RULES FOR CLASSIFICATION Ships Edition October 2015
Part 6 Additional class notations Chapter 6 Cold climate
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DNV GL AS FOREWORD
DNV GL rules for classification contain procedural and technical requirements related to obtaining and retaining a class certificate. The rules represent all requirements adopted by the Society as basis for classification.
© DNV GL AS October 2015
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In this provision "DNV GL" shall mean DNV GL AS, its direct and indirect owners as well as all its affiliates, subsidiaries, directors, officers, employees, agents and any other acting on behalf of DNV GL. CHANGES – CURRENT t n e r
This is a new document. r u
The rules enter into force 1 January 2016. c
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s e g n a h C
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r e t p a h C
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DNV GL AS s t
CONTENTS n e t n
Changes – current...... 3 o C
Section 1 Basic ice strengthening - Ice...... 10 6
1 General...... 10 r
1.1 Introduction...... 10 e t
1.2 Scope...... 10 p a
1.3 Application...... 10 h
1.4 Class notations...... 10 C
1.5 Definitions...... 11 6
t
2 Documentation...... 11 r 2.1 Documentation requirements...... 11 a P 3 Marking and onboard documentation...... 11 3.1 General...... 11 4 Materials...... 12 4.1 General...... 12 5 Loading conditions...... 13 6 Structural requirements for the class notation Ice(C)...... 13 6.1 General...... 13 6.2 Plating...... 13 6.3 Framing...... 13 6.4 Stringers and web frames...... 13 6.5 Weld connections...... 13 6.6 Rudder and steering arrangement...... 14 6.7 Stem...... 14 7 Machinery requirements for class notation Ice(C)...... 14 7.1 Output of propulsion machinery...... 14 7.2 Design of propeller and propeller shaft...... 14 7.3 Sea suctions and discharges...... 18 8 Structural requirements for class notation Ice(E)...... 18 8.1 General...... 18 8.2 Plating...... 19 8.3 Frames...... 19 8.4 Stem...... 19 9 Machinery requirements for class notation Ice(E)...... 19 9.1 Propellers...... 19
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DNV GL AS 9.2 Propeller shafts, intermediate shafts, thrust shafts...... 21 s 9.3 Shrunk joints...... 22 t n
9.4 Gears...... 23 e t
9.5 Sea chests and discharge valves...... 23 n o 9.6 Steering gear...... 23 C
9.7 Electric propeller drive...... 23 6
Section 2 Ice strengthening for the Northern Baltic - Ice...... 24 r e 1 General...... 24 t p
1.1 Introduction...... 24 a 1.2 Scope...... 24 h C 1.3 Application...... 24 6
1.4 Class notations...... 24 t r
1.5 Definitions...... 25 a
2 Documentation...... 26 P 2.1 Documentation requirements...... 26 3 Marking and onboard documentation...... 27 3.1 General...... 27 4 Assumptions...... 27 4.1 General...... 27 5 Materials...... 29 5.1 General...... 29 6 Loading conditions...... 29 7 Design loads...... 29 7.1 Height of the ice load area...... 29 7.2 Ice pressure...... 29 8 Shell plating...... 31 8.1 Vertical extension of ice strengthening for plating...... 31 8.2 Plate thickness in the ice belt...... 32 9 Frames...... 33 9.1 Vertical extension of ice framing...... 33 9.2 Transverse frames...... 33 9.3 Longitudinal frames...... 35 9.4 Structural details...... 36 10 Ice stringers...... 37 10.1 Stringers within the ice belt...... 37 10.2 Stringers outside the ice belt...... 37 10.3 Deck strips...... 38 11 Web frames...... 38
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DNV GL AS 11.1 Design ice load...... 38 s 11.2 Section modulus and shear area...... 38 t n
12 Bilge keels...... 39 e t
12.1 Arrangement...... 39 n o 13 Special arrangement and strengthening forward...... 40 C
13.1 Stem, Baltic ice strengthening...... 40 6
13.2 Arrangements for towing...... 41 r
14 Special arrangement and strengthening aft...... 41 e t
14.1 Stern...... 41 p 14.2 Rudder and steering arrangements...... 41 a h
15 Propulsion machinery...... 42 C
15.1 Engine output...... 42 6
t
15.2 Materials...... 46 r
15.3 Design loads for propeller and shafting...... 47 a P 15.4 Design loads...... 51 15.5 Design loads on propeller blades...... 51 15.6 Axial design loads for open and ducted propellers...... 58 15.7 Torsional design loads...... 59 15.8 Blade failure load...... 62 15.9 Design principle...... 63 15.10 Propeller blade design...... 63 15.11 Propeller bossing and CP mechanism...... 67 15.12 Propulsion shaft line...... 67 15.13 Design of shaft line components not specifically mentioned in FSICR...... 67 15.14 Azimuth main propulsors and other thrusters...... 68 15.15 Alternative design...... 69 16 Miscellaneous machinery requirements...... 69 16.1 Starting arrangements...... 69 16.2 Sea inlet and cooling water systems...... 69 16.3 Ballast system...... 70 17 Guidelines for strength analysis of the propeller blade using finite element method...... 70
Section 3 Operations in cold climate - Winterized...... 71 1 General...... 71 1.1 Introduction...... 71 1.2 Scope...... 71 1.3 Application...... 71 1.4 Class notations...... 71
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DNV GL AS 1.5 Definitions...... 73 s 2 Documentation...... 74 t n
2.1 Documentation requirements...... 74 e t
3 Certification...... 77 n o 3.1 Certification requirements...... 77 C
4 Design environmental conditions...... 77 6
4.1 General...... 77 r
5 General requirements...... 78 e t
5.1 Anti-icing and anti-freezing measures...... 78 p 5.2 De-icing measures...... 79 a h
6 Requirements to winterization...... 80 C
6.1 Requirements to winterization...... 80 6
t r
Section 4 Design ambient temperature - DAT...... 111 a
1 General...... 111 P 1.1 Introduction...... 111 1.2 Scope...... 111 1.3 Application...... 111 1.4 Class notations...... 111 1.5 Documentation requirements...... 112 1.6 Definitions...... 112 2 Material selection...... 114 2.1 Structural categories...... 114 2.2 Selection of steel grades...... 116
Section 5 Polar class - PC...... 118 1 General...... 118 1.1 Introduction...... 118 1.2 Scope...... 118 1.3 Application...... 118 1.4 Class notations...... 118 2 Documentation...... 119 2.1 Documentation requirements...... 119 3 Design principles...... 120 3.1 Design temperature for structure and equipment...... 120 3.2 Hull areas...... 121 3.3 System design...... 121 4 Design ice loads – hull...... 122 4.1 General...... 122
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DNV GL AS 4.2 Glancing impact load characteristics...... 123 s 4.3 Bow area...... 124 t n
4.4 Hull areas other than the bow...... 126 e t
4.5 Design load patch...... 126 n o 4.6 Pressure within the design load patch...... 127 C
4.7 Hull area factors...... 127 6
4.8 Ice compression load amidships...... 129 r
5 Local strength requirements...... 130 e t
5.1 Shell plate requirements...... 130 p 5.2 Framing general...... 131 a h
5.3 Framing – transversely framed side structures and bottom structures...... 133 C
5.4 Framing – side longitudinals (longitudinally framed ships)...... 135 6
t
5.5 Framing – web frame and load carrying stringers...... 136 r
5.6 Framing – structural stability...... 138 a P 5.7 Plated structures...... 140 5.8 Stem and stern frames...... 140 5.9 End connections for framing members...... 141 6 Longitudinal strength...... 143 6.1 Application...... 143 6.2 Design vertical ice force at the bow...... 143 6.3 Design vertical shear force...... 144 6.4 Design vertical ice bending moment...... 145 6.5 Longitudinal strength criteria...... 146 7 Appendages...... 146 7.1 General...... 146 7.2 Rudders...... 146 7.3 Ice forces on rudder...... 147 7.4 Rudder scantlings...... 148 7.5 Ice loads on propeller nozzles...... 148 7.6 Propeller nozzle scantlings...... 148 7.7 Podded propulsors and azimuth thrusters...... 149 8 Direct calculations...... 149 8.1 General...... 149 9 Welding...... 150 9.1 General...... 150 9.2 Minimum weld requirements...... 150 10 Materials and corrosion protection...... 150 10.1 Corrosion/abrasion additions and steel renewal...... 150 10.2 Hull materials...... 151
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DNV GL AS 10.3 Materials for machinery components exposed to sea water...... 153 s 10.4 Materials for machinery components exposed to sea water temperatures. 153 t n
10.5 Materials for machinery components exposed to low air temperature...... 153 e t
11 Ice interaction loads – machinery...... 153 n o 11.1 Propeller ice interaction...... 153 C
11.2 Ice class factors...... 154 6
11.3 Design ice loads for open propeller...... 154 r
11.4 Design ice loads for ducted propeller...... 158 e t
11.5 Propeller blade loads and stresses for fatigue analysis...... 162 p 11.6 Design ice loads for propulsion line...... 162 a h
11.7 Machinery fastening loading conditions...... 166 C
12 Design – machinery...... 168 6
t
12.1 Design principles...... 168 r
12.2 Propeller blade design...... 170 a P 12.3 Fatigue design of propeller blades...... 170 12.4 Blade flange, bolts and propeller hub and CP Mechanism...... 171 12.5 Propulsion line components...... 173 12.6 Azimuth main propulsion...... 179 12.7 Steering system...... 180 12.8 Prime movers...... 180 12.9 Auxiliary systems...... 181 12.10 Sea inlets, cooling water systems and ballast tanks...... 181 12.11 Ballast tanks...... 181 12.12 Ventilation systems...... 181 12.13 Alternative design...... 182 13 Stability and watertight integrity...... 182 13.1 General...... 182 13.2 Intact stability...... 182 13.3 Requirements to watertight integrity...... 182
Appendix A Guidelines for strength analysis of the propeller blade using finite element method...... 183 1 Guidelines for strength analysis of the propeller blade using finite element method...... 183 1.1 Requirements for FE model...... 183 1.2 Good engineering practice for FE analysis...... 183 1.3 Boundary conditions...... 184 1.4 Applied pressure loads...... 184
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DNV GL AS SECTION 1 BASIC ICE STRENGTHENING - ICE 1
n o
1 General i t c 1.1 Introduction e S
The additional class notation Ice establishes requirements for ships intended for service in waters with light 6 ice conditions and light localised drift ice, in river mouths and coastal areas. r e t
1.2 Scope p a The scope for additional class notation Ice specifies requirements for hull strength, machinery systems and h equipment, and includes the relevant procedural requirements applicable to ships operating in light ice and C light localised drift ice conditions in river mouths and coastal areas. 6
t 1.3 Application r a
The additional class notation Ice applies to ships built in compliance with the requirements as specified in P Table 1 and may be assigned a qualifier related to structural strength and machinery. Ships navigating in waters with light ice conditions may be assigned the class notation Ice(C), and ships navigating in waters with light localised drift ice conditions may be assigned the class notation Ice(E). The requirements for class notation Ice(E) are intended for light localised drift ice in mouths of river and coastal areas.
1.4 Class notations Ships built in compliance with the requirements as specified in Table 1 will be assigned the additional notation related to structural strength and integrity as follows:
Table 1 Additional class notation related to cold climate
Class Notation Qualifier Purpose Application
Ice C Ships intended for navigation in light ice conditions Mandatory: E Ships intended for navigation No in light localised drift ice
Design requirements: [6] to [9]
FiS requirements: Pt.7 Ch.1 Sec.2, Pt.7 Ch.1 Sec.3 and Pt.7 Ch.1 Sec.4
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DNV GL AS 1 1.5 Definitions n o
Table 2 Definitions i t c
Terms Definition e S
the upper ice water line is the envelope of the highest points of the waterline at which the ship is intended to operate
(UIWL) in ice irrespective of water salinity. The line may be a broken line. 6
r
the lower ice water line is the envelope of the lowest points of the waterline at which the ship is intended to operate e
(LIWL) in ice. The line may be a broken line. t p a
1.5.1 Symbols h
For symbols not defined in this section, refer to Pt.3 Ch.1 Sec.4. C s1 = Stiffener spacing measured along the plating between ordinary and/or intermediate stiffeners, in m. 6
t r
2 Documentation a P
2.1 Documentation requirements Details related to design, arrangement and strength are in general to be included in the plans specified for the main class.
3 Marking and onboard documentation
3.1 General
3.1.1 The maximum and minimum ice class draughts fore, amidships and aft shall be indicated in the “appendix to the classification certificate”.
3.1.2 If the “Summer Load Line” in fresh water is anywhere located at a higher level than the UIWL, the ship sides shall be provided with a warning triangle and with ice class draught marks at the maximum permissible amidships draught, see Figure 1, and the maximum permissible draught amidships shall be explicitly indicated in the “appendix to the classification certificate”.
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DNV GL AS 1
n o i
ICE t c e S
6
r e t
ICE p a h C
6
t r a P
Figure 1 Ice class draught marking
3.1.3 Marking requirements 1) The ice class draught marking “ICE” shall indicate the maximum ice class draught. 2) The upper edge of the warning triangle shall be located vertically above the “ICE” mark, at the height 1000 mm above Summer Fresh Water Load Line, but not higher than the deck line. The sides of the triangle shall be 300 mm in length. 3) The ice class draught mark shall be located 540 mm abaft the centre of the load line ring or 540 mm abaft the vertical line of the timber load line mark, if applicable. 4) The ice marks and letters shall be cut out of 5 to 8 mm plate and then welded to the ship's side or marking shall be indicated by weld seam directly on the ship side. The marks and letters shall be painted in a red or yellow reflecting colour in order to make the marks and figures plainly visible even in ice conditions. 5) The dimensions of all letters shall be the same as those used in the load line mark. 6) For ships not having load line markings, the warning triangle and ice draught mark shall be vertically aligned with the draught mark. The warning triangle shall be placed 1000 mm above the draught mark, but in no case above the deck line.
4 Materials
4.1 General
4.1.1 For minimum material grade for ice strengthening ships, reference is made to Pt.3 Ch.3 Sec.1 Table 7. Shell strakes in way of ice strengthening area for plates shall be minimum grade B/AH.
4.1.2 The use of materials other than those specified in Pt.3 Ch.3 Sec.1 shall be agreed with the Society.
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DNV GL AS 1 5 Loading conditions n
All design loading conditions in ice, including trim, shall be within the draught envelope limited by the UIWL o i and LIWL. The lower ice waterline should further be determined with due regard to the ship's ice-going t capability in the ballast loading conditions, e.g. propeller submergence. See also Sec.2 [7]. c e (IACS UR I 1.3) S
6
6 Structural requirements for the class notation Ice(C) r e t
6.1 General p a h 6.1.1 The requirements for the bow ice belt region, as defined in Sec.2 Figure 2, for sub-section elements C
[6.2] to [6.7], shall be in accordance with Sec.2 as follows: 6
— In Sec.2 Table 5, the value of ho and h shall be as given for Ice(1C). t
— The ice pressure shall be determined in accordance with Sec.2 [7.2], where the factor c1, as given in r Sec.2 Table 7, is taken as being equal to 0.55. a P — Vertical extension of the ice belt plating and framing shall be: Plating: 0.4 m above UIWL and 0.5 m below LIWL Framing: 0.62 m above UIWL and 1.0 m below LIWL.
6.2 Plating
6.2.1 In the bow ice belt region as defined in [6.1.1], the shell plate thickness shall be as given in Sec.2 [8].
6.3 Framing
6.3.1 In the bow ice belt region as defined in [6.1.1], the frames shall be as given in Sec.2 [9.1] to Sec.2 [9.3]. In addition, the following shall apply: 1) Frames shall be effectively attached to all supporting structures. Transverse and longitudinal frames crossing support structures shall be connected to these with lugs. Alternatively, top stiffener in combination with lug may be used. The upper end of intermediate frames may be sniped at a stringer or deck provided the ice belt covers not more than 1/3 of the span. 2) Frames where the angle between the web and the shell is less than 75 degrees shall be supported against tripping by brackets, intercostals, stringers or similar at a distance preferably not exceeding 2.5 m. Transverse frames perpendicular to shell which are of unsymmetrical profiles shall have tripping preventions if the span is exceeding 4.0 m. 3) The web thickness of the frames shall be at least one half of the thickness of the shell plating. Where there is a deck, tank top, bulkhead, web frame or stringer in lieu of a frame, at least one half of the thickness of shell plating shall be kept to a depth of not less than 0.0025 L, minimum 0.2 m.
6.4 Stringers and web frames
6.4.1 Stringers situated inside and outside the ice belt shall be as given in Sec.2 [10.1] to Sec.2 [10.2]. Web frames shall be as given in Sec.2 [11].
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DNV GL AS 6.5 Weld connections 1
6.5.1 Weld connections to shell in fore peak shall be double continuous. n o i t c
6.6 Rudder and steering arrangement e S
6.6.1 The rudder and steering arrangement shall comply with Sec.2 [14.2], given that the maximum service 6
speed of the ship is not taken less than 14 knots. r e 6.7 Stem t p a
6.7.1 The plate thickness of a shaped plate stem and any part of the bow which forms an angle of 60 h
degrees or more to the centreline in a horizontal plane shall comply with Sec.2 [13.1.2] up to 600 mm above C UIWL. 6
t 7 Machinery requirements for class notation Ice(C) r a P 7.1 Output of propulsion machinery
7.1.1 The maximum continuous output, in kW, is generally not to be less than: ps = 0.73 L B For ships with a bow specially designed for navigation in ice, a reduced output may be accepted. In any case, the output, in kW, shall not be less than: ps = 0.59 L B
7.1.2 If the ship is fitted with a controllable pitch propeller, the output may be reduced by 25%.
7.2 Design of propeller and propeller shaft
7.2.1 The formula for scantlings is based on the following loads:
To = Mean torque of propulsion engine at maximum continuous rating in Nm.
If multi-engine plant, To is the mean torque in an actual branch or after a common point. To is always referred to engine r.p.m.
Tho = Mean propeller thrust in N at maximum continuous speed. R = As given in [7.2.2]. Tice = Ice torque in Nm, referred to propeller r.p.m. = 35 200 R2 for open propellers = 35 200 R2 (0.9 − 0.0622 R-0.5) for ducted propellers.
Skewed propellers will be especially considered with respect to the risk of blade bending at outer radii if fsk exceeds 1.15 (see [7.2.4]).
7.2.2 The particulars governing the requirements for propeller scantlings are:
R = Propeller radius in m. Hr = Pitch in m at radius in question.
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DNV GL AS θ = Rake in degrees at blade tip (backward rake positive). 1
Z = Number of blades. t = Blade gross thickness, in mm, at cylindrical section considered: n o i
t0.25 = t at 0.25 R t t0.35 = t at 0.35 R c e t0.6 = t at 0.6 R S cr = Blade width, in m, at cylindrical section considered: 6
c0.25 = cr at 0.25 R r = cr at 0.35 R e c0.35 t
c0.6 = cr at 0.6 R p e = Distance between skew line and generatrix, in m, at cylindrical section considered, positive when a skew line is forward of generatrix: h C
e0.6 = e at 0.6 R 6 = e at 1.0 R e1.0 t u = Gear ratio: r a u = 1, if the shafting system is directly coupled to engine. P no = Propeller speed at maximum continuous output, for which the machinery shall be approved, in revolutions per minute.
7.2.3 Propellers and propeller parts (defined in Pt.4 Ch.5 Sec.1 [1.3]) shall be of steel or bronze as specified in Pt.2 Ch.2. Nodular cast iron of grade VL 1 and VL 2 may be used for relevant parts in CP-mechanism. Other type of nodular cast iron with elongation ≥ 12% may be accepted upon special consideration for same purposes.
7.2.4 The blade gross thickness, in mm, of the cylindrical sections at 0.25 R (fixed pitch propellers only) and at 0.35 R shall not be less than:
The gross thickness, in mm, at 0.6 R shall not be less than:
where:
U1 and U2 = Material constants shall be taken as given in Pt.4 Ch.5 Sec.1 Table 2.
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DNV GL AS 1
n o i t c e S
6
For fixed blade propellers: r e t p a h C
6
For controllable pitch propellers: t r
K4 = kiZTice sinα a C C C C = As given in Table 3. P 1, 2, 3, 4 2 3 A = q0 + q1d + q2d + q3d q0, q1, q2, q3 = As given in Table 4. d = d = ki = 96 at 0.25 R = 92 at 0.35 R KMat = 1.0 for stainless steel propellers = 0.8 for other materials sinα =
=
K1 as given above is only valid for propulsion by diesel engines (by about zero speed, it is assumed 85% thrust and 75% torque for fixed pitch propellers and 125% thrust and 100% torque for controllable pitch propellers).
For turbine, diesel-electric or similar propulsion machinery K1 will be considered in each particular case.
Guidance note:
K1 may be calculated for other than diesel driven propellers by replacing the constants 0.85 by 1.1 and 0.75 by 1.0 for FP provided that maximum torque of the driving engine is limited to 100% of the nominal torque. If driving torque exceeds 100%, the torque
constant 1.0 shall be multiplied by the ratio Tmax/To and corresponding thrust value (Thotimes constant) calculated based on the actual maximum torque.
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DNV GL AS The thickness of other sections is governed by a smooth curve connecting the above section thicknesses. 1
Table 3 Values of C1, C2, C3, C4 n o i
r 0.25 R 0.35 R 0.6 R t c e C1 0.278 0.258 0.150 S
C2 0.026 0.025 0.020 6 C 0.055 0.049 0.034 3 r e
C4 1.38 1.48 1.69 t p
Table 4 Values of q0, q1, q2, q3 a h C
R q0 q1 q2 q3 6
A1 8.30 0.370 -0.340 0.030 0.25 R t A2 63.80 -4.500 -0.640 0.0845 r a
A1 9.55 -0.015 -0.339 0.0322 P 0.35 R A2 57.30 -7.470 -0.069 0.0472
A1 14.60 -1.720 -0.103 0.0203 0.6 R A2 52.90 -10.300 0.667 0.0
7.2.5 If found necessary by the torsional vibration calculations, minor deviations from the dimensions given in [7.2.4] may be approved upon special consideration.
7.2.6 The gross section modulus of the blade bolt connection, in cm3, referred to an axis tangentially to the bolt pitch diameter, shall not be less than:
σ = Tensile strength of propeller blade material in N/mm2. b 2 σy = Yield stress of bolt material in N/mm .
The propeller blade foot shall have a strength (including stress concentration) not less than that of the bolts.
7.2.7 Fitting of the propeller to the shaft is given in Pt.4 Ch.4 Sec.1 as follows: — flanged connection in [6.3] — keyless cone connection in [6.4] — keyed cone connection in [6.5]. Considering 0°C seawater temperature. If the propeller is bolted to the propeller shaft, the bolt connection shall have at least the same bending strength as the propeller shaft. The strength of the propeller shaft flange (including stress concentration) shall be at least the same as the strength of the bolts.
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DNV GL AS 7.2.8 The propeller shaft diameter need not exceed 1.05 times the rule diameter given for main class, 1 irrespective of the dimension required below. n
The diameter of the propeller shaft at the aft bearing, in mm, shall not be less than: o i t
c e S
6
r e
t 2 σ = Tensile strength of propeller blade material in N/mm . p b 2 σy = Yield strength of propeller shaft material in N/mm . a c0.35 = As defined in [7.2.2] h = As defined in [7.2.2]. C t0.35 6
Between the aft and second aft bearing, the shaft may be evenly tapered to 1.22 times the diameter of the t intermediate shaft, as required for the main class. r a
Forward of the after peak bulkhead, the shaft may be evenly tapered down to 1.05 times the rule diameter of P intermediate shaft, but not less than the actual diameter of the intermediate shaft.
7.3 Sea suctions and discharges
7.3.1 The sea cooling water inlet and discharge for main and auxiliary engines shall be so arranged so that blockage of strums and strainers by ice is prevented. In addition to requirements in Pt.4 Ch.1 and Pt.6 - Additional class notations the requirements in [7.3.2] and [7.3.3] shall be complied with.
7.3.2 One of the sea cooling water inlet sea chests shall be situated near the centre line of the ship and well aft. At least one of the sea chests shall be sufficiently high to allow ice to accumulate above the pump suctions.
7.3.3 A full capacity discharge branched off from the cooling water overboard discharge line shall be connected to at least one of the sea inlet chests. At least one of the fire pumps shall be connected to this sea chest or to another sea chest with de-icing arrangements. Guidance note: Heating coils may be installed in the upper part of the sea chest(s). Arrangement using ballast water for cooling purposes is recommended but will not be accepted as a substitute for sea inlet chest arrangement as described above.
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8 Structural requirements for class notation Ice(E)
8.1 General
8.1.1 The requirements for the bow ice belt region, as defined in Sec.2 Figure 2, for sub-section elements [8.2] to [8.4], shall be in accordance with Sec.2 as follows:
— In Sec.2 Table 5, the value of ho and h shall be as given for Ice(1C). — The ice pressure shall be determined in accordance with Sec.2 [7.2], where:
— For determination of k, the machinery output PS need not be taken > 750 kW.
— The factor c1, as given in Sec.2 Table 7, is taken as being equal to 0.30.
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DNV GL AS — Vertical extension of the ice belt plating and framing shall be: 1
Plating: 0.4 m above UIWL and 0.5 m below LIWL Framing: 0.62 m above UIWL and 1.0 m below LIWL. n o i t c
8.2 Plating e S 8.2.1 In the bow ice belt region as defined in [8.1.1], the shell plate thickness shall be as given in Sec.2 [8]. 6
r e
8.3 Frames t p
8.3.1 In the bow ice belt region as defined in [8.1.1], the frames shall be as given in Sec.2 [9.1] to Sec.2 a
[9.3]. h C 8.3.2 In the bow ice belt region tripping brackets shall be fitted as given in [6.3]. 6
t r
8.4 Stem a P 8.4.1 The plate thickness of a shaped plate stem and any part of the bow which forms an angle of 60 degrees or more to the centreline in a horizontal plane shall comply with Sec.2 [13.1.2] up to 600 mm above UIWL.
9 Machinery requirements for class notation Ice(E)
9.1 Propellers
9.1.1 General The propellers of ships with ice class Ice(E) must be made of the cast copper alloys or cast steel alloys specified in Pt.4 Ch.5 Sec.1 [2.1].
9.1.2 Strengthening Blade sections: tE = = Increased gross thickness of blade section in mm. t = Blade section gross thickness fulfilling Pt.4 Ch.5 Sec.1 [2.2].
If then
If then
CEP = Ice class strengthening factor:
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DNV GL AS 1 = n o i f = 0.62 for solid propellers t = 0.72 for controllable pitch propellers c e
In the case of ducted propellers, the values of f may be reduced by 15% S z = Number of blades. 6 pW = Main engine power in kW. n2 = Propeller shaft speed in rpm. r e
CDyn = Dynamic factor: t p a
, for , otherwise 1.0. h C
6
σ /σ = The maximum and mean stress, generally to be taken from a detailed FE calculation.
max m t
If, in exceptional cases, no such calculation exists, the stress ratio may be calculated r
approximately according to the following formula: a
P
ET =
f2 = 0.4 - 0.6 for single-screw ships, the lower value has to be chosen for stern shapes with a big propeller tip clearance and no rudder heel, the larger value to sterns with small clearance and with rudder heel. Intermediate values are to be selected accordingly. VS = Ship speed in kn. w = Mean wake fraction. T = Propeller thrust in N.
Blade tips:
t1.0E =
= Increased gross thickness of blade section in mm. t1.0E = Strengthened blade tip in mm. D = Propeller diameter in mm. CW = Material factor, corresponds to σB Table 2 in Pt.4 Ch.5 Sec.1 [2.1].
In the case of ducted propellers, the thickness of blade tips may be reduced by 15%.
Leading and trailing edges:
The gross thickness of the leading and trailing edges of reversible propellers and the thickness of the leading edge of controllable pitch propellers must be equal for ice class ICE-E to at least 35% of the blade tip t1.0E when measured at a distance of 1.25 · t1.0E from the edge of the blade. For ducted propellers, the
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DNV GL AS strengthening at the leading and trailing edges has to be based on the non-reduced tip gross thickness 1 according to formula for t1.0E above. n
Blade wear: o i t
If the actual gross thickness in service is below 50% at the blade tip or 90% at other radii of the values c obtained from [9.1.2], respective counter measures have to be taken. Ice strengthening factors according to e S
[9.1.2] will not be influenced by an additional allowance for abrasion. 6
Guidance note: r If the propeller is subjected to substantial wear, e.g. abrasion in tidal flats or in case of dredgers, a wear allowance should be added e
to the blade thickness determined in order to achieve an adequate service time with respect to blade wear. t p
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Propeller mounting: C
6
Where the propeller is mounted on the propeller shaft by the oil injection method, the necessary contact 2 pressure PE, in N/mm , in the area of the mean taper diameter is to be determined as in [9.3]. t r a
In the case of flanged propellers, the required diameter dsE of the alignment pin is to be determined by P applying the following formula:
where: dsE = Reinforced root diameter of alignment pin in mm. ds = Diameter of alignment pin for attaching the propeller, in mm, in accordance with Pt.4 Ch.4 Sec.1 [2.3.4]. CEW = Ice class reinforcement factor in accordance with formula [9.2.2].
9.2 Propeller shafts, intermediate shafts, thrust shafts
9.2.1 General The necessary propeller shaft reinforcements in accordance with formula given in [9.2.2], in conjunction with the formulae and factors specified in Pt.4 Ch.4 Sec.1 [2.2], apply to the area of the aft stern tube bearing or shaft bracket bearing as far as the forward load-bearing edge of the propeller or of the aft propeller shaft coupling flange subject to a minimum area of 2.5 · d.
9.2.2 Reinforcements
where: dE = Increased diameter of propeller shaft in mm. d = Shaft diameter, in mm, according to Pt.4 Ch.4 Sec.1 [2.2]. CEW = Ice class reinforcement factor:
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DNV GL AS 1
= n o i t pW, = See [9.1.2]. c n2 e c = 0.7 for shrink fits in gears. S = 0.71 for the propeller shafts of fixed-pitch propellers. 6
= 0.78 for the propeller shafts of controllable pitch propellers. r e
In case of ducted propellers, the values of c can be reduced by 10%. t p a
9.3 Shrunk joints h C 9.3.1 Normal operation 6 When designing shrink fits in the shafting system and in gearboxes, the necessary pressure per unit area PE, 2 t in N/mm , is to be calculated in accordance with the following formula: r a
P
where: f =
A = Effective area of a shrink fit, in mm2. CA = Coefficient for shrink joints: = 1.0 for geared diesel engine and turbine plants as well as for electric motor drives. = 1.2 for diesel engine drives. ce = Ice strengthening factor: = C = Conicity of shaft ends: = difference in diameter/length of taper Q = Peripheral force at mean taper diameter, in N. S = Safety margin against propeller slipping on cone ≥ 2.8. θ = Half-conicity =
T has to be introduced as positive value if the propeller thrust increases the surface pressure at the taper. Change of direction of the axial force shall be neglected as far as performance and thrust are essentially less. T has to be introduced as negative value if the axial force reduces the surface pressure at the taper, e.g. for tractor propellers.
9.3.2 Operation at a resonance For direct coupled propulsion plants with a barred speed range it has to be confirmed by separate calculation that the vibratory torque in the main resonance is transmitted safety. For this proof the safety against
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DNV GL AS slipping for the transmission of torque shall be at least S = 2.0, the coefficient cA may be set to 1.0. For this 1 additional proof the respective influence of the thrust shall be disregarded. n CEW to be calculated according to [9.2.2], the higher value of the connected shaft ends has to be taken for o the coupling i t c e
9.4 Gears S
Gears in the main propulsion plant of ships with ice class Ice(E) shall not be strengthened. 6
r e
9.5 Sea chests and discharge valves t p
Sea chests and discharge valves shall be designed in accordance with Pt.4 Ch.6. a h C 9.6 Steering gear 6 The dimensional design of steering gear components shall take account of the rudder stock diameter t specified in Pt.3 Ch.14 Sec.1 [7]. r a P 9.7 Electric propeller drive For ships with electrical propeller drive see the rules for electrical propulsion Pt.4 Ch.8 Sec.5 and Pt.4 Ch.8 Sec.12.
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DNV GL AS SECTION 2 ICE STRENGTHENING FOR THE NORTHERN BALTIC - ICE 2
n o
1 General i t c 1.1 Introduction e S
The additional class notation Ice establishes requirements for ships intended for service in the northern 6
Baltic in winter or areas with similar ice conditions. r e t
1.2 Scope p a The scope for additional class notation Ice specifies requirements for hull strength, machinery systems and h equipment and the relevant procedural requirements applicable to ships operating in northern Baltic ice C conditions. A series of qualifiers is available for this notation; related to ships intended for navigation in ice- infested waters, in varying degrees of ice thickness. High powered ships employed as regular traffic, in heavy 6
Baltic ice, may be assigned a specific qualifier associated with their trade. t r a 1.3 Application P The additional class notation Ice applies to ships built in compliance with the requirements of this section and may be assigned one of the following class notations: Ice(1A*), Ice(1A), Ice(1B) or Ice(1C). Ships assigned class notation Ice(1A*) may be assigned the class notation Ice(1A*F). The additional ice class Ice(1A*F) is recommended for ships with relatively high engine power designed for regular traffic in the northern Baltic and other relevant areas, normally operating according to rather fixed timetables irrespective of ice conditions and to a certain degree independent of ice breaker assistance.
1.4 Class notations Ships built in compliance with the requirements as specified in Table 1 will be assigned the additional notation as follows:
Table 1 Additional class notation related to cold climate
Class Notation Qualifier Purpose Application
Ice High powered ships for Ships constructed according to Baltic ice rules. 1A*F regular traffic in heavy Baltic Ice thickness 1.0 m. ice. Mandatory: Ships intended for navigation Constructed according to Baltic ice rules. Ice No 1A* in ice-infested waters. thickness 1.0 m.
Ships intended for navigation Constructed according to Baltic ice rules. Ice Design requirements: 1A in ice-infested waters. thickness 0.8 m. [6] to [16] 1B Ships intended for navigation Constructed according to Baltic ice rules. Ice FiS requirements: in ice-infested waters. thickness 0.6 m. Pt.7 Ch.1 Sec.2, Pt.7 Ch.1 1C Ships intended for navigation Constructed according to Baltic ice rules. Ice Sec.3 and Pt.7 Ch.1 Sec.4 in ice-infested waters. thickness 0.4 m.
1.4.1 The DNV GL ice classes are accepted as equivalent to the Finnish-Swedish ice classes.
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DNV GL AS Table 2 Equivalence between DNV GL Ice class notation and the Finnish-Swedish ice classes 2
Ice class notation Equivalent Finnish-Swedish Ice class n o i
Ice(1A*) 1A Super t c
Ice(1A) 1A e S
Ice(1B) 1B 6
Ice(1C) 1C r e t p
1.5 Definitions a h
1.5.1 General definitions C
6
Table 3 Definitions t r
Terms Definition a P is determined from the Upper Ice Water Line (UIWL) to the Lower Ice Water Line (LIWL), which defines the extreme draughts. For operation in Baltic, the upper ice extent of ice strengthening waterline (UIWL) is in general the same as the Fresh Water Summer Load Line. See also Sec.1 [1.5].
from the stem to a line parallel to and 0.04 L aft of the forward borderline of the part of the hull where the waterlines run parallel to the centre line. For ice classes bow region Ice(1A*F), Ice(1A*) and Ice(1A) the overlap of the borderline need not exceed 6 m, for ice classes Ice(1B), Ice(1C) and Ice(E) this overlap need not exceed 5 m. See Figure 1.
ice belt regions from the aft boundary of the bow region to a line parallel to and 0.04 L aft of the aft borderline of the part of the hull where the waterlines run parallel to the centre line. midbody region For ice classes Ice(1A*F), Ice(1A*) and Ice(1A) the overlap of the borderline need not exceed 6 m, for ice classes Ice(1B) and Ice(1C) this overlap need not exceed 5 m. See Figure 1.
stern region from the aft boundary of the midbody region to the stern. See Figure 1.
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DNV GL AS 2
n o i t c e S
6
r e t p a h C
6
t
r a
Figure 1 Ice belt regions P
The Upper Ice Water Line (UIWL) and the Lower Ice Water Line (LIWL) are defined in Sec.1 [1.5].
1.5.2 Definition of forward draught during transit in ballast condition The minimum forward draught, in m, shall be at least:
(2 + 0.00025 Δf) ho but need not exceed 4 ho where:
Δf = Displacement of the ship, in tonnes, on the maximum ice class draught according to [1.5.3]. ho = Ice thickness according to Table 6.
1.5.3 Symbols For symbols not defined in this section, refer to Pt.3 Ch.1 Sec.4.
2 Documentation
2.1 Documentation requirements
2.1.1 General For general requirements to documentation, including definition of the Info codes, see Pt.1 Ch.3 Sec.2. For a full definition of the documentation types, see Pt.1 Ch.3 Sec.3. Documentation shall be submitted as required by Table 4.
Table 4 Document requirements
Object Documentation type Additional description Info
Technical Z100 – Specification Displacement, machinery type, propulsion power. FI information
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DNV GL AS Z240 – Calculation Minimum required propulsion power, P ,see[15.1]. FI 2 report min n o Propulsion Applicable if a first blade order torsional resonance is within i t
and steering C040 – Design analysis operational speed range +/- 20%. Torsional vibration analysis of AP c
arrangement ice torque response. e S
Applicable for alternative designs, not applying loads defined in 6
C040 – Design analysis AP the rules. Comprehensive design analysis of entire system. r e
Propeller blades C040 – Design analysis Final element analysis of blade stresses introduced by ice loads. AP t p AP = For approval; FI = For information a h C
3 Marking and onboard documentation 6
t r
3.1 General a P For marking and on board documentation see Sec.1 [3].
4 Assumptions
4.1 General
4.1.1 The method for determining the hull scantlings, engine output and other properties are based on certain assumptions concerning the nature of the ice load on the structure and operation of the ship as described in the Finnish-Swedish Ice Class Rules. These assumptions rest on full scale observations made in the northern Baltic.
Table 5 Operation of the ship - design basis
Ice(1A*) normally capable of navigating in difficult ice conditions without the assistance of icebreakers
Ice(1A) capable of navigating in difficult ice conditions, with the assistance of icebreakers when necessary
Ice(1B) capable of navigating in moderate ice conditions, with the assistance of icebreakers when necessary
Ice(1C) capable of navigating in light ice conditions, with the assistance of icebreakers when necessary
Guidance note: For background documentation of this section, reference is made to Finnish Transport Safety Agency (TraFi) homepage: http:// www.trafi.fi/en/maritime/ice_classes_of_ships : “Finnish-Swedish Ice Class Rules” “Guidelines for the application of the Finnish-Swedish ice class rules” (hereafter called “TraFi Guidelines”)
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4.1.2 Assistance from icebreakers is normally assumed when navigating in ice bound waters.
4.1.3 The formula given for plating, stiffeners and girders is based on special investigations as to the distribution of ice loads from plating to stiffeners and girders as well as redistribution of loads on stiffeners and girders. Special values have been given for distribution factors and certain assumptions have been made regarding boundary conditions.
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DNV GL AS 4.1.4 For the formulae and values given in this section for the determination of the hull scantlings more 2 sophisticated methods may be substituted subject to special approval. However, direct analysis is not to be utilized as an alternative to the analytical procedures prescribed by explicit requirements in [8], [9] and [10] n o
(plates, frames and stringers), unless these are invalid or inapplicable for a given structural arrangement or i detail. t c
Direct analyses shall be carried out using the load patch defined in [7] (P, h and la). The pressure to be used e
is 1.8·P where P is determined according to [7.2.1]. The load patch shall be applied at locations where the S capacity of the structure under the combined effects of bending and shear are minimized. In particular, the 6 structure shall be checked with load centred at the UIWL, 0.5·ho below the LIWL, and positioned several vertical locations in between. Several horizontal locations shall also be checked, especially the locations r e centred at the mid-span or -spacing. Further, if the load length la cannot be determined directly from the t arrangement of the structure, several values of la shall be checked using corresponding values for ca. p a
Acceptance criteria for designs are that the combined stresses from bending and shear, using the von Mises h
yield criterion, are lower than the yield point ReH. If the structure is analysed by the use of beam models, the C allowable bending and shear stress is not to be larger than 0.9·ReH and 0.9·τeH respectively, where τeH = ReH/ 6
√3. t r
4.1.5 If scantlings derived from these regulations are less than those required for a non-ice-strengthened a ship, the latter shall be used. P
4.1.6 The frame spacings and spans defined in the following text are in general to be as given in Pt.3 Ch.3 Sec.6 and normally assumed to be measured along the plate and perpendicular to the axis of the stiffener for plates, along the flange for members with a flange, and along the free edge for flat bar stiffeners. For curved members the span (or spacing) is defined as the chord length between span (or spacing) points. The span points are defined by the intersection between the flange or upper edge of the member and the supporting structural element (stringer, web frame, deck or bulkhead). Figure 2 illustrates the determination of span and spacing for curved members.
l b
Figure 2 Definition of the frame span (left) and frame spacing (right) for curved members.
4.1.7 The effective breadth of the attached plate to be used for calculating the combined section modulus of the stiffener, stringer and web frame and attached plate shall be taken as given in Pt.3 Ch.3 Sec.6 [1.3].
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DNV GL AS 4.1.8 The requirements for the section modulus and shear area of the frames, stringers and web frames in 2
[9], [10] and [11] with respect to the effective member cross section, where the member is not normal to the plating, the section properties shall be calculated in accordance with Pt.3 Ch.3 Sec.6 [1.4]. n o i t
5 Materials c e S
5.1 General 6
For minimum material grade for ice strengthening ships see Sec.1 [4]. r e t p
6 Loading conditions a
For design loading conditions in ice see Sec.1 [5]. h C
6
7 Design loads t r a
7.1 Height of the ice load area P
7.1.1 An ice strengthened ship is assumed to operate in open sea conditions corresponding to a level ice thickness not exceeding ho. The design the ice height (h) of the area actually under ice pressure at any particular point of time is, however, assumed to be only a fraction of the ice thickness. The values for ho and h are given in the following table.
Table 6 Values of ho and h
Ice class ho (m) h (m)
Ice(1A*) 1.0 0.35 Ice(1A) 0.8 0.30 Ice(1B) 0.6 0.25 Ice(1C) 0.4 0.22
7.2 Ice pressure
7.2.1 The design ice pressure (based on a nominal ice pressure of 5600 kN/m2), in kN/m2, is determined by the formula:
where: cd = A factor which takes account of the influence of the size and engine output of the ship. This factor is taken as maximum cd = 1. It is calculated by the formula:
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DNV GL AS
2
n o i t
c e S a1 and b1 are given in Table 7. 6
Table 7 Values of a1 and b1 r e t
Region p a Bow Midbody and Stern h
k ≤ 12 k > 12 k ≤ 12 k > 12 C 1 1 1 1 6
a1 30 6 8 2 t r b1 230 518 214 286 a P Δf = Displacement, in tonnes, as defined in [1.5.4]. pS = Machinery output, in kW, as defined in [15.1.1]. c1 = A factor which takes account of the probability that the design ice pressure occurs in a certain region of the hull for the ice class in question.
The value of c1 is given in Table 8:
Table 8 Values of c1
Region Ice class Bow Midbody Stern
Ice(1A*) 1.0 1.0 0.75
Ice(1A) 1.0 0.85 0.65
Ice(1B) 1.0 0.70 0.45
Ice(1C) 1.0 0.50 0.25
For ice class Ice(1A*F) an additional lower bow ice belt (see [8.1.2]) is defined with factor c1 = 0.20. ca = A factor which takes account of the probability that the full length of the area under consideration will be under pressure at the same time. It is calculated by the formula:
, maximum 1.0, minimum 0.35, ℓ0 = 0.6 m
ℓa shall be taken as given in Table 9.
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DNV GL AS Table 9 Values of ℓa 2
n Structure Type of framing ℓa o i
transverse frame spacing t Shell c longitudinal 1.7 × frame spacing e S transverse frame spacing Frames 6
longitudinal span of frame r e
Ice stringer span of stringer t p
Web frame 2 × web frame spacing a h C
8 Shell plating 6
t r
8.1 Vertical extension of ice strengthening for plating a P
8.1.1 The vertical extension of the ice belt (see Figure 1) shall not be less than given in Table 10.
Table 10 Vertical extension of ice belt
Ice class Region Above UIWL (m) Below LIWL (m)
Bow 1.20 Ice(1A*) Midbody 0.60
Stern 1.0
Bow 0.90
Ice(1A) Midbody 0.50 0.75 Stern
Bow 0.70
Ice(1B) and Ice(1C) Midbody 0.40 0.60 Stern
8.1.2 In addition the following areas shall be strengthened: Fore foot: For ice class Ice(1A*) and Ice(1A*F), the shell plating below the ice belt from the stem to a position five main frame spaces abaft the point where the bow profile departs from the keel line shall have at least the thickness required in the ice belt in the midbody region, calculated for the actual frame spacing. Upper bow ice belt: For ice classes Ice(1A*) and Ice(1A) on ships with an open water service speed equal to or exceeding 18 knots, the shell plate from the upper limit of the ice belt to 2 m above it and from the stem to a position at least 0.2 L abaft the forward perpendicular, shall have at least the thickness required in the ice belt in the midbody region, calculated for the actual frame spacing. Guidance note: A similar strengthening of the bow region is advisable also for a ship with a lower service speed, when it is, e.g. on the basis of the model tests, evident that the ship will have a high bow wave.
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DNV GL AS For ice class Ice(1A*F), the upper bow ice belt shall be taken 3 m above the normal ice belt, extending 2 within the bow region.
Lower bow ice belt: For ice class Ice(1A*F), a lower low ice belt below the normal ice belt is defined n o covering the bow region aft of the forefoot and down to the lower turn of bilge. i t c
8.1.3 Sidescuttles shall not be situated in the ice belt. If the weather deck in any part of the ship is situated e below the upper limit of the ice belt, e.g. in way of the well of a raised quarter deck, the bulwark shall be S given at least the same strength as is required for the shell in the ice belt. The strength of the construction of 6
the freeing ports shall meet the same requirements. r e 8.2 Plate thickness in the ice belt t p a
8.2.1 For transverse framing the thickness of the shell plating, in mm, shall be determined by the formula: h
C
6
t r
a P For longitudinal framing the thickness of the shell plating, in mm, shall be determined by the formula:
PPL = 0.75 P P = As given in [7.2]. f1 =
f2 =
= 1.4 − 0.4 (h/s1); when 1 ≤ h/s1 < 1.8 = 0.35 + 0.183 (h/s1) for 1.8 ≤ h/s1 < 3 = 0.9 for h/s1 > 3 h = As given in [7.1]. tc = Increment for abrasion and corrosion in mm; normally 2 mm. If a special surface coating, by experience shown capable to withstand the abrasion of ice, is applied and maintained, lower values may be approved.
8.2.2 For ice class Ice(1A*F) the following additional requirements are given: — bottom plating in the Bow region (below the Lower Bow ice belt defined in [8.1.2]) shall have a gross thickness, in mm, not less than:
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DNV GL AS — side and bottom plating in the Stern region below the ice belt shall have a gross thickness, in mm, not 2
less than:
n o i t c e
S
6
9 Frames r e t p
9.1 Vertical extension of ice framing a h
9.1.1 The vertical extension of the ice strengthening of the framing shall be at least as given in Table 11: C
Table 11 Vertical extension of ice strengthening of the framing 6
t r
Ice class Region Above UIWL (m) Below LIWL (m) a P Bow to double bottom or below top of floors
Ice(1A*F), Ice(1A*) Midbody 1.2 2.0
Stern 1.6
Bow 1.6
Ice(1A), (1B), (1C) midship 1.0 1.3
Stern 1.0
Where an upper Bow ice belt is required (see [8.1.2]), the ice strengthened part of the framing shall be extended at least to the top of this ice belt.
9.1.2 Where the ice strengthening would go beyond a deck or a tank top (or tank bottom) by not more than 250 mm, it can be terminated at that deck or tank top (or tank bottom).
9.2 Transverse frames
9.2.1 The gross section modulus of a main or intermediate transverse frame, in cm3, shall be calculated by the formula:
and the effective gross shear area, in cm2, is calculated from:
P = Ice pressure as given in [7.2]
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DNV GL AS h = Height of load area as given in [7.1] 2
mt = n o i t f3 = Is a factor which takes into account the maximum shear force versus the load location and the c
shear stress distribution, f3 = 1.2. e m = Values as given in Table 12. S
o 6 Table 12 Values of m
o r e t Boundary condition mo Example p
a h C
6
l h 7 Frames in a bulk carrier with top wing tanks t r a P
l h 6 Frames extending from the tank top to a single deck
l
5.7 Continuous frames between several decks or stringers
l
l h 5 Frames extending between two decks only
The boundary conditions are those for the main and intermediate frames. Possible different conditions for main and intermediate frames are assumed to be taken care of by interaction between the frames and may be calculated as mean values. Load is applied at mid span.
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DNV GL AS If the ice belt covers less than half the span of a transverse frame, (b2 < 0.5 ℓ) the following modified 3 2 formula may be used for the gross section modulus in cm :
n o i t c e
S
6 b2 = Distance in m between upper or lower boundary of the ice belt and the nearest deck or stringer within the ice belt. r e t
Where less than 15% of the span, l, of the frame is situated within the ice-strengthening zone for frames as p defined in [9.1.1], ordinary frame scantlings may be used. a h C
9.2.2 Upper end of transverse framing 6
1) The upper end of the strengthened part of a main frame and of an intermediate ice frame shall be
attached to a deck or an ice stringer (see [10]). t r
2) Where an intermediate frame terminates above a deck or an ice stringer which is situated at or above a
the upper limit of the ice belt (see [8.1]), the part above the deck or stringer may have the scantlings P required for a non-ice-strengthened ship and the upper end be connected to the adjacent main frames by a horizontal member of the same scantlings as the main frame.
9.2.3 Lower end of transverse framing 1) The lower end of the strengthened part of a main frame and of an intermediate ice frame shall be attached to a deck, tank top (or tank bottom) or ice stringer (see [10]). 2) Where an intermediate frame terminates below a deck, tank top (or tank bottom) or ice stringer which is situated at or below the lower limit of the ice belt (see [7.1]), the lower end shall be connected to the adjacent main frames by a horizontal member of the same scantlings as the main frames. Note that the main frames below the lower edge of ice belt must be ice strengthened, see [8.1.1].
9.3 Longitudinal frames
9.3.1 The gross section modulus of longitudinal frame with and without brackets, in cm3, shall be calculated by the formula:
The shear effective gross area of a longitudinal frame, in cm2, shall be:
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DNV GL AS In calculating the actual shear area of the frames, the shear area of the brackets is not to be taken into 2 account. n f = Factor which takes account of the load distribution to adjacent frames: o 4 i f4 = (1 − 0.2 h/s1) t c f5 = Factor which takes into account the maximum shear force versus load location and the shear stress distribution: e S f5 = 2.16
P = Ice pressure as given in [7.2] 6
h = Height of load area as given in [7.1] r m1 = Is a boundary condition factor; m1= 13.3 for a continuous beam; where the boundary conditions e deviate significantly from those of a continuous beam, e.g. in an end field, a smaller boundary t p factor may be required. For frames without brackets a value m = 11.0 shall be used. 1 a h C 9.4 Structural details 6
t
9.4.1 Within the ice strengthened area all frames shall be effectively attached to all supporting structures. r
Longitudinal or transverse frames crossing supporting structures, such as web frames or stringers, shall be a connected to these structures on both sides (by collar plates or lugs in way of cut-outs). P Brackets or top stiffeners shall be fitted, in order to provide proper transfer of forces to supporting elements, as necessary. Connection of non-continuous frames to supporting structures shall be made by brackets or similar construction. When a bracket is installed, it shall have at least the same thickness as the web plate of the frame, and the edge shall be appropriately stiffened against buckling.
9.4.2 For ice class Ice(1A*F) and Ice(1A*), and for ice class Ice(1A) in the bow and midbody regions and for ice classes Ice(1B) and Ice(1C) in the bow region, the following shall apply in the ice strengthened area: 1) Frames which are not at a straight angle to the shell shall be supported against tripping by brackets, intercostals, stringers or similar at a distance preferably not exceeding 1.3 m. Transverse frames perpendicular to shell which are of unsymmetrical profiles shall have tripping preventions if the span is exceeding 4.0 m. 2) Frames shall be attached to the shell by double continuous welds. No scalloping is allowed (except when crossing shell plate butts). 3) The web thickness of the frames shall be at least the maximum of the following: — 9 mm — 2.5% of the frame spacing for transverse frames. Alternatively, the buckling capacity of the transverse frame may be assessed by direct calculation. Direct calculations shall be based on design loads as given in [4.1.4] and buckling calculation procedures according to Pt.3 Ch.8. — one half of the net shell plating requirement as given by [8.2.1], where the yield stress, ReH, shall not be taken larger than that given for the frame — , hw is the web height and C = 805 for profiles and C = 282 for flat bars.
Where there is a deck, tank top (or tank bottom) or bulkhead in lieu of a frame, the plate thickness of this shall be as above, to a depth corresponding to the height of adjacent frames.
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DNV GL AS 2 10 Ice stringers n o i 10.1 Stringers within the ice belt t c
3 e
10.1.1 The gross section modulus of a stringer situated within the ice belt (see [8.1]), in cm , shall be S calculated by the formula: 6
r e t p
a h
2 C
The gross shear area, in cm , shall not be less than:
6
t r a P
P = Ice pressure as given in [7.2]. h = Height of load area as given in [7.1]. The product Ph shall not be taken as less than 150 ℓ = Span of stringer in m. m1 = Boundary condition factor as given in [9.3.1]. f6 = Which takes account of the distribution of load to the transverse frames; to be taken as 0.9. f7 = Factor of stringers; to be taken as 1.8. f8 = Factor that takes into account the maximum shear force versus load location and the shear stress distribution; f8 = 1.2.
10.2 Stringers outside the ice belt
10.2.1 The gross section modulus of a stringer situated outside the ice belt but supporting ice strengthened frames, in cm3, shall be calculated by the formula:
The gross shear area, in cm2, shall not be less than:
P = Ice pressure as given in [7.2]. h = Height of load area as given in [7.1].
The product Ph shall not be taken as less than 150.
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DNV GL AS ℓ = Span of stringer in m. 2 m1 = Boundary condition factor as given in [9.3.1].
ℓs = The distance to the adjacent ice stringer in m. n
= The distance to the ice belt in m. o hs i f9 = Factor which takes account of the distribution of load to the transverse frames; to be taken as 0.80. t c f10 = Safety factor of stringers; to be taken as 1.8. e f11 = Factor that takes into account the maximum shear force versus load location and the shear stress S
distribution; f11 = 1.2. 6
r e
10.3 Deck strips t p
10.3.1 Narrow deck strips abreast of hatches and serving as ice stringers shall comply with the section a
modulus and shear area requirements in [10.1] and [10.2] respectively. In the case of very long hatches the h
lower limit of the product Ph may be reduced to 100. C
6
10.3.2 Regard shall be paid to the deflection of the ship's sides due to ice pressure in way of very long hatch t
openings (more than B/2), when designing weather deck hatch covers and their fittings. r a P 11 Web frames
11.1 Design ice load
11.1.1 The design ice load transferred to a web frame from an ice stringer or from longitudinal framing, in kN, shall be calculated by the formula:
P = Ice pressure as given in [7.2], when calculating factor ca, however, ℓa shall be taken as 2 S. h = Height in m of load area as given in [7.1].
The product Ph shall not be taken less than 150.
S = Web frame spacing in m. f12 = Factor of web frames; to be taken as 1.8.
In case the supported stringer is outside the ice belt, the load F may be multiplied by:
as given in [10.2.1].
11.2 Section modulus and shear area
11.2.1 The gross section modulus requirement, in cm3, is given by:
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DNV GL AS 2
n o i t
c M = Maximum calculated bending moment, in kNm, under the ice load F, as given in [11.1.1]. This shall e S
be taken as M = 0.193 · F · ℓ.
γ = As given in Table 13. 6 2
A = Required gross shear area from [11.2.2], in cm . r 2 Aa = Actual gross cross sectional area of web frame, Aa = Af + Aw, in cm . e t
2 p
11.2.2 With boundary conditions as given in [11.2.1], the gross shear area of a web frame, in cm , is given a by: h
C
6
t r
a P Q = Maximum calculated shear force under the load F, in kN, as given in [11.1.1]. f13 = Factor that takes into account the shear force distribution, f13 = 1.1. α = Factor given in Table 13. A = Gross cross sectional area of free flange, in cm2. f 2 Aw = Actual effective gross cross sectional area of web plate, in cm .
Table 13 Values of α and γ
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
α 1.5 1.23 1.16 1.11 1.09 1.07 1.06 1.05 1.05 1.04 1.04
γ 0 0.44 0.62 0.71 0.76 0.80 0.83 0.85 0.87 0.88 0.89
12 Bilge keels
12.1 Arrangement
12.1.1 The connection of bilge keels to the hull shall be so designed that the risk of damage to the hull, in case a bilge keel is ripped off, is minimised.
12.1.2 For class Ice(1A*F) bilge keels are normally to be avoided and should be replaced by roll-damping equipment. Specially strengthened bilge keels may be considered.
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DNV GL AS 2 13 Special arrangement and strengthening forward n o i 13.1 Stem, Baltic ice strengthening t c e
13.1.1 The stem may be made of rolled, cast or forged steel or of shaped steel plates. as shown in Figure 3. S
6
r e t p a h C
6
t r a P
Figure 3 Examples of suitable stems
13.1.2 The plate thickness of a shaped plate stem and in the case of a blunt bow, any part of the shell where α ≥ 30° and ψ ≥ 75° (see [15.1.3] for angle definitions), shall be calculated according to the formulae in [8.2] assuming that: s = Spacing of elements supporting the plate in m. PPL = P (see [7.2]). ℓa = Spacing of vertical supporting elements in m, see Table 9.
For class Ice(1A*F) the front plate and upper part of the bulb and the stem plate up to a point 3.6 m above UIWL (lower part of bow door included) shall have a minimum gross thickness, in mm, of:
c = 2.3 for the stem plate = 1.8 for the bulb plating.
The width of the increased bulb plate shall not be less than 0.2 b on each side of the centre line, b = breadth of the bulb at the forward perpendicular.
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DNV GL AS 13.1.3 The stem and the part of a blunt bow defined above shall be supported by floors or brackets spaced 2 not more than 0.6 m apart and having a thickness of at least half the plate thickness. The reinforcement of the stem shall be extend from the keel to a point 0.75 m above UIWL or, in case an upper bow ice belt is n o
required ([8.1.2]) to the upper limit of this. i t c
13.2 Arrangements for towing e S
13.2.1 The ship shall be arranged for towing. 6
r
13.2.2 A bitt or other means for securing a towline, dimensioned to stand the breaking force of the towline e of the ship shall be fitted. t p a
14 Special arrangement and strengthening aft h C
6
14.1 Stern t r
14.1.1 The introduction of new propulsion arrangements with azimuth thrusters or “podded” propellers, a which provide an improved manoeuvrability, will result in increased ice loading of the Stern region and stern P area. This fact should be considered in the design of the aft/stern structure.
14.1.2 In order to avoid very high loads on propeller blade tips, the minimum distance between propeller(s) and hull (including stern frame) should not be less than h0 (see [7.1.1]).
14.1.3 On twin and triple screw ships the ice strengthening of the shell and framing shall be extended to the double bottom for 1.5 metre forward and aft of the side propellers.
14.1.4 Shafting and stern tubes of side propellers are normally to be enclosed within plated bossings. If detached struts are used, their design, strength and attachment to the hull shall be duly considered. For class Ice(1A*F) the gross skin plating of propeller shaft bossings, in mm, shall not be less than:
14.1.5 The part of a transom stern situated within the ice belt shall be strengthened as for the midship region.
14.2 Rudder and steering arrangements
14.2.1 The scantlings of rudder, rudder post, rudder stock, pintles, steering gear etc. as well as the capacity of the steering gear shall be determined according to the rules. The maximum service speed of the ship to be used in these calculations shall not be taken less than that stated below:
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DNV GL AS Table 14 Maximum service speed 2
Ice class Maximum service speed n o i
Ice(1A*) 20 knots t Ice(1A) 18 knots c e
Ice(1B) 16 knots S
Ice(1C) 14 knots 6
r
If the actual maximum service speed of the ship is higher, that speed shall be used. e t When calculating the rudder force according to the formula given in Pt.3 Ch.14 Sec.1 [4] and with the speed p
V in ahead condition as given above, the factors k1 = k2 = 1.0 irrespective of condition, rudder profile type or a arrangement, shall be used. In the astern condition half the speed values shall be used. h C 14.2.2 For the ice classes Ice(1A*) and Ice(1A), the upper part of the rudder and the rudder stock 6 shall be protected from direct contact with intact ice by an ice horn that extends below the LIWL. Special t
consideration shall be given to the design of the rudder and the ice horn for ships with flap-type rudders. r a
14.2.3 For ice classes Ice(1A*) and Ice(1A), due regard shall be paid to the large loads that arise P when the rudder is forced out of the midship position while going astern in ice or into ice ridges. Suitable arrangement such as rudder stoppers shall be installed to absorb these loads.
14.2.4 Relief valves for hydraulic pressure in rudder turning mechanism(s) shall be installed. The components of the rudder actuator, rudder stock and rudder coupling shall be dimensioned to withstand loading corresponding to the required diameter of the rudder stock.
14.2.5 The local scantlings of rudders shall be determined assuming that the whole rudder belongs to the ice belt. Further, the rudder plating and frames shall be designed using the ice pressure P for the plating and frames in the midbody region.
15 Propulsion machinery
15.1 Engine output
15.1.1 Definition of engine output The engine output PS is the maximum output the propulsion machinery can continuously deliver to the propeller(s). If the output of the machinery is restricted by technical means or by any regulations applicable to the ship, PS shall be taken as the restricted output.
15.1.2 Documentation onboard Minimum engine output corresponding to the ice class shall be given in the Appendix to Classification Certificate.
15.1.3 Required engine output for ice classes Definitions
The dimensions of the ship and some other parameters are defined below:
LBOW = Length of the bow, in m, see Figure 4. L PAR = Length of the parallel midship body, in m, see Figure 4. T = Actual ice class draughts of the ship, in m, according to [1.5.3]. 2 A wf = Area of the waterline of the bow, in m , see Figure 4. α = The angle of the waterline at B/4, in degrees, see Figure 4.
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DNV GL AS φ1 = The rake of the stem at the centreline, in degrees, see Figure 4. 2
φ2 = The rake of the bow at B/4, in degrees, see Figure 4.
ψ = Flare angle, in degrees, calculated as ψ = arc tan(tan φ/sin α) using angles α and φ at each n
location. For subsection [15], flare angle is calculated using φ = φ . o 2 i DP = Diameter of the propeller or outer diameter of nozzle for the nozzle propeller, maximum 1.2 t times propeller diameter, in m. c e HM = Thickness of the brash ice in mid channel, in m. S
HF = Thickness of the brash ice layer displaced by the bow, in m.
RCH = Resistance, in N, of the ship in a channel with brash ice and a consolidated layer (see formula in 6
[15.1.4]). r
Ke = Factor depending on no. of propellers, CPP (or similar), fixed pitch type (see Table 16). e t Pmin = Minimum required engine output, in kW. C = Empirical coefficients (misc. sub index). p f = Empirical factors (misc. sub index). a h g = Empirical factors (misc. sub index). C
L = Length of the ship between the perpendiculars, in m. B = Maximum breadth of ship, in m. 6
t r a
Range of validity P
The range of validity of the formulae for powering requirements in [15.1.4] is presented in Table 15. When calculating the parameter DP/T, T shall be measured at UIWL.
Table 15 Parameter validity range
Parameter Minimum Maximum
α [degrees] 15 55
φ1 [degrees] 25 90
φ2 [degrees] 10 90
L [m] 65.0 250.0
B [m] 11.0 40.0
T [m] 4.0 15.0
LBOW/L 0.15 0.40
LPAR/L 0.25 0.75
DP /T 0.45 0.75
Awf /(L×B) 0.09 0.27
If the ship’s parameter values are beyond the ranges defined in Table 15, other methods for determining RCH shall be used as defined in [15.1.5].
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DNV GL AS 2
n o i t c e S
6
r e t p a h C
6
t r a P
Figure 4 Definitions
15.1.4 The engine output requirement shall be calculated for:
— Upper Ice Waterlines (UIWL) and — Lower Ice Waterlines (LIWL), as defined in Sec.1 [2].
In the calculations the ship's parameters which depend on the draught shall be determined at the appropriate draught, but L and B shall be determined only at the UIWL. The engine output shall not be less than the greater of these two outputs.
The engine output Pmin, in kW, shall not be less than that determined by the formulae and in no case less than given in Table 17:
Guidance note: “New ships” – see [1.4.1] Guidance note. For “existing Ice(1A) and Ice(1A*) ships” see Pt.7 Ch.2 Sec.2 [1].
---e-n-d---of---g-u-i-d-a-n-c-e---n-o-t-e---
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DNV GL AS Table 16 Value of factor Ke for conventional propulsion systems*) 2
Propeller type or machinery n o i
Controllable pitch propeller or electric t Numbers of propellers Fixed pitch propeller or hydraulic propulsion machinery c e
1 propeller 2.03 2.26 S
2 propellers 1.44 1.6 6
r 3 propellers 1.18 1.31 e t )
* For advanced systems see [15.1.5]. p a h Table 17 Minimum engine output Pmin C
Ice(1A), Ice(1B) and Ice(1C) 1000 kW 6
t
Ice(1A*) 2800 kW r a P RCH is the resistance, in N, of the ship in a channel with brash ice and a consolidated layer:
Cμ = 0.15 cos φ2 + sin ψ sin α Cμ ≥ 0.45 (minimum value) C = 0.047 ψ − 2.115 and 0 if ψ ≤ 45° ψ 0.5 HF = 0.26 + (HMB) HM = 1.0 for Ice(1A) and Ice(1A*) = 0.8 for Ice(1B) = 0.6 for Ice(1C).
C1 and C2 take into account a consolidated upper layer of the brash ice and can be taken as zero for ice class Ice(1A), Ice(1B) and Ice(1C).
For ice class Ice(1A*):
For a ship with a bulbous bow, φ1 shall be taken as 90°.
2 f1 = 23 N/m
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DNV GL AS f2 = 45.8 N/m 2 f = 14.7 N/m 3 2 f4 = 29 N/m n
= 1 530 N o g1 i g2 = 170 N/m t
1.5 c g3 = 400 N/m 2 2 e C3 = 845 kg/m s 2 2 S
C = 42 kg/m s 4 2 C5 = 825 kg/s 6
r e t p a
h C
6
shall not be taken less than 5 and not more than 20. t r a
P
15.1.5 Other methods of determining Ke or RCH For an individual ship, in lieu of the Ke or RCH values defined in Table 16 and [15.1.4], the use of Ke or RCH values based on more exact calculations or values based on model tests may be approved. Such approval will be given on the understanding that it can be revoked if experience of the ship’s performance in practice motivates this. Guidance note: For ships intended for trading in Finnish waters and having the propulsion power determined by model tests or by means other than the rule formula, additional approval by Finnish or Swedish authorities is necessary.
---e-n-d---of---g-u-i-d-a-n-c-e---n-o-t-e--- The design requirement for ice classes shall be a minimum speed of 5 knots in the following brash ice channels (see Table 18):
Table 18 Values of HM
Ice class HM
Ice(1A*) 1.0 m and a 0.1 m thick consolidated layer of ice
Ice(1A) 1.0 m
Ice(1B) 0.8 m
Ice(1C) 0.6 m
15.2 Materials
15.2.1 Materials exposed to sea water Materials of components exposed to sea water, such as propeller blades, propeller hubs, and thruster body, shall have an elongation of not less than 15% on a test specimen, the gauge length of which is five times the diameter. A Charpy V impact test shall be carried out for materials other than bronze and austenitic stainless steel. An average impact energy value of 20 J taken from three tests shall be obtained at minus 10ºC.
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DNV GL AS 15.2.2 Materials exposed to sea water temperature 2
Materials exposed to sea water temperature shall be of ductile material. An average impact energy value of 20 J taken from three tests shall be obtained at minus 10ºC. This requirement applies to blade bolts, n o
CP mechanisms, shaft bolts, strut-pod connecting bolts etc. This does not apply to surface hardened i components, such as bearings and gear teeth. t c e S
15.3 Design loads for propeller and shafting 6
15.3.1 These regulations apply to propulsion machinery covering open- and ducted-type propellers with r
controllable pitch or fixed pitch design for the ice classes Ice(1A*), Ice(1A), Ice(1B) and Ice(1C). The e given loads are the expected ice loads for the whole ship's service life under normal operational conditions, t including loads resulting from the changing rotational direction of FP propellers. However, these loads do not p a cover off-design operational conditions, for example when a stopped propeller is dragged through ice. h
The regulations also apply to azimuth’s and fixed thrusters for main propulsion, considering loads resulting C from propeller/ice interaction. However, the load models do not include propeller/ice interaction loads when 6
ice enters the propeller of a turned azimuth thruster from the side (radially) or load case when ice block hits on the propeller hub of a pulling propeller. t r a
15.3.2 Design ice conditions P In estimating the ice loads of the propeller for ice classes, different types of operation as given in Table 19 were taken into account. For the estimation of design ice loads, a maximum ice block size is determined. The maximum design ice block entering the propeller, is a rectangular ice block with the dimensions Hice × 2Hice × 3Hice. The thickness of the ice block (Hice) is given in Table 20.
Table 19 Operation of the ship - design basis
Ice(1A*) Operation in ice channels and in level ice. The ship may proceed by ramming
Ice(1A)…1C Operation in ice channels
Table 20 Thickness of the design maximum ice block Hice entering the propeller
Ice Class Ice(1A*) Ice(1A) Ice(1B) Ice(1C)
(Hice) 1.75 m 1.5 m 1.2 m 1.0 m
Table 21 List of symbols
Symbol Unit Definition
A.P. the after perpendicular is the perpendicular at the after end of the length L
c m chord length of blade section
c0.7 m chord length of blade section at 0.7R propeller radius
CP controllable pitch
D m propeller diameter
d m external diameter of propeller hub
Dlimit m limit value for propeller diameter
EAR expanded blade area ratio
Fb kN maximum backward blade force for the ship’s service life
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DNV GL AS Symbol Unit Definition 2
Fex kN ultimate blade load resulting from blade loss through plastic bending n o F kN maximum forward blade force for the ship’s service life i
f t c F kN ice load
ice e S
(Fice)max kN maximum ice load for the ship’s service life 6
FP fixed pitch r
F.P. the forward perpendicular is the perpendicular at the intersection of the summer load waterline with e t the fore sideof the stem. For ships with unusual bow arrangements the position of the F.P. will be p especially considered. a h h0 m depth of the propeller centreline from the winter waterline C
Hice m thickness of maximum design ice block entering to propeller 6
2 I kgm equivalent mass moment of inertia of all parts on engine side of component under consideration t r
2 a It kgm equivalent mass moment of inertia of the whole propulsion system P k shape parameter for Weibull distribution
LIWL m lower ballast waterline in ice
m slope for SN curve in log/log scale
MBL kNm blade bending moment
MCR maximum continuous rating
n rev/s propeller rotational speed
nn rev/s nominal propeller rotational speed at MCR in free running condition
Nclass reference number of impacts per propeller rotational speed per ice class
Nice total number of ice loads on propeller blade for the ship’s service life 8 NR reference number of load for equivalent fatigue stress (10 cycles)
NQ number of propeller revolutions during a milling sequence
P0.7 m propeller pitch at 0.7R radius
P0.7n m propeller pitch at 0.7R radius at MCR in free running condition
P0.7b m propeller pitch at 0.7R radius at MCR in bollard condition
Q kNm torque
Qemax kNm maximum engine torque
Qmax kNm maximum torque on the propeller resulting from propeller-ice interaction
Qmotor kNm electric motor peak torque
Qn kNm nominal torque at MCR in free running condition
Qr kNm maximum response torque along the propeller shaft line
Qsmax kNm maximum spindle torque of the blade for the ship’s service life
R m propeller radius
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DNV GL AS Symbol Unit Definition 2
r m blade section radius n o T kN propeller thrust i t c T kN maximum backward propeller ice thrust for the ship’s service life
b e S
Tf kN maximum forward propeller ice thrust for the ship’s service life 6
Tn kN propeller thrust at MCR in free running condition r
Tr kN maximum response thrust along the shaft line e t
t m maximum blade section thickness p a
Z number of propeller blades h C αi deg duration of propeller blade/ice interaction expressed in rotation angle 6
γε the reduction factor for fatigue; scatter and test specimen size effect t r
γν the reduction factor for fatigue; variable amplitude loading effect a P γm the reduction factor for fatigue; mean stress effect
ρ a reduction factor for fatigue correlating the maximum stress amplitude to the equivalent fatigue stress for 108 stress cycles
σ0.2 MPa proof yield strength of blade material 8 σexp MPa mean fatigue strength of blade material at 10 cycles to failure in sea water 8 σfat MPa equivalent fatigue ice load stress amplitude for 10 stress cycles
σfl MPa characteristic fatigue strength for blade material
σref MPa reference stress (ultimate strength) σref = 0.6 σ0.2 + 0.4 σu
σref2 MPa reference stress (blade scantlings) σref2 = 0.7 σu or σref2 = 0.6 σ0.2 + 0.4 σu whichever is less
σst MPa maximum stress resulting from Fb or Ff
σu MPa ultimate tensile strength of blade material
(σice)bmax MPa principal stress caused by the maximum backward propeller ice load
(σice)fmax MPa principal stress caused by the maximum forward propeller ice load
(σice)max MPa maximum ice load stress amplitude
Table 22 Definition of ice loads
Load Definition Use of the load in design process
Fb The maximum lifetime backward force on a propeller Design force for strength calculation of the propeller blade resulting from propeller/ice interaction, including blade. hydrodynamic loads on that blade. The direction of the force is perpendicular to 0.7 r/R chord line. See Figure 5
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DNV GL AS Load Definition Use of the load in design process 2
Ff The maximum lifetime forward force on a propeller Design force for calculation of strength of the propeller n
blade resulting from propeller/ice interaction, including blade. o i
hydrodynamic loads on that blade. The direction of the t force is perpendicular to 0.7 r/R chord line. c e
Qsmax The maximum lifetime spindle torque on a propeller In designing the propeller strength, the spindle torque S
blade resulting from propeller/ice interaction, including is automatically taken into account because the 6
hydrodynamic loads on that blade. propeller load is acting on the blade as distributed pressure on the leading edge or tip area. r e t T The maximum lifetime thrust on propeller (all blades) Is used for estimation of the response thrust T . T can
b r b p
resulting from propeller/ice interaction. The direction of be used as an estimate of excitation for axial vibration a
the thrust is the propeller shaft direction and the force calculations. However, axial vibration calculations are h
is opposite to the hydrodynamic thrust. not required in the rules. C
Tf The maximum lifetime thrust on propeller (all blades) Is used for estimation of the response thrust Tr.Tf can 6
resulting from propeller/ice interaction. The direction of be used as an estimate of excitation for axial vibration t the thrust is the propeller shaft direction acting in the calculations. However, axial vibration calculations are r direction of hydrodynamic thrust. not required in the rules. a P
Qmax The maximum ice-induced torque resulting from Is used for estimation of the response torque (Qr) propeller/ice interaction on one propeller blade, along the propulsion shaft line and as excitation for including hydrodynamic loads on that blade. torsional vibration calculations.
Fex Ultimate blade load resulting from blade loss through Blade failure load is used to dimension the blade bolts, plastic bending. The force that is needed to cause total pitch control mechanism, propeller shaft, propeller failure of the blade so that plastic hinge is caused to the shaft bearing and trust bearing. The objective shall root area. The force is acting on 0.8 r/R. Spindle arm guarantee that total propeller blade failure should not shall be taken as 2/3 of the distance between the axis cause damage to other components. of blade rotation and leading/trailing edge (whichever is the greater) at the 0.8R radius.
Qr Maximum response torque along the propeller shaft Design torque for propeller shaft line components. line, taking into account the dynamic behaviour of the shaft line for ice excitation (torsional vibration) and hydrodynamic mean torque on propeller.
Tr Maximum response thrust along shaft line, taking into Design thrust for propeller shaft line components. account the dynamic behaviour of the shaft line for ice excitation (axial vibration) and hydrodynamic mean thrust on propeller.
Qg Fatigue torque at reduction gear for Ng load cycles. Design torque for reduction gear.
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DNV GL AS 2
n o i t c e S
6
r e t p a h C
6
t r a P
Figure 5 Direction of the backward blade force resultant taken perpendicular to chord line at 0.7 r/R
(Ice contact pressure at leading edge is shown with small arrows)
15.4 Design loads
15.4.1 The given loads are intended for component strength calculations only and are total loads including ice-induced loads and hydrodynamic loads during propeller/ice interaction.
15.4.2 The values of the parameters in the formulae in this section shall be given in the units shown in the symbol list.
15.4.3 If the propeller is not fully submerged when the ship is in ballast condition, the propulsion system shall be designed according to ice class Ice(1A) for ice classes Ice(1B) and Ice(1C).
15.5 Design loads on propeller blades
15.5.1 Fb is the maximum force experienced during the lifetime of the ship that bends a propeller blade backwards when the propeller mills an ice block while rotating ahead. Ff is the maximum force experienced during the lifetime of the ship that bends a propeller blade forwards when the propeller mills an ice block while rotating ahead. Fb and Ff originate from different propeller/ice interaction phenomena, not acting simultaneously. Hence they shall be applied to one blade separately.
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DNV GL AS 15.5.2 Maximum backward blade force Fb, in kN, for open propellers 2
n o i t
c e S
6
r
e t p a h
C
6
t r
a where P
n is the nominal rotational speed (at MCR in free running condition) for a CP propeller and 85% of the nominal rotational speed (at MCR in free running condition) for an FP propeller.
15.5.3 Maximum forward blade force Ff, in kN, for open propellers
where
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DNV GL AS 15.5.4 Loaded area on the blade for open propellers 2
Load cases 1 to 4 have to be covered, as given in Table 23 below, for CP and FP propellers. The load case 5 applies to reversible propellers in addition to the cases 1 to 4. n o i
Table 23 Load cases for open propellers t c e Load case Force Loaded area Right-handed propeller S
blade seen from behind 6 Load case 1 F Uniform pressure applied on the back of b r
the blade (suction side) to an area from e
0.6R to the tip and from the leading edge t to 0.2 times the chord length. p a h C
6
t r a P
Load case 2 50% of Fb Uniform pressure applied on the back of the blade (suction side) on the propeller tip area outside 0.9R radius.
Load case 3 Ff Uniform pressure applied on the blade face (pressure side) to an area from 0.6R to the tip and from the leading edge to 0.2 times the chord length.
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DNV GL AS Load case Force Loaded area Right-handed propeller 2
blade seen from behind n
Load case 4 50% of Ff Uniform pressure applied on propeller o i
face (pressure side) on the propeller tip t area outside 0.9R radius. c e S
6
r e t p a h C
6
Load case 5 60% of Ff or Uniform pressure applied on propeller t
Fb, whichever face (pressure side) to an area from 0.6R r is greater to the tip and from the trailing edge to a 0.2 times the chord length P
15.5.5 Maximum backward blade ice force Fb, in kN, for ducted propellers
where
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DNV GL AS n is the nominal rotational speed (at MCR in free running condition) for a CP propeller and 85% of the 2 nominal rotational speed (at MCR in free running condition) for an FP propeller. n
15.5.6 Maximum forward blade ice force Ff, in kN, for ducted propellers o i
t c e S
6
r e t
p a
h C
6
t r a P
where
15.5.7 Loaded area on the blade for ducted propellers Load cases 1 and 3 have to be covered as given in Table 24 for all propellers, and an additional load case (load case 5) for an FP propeller, to cover ice loads when the propeller is reversed.
Table 24 Load cases for ducted propellers
Load case Force Loaded area Right handed propeller blade seen from behind
Load case 1 Fb Uniform pressure applied on the back of the blade (suction side) to an area from 0.6R to the tip and from the leading edge to 0.2 times the chord length.
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DNV GL AS Load case Force Loaded area Right handed propeller 2
blade seen from behind n
Load case 3 Ff Uniform pressure applied on the blade face o i
(pressure side) to an area from 0.6R to the t tip and from the leading edge to 0.5 times c the chord length. e S
6
r e t p a
h C Load case 5 60% of Uniform pressure applied on propeller face 6
Ff or Fb, (pressure side) to an area from 0.6R to the tip and from the trailing edge to 0.2 times t
whichever is r
greater the chord length. a P
15.5.8 Maximum blade spindle torque Qsmax for open and ducted propellers The spindle torque Qsmax, in kNm, around the axis of the blade fitting shall be determined both for the maximum backward blade force Fb and forward blade force Ff, which are applied as in Table 23 and Table 24. If the above method gives a value which is less than the default value given by the formula below, the default value shall be used.
where c0.7 is the length of the blade section at 0.7R radius and F is either Fb or Ff, whichever has the greater absolute value.
15.5.9 Load distribution for blade loads The Weibull-type distribution (probability of exceeding), as given in Figure 6, is used for the fatigue design of the blade.
Here, k is the shape parameter of the spectrum, Nice is the number of load cycles in the spectrum, and Fice is the random variable for ice loads on the blade, 0 ≤ Fice ≤ (Fice)max. The shape parameter k = 0.75 shall be used for the ice force distribution of an open propeller and the shape parameter k = 1.0 for that of a ducted propeller blade.
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DNV GL AS 2
n o i t c e S
6
r e t p a h C
6
t
Figure 6 The Weibull-type distribution (probability of exceeding) that is used for fatigue design r a
15.5.10 Number of ice loads P The number of load cycles per propeller blade in the load spectrum shall be determined according to the formula:
where: n is propeller nominal rps as defined for loads.
Table 25 Reference number of loads for ice classes Nclass
Ice(1A*) Ice(1A) Ice(1B) Ice(1C)
Impacts in life/n 9·106 6·106 3.4·106 2.1·106
Table 26 Propeller location factor k1
Single propeller Twin propeller
location centreline twin wing
k1 1 1.35
Table 27 Propeller type factor k2
type open ducted
k2 1 1.1
Table 28 Propulsion type factor k3
type fixed azimuting
k3 1 1.2
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DNV GL AS The submersion factor k4 is determined from the equation 2
n o i t c e S
6 where the immersion function f is: r
e t p a
h C
where ho is the depth of the propeller centreline at the lower ballast waterline in ice (LIWL) of the ship.
For components that are subject to loads resulting from propeller/ice interaction with all the propeller blades, 6
the number of load cycles (Nice) shall be multiplied by the number of propeller blades (Z). t r a 15.6 Axial design loads for open and ducted propellers P
15.6.1 Design ice thrust on propeller Tb and Tf for open and ducted propellers The maximum forward and backward ice thrusts, in kN, are:
15.6.2 Design thrust along the propulsion shaft line for open and ducted propellers The design thrust, in kN, along the propeller shaft line shall be calculated with the formulae below. The greater value of the forward and backward direction loads shall be taken as the design load for both directions. The factors 2.2 and 1.5 take into account the dynamic magnification resulting from axial vibration. In a forward direction
In a backward direction
If the hydrodynamic bollard thrust, T, is not known, T shall be taken from Table 29, where Tn is the nominal propeller thrust at MCR in free running open water condition
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DNV GL AS Table 29 Selection of bollard thrust *) 2
Propeller type T n o i
CP propellers (open) 1.25 Tn t c
CP propellers (ducted) 1.1 Tn e S
FP propellers driven by turbine or electric motor Tn 6
FP propellers driven by diesel engine (open) 0.85 Tn r e t FP propellers driven by diesel engine (ducted) 0.75 Tn p
*) When not known a h C
6
15.7 Torsional design loads t r
15.7.1 Design ice torque on propeller Qmax for open propellers a
Qmax is the maximum torque, in kNm, on a propeller resulting from ice/propeller interaction. P
where
For CP propellers, the propeller pitch,P0.7 shall correspond to MCR in bollard condition. If not known, P0.7 shall be taken as 0.7·P0.7n, where P0.7n is the propeller pitch at MCR in free running condition.
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DNV GL AS Table 30 Rotational speed selection *) 2
Propeller type Rotational speed n n o i
CP propellers nn t c
FP propellers driven by turbine or electric motor nn e S
FP propellers driven by diesel engine 0.85 nn 6
) * nn refers to MCR free running condition r e t 15.7.2 Design ice torque on propeller Qmax for ducted propellers p Q is the maximum torque, in kNm, on a propeller resulting from ice/propeller interaction. max a
h C
6
t r a P
where
and n and P0.7 as defined for open propeller.
15.7.3 Ice torque excitation for open and ducted propellers The propeller ice torque excitation for shaft line transient torsional vibration analysis shall be described by a sequence of blade impacts which are of a half sine shape, see Figure 7. The torque resulting from a single blade ice impact as a function of the propeller rotation angle is then
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DNV GL AS where Cq and αi parameters are given in the Table 31 and αi is duration of propeller blade/ice interaction 2 expressed in propeller rotation angle. n o
Table 31 Torque excitation parameters i t c Torque excitation Propeller/ice interaction C a q i e S
Case 1 Single ice block 0.75 90 6
Case 2 Single ice block 1.0 135 r
Case 3 Two ice blocks (phase shift 45 deg.) 0.5 45 e t p
The total ice torque is obtained by summing the torque of single blades, taking into account the phase shift a
360 degrees/Z. In addition, at the beginning and at the end of the milling sequence a linear ramp functions h for 270 degrees of rotation angle shall be used. C
The number of propeller revolutions during a milling sequence shall be obtained with the formula: 6
t r a
P
The number of impacts is Z·NQ for blade order excitation.
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DNV GL AS 2
n o i t c e S
6
r
e For 90- and 135-degree single-blade impact sequences and 45 degree double blade impact sequence (figures t p
apply for propellers with 4 blades.) a
Figure 7 The shape of the propeller ice torque excitation h C
15.7.4 Design torque along propeller shaft line 6 If there is not any relevant first blade order torsional resonance within the designed operating rotational t speed range extended 20% above the maximum and 20% below the minimum operating speeds, the r following estimation of the maximum torque, in kNm, can be used: a P
where I is equivalent mass moment of inertia of all parts on engine side of component under consideration and It is equivalent mass moment of inertia of the whole propulsion system. All the torques and the inertia moments shall be reduced to the rotation speed of the component being examined.
If the maximum torque, Qemax, is not known, it shall be taken as follows, where Qmotor is the electric motor peak torque:
Table 32 Selection of maximum motor torque Qemax
Propeller type Qemax
Propellers driven by electric motor Qmotor
CP propellers not driven by electric motor Qn
FP propellers driven by turbine Qn
FP propellers driven by diesel engine 0.75 Qn
If there is a first blade order torsional resonance within the designed operating rotational speed range extended 20% above the maximum and 20% below the minimum operating speeds, the design torque (Qr) of the shaft component shall be determined by means of torsional vibration analysis of the propulsion line.
15.8 Blade failure load
15.8.1 The ultimate load, in kN, resulting from blade failure as a result of plastic bending around the blade root shall be calculated with the formula below. The ultimate load is acting on the blade at the 0.8R radius in the weakest direction of the blade. For calculation of the extreme spindle torque, the spindle arm shall be taken as 2/3 of the distance between the axis of blade rotation and the leading/trailing edge (whichever is the greater) at the 0.8R radius.
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DNV GL AS 2
n o
i t where c
e S
6
c, t, and r are, respectively, the length, thickness, and radius of the cylindrical root section of the blade at the r e weakest section outside the root fillet. t p a
15.9 Design principle h C
15.9.1 The strength of the propulsion line shall be designed according to the pyramid strength principle. This 6 means that the loss of the propeller blade shall not cause any significant damage to other propeller shaft line t components. r a
15.9.2 The propulsion system shall be designed in such a way that the complete dynamic system is free P from harmful torsional, axial, and bending resonances at a 1-order blade frequency within the designed running speed range, extended by 20 per cent above and below the maximum and minimum operating rotational speeds. If this condition cannot be fulfilled, a detailed vibration analysis has to be carried out in order to determine that the acceptable strength of the components can be achieved.
15.10 Propeller blade design
15.10.1 Calculation of blade stresses The blade stresses shall be calculated for the design loads given in [15.5]. Finite element analysis shall be used for stress analysis for final approval for all propellers. The following simplified formulae can be used in estimating the blade stresses for all propellers at the root area (r/R < 0.5). The root area dimensions will be accepted even if the FEM analysis would show greater stresses, in N/mm2, at the root area.
where the constant R1 is the “actual stress”/“stress obtained with beam equation”.
If the actual value is not available, R1 should be taken as 1.6.
For relative radius r/R < 0.5
F is the maximum of Fb and Ff, whichever is greater.
15.10.2 Acceptability criterion - maximum load (static) The following criterion for calculated blade stresses has to be fulfilled.
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DNV GL AS
2
Where σst is the calculated stress for the design load. If FE analysis is used in estimating the stresses, von
Mises stresses shall be used. n o σref 2 is the reference stress, defined as: i t
σref 2 = 0.7·σu c or e S
σref 2 = 0.6·σ0.2 + 0.4 σu 6 whichever is less. r e
15.10.3 Fatigue design of propeller blade t
The fatigue design of the propeller blade is based on an estimated load distribution for the service life of the p ship and the S-N curve for the blade material. An equivalent stress that produces the same fatigue damage a as the expected load distribution shall be calculated and the acceptability criterion for fatigue should be h fulfilled as given in this section. The equivalent stress is normalised for 100 million cycles. C
If the following criterion is fulfilled fatigue calculations according to this Section are not required. 6
t r a P where B1, B2 and B3 coefficients for open and nozzle propellers are given in the Table 33 below.
Table 33 B coefficients
Coefficient Open propeller Nozzle propeller
B1 0.00270 0.00184
B2 1.007 1.007
B3 2.101 2.470
For calculation of equivalent stress two types of SN curves are available. 1) Two slope SN curve (slopes 4.5 and 10), see Figure 8. 2) One slope SN curve (the slope can be chosen), see Figure 9. The type of the SN-curve shall be selected to correspond to the material properties of the blade. If SN-curve is not known the two slope SN curve shall be used.
Figure 8 Two-slope S-N curve
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DNV GL AS
2
n o i t c e S
6
r e t p a h C
6
Figure 9 Constant-slope S-N curve t r
15.10.4 Equivalent fatigue stress a
The equivalent fatigue stress for 100 million stress cycles which produces the same fatigue damage as the P load distribution is:
where
(σice)max = The mean value of the principal stress amplitudes resulting from design forward and backward blade forces at the location being studied. (σice)f max = The principal stress resulting from forward load. (σice)b max = The principal stress resulting from backward load.
In calculation of (σice)max, load case 1 and load case 3 (or case 2 and case 4) are considered as a pair for (σice)f max, and (σice)b max calculations. Load case 5 is excluded from the fatigue analysis.
15.10.5 Calculation of ρ parameter for two-slope S-N curve The parameter ρ relates the maximum ice load to the distribution of ice loads according to the regression formulae:
where:
γε = The reduction factor for scatter and test specimen size effect. γν = The reduction factor for variable amplitude loading.
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DNV GL AS γm = The reduction factor for mean stress. 8 2 σexp = The mean fatigue strength of the blade material at 10 cycles to failure in seawater. n o
The following values should be used for the reduction factors if actual values are not available: γε = 0.67, γν i t = 0.75, and γm= 0.75. c e The coefficients C1, C2, C3, and C4 are given in Table 34. S
Table 34 C coefficients 6
r
Coefficient Open propeller Nozzle propeller e t p C1 0.000711 0.000509 a
C2 0.0645 0.0533 h C
C3 -0.0565 -0.0459 6
C4 2.22 2.584 t r a
15.10.6 Calculation of ρ parameter for constant-slope S-N curve P For materials with a constant-slope S-N curve, see Figure 9 The ρ-factor shall be calculated with the following formula:
where k is the shape parameter of the Weibull distribution, k = 1.0 for ducted propellers and k = 0.75 for open propellers.
NR is the reference number of load cycles (=100 million). Values for the G parameter are given in Table 35. Linear interpolation may be used to calculate the G value for other m/k ratios than given in the Table 35.
Table 35 Value for the G parameter for different m/k ratios
m/k G m/k G m/k G
3 6 5.5 287.9 8 40 320
3.5 11.6 6 720 8.5 119 292
4 24 6.5 1871 9 362 880
4.5 52.3 7 5040 9.5 1.133•106
5 120 7.5 14034 10 3.623•106
15.10.7 Acceptability criterion for fatigue The equivalent fatigue stress at all locations on the blade has to fulfil the following acceptability criterion:
where:
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DNV GL AS
2
n
o i t
γε = The reduction factor for scatter and test specimen size effect. c γν = The reduction factor for variable amplitude loading. e = The reduction factor for mean stress. S γm = The mean fatigue strength of the blade material at 108 cycles to failure in seawater. σexp 6
r
The following values should be used for the reduction factors if actual values are not available: γε = 0.67, γν e t = 0.75, and γm= 0.75. p a
15.11 Propeller bossing and CP mechanism h C
15.11.1 The blade bolts, the CP mechanism, the propeller boss, and the fitting of the propeller to the 6
propeller shaft shall be designed to withstand the maximum and fatigue design loads, as defined in [15.5]. t The safety factor against yielding shall be greater than 1.3 and that against fatigue greater than 1.5. In r addition, the safety factor for loads resulting from loss of the propeller blade through plastic bending as a defined in [15.8] shall be greater than 1.0 against yielding. P
15.12 Propulsion shaft line
15.12.1 The shafts and shafting components, such as the thrust and stern tube bearings, couplings, flanges and sealing, shall be designed to withstand the propeller/ice interaction loads as given in [15.5] - [15.7]. The safety factor shall be at least 1.3.
15.12.2 The design torque Qr determined according to [15.7] shall be applied for low cycle and high cycle strength analysis respectively.
15.12.3 Shafts and shafting components The ultimate load resulting from total blade failure as defined in [15.8] should not cause yielding in shafts and shaft components. The loading shall consist of the combined axial, bending, and torsion loads, wherever this is significant. The minimum safety factor against yielding shall be 1.0 for bending and torsional stresses. Forward of the after peak bulkhead, the shaft may be evenly tapered down to 1.05 times the rule diameter of intermediate shaft, but not less than the actual diameter of the intermediate shaft.
15.13 Design of shaft line components not specifically mentioned in FSICR
15.13.1 Below criteria are given for application of Pt.4 Ch.4 for determination of scantlings for intermediate shafts, couplings, reduction gears and crank shafts.
Application factor KAice = Qr/Qn for low cycle criteria and/or static load criteria (ref. [15.13.3]). For components where fatigue is dimensioning, e.g. shaft and reduction gear, cumulative fatigue analysis are required. The actual Qr/Qn ratios shall be determined as given in [15.7.4].
15.13.2 The diameter of intermediate shafts shall be determined based on methods given in Pt.4 Ch.4 Sec.1 [2.2.1]. a) When using the Class Guideline DNVGL-CG-0038 the necessary reinforcement is determined by using Qr/Qn in the given criteria. b) With Qr/Qn ≤ 1.4 the method in Pt.4 Ch.4 Sec.1 [2.2.6] may be used, i.e. no ice reinforcement beyond the rules for main class, 1A.
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DNV GL AS When using the method in Pt.4 Ch.4 Sec.1 [2.2.8], the minimum diameter in item 3 of that paragraph shall
1/3 2 be multiplied with:(Qr/1.4 Qn) , where Qr is relevant maximum value, but not less than 1.0. n In item 4 of same paragraph, the vibratory torsional stress τv is replaced by: o i
τv = 0.5 (Qr/Qn - 1) To t c and shall not exceed τC. e S
15.13.3 Regarding shaft connections, use Qr/Qn in Pt.4 Ch.4 Sec.1 as follows: 6
— flange connections, see Pt.4 Ch.4 Sec.1 [2.3] r
— shrink fit connections, see Pt.4 Ch.4 Sec.1 [2.4] e — keyed connections, see Pt.4 Ch.4 Sec.1 [2.5]. t p
Connections transmitting ice axial load determined in [15.8] from the propeller to the thrust bearing shall be a capable of transmitting relevant loads without consequential damage. h C
15.13.4 For reduction gears, use Qr/Qn in Pt.4 Ch.4 Sec.2. 6
t
15.13.5 For clutches, use Qr/Qn in Pt.4 Ch.4 Sec.3 [2.1]. r a P 15.13.6 For torsional elastic coupling, use Qr/Qn in Pt.4 Ch.4 Sec.5 [2.2].
15.13.7 For crank shafts in direct coupled diesel engines, see Pt.4 Ch.3 Sec.1 [2.5.6].
15.14 Azimuth main propulsors and other thrusters
15.14.1 Special consideration shall be given to those loading cases which are extraordinary for propulsion units when compared with conventional propellers. The estimation of loading cases has to reflect the way of operation of the ship and the thrusters. In this respect, for example, the loads caused by the impacts of ice blocks on the propeller hub of a pulling propeller have to be considered. Furthermore, loads resulting from the thrusters operating at an oblique angle to the flow shall be considered. The steering mechanism, the fitting of the unit, and the body of the thruster shall be designed to withstand the loss of a blade without damage. The loss of a blade shall be considered for the propeller blade orientation which causes the maximum load on the component being studied. Typically, top-down blade orientation places the maximum bending loads on the thruster body.
15.14.2 Azimuth thrusters shall also be designed for estimated loads caused by thruster body/ice interaction. The thruster body has to stand the loads obtained when the maximum ice blocks, which are given in the “Design ice conditions” section, strike the thruster body when the ship is at a typical ice operating speed. In addition, the design situation in which an ice sheet glides along the ship's hull and presses against the thruster body should be considered. The thickness of the sheet should be taken as the thickness of the maximum ice block entering the propeller, as defined in the “Design ice conditions” section.
15.14.3 Tunnel thrusters Ice strengthening of tunnel thrusters is not required.
15.14.4 Other thruster Thrusters other than propulsion thrusters and tunnel thrusters need only comply with the relevant requirements in [15] if they shall be used in ice conditions or for any reason be exposed to ice loads. For thrusters that are not intended for use in ice conditions, this will be stated in the class certificate and on signboards fitted at all relevant manoeuvring stands.
15.14.5 The relevant structure parts of non-retractable thrusters shall be strengthened with respect to ice loads, independent of whether they are used in ice conditions or not.
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DNV GL AS 2 15.15 Alternative design n o
15.15.1 Scope i t
As an alternative to [15.3]to[15.14], a comprehensive design study may be carried out to the satisfaction c
of the Administration. The study has to be based on ice conditions given for different ice classes in [4.1]. It e
has to include both fatigue and maximum load design calculations and fulfil the pyramid strength principle, as S given in [15.9]. 6
15.15.2 Loading r e
Loads on the propeller blade and propulsion system shall be based on an acceptable estimation of t
hydrodynamic and ice loads. p a
15.15.3 Design levels h
The analysis shall indicate that all components transmitting random (occasional) forces, excluding propeller C blade, are not subjected to stress levels in excess of the yield stress of the component material, with a 6 reasonable safety margin. t
Cumulative fatigue damage calculations are to indicate a reasonable safety factor. Due account shall be taken r of material properties, stress raisers, and fatigue enhancements. a P Vibration analysis shall be carried out and is to indicate that the complete dynamic system is free from harmful torsional resonances resulting from propeller/ice interaction.
16 Miscellaneous machinery requirements
16.1 Starting arrangements
16.1.1 The capacity of the air receivers shall be according to the requirements in Pt.4 Ch.6 Sec.5 [9]. If the air receivers serve any other purposes than starting the propulsion engine, they shall have additional capacity sufficient for these purposes. The capacity of the air compressors shall be sufficient for charging the air receivers from atmospheric to full pressure in one (1) hour, except for a ship with the ice class Ice(1A*) if its propulsion engine has to be reversed for going astern, in which case the compressors shall be able to charge the receivers in half an hour.
16.2 Sea inlet and cooling water systems
16.2.1 The cooling water system shall be designed to ensure supply of cooling water when navigating in ice. The sea cooling water inlet and discharge for main and auxiliary engines shall be so arranged that blockage of strums and strainers is prevented. For this purpose at least one cooling water inlet chest shall be arranged as follows: 1) The sea inlet shall be situated near the centre line of the ship and well aft if possible. The inlet grids shall be specially strengthened. 2) As a guidance for design the volume of the chest shall be about one cubic metre for every 750 kW engine output of the ship including the output of the auxiliary engines necessary for the ship's service. 3) To allow for ice accumulation above the pump suction the height of the sea chest shall not be less than:
where:
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DNV GL AS Vs= Volume of sea chest according to item 2. 2
The suction pipe inlet shall be located not higher than hmin/3 from top of sea chest. n o 4) A pipe for discharge cooling water, allowing full capacity discharge, shall be connected to the chest. i t
Where the sea chest volume and height specified in 2 and 3 are not complied with, the discharge shall c
be connected to both sea chests. At least one of the fire pumps shall be connected to this sea chest or to e
another sea chest with de-icing arrangements. S 5) The area of the strum holes shall be not less than four (4) times the inlet pipe sectional area. 6
If there are difficulties in meeting the requirements of 2) and 3) above, two smaller chests may be arranged r for alternating intake and discharge of cooling water. The arrangement and situation otherwise shall be as e above. t p
Heating coils may be installed in the upper part of the chest or chests. a
Arrangements using ballast water for cooling purposes may be useful as a reserve in ballast condition but h cannot be accepted as a substitute for sea inlet chests as described above. C
6
t
16.3 Ballast system r a
16.3.1 An arrangement to prevent freezing of the ballast water shall be provided for inside ballast tanks P located fully or partly above the LIWL, adjacent to the ship's shell, and which need to be filled for operation in ice conditions according to [1.5.4]. For this purpose the following ambient temperatures shall be taken as design conditions: — sea water temperature: 0°C — air temperature: –10°C. Necessary calculations shall be submitted.
16.3.2 When a tank is situated partly above the LIWL, an air-bubbling arrangement or a vertical heating coil, capable of maintaining an open hole in the ice layer, will normally be accepted. The required heat-balance calculations may then be omitted. Guidance note: It is assumed that, before pumping of ballast water is commenced, proper functioning of level gauging arrangements is verified and air pipes are checked for possible blockage by ice.
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17 Guidelines for strength analysis of the propeller blade using finite element method See App.A for guidelines on strength analysis of the propeller blade using finite element method.
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DNV GL AS SECTION 3 OPERATIONS IN COLD CLIMATE - WINTERIZED 3
n o
1 General i t c 1.1 Introduction e S
The additional class notation Winterized establishes requirements for ensuring that a ship is capable of 6 being suitably prepared for operations in low temperatures. This is provided for by setting requirements for important shipboard functions, systems and equipment intended to be in operation in the specified design r e environmental conditions. The design environmental conditions include cold air, cold sea water and wind. t p a
1.2 Scope h C
The scope for additional class notation Winterized specifies functions, systems and equipment essential for safety of the ship, personnel and the environment, operating in adverse cold climate conditions. Such 6
conditions include; freezing sea spray, atmospheric icing, wind chill factor, and the properties of materials t in cold temperatures. Winterization measures encompass: protection of important shipboard functions, r systems and equipment, provisioning suitable equipment and supplies, and implementing procedures for safe a P operation and personnel welfare. Other functions, such as systems and equipment important for commercial operations may also be affected by cold climate and can benefit from winterization measures. However, the winterized notation does not address these issues where they are not essential to safety; nor do they address those hull and machinery requirements necessary for safe navigation through sea ice, which is addressed in the ice class rules.
1.3 Application The additional class notation Winterized applies to ships constructed and equipped, surveyed and tested in accordance with the rules of this section and may be assigned the class notation Winterized with relevant qualifiers defined in Table 1. One, and only one, of the qualifiers Basic, Cold or Polar, is mandatory. The qualifier td is mandatory for Cold or Polar and is optional for Basic. The qualifier Enhanced is optional and can be selected together with Basic or Cold. The qualifier Enhanced may be assigned to a ship that fulfils additional requirements at a higher level of winterization. For example, a ship that fulfils all requirements for qualifier Basic and several additional elements from Cold may be assigned the qualifier Enhanced. The specific enhancements will be listed in the appendix to the ship's classification certificate.
1.4 Class notations Ships built in compliance with the requirements as specified in Table 1 will be assigned the additional notation related to structural strength and integrity as follows:
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DNV GL AS Table 1 Additional class notation related to cold climate 3
Class Notation Qualifier Purpose Application n o i
Winterized Basic Occasional operation in cold t climate for short periods c e
Mandatory: Cold Regular operation in cold S
No climate or for an extended 6
period of time
r
Design requirements: Polar Operation in extreme cold e t climate of the polar regions [5] and [6] p year-round a h FiS requirements: td Design temperature C
Pt.7 Ch.1 Sec.2, Pt.7 Enhanced Additional requirements of a 6
Ch.1 Sec.3 and Pt.7 Ch.1 higher level of winterization Sec.4 t r a
1.4.1 Use of qualifiers P One and only one of the qualifiers Basic, Cold or Polar, is mandatory.
The qualifier td is mandatory for Cold or Polar; it is optional for Basic. The qualifier Enhanced is optional and can be selected together with Basic or Cold.
1.4.2 Qualifier Enhanced may be assigned to a ship that fulfils additional requirements of a higher level of winterization. For example, a ship that fulfils all requirements for qualifier Basic and several additional elements from Cold may receive the qualifier Enhanced. The specific enhancements will be listed in the Appendix to the ship’s Classification Certificate. Guidance note: This feature is meant to recognize and document additional winterization enhancements of a ship and include them in survey process, as particular winterization features are of increasing importance to ship owners, charterers and vetting agents.
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1.4.3 Syntax of class notation and qualifiers Order of appearance: 1 Winterized, 2 Basic, Cold or Polar, 3 t and 4 Enhanced. td shall be indicated in °C. Qualifiers shall be surrounded by parentheses.
Examples: Winterized(Basic)
Winterized (Cold, -20°C)
Winterized (Cold, -20°C, Enhanced)
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DNV GL AS 3 1.5 Definitions n o
1.5.1 Terminology and definitions i t c Table 2 Terminology and definitions e S Terms Definition 6
active measures winterization measures that rely primarily on energy to address the adverse effects of icing, r
freezing or wind chill; e.g., heat, physical force and circulation of liquids. e t
anti-icing measures to prevent ice from forming on surfaces, structures or equipment. The intent of p anti-icing is that the surfaces, structures or equipment are immediately available. a h
de-icing measures to remove snow and ice accumulations from surfaces, structures or equipment. C The intent of de-icing is that the surfaces, structures or equipment can be made available 6
within a reasonable amount of time. t design environmental environmental conditions for which the ship is designed to operate. For winterization, the r a conditions key design environmental conditions are air temperature, sea water temperature and wind P speed.
design temperature (td) reference air temperature used as a criterion for the selection, testing and use of materials and equipment for low temperature service. Same as design temperature used in the notation DAT (see Sec.4).
F.P. the forward perpendicular is the perpendicular at the intersection of the summer load waterline with the fore side of the stem. For ships with unusual bow arrangements the position of the F.P. will be especially considered.
functional requirement requirements that provide the fundamental rationale behind a particular rule.
main functions the main functions of a ship in the context of class as defined in Pt.1 Ch.1 Sec.1 [1.22].
passive measures winterization measures that do not rely primarily on energy to address the adverse effects of icing, freezing or wind chill; e.g., shielding, enclosures, insulation and building-in areas or equipment.
performance requirement requirements that explain in greater detail the type of performance a winterization measure must achieve in order to fulfil the intent of the functional requirement.
sea spray icing icing caused by the freezing of sea spray on ship surfaces, structures and equipment.
winterization measures taken to ensure a ship is capable of and suitably prepared for operations in low temperatures. Winterization is primarily focused on the adverse effects and control of freezing, icing, wind chill and material properties in cold temperature.
1.5.2 Reference to other documents Documents referenced in this section are listed in Table 2.
Table 3 Reference to other documents
Document reference Title
CSA Standard C22.2 No. 0.3 Test methods for electrical wires and cables
IEC 60945 Maritime navigation and radio communication equipment and systems – General requirements – Methods of testing and required test results
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DNV GL AS Document reference Title 3
IMO Res. A.1024(26) Guidelines for ships operating in polar waters n o IMO Res. MSC/81(70) Revised recommendation on testing of life-saving appliances i t c ISO 3434 Ships and marine technology – Heated glass panes for ships’ rectangular windows e S
ISO 8863 Ship’s wheelhouse windows – Heating by hot air of glass panes 6
ISO 17899 Ships and marine technology – Marine electric window wipers r
LSA Code International life-saving appliances code e t
MARPOL Annex I Regulations for the prevention of pollution by oil p a
SOLAS Chapter IV Radio communications h C
IS Code International code on intact stability 6
t r
2 Documentation a P
2.1 Documentation requirements For general requirements to documentation, including definition of the Info codes, see Pt.1 Ch.3 Sec.2. For a full definition of the documentation types, see Pt.1 Ch.3 Sec.3. Documentation shall be submitted as required by Table 3.
Table 4 Documentation requirements
Object Documentation type Additional description Info Qualifier
Accommodation S120 - Heat balance Indicating the heating consumption based on an AP Cold heating system calculation external ambient temperature of 20°C below the Polar design temperature (td).
Ballast tanks S010 - Piping diagram Anti-freezing arrangement. AP (PD)
S120 - Heat balance Indicating anti-freezing capacity required for tanks FI calculation located fully or partly above the water line or lower ice water line (LIWL), whichever is lower.
Cables Z262 - Report from test To at least 10°C colder than the design temperature FI Cold at manufacturer (td). Polar
Cargo H080 - Strength Under conditions of snow and ice loading. FI Cold hatches.Service analysis Polar hatches
Emergency electric S120 - Heat balance Indicating the heating consumption based on an AP Cold power generation calculation external ambient temperature of 20°C below the Polar arrangement design temperature (td).
Escape routes G120 - Escape route Including anti-icing protection. AP drawing
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DNV GL AS Object Documentation type Additional description Info Qualifier 3
External Z262 - Report from test To the design temperature (td), where td is colder FI n
communications at manufacturer than -25°C. o i
systems t c
Fire-fighting S011 - Piping and Indicating anti-freezing arrangement, including AP e
systems instrumentation drains (for self-draining systems), heat tracing and S
diagram (P&ID) insulation. 6
S120 - Heat balance Indicating anti-freezing capacity required. FI r
calculation e t
Fresh water tanks S010 - Piping diagram Indicating anti-freezing arrangement. AP p (PD) a h
S120 - Heat balance Indicating anti-freezing capacity required. FI C
calculation 6
Helicopter deck H080 - Strength Under conditions of snow and ice loading. FI t r analysis a
Machinery spaces S120 - Heat balance Indicating the heating consumption based on an AP Cold P heating system calculation external ambient temperature of 20°C below the Polar design temperature (td).
Main electric power E040 - Electrical load Including winterization systems as a separate mode. AP generation balance
Navigation lights Z262 - Report from test To -25°C or the design temperature (td), whichever is FI at manufacturer colder.
Navigation systems Z262 - Report from test To -25°C or the design temperature (td), whichever is FI at manufacturer colder.
Navigation bridge N030 - Horizontal field Including anti-icing arrangement to bridge windows, AP of vision drawing wipers and washers.
Oil pollution Z265 - Calculation Accidental oil outflow performance in accordance with FI Polar prevention report MARPOL Annex I Reg. 23.
Propulsion Z100 - Specification Stern tube and controllable pitch propeller oils. AP Polar and steering arrangements
Radar systems Z262 - Report from test To -25°C or the design temperature (td), whichever is FI at manufacturer colder.
Rescue boat G160 - Life-saving Including anti-icing protection. AP arrangements arrangement plan
Stability B030 - Internal FI watertight integrity plan
B050 - Preliminary AP stability manual
B130 - Final damage AP stability calculation
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DNV GL AS Object Documentation type Additional description Info Qualifier 3
Steam and thermal S030 - Capacity Indicating boiler capacity required for supplying anti- FI n
oil system analysis icing, anti-freezing and de-icing arrangements. o i t
Survival craft G160 - Life-saving Including anti-icing protection. AP c
arrangements arrangement plan e S
Winterization Z051 - Design basis Including description of the overall winterization FI
arrangements design arrangement, indicating how each applicable 6
item in the notation has been addressed in the r
winterization design. e t
E050 - Single line For anti-icing and anti-freezing systems, including: AP p diagrams / consumer full load; cable types and cross sections; make, a h list for switchboards type and rating of fuses, switching gear and heating C
cables. 6
E170 - Electrical For anti-icing and anti-freezing systems, including: AP t
schematic drawing control and instrumentation circuits, including make, r
type and rating of all equipment. a P S120 - Heat balance For anti-icing and anti-freezing systems, indicating FI calculation heating capacities required and provided.
Z030 - Arrangement Including anti-icing, anti-freezing and de-icing AP plan systems; heating capacity for each area; fastening arrangement and spacing of electrical cables and fluid pipes; and installation protection details of electrical cables.
Z253 - Test procedure Including anti-icing, anti-freezing and de-icing AP for quay and sea trial systems.
Z161 - Operation Including: AP manual — cold climate operations and planning: cold climate hazards, icing prediction, meteorological and route planning, ship-hand-ling in icing conditions; — winterization preparations and procedures: general precautionary measures; description, location and operating procedures for installed winterization features; system-specific winterization measures; de-icing procedures; — procedures for special operations in cold climate: ballasting, cargo operations, mooring, anchoring, and other relevant operations for ship type; — personnel protection; and — cold climate operation checklists: winterization preparations; routine winterization checks; additional actions for special operations in cold climate.
AP = For approval; FI = For information
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DNV GL AS 3 3 Certification n o i 3.1 Certification requirements t c
For a definition of the certificate types see Pt.1 Ch.3 Sec.5 e S
3.1.1 Products shall be certified as required by Table 4. 6
Table 5 Certification requirements r e t
Object Certificate Issued by Certification standard* Additional description p a type h
Lifeboat PC Manufacturer Including stowage down to −30°C or 20°C C
colder than the design temperature (t ), d 6
whichever is colder; and operation to −15°C or t
the design temperature (td), whichever is colder. r a
Life raft PC Manufacturer Including stowage down to −30°C or 20°C P colder than the design temperature (td), whichever is colder; and operation to −15°C or the design temperature (td), whichever is colder. * Unless otherwise specified the certification standard is the rules.
4 Design environmental conditions
4.1 General
4.1.1 The design temperature (td) value shall be specified in degrees Celsius. Where the ship has also the class notation DAT(t), the design temperature for the two notations shall be the same. Typical environmental conditions for qualifiers Basic, Cold and Polar are listed in Table 5. The values are representative but not necessarily prescriptive.
Table 6 Typical design environmental conditions
Qualifier Air temperature (td) Sea water temperature Wind speed
Basic ≤ −10°C +4°C without ice class 20 m/s (−10°C is default) −2°C with ice class
Cold +2°C without ice class −15°C to −30°C 20 m/s −2°C with ice class
Polar < −25°C −2°C 20 m/s
Guidance note: td should reflect the lowest mean daily average air temperature in the area of operation, where
mean = statistical mean over the observation period (at least 20 years)
daily average = average during a 24-hour period
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DNV GL AS lowest = lowest during a year. 3
For seasonally restricted service, the lowest value during the period of operation applies. n o For ships with ice class, the design sea water temperature is the freezing point of sea water. As the freezing point varies with salinity i t
(from −2°C in normal sea water to 0°C in fresh water), this should be taken into consideration where appropriate when making c
calculations in connection with the notation. e S
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4.1.2 Specific requirements for winterized notation are listed in Table 6. In the table, items marked with an X r are applicable for the relevant qualifier. e t
4.1.3 Required additional class notations p a For qualifier Basic, class notation DAT(t) is mandatory if td < −10°C. h
For qualifier Cold, either class notation DAT(t) or PC is mandatory. C
For qualifier Polar, an ice class notation PC, class notation Clean, and either class notation DAT(t) or PC 6 are mandatory. t r
4.1.4 Functional, performance and prescriptive requirements a The notation adopts a three-tiered approach. First, winterization requirements are based upon fulfilling the P stated functional requirements. The functional requirements provide the fundamental rationale and intent behind a particular rule. Second, some functional requirements are supported by one or more performance requirements. These explain in greater detail the type of performance a winterization measure must achieve in order to fulfill the intent of the functional requirement, either in part or in whole. Third, functional and performance requirements are supported by prescriptive rules and guidance notes. These provide a set of generally acceptable solutions to meet the functional and performance requirements, either in part or in whole.
4.1.5 Prescriptive requirements do not preclude the use of other alternative solutions. Such solutions will be considered by their ability to fulfill the relevant functional and performance requirements.
4.1.6 Equipment not otherwise mentioned in these rules and which in the opinion of the Society is essential for safety shall function properly in the design environmental conditions. Such equipment shall be provided with anti-icing and anti-freezing protection as appropriate, and shall be constructed of material appropriate for the design temperature (td). Equipment material shall be selected according to C1001 in Table 6, as appropriate.
5 General requirements
5.1 Anti-icing and anti-freezing measures
5.1.1 Winterization measures required by Table 6 shall fulfil the functional requirements, and shall be considered for approval in each case.
5.1.2 Where anti-icing and anti-freezing measures are required for areas and equipment in Table 6, the following are examples of acceptable solutions: Equipment and areas that require anti-icing measures should as far as possible be situated in protected locations, so that sea spray cannot reach it. This may be accomplished by using fully enclosed spaces, semi- enclosures, recesses with removable “curtains” in front, or similar. A shielded location will be the simplest and most reliable solution for anti-icing wherever it is possible. Heating of spaces may be necessary depending on the type of equipment located therein.
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DNV GL AS Hard removable covers may also be applicable for some types of equipment. Cover by canvas may be 3 acceptable for some types of equipment, like fire monitors. Supply of heated air may be an alternative if the equipment in question is enclosed under a cover, hard cover or canvas. n o
The use of electric heating blankets or heat tracing can be a solution for protection of equipment on open i deck. t c
Guidance note: e
At higher levels of winterization, preference is given to passive measures for anti-icing/anti-freezing protection (such as enclosures) S
versus de-icing or active measures for anti-icing/anti-freezing protection (such as heat tracing). Passive measures are inherently 6
more effective, more efficient, and contribute to reducing emissions to the environment. r
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5.1.3 The heating capacity for anti-icing and anti-freezing arrangements shall be sufficient to prevent icing or a
freezing under the design environmental conditions. Anti-icing and anti-freezing arrangements must be able h
to maintain a surface temperature of at least +3°C under the design environmental conditions. C
6
5.1.4 In anti-icing and anti-freezing arrangements using heating, special attention shall be paid to the heat transfer from the heating cables or pipes to the equipment or structure to be heated. The spacing t r
and fastening of heating cables or pipes shall be appropriate for efficient heating to keep the equipment or a
structure ice-free under the design environmental conditions. Appropriate spacing shall be established by P heat balance calculations.
5.1.5 For anti-icing and de-icing arrangements applying heating by fluids in pipes, the installation shall ensure that the heating fluid maintains its heating effectiveness under the design environmental conditions. The appropriate amount of insulation and the rate of circulation shall be established by heat balance calculations.
5.1.6 Where heated fluids are used for winterization purposes, their process plants shall have sufficient capacity to simultaneously supply all normal consumers and the winterization systems under the design environmental condition.
5.2 De-icing measures
5.2.1 Where removal of ice prior to taking equipment into use is acceptable, de-icing may be carried out by fixed heating arrangements or by use of portable equipment. Portable equipment may consist of: — hoses for steam blowing — hoses for heated water flushing — mallets (wooden, rubber or plastic hammers) — snow blowers — shovels. Guidance note: Mallets should be made of wood, not metal, to avoid damage to equipment, structures and paintwork.
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5.2.2 Steam or hot water shall be available where an area or equipment is intended to be de-iced manually and fixed heating is not provided. The location and number of the steam/hot water outlets and equipment shall be appropriate to the local layout and to the time scale in which the de-icing is required to be achieved.
5.2.3 De-icing equipment shall be located in areas where it is readily available and protected from icing and other adverse conditions. It is preferable to store de-icing equipment inside the ship. Where it is stored outside, the storage facilities shall be afforded anti-icing protection to ensure it is readily accessible.
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DNV GL AS 5.2.4 Steam- or water-based de-icing equipment shall be stored in heated spaces or containers that are kept 3 above freezing temperature in the design environmental condition to prevent hoses from freezing. n
5.2.5 Any equipment or systems scheduled for de-icing shall have all susceptible components (e.g., sensors, o i counters, limit switches, electric fittings) adequately protected from mechanical damage from manual de- t icing activities or water ingress from water/steam de-icing. c e S
6 Requirements to winterization 6
r e
6.1 Requirements to winterization t p
6.1.1 Winterization measures required by Table 6 shall fulfill the functional requirements, and shall be a considered for approval in each case, in addition to those given for the assignment of main class. The h C requirements relevant for Winterized Basic, Cold and Polar are indicated by an X in the corresponding column of the table. 6
t
Table 7 Requirements for winterized notation r a P Item Object Basic Cold Polar Rule
C200 Stability, watertight and weathertight integrity
C201 Cargo hatches, X X Functional requirements: service hatches and — Cargo hatches, service hatches and shell doors shall maintain shell doors weather-tightness under the design environmental conditions. — Cargo hatches and service hatches shall maintain their structural integrity and weather-tightness under the additional loading of snow and ice accumulation. Performance requirements: — Hatch/door seals and other components relevant for safety shall be made from materials suitable for the design temperature (td) specified in the class notation. Prescriptive requirements: — Snow and ice loading calculations in this requirement shall use the same snow and ice loads as those used for stability calculations in C203. — Where not addressed by Sec.4 for DAT or Sec.5 for PC ice class notation, materials shall be selected according to C1001, as appropriate.
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DNV GL AS Item Object Basic Cold Polar Rule 3
C202 Freeing ports and X X X Functional requirements: n
scuppers o — Freeing ports, scuppers and drains shall be capable of i being kept clear and open under the design environmental t c
conditions, and not be blocked due to snow, ice or freezing e
water. S
Prescriptive requirements: 6
— Where decks, access ways and muster areas are required r
to be kept ice-free, they shall be arranged with drains and e t scuppers that have anti-freezing protection. p
— Freeing ports shall be fitted with anti-icing protection. a
— Increasing the freeing port area by 30% is accepted as an h
alternative to heating (see Pt.3 Ch.12 Sec.10). C
— If a shutter is fitted on the freeing port, it shall be provided 6 with heating sufficient for maintaining its opening ability. t
— For ships 100 m or less in length, shutters shall not be fitted in r the freeing ports, as per the IS Code, Sec. 6.4.1. a P
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DNV GL AS Item Object Basic Cold Polar Rule 3
C203 Stability X X X Functional requirements: n o
— The ship shall retain adequate stability under conditions of i icing under the design environmental conditions. t c
Performance requirements: e S
— The ship shall satisfy the applicable intact and damage stability requirements under conditions of icing, taking into account the 6
additional weights due to ice accretion. r e
— Where there are no other damage stability requirements t
applicable for the ship, the ship shall comply with the damage p
stability requirements of IMO Res. A.1024(26). a h Prescriptive requirements: C — The icing weight distribution shall be calculated from the 6
following: t
— For decks, gangways, wheelhouse tops and other horizontal r surfaces, the values found in Table C203 a P — For projected lateral area of each side of the ship above the water plane; 7.5 kg/m2; — The projected lateral area of discontinuous surfaces of rail, sundry booms, spars (except masts) and rigging of ships having no sails and the projected lateral area of other small objects shall be computed by increasing the total projected area of continuous surfaces by 5% and the static moments of this area by 10%.
C300 Mechanical
C301 Anchor emergency X X X Functional requirements: release safety — The anchor emergency disconnect system on offshore service system (Offshore vessels with anchor handling capability shall be usable in the service vessels) design environmental conditions. Prescriptive requirements: — The anchor emergency disconnect system shall be provided anti-icing protection.
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DNV GL AS Item Object Basic Cold Polar Rule 3
C302 Anchoring X X X Functional requirements: n
arrangement o — The anchoring system shall be readily available in the design i environmental conditions when in or approaching coastal or t c
piloting waters. e
— The control systems shall not be susceptible to damage by de- S icing methods. 6
— Associated hydraulic systems shall function under the design environmental conditions r e Prescriptive requirements: t p
— The anchor windlass and windlass controls shall be provided a
anti-icing protection. h C
— The anchor chain may be de-iced manually.
— The hawse pipe shall be provided anti-icing protection or de- 6
icing protection with steam or hot water. t — Associated hydraulic systems shall comply with the r requirements in C805. a P
C303 Anchoring X X Functional requirements: arrangement — The crew shall be able to easily access and operate the anchor windlass in an environment that protects them from wind, water spray, ice and slippery conditions, without the need to remove ice from equipment or decks. Prescriptive requirements: — Anchor windlass, windlass controls and chain stopper shall be located inside a deckhouse, a semi-enclosure providing protection from water spray or inside a forecastle space.
C304 Anchoring X X Functional requirements: arrangement – — The anchor chain, chain stopper and anchor windlass shall be Material quality made from materials suitable for the design temperature (td). Prescriptive requirements: — The anchor chain material quality shall be chosen as follows:
if td > -20°C, then chain type K2 or K3
if td ≤ -20°C, then chain type K3 — For anchor windlass components fabricated from plate material, Class III steel grades shall be selected according to Sec.4 [2]. — For equipment or parts of equipment fabricated from forged or cast material, the impact test temperature and energy shall fulfil the requirements in C1001. — The anchor windlass shall have foundation bolts and shaft bearing holding bolts made from low temperature steel. Grey cast iron shall not be used in any load bearing parts.
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DNV GL AS Item Object Basic Cold Polar Rule 3
C305 Cranes X X Functional requirements: n o
— Cranes shall be able to withstand icing loads without i collapsing. t c
Performance requirements: e S
— Cranes shall be able to withstand icing loads used in C203 or in Pt.3 Ch.11 Sec.2 [4.5], whichever is greater. 6
— Cranes shall be able to withstand icing loads in the stowed and r e
operating conditions. t
— Crane foundations and supports shall be able to support an p
iced crane, using the loads specified above. a h
C306 Cranes X X Functional requirements: C
— Cranes that are required for essential safety functions (e.g., 6 crane used for launching the rescue boat) shall operate in the t
design environmental conditions. r a
Performance requirements P — The relevant cranes shall be made from materials suitable for the design temperature (td). Prescriptive requirements: — Equipment material shall be selected according to C1001, as appropriate. — The relevant cranes shall be fitted with anti-icing protection.
Guidance note:
1) Icing protection may either be active (e.g., heating) or passive (e.g., shielding).
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C307 Emergency towing X Functional requirements: arrangement — It shall be possible for tankers to make the emergency towing (Tankers) arrangement available on short notice during operation and sailing in the design environmental conditions. — The emergency towing arrangement shall operate under the design environmental conditions. Prescriptive requirements: — The emergency towing arrangement pre-rigged for immediate use shall have anti-icing protection. — The other emergency towing arrangement may be arranged with either anti-icing or de-icing protection.
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DNV GL AS Item Object Basic Cold Polar Rule 3
C308 Emergency towing X X Functional requirements: n
arrangement o — It shall be possible to make the emergency towing i (Tankers) t arrangement available on short notice during operation and c
sailing in the design environmental conditions. e
— The emergency towing arrangements shall operate under the S design environmental conditions. 6
Performance requirements: r e
— Components exposed to the low temperature shall be made t
from materials suitable for the design temperature (td) p
specified in the class notation. a h Prescriptive requirements: C — The emergency towing arrangement pre-rigged for immediate 6
use shall have passive anti-icing protection, that is, it shall be located in an enclosed space, semi-enclosure or under deck t r
space. a
— The other emergency towing arrangement may be arranged P with either anti-icing or de-icing protection. — Equipment material shall be selected according to C1001, as appropriate.
C309 Engine rooms – X X Functional requirements: Re#start from dead — It shall be possible to re-start the main machinery from ship a dead-ship condition after 30 minutes under the design environmental conditions. Performance requirements: — The machinery shall be arranged such that it can re-start and operate from a dead-ship condition after 30 minutes at an outside ambient temperature 20°C colder than the design temperature (td). 1) Guidance note:
1) Insulation may be necessary to ensure the machinery space maintains a sufficiently warm environment for re- starting the machinery after a dead-ship condition of 30 minutes. 2) Machinery may require air intake heating, cooling water heating and lube oil heating, depending on individual machinery specifications, to ensure it can re-start from a dead-ship condition after 30 minutes. 3) Water cooling lines and other machinery components that are subject to freezing should be located away from ship sides, where they will get coldest first.
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DNV GL AS Item Object Basic Cold Polar Rule 3
C310 Mooring X X X Functional requirements: n
arrangement o — Crew must be able to safely and efficiently remove snow and i ice accumulation from mooring winches and the surrounding t c
work area to make operating them safe in a reasonable time e
prior to mooring. S
Prescriptive requirements: 6
— De-icing system shall be provided in the vicinity of the r
mooring winches. e t
— Mooring winches shall be provided with covers to protect them p
from icing. a h C311 Mooring X X Functional requirements: C
arrangement — Mooring equipment exposed to the low temperature shall be 6
made from materials suitable for the design temperature (td) t
specified in the class notation. r
Prescriptive requirements: a P — Equipment material shall be selected according to C1001, as appropriate.Mooring winches shall have foundation bolts and shaft bearing holding bolts made from low temperature steel. Grey cast iron shall not be used in any load bearing parts. — Mooring wires shall be lubricated with low temperature wire rope dressing appropriate for the design temperature (td). Guidance note: Mooring equipment includes bollards, chocks, fairleads and roller pedestal (e.g. body and seat of fairleads and bollards; roller, pin, boss, bush, seat of deck stand rollers); body of sunken bits; chain wheel, gear wheel, shaft, foundation bolt, drum, warping head on an anchor windlass; and mooring wires.
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C400 Electrical
C401 Cables X X Functional requirements: — Electrical cabling shall maintain its required performance under the design environmental conditions. Performance requirements: — Electric cables exposed to the low temperature shall be made from material suitable for the design temperature (td). Prescriptive requirements: — Cables shall comply with acceptable impact and bending test standards. Impact and bending tests shall be conducted to at least 10°C colder than the design temperature (td). Guidance note: The latest revision of Canadian CSA standard C22.2 No. 0.3 for impact test at –35°C and bending test at –40°C, is an acceptable test standard.
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DNV GL AS Item Object Basic Cold Polar Rule 3
C402 Electric motor X X X Functional requirements: n
cooling o — Electric motors on open deck and necessary for safety or for i supporting main functions shall be capable of operation under t c
the design environmental conditions. e S
Performance requirements:
— Snow, ice and cold temperatures shall not adversely affect 6
the motor’s cooling system and thereby render the motor r
inoperable. e t
Prescriptive requirements: p a
— Electric motors in the category above shall be naturally cooled, h
without external fan. C
C403 Emergency electric X X Functional requirements: 6
power generation t — Emergency generators shall be operable under the design arrangement r
environmental conditions. a
Performance requirements: P — Emergency generator shall be able to start and operate with an outside ambient air temperature of 20°C below the design temperature (td). Prescriptive requirements: — Space heating, or heating of the generator itself, is required to ensure the emergency generator will start and operate under cold conditions, unless it can be shown that it will start and operate in temperatures 20°C below the design temperature (td).
C404 Emergency electric X Functional requirements: power generation — The emergency generator starting system shall be arranged so arrangement as to avoid a common mode failure, particularly one related to cold temperatures. Prescriptive requirements: — The emergency generator shall have two different, separate and independent starting systems.
Guidance note: The reference to different starting systems means that the two systems are based on different principles (e.g., one battery- powered and one air-powered), so as to avoid a common mode failure, particularly one related to cold temperatures.
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C405 Lighting X X X Functional requirements: — Deck lighting should be operable under the design environmental conditions. Prescriptive requirements: — Deck lights that do not generate sufficient heating to stay ice-free shall be fitted with additional heating to make them operational.
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DNV GL AS Item Object Basic Cold Polar Rule 3
C406 Main electric X X X Functional requirements: n
power generation o — Main electric generator capacity shall be sufficient to operate i arrangement t essential ship systems including anti-icing systems fitted to c
comply with the notation, under the design environmental e
condition, and a minimum of half of the de-icing systems fitted S to comply with the notation. 6 Prescriptive requirement r
— For calculation of required electric generator capacity (see Pt.4 e t Ch.8), the power requirements for the heating arrangements p
shall be included as follows: a
— 100% of electric power needed for anti-icing and anti- h C
freezing purposes fitted to comply with the notation
— 50% of electrical power needed for de-icing purposes fitted 6
to comply with the notation, or 100% of the power for the t single largest de-icing system consumer fitted to comply r with the notation, whichever is greatest. a P — Calculations shall be based upon power demands under the design environmental condition.
C407 Main electric X Functional requirements: power generation — Sufficient main electricity power generation shall be available arrangement such that a casualty to any one engine room (e.g., from fire or flooding) will not endanger the electric power generation capacity such that the ship is inoperable or crew survivability is put at risk. Prescriptive requirements: — Main electric power generators shall be located in separate spaces so that a casualty affecting one space (e.g., from fire or flooding) does not affect the other. — The ship shall have sufficient capacity to power essential systems for operation and survivability with the loss of any one engine space. — Auxiliary systems required to operate the main electric power generators shall also be separate and independent, to reduce common fault failures.
Guidance note: The redundancy requirement applies to electric power generation capacity, not to propulsion capacity.
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DNV GL AS Item Object Basic Cold Polar Rule 3
C408 Main switchboards X X X Functional requirements: n o
— Switchboards shall be arranged such that the crew can i adequately control and monitor the performance of installed t c
winterization systems. e S
Prescriptive requirements:
— Switchboard for winterization systems shall be arranged 6
as required for distribution switchboards. A wattmeter or r
ampere meter, indicating the total load shall be installed on e t the switchboard. Marking on the switchboard shall state the p
load on each circuit, as well as the total load. a h C409 Protective earthing X X X Functional requirements: C
arrangements — Electrical circuits for winterization features shall be arranged 6
such that an earthed circuit may be automatically isolated and t
disconnected without disabling the rest of the system. r
Prescriptive requirements: a P — All electrical circuits for winterization features shall have earth failure monitoring with automatic disconnection and alarm connected to the main alarm system.
C500 Safety
C501 Access, external X X X Functional requirements: — Personnel should be able to move safely up and down the accommodation ladder and gangway in the design environmental conditions, including freezing precipitation (snow and ice). Prescriptive requirements: — The ship shall have de-icing protection for the accommodation ladder and gangway.
C502 Access, internal X X X Functional requirements: — Personnel safety: The personnel should be able to move safely about weather deck areas of the ship under the design environmental conditions. — Stability: Snow and ice accumulation on weather decks shall be controlled within ship stability limits. Prescriptive requirements: — The ship shall have de-icing protection to remove snow and ice accumulation from all weather deck areas where there are no other requirements for anti-icing protection, to prevent loss of stability and to make them safe for personnel. — Some areas of weather decks may need to be ice-free, e.g. when those areas are important for emergency access (e.g., escape routes, muster areas, embarkation areas to survival craft); these areas shall be provided anti-icing protection.
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DNV GL AS Item Object Basic Cold Polar Rule 3
C503 Access, internal X X X Functional requirements: n o
— People shall not be at risk of injury, nor essential safety i equipment/structures at risk of damage, caused by falling ice t c
from elevated structures, including but not limited to cranes, e
derricks, masts and overhanging decks. S
Prescriptive requirements: 6
— Elevated structures shall be provided with de-icing or other r
measures adequate to prevent personnel injury or damage to e t essential safety equipment/structures from falling ice. p
Guidance note: a Possible measures to prevent injury or damage from falling ice h C
include: locating elevated structures to avoid or minimize icing;
locating work areas and equipment away from elevated structures 6 to eliminate or minimize risk from falling ice; design and/or t
locate elevated structures such that they can be easily de- r
iced; anti-icing measures (enclosure, shielded location, or heat a tracing); design measures to reduce icing potential (box vs. lattice P structure); dropped object protection to protect people, equipment and structures from falling ice.
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C504 Access, internal X X X Functional requirements: (Tankers) — Personnel shall have safe access to bow (for Tankers) under the design environmental conditions. Prescriptive requirements: — Safe access to tanker bow shall be provided by a gangway raised to a sufficient height to prevent passage being impeded by snow build-up on underlying surfaces. — The safe access to tanker bow shall be provided de-icing protection.
C505 Access, internal X X Functional requirements: (Tankers) — Personnel shall have safe access to bow (for Tankers) under the design environmental conditions. Prescriptive requirements: — The safe access to bow gangway shall either be provided anti- icing protection, or it shall be made of a grating with raised non-skid points that will give safe footing in the presence of minor sea spray icing.
Guidance note: Anti-icing protection may be in the form of an under-deck passageway, on deck trunk, or heat tracing.
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DNV GL AS Item Object Basic Cold Polar Rule 3
C506 Accommodation X X Functional requirements: n
heating system o — Accommodation spaces shall be kept at a temperature that i ensures the health and safety of personnel under the design t c
environmental conditions. e S
Prescriptive requirements:
— Accommodation heating shall be dimensioned to ensure 6
accommodation spaces can be kept at a temperature of at r
least +18°C under the design environmental conditions, with a e t recirculation rate of 50%. p
— The heating consumption shall be calculated based on an a
external ambient temperature of 20°C below the design h
temperature (td). C
C507 Accommodation X Functional requirements: 6
heating system t
— Accommodation spaces shall be kept at a temperature that r
ensures the health and safety of personnel under the design a
environmental conditions. P Prescriptive requirements: — The accommodation and spaces essential to ship operation shall have a redundant space heating design such that a failure of one heating source will not render the spaces without heating.
C508 Emergency X X X Functional requirements: shutdown system — Emergency shutdown (ESD) valves for gas tankers shall be ice-free and operational at all times in the design environmental conditions. Performance requirements: — ESD valves shall be arranged with anti-icing protection.
C509 Escape routes X X X Functional requirements: — Escape exits and escape doors must be able to readily open and close under the design environmental conditions, including freezing precipitation (snow and ice) and sea-spray icing. — Escape ways shall be safe to use in an emergency under the design environmental conditions. Prescriptive requirements: — Escape exits and doors shall have anti-icing protection. — Escape ways shall have anti-icing protection providing a minimum ice free width of 700 mm, enabling the use of at least one railing.
C510 Escape routes X Functional requirements: — Escape routes shall be dimensioned so as not to hinder passage for persons wearing suitable polar clothing, to comply with IMO Res. A.1024(26), Sec. 4.3.2.
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DNV GL AS Item Object Basic Cold Polar Rule 3
C511 Fire extinguishing X X X Functional requirements: n
equipment, mobile o — Miscellaneous fire-fighting equipment (including but not limited i to portable fire extinguishers, fire blankets, etc.) shall be t c
readily available under the design environmental conditions. e S
Prescriptive requirements:
— Portable fire extinguishers in open or unheated spaces shall be 6
rated for operation at the design temperature (td). r e
— Miscellaneous fire-fighting equipment shall be located in areas t
where it is readily available and protected from icing and other p
adverse conditions. The storage facilities shall be afforded a
anti-icing protection to ensure it is readily accessible. h C
C512 Fire-fighting X X X Functional requirements:
systems 6 — Fire-fighting systems shall be readily available under the t
design environmental conditions. r
Performance requirements: a P — Fire-fighting equipment (including but not limited to hydrants, hoses, nozzles and monitors) shall not be blocked by external icing or by internal freezing under the design environmental conditions. — Fire mains and fire-fighting system piping shall not be blocked by internal freezing under the design environmental conditions. Prescriptive requirements: — Fire-fighting equipment shall have anti-icing and anti-freezing protection. — Fire mains and fire-fighting system piping shall have anti- freezing protection. — Anti-freezing protection of the fire mains and fire-fighting system piping may be achieved by locating them in a heated passageway, by providing them with heat tracing, or by arranging them as a dry, self-draining system. Where piping is arranged as a dry, self-draining system, drains shall be located at the lowest points in the system, and the piping layout shall ensure all water will drain to them without being trapped in U- bends, low points or dead-ends.
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DNV GL AS Item Object Basic Cold Polar Rule 3
C513 Fire-fighting X X Functional requirements: n
systems o — Fire-fighting systems equipment shall be readily available i under the design environmental conditions. t c
Performance requirements: e S
— The choice of fire-fighting systems and extinguishing agents shall be appropriate for the design environmental conditions, 6
taking into account low temperature effects on extinguishing r
agents. e t
— Isolation valves shall be fitted and readily available under the p
design environmental conditions. a h Prescriptive requirements: C — Fire extinguishing agents (foams, powders, gases) shall be 6
rated for operation at the design temperature (td). t
— Isolation valves shall have anti-icing protection. r
— The isolation valve spindle shall be accessible from weather a
deck. P
C514 Fire and gas X X X Functional requirements: detection and alarm — Fire and gas detection and alarm systems shall function under systems the design environmental condition and shall not be obstructed by ice or snow. Performance requirements: — Fire and gas detection sensors and dampers located outside shall be provided anti-icing protection. — Fire and gas detection sensors located outside or in unheated spaces shall be rated for operation at the design temperature (td).
C515 Guard rails X X X Functional requirements: — Personnel safety: Icing of railings shall be controlled so that railings can maintain their safety function. Prescriptive requirements: — Railings that are important as hand-holds (stairs, escape ways) shall have anti-icing protection. — Railings that function only as barriers, but are not intended as hand-holds, can be arranged for de-icing
C516 Helicopter safety X X X Functional requirements: arrangements — The helicopter winching area and helicopter deck, where fitted, shall be safe for personnel and helicopter operations under the design environmental conditions. Prescriptive requirements: — De-icing arrangements shall be provided for the helicopter winching area and helicopter deck, where fitted.
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DNV GL AS Item Object Basic Cold Polar Rule 3
C517 Helicopter safety X X Functional requirements: n
arrangements o — For standby vessels, the helicopter winching area and i (Standby Vessels) t helicopter deck shall be readily available and safe for c
personnel and helicopter operations under the design e
environmental conditions. S
Prescriptive requirements: 6
— For standby vessels, de-icing arrangements shall be provided r
for the helicopter winching zone and helicopter deck, where e t fitted, capable of making the zone/deck available within one p
hour under the design environmental conditions. a h C518 Immersion suits X X Functional requirements: C — Immersion suits shall be provided and afford the wearer the 6
appropriate level of protection for the design environmental t
condition. r
Prescriptive requirements: a P — The insulated type of immersion suits shall be provided for all personnel.
C519 Life raft X X X Functional requirements: arrangements — The crew shall be able to launch/lower/release the rafts safely in the design environmental condition. — The hydrostatic release mechanism for the life rafts shall be able to function safely in the design environmental condition and is protected from icing build-up. Performance requirements: — Life rafts shall not be damaged in stowage by ambient air temperatures down to -30°C or 20°C colder than the design temperature (td), whichever is colder. — Life rafts shall remain operational in ambient air temperatures down to -15°C or the design temperature (td), whichever is colder. Prescriptive requirements: — Life rafts and their release and lowering systems shall be provided with anti-icing protection. — Life rafts shall be type approved and satisfy relevant criteria given in the LSA Code. — Life rafts shall be tested in accordance with IMO Res. MSC/81(70) as amended and relevant for the equipment in question.
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DNV GL AS Item Object Basic Cold Polar Rule 3
C520 Lifeboat X X X Functional requirements: n
arrangements o — The crew shall be able to launch/lower/release and operate the i lifeboats safely in the design environmental condition. t c
Performance requirements: e S
— Lifeboats shall not be damaged in stowage by ambient air temperatures down to −30°C or 20°C colder than the design 6
temperature (td), whichever is colder. r e
— Lifeboats shall remain operational in ambient air temperatures t
down to -15°C or the design temperature (td), whichever is p
colder. a
— Lifeboat engines shall be arranged to ensure they will start h
readily when required under the design environmental C
conditions. 6 — Lifeboat engine fuel oil shall be suitable for operation under t
the design environmental conditions. r a
Prescriptive requirements: P — Lifeboats shall be type approved and satisfy relevant criteria given in the LSA Code. — The lifeboats shall be tested to be undamaged in stowage by ambient air temperatures down to -30°C or 20°C colder than the design temperature (td), whichever is colder. — The lifeboats shall be tested to operate in ambient air temperatures down to -15°C or the design temperature (td), whichever is colder. — Lifeboats and their securing and launching systems shall be fitted with anti-icing protection. — Lifeboat engines shall be fitted with a heater. — Free-fall lifeboats are not acceptable for ships that have also an ice class notation according to Sec.2 or Sec.5, unless the lifeboats have alternative means for lowering with their full complement onboard.
C521 Lifeboat X X Functional requirements: arrangements — The crew shall be able to launch/lower/release and operate the lifeboats safely in the design environmental condition. Performance requirements: — Lifeboat davits/securing & launching systems shall be made from materials suitable for the design temperature (td). — The lifeboat shall protect occupants from extreme cold. Prescriptive requirements: — Anti-icing for lifeboats and lifeboat davits/securing & launching systems shall be arranged as passive protection. — Materials for davit/securing & launching system components shall be selected according to C1001, as appropriate. — The lifeboat shall be outfitted with internal heating.
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DNV GL AS Item Object Basic Cold Polar Rule 3
C522 Rescue boat X X X Functional requirements: n
arrangements o — The crew shall be able to immediately access, launch, and i operate the rescue boat under the design environmental t c
conditions. e S
Prescriptive requirements:
— The rescue boat and its deployment and recovery equipment 6
shall be fitted with anti-icing protection. r e
C523 Rescue boat X X Functional requirements: t arrangements p
— The rescue boat and deployment equipment shall function a
under the design environmental conditions. h C
Performance requirements: 6
— Rescue boat davits and related components shall be made from materials suitable for the design temperature (t ). t
d r
— The rescue boat engine shall be arranged to ensure it will start a
readily when required under the design temperature (td). P Prescriptive requirements: — Materials for rescue boat davits and related components shall be selected according to C1001, as appropriate. — Rescue boat engine fuel oil shall be suitable for operation under the design temperature (td). — The rescue boat engine shall be fitted with a heater.
C524 Machinery spaces X X Functional requirements: heating system — Spaces containing equipment necessary to perform main functions and safety functions shall be kept at a temperature that ensures safe operation of the essential equipment. Performance requirements: — Engineering spaces shall be kept at a temperature of at least +5°C. Prescriptive requirements: — Engineering spaces shall be provided with heating as required. Spaces that may need heating include, but are not limited to: steering gear room, emergency fire pump room, CO2 rooms, foam rooms, battery rooms, and bow thruster rooms. — The heating consumption shall be calculated based on an external ambient temperature of 20°C below the design temperature (td).
C525 Muster station X Functional requirements: and survival craft — Muster station, embarkation area and access to lifeboats and arrangements life rafts must be immediately available and safe to use in an emergency under the design environmental conditions. Prescriptive requirement — Muster station, embarkation area, and access to the lifeboats and life rafts shall be fitted with anti-icing protection.
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DNV GL AS Item Object Basic Cold Polar Rule 3
C526 Muster station X X Functional requirements: n
and survival craft o — Muster station, embarkation area and access to lifeboats and i arrangements t life rafts shall be immediately available and safe to use in an c
emergency under the design environmental conditions. e S
Prescriptive requirements:
— The muster station shall be located inside the superstructure, 6
close to the lifeboats. r e
— The embarkation area and access to the lifeboats and life rafts t
shall be fitted with anti-icing protection. p a C527 Muster station X Functional requirements: h and survival craft — The muster station, embarkation area and lifeboat access shall C arrangements be dimensioned for people wearing suitable polar clothing. 6
C528 Other safety X Functional requirements: t r arrangements — The ship shall carry survival equipment suitable for the polar a
environment. P Prescriptive requirements: — The ship shall carry personal survival kits and group survival kits as described in IMO Res. A.1024(26), Sec. 11.3 and 11.4. — Sufficient personal and group survival kits shall be carried to cover at least 110% of the persons onboard the ship. — Personal survival kits shall be stored in dedicated lockers in the muster station. — Group survival kits shall be stored so that they may be easily retrieved and deployed in an emergency situation. Containers shall be located adjacent to the survival craft and be designed so that they may be easily moved over the ice and be floatable.
C529 Personal life-saving X X X Functional requirements: appliances — Lifesaving equipment shall be stored so that the equipment is not harmed by the cold climate, and so that it is immediately available. — The bridge life-buoy shall be kept ice-free and immediately ready to launch. Prescriptive requirements: — Storage facilities for lifesaving equipment shall be fitted with anti-icing protection. — The bridge life-buoy shall be provided anti-icing protection and be arranged such that it is immediately deployable by the crew.
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DNV GL AS Item Object Basic Cold Polar Rule 3
C530 Pressure relief X X X Functional requirements: n
valves o — Pressure relief valves shall function properly in the design i environmental condition and shall not be impaired by ice or t c
snow. e S
Prescriptive requirements:
— Pressure relief valves and vent heats associated with any 6
pressure relief discharge line shall be provided anti-icing r
protection. e t
— Associated piping arrangements shall be self-draining. The p
drains shall be located at the lowest points in the system, and a
the piping layout shall ensure all liquids will drain to them h
without being trapped in U-bends, low points or dead-ends. C
C531 Pressure relief X X Functional requirements: 6
valves t
— Pressure relief valves shall function properly in the design r
environmental condition. a P Performance requirements: — Pressure relief valves shall be made from materials suitable for the design temperature (td). Prescriptive requirements: — Materials for pressure relief valves shall be selected according to C1001, as appropriate.
C532 Protective gear X X X Functional requirements: — Appropriate personal protective equipment shall be provided that protects the crew while working outdoors in the design environmental conditions, as well as from falling ice and slippery decks.
C533 Stairs X X X Functional requirements: — Personnel should be able to move safely up and down stairs in the design environmental conditions. Prescriptive requirements: — External stairs and their top railing shall have anti-icing protection to make them safe for personnel. — Stairs that are not part of escape ways or not in regular use may be considered, on a case-by-case basis, for de-icing protection.
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DNV GL AS Item Object Basic Cold Polar Rule 3
C534 Ventilation systems X X X Functional requirements: n o
— Ventilation openings for spaces containing equipment i necessary to perform main functions and safety functions shall t c
be operational at all times under the design environmental e
conditions. S
Prescriptive requirements: 6
— Ventilation openings shall be provided with anti-icing r
protection. e t
Guidance note: p
For Winterized(Cold) and Winterized(Polar), passive protection a (e.g., protective cowlings or vestibules that prevent snow, ice or sea h C
spray ingress) is preferred to active protection (e.g., heat tracing). 6
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C535 Ventilation systems X X Functional requirements: r a
— Ventilation openings for spaces containing equipment P necessary to perform main functions and safety functions shall be operational at all times under the design environmental conditions. Prescriptive requirements: — Ventilation openings shall be equipped with an alarm to indicate blockage.
C536 Working X X Functional requirements: environment — The deck/manifold watch shall be provided with a shelter that keeps them warm and protects them from wind, cold and precipitation while also allowing them to perform their essential duties. Prescriptive requirements: — A heated watchman's shelter shall be arranged at the gangway or at a location covering both the gangway and the loading manifold. — The shelter shall be capable of maintaining an inside temperature of at least +5°C. The heating consumption requirements shall be calculated based on an external ambient temperature of 20°C colder than the design temperature (td).
C600 Hull and structure
C601 Helicopter deck X X X Functional requirements: — The helicopter deck, where fitted, shall maintain its structural integrity under the additional loading of snow and ice accumulation. Prescriptive requirements: — The structural integrity of the helicopter deck design shall be confirmed by calculations. Snow and ice loading calculations in this requirement shall use the same snow and ice loads as those used for stability calculations in C203.
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DNV GL AS Item Object Basic Cold Polar Rule 3
C602 Helicopter deck X X Functional requirements: n o
— An elevated helicopter deck, where fitted, shall be made from i materials suitable for the material design temperature (t ) t d c
specified in the class notation. e S
Prescriptive requirements:
— Materials for an elevated helicopter deck shall be selected 6
according to C1001, as appropriate. r e
Guidance note: t
Material requirements for the main supporting structure for the p helicopter deck sub-structure are covered by Sec.4 for ships with a the DAT notation or by Sec.5 for ships with a PC ice class notation. h C
Material requirements for helicopter decks that are part of the hull
structure are covered by Sec.4 for ships with the DAT notation or 6
by Sec.5 for ships with a PC ice class notation. t
Aluminium helidecks are suitable to all levels of winterization. r a
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C700 Navigation
C701 Navigation bridge X X Functional requirements: — The navigating officers shall be able to navigate the ship without being exposed to the outside environment. Prescriptive requirements: — The navigation bridge wings shall be fully enclosed. — The ship’s side shall be visible from the bridge wings without opening the bridge windows. — Additional conning positions (e.g., aloft conning position for use in ice navigation, aft-facing conning positions), if fitted, shall also be fully enclosed.
C702 Navigation lights X X X Functional requirements: — Navigation lighting shall be operable under the design environmental conditions. Prescriptive requirements: — Navigation lights must either generate sufficient heat to keep the light fixture ice-free under the design environmental conditions or be provided with anti-icing protection. — Sidelight screens shall be provided with anti-icing protection to ensure the required lighting sector is not obstructed by snow or ice accumulated on the screen. — Navigation lights shall be tested for proper operation as per C703.
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DNV GL AS Item Object Basic Cold Polar Rule 3
C703 Navigation systems X X X Functional requirements: n o
— Navigation equipment required by SOLAS Ch.V and additional i navigation equipment fitted to fulfil requirements of other t c
class notations assigned to the ship (e.g., DYNPOS) shall e
be available and operable under the design environmental S condition. 6 Prescriptive requirements: r
— Relevant navigation equipment located outside or in unheated e t compartments shall be tested for proper operation at a p
temperature of -25°C or the design temperature (td) specified a
in the notation, whichever is colder. h
Guidance note: C
Test procedures found in IEC 60945 may be adopted, using the test 6 temperature specified in the prescriptive requirement, above. t r ---e-n-d---of---g-u-i-d-a-n-c-e---n-o-t-e--- a P C704 Navigation systems X X X Functional requirements: — Positioning sensors (e.g., anemometers) fitted to fulfil equipment requirements of other class notations assigned to the ship (e.g., DYNPOS) shall operate under the design environmental conditions. Prescriptive requirements: — Such positioning sensors shall be either of a type not adversely affected by icing, or they shall have anti-icing protection.
C705 Navigation systems X X X Functional requirements: — Antennae to navigation equipment required by SOLAS Ch.V and additional navigation equipment fitted to fulfil requirements of other class notations assigned to the ship (e.g., DYNPOS) shall function properly in the design environmental conditions. Performance requirements: — Relevant antennae shall be protected from snow and ice accumulation that interferes with signal performance. — The movement of rotating antennae (e.g., radar) shall not be inhibited by snow or ice. Prescriptive requirements: — Relevant antennae shall be provided anti-icing protection. Antennae may be heated or placed in heated domes. Whip type antennae do not require heating arrangements. Where relevant equipment requires antennae that cannot be heated, then provision shall be made for easy access for manual de- icing. — Dome and rod antennae shall be located such that heavy snowfall will not bury the antennae. — Pedestals for rotating antennae (e.g., radar) shall have anti- icing to ensure rotation of the antenna is not inhibited by snow or ice under the design environmental conditions.
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DNV GL AS Item Object Basic Cold Polar Rule 3
C706 Navigation systems, X X X Functional requirements: n
other o — Windows to the navigation bridge shall be ice and frost free i under the design environmental conditions. t c
Prescriptive requirements: e S
— All windows within the required field of vision shall be provided with appropriate heating arrangements. Windows shall comply 6
with ISO 3434 and ISO 8863. The heating capacity shall be r
designed for an outside temperature of -20°C or less. e t
— Windows shall be fitted with window wipers that will operate p
and remain ice-free under the design environmental a
conditions. h
— Where fitted, window washers shall be protected from freezing C
under the design environmental conditions. 6
Guidance note: t Reference is made to ISO 17899 for marine electric window wipers. r a When a field of vision larger than defined by SOLAS is required by a P class notation, e.g. NAUT(AW), this should be taken into account.
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DNV GL AS Item Object Basic Cold Polar Rule 3
C707 Searchlights X X Functional requirements: n o
— The ship shall have ice searchlights to aid in detection of ice i during navigation in darkness. t c
— The ice searchlights shall function in the design environmental e
conditions. S
Performance requirements: 6
— The luminous intensity of the focused position of the ice r e
searchlight shall be sufficient to provide an illumination of 5.6 t
lux at a distance of at least 1000 meters from the foremost p
part of the ship or twice the ship’s stop distance at full speed, a
whichever is greater, with an atmospheric transmission of 0.8. h C
Prescriptive requirements: 6
— The ship shall have at least one ice searchlight, which shall in so far as possible be located in the forepart of the ship, t r
and shall be of sufficient luminous intensity to meet the a
performance requirement. P — Ice searchlights shall be located and mounted so that the wheelhouse visibility is not obstructed in snow (i.e., the lights should be positioned as far forward as practicable and should not be mounted above the viewing level of the navigation bridge). — The lights shall be operable remotely from the wheelhouse. — The lights shall include functionality for focusing the cone of light from the wheelhouse. — To function in the design environmental conditions, ice searchlights shall be fitted with the following: — means for securing the starter function at low temperatures; — anti-condensation function of the searchlight housing; — anti-icing protection of the rotation mechanism, if the light is rotatable.
C708 Sound signal X X X Functional requirements: appliances — The ship’s whistle shall operate under the design environmental condition. Prescriptive requirements: — The whistle shall be fitted with anti-icing to ensure it will operate under the design environmental conditions. — Steam or air lines to the whistle, where fitted, shall be protected from freezing at the design temperature (td).
C800 Piping
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DNV GL AS Item Object Basic Cold Polar Rule 3
C801 Air pipes and vent X X X Functional requirements: n
heads o — Air pipes and vent heads to tanks shall be able to maintain i proper tank ventilation under the design environmental t c
condition. e S
Prescriptive requirements:
— Air pipes and vent heads for all tanks shall be provided with 6
anti-icing protection. r e
C802 Ballast tanks, fresh X X X Functional requirements: t water tanks and p
— The ship shall be able to safely ballast, de-ballast and shift a other tanks ballast in the design environmental condition. h
— Freezing of ballast water shall be controlled such that it does C
not cause any harm to the tank or equipment, and does not 6
interfere with ballasting, de-ballasting or shifting of ballast. t
— For fresh water tanks and other tanks intended for holding r
liquids subject to freezing under the design environmental a conditions, freezing of tank contents shall be controlled such P that it does not cause any harm to the tank or equipment. Prescriptive requirements: — The ship shall have an arrangement to prevent the surface of ballast tanks, fresh water tanks and other relevant tanks from freezing over under the design environmental conditions. — GRP piping and other systems and structures in the tanks that may be damaged by freezing and falling ice shall be suitably protected. — Tank level gauging shall function under the design operational conditions. — Where arrangements to prevent freezing of ballast water are required under other sections of these Rules, the more stringent design environmental conditions shall be used in calculations. — In determining the need for anti-freezing protection of fresh water and other relevant tanks, the freezing point of the intended tank contents shall be used in tank calculations.
Guidance note: An arrangement to prevent freezing of the ballast water need not be provided for ballast tanks located fully below the water line or lower ice water line (LIWL), whichever is lower, or where heat balance calculations show the tank will not freeze under the design environmental conditions. An arrangement to prevent freezing of the ballast water need not be provided for ballast tanks located fully below the water line or lower ice water line (LIWL), whichever is lower, or where heat balance calculations show the tank will not freeze under the design environmental conditions. It is assumed that, before pumping of tanks is commenced, proper functioning of level gauging arrangements is verified and air pipes are checked for possible blockage by ice.
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DNV GL AS Item Object Basic Cold Polar Rule 3
C803 Compressed air X X X Functional requirements: n
systems o — The supply of compressed air to essential systems shall be i provided with air drying sufficient to prevent condensation t c
under the design environmental conditions. e S
Prescriptive requirements:
— Compressed air shall be provided with air drying sufficient 6
to lower the dew point to not warmer than -25°C or 15°C r e colder than the design temperature (td) at the actual pressure, t whichever is colder. p
C804 Fuel oil system X X Functional requirements: a h
— Transfer of fuel oil shall be possible under the design C environmental conditions. 6
Prescriptive requirements: t r
— Fuel oil heating system shall be sufficiently dimensioned a
to enable transfer of fuel under the design environmental P conditions. — Transfer lines for heavy fuel oil exposed to the low temperature environment shall have heat tracing.
C805 Hydraulic power X X Functional requirements: systems — Hydraulic systems serving main functions shall operate under the design environmental conditions. Prescriptive requirements: — Hydraulic fluid shall either be of a type that maintains an acceptable viscosity, or the hydraulic system shall have heating/circulation arrangements to keep fluids at an appropriate temperature to ensure the operability of the essential systems they serve. — For calculation of heating need and choice of hydraulic oil for systems located outdoors or in non-heated spaces, a temperature of 20°C below the design temperature (td) shall be used.
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DNV GL AS Item Object Basic Cold Polar Rule 3
C806 Piping X X X Functional requirements: n o
— Piping shall not be damaged by internal freezing under the i design environmental conditions. t c
Performance requirements: e S
— Piping on open decks and in non-heated spaces that carry liquids susceptible to freezing under the design environmental 6
conditions shall be provided anti-freezing protection. r e
Prescriptive requirements: t p — Anti-freezing protection may be achieved by locating piping in a
a heated passageway or trunk, by providing them with heat h
tracing, or by arranging them as a dry, self-draining system. C Where piping is arranged as a dry, self-draining system, drains 6
shall be located at the lowest points in the system, and the
piping layout shall ensure all liquids will drain to them without t r being trapped in U-bends, low points or dead-ends. a
C807 Pollution prevention X Functional requirements: P arrangements — The ship shall be designed to reduce the possibility of polluting the Polar environment from oil pollution. Prescriptive requirements: — The ship shall have the class notation Clean. — For oil tankers, the accidental oil outflow index: OM shall not exceed 0.01 calculated in accordance with revised MARPOL Annex I, Reg. 23. — Non-toxic and biodegradable oil shall be used for stern tube and controllable-pitch propeller systems.
C808 Sea chests X X X Functional requirements: — Cooling water systems for machinery that are essential for the propulsion and safety of the ship, including sea chests inlets, shall be designed to ensure supply of cooling water under the design environmental conditions. Performance requirements: — The sea cooling water inlet and discharge for main and auxiliary engines shall be arranged so that blockage of strums and strainers by ice is prevented. Prescriptive requirements: — A ship with an ice class notation shall comply with the respective requirements in Pt.3 Ch.11 Sec.1 [7.3], Sec.2 [16.2] or Sec.5 [10], as appropriate for their ice class. — A ship without an ice class notation shall comply with the requirements in eitherSec.1 [7.3], Sec.2 [16.2] or Sec.5 [12.10].
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DNV GL AS Item Object Basic Cold Polar Rule 3
C809 Ventilation systems X X X Functional requirements: n
for hazardous cargo o — Venting system for cargo tanks shall be operational under i areas t design environmental conditions c
Prescriptive requirements: e S
— Cargo tank venting systems shall be fitted with anti-icing protection (pressure/vacuum valves, pressure/vacuum 6
breakers, safety valves and flame arresters). r e
— Cargo tank pressure/vacuum breakers shall be fitted with anti- t
freezing protection (e.g., glycol or heating). p a C900 Telecommunications h C
C901 External X X X Functional requirements:
communication 6
— External communications systems required by SOLAS Ch.V systems and additional communications equipment fitted to fulfil t r requirements of other class notations assigned to the ship shall a
function properly in the design environmental conditions. P Performance requirements: — Relevant antennae shall be protected from snow and ice accumulation that interferes with signal performance. — The movement of rotating antennae shall not be inhibited by snow or ice. Prescriptive requirements: — Relevant antennae shall be provided anti-icing protection. Antennae may be heated or placed in heated domes to protect them from snow and ice accumulation. Whip type antennae do not require heating arrangements. Where relevant equipment requires antennae that cannot be heated, then provision shall be made for easy access for manual de-icing — Dome and rod antennae shall be located such that heavy snowfall will not bury the antennae. — Pedestals for rotating antennae shall have anti-icing to ensure rotation of the antenna is not inhibited by snow or ice under the design environmental conditions.
C902 External X X X Functional requirements: communication — Communication equipment required by SOLAS Ch.V systems and additional communications equipment fitted to fulfil requirements of other class notations assigned to the ship shall function properly in the design environmental conditions. Prescriptive requirements: — Relevant communication equipment located outside or in unheated compartments shall be tested and certified to operate properly down to -25°C or the design temperature (td) specified in the notation, whichever is colder.
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DNV GL AS Item Object Basic Cold Polar Rule 3
C903 GMDSS - EPIRB X X X Functional requirements: n o
— The EPIRB shall be kept ice-free and immediately ready to i launch. t c
Prescriptive requirements: e S
— The EPIRB shall be provided anti-icing protection and be arranged such that it is able to float free to the surface without 6
crew intervention. Alternatively, the EPIRB shall be arranged r
with de-icing protection and an additional EPIRB mounted e t inside the wheelhouse, ready for immediate deployment by the p
crew. a h C904 GMDSS – Global X Functional requirements: C
maritime distress — Suitable communication equipment shall be fitted for high and safety system 6 latitude operations. t
Prescriptive requirements: r a
— The ship shall meet SOLAS Ch.IV communication equipment P requirements for Area A4.
C1000 Multidiscipline
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DNV GL AS Item Object Basic Cold Polar Rule 3
C1001 Equipment material X X Functional requirements: n o
— All equipment exposed to the low temperature and being i important for ship operations shall be made from materials t c
suitable for the material design temperature (td) specified in e
the class notation. S
Prescriptive requirements: 6
— For equipment or parts of equipment fabricated from plate r
material, steel grades shall be selected as follows, according to e t Sec.4 [2]. p
Class III: a h — lifeboat and rescue boat davits C
— anchoring and mooring equipment 6
— emergency towing arrangement (tankers). t
Class II: r a
— cargo securing devices P — mast with derrick having load greater than 3 tons — other equipment or components not specified as Class I or Class III, unless upgraded or downgraded on a case-by- case basis due to special considerations of loading rate, level and type of stress, stress concentrations and load transfer points and/or consequences of failure. Class I — natural vents — cargo hatches, service hatches, access hatches. — For pipes, the pipe material shall be selected in the same manner as for plate material above or according to Pt.2 Ch.2 Sec.4 [4]. — For equipment or parts of equipment fabricated from forged or cast material, the impact test temperature and energy shall fulfil the requirements in Table C1001.
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DNV GL AS Item Object Basic Cold Polar Rule 3
C1002 Winterization X X X Functional requirements: n
arrangements o — Installations made in connection with optional class notations i – Installations t and which are essential for safety shall function properly in associated with c
the design environmental conditions. Arrangements that are e optional class
essential for safety include those required for a ship to perform S
notation the primary safety-related functions of its type. 6 Prescriptive requirements: r
— Rescue arrangements in a ship with class notation Standby e t vessel shall be provided with anti-icing protection. p
— Fire-fighting arrangements in a ship with the class notation a
Fire fighter shall be provided with anti-icing and anti-freezing h
protection. C
6
t r a P
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DNV GL AS SECTION 4 DESIGN AMBIENT TEMPERATURE - DAT 4
n o
1 General i t c 1.1 Introduction e S
The additional class notation DAT sets requirements to materials in ships of any type intended to operate 6 for longer periods in areas with low air temperatures, i.e. regular service during winter to Arctic or Antarctic waters. r e t p
1.2 Scope a h The scope for the additional class notation DAT provides requirements to steel grades, based on the material C class, for a given design ambient air temperature for ships of regular service during winter to Arctic or
Antarctic waters. 6
t r
1.3 Application a P The additional class notation DAT applies to ships complying with the rules in this section. The additional class notation DAT(t), where the qualifier t is indicating the temperature applied as basis for the approval. For further details, please see Table 1.
1.4 Class notations Ships built in compliance with the requirements as specified in Table 1 will be assigned the additional notation as follows:
Table 1 Additional class notation related to cold climate
Class Notation Qualifier Purpose Application
DAT t Design ambient air temperature suitable for Mandatory: regular service during winter to polar waters, where t No denotes the lowest design ambient temperature in °C Design requirements: [2]
FiS requirements: Pt.7 Ch.1 Sec.2, Pt.7 Ch.1 Sec.3 and Pt.7 Ch.1 Sec.4
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DNV GL AS 4 1.5 Documentation requirements n
For general requirements to documentation, including definition of the Info codes, see Pt.1 Ch.3 Sec.2. o i
For a full definition of the documentation types, see Pt.1 Ch.3 Sec.3. t c
Documentation shall be submitted as required by Sec.3 Table 3. e S Table 2 Documentation requirements 6
Object Documentation type Additional description Info r e t Design ambient air temperature suitable for Technical information Z100 – Specification AP p
regular service during winter, td. a
AP = For approval h C
6
t 1.6 Definitions r a P 1.6.1 Terminology and definitions
Table 3 Terminology and definitions
Terms Definition
external structure the plating with stiffening to an inwards distance of 0.6 metre from the shell plating, exposed decks and exposed sides and ends of superstructure and deckhouses
design temperature the reference temperature used as a criterion for the selection of steel grades. The design temperature for external structures is defined as the lowest mean daily average air temperature in the area of operation. This temperature is considered to be comparable with the lowest monthly mean temperature in the area of operation −2°C. If operation is restricted to «summer» navigation the lowest monthly mean temperature comparison may only be applied to the warmer half of the month in question. Temperature terms definition see Figure 1.
Guidance note: The design temperatures are defined by the user when signing the class contract. The extreme design temperature may be set to about 20°C below the lowest mean daily average air temperature, or the material design temperature, if information for the relevant trade area is not available.
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mean daily average the statistical mean average temperature for a specific calendar day, based on a number of temperature years of observations (= MDAT).
monthly mean average the average of the mean daily temperature for the month in question (= MAMDAT) temperature
lowest mean daily average the lowest value on the annual mean daily temperature curve for the area in question. For temperature seasonally restricted service the lowest value within the time of operation applies
lowest monthly mean is the monthly mean temperature for the coldest month of the year. average temperature
fore ship substructure includes the bow and the bow intermediate ice belt area, i.e. B and BIi, see Figure 1 in Sec.5.
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DNV GL AS Terms Definition 4
MDHT Mean* Daily High (or maximum) Temperature n o MDAT Mean* Daily Average Temperature i t c MDLT Mean* Daily Low (or minimum) Temperature e S
MAMDHT Monthly Average** of MDHT 6
MAMDAT Monthly Average** of MDAT r
MAMDLT Monthly Average** of MDLT e t
MEHT Monthly Extreme High Temperature (ever recorded) p a
MELT Monthly Extreme Low Temperature (ever recorded) h C 1) Mean: Statistical mean over observation period (at least 20 years). 6
2) Average: Average during one day and night. t r
a P
MEHT MAMDHT MDHT
MDAT MDLT MAMDAT
MAMDLT
LOWEST MEAN DAILY TEMPERATURE MELT
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
Figure 1 Commonly used definitions of temperatures
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DNV GL AS 4 2 Material selection n o i 2.1 Structural categories t c e 2.1.1 S Structural strength members or areas are classified in 4 different classes for the purpose of selecting required 6
material grades. The relevant members are classified as specified in Table 4. The classes are generally described as follows: r e
Class IV: t — Strakes in the strength deck and shell plating amidships intended as crack arrestors. p a
— Highly stressed elements in way of longitudinal strength member discontinuities. h C
Class III: 6
— Plating chiefly contributing to the longitudinal strength. t
— Fore ship substructure. r
— Appendages of importance for the main functions of the ship, e.g. stern frames, rudder horns, rudder, a
propeller nozzles and shaft bracket. P — Aft ship substructures in ships equipped with podded propulsors and azimuth thrusters, and intended for continuous operation astern. — Foundations and main supporting structures for heavy machinery and equipment. — Crane pedestal and main supporting structure — Main supporting structure for helideck sub-structure — Frames for windlasses, emergency towing and chain stopper, when equipment is welded to foundation or deck (i.e. not applicable when equipment is bolted to foundation or deck).
Guidance note: Main supporting structures are primary load bearing members such as plates, girders, web frames/bulkheads and pillars.
---e-n-d---of---g-u-i-d-a-n-c-e---n-o-t-e--- Class II: — Structures contributing to longitudinal and/or transverse hull girder strength in general. — Gutter bars of oil spill coamings attached to hull. — Structures for subdivisions. — Structures for cargo, bunkers and ballast containment. — Internal longitudinal members (stiffeners, girders) on plating exposed to external low temperatures where class III and IV is required. — Deck house or superstructure exposed to longitudinal stresses within 0.6L amidship. Class I: — Local members in general unless upgraded due to special considerations of loading rate, level and type of stress, stress concentrations and load transfer points and/or consequences of failure. — Deckhouse or superstructure in general. — Cargo hatch covers.
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DNV GL AS Table 4 Material classes of strength members in general. 4
Structural member Within 0.4 L amidships Elsewhere n o i
SECONDARY: t
A1. Longitudinal bulkhead strakes, other than that c belonging to the Primary category e S
A2. Deck plating exposed to weather, other than that II II
belonging to the Primary or Special category 6 Side plating
A3. r
A4. Transverse bulkhead plating e t
PRIMARY: p B1. Bottom plating, including keel plate a B2. Strength deck plating, excluding that belonging to h C
the Special category 7) B3. B3. Continuous longitudinal members above III II 6
strength deck, excluding hatch coamings t
B4. B4. Uppermost strake in longitudinal bulkhead r B5. Vertical strake (hatch side girder) and uppermost a sloped strake in top wing tank P
SPECIAL: C1. Sheer strake at strength deck 1), 2) C2. Stringer plate in strength deck 1), 2) C3. Deck strake at longitudinal bulkhead, excluding deck plating in way of inner-skin bulkhead of double-hull ships 1) C4. Strength deck plating at outboard corners of cargo hatch openings in container carriers and other 3) ships with similar hatch opening configurations 6) C5. Strength deck plating at corners of cargo hatch IV III openings in bulk carriers, ore carriers combination carriers and other ships with similar hatch opening configurations 4) C7. Bilge strakes 1),8),9) C8. Longitudinal hatch coamings of length greater than 0.15L5) C9. End brackets and deck house transition of longitudinal cargo hatch coamings5)
1) Single strakes required to be of class IV or of grade VL E/EH and within 0.4 L amidships shall have breadths not less than (800 + 5 L)mm, and need not to be taken greater than 1 800 mm, unless limited by the geometry of the ship’s design. 2) Not to be less than grade VL E/EH within 0.4 L amidships in ships with length exceeding 250 m. 3) Min. class IV within cargo region. 4) Class IV within 0.6 L amidships and class III within rest of cargo region. 5) Not to be less than grade VL D/DH. 6) May be class II outside 0.6 L amidships. 7) May be class II if relevant midship section modulus as built is not less than 1.5 times the rule midship section modulus, and the excess is not credited in local strength calculations. 8) Not to be less than grade VL D/DH within 0.4 L amidships in ships with length exceeding 250 m. 9) May be of class III in ships with double bottom over the full breadth and length less than 150 m.
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DNV GL AS 2.1.2 The material class requirement may be reduced by one class for: 4 — Laterally loaded plating having a thickness exceeding 1.25 times the requirement according to design n formulae. o i
— Laterally loaded stiffeners and girders having section modulus exceeding 1.5 times the requirement t
according to design formulae. c e S 2.2 Selection of steel grades 6
2.2.1 Plating materials for various structural categories as defined in [2.1]of exposed members above the r e ballast waterline of ships with class notation DAT (t) shall not be of lower grades than obtained from Figure t
2 using the specified design temperature. p Plating materials of non-exposed members shall not be of lower grade than obtained according to Pt.3 Ch.3 a Sec.1 Table 9. h C
6
t r a P
Figure 2 Required steel grades
Guidance note: When the structural category is known the material grade can be selected based on the design temperature and plate thickness. E.g. if a 30 mm plate should be applied for structural category III with a design temperature of –30oC, grade E or EH need to be applied. Boundary lines form part of the lower grade.
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DNV GL AS 2.2.2 Forged or cast materials in structural members subject to lower design temperatures than −10°C 4 according to [2.1] shall fulfil requirements given in Sec.3 Table 6 item C1001. n o i t c e S
6
r e t p a h C
6
t r a P
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DNV GL AS SECTION 5 POLAR CLASS - PC 5
n o
1 General i t c 1.1 Introduction e S
The additional class notation PC sets requirements for ships constructed of steel, intended for navigation in 6 ice-infested polar waters. The requirements for the additional class notation PC are in general equivalent to the IACS Unified Requirements for Polar Ships (UR 11 and UR 13). r e t p
1.2 Scope a h The scope for the additional class notation PC consider hull structure, main propulsion, steering gear, C emergency and essential auxiliary systems essential for the safety of the ship and the survivability of the crew. 6
These rules do not consider aspects related to the operation of on-board equipment in cold climate. It is t r
recommended that ships intended to operate in cold climate environments for longer periods comply with the a
requirements as given in Sec.3. P
1.3 Application The additional class notation PC applies to steel ships complying with the requirements in this section, as listed in Table 2. If the hull and machinery are constructed such as to comply with the requirements of different polar classes, then the ship shall be assigned the lower of these classes in the classification certificate. Compliance of the hull or machinery with the requirements of a higher polar class is also to be indicated in the classification certificate or an appendix thereto. Ships designed for ice breaking for the purpose of escort and ice management, and which are assigned a polar class notation PC(1) to PC(7), may be given the additional class notation Icebreaker, as given in Pt.1 Ch.3 Sec.2.
1.4 Class notations
1.4.1 Ships built in compliance with the requirements as specified in Table 1 will be assigned the additional notation as follows:
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DNV GL AS Table 1 Additional class notation related to cold climate 5
Class Notation Qualifier Purpose Application n o i
1 Ships intended for navigation Year-round operation in all Polar waters t
in ice-infested polar waters c e PC
2 Ships intended for navigation Year-round operation in moderate multi-year ice S in ice-infested polar waters conditions 6
Mandatory:
3 Ships intended for navigation Year-round operation in second-year ice which r
No in ice-infested polar waters may include multi-year ice inclusions e t
4 Ships intended for navigation Year-round operation in thick first-year ice which p Design requirements: in ice-infested polar waters may include old ice inclusions a [3] to [13] h
5 Ships intended for navigation Year-round operation in medium first-year ice C
in ice-infested polar waters which may include old ice inclusions 6
FiS requirements:
6 Ships intended for navigation Summer/autumn operation in medium first-year t
Pt.7 Ch.1 Sec.2, Pt.7 Ch.1 r in ice-infested polar waters ice which may include old ice inclusions Sec.3 and Pt.7 Ch.1 Sec.4 a 7 Ships intended for navigation Summer/autumn operation in thin first-year ice P in ice-infested polar waters which may include old ice inclusions
1.4.2 The Polar Class (PC) notations and descriptions are given in Table 2. It is the responsibility of the owner to select an appropriate Polar Class. The descriptions in Table 2 are intended to guide owners, designers and administrations in selecting an appropriate Polar Class to match the requirements for the ship with its intended voyage or service.
1.4.3 The Polar Class notation is used throughout the IACS Unified Requirements for Polar Ships to convey the differences between classes with respect to operational capability and strength.
Table 2 Polar class descriptions
Polar Class Ice Description (based on WMO Sea Ice Nomenclature)
PC(1) Year-round operation in all Polar waters
PC(2) Year-round operation in moderate multi-year ice conditions
PC(3) Year-round operation in second-year ice which may include multi-year ice inclusions.
PC(4) Year-round operation in thick first-year ice which may include old ice inclusions
PC(5) Year-round operation in medium first-year ice which may include old ice inclusions
PC(6) Summer/autumn operation in medium first-year ice which may include old ice inclusions
PC(7) Summer/autumn operation in thin first-year ice which may include old ice inclusions
2 Documentation
2.1 Documentation requirements
2.1.2 For general requirements to documentation, including definition of the Info codes, see Pt.1 Ch.3 Sec.2. For a full definition of the documentation types, see Pt.1 Ch.3 Sec.3.
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DNV GL AS Documentation shall be submitted as required by Table 3. 5
Table 3 Documentation requirements n o i
Object Documentation type Additional description Info t c
Z100 - Specification Main propulsion FI e
machinery, steering, S
emergency and 6
essential auxiliaries: r Technical Description, location, e
information protection against t
freezing, ice and p snow, and operational a capability in intended h C
environment. 6
Propulsion torque C040 - Design analysis Ice load response AP t
and thrust simulation. r
transmission a
arrangement P
Propulsion C040 - Design analysis Ice load response AP thruster torque simulation. transmission arrangement
Z100 - Specification Details of the FI environmental conditions and the External required ice class environment for the machinery, if different from ship’s ice class.
AP = For approval; FI = For information
3 Design principles
3.1 Design temperature for structure and equipment Applicable design temperature for the operation of the ship in ice infested waters shall be given in the documentation submitted for approval. Guidance note: The design temperature reflects the lowest mean daily average air temperature in the intended area of operation. An extreme air temperature about 20°C below this may be tolerable to the structures and equipment from a material point of view. For calculations where the most extreme temperature over the day is relevant, the air temperature can be set 20°C lower than the design temperature in the notation. If no specification of the design temperature has been given, the values -35ºC for notations PC(1) to PC(5) and -25ºC for notations PC(6) and PC(7) will be considered.
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DNV GL AS 5 3.2 Hull areas n o
3.2.1 The hull of all polar class ships is divided into areas reflecting the magnitude of the loads that are i t
expected to act upon them. In the longitudinal direction, there are four regions: Bow, Bow Intermediate, c
Midbody and Stern. The Bow Intermediate, Midbody and Stern regions are further divided in the vertical e
direction into the Bottom, Lower and Ice belt regions. The extent of each hull area is illustrated in Figure 1. S
6
r e t p a h C
6
t r a P
Figure 1 Hull area extents
3.2.2 The upper ice waterline (UIWL) and lower ice waterline (LIWL) are as defined in Sec.1.
3.2.3 Figure 1 notwithstanding, at no time is the boundary between the Bow and Bow Intermediate regions to be forward of the intersection point of the line of the stem and the ship baseline.
3.2.4 Figure 1 notwithstanding, the aft boundary of the Bow region need not be more than 0.45 L aft of the forward perpendicular (F.P.).
3.2.5 The boundary between the bottom and lower regions shall be taken at the point where the shell is inclined 7° from horizontal.
3.2.6 If a ship is intended to operate astern in ice regions, the aft section of the ship shall be designed using the Bow and Bow Intermediate hull area requirements as given in [4.7].
3.3 System design
3.3.1 Systems, subject to damage by freezing, shall be drainable.
3.3.2 Ships classed PC(1), to PC(5) inclusive shall have means provided to ensure sufficient ship operation in the case of propeller damage including CP-mechanism, i.e. pitch control mechanism.
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DNV GL AS Sufficient ship operation means that the ship should be able to reach safe harbour (safe location) where 5 repair can be undertaken in case of propeller damage. This may be achieved either by a temporary repair at sea, or by towing assuming assistance is available (condition for approval). n o i
3.3.3 Means shall be provided to free a stuck propeller by turning backwards. This means that a plant t intended for unidirectional rotation must be equipped at least with a sufficient turning gear that is capable of c turning the propeller in reverse direction. e S
3.3.4 Propulsion power 6
Guidance note: r
For PC no explicit power requirement exists. However, according to “IMO guidelines for Ships operating in Polar waters” ships shall e t
have sufficient propulsion power and sufficient manoeuvrability for operation in intended area. p
Engine power may be selected according to current rule practice. We advise to use model test alternative. a h ---e-n-d---of---g-u-i-d-a-n-c-e---n-o-t-e--- C
6
4 Design ice loads – hull t r a
4.1 General P
4.1.1 For ships of all Polar Classes, a glancing impact on the bow is the design scenario for determining the scantlings required to resist ice loads.
4.1.2 The design ice load is characterized by an average pressure Pavg uniformly distributed over a rectangular load patch of height b and width w.
4.1.3 Within the Bow area of all polar classes, and within the Bow Intermediate Ice belt area of polar classes PC(6) and PC(7), the ice load parameters are functions of the actual bow shape. To determine the ice load parameters Pavg, b and w, it is required to calculate the following ice load characteristics for sub-regions of the bow area; shape coefficient fai, total glancing impact force Fi, line load Qi and pressure Pi.
4.1.4 In other ice-strengthened areas, the ice load parameters Pavg, bNonBow and wNonBow are determined independently of the hull shape and based on a fixed load patch aspect ratio, AR = 3.6.
4.1.5 Design ice forces, calculated according to [4], are in general considered valid for bow forms where the buttock angle, γ, is less than 80 degrees and the frame angle, β, is positive and more than 10 degrees, see Figure 2. Design ice forces for other bow forms and for bow forms that are otherwise considered to be non icebreaking will be specially considered.
4.1.6 Ship structures that are not directly subjected to ice loads may still experience inertial loads of stowed cargo and equipment resulting from ship/ice interaction, as given in [4.1.7] – [4.1.9], which shall be considered as alternative to the design accelerations given in Pt.3 Ch.4 Sec.3.
4.1.7 Maximum longitudinal impact acceleration, in m/s2, at any point along the hull girder, to be taken as:
4.1.8 Combined vertical impact acceleration, in m/s2, at any point along the hull girder, to be taken as:
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DNV GL AS 5
n o
i t c = 1.3 at F.P. Fx e = 0.2 at midships S
= 0.4 at A.P. 6
= 1.3 at A.P. for ships conducting ice breaking astern. r e
Intermediate values to be interpolated linearly. t p 2 4.1.9 Combined transverse impact acceleration, in m/s , at any point along hull girder, to be taken as: a
h C
6
t
r a
Fx = 1.5 at F.P. P = 0.25 at midships = 0.5 at A.P. = 1.5 at A.P. for ships conducting ice breaking astern.
Intermediate values to be interpolated linearly. where:
φ = Maximum friction angle between steel and ice, normally taken as 10°, in degrees. γ = Bow stem angle at waterline, in degrees. Δtk = Displacement at UIWL, in ktonnes. H = Vertical distance from UIWL to the point being considered, in m. FIB = Vertical impact force, defined in [6.2]. FBow = As defined in [4.5.1].
4.2 Glancing impact load characteristics
4.2.1 The parameters defining the glancing impact load characteristics are reflected in the class factors listed in Table 4.
Table 4 Class factors
Polar Crushing failure Flexural failure Load patch Displacement Longitudinal strength Class class factor (CF ) dimensions C Class factor (CFF) Class factor Class factor (CFL) Class factor (CFD) (CFDIS)
PC(1) 17.69 68.60 2.01 250 7.46
PC(2) 9.89 46.80 1.75 210 5.46
PC(3) 6.06 21.17 1.53 180 4.17
PC(4) 4.50 13.48 1.42 130 3.15
PC(5) 3.10 9.00 1.31 70 2.50
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DNV GL AS PC(6) 2.40 5.49 1.17 40 2.37 5
PC(7) 1.80 4.06 1.11 22 1.81 n o i t c
4.3 Bow area e S
4.3.1 In the Bow area, the force F, line load Q, pressure P and load patch aspect ratio AR associated with the 6 glancing impact load scenario are functions of the hull angles measured at the upper ice waterline UIWL. The influence of the hull angles is captured through calculation of a bow shape coefficient fa. The hull angles are r e defined in Figure 2. t p
a h C
6
t r a P
Figure 2 Definition of hull angles
β’ = Normal frame angle at upper ice waterline, in degrees. α = Upper ice waterline angle, in degrees. γ = Buttock angle at upper ice waterline (angle of buttock line measured from horizontal), in degrees. tan(β) = tan(α)/tan(γ) tan(β’) = tan(β) cos(α).
4.3.2 The waterline length of the bow region is generally to be divided into 4 sub-regions of equal length. The force F, line load Q, pressure P and load patch aspect ratio AR shall be calculated with respect to the mid-length position of each sub-region (each maximum of F, Q and P shall be used in the calculation of the ice load parameters Pavg, b and w).
4.3.3 The bow area load characteristics are determined as follows: a) Shape coefficient, fai, shall be taken as
fa=i minimum (fai,1; fai,2; fai,3) where:
2 0.5 fai,1 = (0.097 - 0.68 (x/Lwl - 0.15) )·αi / (β’i)
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DNV GL AS fa = 0.64 i,2 1.2·CFF / (sin (β’i)·CFC·Δtk ) 5
fai,3 = 0.60 n o i
i = Sub-region considered t c
Lwl = Ship length as defined in Pt.3 Ch.1, measured on the upper ice waterline (UIWL), in m e S
x = Distance from the forward perpendicular (FE) to station under consideration, in m 6
α = Waterline angle [deg], see Figure 2 r
= Normal frame angle [deg], see Figure 2 e β’ t p Δ = Ship displacement, in ktonnes, at UIWL, not to be taken less than 5 ktonnes
tk a h CFC = Crushing failure class factor from Table 4 C
CFF = Flexural failure class factor from Table 4 6
b) Force, in MN: t r
0.64 a
Fi= fai ·CFC·Δtk P where:
i = Sub-region considered
fai = Shape coefficient of sub-region i
CFF = Crushing Failure Class Factor from Table 4
Δtk = Ship displacement, in ktonnes, at UIWL, not to be taken less than 5 ktonnes c) Load patch aspect ratio, AR:
AR=i 7.46·sin (β’i) ≥ 1.3 where:
i = Sub-region considered β’ = Normal frame angle of sub-region i, in degrees d) Line load, in MN/m:
0.61 0.35 Qi= Fi ·CFD / ARi where:
i = Sub-region considered
Fi = Force of sub-region i, in MN
CFD = Load Patch Dimensions Class Factor from Table 4
ARi = Load patch aspect ratio of sub-region i e) Pressure, in MPa:
0.22 2 0.3 Pi= Fi ·CFD ·ARi where:
i = Sub-region considered
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DNV GL AS F = Force of sub-region i, in MN
i 5
CFD = Load Patch Dimensions Class Factor from Table 4 n o AR = Load patch aspect ratio of sub-region i i
i t c e S
4.4 Hull areas other than the bow 6
4.4.1 In the hull areas other than the bow, the force FNonBow and line load QNonBow used in the determination r of the load patch dimensions (b , w ) and design pressure P are determined as follows: e NonBow NonBow avg t a) Force, in MN: p a h FNonBow = 0.36·CFC·DF C
6
where: t
CFC = Crushing force class factor from Table 4 r a
CFD = Load patch dimensions class factor from Table 4 P
DF = Ship displacement factor 0.64 = Δtk if Δtk ≤ CFDIS
0.64 = CFDIS + 0.10 (Δtk - CFDIS) if Δtk > CFDIS
Δtk = Ship displacement, in ktonnes at UIWL, not to be taken less than 10 ktonnes
CFDIS = Displacement class factor from Table 4 b) Line Load, in MN/m:
0.61 QNonBow = 0.639·FNonBow ·CFD
where
FNonBow = Force from (a), in MN
CFD = Load patch dimensions class factor from Table 4.
4.5 Design load patch
4.5.1 In the Bow area for all PC-classes, and the Bow Intermediate Ice belt area for ships with class notation PC(6) and PC(7), the design load patch, in m, has dimensions of width, wBow, and height, bBow, defined as follows: wBow = FBow / QBow bBow = QBow / PBow where:
FBow = Maximum force Fi in the Bow area, ref. [4.3.3] b), in MN. QBow = Maximum line load Qi in the Bow area, ref. [4.3.3] d), in MN/m. PBow = Maximum pressure Pi in the Bow area, ref. [4.3.3] e), in MPa.
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DNV GL AS 4.5.2 In hull areas other than those covered by [4.5.1], the design load patch, in m, has dimensions of 5 width, wNonBow, and height, bNonBow, defined as follows: n o wNonBow = FNonBow / QNonBow i t b = wNonBow / 3.6
NonBow c e
where: S
6
FNonBow = Ice force as given by [4.4.1], in MN. QNonBow = Ice line load as given by [4.4.1], in MN/m. r e t p
4.6 Pressure within the design load patch a h
4.6.1 The average pressure within a design load patch, in MPa, is determined as follows: C
6 P = F / (b·w) avg t r where: a P
F = FBow or FNonBow as appropriate for the hull area under consideration, in MN. b = bBow or bNonBow as appropriate for the hull area under consideration, in m. w = wBow or wNonBow as appropriate for the hull area under consideration, in m.
4.6.2 Areas of higher, concentrated pressure exist within the load patch. In general, smaller areas have higher local pressures. Accordingly, the peak pressure factors listed in Table 5 are used to account for the pressure concentration on localized structural members.
4.7 Hull area factors
4.7.1 Associated with each hull area is an area factor that reflects the relative magnitude of the load expected in that area. The area factor (AF) for each hull area is listed in Table 6.
4.7.2 In the event that a structural member spans across the boundary of a hull area, the largest hull area factor shall be used in the scantling determination of the member.
4.7.3 Due to their increased manoeuvrability, ships having propulsion arrangements with azimuting thruster(s) or “podded” propellers shall have specially considered Stern Ice belt (Si) and Stern Lower (Sl) hull area factors.
4.7.4 For ships intended to operate astern in ice regions, the area factor as for the bow shall be used for all structure within the stern ice belt area, and the bow intermediate lower and bottom area factors increased by 10% shall be used for the stern lower and bottom areas, appendages included. In addition stern intermediate areas shall be defined for the aft ship as for the fore ship. The area factor (AF) for ships intended to operate astern is listed in Table 7.
Table 5 Peak pressure factors
Structural Member Peak Pressure Factor (PPFi)
Transversely-framed PPFp = (1.8 - s) ≥ 1.2 Plating Longitudinally-framed PPFp = (2.2 - 1.2·s) ≥ 1.5
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DNV GL AS Structural Member Peak Pressure Factor (PPF ) i 5
1)
Frames in transverse With load distributing stringers PPFt = (1.6 - s) ≥ 1.0 n o
Framing systems 1) i With no load distributing dtringers PPF = (1.8 - s) ≥ 1.2
t t c Load carrying stringers PPF = 1, if S ≥ 0.5·w
s w e
Side and bottom longitudinals PPFs = 2.0 - 2.0·Sw / w, if Sw < (0.5·w) S
Web frames 6
s = frame or longitudinal spacing [m] r e
where Sw = web frame spacing [m] t
w = ice load patch width [m] p a
1) In order that the reduced PPFt value may be used, the load distributing stringer shall be located at or close to the h
middle of span of the transverse frames, to have web height not less than the 80% of the transverse frames, and to C
have net web thickness not less than the net web thickness of the transverse frames. 6
t
Table 6 Hull area factors (AF) r a P Polar Class Hull Area Area PC(1) PC(2) PC(3) PC(4) PC(5) PC(6) PC(7)
Bow (B) All B 1.00 1.00 1.00 1.00 1.00 1.00 1.00
Ice belt BIi 0.90 0.85 0.85 0.80 0.80 1.00* 1.00* Bow intermediate Lower BI 0.70 0.65 0.65 0.60 0.55 0.55 0.50 (BI) l
Bottom BIb 0.55 0.50 0.45 0.40 0.35 0.30 0.25
Ice belt Mi 0.70 0.65 0.55 0.55 0.50 0.45 0.45
Midbody (M) Lower Ml 0.50 0.45 0.40 0.35 0.30 0.25 0.25
Bottom Mb 0.30 0.30 0.25 ** ** ** **
Ice belt Si 0.75 0.70 0.65 0.60 0.50 0.40 0.35
Stern (S) Lower Sl 0.45 0.40 0.35 0.30 0.25 0.25 0.25
Bottom Sb 0.35 0.30 0.30 0.25 0.15 ** **
Notes:
* = See [4.1.3]. ** = Indicates that strengthening for ice loads is not necessary.
Table 7 Hull area factors (AF) for ships intended to operate astern
Polar Class Hull Area Area PC(1) PC(2) PC(3) PC(4) PC(5) PC(6) PC(7)
Bow (B) All B 1.00 1.00 1.00 1.00 1.00 1.00 1.00
Bow intermediate Icebelt BIi 0.90 0.85 0.85 0.80 0.80 1.00* 1.00* (BI) Lower BIl 0.70 0.65 0.65 0.60 0.55 0.55 0.50
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DNV GL AS Polar Class 5
Hull Area Area
PC(1) PC(2) PC(3) PC(4) PC(5) PC(6) PC(7) n o Bottom BI 0.55 0.50 0.45 0.40 0.35 0.30 0.25 i
b t c Icebelt M 0.70 0.65 0.55 0.55 0.50 0.45 0.45
i e S
Midbody (M) Lower Ml 0.50 0.45 0.40 0.35 0.30 0.25 0.25 6
Bottom Mb 0.30 0.30 0.25 ** ** ** ** r
Icebelt SIi 0.90 0.85 0.85 0.80 0.80 1.00* 1.00* e t
Stern Intermediate p Lower SIl 0.70 0.65 0.65 0.60 0.55 0.55 0.50
(SI)*** a
Bottom SIb 0.55 0.50 0.45 0.40 0.35 0.30 0.25 h C Icebelt Si 1.00 1.00 1.00 1.00 1.00 1.00 1.00 6
Stern (S) Lower Sl 0.77 0.72 0.72 0.66 0.61 0.61 0.55 t r
Bottom Sb 0.61 0.55 0.50 0.44 0.39 0.33 0.28 a P Notes:
* = See [4.1.3]. ** = Indicates that strengthening for ice loads is not necessary. ***= The Stern intermediate region, if any, for ships intended to operate astern is to be defied as the region forward of Stern region to section 0.04 L forward of WL angle = 0 degrees at UIWL (ref. definition of bow intermediate in Figure 1).
4.8 Ice compression load amidships
4.8.1 All ships shall withstand line loads acting simultaneously in the horizontal plane at the water level on both sides of the hull. These loads are assumed to arise when a ship is trapped between moving ice floes. The parameter for ice thickness hice is to be in agreement with the Society and will be stated in the “Appendix to the classification certificate”.
4.8.2 The design line loads, in kN/m, shall be taken as:
for vertical side shells
hice = Average ice thickness expected for the ship to encounter, in m. βf = Angle of outboard flare at the water level, in degrees.
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DNV GL AS 5 5 Local strength requirements n o i 5.1 Shell plate requirements t c e
5.1.1 The required minimum shell plate thickness, in mm, is given by: S
6
t = tnet + ts r where: e t p tnet = Plate thickness required to resist ice loads according to [5.1.2], in mm. a ts = Corrosion and abrasion allowance according to [10.1], in mm. h C
5.1.2 The thickness of shell plating required to resist the design ice load, t , depends on the orientation of
net 6 the framing. t r
In the case of transversely-framed plating (Ω ≥ 70 deg), including all bottom plating, i.e. plating in hull areas a BIb, Mb and Sb, the net thickness, in mm, is given by: P
In the case of longitudinally-framed plating (Ω ≤ 20°), when b ≥ s, the net thickness, in mm, is given by:
In the case of longitudinally-framed plating (Ω ≤ 20°), when b < s, the net thickness, in mm, is given by:
In the case of obliquely-framed plating (70° > Ω > 20°), linear interpolation shall be used. where:
Ω = Smallest angle between the chord of the waterline and the line of the first level framing as illustrated in Figure 3, in degrees. s = Transverse frame spacing in transversely-framed ships or longitudinal frame spacing in longitudinally-framed ships, in m. AF = Hull area factor from Table 6/Table 7. PPFp = Peak pressure factor from Table 5. Pavg = Average patch pressure as given in [4.6], in MPa.
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DNV GL AS b = Height of design load patch, in m, where b ≤ (ℓ – s/4) in the case of transversely framed plating. 5
ℓ = Distance between frame supports, i.e. equal to the frame span as given in [5.2.5], but not
reduced for any fitted end brackets, in m. When a load-distributing stringer is fitted, the length l n
need not be taken larger than the distance from the stringer to the most distant frame support. o i t c e S
6
r e t p a h C
6
t r a P
Figure 3 Shell framing angle Ω
5.2 Framing general
5.2.1 Framing members of Polar class ships shall be designed to withstand the ice loads defined in [4].
5.2.2 The term “framing member” refers to transverse and longitudinal local frames, load-carrying stringers and web frames in the areas of the hull exposed to ice pressure, see Figure 1.
5.2.3 The strength of a framing member is dependent upon the fixity that is provided at its supports. Fixity can be assumed where framing members are either continuous through the support or attached to a supporting section with a connection bracket. In other cases, simple support should be assumed unless the connection can be demonstrated to provide significant rotational restraint. Fixity shall be ensured at the support of any framing which terminates within an ice-strengthened area.
5.2.4 The details of framing member intersection with other framing members, including plated structures, as well as the details for securing the ends of framing members at supporting sections, shall be in accordance with [5.9] and Pt.3 Ch.3 Sec.5 [3], Pt.3 Ch.3 Sec.5 [4], Pt.3 Ch.3 Sec.6 [1]and Pt.3 Ch.6 Sec.7 as applicable.
5.2.5 The design span of framing members shall generally be determined according to Pt.3 Ch.3 Sec.6 [1]. However, the span length is only to be reduced in accordance with Pt.3 Ch.3 Sec.6 [1] provided the end 0.5 brackets fitted are flanged or the edge length in mm is equal to or less than 600 tbn /ReH . tbn = Net thickness of bracket, in mm.
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DNV GL AS 5.2.6 Load-carrying stringers and web frames are generally to be of symmetrical cross-section. When the 5 flange is arranged to be unsymmetrical, an effective tripping support shall be provided at the middle of each span length. n o i
5.2.7 When calculating the section modulus and shear area of a framing member, net thickness of the web, t flange (if fitted) and of the attached shell plating shall be used. The shear area of a framing member may c include that material contained over the full depth of the member, i.e. web area including portion of flange, if e S fitted, but excluding attached shell plating. 6
2
5.2.8 The actual net effective shear area of a framing member, in cm , is given by: r e t p a
h C
where: 6
t h = Height of stiffener, in mm, see Figure 4. r twn = Net web thickness, in mm. a P = tw - ts tw = As built web thickness, in mm, see Figure 4. ts = Corrosion addition, in mm, as given in [10.1.3], to be subtracted from the web and flange thickness. φw = Smallest angle between shell plate and stiffener web, in degrees, measured at the midspan of the stiffener, see Figure 4. The angle ϕw may be taken as 90 degrees provided the smallest angle is not less than 75 degrees.
Figure 4 Stiffener geometry
5.2.9 When the cross-sectional area of the attached plate flange, Apn, exceeds the cross-sectional area of the 3 local frame, (Afn+hw· tw/100), the actual net effective plastic section modulus, in cm , is given by:
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DNV GL AS 5
n o i
t c h, twn, and φw are as given in [5.2.7] and s as given in [5.1.2]. e
2 S Apn = Net cross-sectional area of the fitted shell plate, (tpn·s·10), in cm .
= Fitted net shell plate thickness, in mm (shall comply with t as required by [5.1.2]). 6 tpn net hw = Height of local frame web, in mm, see Figure 4. r = Net cross-sectional area of local frame flange, in cm2. e Afn t
hfc = Height of local frame measured to centre of the flange area, in mm, see Figure 4. p bw = Distance from mid thickness plane of local frame web to the centre of the flange area, in mm, see a
Figure 4. h C
When the cross-sectional area of the local frame exceeds the cross-sectional area of the attached plate 6 flange, the plastic neutral axis is located a distance above the attached shell plate, in mm, given by: t
r a P
and the net effective plastic section modulus, in cm3, is given by:
5.2.10 In the case of oblique framing arrangement 70° > Ω > 20°, where Ω is defined as given in [5.1.2], linear interpolation shall be used.
5.3 Framing – transversely framed side structures and bottom structures
5.3.1 The local frames in transversely-framed side structures and in bottom structures (i.e. hull areas BIb, Mb and Sb) shall be dimensioned such that the combined effects of shear and bending do not exceed the plastic strength of the member. The plastic strength is defined by the magnitude of patch load that causes the development of a plastic hinge mechanism.
5.3.2 The actual net effective shear area of the frame, in cm2, as defined in [5.2.8], shall comply with the following condition: Aw ≥ At, where:
where:
LL = Length of loaded portion of span. = Lesser of a and b, in m. a = Frame span as defined in [5.2.5], in m.
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DNV GL AS b = Height of design ice load patch as given in [4.5], in m. 5 s = Transverse frame spacing, in m.
AF = Hull Area Factor fromTable 6/Table 7. n
= Peak Pressure Factor from Table 5. o PPFt i Pavg = Average pressure within load patch as given in [4.6], in MPa. t c e 5.3.3 The actual net effective plastic section modulus of the plate/stiffener combination, in cm3, as defined in S [5.2.9], shall comply with the following condition: Zp ≥ Zpt, where Zpt shall be the greater calculated on the 6
basis of two load conditions: a) ice load acting at the midspan of the transverse frame, and b) the ice load acting near a support. The A1 parameter reflects the two conditions: r e
t p a h C
6
where: t r
AF, PPFt, Pavg, LL, b, s, and a are as given in [5.3.2]. a P Y = 1 - 0.5·(LL / a) A1 = maximum of:
2 0.5 A1A = 1 / (1 + j / 2 + kw·j / 2·[(1 - a1 ) - 1])
0.7 A1B = (1 – 1 / (2·a1·Y)) / (0.275 + 1.44·kz )
j = 1 for framing with one simple support outside the ice-strengthened areas
= 2 for framing without any simple supports
a1 = At / Aw
2 At = Minimum shear area of transverse frame as given in [5.3.2], in cm .
2 Aw = Effective net shear area of transverse frame (calculated according to [5.2.8], in cm .
kw = 1 / (1 + 2·Afn / Aw) with Afn as given in [5.2.9]
kz = zp / Zp in general
0.0 when the frame is arranged with end bracket 3 zp = Sum of the individual plastic section modulus of flange and shell plate as fitted, in cm .
2 2 = (bf·tfn / 4 + beff·tpn / 4) / 1000
bf = Flange breadth, in mm, see Figure 4
tfn = Net flange thickness, in mm
= tf – ts (ts as given in [5.2.8])
tf = As-built flange thickness, in mm, see Figure 4
tpn = The fitted net shell plate thickness, in mm (not to be less than tnet as given in [5.1.2])
beff = Effective width of shell plate flange, in mm
= 500 s 3 Zp = Net effective plastic section modulus of transverse frame (calculated according to [5.2.9]), in cm .
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DNV GL AS 5.3.4 The scantlings of the frame shall meet the structural stability requirements of [5.6]. 5
n o
5.4 Framing – side longitudinals (longitudinally framed ships) i t
5.4.1 Side longitudinals shall be dimensioned such that the combined effects of shear and bending do not c exceed the plastic strength of the member. The plastic strength is defined by the magnitude of midspan load e S that causes the development of a plastic collapse mechanism. 6
2
5.4.2 The actual net effective shear area of the frame, in cm , as defined in [5.2.8], shall comply with the r following condition: e t p Aw ≥ AL a h where: C
6
t r a P
where:
AF = Hull Area Factor from Table 6/Table 7. PPFs = Peak Pressure Factor from Table 5. Pavg = Average pressure within load patch as given in [4.6], in MPa. b1 = ko·b2 in m ko = 1 - 0.3 / b’ b’ = b / s b = Height of design ice load patch as given by [4.5.1]/[4.5.2], in m. s = Spacing of longitudinal frames, in m. b2 = b (1 - 0.25·b’) if b’ < 2 = s if b’ ≥ 2 a = Longitudinal design span as given in [5.2.5], in m.
5.4.3 The actual net effective plastic section modulus of the plate/stiffener combination, in cm3, as defined in [5.2.9], shall comply with the following condition:
ZP ≥ ZPL where:
where:
AF, PPFs, Pavg, b1, and a are as given in [5.4.2].
2 0.5 A4 = 1 / (2 + kwℓ·[(1 - a4 ) - 1]) a4 = AL / Aw A = Minimum shear area for longitudinal as given in [5.4.2], in cm2. L 2 Aw = Net effective shear area of longitudinal (calculated according to [5.2.8]), in cm . kwℓ = 1 / (1 + 2·Afn / Aw) with Afn as given in [5.2.9].
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DNV GL AS 5.4.4 The scantlings of the longitudinals shall meet the structural stability requirements of [5.6]. 5
n o
5.5 Framing – web frame and load carrying stringers i t
5.5.1 Web frames and load-carrying stringers shall be designed to withstand the ice load patch as defined in c [4.5]. The load patch shall be applied at locations where the capacity of these members under the combined e S effects of bending and shear is minimised. 6
5.5.2 Where load carrying stringers or web frames supporting local frames constitute regular structures with r sufficient and well defined support capacity and boundary condition at end supports, and with the stringer e or web frame located within the hull area considered, see [3.2], the required effective net web area and net t section modulus is as given in [5.5.3] or [5.5.5]. The required shear area and section modulus of web frames p a supporting load carrying stringers is as given in [5.5.4]. Alternatively, where web frames and load-carrying h stringers form part of a structural grillage system, appropriate methods of analysis as outlined in [8.1.3] C shall be used. 6
2 5.5.3 The effective net web area, in cm , as defined in Pt.3 Ch.3 Sec.6 [1.4.7], of web frames supporting t longitudinal local frames shall not be less than: r a P
where
AF = Hull Area Factor from Table 6/Table 7. PPFs = Peak Pressure Factor from Table 5. Pavg = Average pressure within load patch as given in [4.6.1], in MPa. Ks = [S – (LHs + s)/2]/S, minimum 0.55. LHs = Load height with respect to shear response of web frame, given as the smaller of b and (S-s), in m. LLs = Load length with respect to shear response of web frame = w (ℓ – w/4)/ℓ, in m. ℓ = Spacing of web frames, measured along the shell plate, in m. b = Height of design ice load patch as given by [4.5.1]/[4.5.2], in m. s = Longitudinal frame spacing, in m. S = Span length of web frame as given in [5.2.5], in m. w = Length of load patch as given in [4.6.1], in m, but is not to be taken larger than 2 ℓ η = Usage factor: = 0.9 φw = Smallest angle between shell plate and the web of the web frame, measured at middle of span, in degrees.
The angle φw may be taken as 90 degrees provided the smallest angle is not less than 75 degrees.
The net elastic section modulus, in cm3, of web frames supporting longitudinal local frames shall not be less than:
where:
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DNV GL AS a = Design span of local frames as given in [5.2.5], in m. 5
LHb = Load height w.r.t bending response of web frame, given as the smaller of b and S, in m. kf = End fixity parameter for the web frame n
= 2.0 when both end supports are fixed o i
= 1.5 when one end support is fixed t = 1.0 when both end supports are simply supported c e kfl = End fixity parameter for the local frames S
= 2.0 when both end supports are fixed
= 1.5 when one end support is fixed 6
= 1.0 when both end supports are simply supported r 3 ZP = Net plastic section modulus of fitted local ice frames as given in [5.2.9], in cm . e t
2 p
5.5.4 The effective net web area, in cm , as defined in Pt.3 Ch.3 Sec.6 [1.4.7], of web frames supporting a
load carrying stringers shall not be less than: h
C
6
t r
a P where
AF = Hull area factor from Table 6. PPFs = Peak pressure factor from Table 5. Pavg = Average pressure within load patch as given in [4.6.1], in MPa. b = Height of design ice load patch as given by [4.5.1]/[4.5.2], in m. C = Smallest distance from considered load carrying stringer to web frame support, in m. ℓLCS = Distance between web frames, measured along the shell plate, in m. ℓ = Distance from considered load carrying stringer to adjacent load carrying stringer or longitudinal support member, as applicable, measured along the shell plate, in m. S = Span length of web frame as given in [5.2.5], in m. w = Length of load patch as given in [4.6.1], in m. η = Usage factor: = 0.9 φw = Smallest angle between shell plate and the web of the web frame, measured at the load carrying stringer, in degrees.
The net elastic section modulus, in cm3, of web frames supporting load carrying stringer shall not be less than:
where: kf = End fixity parameter for the web frame. = 2.0 when both end supports are fixed. = 1.5 when one end support is fixed. = 1.0 when both end supports are simply supported.
5.5.5 The effective net web area, in cm2, as defined in Pt.3 Ch.3 Sec.6 [1.4.7], of load-carrying stringers shall not be less than:
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DNV GL AS
5
n o i t
c e
where: S
6
AF = Hull area factor from Table 6. r PPFs = Peak pressure factor from Table 5. e
Pavg = Average pressure within load patch, as given in [4.6.1], in MPa. t
LHs = Load height with respect to shear response of stringer = b (ℓ – b/4)/ℓ, in m. p LLs = Load length with respect to shear response of stringer, given as the smaller of w and (S-s), in m. a ℓ = Distance between transverse frame supports, measured along the shell plate, in m. h b = Height of design ice load patch as given in [4.6.1], in m. C
= Length of load patch as given in [4.6.1], in m. w 6 s = Spacing of transverse frames, in m. t
S = Span of stringer as given in [5.2.5], in m. r
η = Usage factor: a = 0.9 P φw = Smallest angle between shell plate and the web of the stringer, in degrees, measured at middle of span. The angle φw may be taken as 90 degrees provided the smallest angle is not less than 75 degrees.
3 The net elastic section modulus, in cm , of the stringer shall not be less than:
where: a = Design span of local frames as given in [5.2.5], in m. kf = End fixity parameter for the load-carrying stringer: = 2.0 when both end supports are fixed = 1.5 when one end support is fixed = 1.0 when both end supports are simply supported kfl = End fixity parameter for the local frames: = 2.0 when both end supports are fixed = 1.5 when one end support is fixed = 1.0 when both end supports are simply supported LL = Load length w.r.t bending response of stringer, given as the smaller of w and S, in m. b 3 ZP = Net plastic section modulus of fitted local ice frames as given in [5.2.9], in cm .
5.5.6 The scantlings of web frames and load-carrying stringers shall meet the structural stability requirements of [5.6].
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DNV GL AS 5.6 Framing – structural stability 5
n 5.6.1 To prevent local buckling in the web, the ratio of web height, hw, to net web thickness, twn, of any o framing member shall not exceed: i t c
For flat bar sections: e
0.5 S hw / twn ≤ 282 / (ReH) 6
For bulb, tee and angle sections: r e
0.5 t
hw / twn ≤ 805 / (ReH) p a
where: h C hw = Web height, in mm. 6 twn = Net web thickness, in mm. t r
5.6.2 Framing members for which it is not practicable to meet the requirements of [5.6.1], e.g. load carrying a stringers or deep web frames, are required to have their webs effectively stiffened. The scantlings of the web P stiffeners shall ensure the structural stability of the framing member. The minimum net web thickness for these framing members, in mm, is given by:
where: c1 = hw – 0.8·h, in mm. hw = Web height of stringer/web frame, in mm (see Figure 5). h = Height of framing member penetrating the member under consideration (0 if no such framing member), in mm (see Figure 5). c2 = Spacing between supporting structure oriented perpendicular to the member under consideration, in mm (see Figure 5).
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DNV GL AS 5
n o i t c e S
6
r e
t p Figure 5 Parameter definition for web stiffening a h
5.6.3 In addition, the following shall be satisfied: C
0.5 t ≥ 0.35·t ·(R / 235) 6 wn pn eH t where: r a
2 P ΡeH = Minimum upper yield stress of the shell plate in way of the framing member, in N/mm . twn = Net thickness of the web, in mm. tpn = Net thickness of the shell plate in way of the framing member, in mm.
5.6.4 To prevent local flange buckling of welded profiles, the following shall be satisfied:
(i) = The flange width, bf in mm, shall not be less than five times the net thickness of the web, twn. (ii) = The flange outstand, in mm, shall meet the following requirement: 0.5 bout / tfn ≤ 155 / (ReH) where: tfn = Net thickness of flange, in mm.
5.7 Plated structures
5.7.1 Plated structures are those stiffened plate elements in contact with the shell and subject to ice loads. These requirements are applicable to an inboard extent which is the lesser of:
(i) = web height of adjacent parallel web frame or stringer; or (ii)= 2.5 times the depth of framing that intersects the plated structure.
5.7.2 The thickness of the plating and the scantlings of attached stiffeners shall be consistent with the end connection requirements for supported framing as given in [5.9].
5.7.3 Plated structures subjected to direct ice loads, as defined in [4], shall be considered with respect to the buckling requirements in Pt.3 Ch.8.
5.8 Stem and stern frames
5.8.1 For PC(6) or PC(7) ships requiring 1A*/1A equivalency, the stem and stern requirements of the Finnish-Swedish ice class rules may need to be additionally considered.
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DNV GL AS 5.8.2 When the ship has a sharp edged stem, the thickness of the stem side plate within a breadth not less 5 than 0.7 s, where s denotes the spacing of stiffening members, shall not be less than 1.2 t, where t denotes the required net shell plate thickness for the bow area, as given in [5.1]. n o
The stem reinforcement shall be extending vertically from a line 1.5 m below the LIWL to the horizontal line x i m above the UIWL, see the Figure 6. t c
e S
6
r e t p
For PC1, 2, 3 & 4 x=1,5 m a
For PC5 and PC6 x=1,0 m h C Max 0.06 L 6
t x x 2 m UIWL r a P BIi B Stem area Stem area LIWL 1.5 m
BIL
Max 0.45 L FP
Figure 6 Stem reinforcement
5.8.3 In ships with class notation PC(3) to PC(1), intended to operate under harsh ice condition, and of type and size that may cause excessive beaching to occur, a forward ice knife may be required fitted. This requirement will be based on consideration of design speed, stability and freeboard.
5.9 End connections for framing members
5.9.1 The end connection for framing members exposed to ice loads, to supports, e.g. stringers, web frames, decks or bulkheads, shall be related to the response of the member when subjected to ice loads. The connection area is generally obtained through support members such as collar plate, lugs, end brackets or web stiffener.
The total net connection area of support members, in cm2, is given as:
where:
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DNV GL AS hi = Effective dimension of connection area of member #i, in mm. 5 ti = Thickness of connection area #i, in mm. kτ = 1.0 for members where critical stress response is shear n
= 1.5 for members where critical stress response is normal stress o i n = Number of support members. t c ts = Minimum corrosion addition as given in [10.1.3], in mm. e
2 S 5.9.2 The net end connection area fitted, a, is generally not to be less than ao, in cm , given as: 6
for longitudinal local frames r e t p a h C
6
for transverse local frames t r a P
for load carrying stringers
for transverse web frames supporting longitudinal local frames
where:
AF = Hull area factor from Table 6. PPF = Peak pressure factor from Table 5. Pavg = Average pressure within load patch as given in [4.6.1], in MPa. LH = Load height, given as the smaller of b and (a-s), in m. LL = Load length, given as the smaller of w and (a-s), in m. a, S = Span of member as given in [5.2.5], in m. s = Spacing of frames, in m. b, w = As given in [4.6.1]. b1 = As given in [5.4.2]. η = Usage factor: = 0.9 φw = Smallest angle between shell plate and the web of the stringer or web frame as applicable, in degrees, measured at the intersection with the stiffener. The angle φw may be taken as 90 degrees provided the smallest angle is not less than 75 degrees.
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DNV GL AS 5.9.3 For support members constituting the end connection, the throat thickness in mm of double fillet welds 5 for the attachment of the support member i, to the framing member and the support is given as the smaller of: n
o i t c e S
6
= 0.5 ti r e t where: p a a = As given in [5.9.1]. h = As given in [5.9.2]. C ao = Thickness of connection member i, in mm. ti 6 = As given in Pt.3 Ch.13 Sec.1 [2.5.2] fyd t ts = Corrosion addition/abrasion addition as given in [10.1.3], in mm. r a
The throat thickness not be less than as given in Pt.3 Ch.13 Sec.1 [2.5]. P
6 Longitudinal strength
6.1 Application
6.1.1 Ice loads need only be combined with still water loads. The combined stresses shall be compared against permissible bending and shear stresses at different locations along the ship’s length. In addition, sufficient local buckling strength is also to be verified.
6.2 Design vertical ice force at the bow
6.2.1 The design vertical ice force at the bow, in MN, shall be taken as:
FIB = minimum (FIB,1; FIB,2) where:
0.15 0.2 0.5 FIB,1 = 0.534·KI ·sin (γstem)·(Δkt ·Kh) ·CFL , in MN FIB,2 = 1.20·CFF , in MN KI = Indentation parameter = Kf / Kh a) For the case of a blunt bow form: 1-eb 0.9 -0.9·(1 + eb) Kf = (2·C·B / (1 + eb)) ·tan(γstem) b) For the case of wedge bow form (αstem < 80 deg), eb = 1 and the above simplifies to: 2 0.9 Kf = (tan(αstem) / tan (γstem))
Kh = 0.01·Awp , in MN/m.
CFL = Longitudinal Strength Class Factor from Table 4 eb = Bow shape exponent which best describes the water plane (see Figure 7 and Figure 8) = 1.0 for a simple wedge bow form = 0.4 to 0.6 for a spoon bow form
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DNV GL AS = 0 for a landing craft bow form 5 An approximate eb determined by a simple fit is acceptable. n γstem = Stem angle to be measured between the horizontal axis and the stem tangent at the upper ice o
waterline, in degrees, (buttock angle as per Figure 2 measured on the centerline). i t
α = Hull waterline angle to be measured at stem (centre line) at the UIWL, see Figure 2, in degrees. c stem eb
C = 1 / (2·(LB / B) ) e eb LB = Bow length used in the equation y = B / 2·(x/LB) , in m, see Figure 7 and Figure 8. S
= Ship displacement, in ktonnes, at UIWL, not to be taken less than 10 ktonnes.
Δ 6 kt 2 Awp = Ship water plane area, in m . CF = Flexural Failure Class Factor from Table 4. r F e t
Draught dependent quantities are, where applicable, to be determined at the waterline corresponding to the p loading condition under consideration. a h C
6.3 Design vertical shear force 6
t
6.3.1 The design vertical ice shear force along the hull girder, in MN, shall be taken as: r a F = C ·F I f IB P where:
Cf = Longitudinal distribution factor to be taken as follows: a) Positive shear force
Cf= 0.0 between the aft end of L and 0.6 L from aft Cf= 1.0 between 0.9 L from aft and the forward end of L b) Negative shear force
Cf= 0.0 at the aft end of L Cf= – 0.5 between 0.2 L and 0.6 L from aft Cf= 0.0 between 0.8 L from aft and the forward end of L. Intermediate values shall be determined by linear interpolation.
Figure 7 Bow shape definition
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DNV GL AS 5
n o i t c e S
6
r e t p a h C
6
t r
a P
Figure 8 Illustration of eb effect on the bow shape for B = 20 and LB =16
Table 8 Longitudinal strength criteria
Permissible Stress when Permissible Stress Failure Mode Applied Stress ReH / Rm ≤ 0.7 when ReH / Rm > 0.7
Tension σa η·ReH η·0.41 (Rm+ ReH)
0.5 Shear τa η·τeH η·0.41 (Rm+ ReH) / (3)
σc for plating and for web plating of stiffeners σa Buckling σc / 1.1 for stiffeners
τa τc
6.3.2 The applied vertical shear stress, τa, shall be determined along the hull girder in a similar manner as in Pt.3 Ch.5 Sec.1 by substituting the design vertical ice shear force for the design vertical wave shear force.
6.4 Design vertical ice bending moment
6.4.1 The design vertical ice bending moment along the hull girder, in MNm, shall be taken as:
-0.2 MI = 0.1·Cm·L·sin (γstem)·FIB where:
γ stem is as given in [6.2.1]
FIB = Design vertical ice force at the bow, in MN. Cm = Longitudinal distribution factor for design vertical ice bending moment to be taken as follows: Cm = 0.0 at the aft end of L
Cm = 1.0 between 0.5 L and 0.7 L from aft
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DNV GL AS Cm = 0.3 at 0.95 L from aft 5 Cm = 0.0 at the forward end of L. L = Ship length as defined in Pt.3 Ch.1 Sec.4, but measured on the upper ice waterline [UIWL], in n o m. i t
Intermediate values shall be determined by linear interpolation. c e S
Draught dependent quantities are, where applicable, to be determined at the waterline corresponding to the loading condition under consideration. 6
r
6.4.2 The applied vertical bending stress, σa, shall be determined along the hull girder in a similar manner e t
as in Pt.3 Ch.5 Sec.1 by substituting the design vertical ice bending moment for the design vertical wave p
bending moment. The ship still water bending moment shall be taken as the maximum sagging moment. a h C 6.5 Longitudinal strength criteria 6
6.5.1 The strength criteria provided in Table 8 shall be satisfied. The design stress shall not exceed the t r
permissible stress. a P where:
σ = Applied vertical bending stress, in N/mm2. a 2 τa = Applied vertical shear stress, in N/mm . Ρ = Specified minimum yield stress of the material, in N/mm2. eH 2 Ρm = Specified minimum tensile strength of material, in N/mm . σ = Critical buckling stress in compression, according to Pt.3 Ch.8, in N/mm2. c 2 τc = Critical buckling stress in shear, according to Pt.3 Ch.8, in N/mm . η = 0.8.
7 Appendages
7.1 General
7.1.1 All appendages shall be designed to withstand forces appropriate for the location of their attachment to the hull structure or their position within a hull area, as given below. For appendages of type or arrangement other than as considered in the following, the load definition and response criteria are subject to special consideration.
7.1.2 Stern frames, rudders and propeller nozzles shall be designed according to the rules given in Pt.3 Ch.14 Sec.1.
7.1.3 Bilge keels are normally to be avoided and should preferably be substituted by roll-damping equipment. If bilge keels are fitted, it is required that the connection to the hull is so designed that the risk of damage to the hull, in case the bilge keel is ripped off, is minimized.
7.1.4 Additional requirements for ice reinforced ships are given in the following. For ships with rudders which are not located behind the propeller, special consideration will be made with respect to the longitudinal ice load.
7.2 Rudders
7.2.1 The rudder stock and upper edge of the rudder shall be effectively protected against ice pressure.
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DNV GL AS 7.2.2 Rudder stops are to be provided. The design ice force on rudder shall be transmitted to the rudder 5 stops without damage to the steering system. n o
7.2.3 Ice horn shall in general be fitted to protect the rudder in centre position. The ice horn shall extend i below BWL. Design forces shall be determined according to the [12.5]. t c e 7.2.4 Ice horns shall be fitted directly abaft each rudder in such a manner that: S — the upper edge of the rudder is protected within two degrees to each side of the mid position when going 6
astern, and r — ice is prevented from wedging between the top of the rudder and the ship's hull. e t The ice horn shall extend vertically to, minimum = 1.5 CF , in m, below LIWL, where CF shall be taken as
D D p
given in Table 4. Alternatively an equivalent arrangement shall be arranged. a h
7.2.5 Exposed seals for rudder stock are assumed to be designed for the given environmental conditions C such as: 6
— ice formation t — specified design temperature. r a P 7.3 Ice forces on rudder
7.3.1 The ice force, FU, acting on the uppermost part of the rudder, the ice horn included shall be assessed on a case to case basis based on the Society’s current practice.
The force FU shall be divided between rudder and ice horn according to their support position. The force acting on the ice horn, in kN, may generally be taken as:
X = Distance from leading edge of rudder to point of attack of the force F: = 0.5 ℓr minimum, in m. = 0.67 ℓr maximum, in m. ℓr = Length of rudder profile (including ice horn), in m. XF = Longitudinal distance, in m, from the leading edge of the rudder to the axis of the rudder stock. XK = Distance, in m, from leading edge of rudder to centre of ice horn.
For this loading the stress response of the rudder, the ice horn and support structures for these shall not exceed ReH, where ReH denotes the specified minimum yield stress of the material.
7.3.2 The ice force, FR, acting on the rudder the distance zLIWL below LIWL shall be assessed on a case to case basis based on the Society’s current practice.
The rudder force, FR, in kN, gives rise to bending moments in the rudder, the rudder stock and the rudder horn, as applicable. Alternative positions for the ice load area shall be considered in order that the maximum bending moment shall be determined.
The bending moment in way of the rudder section in question, in kNm, is given as:
MB = FR·hs
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DNV GL AS hs = Vertical distance from the ice load area position to the rudder section in question, in m. 5
The rudder force, FR, gives rise to a rudder torque, MTR, and a bending moment in the rudder stock, MB, n o which both will vary depending on the position of the assumed ice load area, and on the rudder type and i arrangement used. t c e In general the load giving the most severe combination of F , M and M with respect to the structure under R TR B S consideration shall be applied in a direct calculation of the rudder structure. 6
The design value of MTR is given by: r e t
MTR = FR (0.6 ℓr – XF), in kNm p
= 0.15 FR ℓr minimum a XF = Longitudinal distance, in m, from the leading edge of the rudder to the axis of the rudder stock. h = Length of rudder profile, in m. C ℓr 6
t
7.4 Rudder scantlings r a
7.4.1 Scantlings of rudder, rudder stock, rudder horn and rudder stoppers, as applicable, shall be calculated P for the force, F, given in [7.3.1] acting on the rudder and ice horn, with respect to bending and shear. The nominal von Mises stress shall not exceed ReH, where ReH denotes the specified minimum yield stress of the material in N/mm2.
7.4.2 The scantlings of rudders, rudder stocks and shafts, pintles, rudder horns and rudder actuators shall be calculated from the formulae given in Pt.3 Ch.14 Sec.1, inserting the rudder torque MTR, bending moments MB and rudder force FR as given in [7.3.2].
7.4.3 Provided an effective torque relief arrangement is installed for the steering gear, and provided effective ice stoppers are fitted, the design rudder torque need not be taken greater than:
M TR = MTRO MTRO = Steering gear relief torque, in kNm.
7.4.4 For rudder plating the ice load thickness shall be calculated as given in [5.1] for the stern area or lower stern area as applicable.
7.5 Ice loads on propeller nozzles
7.5.1 The transverse ice force, FN, shall be calculated as outlined in [7.7].
7.5.2 The longitudinal ice force, FL, acting on the nozzle shall be assessed on a case to case basis based on the Society’s current practice.
For the determination of FL, the following two alternative ice load areas, A, shall be considered: — an area positioned at the lower edge of the nozzle with width equal to 0.65 D and height equal to the height of the nozzle profile, in m — an area on both sides of the nozzle at the propeller shaft level, with transverse width equal to the height of the nozzle profile in m and with height equal to 0.35 D. Both symmetric and asymmetric loading shall be checked. D = Nozzle diameter, in m.
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DNV GL AS 7.6 Propeller nozzle scantlings 5
7.6.1 The scantlings of the propeller nozzle and its supports in the hull shall be calculated for the ice loads n o given in [7.5]. The nominal von Mises stress shall not exceed ReH, where ReH denotes the specified minimum i 2 t
yield stress of the material in N/mm . c
For nozzle plating the ice load thickness shall be taken as given in [5.1] using the design ice pressure as e given for the stern area, lower stern area as applicable. S
6
7.7 Podded propulsors and azimuth thrusters r e t
7.7.1 Ships operating in ice and equipped with podded propulsors or azimuth thrusters shall be designed p according to operational mode and purpose stated in the design specification. If not given, it shall be a assumed that the ship may operate longer periods in ice using astern running mode as part of its operational h C
profile. When limitations are given, this information shall also be stated in the ship's papers. 6 7.7.2 Ramming astern is not anticipated. t r
7.7.3 Documentation of both local and global strength capacity of the pod/thruster shall be submitted for a class assessment. Recognised structural idealisation and calculation methods shall be applied. P
7.7.4 Ice loads on pod/thruster body shall be assessed on a case by case basis based on the Society’s current practice.
7.7.5 The nominal von Mises stress shall not exceed ReH, where ReH denotes the specified minimum yield stress of the material in N/mm2.
8 Direct calculations
8.1 General
8.1.1 Direct calculations shall not be utilised as an alternative to the analytical procedures prescribed for shell plating and local frames.
8.1.2 Where direct calculation is used to check the strength of structural systems, the load patch specified in [4.5] with design pressure given as the product (AFPavg) shall be applied at locations that maximize the shear and bending response of the structure members in focus for the calculation.
AF = As given in Table 6. Pavg = As given in [4.6].
8.1.3 Direct calculations may be used for the scantling control of the support structures for local frames, including load-carrying stringers, web frames and plated structures in general. The extent of the structure model must be such that possible inaccuracies in the support definition will not affect the calculation results significantly. The calculation shall ensure that stress response of webs and flanges of girder structures, when a usage factor = 0.9 is included, does not exceed yield or the buckling capacity. The documentation of direct strength analyses shall be in accordance with Pt.3 Ch.7 Sec.1.
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DNV GL AS 5 9 Welding n o i 9.1 General t c e
9.1.1 All welding within ice-strengthened areas shall be of the double continuous type. S
6
9.1.2 Continuity of strength shall be ensured at all structural connections. r e t
9.2 Minimum weld requirements p a
9.2.1 The weld connection of local frames and load carrying stringers and web frames supporting local h
frames to shell shall be as given in Pt.3 Ch.13 Sec.1 [2.5] with the weld factor fw given as: C
6 fw = 0.31rw, minimum 0.26, for middle 60% of span t
= 0.52rw, minimum 0.43, at ends. r r = Ratio of required net web area over fitted net web area for member considered. For transverse local a
w P frames, rw is, however, not to be taken less than:
where:
LLs = Length of loaded portion of span, in m. = Lesser of a and (b - 0.5 s), in m. a = Frame span as defined in [5.2.5], in m. b = Height of design ice load patch as given in [4.5], in m. s = Transverse frame spacing, in m. AF = Hull Area Factor from Table 6. PPFi = Peak Pressure Factor from Table 5. Pavg = Average pressure within load patch as given in [4.6], in MPa.
9.2.2 Weld throat thickness need not be greater than 0.50 x plate thickness.
10 Materials and corrosion protection
10.1 Corrosion/abrasion additions and steel renewal
10.1.1 Effective protection against corrosion and ice-induced abrasion is recommended for all external surfaces of the shell plating for all polar ships.
10.1.2 The values of corrosion/abrasion additions, ts, to be used in determining the shell plate thickness are listed in Table 9.
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DNV GL AS Table 9 Corrosion/abrasion additions for shell plating 5
ts [mm] n o i
With effective protection Without effective protection t Hull Area c
PC(4) PC(6) PC(1) PC(4) PC(6) e PC(1)PC(2)PC(3)
PC(5) PC(7) PC(2)PC(3) PC(5) PC(7) S
Bow; bow intermediate ice belt 3.5 2.5 2.0 7.0 5.0 4.0 6
r Bow intermediate lower; midbody and stern 2.5 2.0 2.0 5.0 4.0 3.0 e ice belt t p
Midbody and stern lower; bottom 2.0 2.0 2.0 4.0 3.0 2.5 a h C
10.1.3 Polar ships shall have a minimum corrosion/abrasion addition of ts = 1.0 mm applied to all internal structures within the ice-strengthened hull areas, including plated members adjacent to the shell, as well as 6
stiffener webs and flanges. Additionally, the corrosion/abrasion addition, ts, shall not be less than tc as given t in Pt.3 Ch.3 Sec.3. r a P 10.1.4 Steel renewal for ice strengthened structures is required when the gauged thickness is less than tnet + 0.5 mm.
10.2 Hull materials
10.2.1 Plating materials for hull structures shall be not less than those given in Table 11 and Table 12 based on the as-built thickness of the material, the PC class notation assigned to the ship and the material class of structural members given in [10.2.2].
10.2.2 Material classes specified in Pt.3 Ch.3 Sec.1 are applicable to polar ships regardless of the ship’s length. In addition, material classes for weather and sea exposed structural members and for members attached to the weather and sea exposed shell plating of Polar class ships are given in Table 10. Where the material classes in Table 10 and those in Pt.3 Ch.3 Sec.1 differ, the higher material class shall be applied.
Table 10 Material classes for structural members of polar ships
Material Structural Members Class
Shell plating within the bow and bow intermediate ice belt hull areas (B, BIi) III
All weather and sea exposed SECONDARY and PRIMARY, as defined in Pt.3 Ch.3 Sec.1 Table 3, structural II members outside 0.4 L amidships
Plating materials for stem and stern frames, rudder horn, rudder, propeller nozzle, shaft brackets, ice skeg, III ice knife and other appendages subject to ice impact loads
All inboard framing members attached to the weather and sea-exposed plating including any contiguous II inboard member within 600 mm of the plating
Weather-exposed plating and attached framing in cargo holds of ships which by nature of their trade have II their cargo hold hatches open during cold weather operations
All weather and sea exposed SPECIAL, as defined in Pt.3 Ch.3 Sec.1 Table 3, structural members within 0.2 L III from FE
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DNV GL AS 10.2.3 Steel grades for all plating and attached framing of hull structures and appendages situated below the 5 level of 0.3 m below the lower waterline, as shown in Figure 9, shall be obtained from Pt.3 Ch.3 Sec.1based on the material class for structural members in Table 10 above, regardless of qualifier. n o
i t c e S
6
Figure 9 Steel grade requirements for submerged and weather exposed shell plating r e
Table 11 Steel grades for weather exposed plating t p
Material class II Material class III Material class IV a h
Thickness PC(1) PC(6) PC(1) PC(6) PC(1) PC(4) PC(6) C
through (5) and (7) through (5) and (7) through (3) and (5) and (7)
t [mm] 6
MS HT MS HT MS HT MS HT MS HT MS HT MS HT t r
t ≤ 10 B AH B AH B AH B AH E EH E EH B AH a P 10 < t ≤ 15 B AH B AH D DH B AH E EH E EH D DH
15 < t ≤ 20 D DH B AH D DH B AH E EH E EH D DH
20 < t ≤ 25 D DH B AH D DH B AH E EH E EH D DH
25 < t ≤ 30 D DH B AH E EH 2) D DH E EH E EH E EH
30 < t ≤ 35 D DH B AH E EH D DH E EH E EH E EH
35 < t ≤ 40 D DH D DH E EH D DH F FH E EH E EH
40 < t ≤ 45 E EH D DH E EH D DH F FH E EH E EH
45 < t ≤ 50 E EH D DH E EH D DH F FH F FH E EH
Notes:
1) = Includes weather-exposed plating of hull structures and appendages, as well as their outboard framing members, situated above a level of 0.3 m below the lowest ice waterline. 2) = Grades D, DH are allowed for a single strake of side shell plating not more than 1.8 m wide from 0.3 m below the lowest ice waterline.
Table 12 Steel grades for inboard framing members attached to weather exposed plating
PC(1) through PC(5) PC(6) and PC(7) Thickness t, mm MS HT MS HT
t ≤ 20 B AH B AH
20 35 45 10.2.4 Steel grades for all weather exposed plating of hull structures and appendages situated above the level of 0.3 m below the lower ice waterline, as shown in Figure 9, shall be not less than given in Table 11. Rules for classification: Ships — DNVGL-RU-SHIP-Pt6Ch6. Edition October 2015 Page 152 Cold climate DNV GL AS 10.2.5 Steel grades for all inboard framing members attached to weather exposed plating shall be not less 5 than given in Table 12. This applies to all inboard framing members as well as to other contiguous inboard members (e.g. bulkheads, decks) within 600 mm of the exposed plating. n o i 10.2.6 Castings and forgings shall have specified properties consistent with the expected service t temperature for the cast component. Forged or cast materials in structural members exposed to design c temperatures lower than 10°C, shall fulfil requirements given in Sec.3 Table 7 item C1001. The test e S temperature of components fully exposed to the ambient air shall, if the design temperature has not been specified, for notations PC(1) to PC(5) be taken as -20ºC and for notations PC(6) and PC(7) as -10ºC. 6 r e 10.3 Materials for machinery components exposed to sea water t p a 10.3.1 Materials exposed to sea water, such as propeller blades, propeller hub, cast thrusters body shall h have an elongation not less than 15% on a test specimen with a length which is five times the diameter of C test specimen. 6 10.3.2 Charpy V impact tests shall be carried out for materials other than bronze and austenitic steel. t Average impact energy of 20 J taken from three Charpy V tests shall be obtained at minus 10ºC. r a P 10.4 Materials for machinery components exposed to sea water temperatures 10.4.1 Materials exposed to sea water temperature shall be of steel or other approved ductile material. 10.4.2 Charpy V impact tests shall be carried out for materials other than bronze and austenitic steel. An average impact energy value of 20 J taken from three tests shall be obtained at minus 10ºC. This requirement applies to blade bolts, CP-mechanisms, shaft bolts, strut-pod connecting bolts, etc. This does not apply to surface hardened components, such as bearings and gear teeth. 10.5 Materials for machinery components exposed to low air temperature 10.5.1 Materials of essential components exposed to low air temperature shall be of steel or other approved ductile material. An average impact energy value of 20 J taken from three Charpy V tests shall be obtained at 10ºC below the lowest design temperature. This does not apply to surface hardened components, such as bearings and gear teeth. For definition of structural boundaries exposed to air temperature see [10.2.4]. 11 Ice interaction loads – machinery 11.1 Propeller ice interaction 11.1.1 These rules cover open and ducted type propellers situated at the stern of a ship having controllable pitch or fixed pitch blades. Ice loads on bow propellers and pulling type propellers shall receive special consideration. The given loads are expected, single occurrence, maximum values for the whole ships service life for normal operational conditions. These loads do not cover off-design operational conditions, for example when a stopped propeller is dragged through ice. These rules cover loads due to propeller ice interaction also for azimuth and fixed thrusters with geared transmission or integrated electric motor (“geared and podded propulsors”). However, the load models of these rules do not cover propeller/ice interaction loads when ice enters the propeller of a turned azimuthing thruster from the side (radially) or when ice block hits on the propeller hub of a pulling propeller/thruster. Rules for classification: Ships — DNVGL-RU-SHIP-Pt6Ch6. Edition October 2015 Page 153 Cold climate DNV GL AS 11.1.2 The loads given in this section are total loads (unless otherwise stated) during ice interaction and 5 shall be applied separately (unless otherwise stated) and are intended for component strength calculations only. n o i 11.1.3 Fb is a force bending a propeller blade backwards when the propeller mills an ice block while rotating t c ahead. Ff is a force bending a propeller blade forwards when a propeller interacts with an ice block while e rotating ahead. S 6 11.2 Ice class factors r e t 11.2.1 Table 13 below lists the design ice thickness and ice strength index to be used for estimation of the p propeller ice loads. a h Table 13 Ice class factors C 6 Ice Class Hice[m] S ice[-] t PC(1) 4.0 1.2 r a PC(2) 3.5 1.1 P PC(3) 3.0 1.1 PC(4) 2.5 1.1 PC(5) 2.0 1.1 PC(6) 1.75 1 PC(7) 1.5 1 where: Hice = Ice thickness for machinery strength design, in m. Sice = Ice strength index for blade ice force. 11.3 Design ice loads for open propeller 11.3.1 Maximum backward blade force, in kN when D < Dlimit: when D ≥ Dlimit: 1.4 Dlimit = 0.85·[Hice] , in m. Rules for classification: Ships — DNVGL-RU-SHIP-Pt6Ch6. Edition October 2015 Page 154 Cold climate DNV GL AS where: 5 n = Nominal rotational speed (at MCR free running condition) for CP-propeller and 85% of the n nominal rotational speed (at MCR free running condition) for a FP-propeller (regardless driving o i engine type), in rps. t D = Propeller diameter, in m. c EAR = Expanded blade area ratio. e S Z = Number of propeller blades. 6 Fb shall be applied as a uniform pressure distribution to an area on the back (suction) side of the blade for r the following load cases: e t a) Load case 1:from 0.6 R to the tip and from the blade leading edge to a value of 0.2 chord length p a b) Load case 2:a load equal to 50% of the Fb shall be applied on the propeller tip area outside of 0.9 R h c) Load case 5:for reversible propellers a load equal to 60% of the greater of Fb or Ff, shall be applied from C 0.6 R to the tip and from the blade trailing edge to a value of 0.2 chord length. 6 Table 14 Design ice load cases for maximum backward blade force for open propellers t r a Right handed propeller P Force Loaded area blade seen from back Uniform pressure applied on the back of the blade (suction side) to an area from 0.6 R to Load case 1 F b the tip and from the leading edge to 0.2 times the chord length Uniform pressure applied on the back of the Load case 2 50% of Fb blade (suction side) on the propeller tip area outside of 0.9 R radius. Rules for classification: Ships — DNVGL-RU-SHIP-Pt6Ch6. Edition October 2015 Page 155 Cold climate DNV GL AS Right handed propeller Force Loaded area 5 blade seen from back n o i t c e S 60% of Uniform pressure applied on propeller face Ff or Fb (pressure side) to an area from 0.6 R to the 6 Load case 5 which one tip and from the trailing edge to 0.2 times the r is greater chord length e t p a h C 6 11.3.2 Maximum forward blade force, in kN t when D < Dlimit: r a P when D ≥ Dlimit: where: d = Propeller hub diameter, in m. D = Propeller diameter, in m. EAR = Expanded blade area ratio. Z = Number of propeller blades. Ff shall be applied as a uniform pressure distribution to an area on the face (pressure) side of the blade for the following loads cases: a) Load case 3: from 0.6 R to the tip and from the blade leading edge to a value of 0.2 chord length b) Load case 4: a load equal to 50% of the Ff shall be applied on the propeller tip area outside of 0.9 R c) Load case 5: for reversible propellers a load equal to 60% of the greater of Ff or Fb shall be applied from 0.6 R to the tip and from the blade trailing edge to a value of 0.2 chord length. Rules for classification: Ships — DNVGL-RU-SHIP-Pt6Ch6. Edition October 2015 Page 156 Cold climate DNV GL AS Table 15 Design ice load cases for maximum forward blade force for open propellers 5 Force Loaded area Right handed propeller blade seen from back n o i t c e S Uniform pressure applied on the blade face 6 (pressure side) to an area from 0.6 R to the Load case 3 F r f tip and from the leading edge to 0.2 times the e chord length. t p a h C 6 t r a P Uniform pressure applied on propeller face Load case 4 50% of Ff (pressure side) on the propeller tip area outside of 0.9 R radius. 60% of Uniform pressure applied on propeller face F or F (pressure side) to an area from 0.6 R to the Load case 5 f b which one tip and from the trailing edge to 0.2 times the is greater chord length 11.3.3 Maximum blade spindle torque, Qsmax Spindle torque Qsmax around the spindle axis of the blade fitting shall be calculated both for the load cases described in [11.3.1] and [11.3.2] for FbFf. If these spindle torque values are less than the default value given below, the default minimum value, in kNm, shall be used: Default Value: Qsmax = 0.25 Fc0.7 where: c0.7 = Length of the blade chord at 0.7 R radius, in m. F is either Fb or Ff which ever has the greater absolute value. 11.3.4 Maximum propeller ice torque, in kNm, applied to the propeller when D < Dlimit: Rules for classification: Ships — DNVGL-RU-SHIP-Pt6Ch6. Edition October 2015 Page 157 Cold climate DNV GL AS 5 n o i t c e where: S = 14.7 for PC(1) - PC(5); and 6 kopen kopen = 10.9 for PC(6) - PC(7) r e t p when D ≥ Dlimit: a h C 6 t r a Dlimit = 1.8·Hice, in m. P where: P0.7 = Propeller pitch at 0.7 R, in m. n = Rotational propeller speed, in rps, at bollard condition. If not known, n shall be taken as shown in Table 16 below: Table 16 Rotational propeller speed, n, at bollard condition Propeller type n CP propellers nn FP propellers driven by turbine or electric motor nn FP propellers driven by diesel engine 0.85 nn where nn is the nominal rotational speed at MCR, free running condition. For CP propellers, propeller pitch,P0.7 shall correspond to MCR in bollard condition. If not known, P0.7 shall be taken as 0.7 P0.7n, where P0.7n is propeller pitch at MCR free running condition. 11.3.5 Maximum propeller ice thrust, in kN, applied to the shaft: Thf = 1.1 Ff Thb = 1.1 Fb However, the load models of this UR do not include propeller/ice interaction loads when ice block hits on the propeller hub of a pulling propeller. 11.4 Design ice loads for ducted propeller 11.4.1 Maximum backward blade force, in kN: when D < Dlimit: Rules for classification: Ships — DNVGL-RU-SHIP-Pt6Ch6. Edition October 2015 Page 158 Cold climate DNV GL AS 5 n o i t c when D ≥ or equal Dlimit: e S 6 r e t p a where Dlimit = 4 Hice, in m. h n shall be taken as in [11.3.1]. C Fb shall be applied as a uniform pressure distribution to an area on the back side for the following load cases: 6 t a) Load case 1: On the back of the blade from 0.6 R to the tip and from the blade leading edge to a value r of 0.2 chord length a P b) Load case 5: For reversible rotation propellers a load equal to 60% of the greater of Fb or Ff is applied on the blade face from 0.6R to the tip and from the blade trailing edge to a value of 0.2 chord length. Table 17 Design ice load cases for maximum backward blade force for ducted propellers Right handed propeller Force Loaded area blade seen from back Uniform pressure applied on the back of the blade (suction side) to an area Load case 1 Fb from 0.6 R to the tip and from the leading edge to 0.2 times the chord length Uniform pressure applied on propeller 60% of Ff or face (pressure side) to an area from Load case 5 F which one is b 0.6 R to the tip and from the trailing greater edge to 0.2 times the chord length 11.4.2 Maximum forward blade force, in kN: when D ≤ Dlimit: Rules for classification: Ships — DNVGL-RU-SHIP-Pt6Ch6. Edition October 2015 Page 159 Cold climate DNV GL AS 5 n o i t c when D > Dlimit: e S 6 r e t p a where: h C 6 t r a P Ff shall be applied as a uniform pressure distribution to an area on the face (pressure) side for the following load case: a) Load case 3: On the blade face from 0.6 R to the tip and from the blade leading edge to a value of 0.5 chord length b) Load case 5: A load equal to 60% of the greater of Ff or Fb shall be applied from 0.6 R to the tip and from the blade leading edge to a value of 0.2 chord length. Table 18 Design ice load cases for maximum forward blade force for ducted propellers Right handed propeller Force Loaded area blade seen from back Uniform pressure applied on the blade face (pressure side) to an area from 0.6 Load case 3 F f R to the tip and from the leading edge to 0.5 times the chord length. Rules for classification: Ships — DNVGL-RU-SHIP-Pt6Ch6. Edition October 2015 Page 160 Cold climate DNV GL AS Right handed propeller Force Loaded area 5 blade seen from back n o i t c e Uniform pressure applied on propeller S 60% of F or F f b face (pressure side) to an area from 0.6 Load case 5 which one is 6 R to the tip and from the trailing edge greater r to 0.2 times the chord length e t p a h C 11.4.3 Maximum blade spindle torque for CP-mechanism design, Qsmax.Spindle torque Qsmax around the 6 spindle axis of the blade fitting shall be calculated for the load case described in [11.1]. If these spindle t torque values are less than the default value given below, in kNm, the default value shall be used: Default r a Value: Qsmax = 0.25 Fc0.7 where c0.7 the length of the blade section at 0.7 R radius and F is either Fb or Ff P which ever has the greater absolute value. 11.4.4 Maximum propeller ice torque applied to the propeller Tmax is the maximum torque on a propeller due to ice-propeller interaction, in kNm. when D ≤ Dlimit: where: kducted = 10.4 for PC(1) - PC(5); and kducted = 7.7 for PC(6) - PC(7) when D > Dlimit: where Dlimit = 1.8 Hice, in m. “n” is the rotational propeller speed, in r.p.s., at bollard condition. If not known, n shall be taken as shown in Table 19 below: Table 19 Rotational propeller speed, n, at bollard condition Propeller type n Rules for classification: Ships — DNVGL-RU-SHIP-Pt6Ch6. Edition October 2015 Page 161 Cold climate DNV GL AS CP propellers n n 5 FP propellers driven by turbine or electric motor nn n o i FP propellers driven by diesel engine 0.85 nn t c e where n is the nominal rotational speed at MCR, free running condition. n S For CP propellers, propeller pitch P shall correspond to MCR in bollard condition. If not known, P shall be 6 , 0.7 0.7 taken as 0.7 P0.7n, where P0.7n is propeller pitch at MCR free running condition”. r e t 11.4.5 Maximum propeller ice thrust (applied to the shaft at the location of the propeller), in kN: p a Thf = 1.1 Ff h Thb = 1.1 Fb C 6 11.5 Propeller blade loads and stresses for fatigue analysis t r a 11.5.1 Blade stresses P The blade stresses at various selected load levels for fatigue analysis shall be taken proportional to the stresses calculated for maximum loads given in sections [11.3.1], [11.3.2], [11.4.1] and [11.4.2]. The peak stresses are those determined due to Ff and Fb. The peak stress range Δσmax and the maximum stress amplitude FAmax are determined on the basis of: 11.6 Design ice loads for propulsion line 11.6.1 Torque The propeller ice torque excitation for shaft line dynamic analysis shall be described by a sequence of blade impacts which are of half sine shape and occur at the blade. The torque due to a single blade ice impact as a function of the propeller rotation angle, in kNm, is then defined as: T(ϕ) = CqTmax sin(ϕ(180/αi)) when ϕ rotates from 0 to αi plus integer revolutions T(ϕ) = 0 when ϕ rotates from αi to 360 plus integer revolutions where Cq and αi parameters are given in Table 20. Table 20 Propeller ice torque parameters Torque excitation Propeller-ice interaction Cq αi Case 1 Single ice block 0.75 90 Case 2 Single ice block 1.0 135 Case 3 Two ice blocks with 45 degree phase in rotation angle 0.5 45 Rules for classification: Ships — DNVGL-RU-SHIP-Pt6Ch6. Edition October 2015 Page 162 Cold climate DNV GL AS The total ice torque is obtained by summing the torque of single blades taking into account the phase shift 5 360 deg/Z. The number of propeller revolutions during a milling sequence shall be obtained with the formula: n NQ = 2 Hice o i and total number of impacts during one ice milling sequence is t c e S 6 In addition, the impacts shall ramp up over 270 degrees and subsequently ramp down over 270 degrees. The total excitation torque from the 3 cases will then look like the figures below. See Figure 10. r e t p a h C 6 t r a P Rules for classification: Ships — DNVGL-RU-SHIP-Pt6Ch6. Edition October 2015 Page 163 Cold climate DNV GL AS Cold climate R u l e s f o r c l a s s i f i c a t i o n : S h i p s — D N V G L - R U - S H I P - P t 6 C D h Case 1 Case 2 Case 3 6 N . V E d G Figure 10 The shape of the propeller ice torque excitation for 90, 135 degrees single blade impact sequences and 45 i t i L o degrees double blade impact sequence (Case 1 to 3 respectively apply for propeller with 4 blades). n A O S c t o b e r 2 0 1 5 P a g e 164 Part 6 Chapter 6 Section 5 Milling torque sequence duration is not valid for pulling bow propellers, which are subject to special 5 consideration. n 11.6.2 Response torque in the propulsion system o i The response torque, Tr(t) at any component in the propulsion system shall be analysed by means of t c transient torsional vibration analysis considering the excitation torque at the propeller T(ϕ) as given in e [11.6.1], the actual available engine torque Te, and the mass elastic system. Calculations have to be carried S out for all excitation cases given in [11.6.1] and the excitation torque has to be applied on top of the mean 6 hydrodynamic torque in bollard condition at considered propeller rotational speed. The worst phase angle between the ice interactions and any high torsional vibrations caused by engine excitations (e.g. 4th order r e engine excitation in direct coupled 2-stroke plants with 7-cyl. engine) should be considered in the analysis. t Guidance note: p a A recommended way of performing transient torsional vibration calculations is given in Class Guideline, DNVGL-CG-0041. h Alternative methods to the ones given in Class Guideline, DNVGL-CG-0041 may also be considered on the basis of equivalence. C ---e-n-d---of---g-u-i-d-a-n-c-e---n-o-t-e--- 6 The results of the 3 cases shall be used in the following way: t 1) The highest peak torque (between the various lumped masses in the system) is in the following referred r a to as peak torque Tpeak. P 2) The highest torque amplitude during a sequence of impacts shall be determined as half of the range from max to min torque and is referred to as TAmax. Figure 11 Response torque over time 11.6.3 Maximum response thrust Thr Maximum thrust along the propeller shaft line shall be calculated with the formulae below. The factors 2.2 and 1.5 take into account the dynamic magnification due to axial vibration. Alternatively the propeller thrust magnification factor may be calculated by dynamic analysis. Maximum Shaft Thrust Forwards, in kN: Thr = Thn + 2.2 Thf Maximum Shaft Thrust Backwards, in kN: Thr = 1.5 Thb Thn = Propeller bollard thrust, in kN. Rules for classification: Ships — DNVGL-RU-SHIP-Pt6Ch6. Edition October 2015 Page 165 Cold climate DNV GL AS Thf = Maximum forward propeller ice thrust, in kN. 5 If hydrodynamic bollard thrust, Thn is not known, Thn shall be taken as shown in Table 21 below: n o i Table 21 Hydrodynamic bollard thrust, Thn t c e Propeller type Thn S CP propellers (open) 1.25 Th 6 r CP propellers (ducted) 1.1 Th e t FP propellers driven by turbine or electric motor Thr p a FP propellers driven by diesel engine (open) 0.85 Th h C FP propellers driven by diesel engine (ducted) 0.75 Th 6 Th = Nominal propeller thrust at MCR at free running open water conditions. t r a 11.6.4 Blade failure load for both open and nozzle propeller, Fex P The force is acting at 0.8R in the weakest direction of the blade at the centre of the blade. For calculation of spindle torque the force is assumed to act at a spindle arm of 1/3 of the distance from the axis of blade rotation to the leading or the trailing edge, whichever is greater. The blade failure load, in kN, is: where σref = 0.6σ0.2 + 0.4σu where σu (specified maximum ultimate tensile strength) and σ0.2 (specified maximum yield or 0.2% proof strength) are representative values for the blade material. Representative in this respect means values for the considered section. These values may either be obtained by means of tests, or commonly accepted “thickness correction factors” approved by the classification society. If not available, maximum specified values shall be used. c, t, D and r are respectively the actual chord length (m), thickness (m), propeller diameter (m) and radius (m) of the cylindrical root section of the blade at the weakest section outside root fillet and typically will be at the termination of the fillet into the blade profile. Alternatively the Fex can be determined by means of FEA of the actual blade. Blade bending failure shall take place reasonably close to the root fillet end and normally not more 20% of R outside fillet. The blade bending failure is considered to occur when von Mises stress reach σref1 times 1.5 in elastic model. Guidance note: A recommended FE analysis method is given in Class Guideline, DNVGL-CG-0041. Alternative methods to the ones given in Class Guideline, DNVGL-CG-0041, may also be considered on the basis of equivalence. ---e-n-d---of---g-u-i-d-a-n-c-e---n-o-t-e--- 11.7 Machinery fastening loading conditions 11.7.1 Essential equipment and main propulsion machinery supports shall be suitable for the accelerations as indicated in as follows. Accelerations shall be considered acting independently. Rules for classification: Ships — DNVGL-RU-SHIP-Pt6Ch6. Edition October 2015 Page 166 Cold climate DNV GL AS 11.7.2 Longitudinal Impact Accelerations al 5 Maximum longitudinal impact acceleration, in m/s2, at any point along the hull girder: n o i t c e S 6 11.7.3 Vertical acceleration av r 2 e Combined vertical impact acceleration, in m/s , at any point along the hull girder: t p a h C 6 t FX = 1.3 at F.E. r = 0.2 at midships a = 0.4 at A.E. P = 1.3 at A.E. for ships conducting ice breaking astern. Intermediate values to be interpolated linearly. 11.7.4 Transverse impact acceleration at Combined transverse impact acceleration, in m/s2, at any point along hull girder: FX = 1.5 at F.E. = 0.25 at midships = 0.5 at A.E. = 1.5 at A.E. for ships conducting ice breaking astern, intermediate values to be interpolated linearly where: φ = Maximum friction angle between steel and ice, normally taken as 10°, in degrees. γ = Bow stem angle at waterline, in degrees. Δtk = Displacement at UIWL, in ktonnes. H = Distance, in m, from the water line to the point being considered. FIB = Vertical impact force, defined in [6.2]. FBow = As defined in [4.5.1]. Rules for classification: Ships — DNVGL-RU-SHIP-Pt6Ch6. Edition October 2015 Page 167 Cold climate DNV GL AS 5 12 Design – machinery n o i 12.1 Design principles t c e 12.1.1 Fatigue design in general S The propeller and shaft line components shall be designed so as to prevent accumulated fatigue failure when 6 considering the loads according to [11.3] through [11.6] using the linear elastic Palmgren-Miner’s rule. r e t p a h C The long term ice load spectrum is approximated with two-parameter Weibull distribution. 6 t 12.1.2 Propeller blades r The load spectrum for backward loads is normally expected to have a lower number of cycles than the load a spectrum for forward loads. Taking this into account in a fatigue analysis introduces complications that are P not justified considering all uncertainties involved. The blade stress amplitude distribution is therefore simplified and assumed to be as: where the Weibull shape parameter is, k = 0.75 for open propeller and k = 1.0 for nozzle propeller This is illustrated in the cumulative stress spectrum (stress exceedence diagram) in Figure 12. Number of load cycles Nice in the load spectrum per blade shall be determined according to the formula: where: Nclass= Reference number of impacts per propeller rotation speed for each ice class (table). Ice Class PC-1 PC-2 PC-3 PC-4 PC-5 PC-6 PC-7 6 6 6 6 6 6 6 Nclass 21 × 10 17 × 10 15 × 10 13 × 10 11 × 10 9 × 10 6 × 10 k1 = 1 for centre propeller = 2 for wing propeller = 3 for pulling propeller (wing and centre) = For pulling bow propellers number of load cycles is expected to increase in range of 10 times k2 = 0.8 - f when f < 0 = 0.8 - 0.4·f when 0 ≤ f ≤ 1 = 0.6 - 0.2·f when 1 < f ≤ 2.5 Rules for classification: Ships — DNVGL-RU-SHIP-Pt6Ch6. Edition October 2015 Page 168 Cold climate DNV GL AS = 0.1 when f > 2.5 5 where the immersion function f is: n o i t c e S 6 where: r e t p a h C = Depth of the propeller centreline at the minimum ballast waterline in ice (LIWL) of the ship, in m. 6 12.1.3 Applicable loads in propulsion line components t The strength of the propulsion line components shall be designed r a a) for maximum loads in [11.3] and [11.4] (for open and ducted propellers respectively) P b) such that the plastic bending of a propeller blade shall not cause damages in other propulsion line components c) with fatigue strength as determined by the criteria in [12.5] with the following ice load spectrum The Weibull shape parameter is k = 1.0 for both open and ducted propeller torque and bending forces. The load distribution is an accumulated load spectrum (load exceedence diagram). This is illustrated by the example in the Figure 13. Figure 12 Ice load distribution for ducted and open propeller Rules for classification: Ships — DNVGL-RU-SHIP-Pt6Ch6. Edition October 2015 Page 169 Cold climate DNV GL AS 5 n o i t c e S 6 r e t p a h C 6 Figure 13 The total number of load cycles in the load spectrum is determined as: Z·N t ice. r a P 12.2 Propeller blade design 12.2.1 Maximum blade stresses Blade stresses (equivalent and principal stresses) shall be calculated using the backward and forward loads given in section [11.3] and [11.4]. The stresses shall be calculated with recognised and well documented FE- analysis. Guidance note: A recommended FE analysis method is given in Class Guideline, DNVGL-CG-0041. Alternative methods to the ones given in Class Guideline, DNVGL-CG-0041, may also be considered on the basis of equivalence. ---e-n-d---of---g-u-i-d-a-n-c-e---n-o-t-e--- The stresses on the blade shall not exceed the allowable stresses σall for the blade material given below. Calculated blade equivalent stress for maximum ice load shall comply with the following: σcalc < σall = σref /S S = 1.5 σref = Reference stress, defined as: σref = 0.7σu or σref = 0.6σ0.2 + 0.4σu whichever is less where σu and σ0.2 are minimum specified values for the blade material according to approved maker’s specification. 12.3 Fatigue design of propeller blades 12.3.1 Propeller blades shall be designed so as to prevent accumulated fatigue when considering the loads according to [12.1.2] and using the Miner’s rule. Guidance note: A recommended fatigue analysis method is given in Class Guideline, DNVGL-CG-0041. Alternative methods to the ones given in Class Guideline, DNVGL-CG-0041, may also be considered on the basis of equivalence. Rules for classification: Ships — DNVGL-RU-SHIP-Pt6Ch6. Edition October 2015 Page 170 Cold climate DNV GL AS ---e-n-d---of---g-u-i-d-a-n-c-e---n-o-t-e--- 5 0 8 12.3.2 The S-N curve characteristics are based on two slopes, the first slope 4.5 is from 10 to 10 load n 8 cycles; the second slope 10 is above 10 load cycles. o i t — The maximum allowable stress is limited by σref/S c e — The fatigue strength σFat-E7 is the fatigue limit at 10 million load cycles. S The geometrical size factor (K ) is: size 6 r e t p a h Where t = actual blade thickness at considered section and a is given in Table 22 C The mean stress effect (Kmean) is: 6 t r a P The fatigue limit for 10 million load cycles is then: where S is the safety factor S = 1.5 The S-N curve is extended by using the first slope (4.5) to 100 million load cycles due to the variable loading effect (stress interaction effect). Table 22 Mean fatigue strength σFat-E7 for different material types Bronze and brass (a = 0.10) Stainless steel (a = 0.05) Mn-Bronze, CU1 (high tensile brass) 80 MPa Ferritic (12Cr 1Ni) 120 MPa Mn-Ni-Bronze, CU2 (high tensile brass) 80 MPa Martensitic (13Cr 4Ni/13Cr 6Ni) 150 MPa Ni-Al-Bronze, CU3 120 MPa Martensitic (16Cr 5Ni) 165 MPa Mn-Al-Bronze, CU4 105 MPa Austenitic (19Cr 10Ni) 130 MPa Alternatively, σFat-E7 can be defined from fatigue test results from approved fatigue tests at 50% survival probability and stress ratio R = -1, ref. Rules Pt.4 Ch.5 Sec.1 [2.1.1]. 12.4 Blade flange, bolts and propeller hub and CP Mechanism 12.4.1 The blade bolts, the cp mechanism, the propeller boss, and the fitting of the propeller to the propeller shaft shall be designed to withstand the maximum and fatigue design loads, as defined in I. The safety factor against yielding shall be greater than 1.3 and that against fatigue greater than 1.5. In addition, the safety factor for loads resulting from loss of the propeller blade through plastic bending as defined in [11.6.4] shall be greater than 1 against yielding. Guidance note: Rules for classification: Ships — DNVGL-RU-SHIP-Pt6Ch6. Edition October 2015 Page 171 Cold climate DNV GL AS A recommended fatigue analysis method is given in Class Guideline, DNVGL-CG-0041. Alternative methods to the ones given in Class 5 Guideline, DNVGL-CG-0041, may also be considered on the basis of equivalence. ---e-n-d---of---g-u-i-d-a-n-c-e---n-o-t-e--- n o i t 12.4.2 Blade bolts shall withstand following bending moment, in kNm, considered around bolt pitch circle, or c an other relevant axis for not circular joints, parallel to considered root section with a safety factor of 1.0: e S 6 r e t where: p a r = Radius to the bolt plan, in m. bolt h C 12.4.3 Blade bolt pre-tension shall be sufficient to avoid separation between mating surfaces with maximum forward and backward ice loads in [11.3.1] - [11.3.2] and [11.4.1] - [11.4.2] (open and ducted 6 respectively). t r a 12.4.4 Separate means, e.g. dowel pins, have to be provided in order to withstand a spindle torque resulting P from blade failure ([11.6.4]) Qsex or ice interaction Qsmax ([11.3.3]), whichever is greater. A safety factor S of 1.0 is required. The minimum diameter of the pins, in mm, shall be taken as: where: PCD = Pitch circle diameter, in mm. i = Number of pins. Qs = Max(Qsmax; Qsex ) - Qfr1 - Qfr2, in kNm. σ0.2 = Yield strength of dovel pin material. Qsex = , in kNm. Qfr1 = Friction torque in blade bearings caused by the reaction forces due to Fex. Qfr2 = Friction between connected surfaces resulting from blade bolt pretension forces. ℓex = Maximum of distance from spindle axis to the leading, or trailing edge at radius 0,8R. Coefficient of = 0.15 may normally be applied in calculation of Qfr1,2. friction 12.4.5 Components of CP mechanisms shall be designed to withstand the blade failure spindle torque Qsex and maximum ice spindle torque. The blade failure spindle torque, Qsex , shall not lead to any consequential damages. Fatigue strength shall be considered for parts transmitting the spindle torque from blades to a servo system considering ice spindle torque acting on one blade. The maximum amplitude, in kNm, is defined as: Rules for classification: Ships — DNVGL-RU-SHIP-Pt6Ch6. Edition October 2015 Page 172 Cold climate DNV GL AS Provided that calculated stresses duly considering local stress concentrations are less than yield strength, 5 or maximum 70% of σu of respective materials, detailed fatigue analysis is not required. In opposite case components shall be analysed for cumulative fatigue. n o i t 12.4.6 Design pressure for servo system shall be taken as a pressure caused by Qsmax or Qsex when not c protected by relief valves, reduced by relevant friction losses in bearings caused by the respective ice loads. e Design pressure shall in any case be less than relief valve set pressure. S 6 12.5 Propulsion line components r e t 12.5.1 Propeller fitting to the shaft p A. Keyless cone mounting a h o The friction capacity (at 0 C) shall be at least 2.0 times the highest peak torque Tpeak, in kNm, as determined C in [11.6] without exceeding the permissible hub stresses. 6 The necessary surface pressure, in MPa, can be determined as: t r a P where: μ = 0.14 for steel-steel, = 0.13 for steel-bronze DS = Is the shrinkage diameter at mid-length of taper, in m. ℓ = Is the effective length of taper, in m. Above friction coefficients may be increased by 0.04 if glycerine is used in wet mounting B. Key mounting Key mounting is not permitted. C. Flange mounting I = The flange thickness shall be at least 25% of the shaft diameter. II = Any additional stress raisers such as recesses for bolt heads shall not interfere with the flange fillet unless the flange thickness is increased correspondingly. III = The flange fillet radius shall be at least 10% of the shaft diameter. IV = The diameter of ream fitted (light press fit) bolts shall be chosen so that the peak torque does not cause shear stresses beyond 30% of the yield strength of the bolts. V = The bolts shall be designed so that the blade failure load Fex ([11.6.4]) does not cause yielding. 12.5.2 Propeller shaft The propeller shaft shall be designed to fulfill the following: A. The blade failure load Fex ([11.6.4]) applied parallel to the shaft (forward or backwards) shall not cause yielding. Bending moment need not to be combined with any other loads.The diameter in way of the aft stern tube bearing, in mm, shall not be less than: Rules for classification: Ships — DNVGL-RU-SHIP-Pt6Ch6. Edition October 2015 Page 173 Cold climate DNV GL AS 5 n o i t c e S where: 6 σy = Minimum specified yield or 0.2% proof strength of the propeller shaft material, in MPa. r = Shaft diameter, in mm. e d t di = Shaft inner diameter, in mm. p a Forward from the aft stern tube bearing the diameter may be reduced based on direct calculation of actual h bending moments, or by the assumption that the bending moment caused by Fex is linearly reduced to 50% C at the next bearing and in front of this linearly to zero at third bearing. 6 t Bending due to maximum blade forces Fb and Ff have been disregarded since the resulting stress levels are r much below the stresses due to the blade failure load. a P B. The stresses due to the peak torque Tpeak, in kNm, shall have a minimum safety factor of 1.5 against yielding in plain sections and 1.0 in way of stress concentrations in order to avoid bent shafts. Minimum diameter, in mm, of: plain shaft: notched shaft: where αt is the local stress concentration factor in torsion. Notched shaft diameter shall in any case not be less than the required plain shaft diameter. C. The torque amplitudes with the foreseen number of cycles shall be used in an accumulated fatigue evaluation with the safety factors as defined below. Guidance note: A recommended fatigue analysis method is given in Class Guideline, DNVGL-CG-0041, with further references to the DNVGL-CG-0038. Alternative methods to the ones given in Class Guideline, DNVGL-CG-0041, may also be considered on the basis of equivalence. ---e-n-d---of---g-u-i-d-a-n-c-e---n-o-t-e--- D. For plants with reversing direction of rotation the stress range Δτ·αt, in MPa, resulting from forward Tpeakf to astern Tpeakb shall not exceed twice the yield strength (in order to avoid stress-strain hysteresis loop), in MPa, with a safety factor of 1.5, i.e.: Rules for classification: Ships — DNVGL-RU-SHIP-Pt6Ch6. Edition October 2015 Page 174 Cold climate DNV GL AS 5 n o i t c The fatigue strengths σF and τF (3 million cycles) of shaft materials may be assessed on the basis of the e material’s yield or 0.2% proof strength, in MPa, as: S 6 r e t This is valid for small polished specimens (no notch) and reversed stresses, see “VDEH 1983 Bericht Nr. p a ABF11 Berechnung von Wöhlerlinien für Bauteile aus Stahl”. h C The high cycle fatigue (HCF) shall be assessed based on the above fatigue strengths, notch factors (i.e. geometrical stress concentration factors and notch sensitivity), size factors, mean stress influence and the 6 required safety factor of 1.5. t r The low cycle fatigue (LCF) representing 103 cycles shall be based on the lower value of either half of the a P stress range criterion (see D) or the smaller value of yield or 0.7 of tensile strength/√3. Both criteria utilise a safety factor of1.5. The LCF and HCF as given above represent the upper and lower knees in a stress-cycle diagram. Since the required safety factors are included in these values, a Miner sum of unity is acceptable. 12.5.3 Intermediate shafts The intermediate shafts shall be designed to fulfil the following: A. The stresses due to the peak torque Tpeak, in kNm, shall have a minimum safety factor of 1.5 against yielding in plain sections and 1.0 in way of stress concentrations in order to avoid bent shafts. Minimum diameter, in mm, of: plain shaft: notched shaft: where αt is the local stress concentration factor in torsion. Notched shaft diameter shall in any case not be less than the required plain shaft diameter. B. The torque amplitudes with the foreseen number of cycles shall be used in an accumulated fatigue evaluation with the safety factors as defined below. Guidance note: A recommended fatigue analysis method is given in Class Guideline, DNVGL-CG-0041. Alternative methods to the ones given in Class Guideline, DNVGL-CG-0041, may also be considered on the basis of equivalence. Rules for classification: Ships — DNVGL-RU-SHIP-Pt6Ch6. Edition October 2015 Page 175 Cold climate DNV GL AS ---e-n-d---of---g-u-i-d-a-n-c-e---n-o-t-e--- 5 C. For plants with reversing direction of rotation the stress range Δτ·αt, in MPa, resulting from forward Tpeakf n to astern Tpeakb shall not exceed twice the yield strength (in order to avoid hysteresis), in MPa, with a safety o factor of 1.5, i.e.: i t c e S 6 r The fatigue strengths σF and τF (3 million cycles) of shaft materials may be assessed on the basis of the e material’s yield or 0.2% proof strength, in MPa, as: t p a h C 6 This is valid for small polished specimens (no notch) and reversed stresses, see “VDEH 1983 Bericht Nr. t ABF11 Berechnung von Wöhlerlinien für Bauteile aus Stahl”. r The high cycle fatigue (HCF) shall be assessed based on the above fatigue strengths, notch factors (i.e. a geometrical stress concentration factors and notch sensitivity), size factors, mean stress influence and the P required safety factor of 1.5. The low cycle fatigue (LCF) representing 103 cycles shall be based on the lower value of either half of the stress range criterion (see C) or the smaller value of yield or 0.7 of tensile strength/√3. Both criteria utilise a safety factor of 1.5. The LCF and HCF as given above represent the upper and lower knees in a stress-cycle diagram. Since the required safety factors are included in these values, a Miner sum of unity is acceptable. 12.5.4 Shaft connections A. Shrink fit couplings (keyless) The friction capacity shall be at least 1.8 times the highest peak torque Tpeak as determined in [11.6.2] without exceeding the permissible hub stresses. The necessary surface pressure, in MPa, can be determined as: where: μ = Coefficient of friction = 0.14 for steel to steel with oil injection (= 0.18 if glycerine injection). DS = Is the shrinkage diameter at mid-length of taper, in m. ℓ = Is the effective length of taper, in m. B. Key mounting Key mounting is not permitted. C. Flange mountingg I = The flange thickness shall be at least 20% of the shaft diameter. II = Any additional stress raisers such as recesses for bolt heads shall not interfere with the flange fillet unless the flange thickness is increased correspondingly. Rules for classification: Ships — DNVGL-RU-SHIP-Pt6Ch6. Edition October 2015 Page 176 Cold climate DNV GL AS III = The flange fillet radius shall be at least 8% of the shaft diameter. 5 IV = The diameter of ream fitted (light press fit) bolts or pins shall be chosen so that the peak torque does not cause shear stresses beyond 30% of the yield strength of the bolts or pins. n = The bolts shall be designed so that the blade failure load ([11.6.4]) in backwards direction does not o V i cause yielding. t c e 12.5.5 Gear transmissions S A. Shafts 6 Shafts in gear transmissions shall meet the same safety level as intermediate shafts, but where relevant, bending stresses and torsional stresses shall be combined, e.g. by von Mises. r e Guidance note: t p A recommended fatigue analysis method is given in Class Guideline, DNVGL-CG-0041. Alternative methods to the ones given in Class a Guideline, DNVGL-CG-0041, may also be considered on the basis of equivalence. h ---e-n-d---of---g-u-i-d-a-n-c-e---n-o-t-e--- C Maximum permissible deflection in order to maintain sufficient tooth contact pattern shall be considered for 6 the relevant parts of the gear shafts. t B. Gearing r a The gearing shall fulfil following 3 acceptance criteria: P 1) tooth root fracture 2) pitting of flanks 3) scuffing. In addition to above 3 criteria subsurface fatigue may need to be considered. Common for all criteria is the influence of load distribution over the face width. All relevant parameters shall be considered, such as elastic deflections (of mesh, shafts and gear bodies), accuracy tolerances, helix modifications, and working positions in bearings (especially for twin input single output gears). The load spectrum (see [12.1.3]) may be applied in such a way that the numbers of load cycles for the output wheel are multiplied by a factor of (number of pinions on the wheel / number of propeller blades Z). For pinions and wheels with higher speed the numbers of load cycles are found by multiplication with the gear ratios. The peak torque, Tpeak, is also to be considered. Guidance note: The acceptance criteria for calculation assessment are given below. They refer to calculation methods as given in Class Guideline, DNVGL-CG-0036, comprising information on calculation of tooth root strength (root fractures), flank surface durability (pitting, spalling, case crushing and tooth fractures starting from the flank), scuffing and subsurface fatigue. Alternative methods to the ones given in Class Guideline, DNVGL-CG-0036, may also be considered on the basis of equivalence. ---e-n-d---of---g-u-i-d-a-n-c-e---n-o-t-e--- Tooth root safety shall be assessed against the peak torque, torque amplitudes (with the pertinent average torque) as well as the ordinary loads (free water running) by means of accumulated fatigue analyses. The resulting safety factor shall be at least 1.5. The safety against pitting shall be assessed in the same way as tooth root stresses, but with a minimum resulting safety factor of 1.2. The scuffing safety (flash temperature method – see Class Guideline, DNVGL-CG-0036) based on the peak torque shall be at least 1.2 when the FZG class of the oil is assumed one stage below specification. The safety against subsurface fatigue of flanks for surface hardened gears (oblique fracture from active flank to opposite root) shall be assessed at the discretion of each society. C. Bearings See section [12.5.9]. 12.5.6 Clutches Clutches shall have a static friction torque of at least 1.3 times the peak torque and dynamic friction torque 2/3 of the static. Rules for classification: Ships — DNVGL-RU-SHIP-Pt6Ch6. Edition October 2015 Page 177 Cold climate DNV GL AS Emergency operation of clutch after failure of e.g. operating pressure shall be made possible within 5 reasonably short time. If this is arranged by bolts, it shall be on the engine side of the clutch in order to ensure access to all bolts by turning the engine. n o i 12.5.7 Elastic couplings t There shall be a separation margin of at least 20% between the peak torque and the torque where any twist c limitation is reached. e S The torque amplitude (or range Δ) shall not lead to fatigue cracking, i.e. exceeding the permissible vibratory 6 torque. The permissible torque may be determined by interpolation in a log-log torque-cycle diagram where 6 TKmax1 respectively ΔTKmax refer to 50,000 cycles and TKV refer to 10 cycles. See illustration in Figure 14, r e Figure 15 and Figure 16. t p a h C 6 t r a P Figure 14 Figure 15 Figure 16 Rules for classification: Ships — DNVGL-RU-SHIP-Pt6Ch6. Edition October 2015 Page 178 Cold climate DNV GL AS 12.5.8 Crankshafts 5 Special considerations apply for plants with large inertia, e.g. flywheel, tuning wheel or PTO, in the non- driving end of the engine. n o i 12.5.9 Bearings t All shaft bearings shall be designed to withstand the propeller blade ice interaction loads according to [11.3] c and [11.4]. For the purpose of calculation the shafts are assumed to rotate at rated speed. Reaction forces e S due to the response torque, e.g. in gear transmissions, shall be considered. 6 Additionally the aft stern tube bearing as well as the next shaft-line bearing shall withstand Fex as given in [11.6], in such a way that the ship can maintain operational capability. r e Rolling bearings shall have a L10a lifetime of at least 40 000 hours according to ISO-281. t p Thrust bearings and their housings shall be designed to withstand maximum response thrust [11.6] and the a force resulting from the blade failure force Fex. For the purpose of calculation except for Fex the shafts are h assumed to rotate at rated speed. For pulling propellers special consideration shall be given to loads from ice C interaction on propeller hub. 6 12.5.10 Seals t r Basic requirements for seals: a A. Seals shall prevent egress of pollutants, and be suitable for the operating temperatures. Contingency plans P for preventing the egress of pollutants under failure conditions shall be documented. B. Seal shall be of type approved type or otherwise of proven design. 12.6 Azimuth main propulsion 12.6.1 In addition to the above requirements, special consideration shall be given to those loading cases which are extraordinary for propulsion units when compared with conventional propellers. The estimation of loading cases has to reflect the way of operation of the ship and the thrusters. In this respect, for example, the loads caused by the impacts of ice blocks on the propeller hub of a pulling propeller have to be considered. Furthermore, loads resulting from the thrusters operating at an oblique angle to the flow have to be considered. The steering mechanism, the fitting of the unit, and the body of the thruster shall be designed to withstand the loss of a blade without damage. The loss of a blade shall be considered for the propeller blade orientation which causes the maximum load on the component being studied. Typically, top-down blade orientation places the maximum bending loads on the thruster body. 12.6.2 Azimuth thrusters shall also be designed for estimated loads due to thruster body/ice interaction as per sub-section E. The thruster body has to stand the loads obtained when the maximum ice blocks, which are given in [11.2.1], strike the thruster body when the ship is at a typical ice operating speed. In addition, the design situation in which an ice sheet glides along the ship’s hull and presses against the thruster body should be considered. The thickness of the sheet should be taken as the thickness of the maximum ice block entering the propeller, as defined in [11.2]. 12.6.3 Design criteria for azimuth propulsors Azimuth propulsors shall be designed for following loads: 1) Ice pressure on strut based on defined location area of the strut / ice interaction as per [12.5]. 2) Ice pressure on pod based on defined location area of thruster body / ice interaction as per subsection [12.5]. 3) Plastic bending of one propeller blade in the worst position (typically top-down) without consequential damages to any other part 4) Steering gear design torque, in kNm, shall be minimum 60% of steering torque expected at propeller ice milling condition defined as Tmax TSG = 0.6(Tmax / 0.8R) ℓ where ℓ is distance from the propeller plane to steering (azimuth) axis, in m. Rules for classification: Ships — DNVGL-RU-SHIP-Pt6Ch6. Edition October 2015 Page 179 Cold climate DNV GL AS 5) Steering gear shall be protected by effective means limiting excessive torque caused by: 5 a) Ice milling torque exceeding design torque and leading to rotation of unit n b) Torque caused by plastic bending of one propeller blade in the worse position (related to steering o i gear) and leading to rotation of the unit. t 6) Steering gear shall be ready for operation after above load, 5)a) or 5)b) has gone. c e S 12.7 Steering system 6 r 12.7.1 The effective holding torque of the rudder actuator, at safety valve set pressure, is obtained by e multiplying the open water requirement at design speed (maximum 18 knots) by following factors: t p Ice Class PC-1 PC-2 PC-3 PC-4 PC-5 PC-6 PC-7 a h Factor 5 5 3 3 3 2 1.5 C 6 The holding torque shall be limited to the actual twisting capacity of the rudder stock calculated at its yield t strength (ref. Pt.4 Ch.10) r a 12.7.2 The rudder actuator shall be protected by torque relief arrangements, assuming the following turning P speeds [deg/s] without undue pressure rise (ref. Pt.4 Ch.10 for undue pressure rise): Ice Class PC-1 and 2 PC-3 to 5 PC-6 and 7 Turning speeds [deg/s] 8 6 4 12.7.3 Additional fast acting torque relief arrangements (acting at 15% higher pressure than set pressure of safety valves in [12.7.2] shall provide effective protection of the rudder actuator in case of the rudder is pushed rapidly hard over against the stops assuming following turning speeds [deg/s]. Ice Class PC-1 and 2 PC-3 to 5 PC-6 and 7 Turning speeds [deg/s] 40 20 10 The arrangement shall be so that steering capacity can be speedily regained. 12.8 Prime movers 12.8.1 Engines shall be capable of being started and running the propeller in bollard condition. 12.8.2 Propulsion plants with CP propeller shall be capable being operated even in case with the CP system in full pitch as limited by mechanical stoppers. 12.8.3 Provisions shall be made for heating arrangements to ensure ready starting of the cold emergency power units at an ambient temperature applicable to the polar class of the ship. 12.8.4 Emergency power units shall be equipped with starting devices with a stored energy capability of at least three consecutive starts at the design temperature in [11.1] above The source of stored energy shall be protected to preclude critical depletion by the automatic starting system, unless a second independent means of starting is provided. A second source of energy shall be provided for an additional three starts within 30 min., unless manual starting can be demonstrated to be effective. Rules for classification: Ships — DNVGL-RU-SHIP-Pt6Ch6. Edition October 2015 Page 180 Cold climate DNV GL AS 5 12.9 Auxiliary systems n o 12.9.1 Machinery shall be protected from the harmful effects of ingestion or accumulation of ice or snow. i t Where continuous operation is necessary, means should be provided to purge the system of accumulated ice c or snow. e S 12.9.2 Means should be provided to prevent damage due to freezing, to tanks containing liquids. 6 12.9.3 Vent pipes, intake and discharge pipes and associated systems shall be designed to prevent blockage r e due to freezing or ice and snow accumulation. t p a 12.10 Sea inlets, cooling water systems and ballast tanks h C 12.10.1 Cooling water systems for machinery that are essential for the propulsion and safety of the ship, 6 including sea chests inlets, shall be designed for the environmental conditions applicable to the ice class. t r 12.10.2 At least two sea chests shall be arranged as ice boxes for class PC(1) to PC(5) inclusive. The a 3 calculated volume for each of the ice boxes shall be at least 1 m for every 750 kW of the total installed P power. For PC(6) and PC(7) there shall be at least one ice box located preferably near centre line. 12.10.3 Ice boxes shall be designed for an effective separation of ice and venting of air. 12.10.4 Sea inlet valves shall be secured directly to the ice boxes. The valve shall be a full bore type. 12.10.5 Ice boxes and sea bays shall have vent pipes and shall have shut off valves connected direct to the shell. 12.10.6 Means shall be provided to prevent freezing of sea bays, ice boxes, ship side valves and fittings above the load water line. 12.10.7 Efficient means shall be provided to re-circulate cooling seawater to the ice box. Total sectional area of the circulating pipes shall not be less than the area of the cooling water discharge pipe. 12.10.8 Detachable gratings or manholes shall be provided for ice boxes. Manholes shall be located above the deepest load line. Access shall be provided to the ice box from above. 12.10.9 Openings in ship sides for ice boxes shall be fitted with gratings, or holes or slots in shell plates. The net area through these openings shall be not less than 5 times the area of the inlet pipe. The diameter of holes and width of slot in shell plating shall be not less than 20 mm. Gratings of the ice boxes shall be provided with a means of clearing. Clearing pipes shall be provided with screw-down type non return valves. 12.11 Ballast tanks 12.11.1 Efficient means shall be provided to prevent freezing in fore and after peak tanks and wing tanks located above the water line and where otherwise found necessary. 12.12 Ventilation systems 12.12.1 The air intakes for machinery and accommodation ventilation shall be located on both sides of the ship. 12.12.2 Accommodation and ventilation air intakes shall be provided with means of heating. Rules for classification: Ships — DNVGL-RU-SHIP-Pt6Ch6. Edition October 2015 Page 181 Cold climate DNV GL AS 12.12.3 The temperature of inlet air provided to machinery from the air intakes shall be suitable for the safe 5 operation of the machinery n o i 12.13 Alternative design t c 12.13.1 As an alternative, a comprehensive design study may be submitted and may be requested to be e S validated by an agreed test programme. 6 r 13 Stability and watertight integrity e t p 13.1 General a h C 13.1.1 Ships with a length LLL of 24 meters and above and class notation PC(7) to PC(1) shall comply with the requirements of Pt.3 Ch.15 and IMO Resolution A.1024(26) “Guidelines for Ships Operating in Polar 6 Waters” Chapter 3 “Subdivision and Stability” as well as the requirements of this subsection. t r 13.1.2 For ships with PC(6) and PC(7) not carrying any polluting or hazardous cargoes, damage may be a P assumed to be confined between watertight bulkheads, except where such bulkheads are spaced at less than the damage dimension. 13.2 Intact stability 13.2.1 The initial metacentric height GM shall not be less than 0.5 m. 13.3 Requirements to watertight integrity 13.3.1 As far as practicable, tunnels, ducts or pipes which may cause progressive flooding in case of damage, shall be avoided in the damage penetration zone. If this is not possible, arrangements shall be made to prevent progressive flooding to volumes assumed intact. Alternatively, these volumes shall be assumed flooded in the damage stability calculations. 13.3.2 The scantlings of tunnels, ducts, pipes, doors, staircases, bulkheads and decks, forming watertight boundaries, shall be adequate to withstand pressure heights corresponding to the deepest equilibrium waterline in damaged condition. Rules for classification: Ships — DNVGL-RU-SHIP-Pt6Ch6. Edition October 2015 Page 182 Cold climate DNV GL AS APPENDIX A GUIDELINES FOR STRENGTH ANALYSIS OF THE A PROPELLER BLADE USING FINITE ELEMENT METHOD x i d 1 Guidelines for strength analysis of the propeller blade using finite n e element method p p A 1.1 Requirements for FE model 6 1.1.1 The objective of the stress analysis of ice-strengthened propeller blades shall make sure that the r designed propeller blade has an acceptable margin of safety against both ultimate and fatigue strength at the e t design loads. p The typical locations on the propeller blades at which the highest stresses caused by ice loads occur are the a fillet at the root of the blade in the case of all propeller types and the section next to the tip load area in the h case of skewed propellers. C The requirement for the finite element model is that it is able to represent the complex curvilinear geometry 6 and the thickness variation of the blade and also the geometry of the fillet at the root of the blade, in order t to represent the complex three-dimensional stress state of the structure and to represent the local peak r stresses needed to assess the fatigue strength of the structure with acceptable accuracy. The load of the a propeller blade is dominated by bending, leading to non-constant stress distribution over the thickness of the P blade. The model should also be able to represent the stress distribution over the thickness of the blade. A conventional stress analysis approach to propeller blades utilising beam theory, although capable of dealing with warping stresses, or an approach utilising coarse shell elements with a rough representation of the thickness variation of the blade do not lead to acceptable accuracy in the stress analyses of ice-strengthened propeller blades. 1.2 Good engineering practice for FE analysis 1.2.1 The use of solid elements is highly recommended for determining the stress distribution of the propeller blades. The use of a very dense parabolic tetrahedron mesh is recommended. Parabolic hexahedron solid elements may also be used, but hexahedra require considerably greater modelling effort. Linear elements and, especially, linear tetrahedrals should not be used in stress analysis. As a rule of thumb, a minimum of two parabolic solid elements should be used over the thickness of the blade in the thinnest regions of the blade. Near the root region of the blade, where the geometry changes rapidly, the element size used should be chosen to be such that the local peak stress used in the fatigue assessment is obtained with good accuracy. Additional geometric details which have a significant effect on the maximum peak stress at the root fillet should also be taken into account in the model, e.g. bolt holes located close to the root fillet. Well-shaped elements are a prerequisite for the stress analyses. The element formulation to be used should be chosen so as to be such that no locking, hour-glassing etc. phenomena occur. A typical parabolic tetrahedron mesh of a propeller blade used in the verification studies is presented in Figure 1 as an example. Rules for classification: Ships — DNVGL-RU-SHIP-Pt6Ch6. Edition October 2015 Page 183 Cold climate DNV GL AS A x i d n e p p A 6 r e t p a h C 6 t r a P Figure 1 A typical parabolic tetrahedron mesh of a propeller blade Shell elements may be used in the stress analyses of propeller blades, but the accuracy of the modelling approach has to be proven by measurements or extensive verification calculations covering the thickness, dimensional, and geometrical variations of the propeller blade product range to be manufactured. For example, extreme sizes and an adequate number of intermediate sizes of the propeller blade product range should be used in verification calculations or measurements. The peak stress obtained using the shell element approach has to be within acceptable accuracy and the boundary conditions shall not cause significant disturbance in the peak stresses. The root fillet geometry has to be considered in the peak stress state used in the stress analysis. The modelling of the tip region is difficult. Thus, it is allowed, for example, to finish discretisation at the 0.975 chord and to make an artificial chord at the tip. The shell element formulation to be used should be chosen so as to be such that no locking, hour-glassing etc. phenomena occur. 1.3 Boundary conditions 1.3.1 The boundary conditions of the blade model should be given at an adequate distance from the peak stress location in order to ensure that the boundary condition has no significant effect on the stress field used in the stress analysis. 1.4 Applied pressure loads 1.4.1 The pressure loads applied on the finite element model can be given either in the normal direction of the curved blade surface or alternatively as a directional pressure load. The normal pressure approach - see Figure 2 - leads to a loss of the net applied transversal load as a result of the highly curved surface near the edge of the propeller blade. Whichever approach is used, it should be ensured that the total force determined in the particular load case is applied on the model. In the normal pressure case, this can be done by scaling the load or, alternatively, by scaling the resulting stresses. The directional pressure is better suited to propeller blade stress analyses. The pressure can be given on a surface in a direction defined using, for example, a local coordinate system; see Figure 3. Rules for classification: Ships — DNVGL-RU-SHIP-Pt6Ch6. Edition October 2015 Page 184 Cold climate DNV GL AS A x i d n e p p A 6 r e t p a h C 6 t r a P Figure 2 First alternative. One possible way to apply the pressure load to the propeller blade. If the pressure load is given in the normal direction of the highly curved blade surface, the resulting net applied load will be less than the intended load and should be scaled appropriately. Rules for classification: Ships — DNVGL-RU-SHIP-Pt6Ch6. Edition October 2015 Page 185 Cold climate DNV GL AS A x i d n e p p A 6 r e t p a h C 6 t r a P Figure 3 Second alternative. If the pressure load is given in a fixed direction, the net applied load is directly the intended load. Rules for classification: Ships — DNVGL-RU-SHIP-Pt6Ch6. Edition October 2015 Page 186 Cold climate DNV GL AS DNV GL Driven by our purpose of safeguarding life, property and the environment, DNV GL enables organizations to advance the safety and sustainability of their business. We provide classification and technical assurance along with software and independent expert advisory services to the maritime, oil and gas, and energy industries. We also provide certification services to customers across a wide range of industries. Operating in more than 100 countries, our 16 000 professionals are dedicated to helping our customers make the world safer, smarter and greener. SAFER, SMARTER, GREENER