DNV Ship Rules Pt.5 Ch.1

RULES FOR CLASSIFICATION OF

SHIPS

NEWBUILDINGS

SPECIAL SERVICE AND TYPE ADDITIONAL CLASS

PART 5 CHAPTER 1

SHIPS FOR NAVIGATION IN ICE JULY 2006

CONTENTS PAGE

Sec. 1 General Requirements ...... 5 Sec. 2 Basic Ice Strengthening...... 6 Sec. 3 Ice Strengthening for the Northern Baltic ...... 8 Sec. 4 Vessels for Arctic and Ice Breaking Service ...... 19 Sec. 5 Sealers ...... 35 Sec. 6 Winterization ...... 36 Sec. 7 DAT(-X°C) ...... 38

DET NORSKE VERITAS Veritasveien 1, NO-1322 Høvik, Norway Tel.: +47 67 57 99 00 Fax: +47 67 57 99 11 CHANGES IN THE RULES

General sions has been undertaken. Previous Fig.4, now Fig.3, has been revised accordingly. The present edition of the rules includes additions and amendments — In item B201, additional members have been categorized. decided by the Board in June 2006 and supersedes the January 2006 — In item D400, correction factors for local ice pressures have been edition of the same chapter. revised based on experience and work related to IACS Polar The rule changes come into force as indicated below. Code development. The factors have been revised from 0.25 for bottom area to a differentiation of 0.20 for vessels with notation This chapter is valid until superseded by a revised chapter. Supple- ICEBREAKER or POLAR, and 0.10 for vessels with notation ments will not be issued except for minor amendments and an updated ICE only. Differentiation has also been introduced keeping 1.0 list of corrections presented in Pt.0 Ch.1 Sec.3. Pt.0 Ch.1 is normally for the stem area for vessels with notation ICEBREAKER or revised in January and July each year. POLAR, and introducing 0.8 for vessels with ICE notation only, Revised chapters will be forwarded to all subscribers to the rules. fitted with pod or thruster propulsion units. Buyers of reprints are advised to check the updated list of rule chap- — In item F302, the me-factors in Table F1 have been changed for ters printed in Pt.0 Ch.1 Sec.1 to ensure that the chapter is current. balancing the required moment capacity to be generally consistent with that for longitudinal stiffeners. — A new sub-section element G700 has been introduced with basic rules for dimensioning of podded propulsors and azimuth thrust- Main changes coming into force 1 January 2007 ers, including supporting structure. Over the last few years there has been a rapid technological shift in the design of relevant ves- • Sec.1 General Requirements sels, a new standard practice having evolved which now needs to Sec.2 Basic Ice Strengthening be implemented in the rules. σ — In item Sec.1 B101, the definition text of F has been modified. — Sec.1 and Sec.2 have been modified to cover a new additional, • Sec.6 Winterization basic class notation ICE-E. As a consequence, the notation ICE- — This section has been amended to make the requirements for CP C becomes an intermediate notation between the ICE-1C and the propellers, electric propulsion and stainless steel propellers ap- ICE-E notations. plicable to vessels with Winterized Arctic notation instead of vessels with Winterized notation. As a consequence, item B102 • Sec.3 Ice Strengthening for the Northern Baltic and item B103 have been deleted and relocated as item E102 and — Item D301 has been modified so that m1 = 12 has been changed item E103. Also, sub-section element E300 has been deleted and to m1 = 11 in the last list item. Further, under item D402, the first item E301 has been moved to E104. paragraph of list item 3) has been replaced by: ° The web thickness of the frames need not exceed one half of the • Sec.7 DAT(-X C) thickness of the shell plating, calculated for a frame spacing of —The DAT(-XºC) requirements, previously found in Sec.4, have 0.45 m, assuming the yield stress of the plate not more than that been collected and made more visible in a separate new section, used for the frame, minimum 9 mm. Sec.7. The reason for the change is to align the rules with the new guidelines of the Finnish Maritime Authorities. • Sec.4 Vessels for Arctic and Ice Breaking Service Corrections and Clarifications — In item A403 (previous item A405), the upper transition area def- In addition to the above stated rule requirements, a number of correc- initions have been removed. A general revision of vertical exten- tions and clarifications have been made in the existing rule text.

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CONTENTS

SEC. 1 GENERAL REQUIREMENTS ...... 5 I. Special Arrangement and Strengthening Aft ...... 14 I 100 Stern ...... 14 A. Classification...... 5 I 200 Rudder and steering arrangements ...... 14 A 100 Application...... 5 A 200 Class notations ...... 5 J. Machinery ...... 14 J 100 Engine output...... 14 B. Definitions...... 5 J 200 Design loads for propeller and shafting...... 16 B 100 Symbols...... 5 J 300 Propeller...... 16 B 200 Terms ...... 5 J 400 Propulsion shaft line reinforcement...... 17 J 500 Miscellaneous machinery requirements...... 18 C. Documentation ...... 5 C 100 General...... 5 SEC. 4 VESSELS FOR ARCTIC AND ICE BREAKING SERVICE ...... 19 SEC. 2 BASIC ICE STRENGTHENING ...... 6 A. General...... 19 A. General...... 6 A 100 Classification ...... 19 A 100 Classification...... 6 A 200 Scope...... 19 A 300 Design principles and assumptions...... 19 B. Structural requirements for the class notation ICE-C...... 6 A 400 Definitions...... 19 B 100 General...... 6 A 500 Documentation...... 20 B 200 Plating ...... 6 B 300 Framing ...... 6 B. Materials and Corrosion Protection...... 21 B 400 Stringers ...... 6 B 100 Design temperatures...... 21 B 500 Weld connections...... 6 B 200 Selection of steel grades...... 21 B 600 Sternframe and rudder ...... 6 B 300 Coatings ...... 21 B 400 Corrosion additions...... 21 C. Machinery...... 6 C 100 Output of propulsion machinery ...... 6 C. Ship Design and Arrangement...... 21 C 200 Design of propeller and propeller shaft ...... 6 C 100 Hull form...... 21 C 300 Sea suctions and discharges...... 6 C 200 Appendages...... 22 C 300 Mooring equipment...... 22 D. Requirements for the Class Notation ICE-E ...... 7 D 100 General...... 7 D. Design Loads ...... 22 D 200 Plating ...... 7 D 100 Ice impact forces on the bow ...... 22 D 300 Framing ...... 7 D 200 Beaching forces...... 22 D 400 Stem ...... 7 D 300 Ice compression loads amidships...... 22 D 400 Local ice pressure ...... 23 SEC. 3 ICE STRENGTHENING FOR THE D 500 Accelerations...... 23 NORTHERN BALTIC ...... 8 E. Global Strength ...... 24 E 100 General...... 24 A. General...... 8 E 200 Longitudinal strength...... 24 A 100 Classification...... 8 E 300 Transverse strength amidships...... 25 A 200 Assumptions...... 8 E 400 Overall strength of substructure in the foreship...... 25 A 300 Definitions...... 8 A 400 Documentation...... 8 F. Local Strength ...... 25 F 100 General...... 25 B. Design Loads ...... 9 F 200 Plating ...... 25 B 100 Height of load area...... 9 F 300 Longitudinal stiffeners...... 25 B 200 Ice pressure ...... 9 F 400 Other stiffeners...... 26 F 500 Girders ...... 27 C. Shell Plating...... 9 C 100 Vertical extension of ice strengthening...... 9 G. Hull Appendages and Steering Gears ...... 27 C 200 Plate thickness in the ice belt ...... 10 G 100 General...... 27 G 200 Ice loads on rudders ...... 28 D. Frames...... 10 G 300 Rudder scantlings...... 28 D 100 Vertical extension of ice framing...... 10 G 400 Ice loads on propeller nozzles...... 28 D 200 Transverse frames ...... 10 G 500 Propeller nozzle scantlings ...... 29 D 300 Longitudinal frames ...... 11 G 600 Steering gear ...... 29 D 400 Structural details ...... 11 G 700 Podded propulsors and azimuth thrusters ...... 29 E. Ice Stringers ...... 12 H. Welding ...... 29 E 100 Stringers within the ice belt ...... 12 H 100 General...... 29 E 200 Stringers outside the ice belt ...... 12 H 200 External welding ...... 29 E 300 Deck strips ...... 12 H 300 Fillet welds and penetration welds subject to high stresses ...... 29 F. Web Frames...... 12 F 100 Design load ...... 12 I. Machinery Systems ...... 29 F 200 Section modulus and shear area...... 12 I 100 Pneumatic starting arrangement...... 29 I 200 Sea inlets and discharges ...... 29 G. Bilge Keels...... 13 I 300 Sea cooling water arrangements ...... 30 G 100 Arrangement...... 13 I 400 Ballast system ...... 30 H. Special Arrangement and Strengthening Forward...... 13 J. Propulsion Machinery and Propellers ...... 30 H 100 Stem, baltic ice strengthening ...... 13 J 100 General...... 30 H 200 Arrangements for towing ...... 13 J 200 Engine output...... 30

DET NORSKE VERITAS Rules for Ships, July 2006 Pt.5 Ch.1 Contents – Page 4

J 300 Determination of ice torque and loads ...... 30 E 300 Machinery systems...... 35 J 400 Propeller...... 31 J 500 Propulsion shaft line reinforcement ...... 31 SEC. 6 WINTERIZATION...... 36 K. Thrusters ...... 32 A. General...... 36 K 100 General ...... 32 A 100 Classification...... 36 K 200 Propulsion thrusters...... 32 A 200 Documentation...... 36 K 300 Other thrusters...... 33 B. Ship Design and Arrangement ...... 36 L. Stability and Watertight Integrity ...... 33 L 100 Application...... 33 B 100 Ship arrangement - Ice strengthening of hull, rudder, L 200 Documentation ...... 33 steering gear, propeller and propeller shaft...... 36 L 300 Requirements for intact stability...... 33 L 400 Requirements for damage stability ...... 33 C. Material for Low Temperature ...... 36 L 500 Requirements to watertight integrity...... 34 C 100 Hull material ...... 36 C 200 Materials for equipment...... 36 SEC. 5 SEALERS ...... 35 D. Anti-Icing, Anti-Freezing and De-icing ...... 37 A. General ...... 35 D 100 General...... 37 A 100 Classification...... 35 A 200 Hull form...... 35 E. Additional Requirements for Class Notation WINTERIZED ARCTIC (design temp.) ...... 37 B. Strength of Hull and Superstructures ...... 35 E 100 Ice strengthening and propulsion ...... 37 B 100 Ship's sides and stem...... 35 E 200 Enhanced oil pollution prevention ...... 37 B 200 Superstructures...... 35 SEC. 7 DAT(-X°C) ...... 38 C. Sternframe, Rudder and Steering Gear ...... 35 C 100 Design rudder force...... 35 A. General...... 38 C 200 Protection of rudder and propeller ...... 35 A 100 Classification...... 38 D. Anchoring and Mooring Equipment...... 35 A 200 Documentation...... 38 D 100 General ...... 35 A 300 Definitions...... 38 E. Machinery...... 35 B. Material Selection ...... 39 E 100 Output of propulsion machinery ...... 35 B 100 Structural categories...... 39 E 200 Thrust bearing, reduction gear, shafting and propeller ...35 B 200 Selection of steel grades...... 39

DET NORSKE VERITAS Rules for Ships, July 2006 Pt.5 Ch.1 Sec.1 – Page 5

SECTION 1 GENERAL REQUIREMENTS

A. Classification CB = block coefficient *) ∆ 3 f = displacement in t in fresh water (density 1.0 t/m ) at ice A 100 Application class draught 101 The rules in this chapter apply to vessels occasionally or Ps = maximum continuous output of propulsion machinery primarily intended for navigation in waters with ice conditions. in kW The requirements shall be regarded as supplementary to those s = stiffener spacing in m measured along the plating be- given for the assignment of main class. tween ordinary and/or intermediate stiffeners l = stiffener span in m measured along the top flange of A 200 Class notations the member. For definition of span point, see Pt.3 Ch.1 201 Vessels complying with relevant additional require- Sec.3 C100 ments of this chapter will be assigned one of the following S = girder span in m. For definition of span point, see Pt.3 class notations: Ch.1 Sec.3 C100. σ = minimum upper yield stress of material in N/mm2 F σ Table A1 Class notations For NV-NS-steel and HS-steel, F to be taken as given Notation Reference in Pt.3 Ch.1 Sec.2 B201 and Pt.3 Ch.2 Sec.2 B201. g = standard acceleration of gravity (≈ 9.81 m/s2). ICE-C 0 (See Sec.2) ICE-E *) For details see Pt.3 Ch.1. ICE-1A*F ICE-1A* B 200 Terms ICE-1A (See Sec.3) ICE-1B 201 Load waterline, LWL: ICE-1C The waterline corresponding to winter load line. For ships ICE - 05(or - 10 or - 15) trading in the Baltic during winter at summer load line, the ice POLAR - 10(or - 20 or - 30) (See Sec.4) strengthening shall be based on the summer load line, see also Icebreaker Sec.3 A300. WINTERIZED (design temp. °C) WINTERIZED ARCTIC (design temp. °C) (See Sec.6) 202 Ballast waterline, BWL: Sealer (See Sec.5) To be determined in such a way that the propeller, if possible, is completely submerged, see also Sec.3 A300.

B. Definitions C. Documentation B 100 Symbols 101 General C 100 General L = rule length in m *) 101 Details related to additional classes regarding design, ar- B = rule breadth in m *) rangement and strength are in general to be included in the D = rule depth in m *) plans specified for the main class. T = rule draught in m *) 102 Additional documentation not covered by the main class ∆ = rule displacement in t *) are specified in appropriate sections of this chapter.

DET NORSKE VERITAS Rules for Ships, July 2006 Pt.5 Ch.1 Sec.2 – Page 6

SECTION 2 BASIC ICE STRENGTHENING

A. General B 600 Sternframe and rudder 601 The section modulus of sternframe, rudder horn and sole A 100 Classification piece shall be 7.5% greater than required for the main class. 101 The requirements in this section apply to passenger and 602 Scantlings of rudders, rudder stocks and rudder shafts cargo vessels intended for service in waters with light ice con- shall be based on a rudder force 25% greater than a design val- ditions. ue calculated according to Pt.3 Ch.3 Sec.2 D101, with k1 = k2 The requirements in D for class notation ICE-E are intended = 1.0 irrespective of condition, rudder profile type and arrange- for light localised drift ice in mouths of rivers and coastal are- ment. as. 102 Vessels built in compliance with the following requirements may be given the class notation ICE-C. C. Machinery 103 Vessels built in compliance with the requirements in D may be given the class notation ICE-E. C 100 Output of propulsion machinery 101 The maximum continuous output is generally not to be less than:

B. Structural requirements for the class notation Ps = 0.73 L B (kW) ICE-C For ships with a bow specially designed for navigation in ice, a reduced output may be accepted. In any case, the output shall B 100 General not be less than:

101 The requirements to the forward ice belt region as de- Ps = 0.59 L B (kW) fined in Fig.1 of Sec.3 are to be in accordance with Sec.3 as follows: 102 If the ship is fitted with a controllable pitch propeller, the output may be reduced by 25%. — In Table B1, the value of ho and h shall be as given for ICE-1C. C 200 Design of propeller and propeller shaft — The ice pressure shall be determined in accordance with 201 Relevant criteria for propeller blades; blade bolts and Sec.3 B200, where the factor c1, as given in Table B3 need propeller shaft in Sec.3 shall be applied, assuming the ice not be taken larger than 0.55. torque in Nm: 2 B 200 Plating TICE= 35 200 R for open propellers 201 2 − -0.5 In the forward ice belt region as defined in 101, the shell TICE= 35 200 R (0.9 0.0622 R ) for ducted propellers plate thickness is to be as given in Sec.3 C. 202 Forward of amidships the ice belt shell plating is nowhere R = propeller radius (m). to be less than as would be required for the midship region. Skewed propellers will be especially considered with respect to the risk of blade bending at outer radii if fsk exceeds 1.15 B 300 Framing (see Sec.3 J304). 301 In the forward ice belt region as defined in 101, the 202 The propeller shaft diameter need not exceed 1.05 times frames shall be as given in Sec.3 D100 - D300. the rule diameter given for main class, irrespective of the di- In addition, the following shall apply: mension derived from Sec.3. — All frames shall be effectively attached to all supporting C 300 Sea suctions and discharges structures. Longitudinal or transverse frames crossing sup- 301 The sea cooling water inlet and discharge for main and porting structures, such as web frames or stringers, shall auxiliary engines shall be so arranged so that blockage of be connected to these structures by collar plates, lugs and strums and strainers by ice is prevented. In addition to require- top stiffeners as appropriate in way of cut-outs. ments in Pt.4 Ch.1 and Ch.6 the requirements in 302 and 303 — Frames which are not at a straight angle to the shell shall shall be complied with. be supported against tripping by brackets, intercostals, stringers or similar at a distance preferably not exceeding 302 One of the sea cooling water inlet sea chests shall be sit- 1.3 m. uated 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 accu- Transverse frames perpendicular to shell which are of un- mulate above the pump suctions. symmetrical profiles shall have tripping preventions if the span is exceeding 4.0 m. 303 A full capacity discharge branched off from the cooling — The web thickness of the frames shall be at least one half water overboard discharge line shall be connected to at least of the thickness of the shell plating. 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- B 400 Stringers icing arrangements. 401 Stringers situated inside and outside the ice belt shall be Guidance note: as given in Sec.3 E100 - E200. Heating coils may be installed in the upper part of the sea chest(s). Arrangement using ballast water for cooling purposes is B 500 Weld connections recommended but will not be accepted as a substitute for sea inlet chest arrangement as described above.

501 Weld connections to shell in fore peak shall be double continuous. ---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e---

DET NORSKE VERITAS Rules for Ships, July 2006 Pt.5 Ch.1 Sec.2 – Page 7

D. Requirements for the Class Notation ICE-E in Sec.3 C100 need not be taken larger than as given for notation ICE-1C. D 100 General 203 Forward of amidships the ice belt shell plating is no- 101 The requirements to the forward ice belt region as de- where to be less than as would be required for the midship re- fined in Fig.1 of Sec.3 are to be in accordance with Sec.3 as gion. follows: D 300 Framing — In Table B1, the value of ho and h shall be as given for ICE-1C. 301 In the forward ice belt region as defined in 101, the — The ice pressure shall be determined in accordance with frames shall be as given in Sec.3 D100 - D300. Sec.3 B200 where: 302 For the region from the stem to 0.075 L aft of the stem of the forward ice belt region, the framing shall extend verti- — For determination of k, the machinery output, Ps need not be taken > 750 kW. cally not less than 1.0 m above the LWL and 1.0 m below the BWL. — The factor c1, as given in Table B3 need not be taken larger than 0.3. 303 For the forward ice belt region tripping brackets shall be fitted as given in Sec.3 D402 item 1). D 200 Plating 201 In the forward ice belt region as defined in 101, the shell D 400 Stem plate thickness is to be as given in Sec.3 C. 401 The welded plate stems up to 600 mm above LWL is in 202 The vertical extension of the ice strengthening as given accordance with H202 to comply with Sec.3 C200.

DET NORSKE VERITAS Rules for Ships, July 2006 Pt.5 Ch.1 Sec.3 – Page 8

SECTION 3 ICE STRENGTHENING FOR THE NORTHERN BALTIC

A. General spans shall be measured along the side of the ship. 206 Assistance from icebreakers is normally assumed when A 100 Classification navigating in ice bound waters. 101 The requirements in this section apply to vessels for service in the northern Baltic in winter or areas with similar ice A 300 Definitions conditions. 301 Maximum draught amidships 102 Vessels built in compliance with the following requirements may be given one of the class notations ICE-1A*, ICE- The maximum ice class draught amidships shall be the draught 1A, ICE-1B ICE-1C on the Fresh Water Load Line in Summer. If the ship has a tim- or whichever is relevant. ber load line, the Fresh Water Timber Load Line in Summer Guidance note: shall be used. The DNV ice classes are accepted as equivalent to the Finnish- 302 Maximum and minimum draught fore and aft Swedish ice classes. (Extract of the Finnish Maritime Adminis- tration Bulletin No. 16/27.11.2002). The maximum and minimum ice class draughts fore and aft shall be determined and stated in the classification certificate. DNV Ice Class notation Equivalent Finnish-Swedish Ice Class The line defined by the maximum draughts fore, amidships ICE-1A* 1A Super and aft will henceforth be referred to as LWL. The line may be a broken line. The line defined by the minimum draughts fore ICE-1A 1A and aft will be referred to as BWL. ICE-1B 1B ICE-1C 1C The draught and trim, limited by the LWL, must not be exceed- ed when the ship is navigating in ice. The salinity of the sea Revision of the Finnish-Swedish Ice Class Rules of 1 October water along the intended route shall be taken into account 2002 concern propulsion power and structural strength and ap- when loading the ship. Filling of ballast tanks may be neces- plies to ships of which the keel is laid, or which is at a similar sary to load the ship to the BWL. Any ballast tanks situated ful- stage of construction on or after 1 September 2003, and was im- ly or partly above the BWL adjacent to the ship's shell shall be plemented into the DNV rules in January 2003. equipped with anti-freezing device(s) to prevent the water

---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e--- from freezing, see J603. In determining the BWL, regard shall be paid to the need for ensuring a reasonable degree of ice go- 103 Vessels built in compliance with the requirements rele- ing capability in ballast. The propeller shall be fully sub- vant for class ICE-1A* and with the additional requirements merged, if possible entirely below the ice. The minimum given below may acquire the class notation ICE-1A*F. forward draught shall be at least: ∆ Guidance note: (2 + 0.00025 f) ho (m) The additional ice class ICE-1A*F is recommended applied to but need not exceed 4 ho where vessels with relatively high engine power designed for regular traffic in the northern Baltic and other relevant areas, normally ∆ f = displacement of the ship (t) on the maximum ice class operating according to rather fixed timetables irrespective of ice draught according to 301 conditions and to a certain degree independent of ice breaker assistance. ho = ice thickness according to B101.

---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e--- 303 Ice belt regions The ice belt is divided into regions as follows (see also Fig.1): A 200 Assumptions Forward region: From the stem to a line parallel to and 0.04 L 201 The method for determining the hull scantlings is based aft of the forward borderline of the part of the hull where the on certain assumptions concerning the nature of the ice load on waterlines run parallel to the centre line. For ice classes ICE- the structure. These assumptions rest on full scale observations 1A*F, ICE-1A* and ICE-1A the overlap of the borderline made in the northern Baltic. need not exceed 6 m, for ice classes ICE-1B and ICE-1C this 202 The formulae given for plating, stiffeners and girders are overlap need not exceed 5 m. based on special investigations as to the distribution of ice Midship region: From the aft boundary of the Forward region loads from plating to stiffeners and girders as well as redistri- to a line parallel to and 0.04 L aft of the aft borderline of the bution of loads on stiffeners and girders. Special values have part of the hull where the waterlines run parallel to the centre been given for distribution factors and certain assumptions line. For ice classes ICE-1A*F, ICE-1A* and ICE-1A the have been made regarding boundary conditions. overlap of the borderline need not exceed 6 m, for ice classes 203 For the formulae and values given in this section for the ICE-1B and ICE-1C this overlap need not exceed 5 m. determination of the hull scantlings more sophisticated methods may be substituted subject to special approval. Aft region: From the aft boundary of the Midship region to the stern. 204 If scantlings derived from these regulations are less than those required for an unstrengthened ship, the latter shall be A 400 Documentation used. 401 LWL and BWL shall be indicated on the shell expansion 205 The frame spacing and spans defined in the following plan together with the lines separating the forward, amidships text are normally assumed to be measured in a vertical plane and aft regions of the ice belt. The machinery, displacement, ∆ parallel to the centreline of the ship. However, if the ship’s side f, and the output of propulsion machinery, Ps, shall be stated deviates more than 20° from this plane, the frame distances and on the shell expansion and/or the framing plan.

DET NORSKE VERITAS Rules for Ships, July 2006 Pt.5 Ch.1 Sec.3 – Page 9

Table B3 Values of c1 Region Ice class Forward Midship Aft 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

Fig. 1 For ice class ICE-1A*F an additional lower forward ice belt Ice belt regions (see C102) 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 B. Design Loads pressure at the same time. It is calculated by the formula: B 100 Height of load area 47– 5l c = ------a-, maximum 1.0, minimum 0.6 101 An ice strengthened ship is assumed to operate in open a 44 sea conditions corresponding to a level ice thickness not exceeding ho. The design height (h) of the area actually under ice la shall be taken as given in Table B4. 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 Table B4 Values of la are given in the following table. Structure Type of framing la transverse frame spacing Shell Table B1 Values of ho and h longitudinal 2 x frame spacing Ice class ho (m) h (m) transverse frame spacing Frames ICE-1A* 1.0 0.35 longitudinal span of frame ICE-1A 0.8 0.30 ICE-1B 0.6 0.25 Ice stringer span of stringer ICE-1C 0.4 0.22 Web frame 2 x web frame spacing B 200 Ice pressure 201 The design ice pressure (based on a nominal ice pressure of 5 600 kN/m2) is determined by the formula: C. Shell Plating 2 p = 5 600 cd c1 ca (kN/m ) C 100 Vertical extension of ice strengthening 101 The vertical extension of the ice belt (see Fig.1) shall not cd = a factor which takes account of the influence of the size and engine output of the ship. It is calculated by the be less than given in Table C1. formula: Table C1 Vertical extension of ice belt Ice class Above LWL (m) Below BWL (m) ak+ b cd = ------ICE 1A* 0.6 0.75 1000 ICE 1A 0.5 0.6 ICE 1B 0.4 0.5 ∆ P ICE 1C 0.4 0.5 k = ------f s 1000 102 In addition the following areas shall be strengthened: a and b are given in Table B2. 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 Table B2 Values of a and b frame spaces abaft the point where the bow profile departs Region from the keel line shall have at least the thickness required in Forward Midship and aft the ice belt in the midship region, calculated for the actual k ≤ 12 k > 12 k ≤ 12 k > 12 frame spacing. a306 8 2 Upper forward ice belt: For ice classes ICE-1A* and ICE-1A b 230 518 214 286 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 ∆ f = displacement (t) as defined in A302 to 2 m above it and from the stem to a position at least 0.2 L Ps = machinery output (kW) as defined in J101 abaft the forward perpendicular, shall have at least the thick- c1 = a factor which takes account of the probability that the ness required in the ice belt in the midship region, calculated design ice pressure occurs in a certain region of the for the actual frame spacing. hull for the ice class in question. Guidance note: A similar strengthening of the bow region is advisable also for a The value of c1 is given in Table B3: 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.

---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e--- For ice class ICE-1A*F the upper forward ice belt shall be taken 3 m above the normal ice belt, extending within the forward region.

DET NORSKE VERITAS Rules for Ships, July 2006 Pt.5 Ch.1 Sec.3 – Page 10

Lower forward ice belt: For ice class ICE-1A*F a lower forward ice belt below the normal ice belt is defined covering the t0.6s0.8= ()+ ------235L- (mm), minimum 10 mm forward region aft of the forefoot and down to the lower turn σ of bilge. F 103 Sidescuttles shall not be situated in the ice belt. If the weather deck in any part of the ship is situated below the upper limit of the ice belt (e.g. in way of the well of a raised quarter D. Frames deck), the bulwark shall be given at least the same strength as is required for the shell in the ice belt. The strength of the con- D 100 Vertical extension of ice framing struction of the freeing ports shall meet the same requirements. 101 The vertical extension of the ice strengthening of the C 200 Plate thickness in the ice belt framing shall be at least as given in Table D1: 201 For transverse framing the thickness of the shell plating Table D1 Vertical extension of ice strengthening of the shall be determined by the formula: framing x p Ice class Region Above LWL Below BWL t= 21.1s ------1 PL-t+ (mm) (m) (m) σ c F to double bottom or For longitudinal framing the thickness of the shell plating shall forward 1.2 below top of be determined by the formula: ICE- 1A*F floors midship 1.2 1.6 p t21.1s= ------PL + t (mm) aft 1.2 1.2 x σ c 2 F to double from stem to bottom or 0.3 L abaft it 1.2 below top of p PL = 0.75 p p = as given in B200. floors ICE-1A* abaft 0.3 L from 1.2 1.6 4.2 stem x1 =1.3 – ------, maximum 1.0 midship 1.2 1.6 ()⁄ 2 hs+ 1.8 aft 1.2 1.2 from stem to 0.4 1.0 1.6 ------≤ 0.3 L abaft it x2 = 0.6 + ()⁄ , when h/s 1 hs ICE-1A, abaft 0.3 L from stem 1.0 1.3 − ≤ 1B, 1C =1.4 0.4 (h/s); when 1 h/s < 1.8 midship 1.0 1.3 = 0.35 + 0.183 (h/s) for 1.8 ≤ h/s < 3 aft 1.0 1.0 = 0.9 for h/s > 3 Where an upper forward ice belt is required (see C102), the ice h = as given in B100 strengthened part of the framing shall be extended at least to σ 2 F = yield stress of the material (N/mm ) the top of this ice belt. 102 tc = increment for abrasion and corrosion (mm); normally Where the ice strengthening would go beyond a deck or 2 mm. If a special surface coating, by experience a tank top by not more than 250 mm, it can be terminated at shown capable to withstand the abrasion of ice, is ap- that deck or tank top. plied and maintained, lower values may be approved. D 200 Transverse frames 202 For ice class ICE-1A*F the following additional re- 201 The section modulus of a main or intermediate trans- quirements are given: verse frame shall be calculated by the formula:

— bottom plating in the forward region (below the lower for- pshl 3 3 Z = ------10 () cm ward ice belt defined in 102) shall have a thickness not less m σ than: t F p = ice pressure as given in B200 235L t= 0.7() s+ 0.8 ------(mm), minimum 12 mm h = height of load area as given in B100 σ F 7m m =------o ---- t 7 – 5h ⁄ l — side and bottom plating in the aft region below the ice belt shall have a thickness not less than: mo = values as given in Table D2.

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er may have the scantlings required for an unstrengthened Table D2 Values of m ship and the upper end be connected to the adjacent main o frames by a horizontal member of the same scantlings as Boundary condi- mo Example the main frame. Such an intermediate frame can also be tion extended to the deck above and if this is situated more than 1.8 metre above the ice belt the intermediate frame need not be attached to that deck, except in the Forward region. 203 Lower end of transverse framing 7 Frames in a bulk carrier with top wing tanks 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 ice stringer (see E). 2) Where an intermediate frame terminates below a deck, tank top or ice stringer which is situated at or below the lower limit of the ice belt (see C100), the lower end to be connected to the adjacent main frames by a horizontal member of the same scantlings as the frames. D 300 Longitudinal frames 6 Frames extending from the tank top to a single deck 301 The section modulus of a longitudinal frame shall be calculated by the formula: 2 x x phl ------3 4 - 3 ()3 Z = σ 10 cm m1 F The shear area of a longitudinal frame shall be:

5.7 Continuous frames between several These formulae assume that the longitudinal frame is attached decks or stringers to supporting structure as required in 401. 8.7 x phl ------3 - ()2 A = σ cm F

x3 = factor which takes account of the load distribution to Frames extending between adjacent frames: 5 two decks only − x3 = (1 0.2 h/s)

x4 = factor which takes account of the concentration of load to the point of support: The boundary conditions are those for the main and intermediate frames. Possible different conditions for main and interme- x4 = 0.6 diate frames are assumed to be taken care of by interaction p = ice pressure as given in B200 between the frames and may be calculated as mean values. h = height of load area as given in B100 Load is applied at mid span. m1 = boundary condition factor; m1 = 11 shall be used for If the ice belt covers less than half the span of a transverse continuous longitudinals. Where the boundary condi- frame, (b < 0.5 l) the following modified formula may be used tions deviate significantly from a continuous beam, a for the section modulus: smaller factor may be required.

2 ps h b ()l – b 3 3 Z = ------10 () cm D 400 Structural details σ 2 F l 401 Within the ice strengthened area all frames shall be effectively attached to all supporting structures. Longitudinal or transverse frames crossing supporting structures, such as web b = distance in m between upper or lower boundary of the frames or stringers, shall be connected to these structures on ice belt and the nearest deck or stringer within the ice both sides (by collar plates or lugs in way of cut-outs). belt. Brackets or top stiffeners shall be fitted, in order to provide Where less than 15% of the span, l, of the frame is situated proper transfer of forces to supporting elements, as necessary. within the ice-strengthening zone for frames as defined in Connection of non-continuous frames to supporting structures D101, ordinary frame scantlings may be used. shall be made by brackets or similar construction. When a bracket is installed, it has to have at least the same thickness as 202 Upper end of transverse framing the web plate of the frame, and the edge shall be appropriately stiffened against buckling. 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 402 For ice class ICE-1A*F and ICE-1A*, for ice class ICE- an ice stringer (see E). 1A in the forward and midship regions and for ice classes ICE- 1B and ICE-1C in the forward region, the following shall ap- 2) Where an intermediate frame terminates above a deck or ply in the ice strengthened area: an ice stringer which is situated at or above the upper limit of the ice belt (see C100) the part above the deck or string- 1) Frames which are not at a straight angle to the shell shall

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be supported against tripping by brackets, intercostals, designing weatherdeck hatch covers and their fittings. stringers or similar at a distance preferably not exceeding 1.3 m. Transverse frames perpendicular to shell which are of un- symmetrical profiles shall have tripping preventions if the F. Web Frames span is exceeding 4.0 m. F 100 Design load 2) Frames and girder webs shall be attached to the shell by double continuous welds. No scalloping is allowed (ex- 101 The load transferred to a web frame from an ice stringer cept when crossing shell plate butts). or from longitudinal framing shall be calculated by the formula: 3) The web thickness of the frames need not exceed one half of the thickness of the shell plating, calculated for a frame F = p h s (kN) spacing of 0.45 m, assuming the yield stress of the plate p = ice pressure as given in B200, when calculating factor not more than that used for the frame, minimum 9 mm. ca, however, la shall be taken as 2 s Where there is a deck, tank top or bulkhead in lieu of a h = height in m of load area as given in B100 frame the plate thickness of this shall be as above, to a depth corresponding to the height of adjacent frames. The product ph shall not be taken less than 300. s = web frame spacing in m E. Ice Stringers In case the supported stringer is outside the ice belt, the load F may be multiplied by: E 100 Stringers within the ice belt h ⎛⎞1 – -----s 101 The section modulus of a stringer situated within the ice ⎝⎠l belt (see C100) shall be calculated by the formula: s as given in E201. 2 0.9p h l 3 3 ------() Z = σ 10 cm m1 F The shear area shall not be less than: l 2 ------7.8 p h () A = σ cm F p = ice pressure as given in B200 h = height of load area as given in B100 The product p h shall not be taken as less than 300 l = span of stringer (m) m1 = boundary condition factor as given in D301. E 200 Stringers outside the ice belt 201 The section modulus of a stringer situated outside the ice belt but supporting ice strengthened frames shall be calculated Fig. 2 by the formula: Web frame

2 0.95 p h l h 3 3 Z = ------⎛⎞1 – -----s 10 () cm F 200 Section modulus and shear area m σ ⎝⎠l 1 F s 201 For a web frame simply supported at the upper end and The shear area shall not be less than: fixed at the lower end (see Fig.2), the section modulus requirement is given by: 8.2 p h l h 2 A = ------⎛⎞1 – -----s () cm σ ⎝⎠l M 1 3 3 F s Z = ------1 0 (cm ) σ A 2 F 1 – ⎛⎞γ------p = ice pressure as given in B200 ⎝⎠ h = height of load area as given in B100 Aa The product p h shall not be taken as less than 300. M = maximum calculated bending moment under the load F, as given in 101 l = span of stringer (m) γ = as given in Table F1 m1 = boundary condition factor as given in D301 A = required shear area from 202 l = the distance to the adjacent ice stringer(m) s Aa = actual cross sectional area of web plate. hs = the distance to the ice belt (m). 202 With boundary conditions as given in 201, the shear area E 300 Deck strips of a web frame is given by: 301 Narrow deck strips abreast of hatches and serving as ice 17.3α Q 2 stringers shall comply with the section modulus and shear area ------) A = σ (cm requirements in 100 and 200 respectively. In the case of very F long hatches the lower limit of the product p h may be reduced to 200. 302 Regard shall be paid to the deflection of the ship's sides Q = maximum calculated shear force under the load F, as due to ice pressure in way of very long hatch openings, when given in 101

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α = factor given in Table F1 Allowable stresses are as follows: Af = cross sectional area of free flange Aw = cross sectional area of web plate. τσ⁄ — shear stress: = F 3 203 For other web frame configurations and boundary con- σ σ ditions than given in 201, a direct stress calculation should be — bending stress: b = F performed. σ σ 2 τ2 σ The concentrated load on the web frame is given in 101. — equivalent stress: c ==b + 3 F The point of application is in each case to be chosen in relation to the arrangement of stringers and longitudinal frames so as to obtain the maximum shear and bending moments.

Table F1 Values of α and γ

A ------f- 0.00.20.40.60.81.01.21.41.61.82.0 Aw 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

G. Bilge Keels la = spacing of vertical supporting elements (m). G 100 Arrangement For class ICE-1A*F the front plate and upper part of the bulb 101 and the stem plate up to a point 3.6 m above LWL (lower part The connection of bilge keels to the hull shall be so de- of bow door included) shall have a minimum thickness of: signed that the risk of damage to the hull, in case a bilge keel is ripped off, is minimised. 102 To limit damage when a bilge keel is partly ripped off, it 235 L is recommended that bilge keels are cut up into several shorter tc= ------( m m ) σ independent lengths. f 103 For class ICE-1A*F bilge keels are normally to be avoided and should be replaced by roll-damping equipment. c = 2.3 for the stem plate Specially strengthened bilge keels may be considered. = 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 being the breadth of the bulb H. Special Arrangement and Strengthening For- at F.P. ward 103 The stem and the part of a blunt bow defined above shall be supported by floors or brackets spaced not more than 0.6 m H 100 Stem, baltic ice strengthening apart and having a thickness of at least half the plate thickness. 101 The stem may be made of rolled, cast or forged steel or The reinforcement of the stem shall be extend from the keel to of shaped steel plates. A sharp edged stem (see Fig.3) improves a point 0.75 m above LWL or, in case an upper forward ice belt the manoeuvrability of the ship in ice and is recommended par- is required (C102) to the upper limit of this. ticularly for smaller ships with length less than 150 m. H 200 Arrangements for towing 201 A mooring pipe with an opening not less than 250 by 300 mm, a length of at least 150 mm and an inner surface radius of at least 100 mm shall be fitted in the bow bulwark at the centre line. 202 A bitt or other means for securing a towline, dimensioned to stand the breaking force of the towline of the ship shall be fitted. 203 On ships with a displacement not exceeding 30 000 tons the part of the bow which extends to a height of at least 5 m above the LWL and at least 3 m aft of the stem, shall be Fig. 3 strengthened to take the stresses caused by fork towing. For Welded stem this purpose intermediate frames shall be fitted and the framing shall be supported by stringers or decks. 102 The plate thickness of a shaped plate stem and in the 204 It shall be noted that for ships of moderate size (displace- case of a blunt bow, any part of the shell which forms an angle ment not exceeding 30 000 tons) fork towing in many situa- of 30° or more to the centre line in a horizontal plane, shall be tions is the most efficient way of assisting in ice. Ships with a calculated according to the formulae in C200 assuming that: bulb protruding more than 2.5 m forward of the forward perpendicular are often difficult to tow in this way. The adminis- s = spacing of elements supporting the plate (m) trations reserve the right to deny assistance to such ships if the pPL = p (see B200). situation so warrants.

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I. Special Arrangement and Strengthening Aft 204 Relief valves for hydraulic pressure shall be effective. The components of the steering gear shall be dimensioned to I 100 Stern stand the yield torque of the rudder stock. Where possible rudder stoppers working on the blade or rudder head shall be fit- 101 The introduction of new propulsion arrangements with ted. azimuthing thrusters or “podded” propellers, which provide an improved manoeuvrability, will result in increased ice loading 205 Parts of rudder within the ice belt shall have local thick- of the aft region and stern area. This fact should be considered ness at least equivalent to the side shell in the afterbody. in the design of the aft/stern structure. 102 An extremely narrow clearance between the propeller blade tip and the stern frame shall be avoided as a small clear- J. Machinery ance would cause very high loads on the blade tip. 103 On twin and triple screw ships the ice strengthening of J 100 Engine output the shell and framing shall be extended to the double bottom 101 Definition of engine output for 1.5 metre forward and aft of the side propellers. The engine output PS is the maximum output the propulsion 104 Shafting and stern tubes of side propellers are normally machinery can continuously deliver to the propeller(s). If the to be enclosed within plated bossings. If detached struts are output of the machinery is restricted by technical means or by used, their design, strength and attachment to the hull shall be any regulations applicable to the ship, PS shall be taken as the duly considered. restricted output. For class ICE-1A*F the skin plating of propeller shaft bossings 102 Documentation on board shall not be less than: Minimum engine output corresponding to the ice class shall be given in the Classification Certificate. 235 L 103 Required engine output for ice classes t= 0.9() s+ 0.8 ------(mm). σ f Definitions 105 A wide transom stern extending below the LWL will se- The dimensions of the ship and some other parameters are de- riously impede the capability of the ship to run astern in ice, fined below: which is most essential. Therefore a transom stern shall not be extended below the LWL if this can be avoided. If unavoida- L = length of the ship between the perpendiculars (m) ble, the part of the transom below the LWL shall be kept as nar- LBOW = length of the bow (m), Fig.4 row as possible. The part of a transom stern situated within the L PAR = length of the parallel midship body (m), Fig.4 ice belt shall be strengthened as for the midship region. B = maximum breadth of the ship (m) T = actual ice class draughts of the ship (m) according to I 200 Rudder and steering arrangements A301 2 201 The scantlings of rudder, rudder post, rudder stock, pin- A wf = area of the waterline of the bow (m ), Fig.4 tles, steering gear etc. as well as the capacity of the steering α = the angle of the waterline at B/4 (°), Fig.4 ϕ ° gear shall be determined according to the rules. The maximum 1 = the rake of the stem at the centreline ( ), Fig.4 ϕ ° service speed of the ship to be used in these calculations is, 2 = the rake of the bow at B/4 ( ), Fig.4 however, not to be taken less than that stated below: DP = diameter of the propeller or outer diameter of nozzle for the nozzle propeller, maximum 1.2 times propel- Table I1 Maximum service speed ler diameter (m) Ice class Maximum service speed HM = thickness of the brash ice in mid channel (m) ICE-1A* 20 knots HF = thickness of the brash ice layer displaced by the bow ICE-1A 18 knots (m). ICE-1B 16 knots ICE-1C 14 knots Range of validity The range of validity of the formulae for powering require- If the actual maximum service speed of the ship is higher, that ments in 104 is presented in Table J1. When calculating the pa- speed shall be used. rameter DP/T, T shall be measured at LWL. When calculating the rudder force according to the formula given in Pt.3 Ch.3 Sec.2 D and with the speed V in ahead con- Table J1 Parameter validity range dition as given above, the factors k1 = k2 = 1.0 irrespective of Parameter Minimum Maximum condition, rudder profile type or arrangement. In the astern α [degrees] 15 55 condition half the speed values shall be used. ϕ 1 [degrees] 25 90 ϕ 202 For the ice classes ICE-1A* and ICE-1A the rudder 2 [degrees] 10 90 stock and the upper edge of the rudder shall be protected L [m] 65.0 250.0 against ice pressure by an ice knife or equivalent means. B [m] 11.0 40.0 Guidance note: T [m] 4.0 15.0 Upper forward part of rudder and forward part of rudder horn LBOW/L 0.15 0.40 should be protected against abrasion by a special coating or in- L /L 0.25 0.75 crease in thickness. PAR DP /T 0.45 0.75

---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e--- Awf /(L*B) 0.09 0.27 203 For ice classes ICE-1A* and ICE-1A due regard shall be If the ship’s parameter values are beyond the ranges defined in paid to the excessive loads caused by the rudder being forced Table J1, other methods for determining RCH shall be used as out of the midship position when backing into an ice ridge. defined in 105.

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Fig. 4 Definitions

104 The engine output requirement shall be calculated for Cµ =0.15 cosϕ2 + sinψ sinα the following two draughts: Cµ ≥ 0.45 (minimum value) Cψ =0.047ψ − 2.115 and 0 if ψ ≤ 45° — the maximum draught amidships referred to as LWL and 0.5 — the minimum draught referred to as BWL, as defined in HF =0.26 + (HMB) A302. HM = 1.0 for ICE-1A and ICE-1A* = 0.8 for ICE-1B In the calculations the ship's parameters which depend on the = 0.6 for ICE-1C draught shall be determined at the appropriate draught, but L and B shall be determined only at the LWL. The engine output C1 and C2 take into account a consolidated upper layer of the shall not be less than the greater of these two outputs. brash ice and can be taken as zero for ice class ICE-1A, ICE- 1B and ICE-1C. The engine output PS shall not be less than that determined by the formulae and in no case less than given in Table J3: For ice class ICE-1A*: Guidance note: BLPAR C = f ------+ ()10+ .021ϕ ()f Bf++L f BL 1 1 T 1 2 3 BOW 4 BOW “New ships” – see A102 Guidance note. 2---- + 1 For “existing ICE-1A and ICE-1A* ships” see Pt.7 Ch.2. B 2 ---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e--- T B C = ()10+ .063ϕ ()g + g B + g ⎛⎞11+ .2------2 1 1 2 3⎝⎠B L 3 R --- For a ship with a bulbous bow, ϕ shall be taken as 90°. ⎛⎞------CH- 2 1 ⎝⎠1000 P = K ------(kW) f =23 (N/m2) S e D 1 P f2 =45.8 (N/m) f3 =14.7 (N/m) 2 Table J2 Value of factor Ke f4 =29 (N/m) Propeller type or machinery g1 = 1 530 (N) Controllable pitch propeller or g2 = 170 (N/m) Numbers of Fixed pitch 1.5 electric or hydraulic propulsion g3 = 400 (N/m ) propellers propeller 2 2 machinery C3 = 845 (kg/(m s )) 2 2 1 propeller 2.03 2.26 C4 = 42 (kg/(m s )) C = 825 (kg/s2) 2 propellers 1.44 1.6 5 3 propellers 1.18 1.31 tanϕ ψ = arctan⎛⎞------2 ⎝⎠sinα Table J3 Minimum engine output PS ICE-1A, ICE-1B and ICE-1C 1 000 kW LT 3 The following shall apply: 20 ≥≥⎛⎞------5 ICE-1A* 2 800 kW ⎝⎠2 B RCH is the resistance in Newton of the ship in a channel with brash ice and a consolidated layer: 105 Other methods of determining Ke or RCH 2 For an individual ship, in lieu of the K or R values defined R = C ++C C C ()H + H ()BC+ H + e CH CH 1 2 3 µ F M ψ F in Table J2 and 104, the use of Ke or RCH values based on more exact calculations or values based on model tests may be ap- 2 LT 3Awf proved. Such approval will be given on the understanding that C L H + C ⎛⎞------(N) 4 PAR F 5⎝⎠2 L it can be revoked if experience of the ship’s performance in B practice motivates this.

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Guidance note: no = propeller speed at maximum continuous output, for For ships having the propulsion power determined by model tests which the machinery shall be approved, in revolutions or by means other than the rule formula, additional approval by per minute. FMA or SMA is necessary for ships requesting Finnish ice certificate. 302 Propellers and propeller parts (defined in Pt.4 Ch.5

Sec.1 A103) shall be of steel or bronze as specified in Pt.2 ---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e--- Ch.2. Nodular cast iron of Grade NV 1 and NV 2 may be used for relevant parts in CP-mechanism. Other type of nodular cast The design requirement for ice classes shall be a minimum speed iron with elongation ≥ 12% may be accepted upon special con- of 5 knots in the following brash ice channels (see Table J4): sideration for same purposes.. 303 Skewed propellers will be especially considered with re- Table J4 Values of HM spect to the risk of blade bending at outer sections if fsk (see Ice class HM 304) exceeds: ICE-1A* 1.0 m and a 0.1 m thick consolidated layer of ice ICE-1A 1.0 m — 1.10, in case propeller direction of rotation cannot be reversed ICE-1B 0.8 m — 1.05, in case propeller direction of rotation can be re- ICE-1C 0.6 m versed. J 200 Design loads for propeller and shafting 304 The blade thickness of the cylindrical sections at 0.25 R 201 The formulae for scantlings are based on the following (fixed pitch propellers only) and at 0.35 R shall not be less than: loads: 2RK ()U C + 0.2 + K tC= ------1 2 4 4 ( m m ) To = mean torque of propulsion engine at maximum con- 1 Zc (K U – U S ) tinuous rating in Nm r Mat 1 2 r The thickness at 0.6 R shall not be less than: (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.) 0.45⋅⋅ f c tt= ------sk 0.35- (mm) Tho = mean propeller thrust in N at maximum continuous 0.35 c speed 0.6 R = as given in 301. − 2 Tice = ice torque in Nm (referred to propeller r.p.m.) and = + ⎛ e0.6 e1.0 ⎞ found from Table J5. fsk 1 ⎜ ⎟ ⎝ R ⎠

Table J5 Values of Tice U1 and U2 = material constants to be taken as given in Pt.4 Ice class Open propeller Ducted propeller Ch.5 Sec.1 Table B1. 2 2 ICE-1A* 84 000 R 62 400 R 2Rn 2 ICE-1A 62 400 R2 52 000 R2 S = ⎛⎞------o- ()C θ + C r ⎝⎠2 3 ICE-1B 52 000 R2 47 600 R2 100 2. ICE-1C 47 600 R2 42 800 R R > 3 m 40 400 R2. R < 1.5 m 1) 0.75uT ⎛⎞o 1) For 1.5 m < R < 3 m, T may be found by linear interpolation. K = A dTh 0.85+ A ------ice 1 1 o 2 ⎝⎠R J 300 Propeller For fixed blade propellers 301 The particulars governing the requirements for scantlings are: uT K = A dTh 1.25+ A ------o R = propeller radius (m) 1 1 o 2 R Hr = pitch in m at radius in question θ = rake in degrees at blade tip (backward rake positive) For controllable pitch propellers Z = number of blades α t = blade thickness in mm at cylindrical section consid- K4 =ki Z Tice sin ered C1, C2, C3, C4 = as given in Table J6. t0.25 = t at 0.25 R 2 3 t0.35 = t at 0.35 R A = q0 + q1 d + q2 d + q3 d t =t at 0.6 R 0.6 q q q q = as given in Table J7. cr = blade width in m at cylindrical section considered 0, 1, 2, 3 c0.25 =cr at 0.25 R c0.35 =cr at 0.35 R 2πR d = ------for fixed blade propellers c0.6 =cr at 0.6 R H e = distance between skew line and generatrix in m at cy- r lindrical section considered, positive when skew line is 2πR forward of generatrix. d =------for controllable pitch propellers e0.6 =e at 0.6 R 0.7Hr e1.0 =e at 1.0 R u = gear ratio: ki = 96 at 0.25 R = 92 at 0.35 R K = 1.0 for stainless steel propellers engine r.p.m. Mat u = ------= 0.8 for other materials propeller r.p.m. 4 sin α =------at 0.25 R If the shafting system is directly coupled to engine, u = 1. 2 d + 16

DET NORSKE VERITAS Rules for Ships, July 2006 Pt.5 Ch.1 Sec.3 – Page 17

The propeller blade foot shall have a strength (including stress 2.86 concentration) not less than that of the bolts. =------at 0.35 R 2 308 Fitting of the propeller to the shaft is given in Pt.4 Ch.4 d + 8.18 Sec.1 as follows: K1 as given above is only valid for propulsion by diesel engines (by about zero speed, it is assumed 85% thrust and 75% — Flanged connection in B300 torque for fixed pitch propellers and 125% thrust and 100% — Keyless cone connection in B400 torque for controllable pitch propellers). — Keyed cone connection in B500 For turbine, diesel-electric or similar propulsion machinery K1 (Considering 0°C seawater temperature) will be considered in each particular case. If the propeller is bolted to the propeller shaft, the bolt connec- Guidance note: tion shall have at least the same bending strength as the propel- ≥ K1 1.1 may be used if nothing else is documented ler shaft.

---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e--- The strength of the propeller shaft flange (including stress concentration) shall be at least the same as the strength of the bolts. The thickness of other sections is governed by a smooth curve connecting the above section thicknesses. J 400 Propulsion shaft line reinforcement 401 Determination of factors for ice reinforcement of shaft Table J6 Values of C1, C2, C3, C4 line. r 0.25 R 0.35 R 0.6 R u = as defined in 301 C1 0.278 0.258 0.150 I = equivalent mass moment of inertia in kgm2 based on C2 0.026 0.025 0.020 torque of all parts on engine side of component under C3 0.055 0.049 0.034 consideration. C 1.38 1.48 1.69 4 Masses rotating with engine speed to be transformed according to: Table J7 Values of q0, q1, q2, q3 2 Iequiv = I actual u Rq0 q1 q2 q3 In propulsion systems with hydraulic coupling, torque convert- 0.25 R A1 8.30 0.370 -0.340 0.030 A2 63.80 -4.500 -0.640 0.0845 er or electromagnetic slip coupling, the masses in front of the coupling shall not be taken into consideration. 0.35 R A1 9.55 -0.015 -0.339 0.0322 A2 57.30 -7.470 -0.069 0.0472 It = equivalent mass moment of inertia of propulsion sys- 0.6 R A1 14.60 -1.720 -0.103 0.0203 2 A2 52.90 -10.300 0.667 0.0 tem in kgm . (Masses in front of hydraulic or electromagnetic slip coupling shall not be taken into 305 When the outer sections of the propeller blade is not sub- consideration.) ject to special consideration according to J303, the blade tip thickness at the radius 0.95 R shall not be less than given by 402 Application factor for diesel and or turbine machinery in the following formulae: general: T I 490 = + ice t204R= ()+ ------( m m ) K Aice 1 σ uT0IT b For ICE-1A*: 403 Application factor for electric motor machinery or diesel machinery with hydrodynamic torque converter: 490 t154R= ()+ ------( m m ) σ 1) Diesel engine with torque converter or hydrodynamic cou- b pling: For ICE-1A, ICE-1B or ICE-1C = TTC max + TiceI σ 2 K Aice b = ultimate tensile strength in N/mm of propeller blade T0 uT0I t material. The thickness of the blade edge and the propeller tip shall not TTC max = maximum possible transmittable torque through be less than 50% of minimum t as given above, measured at converter and or coupling. 1.25 t from the edge or tip, respectively. For propellers where 2) Electric motor drive: the direction of rotation is not reversible, this requirement only applies to the leading edge and propeller tip. T T I K = max + ice 306 If found necessary by the torsional vibration calcula- Aice T uT I tions, minor deviations from the dimensions given in 304 and 0 0 T 305 may be approved upon special consideration. Tmax = motor peak torque (steady state condition). 307 The section modulus of the blade bolt connection re- Alternatively to the above criteria, the ice impact load may be ferred to an axis tangentially to the bolt pitch diameter, shall documented by simulation of the transient dynamic response not be less than: in the time domain. For branched systems, such simulation is σ in general recommended. 2 -----b- ()3 Wb = 0.1 c0.35 t0.35 σ cm 404 The diameter of the propeller shaft at the aft bearing y shall not be less than: σ 2 σ 2 b = tensile strength of propeller blade material (N/mm ) b = tensile strength of propeller blade material (N/mm ) σ 2 σ 2 y = yield stress of bolt material (N/mm ) y = yield strength of propeller shaft material (N/mm )

DET NORSKE VERITAS Rules for Ships, July 2006 Pt.5 Ch.1 Sec.3 – Page 18

1 --- 502 Sea inlet and cooling water systems. σ 2 3 ⎛⎞bC0.35t0.35 The cooling water system shall be designed to ensure supply of dp = 11.5⎜⎟------(mm) ⎝⎠σ cooling water when navigating in ice. The sea cooling water y inlet and discharge for main and auxiliary engines shall be so c0.35 = as defined in 301 arranged that blockage of strums and strainers is prevented. t = as defined in 301. 0.35 For this purpose at least one cooling water inlet chest shall be Between the aft and second aft bearing, the shaft may be even- arranged as follows: ly tapered to 1.22 times the diameter of the intermediate shaft, as required for the main class. 1) The sea inlet shall be situated near the centre line of the ship and well aft if possible. The inlet grids shall be spe- Forward of the after peak bulkhead, the shaft may be evenly ta- cially strengthened. pered down to 1.05 times the rule diameter of intermediate shaft, but not less than the actual diameter of the intermediate shaft. 2) As a guidance for design the volume of the chest shall be about one cubic metre for every 750 kW engine output of 405 The diameter of intermediate shafts shall be determined the ship including the output of the auxiliary engines nec- based on methods given in Pt.4 Ch.4 Sec.1 B201. essary for the ship's service. a) When using the classification note 41.4 the necessary rein- 3) To allow for ice accumulation above the pump suction the forcement is determined by using KAice in the given criteria. height of the sea chest shall not be less than: b) With K ≤ 1.4 the method in Pt.4 Ch.4 Sec.1 B206 may Aice ≥ 3 be used, i.e. no ice reinforcement beyond 1A1 rules. hmin 1.5 Vs When using the method in Pt.4 Ch.4 Sec.1 B208, the minimum diameter in item 3 of that paragraph is to be multiplied with: Vs = volume of sea chest according to item 2. 1 The suction pipe inlet shall be located not higher than h /3 from top of sea chest. ⎛ K Aice ⎞ 3 min ⎜ ⎟ ⎝ 1.4 ⎠ 4) A pipe for discharge cooling water, allowing full capacity discharge, shall be connected to the chest. Where the sea chest but not less than 1.0 volume and height specified in 2 and 3 are not complied with, τ the discharge shall be connected to both sea chests. At least In item 4 of same paragraph, the vibratory torsional stress v is replaced by: one of the fire pumps shall be connected to this sea chest or to another sea chest with de-icing arrangements. τ = ⋅()− ⋅ v 0.5 K Aice 1 T0 5) The area of the strum holes shall be not less than four (4) τ and is not to exceed C. times the inlet pipe sectional area. 406 Regarding shaft connections, use KAice in Pt.4 Ch.4 Sec.1 as follows: If there are difficulties in meeting the requirements of 2) and 3) above, two smaller chests may be arranged for alternating in- — Flange connections, see B300 take and discharge of cooling water. The arrangement and situation otherwise shall be as above. — Shrink fit connections, see B400 — Keyed connections, see B500 Heating coils may be installed in the upper part of the chest or chests. 407 The thrust bearing shall be dimensioned for a thrust according to: Arrangements using ballast water for cooling purposes may be useful as a reserve in ballast condition but can not be accepted T as a substitute for sea inlet chests as described above. Th= 1.3Th + ------ice- (N) o R 503 Ballast system 408 For reduction gears, use K in Pt.4 Ch.4 Sec.2. An arrangement to prevent freezing of the ballast water shall Aice be provided for in ballast tanks located fully or partly above the 409 For clutches, use KAice in Pt.4 Ch.4 Sec.3 B100 BWL, adjacent to the ship's shell, and needed to be filled for operation in ice conditions according to A302. For this purpose 410 For torsional elastic coupling, use KAice in Pt.4 Ch.4 Sec.5 B200. the following ambient temperatures shall be taken as design conditions: 411 For crank shafts in direct coupled diesel engines, see Pt.4 Ch.3 Sec.1 B506. — Sea water temperature: 0°C — Air temperature: –10°C J 500 Miscellaneous machinery requirements 501 Starting arrangements Necessary calculations shall be submitted. The capacity of the air receivers shall be according to the re- When a tank is situated partly above the BWL, an air-bubbling quirements in Pt.4 Ch.6 Sec.5 I. arrangement or a vertical heating coil, capable of maintaining an open hole in the ice layer, will normally be accepted. If the air receivers serve any other purposes than starting the propulsion engine, they shall have additional capacity suffi- The required heat-balance calculations may then be omitted. cient for these purposes. Guidance note: The capacity of the air compressors shall be sufficient for charg- It is assumed that, before pumping of ballast water is coming the air receivers from atmospheric to full pressure in one (1) menced, proper functioning of level gauging arrangements is hour, except for a ship with the ice class ICE-1A* if its propul- verified and air pipes are checked for possible blockage by ice. sion engine has to be reversed for going astern, in which case the compressors shall be able to charge the receivers in half an hour. ---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e---

DET NORSKE VERITAS Rules for Ships, July 2006 Pt.5 Ch.1 Sec.4 – Page 19

SECTION 4 VESSELS FOR ARCTIC AND ICE BREAKING SERVICE

A. General related to the selected nominal ice thickness. 302 Vessels with the class notation Icebreaker, and other A 100 Classification POLAR class vessels are expected to encounter pressure ridg- 101 The requirements in this section apply to icebreakers es and other ice features of significantly greater thickness than and to passenger and cargo vessels intended to operate unas- the average thicknesses specified in Table A1. Vessels with the sisted in ice-infested waters of sub-Arctic, Arctic and/or Ant- class notation POLAR only are assumed not to make repeated arctic regions. ramming attempts if the ice fails to break during the first (occasional) ram unless the vessel's speed is kept well below the 102 Vessels intended for ice breaking as their main purpose design ramming speed. Vessels with class notation Icebreak- and built in compliance with the following requirements may er may make several consecutive attempts to break the ice at be given one of the class notations Icebreaker ICE-05 (or - maximum ramming speed. The design speed in ice infested 10 or -15) or Icebreaker POLAR-10 (or -20 or -30), which- waters when ramming may occur, VRAM, shall be specified by ever is relevant. the builder. In general this speed shall not be taken less than: Vessels built for another main purpose, while also intended for V = V + V (m/s) ice breaking, may be given the additional class notation ICE- RAM B H 05 (or -10 or -15) or the notation POLAR-10 (or -20 or -30). VB = specified continuous speed, when breaking maximum 103 Arctic class vessels intended for special services where average ice thickness intermediate ice condition values are relevant may, upon spe- VH = speed addition in thinner ice cial consideration, be given intermediate notations (e.g. PO- =hice (see Table A1). LAR-25). In no case the design ramming speed shall be taken less than: 104 For POLAR class vessels the design ambient air temperature on which the classification has been based will be given VRAM (minimum) the special feature notation DAT(—x°C). For details, see Sec.7. = 2.0 m/s (3.9 knots) for the notation POLAR-10 105 For vessels with the class notation Icebreaker, and for other POLAR class vessels the maximum operational speed = 3.0 m/s (5.8 knots) for the notation POLAR-20 on which the ramming design requirements have been based = 4.0 m/s (7.8 knots) for the notation POLAR-30. will be stated in the “Appendix to the classification certificate”. The operational speed is in no case to be taken as smaller For vessels with the class notation Icebreaker the minimum than stated in 300 for the various class notations. speed is 2 m/s (3.9 knots) but not less than 1.5 times the speed specified above when POLAR class notation is also specified. A 200 Scope A 400 Definitions 201 The following matters are covered by the classification: 401 General symbols and terms are also given in Sec.1 B100. — materials in structures exposed to low ambient air temper- 402 Symbols atures — subdivision, intact and damage stability VRAM = design speed in m/s when ramming may occur, see — hull girder longitudinal and transverse strength also 302 σ 2 — local hull structures exposed to ice loads ice = nominal strength of ice in N/mm , see Table A1 — rudders and steering gears hice = average ice thickness in m, see Table A1 — propellers and propulsion machinery EKE = vessel's kinetic energy before ramming ∆ 2 — sea suctions for cooling water =1/2 (VRAM) (kNm) — air starting systems α, γ = bow shape angles, see Fig.1 CWL = vessel's water line area coefficient on LWL MDHT Mean daily high (or maximum) temperature s = stiffener spacing in m, measured along the plating. MDAT Mean daily average temperature Stiffener web thickness may be deducted MDLT Mean daily low (or minimum) temperature l = Stiffener span in m, measured along the top flange MAMDHT Monthly average of MDHT of the member. MAMDAT Monthly average of MDAT For determining the section modulus and shear area MAMDLT Monthly average of MDLT of the stiffener, the depth of stiffener on crossing MEHT Monthly extreme high temperature (ever recorded) panel and 2/3 of the arm length of end bracket(s) (except at simply supported ends) may be deducted MELT Monthly extreme low temperature (ever recorded). when deciding the span. Mean: Statistical mean over observation period (at least 20 S = girder span in m. The web height of in-plane girders years). may be deducted Average: Average during one day and night. t = rule thickness of plating in mm tk = corrosion addition in mm A 300 Design principles and assumptions tw = rule web thickness in mm Z = rule section modulus in cm3 301 Each class notation is related to a particular ice condition 2 that the vessel is expected to encounter. Relevant design ice AW = rule web area in cm , defined as the web thickness conditions are as given in Table A1. In case intermediate ice times the web height including thickness of flanges conditions are relevant (see 103), nominal ice strength shall be A = rule cross-sectional area in cm2

DET NORSKE VERITAS Rules for Ships, July 2006 Pt.5 Ch.1 Sec.4 – Page 20

Table A1 Ice conditions Class notation Type of ice encountered Nominal ice strength Nominal ice thickness Limiting impact conditions σ 2 ice(N/mm ) hice (m) ICE-05 4.2 0.5 ICE-10 Winter ice with pressure ridges 5.6 1.0 No ramming anticipated ICE-15 7.0 1.5 POLAR-10 7.0 1.0 POLAR-20 Winter ice with pressure ridges and multi- year ice-floes and glacial ice inclusions 8.5 2.0 Occasional ramming POLAR-30 10.0 3.0 Icebreaker As above As above As above Repeated ramming

Vertically from a line defined by the distance zla below BWL, LWL F.P. to a line defined by the distance z above LWL. 1 ua m Stern area Longitudinally from the stern to a line parallel to and 0.04 L forward of the border line of flat side of hull aft, or to a line CENTRE LINE 0.2 L aft of amidships, whichever is the aftermost. α Vertically from a line defined by the distance zla below BWL, to a line defined by a distance zua above LWL. K γ LWL C TO E Midship area T IN BU L M Longitudinally from the stern area to the bow area. TE BASE LINE S Vertically from a line defined by the distance zlm below BWL, to a line defined by a distance z above LWL. Fig. 1 ua Bow shape angles Bottom area Longitudinally aft of 0.3 L from F.P. and transversely over the flat bottom including deadrise. For ships with bow ice knife, 403 The hull structure (shell plating with stiffening) to be re- the bottom area may be extended forward to the ice knife. inforced against local ice loads is divided into 7 different areas. The areas are defined as follows (see also Fig.2): Lower transition area Bow area Transition area between the bottom area and the adjacent stern, and midship areas respectively. Longitudinally from stem to a line parallel to and 0.04 L aft of the border line of flat side of hull forward. If the hull breadth is Lower bow area increased over a limited length forward of the flat side the bow The area below the bow area. area need normally not extend aftwards beyond the widest sec- LWL and BWL are defined in Sec.1 B200. tion of each waterline. Values of zla, zlm, zua, and zuf are given for various class no- The bow area need not extend aftwards beyond 0.3 L from the tations in Table A2. forward perpendicular.

Vertically from a line defined by the distance zlm below BWL Table A2 Vertical extent of ice reinforced areas (aft) and the intersection between the keel line and the stem Class notation Parameters for vertical extent (m) line (forward) to a line defined by the distances zua (aft) and zuf z z 1) z z (forward) above LWL. For ships with an ice knife fitted, the la lm ua uf line of the lower vertical extension may be drawn to a point ICE-05 1.7 1.1 0.8 1.5 ICE-10 2.2 1.6 1.0 2.0 0.04 L aft of the upper end of the knife and further down to the ICE-15 4.6 3.7 1.9 2.5 base line (see also Fig.2). POLAR-10 2.9 2.3 1.4 2.2 POLAR-20 6.0 4.6 2.8 3.7 POLAR-30 11.9 9.2 4.2 5.2 1) zlm (maximum) = the vertical distance from the BWL to the

f point on the frame contour amidships where u a Z

u the tangent is at 45 degrees. Z LWL BWL A 500 Documentation 501 LWL and BWL as well as the border line of flat side

lm shall be indicated on the shell expansion plan together with the Z ice reinforced areas as given in Fig.3. 0.04 L 0.3 L 502 Maximum design ramming speed (VRAM) in ice infested waters as well as design speed for continuous ice breaking operations (VB) shall be stated on the midship section plan for Fig. 2 ships with class notations POLAR or Icebreaker. Extension of bow area 503 For documentation in connection with stability and watertight integrity, see L300. Stem area 504 Applicable design specifications for the operation of the The part of the bow area between the stem line and a line 0.06 vessel in ice infested waters shall be stated in the ship's loading L aft of the stem line or 0.125 B outboard from the centre line, manual, see Pt.3 Ch.1 Sec.5 F and Pt.3 Ch.2 Sec.4 E. whichever is first reached. Possible design specifications are:

DET NORSKE VERITAS Rules for Ships, July 2006 Pt.5 Ch.1 Sec.4 – Page 21

— allowable draughts, maximum and minimum 505 Where ice exposed plating is fitted with a special wear — loading conditions with respect to strength and stability addition, the plate thickness including wear addition shall be — ambient temperature given on the shell expansion plan in addition to the net thick- — design speed ness required by the rules. — ramming speed — instruction for filling of ballast tanks. — astern operation in ice.

STERN AREAMIDSHIP AREA BOW AREA

LOWER TRANSITION AREA BOTTOM AREA LOWER BOW

0.06L BORDER LINE OF FLAT SIDE (max) 0.04L 0.04L

Zuf LWL Z Zlm Zua ua BWL Zla Zla

0.2L 0.3L A.P. F.P.

LOWER TURN OF THE BILGE 0.125 B (max)

BORDER LINE OF FLAT SIDE (AT LWL)

Fig. 3 Ice reinforced areas

B. Materials and Corrosion Protection B200 Table B1. Cranes shall be in compliance with "Rules for Certification of B 100 Design temperatures Lifting Appliances". 101 Steel grades to be used in hull structural members shall be determined based on the design temperature for the struc- B 300 Coatings ture in question with requirements as given in Sec.7. 301 Wear resistant coating is assumed used for the external 102 For POLAR class notations steel grades in exposed surfaces of plating in ice reinforced areas. structures (external structure as defined in Sec.7) shall be based on air temperatures lower than those generally anticipat- B 400 Corrosion additions ed for world wide operation. Unless a service restriction nota- 401 Hull structures are in general to be given a corrosion ad- tion is also given, limiting the navigation to specified areas dition tk as required by the main class, see Pt.3 Ch.1 Sec.2 and and/or time of year, the design temperature shall not be taken or Pt.3 Ch.2 Sec.2. higher than -30°C (corresponding extreme low temperature -50ºC). For operation in lower design temperatures, this must be clear- ly specified. C. Ship Design and Arrangement 103 For ICE class notations no special consideration for low C 100 Hull form ambient air temperatures are given unless specified by the builder. 101 The bow shall be shaped so that it can break level ice effectively and at continuous speed, up to a thickness as indicat- B 200 Selection of steel grades ed in Table A1 for the various class notations. 201 Plating materials for various structural categories of ex- 102 Vessels with class notation Icebreaker, and other PO- posed members above the ballast waterline of vessels with LAR class vessels shall have a bow shape so that the bow will class notation POLAR shall not be of lower grades than ob- ride up on the ice when encountering pressure ridges or similar tained from Sec.7 using design temperatures as defined in 100. ice features that will not break on the first ramming. Plating materials of non-exposed members and of vessels with 103 Masts, rigging, superstructures, deckhouses and other class notation ICE shall not be of lower grade than obtained ac- items on deck shall be designed and arranged so that excessive cording to Pt.3 Ch.1 Sec.2 B200 Table B1and Pt.3 Ch.2 Sec.2 accumulation of ice is avoided. The rigging shall be kept at a

DET NORSKE VERITAS Rules for Ships, July 2006 Pt.5 Ch.1 Sec.4 – Page 22 minimum, and the surfaces of erections on deck shall be as L as defined in Sec.1 B100. even as possible. 4 104 Weathertight doors and hatches shall be suitably de- IV = moment of inertia in m about the horizontal neutral axis signed for use in low temperature environment with respect to: of the midship section. — strength of cleats and the choice of steel with adequate 102 The total design force normal to the shell plating in the ductility bow area due to an oblique impact with an ice feature is given — flexibility of packing material by: — ease of maintenance, e.g. interior accessible grease fittings P F ------ZR SIDE — ease of operations, e.g. low weight and preference to cen- POI = γ (kN) tral handwheel operated cleats. cos σ 0.05 105 Air pipe closures shall be designed so that icing or freez- 1.9 ice F = ------⎛⎞------in general ing will not make them inoperable. SIDE 0.4⎝⎠ ()tanα EKE 106 Freeing ports shall be designed so that blocking by ice is avoided as far as possible and so that they are easily accessible 0.1 B for removal of ice should blocking occur. tanα = 1 .2------for spoon shaped bows cosγ C 200 Appendages 201 In vessels with class notation Icebreaker and in other PZR = vertical ramming load as given in 101 POLAR class vessels an ice knife may be required forward to avoid excessive beaching and submersion of the deck aft. This requirement will be based on consideration of design speed L and B as defined in Sec.1 B100. σ α γ and freeboard, and may result in additional requirements re- EKE, ice, and as defined in A400. garding accelerations and strength. D 200 Beaching forces 202 Ice horns shall be fitted directly abaft each rudder in such a manner that: 201 The vertical design force resulting from beaching on a large ice feature (not applicable to vessels with class notation — the upper edge of the rudder is protected within two de- ICE only) is in general given by: grees to each side of midposition when going astern, and — ice is prevented from wedging between the top of the rudder and the vessel's hull. PZB = GB kbEKELB (kN) C 300 Mooring equipment 301 The housing arrangement for anchors shall be designed C ()C – 0.5 G = ------WL WL so that possible icing will not prevent the anchor from falling B ()C + 1 when released. WL − kb =2 go (1 rfw) rfw = reduction factor due to energy lost in friction and waves D. Design Loads =0.3. σ γ α D 100 Ice impact forces on the bow EKE, ice, CWL, and as defined in A400. 101 The vertical design force component due to head on L, B and go as defined in Sec.1 B100. ramming (not applicable to vessels with class notation ICE on- 202 For vessels with vertical ram bow the vertical design ly) is given by: force in beaching need not be taken larger than: P ZR = PR FEL (kN) 0.6 γ C E 0.4 10.6C BLXtan P = 28⎛⎞------R IMP ()σ tanα in general P = ------WL (kN) R ⎝⎠γ ice ZB 2 tan 1150.55XL+ []– ()⁄ 0.1 B For spoon bows: tanα = 1.2------X = horizontal distance from FPICE to centre of ver- cosγ tical ram bow in m FPICE = intersection point of stem line and deepest ice- 2 tan γ breaking waterline E = E ------C WL = waterline area coefficient. IMP KE 2γ tan + 2.5 L and B as defined in Sec.1 B100.

E D 300 Ice compression loads amidships F = ------IMP EL 2 301 All vessels shall withstand line loads acting simultane- EIMP + CLPR ously in the horizontal plane at the water level on both sides of the hull. These loads are assumed to arise when a vessel is 3 L trapped between moving ice floes. C = ------L × 10 302 The design line loads shall be taken as: 310IV 165 1.5 CR = 1 for the class notation POLAR only q = ------()h (kN/m) = 2 for the class notation Icebreaker sinβ ice σ α γ EKE, ice, and as defined in A400. hice = average ice thickness as defined in A400

DET NORSKE VERITAS Rules for Ships, July 2006 Pt.5 Ch.1 Sec.4 – Page 23

0.1 B For spoon bows: tanα = 1.2------β = angle of outboard flare at the waterlevel. Need not to cosγ be taken as less than 10 degrees.

D 400 Local ice pressure P = the largest of PZR and PZB as given in D100 and D200. 401 All vessels shall withstand local ice pressure as defined w = critical width of contact area in m for the different ice class notations and as applied to the differ- = l for longitudinals ent ice reinforced areas. The design pressure shall be applied = s for non-longitudinal frames over a corresponding contact area reflecting the type of load in = 1.4 l for connection area for longitudinals question. = l for vertical girders supporting longitudinal main frames 402 The basic ice pressure is in general to be taken as: = S for stringers supporting vertical main frames. σ 2 po = 1 000 FA ice (kN/m ) l, S, α and γ as defined in A400. FA = correction factor for ice reinforced area in question = 1.0 for bow and stem area in general. The relations are illustrated in Fig.4. = 0.6 for midship area in general = 0.5 for midship area if ship breadth in bow area larger

than ship breadth in midship area ICE h h = 0.20 for bottom area of vessels with notation ICE- SHEET ice BREAKER or POLAR = 0.10 for vessels with notation ICE only W = 0.6 for stern area in general = 0.8 for stern area in ships with class notation Ice- VERTICAL GIRDERS breaker = 1.0 for the stern area in ships with class notation Ice- breaker or POLAR, and 0.8 for ships with ICE notations, fitted with pod or thruster propulsion units, and designed for continuous operation astern. The stern area structure shall in general be dimensioned as out- lined for bow structure. See also G700. ll

For the transition areas 2/3 of the FA-value for the adjacent area above may be used in general. LONGITUDINAL STRINGERS σ ice as defined in A400. 403 The design pressure is in general to be taken as: 2 p = FB po (kN/m ) S FB = correction factor for size of design contact area AC Fig. 4 0.58 2 =------for A ≤ 1.0 m Design contact areas ()0.5 C AC

0.58 2 D 500 Accelerations =------for A > 1.0 m ()0.15 C 501 Substructures, equipment and supporting structures AC shall withstand accelerations arising as a result of impacts with 2 ice features. AC =ho w (m ) ho =h in general 502 The combined vertical acceleration at any point along = s, maximum for longitudinals the hull girder (not applicable to vessels with class notation =l, maximum for non-longitudinal frames ICE only) may be taken as: =1.4 l, maximum for connection area of non-longitudi- 2.5P 2 nal frames a = ------ZR F () m⁄ s = S, maximum for girders supporting longitudinals v ∆ X =l, maximum for stringers supporting non-longitudinal FX = 1.3 at F.P. frames = 0.1 at midships h = effective height of contact area in m = 0.4 at A.P. =0.4 hice (m) in general = 0.64 hice (m) in the stern area; for vessels fitted with Linear interpolation shall be applied between specified posi- pod or thruster propulsion units, and designed for con- tions. tinuous operation astern P as derived in 100. =0.8 hice (m) in stem area in general ZR 0.5 2 2 ∆ as defined in Sec.1 B100. P 0.6⎛⎞tan γα+ tan =⎛⎞------⎜⎟------⎝⎠σ α av does not include the acceleration of gravity. 645 ice ⎝⎠tan 503 The combined transverse acceleration at any point along in stem area for vessels with class notation POLAR or the hull girder may be taken as: Icebreaker =0.8 hstem (m) in bow area outside stem area hstem = h as given for stem area. 3P 2 a = ------OI- F () m⁄ s t ∆ X

DET NORSKE VERITAS Rules for Ships, July 2006 Pt.5 Ch.1 Sec.4 – Page 24

FX = 1.5 at F.P. = 0.25 at midships = 0.5 at A.P. Linear interpolation shall be applied between specified positions.

POI as derived in 100. ∆ as defined in Sec.1 B100. 504 The maximum longitudinal acceleration is taken to be the same at any point along the hull girder.

1.1P tan()γφ+ 7P H 2 a = ------ZR - + ------ZR - () m⁄ s l ∆ ∆L Fig. 5 ϕ = maximum friction angle (between steel and ice), nor- Distribution of vertical shear force due to ramming and beaching mally taken as 10° H = distance in m from lowest waterline to position considered.

PZR as derived in 100. ∆ as defined in Sec.1 B100. γ as defined in A400.

E. Global Strength E 100 General 101 Hull girder shear forces and bending moments as stipulated in this subsection shall be combined with relevant stillwater conditions as stipulated for the main class. Wave load conditions as stipulated for the main class need not be regarded Fig. 6 as occurring simultaneously with the shear forces and bending Distribution of vertical bending moment due to ramming moments resulting from ramming and beaching. 102 The shear forces and bending moments shall be regarded as the design values at probability level equivalent to the maximum load in a service life of 20 years. 103 In addition to the maximum stress requirements given in this subsection, individual elements shall be checked with respect to buckling under the ramming and beaching load conditions, according to accept criteria as stipulated for the main class. E 200 Longitudinal strength 201 The following requirements are applicable to vessels with class notation Icebreaker and other POLAR class vessels (i.e. not to vessels with class notation ICE only). Fig. 7 202 The design vertical shear force at any position of the hull Distribution of vertical bending moment due to beaching girder due to ramming and/or beaching is given by: Q = k P (kN) ICE iq 203 The design vertical sagging bending moment at any po- k iq = 0.4 at F.P. sition of the hull girder due to ramming and/or beaching is giv- = 1.0 between 0.05 L and 0.1 L from F.P. en by: = 0.4 between 0.7 L and 0.2 L from A.P. MICE S = 0.25 kim P L (kNm) = 0.0 at A.P. k im = 0.0 at F.P. and A.P. Between specified positions kiq shall be varied linearly. Values = 1.0 between 0.25 L from F.P. to 0.35 L from A.P. for of kiq may also be obtained from Fig.5. ramming load condition = 1.0 between 0.3 L and 0.5 L from F.P. for beaching P = PZR as given in D100 or load condition. = PZB as given in D200, whichever is the greater. Between specified positions kim shall be varied linearly. Val- The thickness requirements for side shell and possible longitu- ues of kim may also be obtained from Fig.6 and Fig.7 for ram- dinal bulkhead platings shall be calculated for different cargo ming and beaching load conditions respectively. and ballast conditions as stipulated in Pt.3 Ch.1 Sec.5 D replac- ing QW with QICE as calculated above. P=P ZR or PZB as given in D100 or D200 for ramming and

DET NORSKE VERITAS Rules for Ships, July 2006 Pt.5 Ch.1 Sec.4 – Page 25

beaching load conditions respectively. and the mean shear stress over a web cross-section is not ex- σ L as defined in Sec.1 B100. ceeding 0.45 f . 204 The design vertical hogging bending moment at any position of the hull girder due to vibration following the initial ramming is given by: F. Local Strength M = 0.6 M (kNm) ICE H ICE SR F 100 General MICE SR = as given in 203 for ramming load condition. 101 The requirements in this subsection apply to members that may be directly exposed to local ice pressure. 205 The section modulus requirement about the transverse neutral axis is given by: 102 The buckling strength of web plates and face plates in girders and stringers subject to ice loads shall be checked ac- M + M cording to methods given in Pt.3 Ch.1 Sec.13 or equivalent. ------S ICE 3 ()3 Z = σ 10 cm 0.7 f 103 In curved regions of ice exposed plating, the stiffening is normally to be in the direction of the maximum curvature. MS = design stillwater bending moments according to 104 Framing in ice reinforced areas are in general to have Pt.3 Ch.1 Sec.5 B symmetrical cross-section with the web to the extent possible MICE = design bending moment due to ramming and/or positioned at right angle to the plane of the plate. The bending beaching, see 203 and 204. efficiency and tripping capacity of frames shall be documented The most unfavourable combinations of stillwater and ram- by calculations according to recognised methods as considered ming/beaching bending moments shall be applied. necessary. 206 The buckling strength of longitudinal strength members 105 Ice exposed knuckles are in general to be supported by in bottom, side and deck as well as longitudinal bulkheads sub- carlings or equivalent structures. ject to compressive and/or shearing loads shall be checked ac- 106 Plate fields adjacent to stem and possible knuckles in the cording to Pt.3 Ch.1 Sec.13. forward shoulder shall be supported so as to be of square shape E 300 Transverse strength amidships or otherwise locally strengthened to equivalent standard. 301 The line loads specified in D300 shall be applied at dif- F 200 Plating ferent water levels including LWL and BWL as found neces- 201 The thickness of plating exposed to patch load is gener- sary depending on the structural arrangement of the vessel. ally not to be less than: 302 The line loads shall be applied over one full hold/tank length or as found necessary to assess the structural strength of transverse bulkheads and decks supporting the ice reinforced 0.75 s k p regions. t23k= ------w o-+ t (mm) a 0.25 m σ k 303 The calculations of transverse strength amidships shall ho p f be based on the most severe realistic combination of ice compression loads and static load conditions. ka = aspect ratio factor for plate field 304 Recognised structural idealisation and calculation meth- = 1.1 − 0.25 s/ l, maximum 1.0, minimum 0.85 ods shall be applied. Effects to be considered are indicated in kw = influence factor for narrow strip of load (perpendicu- Pt.3 Ch.1 Sec.12 D200. lar to s) 305 The calculated stresses shall not exceed allowable 4.2 =1.3 – ------, maximum 1.0 stresses as stipulated in Pt.3 Ch.1 Sec.12 B400. 2 ()as⁄ + 1.8 E 400 Overall strength of substructure in the foreship mp = bending moment factor 401 The total impact forces as stipulated in D100 may have = f(b/s), see Table F1 (taking r as b/s) a decisive effect on primary structural systems in the foreship. a = s in general The loads are assumed to be evenly distributed in such a man- =ho for transversely stiffened panels ner that local pressures will not exceed those stipulated for lo- ho = h, see D400 cal members directly exposed to the load as given in D402. = s, whichever is the smaller 402 The design ramming load (not applicable to vessels with b = s in general ICE =h for longitudinally stiffened plating class notation only) taken as o 2 γ po = basic ice pressure in kN/m as calculated in D400 PZR/cos tk = corrosion addition as given in B500. shall be applied with its center on the stem line at the water line forward. The most unfavourable design draught forward shall s and l as defined in A400. be assumed with regard to positioning of the load. F 300 Longitudinal stiffeners 403 The design bow side impact load taken as POI should be positioned at various positions within bow side area consid- 301 Stiffeners in the bow-, midship- and stern ice reinforced ered critical for the overall strength of the substructure. areas which are largely parallel to the waterline are defined as longitudinals. Such parts of the bow side area which are aft of the border line of the flat side need normally not be considered with respect to POI. 302 The web sectional area of stiffeners in ice reinforced areas shall not be less than: 404 Recognised structural idealisation and calculation methods shall be applied. Effects to be considered are indicated in 1 – α 3.7()l – 0.5s h p Pt.3 Ch.1 Sec.12 D200. o o ()2 AW = ------α -A+ K cm 405 The equivalent stress as defined in Pt.3 Ch.1 Sec.12 τβsin l B400 shall not exceed σ . This is normally achieved for girder f σ type members when the bending stress is not exceeding 0.9 f and the web thickness shall not be less than:

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p 0.67 h h 0.33 t = 1.5 ⎛⎞------o - ⎛⎞------w o + t (mm) FRAME w ⎝⎠σ β ⎝⎠ k f sin ts y for flanged profiles. SIDESHELL

Table F1 Parameters for local strength formulas (general application) γ rmp me y 0.05 27.4 132.3 CENTRE LINE 0.10 14.25 67.9 0.15 9.87 46.5 PLAN VIEW 0.20 7.69 35.8 0.25 6.40 29.5 CENTRE LINE CENTRE 0.30 5.57 25.3 0.35 4.95 22.3

0.40 4.50 20.2 S I D 0.45 4.09 18.5 E S 0.50 3.77 17.2 H E L 0.60 3.31 15.4 L 0.70 3.02 14.1 θ 0.80 2.83 13.4 0.90 2.72 13.0 1.00 2.68 12.9 For intermediate values of r the parameters may be obtained by lin- FRAME VIEW (y-y) ear interpolation. Fig. 8 The section modulus shall not be less than: Determination of β-angle 1 – α 2 – α 41h l p w 3 Z = ------o o k- () cm σβsin F 400 Other stiffeners 401 The web sectional area shall not be less than: The stiffener connection area ao as defined in Pt.3 Ch.1 Sec.11 C400 shall not be less than: ()1 – α() 5.8ks hos l – 0.5s po 2 1 – α() A = ------A+ (cm ) 10cP 6.5ch0 l – 0.5s p0 2 W τ lsinβ K a ==------() cm 0 τβ α sin τβsin ()1.4l and the web thickness shall not be less than: ho = h, see D400 p 0.67 h s 0.33 = s, whichever is smaller t = 1.5⎛⎞------o - ⎛⎞------w - + t (mm) w ⎝⎠σ β ⎝⎠ k h = height of web in mm f sin ts w 2 po = basic ice pressure in kN/m as calculated in D400 for flanged profiles. τ = 0.45 σ σ σ f =0.9 f The section modulus shall not be less than: ts = shell plate thickness in mm. 2 1 – α 520l s p w σ o k ()3 s, l and y as defined in A400. Z = ------α cm m σ h sinβ -2 2 e o AK =tk hw 10 (cm ) wk = section modulus corrosion factor, see Pt.3 Ch.1 Sec.3 For end connections with brackets, section modulus including C1004 bracket shall be at least 1.2 Z. the bracket thickness is not to be c = factor as given in Table C4 of Pt.3 Ch.1 Sec.11 C400. less than t . α ≤ w = 0.5 for AC 1.0 = 0.15 for A > 1.0 The connection area ao as defined in Pt.3 Ch.1 Sec.11 C400 C shall not be less than: AC = as defined in D403 β = angle of web with shell plating. 2 α⎛⎞h α –1 tanγ 1 – 1 1 – β ⎛⎞------γ θ 5.8cs ⎜⎟10.1– ------()l – 0.5s h p =tan θ , and as shown on Fig.8 2 o o ⎝⎠sin ⎝⎠l 2 a = ------() cm 0 τlsinβ

3 2 ()C + 0.5h ()C + 0.5h k = 10.5+ ------1 o – 1.5------1 o s 3 2 l l =0.69 minimum C1 = arm length of bracket in m ho = h, see D400 =l, whichever is the smaller

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h1 =h =1.4 l, whichever is the smaller a = S in general hw = web height in mm =ho, maximum for girders supporting longitudinals me = bending moment factor b = l in general =f (ho/ l), see Table F1 (taking r = ho/ l) in general =ho, maximum for girders supporting non-longitudinal frames 8 =------ho = h, see D400 p = basic ice pressure in kN/m2 as given in D400 ho ho o ⎛⎞2 – ------τ =0.45 σ ⎝⎠l l σ σ f =0.9 f in general =0.8 σ when both ends are simply supported for stiffener with simply supported ends α f ≤ = 0.5 for AC 1.0 2 = 0.15 for A > 1.0 po = basic ice pressure in kN/m , see D400 C τ = 0.45 σ AC = as given in D403 σ σ f β = angle of web with shell plating. =0.9 f in general =0.8 σ when both ends are simply supported f l and S as defined in A400. ts = shell plate thickness in mm. A and w , see 302. σ K k s, l and y as defined in A400. -2 2 Table F2 Shear factor ks AK =tk hw 10 (cm ) wk = section modulus corrosion factor, see Pt.3 Ch.1 Sec.3 C1004 c = factor as given in Table C4 of Pt.3 Ch.1 Sec.11 C400 r α ≤ =0.5 for AC 1.0 = 0.15 for AC > 1.0 AC = as given in D403 0.0 1.00 1.00 1.00 β = angle of web with shell plating. 0.1 0.99 0.99 0.95 F 500 Girders 0.2 0.96 0.98 0.90 0.3 0.92 0.96 0.85 501 Within ice reinforced areas, girder structures supporting shell stiffeners shall be considered for ice loading. The ice load 0.4 0.87 0.93 0.80 area to be applied for the girder system will depend on the 0.5 0.81 0.89 0.75 structure considered, its position and orientation etc. The ice 0.6 0.75 0.85 0.70 pressure load and load area are generally to be taken as given 0.7 0.69 0.80 0.65 in D403. 0.8 0.62 0.74 0.60 502 For girders being part of a complex system of primary 0.9 0.56 0.69 0.55 structures, analysis by direct calculation may be required. For 1.0 0.50 0.63 0.50 such girder structures in the foreship, the requirements given in E400 apply. 1.1 0.5-0.05 i 0.63-0.06 i 0.5-0.05 i 1.2 0.5-0.10 i 0.63-0.12 i 0.5-0.10 i 503 The following requirements apply to evenly spaced girders for which the ends may be considered as fixed, simply sup- 1.3 0.5-0.15 i 0.63-0.18 i 0.5-0.15 i ported or constrained due to repetitive continuation of the 1.4 0.5-0.20 i 0.63-0.24 i 0.5-0.20 i girder beyond the support. The stiffness of supported members 1.5 0.5-0.25 i 0.63-0.30 i 0.5-0.25 i (frames or longitudinals) is assumed to be much smaller than i = b/2s. maximum = 1.0 the stiffness of the girder considered. The web sectional area at any point along a girder shall not be less than: G. Hull Appendages and Steering Gears 5.8 k abp s o ()2 AW = ------A+ K cm G 100 General τβ α sin AC 101 Sternframes, rudders, propeller nozzles and steering and the section modulus shall not be less than: gears are in general to be designed according to the rules given 2 in Pt.3 Ch.3 Sec.2 and Pt.4 Ch.14 Sec.1. 550S bp w Z = ------o k- 102 Additional requirements for ice reinforced vessels are σβα given in the following. For vessels with rudders which are not me sin AC located behind the propeller, special consideration will be made with respect to the longitudinal ice load. ks = shear factor, see Table F2 (taking r as (a + s)/S) s = spacing of secondary members in m 103 Plating materials in rudders, propeller nozzles and rud- me = bending moment factor der horns shall be in accordance with Sec.7. Forged or cast ma- = f (a/S) in case of a continuous member, see Table F1 terials in structural members subject to lower design (taking r as a/S) temperatures than –10°C according to B100 shall be impact tested at 5°C below (colder than) design temperature. 24 =------in case of fixed ends 104 The rudder stock and upper edge of the rudder shall be a 2 a ⎛⎞3 – ⎛⎞------effectively protected against ice pressure. ⎝⎠⎝⎠S S 105 Aft of the rudder an ice horn with depth minimum = 0.8 8 hice or an equivalent arrangement shall be arranged. =------in case of simply supported ends a a 106 Exposed seals for rudder stock are assumed to be de- ⎛⎞2 – ⎛⎞------signed for the given environmental conditions such as: ⎝⎠⎝⎠S S

DET NORSKE VERITAS Rules for Ships, July 2006 Pt.5 Ch.1 Sec.4 – Page 28

— ice formation = 1.0 for vessels with class notations POLAR or Ice- — specified design temperature. breaker. G 200 Ice loads on rudders The force F shall be divided between rudder and ice knife ac- 201 An ice load area is defined on the rudder with a length cording to their support position. The force acting on the ice knife may generally be taken as: equal to the length of the rudder profile lr and height equal to the effective ice load height (h). The general design rudder FX()– X force (FR) is given by the following formula: F FK = ------0.85 ()X – X FR = 0.2 (h lr) K po (kN) K F z K = 1 + ------X = distance from leading edge of rudder to point of attack of the force F zbl – 0.01 L =0.5 l r (m) minimum z = distance from rudder bottom to centre of the assumed =0.67 l r (m) maximum ice load area in m XK = distance in m from leading edge of rudder to centre of zbl = distance from rudder bottom to the ballast waterline in ice knife. m L = as defined in Sec.1 B100 G 300 Rudder scantlings po = as given in D400. 301 The scantlings of rudders, rudder stocks and shafts, pin- The rudder force FR gives rise to a rudder torque (MTR) and a tles, rudder horns and rudder actuators shall be calculated from bending moment in the rudder stock (MB), which both will the formulae given in Pt.3 Ch.3 Sec.2, inserting the rudder vary depending on the position of the assumed ice load area, torque MTR, bending moments MB and rudder force FR as giv- and on the rudder type and arrangement used. en in 201, all multiplied by factor 0.7. In general the load giving the most severe combination of FR, 302 Provided an effective torque relief arrangement is in- MTR and MB with respect to the structure under consideration stalled for the steering gear, and provided effective ice stop- shall be applied in a direct calculation of the rudder structure. pers are fitted, the design rudder torque need not be taken greater than: The design value of MTR is given by: M = M − TR TRO M TR = FR (0.6 l r XF) (kNm) MTRO = steering gear relief torque in kNm. =0.15 FR l r minimum 303 For rudder plating the ice load thickness shall be calcu- XF = longitudinal distance in m from the leading edge of the rudder to the centre line of the rudder stock. lated as given in F200 using the basic ice pressure as given for the stern area reduced linearly to half value at the lower end of In lieu of direct calculation design values of MB and FR, appli- the rudder. cable for the rudder stock diameter at the lower end, may normally be taken as: 304 Scantlings of rudder, rudder stock, rudder horn, rudder stoppers and ice knife as applicable are also to be calculated for the rudder force given in 202 acting on the rudder and ice Spade rudders: knife, with respect to bending and shear. Allowable stresses as 0.85 given in F400. FR = 0.2 ( h l r) po (kN) MB = FR HB (kNm) G 400 Ice loads on propeller nozzles Semi spade rudders: 401 A transverse ice load area positioned at the level of the 0.85 nozzle center is defined on the nozzle with a length equal to the FR = 0.2 ( h l r) po (kN) nozzle length and a height equal to the ice load height h given by: MB = 0.5 FR HP (kNm) Balanced rudders: h = 0.8 hice in general =0.6 hice for nozzle directly inside of protecting struc- 0.85 H tures, e.g. other nozzle or propeller. F = 0.2() hl ⎛⎞1 + ------B p (kN) R r ⎝⎠o 2zbl – 0.02L 402 The following two alternative longitudinal ice load areas shall be considered: MB = 0.25 FR HH (kNm) — an area positioned at the lower edge of the nozzle with a HB = distance (m) from lower end of rudder to middle of width equal to 0.65 D and a height equal to the height of neck bearing the nozzle profile HP = distance (m) from lower end of rudder to middle of pintle bearing — an area on both sides of the nozzle at the propeller shaft level, with a transverse width equal to the height of the HH = distance (m) from centre of heel bearing to centre of nozzle profile and with a height equal to 0.35 D. Both neck bearing symmetric and asymmetric loading shall be checked. h = as given in D403. 202 An additional ice load area is defined on the uppermost D = nozzle diameter. part of the rudder including ice knife with a length equal to the 403 The design ice pressure p (in kN/m2) for the stern area rudder (including ice knife) ( lr) and height below the hull as given in D400 shall be assumed for the ice load areas spec- equal to the nominal ice height (hice). This gives rise to a force ified under 401 and 402 giving rise to a force (F) given by: (F) given by: F = k p A (kN) F = k p h l (kN) ice r A = ice load area as defined in 401 and 402 p = design ice pressure in kN/m2 in stern area as given in k = 0.7 in general D400 = 1.0 for vessels with class notations POLAR or Ice- k = 0.7 in general breaker.

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G 500 Propeller nozzle scantlings H. Welding 501 The scantlings of the propeller nozzle and its supports in the hull shall be calculated for the ice loads given in 400, with H 100 General stresses not exceeding allowable values given in F400. For 101 The requirements in this subsection apply to members nozzle plating the ice load thickness shall be taken as given in that may be directly exposed to local ice pressure and support F200 using the design ice pressure as given for the stern area. structures for these. Otherwise weld dimensions shall be in accordance with the rules for main class. G 600 Steering gear 601 The main steering gear shall be capable of putting the H 200 External welding rudder over from 35° on one side to 30° on the other side in 20 201 The welding of ice strengthened external plating to stiff- seconds, when the vessel is running ahead at maximum service eners and to webs and bulkheads fitted in lieu of stiffeners is in speed (corresponding to MCR) and at deepest ice draught. any case to have a double continuous weld with throat thick- 602 For the additional class notation Icebreaker the above ness which is not less than: time shall not exceed 15 seconds. 0.55 s p t = ------o + 0 . 5 t (mm) 603 The effective holding torque of the rudder actuator, at σ k safety valve set pressure, shall be capable of holding the rudder fw σ 2 in the preset position, when backing in ice, unless arranged in Where fw = yield strength in N/mm of weld deposit. See accordance with 302 and 604. Pt.3 Ch.1 Sec.11 and Pt.3 Ch.2 Sec.11. The holding torque means the rudder torque the actuator is ca- Need not be greater than: pable to withstand before the safety valve discharges. = 0.45 x plate thickness for mild steel, and The holding torque need normally not exceed the values given = 0.50 x plate thickness for high strength steel. in Table G1. If the welding method leads to deeper penetration than normal, the additional penetration can be included in the throat thick- Table G1 Values of holding torque ness. ICE-05 to -15 POLAR-10 to -30 Icebreaker Weld throat shall in no case be less than for main class require- 0.5 MTR 0.75 MTR MTR ments. MTR = as given in 201. H 300 Fillet welds and penetration welds subject to high 604 The torque relief arrangement, when installed, shall pro- stresses vide protection against excessive rudder ice peak torque, e.g. 301 In structural parts where high tensile stresses due to local when backing towards ice ridges. ice load act through an intermediate plate, the throat thickness The arrangement shall be such that steering capability is either of double continuous welds shall not be less than given by Pt.3 σ σ maintained or speedily regained after activation of such ar- Ch.1 Sec.11 C202, with = 0.77 i. rangement. σ i = calculated maximum tensile stress in abutting plate due 605 All hydraulic rudder actuators shall be protected by to ice load in N/mm2. means of relief valves. Discharge capacity at set pressure shall not be less than given in Table G2. 302 Where high shear stresses in web plates due to local ice load, double continuous boundary fillet welds shall have throat Table G2 Relief valve discharge capacity thickness not less than given by Pt.3 Ch.1 Sec.11 C302 with τ τ ICE-05 to -15 POLAR-10 to Icebreaker = 0.77 i. -30 τ i = calculated maximum shear stress due to ice load in N/ Rudder speed 4.5 5 6.5 mm2. (degrees/s) 606 Where practicable rudder stoppers working on the rudder blade or head shall be fitted. I. Machinery Systems G 700 Podded propulsors and azimuth thrusters I 100 Pneumatic starting arrangement 701 Vessels operating in ice and equipped with podded propulsors or azimuth thrusters shall be designed according to op- 101 In addition to the requirements given in Pt.4 Ch.6 Sec.5 erational mode and purpose stated in the design specification. for a vessel having a propulsion engine(s), which has to be re- If not given, it shall be assumed that the vessel will be intended versed for going astern, the compressors shall have the capac- for continuous operation astern. This information shall also be ity to charge the receivers in half an hour. stated in the ship's papers. I 200 Sea inlets and discharges 702 Ramming astern is not anticipated. 201 The sea cooling water inlet and discharge for main and 703 The structure (housings, struts, bearings etc) of the pod/ auxiliary engines shall be so arranged that blockage of strums thruster shall be dimensioned for basic ice pressures as given and strainers by ice is prevented. in D400 for stern area in accordance with requested class notation and the operational mode. In addition, the requirements in Pt.4 Ch.6 Sec.5 B302 and 704 Documentation of both local and global strength capac- B303 shall be complied with. ity of the pod and or thruster shall be submitted for class as- 202 At least one of the sea chests shall be sufficiently high to sessment. Recognised structural idealisation and calculation allow ice to accumulate above the pump suctions and cooling methods shall be applied. water tank inlet, arranged as follows: 705 The equivalent stress as defined in Pt.3 Ch.1 Sec.12 B400 shall not exceed σ . This is normally achieved for girder 1) The sea inlet shall be situated near the centre line of the y σ ship and well aft if possible. The inlet grids shall be spe- type members when the bending stress is not exceeding 0.9 y and the mean shear stress over a web cross-section is not ex- cially strengthened. σ ceeding 0.45 y 2) As a guidance for design the volume of the chest shall be

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about one cubic metre for every 750 kW engine output of 103 Grey cast iron is normally not accepted for components the ship including the output of the auxiliary engines nec- subject to ice shocks, as e.g. thrust bearing housings. essary for the ship's service. 104 Shafting systems equipped with specially designed me- 3) To allow for ice accumulation above the pump suction the chanical torque limiting devices are subject to special consid- height of the sea chest shall not be less than: eration. Such devices, when accepted, shall comply with redundancy type R2 in Pt.4 Ch.1 Sec.1 B108. h ≥ 1.53 V min s The torque limit is normally not less than 1.5 KA TO . For K and T , see 500. V =volume of sea chest according to item 2. A O s 105 Ice induced vibrations (repetitive ice chocks) in the The suction pipe inlet shall be located not higher than shafting system shall be considered. hmin/3 from top of sea chest. Forced torsional vibration calculations shall include an evalu- 4) The area of the strum holes shall be not less than four (4) ation of transient vibrations excited by ice on the propeller. times the inlet pipe sectional area. 106 For non-reversible machinery plants, special means Heating coils may be installed in the upper part of the chests. shall be provided for reversing the propellers stuck in ice. 203 A full capacity discharge branched off from the cooling J 200 Engine output water overboard discharge line shall be connected to the sea chests. At least one of the fire pumps shall be connected to this 201 The maximum continuous output of propulsion machin- sea chest or to another sea chest with de-icing arrangement. ery shall not be less than: P = 1.5 c c I N B [ 1 + 1.6 T + 27 (0.1 I N / T0.25)0.5 ] (kW) I 300 Sea cooling water arrangements s p 301 The sea cooling water inlets and discharges for main and cs = 1.0 for vessels with conventional «icebreaker stem» auxiliary engines shall be connected to a cooling water double = 0.9 + γ / 200; minimum 1.0, but need not exceed 1.2 bottom tank having direct supply from the sea chests. The cp = 1.0 for controllable pitch propeller cross-sectional area of the supply line between each sea chest = 1.1 for fixed pitch propeller and the cooling water tank shall be twice that of all pump suc- IN = ice class number (figure added to class notation) tions connected to the tank. B = moulded breadth at waterline (m), local increase in 302 Vessels with the class notation Icebreaker or POLAR way of stem area is normally not to be taken into ac- shall comply with 303 to 307. count 3 T = rule draught (m) 303 The cooling water tank volume in m shall be at least γ = stem angle (see Fig.1). 0.01 times the output in kW of the main and auxiliary engines. 304 The sea water suction line strainers required in Pt.4 Ch.6 202 When the vessel is provided with special means which Sec.5 shall be arranged outstream from the cooling water tank. will improve her performance in ice (e.g. air bubbling system), the input rating of machinery used for such purpose may be 305 The sea water cooling pumps shall be of the self-priming added to the actual rating of propulsion machinery. type or connected to a central priming system. The propeller rating is, however, not to be less than 85% of that 306 The sea water cooling and ballast piping shall be ar- required in 201. ranged so that water in the cooling water tank can be circulated through the ballast tanks for the purpose of spare cooling ca- 203 When the vessel is provided with a nozzle of efficient pacity in the case of blocked sea chests. design, a reduction of required engine output corresponding to increase of thrust in ice conditions will be considered. The re- 307 Arrangements providing additional cooling capacity duction is, however, not to exceed 20% of required output in equivalent to that specified in 301 through 306 may be consid- 201 and 202. ered. 204 Additional reduction of the required output may be con- I 400 Ballast system sidered for a vessel having design features improving her performance in ice conditions. Such features shall be documented, 401 Arrangement to prevent freezing shall be provided for either by means of model tests or full scale measurements. ballast tanks where found necessary. It is understood that such approval can be revoked, if experi- Guidance note: ence motivates it. Double bottom tanks are normally not required to be provided with arrangement to prevent freezing. J 300 Determination of ice torque and loads

---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e--- 301 Ice torque (TICE), used for determination of scantlings in propellers and shafting systems, shall be taken as follows: 2 TICE = m D (kNm) J. Propulsion Machinery and Propellers The factor m is given in Table J1 as function of ice class: J 100 General Table J1 Values of m Ice class m Icebreaker m 101 Special cold climate environmental conditions shall be taken into consideration in machinery design. ICE-05 16 ICE-05 21 ICE-10 21 ICE-10 30 102 Propellers and propeller parts (defined in Pt.4 Ch.5 Sec.1 A103) shall be of steel or bronze as specified in Pt.2 Ch.2. Nod- ICE-15 27 ICE-15 30 ular cast iron of Grade NV 1 and NV 2 may be used for relevant POLAR 33 POLAR 40 parts in CP-mechanism. Other type of nodular cast iron with elongation ≥ 12% may be accepted upon special consideration D = propeller diameter in m. for same purposes. Propeller shafts are subject to Charpy 302 For propellers running in nozzles of satisfactory design, V-notch impact testing at minus 10°C and the average energy the ice torque will be considered based on submitted documen- value shall be minimum 27 J. tation, e.g. measurements carried out on similar vessels.

DET NORSKE VERITAS Rules for Ships, July 2006 Pt.5 Ch.1 Sec.4 – Page 31

However, if nothing else is documented, the following may be used: σ 0.9– R ⁄ R 2 -----n------B ()3 -0.5 2 WBS=.15Sc0 r tr σ ⁄ mm TICE = (0.9 - 0.01 m D ) m D (kNm) y 0.9– RR R Large fragments of ice shall not have free access into or towards the front of the nozzle. 303 Axial loads in shaftline: S = 1.0 for CP-propellers = 1.25 for FP-propellers F = TH + 1.5 FLE (axial load, ahead) σ 2 y = yield stress of bolt material (N/mm ) F = 0.8 TH + FLE (axial load, astern) RB = radius to bolt plan (m). The axial load F shall be applied on the propeller side of the c t and σ as given in 404. thrust bearing. r, r n The bolts shall have a design which minimises stress concen- TH and FLE according to 400 and 500. trations in transition zones to threads and bolt head as well as J 400 Propeller in way of the threads, and reduces risk for plastic deformations in the threads. 401 The blade scantling requirements given in Sec.3 apply, 406 For all parts in the pitch control mechanism, which are except as given below. In calculations involving the ice torque, subject to variable ice loads, stress concentration shall be taken TICE according to 300 shall be applied. into consideration. Propeller blade scantlings of martensitic — austenitic and fer- 407 The blade fitting and other parts in the pitch control ritic — martensitic stainless steel may be specially considered. mechanism shall be designed to withstand all forces produced 402 Arrangement of propellers in ice classes ICE-15 and by the pitch control system at its maximum power. The forces POLAR-10 to -30 shall be such that large fragments of ice do shall be assumed to act towards one blade at a time. not have free access into the front of the propeller disc within Guidance note: 0.7 radius. The pitch control mechanism shall be designed for the following 403 When the outer sections of the propeller blade is not sub- dynamic ice loads: ject to special consideration according to Sec.3 J303, the blade tip thickness at the radius 0.95 R shall not be less than: FLE =TICE / 0.9 R (kN) at leading edge, F TE = - 0.5 FLE at trailing edge, 490 tm2D= ()+ ------(mm) applied at the 0.9 radius perpendicular to the blade plane at the σ b respective blade edges. D and σ as given in 404. Number of load cycles to be considered shall not be taken less b than one million for ice classes ICE-05 to -15 and infinitive for σ σ b shall not be taken higher than 2.5 y. POLAR-10 to -30 and class notation Icebreaker. The design pressure of the hydraulic system shall not be taken less than twice For propellers running in nozzles blade tip thickness smaller the pressure needed to produce the blade spindle torque based on than above may be accepted. The tip thickness, however, shall the above forces. The forces are assumed to act on one blade at a not be less than 3/4 of the above value. time only.

The thickness of the blade edge and the propeller tip is not to ---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e--- be less than 50% of minimum t as given above, measured at 1.25 t from the edge or tip, respectively. For propellers where 408 Fitting of the propeller to the shaft is given in Pt.4 Ch.4 the direction of rotation is not reversible, this requirement only Sec.1 as follows: applies to the leading edge and propeller tip. — Flanged connection in B300 404 The fitting of the propeller blades and the pitch control — Keyless cone connection in B400 mechanism shall withstand a design static load not less than: — Keyed cone connection in B500 2 σ c t (Considering 0°C sea water temperature) ------n r r - –6 FICE = 0.3 []⁄ 10 (kN) D0.9– RR R If the propeller is bolted to the propeller shaft, the bolt connection shall have at least the same bending strength as the propel- This load shall be applied on the blade at a radius 0.9 R and at ler shaft. an offset from blade centre axis of 2/3 l . e J 500 Propulsion shaft line reinforcement σ σ σ n = 0.37 b + 0.6 y 501 Determination of factors for ice reinforcement of shaft σ 2 b = ultimate tensile strength of the blade (N/mm ) line. σ 2 y = the blade yield stress or 0.2% offset point (N/mm ) cr = the length of the blade section at RR radius (mm) TO = torque (kNm) in the actual component T = ice torque (kNm) according to 300 tr = the corresponding thickness (mm) ICE D = propeller diameter (m) u = gear ratio (if no reduction gear, or for components R = D/2 (m) on the propeller side of a reduction gear use u = 1) I = equivalent mass moment of inertia in kgm2 based RR = radius to a blade section taken at the termination of the blade root fillet (rounded upwards to the nearest R/20), on torque of all parts on engine side of component under consideration. ref. cr and tr (m) le = distance from axis of rotation of the blade to the lead- Masses rotating with engine speed to be transformed according ing or trailing edge, whichever is the greater, at a radi- to: us of 0.9 R. 2 Iequiv = I actual u 405 Propeller blade bolts shall have a section modulus, re- In propulsion systems with hydraulic coupling, torque convert- ferred to an axis tangential to the bolt pitch diameter, not less er or electromagnetic slip coupling, the masses in front of the than: coupling shall not be taken into consideration

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It = equivalent mass moment of inertia of propulsion sys- c) When using the method in Pt.4 Ch.4 Sec.1 B208, the min- tem in kgm2. (Masses in front of hydraulic or electro- imum diameter in item 3 of that paragraph is to be multi- magnetic slip coupling shall not be taken into plied with: consideration.) 1 502 Application factor for diesel and or turbine machinery in ⎛ K Aice ⎞ 3 ⎜ ⎟ general: ⎝ 1.4 ⎠ T I but not less than 1.0 K =1 + ice Aice uT I In item 4 of same paragraph, the vibratory torsional stress 0 T τ v is replaced by: 503 Application factor for electric motor machinery or diesel τ = ⋅ ()− ⋅ machinery with hydrodynamic torque converter: v 0.5 K Aice 1 T0 τ 1) Diesel engine with torque converter or hydrodynamic cou- and is not to exceed C. pling: 507 Support and construction of the thrust bearing shall be designed to avoid excessive axial shaft movements caused by = TTC max + TiceI heavy axial forces when the propeller hits ice. K Aice T0 uT0I t The thrust bearing shall have static strength designed for not TTC max = maximum possible transmittable torque through less than the nominal thrust plus the static ice force as defined converter/coupling. in 404. The ice force is assumed to act in the axial direction. Both forward and astern directions shall be considered. 2) Electric motor drive: The basic static load ratings of roller bearings shall not be less = Tmax + TiceI than 2 times the load. K Aice T0 uT0IT For calculation of the bearing pressures in the ice conditions, T = motor peak torque (steady state condition). the following thrust force applies: max ± Alternatively to the above criteria, the ice impact load may be THI = 1.1 TH + 0.25 FLE 0.75 FLE (kN) documented by simulation of the transient dynamic response F = according to 407 in the time domain. For branched systems, such simulation is LE TH = mean «bollard thrust» of the propeller or 1.25 times the in general recommended. mean thrust at maximum continuous ahead speed, in 504 Regarding shaft connections, use KAice in Pt.4 Ch.4 kN. Sec.1 as follows: Calculated lifetime (B10) of roller bearings shall be minimum — Flange connections, see B300 40 000 h, by applying the load THI. — Shrink fit connections, see B400 508 For reduction gears, use K in Pt.4 Ch.4 Sec.2. — Keyed connections, see B500 Aice Axial ice load according to 507, when applicable, shall be con- 505 The diameter of the propeller shaft in way of aft bearing sidered with respect to bearing arrangement and stiffness of the and at least a length 2.5 times the required diameter forward of gear housing. propeller flange or hub, shall not be less than: 509 For clutches, use KAice in Pt.4 Ch.4 Sec.3 B100. 1 510 For torsional elastic coupling, use K in Pt.4 Ch.4 2 --- Aice ⎛⎞0.9σ c t 3 Sec.5 B200. ------n r dp = 1.16 ⎜⎟[]()⁄ σ (mm) ⎝⎠0.9– RR R y 2 cr t = actual value of blade section considered at the termina- K. Thrusters tion of the blade root fillet (rounded upwards to nearest 1/20 of R). K 100 General σ y refers to the shaft material. 101 Special cold climate environmental conditions shall be σ taken into consideration in the thruster design. n refers to the blade material, see 404. 102 c and t as given in 404. Means for heating and circulation of lubrication and hy- r draulic oil shall be provided. The propeller shaft diameter may be evenly tapered to 1.15 times the required intermediate shaft diameter between the aft K 200 Propulsion thrusters bearing and the second aft bearing. Forward of this bearing the 201 Thrusters, which are used for propulsion purpose, shall propeller shaft diameter may be reduced to 1.05 times the re- comply with the relevant requirements in J. quired diameter of the intermediate shaft (using material factor valid for propeller shaft). Guidance note: Any thruster intended to be used for propulsion in ice, not only The propeller shaft flange thickness (propeller fitting) shall be the main propulsion thrusters, is defined as propulsion thrusters at least 0.3 times the actual shaft diameter. The fillet radius in this context. shall be at least 0.125 times the actual shaft diameter. ---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e--- 506 The diameter of intermediate shafts shall be determined based on methods given in Pt.4 Ch.4 Sec.1 B201. 202 Steering gear for azimuth thrusters shall be designed to withstand all relevant ice loads. Both ice loads on propeller a) When using the classification note 41.4 the necessary re- nozzle (G400) and on propeller blade (J400) shall be consid- inforcement is determined by using KAice in the given cri- ered. teria. ≤ K 300 Other thrusters b) With KAice 1.4 the method in Pt.4 Ch.4 Sec.1 B206 may be used, i.e. no ice reinforcement beyond 1A1 rules. 301 For shafting the following applies:

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— Maximum peak torque, which may occur due to ice in the 303 Suitable calculations should be carried out and or tests propeller, shall be taken into consideration. conducted to demonstrate the following: — The load F in 303 shall be considered for the propeller shaft. 1) the ship, when operated in ice within approved limitations, Maximum permissible equivalent stress is 80% of the yield during a disturbance causing roll, pitch, heave or heel due stress or 0.2% proof stress of materials. to turning or any other cause, should maintain sufficient positive stability, and 302 For reduction gears the application factor (KA) shall be taken as minimum 1.2. 2) when riding up in ice and remaining momentarily poised 303 The propeller blade shall be designed to withstand a at the lowest stem extremity, should maintain sufficient peak load, without exceeding 80% of blade material yield or positive stability. 0.2% proof stress of: 304 Sufficient positive stability in paragraphs 303 1) and 2) T means that the ship is in a positive state of equilibrium with a F = ------(kN) 0.85Rsinα positive metacentric height of at least 150 mm, and a line 150 0.85 mm below the edge of the freeboard deck as defined in the applicable LL-Convention, is not submerged. T = maximum peak torque of prime mover (kNm) α 305 For performing stability calculations on ships that ride 0.85 = pitch angle at radius 0.85 R R = propeller radius (m). up onto the ice, the ship should be assumed to remain momentarily poised at the lowest stem or extremity as follows: The load F is assumed to apply at 0.85 R, perpendicular to the blade plane. — for a regular stem profile, at the point at which the stem contour is tangent to the keel line — for a stem fitted with a structurally defined skeg, at the point at which the stem contour meets the top of the skeg L. Stability and Watertight Integrity — for a stem profile where the skeg is defined by shape alone, at the point at which the stem contour tangent intersects L 100 Application the tangent of the skeg, or 101 Vessels with class notation Icebreaker or POLAR — for a stem profile of novel design, the position should be shall comply with the requirements of Pt.3 Ch.3 Sec.9 as well specially considered as the requirements of this subsection. — the same considerations shall be made for ships designed Guidance note: for breaking ice at the stern. The requirements contained in this section are based on the IMO MSC/Circ.1056 "Guidelines for Ships Operating in Arctic Ice- L 400 Requirements for damage stability covered waters" as applicable for polar classes 1 to 3. 401 The damage assumptions in 402 to 403 and the criteria

---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e--- in 407 and 408 shall be the basis of damage stability calculations. L 200 Documentation 402 The dimensions of an ice damage penetration should be taken as: 201 Documentation for approval — longitudinal extent 0.045 of deepest ice waterline length if — preliminary damage stability calculations centred forward of the point of maximum beam on the wa- — final damage stability calculations terline, and 0.015 of waterline length otherwise, (not required in case of approved limit curves, or if ap- — depth 760 mm measured normal to the shell over the full proved lightweight data are not less favourable than esti- extent of the damage, and mated lightweight data). — vertical extent the lesser of 0.2 of deepest ice draft, or of 202 Documentation for information longitudinal extent. — internal watertight integrity plan. 403 The centre of the ice damage may be located at any point between the keel and 1.2 times the deepest ice draft. The verti- 203 Details of above documentation are given in Classifica- cal extent of damage may be assumed to be confined between tion Note No. 20.1. the keel and 1.2 times the deepest ice draft. L 300 Requirements for intact stability 404 If damage of lesser extent than that specified above re- sults in a more severe condition, such lesser extent shall be as- 301 The initial metacentric height GM shall not be less than sumed. 0.5 m. 405 For pipes, ducts or tunnels situated within the assumed 302 Account shall be taken of the effect of icing in the stabil- extent of damage, see 500. ity calculations. 406 The following permeability factors shall be assumed: Guidance note: The realistic figures for thickness and density of the accumulated ice load may vary with different areas. In lack of detailed infor- – store rooms: 0.60 mation the following ice loads should be accounted for: – machinery spaces: 0.85 - 30 kg per square metre on exposed weather decks and gang- – tanks and other spaces: 0.95 ways – partially filled ballast tanks: consistent with minimum - 7.5 kg per square metre for projected lateral area of each side of the vessel above the water plane tank content. - the weight distribution of ice on discontinuous structures such as railings, rigging, posts and equipment shall be included by 407 Damage criteria at the final stage of flooding: increasing the total area for the projected lateral plane of the vessel's sides by 5%. The static moment of this area shall be — the final equilibrium waterline after damage shall be be- increased by 10%. low the edge of any non-watertight opening

— the final equilibrium heel angle after damage shall not ex- ---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e--- ceed 15°. This may be increased to 17° if the deck edge is

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not submerged 409 A maximum allowable VCG curve with respect to dam- — GZ after damage has at least 20° positive range beyond age stability shall be included in the stability manual. Other- equilibrium wise the damage stability approval shall be limited to the — maximum GZ of at least 0.10 m within 20° beyond the presented loading conditions. maximum equilibrium position. L 500 Requirements to watertight integrity 408 Damage criteria at the intermediate stages of flooding: 501 As far as practicable, tunnels, ducts or pipes which may cause progressive flooding in case of damage, shall be avoided — the waterline after damage shall be below the edge of any in the damage penetration zone. If this is not possible, arrange- non-weathertight opening ments shall be made to prevent progressive flooding to vol- — the heel angle after damage shall not exceed 25°. This may umes assumed intact. Alternatively, these volumes shall be be increased to 30° if the deck edge is not submerged assumed flooded in the damage stability calculations. — GZ after damage has at least 10° positive range beyond 502 The scantlings of tunnels, ducts, pipes, doors, staircases, equilibrium bulkheads and decks, forming watertight boundaries, shall be — maximum GZ of at least 0.05 m within 10° beyond the adequate to withstand pressure heights corresponding to the maximum equilibrium position. deepest equilibrium waterline in damaged condition.

DET NORSKE VERITAS Rules for Ships, July 2006 Pt.5 Ch.1 Sec.5 – Page 35

SECTION 5 SEALERS

A. General according to 202, shall be fitted in way of the strengthened side plating stated in 201. The top of intermediate frames shall be A 100 Classification connected to a horizontal girder of same depth as the frames 2 101 The requirements in this Section apply to vessels spe- and with a flange area not less than 10 cm . The horizontal cially built for catching. girder shall be attached to all side frames. 102 Vessels built in compliance with the following requirements may be given the class notation Sealer. C. Sternframe, Rudder and Steering Gear A 200 Hull form 201 The hull form of the vessel shall be suitable for naviga- C 100 Design rudder force tion in pack ice and shall be such that the ship cannot be 101 The scantlings shall be based on a rudder force 3 times pressed down by ice. The sides of the hull shall be convex, with the design rudder force for main class. the greatest breadth at the first continuous deck above the design waterline. The angle between the tangent to the ship's side C 200 Protection of rudder and propeller at the deck and the vertical shall not be less than 5 degrees. 201 Ice fins shall be fitted for protecting rudder and propeller.

B. Strength of Hull and Superstructures D. Anchoring and Mooring Equipment B 100 Ship's sides and stem D 100 General 101 The scantlings of shell plating, frames, girders and stem 101 are at least to be as required for ice class ICE–05, see Sec.4. The equipment may be as required for fishing vessels. B 200 Superstructures 201 Side plating in superstructures shall have increased E. Machinery thickness in an area extending not less than 1 m above the load waterline of the vessel or above deck if the vessel has no free- E 100 Output of propulsion machinery board mark. In the mentioned area the plate thickness forward of 0.25 L from F.P. shall not be less than: 101 The output shall not be less than 735 kW. If the vessel has a controllable pitch propeller, the output requirement may t = 10 + 0.08 L (mm) be reduced by 10%. Aft of 0.25 L from F.P. the plate thickness shall not be less than: E 200 Thrust bearing, reduction gear, shafting and propeller t = 7.5 + 0.06 L (mm) 201 The scantlings are at least to be as required for class no- 202 Frames in superstructures in way of crew accommoda- tation ICE–05, see Sec.4. tion shall have a section modulus at least 50% in excess of the requirement for main class. The frames shall have brackets at E 300 Machinery systems both ends. 301 For requirements to sea inlets and cooling water system, 203 Intermediate frames with section modulus as for frames see Sec.3 J602.

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SECTION 6 WINTERIZATION

A. General 109 Immersion suits shall be of the insulated type. 110 Engine room and other spaces containing important A 100 Classification equipment shall be fitted with heating unless the equipment 101 The requirements in this section apply to ships intended and piping installations are so designed and or heated that they for service in cold climate environments for longer periods. can operate at the lowest indoor temperature that can be gener- 102 The class notation WINTERIZED (design temp. °C) ated by the outdoor temperature defined in the notation, with may be assigned to ships complying with the requirements in realistic space ventilation. subsections B through D. 111 An ice search light shall be provided on the wheelhouse 103 The class notation WINTERIZED ARCTIC (design top. temp. °C) may be assigned to ships complying with the requirements in subsections B through E. Guidance note: C. Material for Low Temperature The information within the brackets state the design temperature in °C. C 100 Hull material

---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e--- 101 Material used in external structures above the ballast waterline, BWL, shall be appropriate for the design tempera- Guidance note: ture given in the class notation. External structure is defined as The design temperature is defined by the user when signing the the plating with stiffening to a distance of 0.5 meter inwards class contract. The design temperature reflects the lowest mean from the shell plating, exposed decks and sides of superstruc- daily average air temperature in the area of operation, and an ex- ture and deckhouses. The requirement also applies to masts. treme air temperature about 20°C below this may be tolerable to the structures and equipment from a material point of view. For 102 Steel grades shall be selected in accordance with Pt.2 calculations where the most extreme temperature over the day is Ch.2 Sec.1 and as given in the requirements of the DAT (spe- relevant, e.g. heat balances in ventilated spaces, the air tempera- cial features notation), in Sec.4 B. ture can be set 20°C lower than the design temperature in the notation. C 200 Materials for equipment

---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e--- 201 All equipment exposed to the low temperature and being important for ship operations shall be made from materials A 200 Documentation suitable for the design temperature specified in the class nota- 201 Documentation as specified for notations: tion. Documentation as specified for the selected ice class notation Guidance note: in Sec.3 or Sec.4, and for class notation DEICE in Pt.6 Ch.1 Cranes are outside of class scope and the material requirements Sec.5 shall be submitted. are therefore not considered relevant for cranes.

shall be submitted. ---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e--- 202 Additional documentation for WINTERIZED ARCTIC 202 Equipment for which 201 applies include, but is not lim- as specified for notations CLEAN in Pt.6 Ch.12, OPP-F in ited to: Pt.6 Ch.1 Sec.6 and RPS in Pt.6 Ch.2 shall be submitted. — windlass and chain stopper — mooring winches and associated equipment B. Ship Design and Arrangement — lifeboats and or rescue boat davits and winches — rudderstock with flanges and bolts if flanged connection B 100 Ship arrangement - Ice strengthening of hull, — cargo oil piping, vents and air pipes rudder, steering gear, propeller and propeller shaft — hatches for cargo holds and cargo tanks 101 The ship shall be built to an ice class notation according — strongpoint for emergency towing. to Sec.3 or Sec.4. 102 Life boats shall be located in deck-house recesses with Guidance note: protection from water spray. Free fall lifeboats are not accepted. Cables exposed to the low temperature should comply with the 103 Anchor windlass shall be located inside a deckhouse, or latest revision of CSA standard C22.2 No. 0.3 for impact test at inside a forecastle space. –35°C and bending test at –40°C.

104 The “Emergency towing arrangements” aft on tankers ---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e--- shall be located inside a deckhouse or in an under-deck space. 203 For equipment or parts of equipment fabricated from 105 The cargo manifold, and manifold valves on tankers plate material, steel grades according to requirements for pri- shall be located in a semi-enclosed deck house. mary structure (class III) in Sec.4 B, shall be used. 106 Safe access to the bow shall be arranged via an on-deck 204 For equipment or parts of equipment fabricated from trunk or under-deck passageway. forged or cast material, steel grades according to Pt.2 Ch.2 107 Navigation bridge wings shall be fully enclosed. Sec.5 G or Pt.2 Ch.2 Sec.7 F, respectively, shall be used. 108 A heated watchman’s shelter shall be arranged at the 205 For pipes, steel grades according to Pt.2 Ch.2 Sec.4 D gangway. shall be used.

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D. Anti-Icing, Anti-Freezing and De-icing E. Additional Requirements for Class Notation WINTERIZED ARCTIC (design temp.) D 100 General 101 The requirements for class notation DEICE shall be E 100 Ice strengthening and propulsion complied with. 101 The ship shall be built to an ice class notation according 102 In addition to 101 the following shall be complied with: to Sec.4. — anti-icing and or de-icing of mooring equipment 102 Propellers intended for propulsion shall be of the con- — de-icing and or anti icing of cranes covered by CRANE- trollable pitch (CP) type, when driven by diesel engines, or ei- notation ther of controllable pitch (CP) or fixed (FP) type when — de-icing arrangements for anchor chain electrically driven, provided that the electrical systems are de- — fire main and foam main, if applicable, shall be heat traced signed to provide 100% of the nominal torque from 100% to or located inside a heated passageway 20% of the rpm. — water pipes on open decks and in non-heated spaces shall be arranged self-draining or provided with heat tracing 103 The propeller material shall be made of stainless steel or — hydraulic oil systems on open decks and in non-heated a material providing equivalent low temperature properties. spaces shall be arranged with heating, alternatively special 104 The RPS notation is mandatory. hydraulic oil for low temperatures shall be used — forecastle deck and poop deck shall be provided with un- E 200 Enhanced oil pollution prevention der-deck heating to ease ice removal — horizontal surfaces of superstructure shall be provided 201 The requirements for class notation CLEAN shall be with heating to ease ice removal complied with. — thermal protection suits including face masks, gloves and 202 The requirements for class notation OPP-F shall be boots shall be provided for all crew members. complied with. — for design temperatures lower than –10°C the following requirements also apply: 203 For oil tankers the accidental oil outflow index: OM shall not exceed 0.01 calculated in accordance with revised MAR- — ballast tanks and fresh water tanks located partly or POL Annex I, Reg. 23. fully above ballast water line shall be provided with means for heating 204 Cargo oil lines shall be located under deck or inside a — fuel oil storage tanks shall be provided with sufficient deck trunk, except for the loading and unloading manifold. heating enabling transfer of fuel 205 Non- toxic and biodegradable oil shall be used for stern — fuel oil transfer lines exposed to the low temperature tube and CP propeller systems. environment shall have heat tracing — where heating of horizontal deck areas and or outdoor 206 The bunker capacity shall be sufficient for at least 30 passageways is required in accordance with 101, the days operation of the ship’s accommodation power, in addition heating capacity shall not be less than 450 W/m2. to what is needed for the transit distance.

DET NORSKE VERITAS Rules for Ships, July 2006 Pt.5 Ch.1 Sec.7 – Page 38

SECTION 7 DAT(-X°C)

A. General rion for the selection of steel grades. The design temperature for external structures is defined as the lowest mean daily av- A 100 Classification erage air temperature in the area of operation. This temperature is considered to be comparable with the lowest monthly mean 101 The requirements in this section apply to materials in − ships of any type intended to operate for longer periods in areas temperature in the area of operation 2°C. If operation is re- with low air temperatures (i.e. regular service during winter to stricted to «summer» navigation the lowest monthly mean Arctic or Antarctic waters). temperature comparison may only be applied to the warmer half of the month in question. The corresponding extreme low Vessels built in compliance with the requirements of Sec.7, temperature is generally considered to be 20ºC lower than the will be assigned the notation DAT(-XºC), indicating the de- design temperature. sign temperature applied as basis for approval. Mean daily average temperature is the statistical mean aver- A 200 Documentation age temperature for a specific calendar day, based on a number of years of observations (= MDAT). 201 Specification of design temperature. Monthly mean temperature is the average of the mean daily A 300 Definitions temperature for the month in question (= MAMDAT). 301 External structure is defined, with respect to design tem- Lowest mean daily temperature is the lowest value on the an- perature, as the plating with stiffening to a inwards distance of nual mean daily temperature curve for the area in question. For 0.5 metre from the shell plating, exposed decks and exposed seasonally restricted service the lowest value within the time of sides and ends of superstructure and deckhouses. operation applies. 302 Temperature terms definitions (see also Fig.1): Lowest monthly mean temperature is the monthly mean tem- Design temperature is a reference temperature used as a crite- perature for the coldest month of the year.

Fig. 1 Commonly used definitions of temperatures

MDHT Mean* daily high (or maximum) temperature MEHT Monthly extreme high temperature MDAT Mean* daily average temperature (ever recorded) MDLT Mean* daily low (or minimum) temperature MELT Monthly extreme low temperature MAMDHT Monthly average** of MDHT (ever recorded). MAMDAT Monthly average** of MDAT * Mean: Statistical mean over observation period (at least 20 years). MAMDLT Monthly average** of MDLT ** Average: Average during one day and night.

DET NORSKE VERITAS Rules for Ships, July 2006 Pt.5 Ch.1 Sec.7 – Page 39

B. Material Selection hull girder strength in general. — Appendages of importance for the main functions of the B 100 Structural categories vessel. Stern frames, rudder horns, rudder, propeller noz- 101 Structural strength members or areas are classified in 4 zles and shaft bracket. (To be class III for vessels with no- different classes for the purpose of selecting required material tations ICE, ICEBREAKER or POLAR). grades. The classes are generally described as follows: — Gutter bars of oil spill coamings attached to hull. — Structures for subdivisions. Class IV: — Structures for cargo, bunkers and ballast containment. — Strakes in the strength deck and shell plating amidships in- — Internal members (stiffeners, girders) on plating exposed tended as crack arrestors. to external low temperatures where class III and IV is re- — Highly stressed elements in way of longitudinal strength quired. member discontinuities. Class I: Class III: — Local members in general unless upgraded due to special — Plating chiefly contributing to the longitudinal strength. considerations of loading rate, level and type of stress, — Fore ship substructure in vessels with notations ICE- stress concentrations and load transfer points and/or con- BREAKER or POLAR. sequences of failure. — Aft ship substructures in vessels equipped with podded — Deckhouse structure not exposed to longitudinal stresses. propulsors and azimuth thrusters, and intended for contin- — Cargo hatch covers. uous operation astern. — Foundations and support structures for heavy machinery 102 The material class requirement may be reduced by one and equipment, including crane pedestals. class for: — Frames for windlasses, emergency towing and chain stopper. — laterally loaded plating having a thickness exceeding 1.25 times the requirement according to design formulas, Class II: — laterally loaded stiffeners and girders having section modulus exceeding 1.5 times the requirement according to de- — Structures contributing to longitudinal and/or transverse sign formulas.

Table B1 Classification of longitudinal and transverse strength members, plating Structural member Within 0.4L amidships Elsewhere (Within 0.2 L aft of amidships and 0.3 L forward of amidships in vessels with notation ICEBREAKER or POLAR)

Deck plating exposed to weather, in general. Side plating. Longitudinal bulkhead plating, in general. II II Transverse bulkhead plating. Bottom plating including keel plate. Strength deck plating. 2) Continuous longitudinal members above strength deck excluding longitudinal hatch coamings. III 5) II Upper strake in longitudinal bulkhead. Upper strake in top wing tank.

Sheer strake at strength deck.6) Stringer plate in strength6) deck. 1) Deck strake at longitudinal bulkhead 4) Bilge strake 3) IV III Continuous longitudinal hatch coamings7)

1) In ships with breadth exceeding 70 m at least three deck strakes shall be class IV amidships. 2) Plating at corners of large hatch openings shall be specially considered. Class IV shall be applied in positions where high local stresses may occur. 3) May be of class III amidships in ships with a double bottom over the full breadth and with length less than 150 m. 4) May be class II outside 0.6 L amidships. 5) May be class II if relevant midship section modulus as built is not less than 1.5 times the rule midships section modulus, and the excess is not credited in local strength calculations. 6) Not to be less than grade NV E/EH within 0.4 L amidships in ships with length exceeding 250 m. 7) Not to be less than grade NV D/DH. 8) Single strakes required to be of class IV or of grade NV E/EH and within 0.4 L amidships shall have breadths not less than (800 + 5 L) mm, need not exceed 1 800 mm, unless limited by the geometry of the ship’s design.

B 200 Selection of steel grades Plating materials of non-exposed members shall not be of low- 201 Plating materials for various structural categories as de- er grade than obtained according to Pt.3 Ch.1 Sec.2 Table B1 fined in 100 of exposed members above the ballast waterline and or Pt.3 Ch.2 Sec.2 Table B1. of vessels with class notation DAT (-XºC) shall not be of lower Cranes shall fulfil requirements in accordance with “Rules for grades than obtained from Fig.2 using the specified design Certification of Lifting Appliances”. temperature.

DET NORSKE VERITAS Rules for Ships, July 2006 Pt.5 Ch.1 Sec.7 – Page 40

100

→ 70

60 FH

Thickness (mm) Thickness 40

Steel grade → E/EH D/DH B/AH A Class IV -50 -40 -30 -20 -10 0

(Special) Class III -50 -40 -30 -20 -10 0 (Primary) Class II -50 -40 -30 -20 -10 0

ATEGORIES (Secondary)

TRUCTURAL C S Class I -50 -40 -30 -20 -10 0 Design temperature (oC) →

Fig. 2 Required steel grades

Guidance note: 202 Forged or cast materials in structural members subject to When the structural category is known the material grade can be lower design temperatures than −10°C according to B100 shall selected based on the design temperature and plate thickness. be impact tested at 5°C below the design temperature. E.g. if a 30mm plate is to 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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