Mobile Offshore Units (IV-6-2)

Rules for Classification and Construction IV Industrial Services

6 Offshore Technology

2 Mobile Offshore Units

Edition 2007

The following Rules come into force on June 1st , 2007

Germanischer Lloyd Aktiengesellschaft

Head Office Vorsetzen 35, 20459 Hamburg, Germany Phone: +49 40 36149-0 Fax: +49 40 36149-200 [email protected]

www.gl-group.com

"General Terms and Conditions" of the respective latest edition will be applicable (see Rules for Classification and Construction, I - Ship Technology, Part 0 - Classification and Surveys).

Reproduction by printing or photostatic means is only permissible with the consent of Germanischer Lloyd Aktiengesellschaft.

Published by: Germanischer Lloyd Aktiengesellschaft, Hamburg Printed by: Gebrüder Braasch GmbH, Hamburg IV - Part 6 Table of Contents Chapter 2 GL 2007 Page 3

Table of Contents

Section 1 Scope, Definitions and Procedures A. Scope, Application ...... 1- 1 B. Definitions ...... 1- 1 C. Design Review ...... 1- 2 D. Supervision of Fabrication and Installation ...... 1- 6 E. Testing and Commissioning ...... 1- 7

Section 2 Self-elevating Units A. General ...... 2- 1 B. Structure ...... 2- 1 C. Stability ...... 2- 3

Section 3 Column Stabilized Units A. General ...... 3- 1 B. Structure ...... 3- 2 C. Stability ...... 3- 4

Section 4 Surface Drilling Units A. General ...... 4- 1 B. Structure ...... 4- 2 C. Stability ...... 4- 2 D. Drilling Facilities ...... 4- 2 E. Safety Aspects ...... 4- 3

Section 5 Pipelaying Units A. General ...... 5- 1 B. Movement and Position Keeping ...... 5- 1 C. Structure ...... 5- 4 D. Watertight Integrity and Stability ...... 5- 4 E. Pipelaying Facility ...... 5- 5

Section 6 Well Stimulation Units A. General ...... 6- 1 B. Special Safety Aspects ...... 6- 1 C. Position Keeping ...... 6- 1 D. Well Stimulation Equipment ...... 6- 1 Chapter 2 Table of Contents IV - Part 6 Page 4 GL 2007

Section 7 Subdivision, Stability and Load Line A. General Remarks, Scope ...... 7- 1 B. Righting and Heeling Lever Curves ...... 7- 1 C. Intact Stability Criteria ...... 7- 2 1. Standard criteria ...... 7- 2 D. Inclining Test ...... 7- 3 E. Subdivision and Damage Stability ...... 7- 3 F. Extent of Damage ...... 7- 4 G. Watertight Integrity ...... 7- 5 H. Load Line ...... 7- 6

Section 8 Mooring Equipment A. General ...... 8- 1 B. Temporary Mooring Equipment ...... 8- 1 C. Positional Mooring Equipment ...... 8- 6

Section 9 Life-Saving Appliances A. General ...... 9- 1 B. Life-Saving Appliances ...... 9- 1 C. Arrangement of Lifeboats and Liferafts ...... 9- 2 D. Rescue Boats ...... 9- 4

Annex A List of Standards, Codes, etc. Quoted IV - Part 6 Index Chapter 2 GL 2007 Page 5

Index

A Accessories ...... 8-5 Alarm signals ...... 9-1 Anchor lines ...... 8-7 Anchoring systems ...... 8-6 Anchors ...... 8-2, 8-7 Application ...... 1-1

B Block coefficient CB ...... 1-2 Bottom mat ...... 2-3 Bracing members ...... 3-4 Breadth B ...... 1-1

C Chain cable manufacture ...... 8-11 Chain cables ...... 8-5, 8-8 Chain locker ...... 8-5 Class notation ...... 2-1, 3-1, 4-1, 5-1, 5-2, 6-1, 8-6 Column stabilized units ...... 3-1, 7-5, 7-7, 9-2 Columns, hulls footings ...... 3-3 Commissioning ...... 1-7 Construction portfolio ...... 1-4 Corrective actions ...... 1-7

D Damage ...... 7-4 Definitions ...... 1-1 Depth H ...... 1-1 Design review ...... 1-2 Documents ...... 1-2, 5-5, 8-1, 8-6, 8-17 Draught T ...... 1-2 Drilling ...... 2-1, 3-2, 4-2 Drilling well ...... 4-2 Dynamic position keeping ...... 3-1, 4-1, 5-2, 8-17

E Embarkation stations ...... 9-2 Equipment numeral ...... 8-2 Chapter 2 Index IV - Part 6 Page 6 GL 2007

F Frame spacing a ...... 1-2 H Hazards ...... 1-5 Heeling lever curves ...... 7-1 High holding power anchors ...... 8-2 Hull ...... 2-1 I Inclining test ...... 7-3 Intact stability ...... 7-2 J Jacking ...... 2-2 L Launching ...... 9-3 Legs ...... 2-2 Length L ...... 1-1 Lifeboats ...... 9-1 Liferafts ...... 9-2 Life-saving appliances ...... 9-1 Lifting appliances ...... 2-1, 3-1, 4-1, 5-1 Load line ...... 7-6 M Marking ...... 1-7, 8-15, 8-17 Materials ...... 8-9 Mooring equipment ...... 8-1 O Openings ...... 7-5 Operating manual ...... 1-4, 5-4, 5-5 P Penetrations ...... 7-5 Personal life saving appliances ...... 9-2 Pipelaying facility ...... 5-5 Pipelaying units ...... 5-1 Pollution prevention ...... 1-6 Position keeping ...... 5-1, 6-1 Positional mooring equipment ...... 3-1, 4-1, 5-2, 8-6 Preload capability ...... 2-3 Production processes ...... 1-6 IV - Part 6 Index Chapter 2 GL 2007 Page 7

R Rejection repair criteria ...... 8-15 Rescue boats ...... 9-4 Righting lever curves ...... 7-1

S Safety aspects ...... 4-3, 5-1, 6-1 Safety management plan ...... 1-5 Safety management system ...... 1-4 Sea trials ...... 1-7, 5-4 Self-elevating units ...... 2-1, 7-4, 7-7, 9-2 Stability ...... 2-3, 3-4, 4-2, 5-4, 7-1 Storm condition ...... 7-2 Structure ...... 2-1, 3-2, 4-2, 5-4 Studs ...... 8-13 Subdivision damage stability ...... 7-3 Supervision of fabrication ...... 1-7 Surface drilling units ...... 4-1 Surface units ...... 7-4, 7-6, 9-2

T Tanks ...... 3-3 Temporary mooring equipment ...... 8-1 Testing ...... 8-14 Testing accessories ...... 8-16 Towing ...... 2-1, 4-2, 5-2 Towing ballasting ...... 3-1

V Valves ...... 7-5

W Waste management ...... 1-6 Watertight integrity ...... 7-5 Wave clearance ...... 3-2 Well stimulation equipment ...... 6-1 Well stimulation units ...... 6-1 Well stimulation vessels ...... 6-1 Winch system ...... 8-17 Wind forces ...... 7-1 Wire ropes ...... 8-5 Chapter 2 Index IV - Part 6 Page 8 GL 2007

IV - Part 6 Section 1 B Scope, Definitions and Procedures Chapter 2 GL 2007 Page 1–1

Section 1

Scope, Definitions and Procedures

A. Scope, Application B. Definitions

1. Scope 1. Mobile offshore unit A mobile offshore unit is any mobile offshore struc- 1.1 In this Chapter the requirements for the dif- ture or vessel, whether designed for operation afloat or ferent types of mobile offshore units are defined. supported by the sea bed, built in accordance with these Rules and classed by GL and includes the entire 1.2 Types of units structure and components covered by these Rules.

− units connected to the sea bed by anchoring 2. Drilling unit (mooring) A drilling unit is any unit intended for use in offshore − units kept on position by dynamic position- drilling operations for the exploration or exploitation ing/propelling system of the subsea resources. − units connected by legs in jacked up condition 3. Selfpropelled unit 1.3 Materials used for construction of the hull A self-propelled unit is a unit which is designed for unassisted passage. All other units are considered as The following materials may be used for the main non-self-propelled. structure/hull:

− steel, normally 4. Length L

− concrete, in exceptional cases 4.1 Shiptype units The length L is the distance in metres on the summer 2. Application load waterline from the fore side of the stem to the after side of the rudder post, or the centre of the rudder 2.1 The following types of employment have to stock, if there is no rudder post. L is not to be less than be distinguished: 96 % and need not be greater than 97 % of the extreme length of the summer load waterline. In units − drilling/exploration with unusual stern and bow arrangement, the length L will be specially considered. − self-elevating drilling units 4.2 Other units − column stabilized drilling units The length L means 96 % of the total length on a − surface drilling units of ship or barge type waterline at 85 % of the least moulded depth H measured from the top of the keel, or the length from the − other types of drilling units foreside of the stem to the axis of the rudder stock on that waterline, if that be greater. In units designed with − production, e.g. oil/gas a rake of keel, the waterline on which this length is − processing/treatment measured shall be parallel to the designed waterline.

− storage or loading on/off 5. Breadth B − research, measurements The breadth B is the greatest moulded breadth of the unit. − construction / pipelaying 6. Depth H 2.2 Manning The depth H is the vertical distance, at the middle of Only units continuously manned in operation mode the length L, from the base line to the top of the deck are considered. beam at side of the uppermost continuous deck. Chapter 2 Section 1 C Scope, Definitions and Procedures IV - Part 6 Page 1–2 GL 2007

In way of effective superstructures the depth is to be mentation if that submitted is insufficient for an as- measured up to the superstructure deck for determin- sessment of the unit or essential parts thereof. This ing the unit’s scantlings. may especially be the case for plants and equipment related to new developments and/or which are not Effective superstructures are extending into the range tested on board to a sufficient extent. of 0,4 L admidship and their length exceeds 0,15 L. 2.1.3 Once the documents submitted have been 7. Draught T approved by GL they are binding on the execution of the work. Subsequent modifications and extensions The draught T is the vertical distance at the middle of require the approval of GL before becoming effective. the length L from base line to freeboard marking for summer load waterline. 2.2 Plans for the hull and design data

8. Block coefficient CB General specifications with an indication of the intended use, design life, location and environment, The moulded block coefficient CB at load draught T, place(s) and period of construction and the main based on the length L is defined as: stages of construction up to final assembly and/or installation at sea. moulded volume of displacement [m3 ] at T CB = Plans showing the scantlings, arrangements and details LBT⋅⋅ of the principal parts of the hull are to be submitted for approval before construction commences. These draw- 9. Frame spacing a ings have to clearly indicate the scantlings, types and grades of materials, joint details and welding, or other The frame spacing a will be measured from moulding methods of connection. These plans are to include the edge to moulding edge of frames. following, where applicable: − general arrangement 10. Further definitions − specification of the assumed loads For further definitions see Chapter 1, Section 1, B. − inboard and outboard profile − summary of distributions of fixed and variable weights C. Design Review − plan indicating design loads for all decks 1. Extent of review − transverse sections showing scantlings Examination or verification of the following will be − longitudinal sections showing scantlings undertaken: − design documents, such as load assessment and − decks including helicopter deck stress analyses (as far as applicable), reports on − framing model tests, design drawings − practical qualifications of manufacturing firms and − shell plating personnel − watertight bulkheads and flats − suitability of the materials used − structural bulkheads and flats − erection procedure of the structure on land and at the port − tank boundaries with location of overflows − transportation procedures and jack-up procedure, − structure in way of jacking or other elevating ar- if applicable rangements − critical review of safety management system, see 4. − hulls, pontoons, legs, footings, pads or mats − superstructures and deckhouses 2. Documents for approval − arrangement and details of watertight doors and hatches 2.1 General − anchor handling arrangements, mooring system 2.1.1 All documents have generally to be submitted to GL in German or English language. − welding details and procedures, pre- and post- treatments 2.1.2 The general scope of documents is defined in − lines or offsets 2.2 to 2.6, the detailed scope will be defined case by case. GL reserve the right to demand additional docu- − curves of form or equivalent data IV - Part 6 Section 1 C Scope, Definitions and Procedures Chapter 2 GL 2007 Page 1–3

− wind heeling moment curves or equivalent data 2.5 Calculations

− capacity plan 2.5.1 The following data and calculations are to be submitted in conjunction with the scantling plans, as − corrosion control arrangements may be applicable: − methods and locations for non-destructive testing, − structural analysis for relevant loading conditions manufacturer’s quality control methods and test as agreed with GL procedures − resultant forces and moments from wind, waves, where appropriate, general arrangement of equip- − current, mooring and other environmental loading ment including calculations associated with the taken into account in the structural analysis transfer/installation mode − effect of icing on structural loading, stability and In addition an arrangement plan of watertight com- windage area partments shall be submitted as early in the design stage as possible, for review of damage stability. This − stability calculations, both intact and damaged, drawing is to indicate the watertight bulkheads, decks over the appropriate range of drafts, including the and flats and all openings therein. Doors, hatches, transit conditions ventilators, etc. and their means of closure, are to be indicated. Piping and ventilation systems shall be − significant operational loads from drilling derrick shown in sufficient detail to evaluate their effects on and associated equipment, industrial items, etc, the watertight integrity after incurring damage. and other significant loadings

2.3 Plans for machinery and electrical equip- − calculations substantiating adequacy of structure ment and design data to transmit forces between legs and hull through the jacking or other elevating systems Plans are to be submitted showing the arrangement and details of: − evaluation of the ability to resist overturning while bearing on the sea bed − general arrangement of machinery installations and equipment 2.5.2 Submitted calculations are to be suitably referenced. Results from relevant model tests or dy- general arrangement and design details of propul- − namic response calculations may be submitted as sion system alternatives or as substantiation for the required calcu- − auxiliary machinery lations.

− steering gear 2.5.3 The choice of computer programs according to the “State of the Art“ is free. It is recommended to − boilers and pressure vessels use computer programs which are approved by GL in − general arrangement and particulars of the electri- advance as appropriate to solve the actual problems. If cal installation the computer programs to be used are not known to GL, they may be checked by GL through comparative − jacking system including description calculations with predefined test examples. Reference applications, already achieved approvals by other − bilge and ballast systems institutions and other relevant information shall be provided in advance. A generally valid approval for a − fire extinguishing systems computer program is, however, not given by GL.

− other pumps and piping systems The calculations have to be compiled in a way which − working gear as far as it has been agreed to be allows to identify and check all steps of the calcula- included in the design review tions with regard to input and output in an easy way. Handwritten, easily readable documents are acceptable. 2.4 Safety aspects Comprehensive quantities of output data shall be pre- − hazardous areas plan sented in graphic form. A written comment to the main conclusions resulting from the calculations has − arrangement plans of safety devices and equip- to be provided. ment, e.g. fire extinguishing plan, escape routes, life-saving appliances, structural fire protection 2.6 Further details − operating instructions, as far as related to safety The necessary documentation is indicated in further − safety management plans, where applicable detail in the relevant Chapters and Sections. Chapter 2 Section 1 C Scope, Definitions and Procedures IV - Part 6 Page 1–4 GL 2007

2.7 Distribution of documents − representative examples of loading conditions for The distribution of design documents according to 2.2 each approved mode of operation, together with – 2.6 will be agreed upon in each individual case, means for evaluation of other loading conditions depending on the organization on Owner's, contrac- − details of emergency shutdown procedures tor's and/or fabricator’s side, and the mandatory requirements of responsible Administrations. − identification of the helicopter used for the design of the helicopter deck and procedure for helicopter For the needs of GL, general descriptions, calculations operations and test reports have to be submitted in duplicate, structural plans, detail drawings and building/testing − safety checks and maintenance work to be carried specifications in triplicate, one copy of each being through returned to the remitter with the approval or review − emergency procedures and rescue operations notation. − operating booklet for helicopter operation, including helicopter data on which design is based 3. Operating instructions 3.2 Construction Portfolio (Booklet) 3.1 Operating Manual (Booklet) A set of plan copies showing the exact location and An Operating Manual or equivalent is to be placed on extent of application of different grades and strengths board of each unit. The booklet shall include the fol- of structural materials, together with a description of lowing information, as applicable in the particular the material and welding procedures involved, is to be case, so as to provide suitable guidance to the operat- placed on board. Any other relevant construction in- ing personnel with regard to safe operation of the unit: formation is to be included in the booklet, including restrictions or prohibitions regarding repairs or modi- − general description / main characteristics fications. − pertinent data for each approved mode of operation, including design and variable loading, envi- 3.3 The operating instructions will be subject to ronmental conditions for the execution of certain examination within the design review procedure only operations, e.g. jacking, drilling, etc. insofar as they are related to the specified loads and load cases to be applied, and to other safety matters − minimum anticipated atmospheric and sea tem- covered by these Rules. peratures − assumed seabed conditions and their control, 4. Safety management system scouring, etc. 4.1 Safety management procedures 1, may be − admissible draft, or required distance of certain subject to review by GL either parts from the water surface − based on an agreement with the Owner/Operator, − general arrangement showing watertight compart- or ments, closures, vents, allowable deck loading, etc.; if permanent ballast is used, the weight, loca- − due to authorization and request by the competent tion and substance used are to be clearly indicated national Administration.

− hydrostatic curves or equivalent data 4.2 Safety management may be related to − capacity plan showing capacities of tanks, centres − personal safety of operating personnel, i.e. of gravity, free surface corrections, etc. − accident prevention − instructions for operation, including precautions to be taken in adverse weather, changing mode of − protection against exposure to toxic, radioactive operations, any inherent limitations of operations, or otherwise harmful substances etc. − general preventive and health control measures − plans and description of the ballast system and (alcohol, drugs control, etc.) instructions for ballasting − protection of the environment (sea, sea floor, at- − hazardous areas plan mosphere surrounding the installation) − light unit data on the results of an inclining experiment, etc. –––––––––––––– − stability information in the form of maximum KG 1 See IMO ISM (International Safety Manage- draught curve, or other suitable parameters based ment) procedures, to be introduced for mobile off- upon compliance with the required intact and sta- shore units from 1 July 2002 bility criteria IV - Part 6 Section 1 C Scope, Definitions and Procedures Chapter 2 GL 2007 Page 1–5

− operational safety/operability of the technical original plan, will be evaluated and duly incorpo- installations/systems on board rated in a revised SMP Obviously, an inter-relation exists with the operating − communication between operating personnel and manual according to 3., see also 4.4 and 4.6. responsible company management is ensured, including immediate and reliable information on 4.3 Safety Management Plan special/ abnormal incidents or events defined in the SMP, see 4.4.2. In relevant cases information 4.3.1 Safety management procedures shall be pre- to Authorities and GL is ensured. sented in the form of a Safety Management Plan − for any abnormal situations, e.g. repairs requiring (SMP), to be set up in each individual case, bearing in operational restrictions, the necessary additional mind the particular operational and environmental precautions are taken and any person possibly in- conditions to be expected as well as the applicable volved is aware of the existing danger legislation and regulations. 4.4.2 The SMP shall indicate follow-up measures 4.3.2 Preparation of a SMP will essentially consist and procedures for each case of failure or incident in an assessment of all foreseeable risks emerging considered. Responsibilities shall be clearly attributed from the planned activities, and in providing measures to members of the crew/installation personnel within and procedures to minimize these risks. The assess- each contingency procedure, and the paths or chains of ment will be based on existing experience and statisti- information clearly stated for the different cases. cal information regarding similar installations and activities. Proven methods of risk and failure analysis 4.4.3 For the unit in service, it shall be guaranteed including e.g. Fault-Tree or Event-Tree diagrams may by regular, and possibly additional, unprecedented, be used. checks, audits etc., that the measures provided by the 4.3.3 Corrective measures and amendments to the SMP are actually being observed. plan may be required following experience gathered Relevant documentation is to be kept on board and/or during the initial service period, see also 4.4. in the Operator’s headquarters for a period to be defined by the Administration, but not less than 5 years. 4.3.4 The SMP should take into account separately all relevant operational phases and situations and their specific risks, such as 4.5 Types of hazards − initial (start-up, test) period(s), also following Among aspects to be considered in assessing risks are important changes the following: − normal ("routine") operations 4.5.1 Hazards to personnel − operations under restricting conditions, e.g. − explosion, fire − due to extreme environmental impact − exposure (through contact, inhalation, ingestion) − during repairs, conversions, etc. to toxic, irritant or otherwise harmful gases, liquids, chemicals etc. − periods following an accident or failure − accidents due to operations with lifting gear/ ap- 4.4 Essential elements of a SMP pliances and machinery or tools 4.4.1 The SMP shall clearly show, through ade- − accidents due to environmental influences (icing, quate procedures and organizational provisions, that unit’s motions, bad visibility etc.) − routine controls, checks, measurements etc. are − noise/vibrations exceeding given ("tolerable") provided in order to ensure that physical properties limits and chemical processes remain stable and within prescribed limits, e.g. critical gas concentrations, 4.5.2 Hazards to the environment: exposure limits, pressures, ppm values; functioning of alarms − spills/loss of polluting (toxic or otherwise harmful) substances during "normal" - e.g., drilling - opera- − information and training of personnel is ensured, tions to the sea or sea floor, see 4.6.2 taking into account also possible language problems, like information on danger zones, “hazard- − spills of hydrocarbons, chemicals etc. during trans- ous areas“, alarms; handling of fire fighting and port/conveyance operations, see 4.6.1 rescue equipment, etc. − collision and grounding hazard, depending on − national regulations have been considered weather and traffic conditions − any (new) hazards becoming known, not taken − release of polluting (e.g. exhaust) gases to the into account or not sufficiently covered in the atmosphere, see 4.6.2 Chapter 2 Section 1 D Scope, Definitions and Procedures IV - Part 6 Page 1–6 GL 2007

− dropping of objects (e.g. wastes) to the sea/sea regulations. Unintentional escape of gases (leakage), floor, see 4.7 particularly in hazardous areas and to accommodation spaces, shall be avoided by precautions such as suit- − noise exceeding prescribed limits; may be relevant able arrangement of piping, ducts and exhaust open- in certain cases, e.g. in sensitive, protected areas ings/ intakes, sensors/measuring devices and alarms, pressurizing, according to the Rules, see Chapter 5 4.6 Pollution prevention during production and 6. and transport activities 4.7 Waste management 4.6.1 Transport/conveyance and storing operations 4.7.1 For sewage waste water the same applies as stated under 4.6.2.3 for waste water originating from 4.6.1.1 Loading and unloading operations, e.g. using the production process. The sewage residues shall be transport (supply) vessels and cargo handling equip- discharged or transported to corresponding installa- ment, shall be carried out observing weather imposed tions onshore. restrictions, see "operating instructions", and applicable safety and environment protection regulations. 4.7.2 Generally, no solid wastes whatsoever (sani- tary, food processing, production auxiliary materials 4.6.1.2 For the conveyance of oil/hydrocarbon prod- such as for cleaning, etc.) shall be dumped from an ucts from a production unit to a (shuttle) tanker, using offshore unit. Crew information and strict adherence articulated piping, swivels, flexible hoses etc., special shall be ensured by suitable measures such as publica- precautions - e.g., emergency shutdown and spill ar- tion (posters), regular instruction and supervision. resting devices - may be necessary, depending on environment conditions and regulations applicable to the location. For import/export flow lines (hydrocarbons produc- D. Supervision of Fabrication and Installation tion) see also 4.6.2. 1. General 4.6.1.3 Any harmful substances subject to controlled handling shall be allocated to defined, properly shel- 1.1 Supervision of the fabrication of individual tered and marked spaces. Liquids or substances capa- components and of the installation of the hull will ble of releasing harmful liquids under certain condi- generally take the form of inspections by the author- tions shall be stored in such a way that spills are pre- ized GL Surveyor to the extent considered necessary vented. by GL at any given time. 4.6.1.4 Reception/receiving, use/consumption and 1.2 GL branch (inspection) offices will receive, return/unloading of harmful or polluting substances for their supervisory work, previously examined, shall be constantly controlled and their volumes or documents from the Head Office, see C.2.7. Addition- weight noted. ally all technical documents connected with the rele- 4.6.2 Production and treatment processes vant construction project shall be made available to the Surveyors on request. 4.6.2.1 Suitable controls using measuring and monitoring techniques shall be provided to ensure safe 1.3 GL will assess the production facilities and conveyance of hydrocarbons and other polluting sub- procedures of the yard and other fabricators as to stances to and from the offshore unit, through flow whether they meet the requirements of GL Rules. In lines, risers, hoses, etc. general, approvals based on such assessments are conditional for acceptance of products subject to test- 4.6.2.2 For safe conveyance/transport of liquid and ing. gaseous substances on board of the production unit, between the different processing stations, the provi- 1.4 Materials, components, appliances and instal- sions of Chapters 5 and 6 have to be observed (mate- lations subject to inspection are to comply with the rial selection, design requirements, safety, monitoring relevant rule requirements and be presented for in- and alarm devices, etc.). spection and/or construction supervision by GL Sur- 4.6.2.3 Waste water, in connection with the produc- veyors, unless otherwise provided as a result of special tion process, shall be either collected in storage tanks approvals granted by GL. and discharged via auxiliary vessels or pipeline, or – if allowed by the competent Authority - pumped to the 1.5 It shall be the duty of the fabricator to inform sea after prescribed treatment/purification and under the competent inspection office of the completion of controlled conditions (monitoring of ppm values). important stages of the construction or of trials and inspections due. 4.6.2.4 Release of gaseous substances to the atmosphere, including flaring operations, shall occur under 1.6 In order to enable the Surveyor to fulfil his controlled conditions and according to the applicable duties, he is to be given free access to the unit and the IV - Part 6 Section 1 E Scope, Definitions and Procedures Chapter 2 GL 2007 Page 1–7

workshop, where parts requiring approval are fabri- E. Testing and Commissioning cated, assembled or tested. For performance of the tests required, the yard or fabricators are to give the 1. Program Surveyor every assistance by providing the staff and equipment necessary for such tests. An overall test or commissioning program including the complete, combined function of the unit as well as partial tests of the different systems has to be estab- 2. Supervision of fabrication lished. The detailed requirements for the overall function and the functioning of the different systems are 2.1 Aim of supervision defined in the following Chapters and Sections. The test program has to be approved by GL. During the phase of fabrication of an unit GL will ensure by surveys and inspections that: 2. Tests at fabricators − parts for hull and machinery and/or special equip- As far as practicable, machinery and equipment will ment requiring approval have been constructed in be subjected to operational trials on the fabricator's compliance with the approved drawings and par- test bed to the scope specified in the Construction ticulars Rules. This applies also to engines produced in large series. Where the machinery, equipment or electrical − all tests and trials stipulated by GL Rules are per- installations are novel in design or have not yet suffi- formed satisfactorily ciently proved their efficiency under actual service conditions on board ships or units , GL may require − workmanship is in compliance with current engi- performance of a trial under particularly severe condi- neering standards and/or GL Rule requirements tions. Upon completion of work, compartments, decks, − welded parts are produced by qualified welders bulkheads, etc. are to be tested as specified in the having undergone tests following Chapters and Sections. − test Certificates have been presented for components requiring approval (the fabricator will have 3. Sea trials to ensure that any parts and materials requiring Upon completion of the unit and/or the system/ approval will only be delivered and installed, if the equipment to be classed, all structure/hull, machinery appropriate test Certificates have been issued) and electrical installations will be subjected to operational trials in the presence of the GL Surveyor, prior − where no individual Certificates are required, type- to and during the sea trial. This will comprise, e. g.: tested appliances and equipment are employed in accordance with rule requirements − tightness, operational and load tests of tanks, covers, shell ports, ramps, etc. 2.2 Marking and attestation of individual − operational and/or load tests of the machinery and components installations (propulsion plant, electrical installations, steering gear, anchor equipment, etc.) of im- 2.2.1 Insofar as it is necessary to identify materials portance for safe operation or components during the fabrication process or possi- During a final survey, checks will be made to ensure bly also after commissioning, e.g. because of special that any deficiencies found, for instance during the sea properties of the material, a permanent mark is to be trial, have been eliminated. made by means of a stamp. 4. Report 2.2.2 The construction supervision, survey and/or final inspection of materials, parts supplied or installa- A test or commissioning report has to be established tion components, corresponding to the relevant speci- by the fabricator or Owner and to be agreed with the fications and GL Rules, will be attested by the Sur- GL Surveyor. veyor concerned on special forms, or informally, as agreed in the individual case. 5. Corrective actions If the tests according to the established test program, 3. Industrial equipment see 1., are partially or totally not satisfactory to the GL Surveyor, corrective actions have to be provided by Regarding working gear and special equipment, su- the fabricator or Owner and the relevant part of the pervision of construction and testing will be agreed tests repeated until a satisfactory result has been upon from case to case. reached.

IV - Part 6 Section 2 B Self-elevating Units Chapter 2 GL 2007 Page 2–1

Section 2

Self-elevating Units

A. General 2.6 Towing and elevating Conditions for towing, for the elevating and lowering 1. Definition procedures and for operating phases while standing on Self-elevating units have hulls with sufficient buoy- the sea floor, shall be clearly indicated in the Operat- ancy to safely transport the unit to the desired loca- ing Manual, compare Section 1, C.3.1. tion, after which the hull is raised to a predetermined elevation above the sea surface on its legs, which are 2.7 Drilling supported on the sea bed. Equipment and supplies may Drilling derricks shall be designed according to recog- be transported on the unit, or may be added to the unit nized codes/standards and/or applicable national regu- in its elevated position. The legs of such units may lations. The rated capacity for each reeving shall be penetrate the sea bed, may be fitted with enlarged included in the Operating Manual. sections or footings (spud cans) to reduce penetration, or may be attached to a bottom pad or mat. Self- Permanently installed piping systems for drilling op- elevating units are also known as Jack-up units. erations are to comply with recognised standard or code. The Class Notation SELF ELEVATING UNIT will be assigned for this type, see Chapter 1, Section 2, These Rules do not include requirements for the drill- C.2.3. ing of subsea wells or procedures for their control. Such drilling operations are subject to control by the coastal state. 2. Scope

2.1 This Section covers those specific design criteria and features of self-elevating mobile offshore B. Structure units which are not dealt with in the special Sections as referred to in the following. 1. General 1.1 The buoyant main structure (hull) of a self- 2.2 Subdivision and watertight integrity elevating unit shall be designed to resist the loads and Subdivision and watertight integrity are dealt with in stresses arising in the floating condition and while Section 7. Regarding stability see C. elevated. Chapter 4, Sections 1 to 4 apply.

2.3 Machinery and electrical installations 1.2 The unit is to be designed for a clearance of either 1,2 m, or 10 % of the combined storm tide, Machinery and electrical installations shall be de- astronomical tide and height of the maximum wave signed according to Chapters 5 and 6, respectively, as crest above the mean low water level, whichever is far as applicable. For the jacking installation, see less, between the underside of the hull in the elevated Chapter 5, Section 9 and Chapter 6, Section 12, I. position and the crest of the design wave. This crest elevation is to be measured above the level of the 2.4 Auxiliary installations and equipment combined astronomical and storm tides. See also Chapter 4, Section 2, B.4.10. Special (auxiliary) installations and equipment are to be designed according to the specific Sections as far as 1.3 Classification or Certification will be based applicable. See also Chapter 1, Section 1, D.2. upon the designer’s assumptions regarding the sea bed conditions. These assumptions shall be recorded in the 2.5 Lifting appliances Operating Manual. It is the responsibility of the Op- For the interaction of lifting appliances with the unit, erator to ensure that actual conditions do not impose its foundations, etc. Chapter 4, Section 8. more severe loading on the unit. The requirements for offshore cranes and other lifting 2. Hull appliances themselves are defined in the GL Rules VI – Additional Rules and Guidelines, Part 2 – Life Sav- 2.1 Structural elements such as the outer shell, ing Appliances, Lifting Appliances, Accesses, Chapter decks, bulkheads and girders shall be dimensioned 2 – Guidelines for the Construction and Survey of according to the principles outlined in Chapter 4, Lifting Appliances. Section 3. The GL Rules I – Ship Technology, Part 1 – Chapter 2 Section 2 B Self-elevating Units IV - Part 6 Page 2–2 GL 2007

Seagoing Ships, Chapter 1 – Hull Structures may be 4. Legs used as a basis where applicable, e.g. dimensioning of tank boundaries. 4.1 Leg types

2.2 The hull is to be considered as a complete Legs may be either shell type or truss type. Shell type structure having sufficient strength to resist all in- legs may be designed as either stiffened or unstiffened duced stresses while in the elevated position and sup- shells. According to the sea bed conditions envisaged, ported by all legs. All fixed and variable loads are to the legs may be designed with fixed or detachable be distributed, by an accepted method of rational footings, or bottom mats. analysis, from the various points of application to the supporting legs. The scantlings of the hull are then to be determined consistent with this load distribution, 4.2 Lower end but are not to be less than those required by the Rules Where footings or mats are not fitted, proper consid- defined in 2.1. Scantlings of units having other than eration shall be given to the leg penetration of the sea rectangular hull configurations will be subject to spe- bed and the corresponding end fixity of the legs. De- cial consideration. pending on the mat and type of connection, a rota- tional restraint of the leg may exist also in this case. 2.3 Deckhouses located near the boundary of the unit shall be designed to resist the possible impact of sea wash during conveyance. 4.3 Dimensioning

Deckhouses are to have sufficient strength for their 4.3.1 The legs of self-elevating units shall be de- size, function and location and are to be constructed to signed to resist the forces and bending moments re- approved plans. Their general scantlings are to be as sulting from the following operational conditions. The indicated in the Rules according to 2.1. Where they safety factors according to loading condition 2 accord- are close to the side shell of the unit, their scantlings ing to Chapter 4, Section 3, C. and D. apply. Fatigue may be required to conform to the requirements for may have to be specially considered, particularly for bulkheads of unprotected deckhouse fronts. legs of truss type. For fatigue criteria, see Chapter 4, Section 3, G. 2.4 Special attention is to be paid to the foundations and fastening of drilling derrick(s) and cranes, 4.3.2 Ocean transit condition also with regard to transit conditions. Legs shall be designed for acceleration and gravity moments resulting from the motions in the most se- 3. Structure in way of jacking vere anticipated environmental transit conditions, together with corresponding wind moments. Calcula- 3.1 Load carrying members which transmit loads tion or model test methods, acceptable to GL, may be from the legs to the hull are to be designed for the used. Alternatively, legs may be designed for a bend- maximum design loads and are to be arranged that ing moment resulting from a 15° single amplitude of loads transmitted from the legs are properly distrib- roll or pitch at a 10 second period, plus 120 % of the uted into the hull structure. gravity moment caused by the legs' angle of inclination (minimum design criteria).

3.2 For the elevated position, special attention is For ocean transit conditions, it may be necessary to to be paid to the distribution of the loads from the reinforce or support the legs, or to remove sections of supporting points (legs) into the hull structure, taking them. The approved condition is to be included in the account also of possible load redistributions resulting Operating Manual. from lack of support at one leg. 4.3.3 Field transit condition The structure surrounding the legs (points of support) shall be designed with particular regard to the intro- Legs are to be designed for a bending moment result- duction of local concentrated forces; main loadbearing ing from a 6° single amplitude of roll or pitch at the elements should be continuous in the vertical direc- natural period of the unit, plus 120 % of the gravity tion. moment caused by the legs' angle of inclination.

Regarding the maximal force to be transmitted, pre- The legs are to be investigated for any proposed leg loading of the legs shall be considered, see 4.5 below. arrangement with respect to vertical position during field transit moves, and the approved positions are to 3.3 For loose elements, e.g. bars, rods, bolts, be specified in the Operating Manual. pins, serving for transmission of forces to support the unit, special requirements may be imposed regarding Such investigation should include strength and stabil- dimensioning (safety factors) and testing. ity aspects. IV - Part 6 Section 2 C Self-elevating Units Chapter 2 GL 2007 Page 2–3

Field transit moves may only be undertaken when the 4.4.2 The envelope plating of tanks which are not predicted weather is such that the anticipated motions vented freely to the sea is not to be less in thickness of the unit will not exceed the design condition. The than would be required by the rules for tanks, using a duration of a field transit move may be for a consider- head to the design water level taking into account the able period of time and should be related to the accu- astronomical and storm tides, see 2.1. racy of weather forecasting in the area concerned. Such a move should not normally exceed a twelve 4.4.3 The effects of scouring on the bottom bearing hour voyage between protected locations, or locations surface should be considered. The effects of skirt where the unit may be safely elevated; however, dur- plates, where provided, have to be especially consid- ing any portion of the move, the unit is not normally ered. to be more than a six hour voyage away form a pro- 4.4.4 Mats are to be designed to withstand the tected location or a location where the unit may be loads encountered during lowering including the safely elevated. The approved condition is to be in- shock of touching bottom while the unit is afloat and cluded in the Operating Manual. subject to wave motions. 4.3.4 Condition while lowering legs 4.4.5 Provisions for ballasting and de-ballasting the mat have to be installed. These may be pipelines run- Legs are to be designed to withstand the dynamic and ning down each leg into the mat to vent off trapped air current loads which may be encountered along their during ballasting or to induce air for displacing the unsupported length just prior to touching bottom, and water and thus de-ballasting the mat. These pipelines also to withstand the shock of touching bottom while may also be used to blow air under the bottom of the the unit is afloat and subject to motions caused by mat with the aim of facilitating the lifting of the mat waves and wind. from the bottom of the sea. The maximum design motions, water depth, bottom 4.5 Preload capability conditions and sea state while lowering legs are to be For units without bottom mats, all legs are to have the clearly indicated in the Operating Manual, and the legs capability of being preloaded to the maximum appli- are not to be permitted to touch bottom when the site cable combined gravity plus overturning load. The conditions exceed the allowable. approved pre-load procedure shall be included in the Operating Manual. 4.3.5 Condition while elevating the unit Regarding the preloading capability of the elevating The legs are to be designed to withstand the loads machinery, see Chapter 5, Section 9. acting on both, the unit’s hull and the legs themselves, during the elevating procedure. The environmental conditions are the same as foreseen for lowering of the C. Stability legs (4.3.4). 1. General The analysis may have to be done for several interme- The general requirements for stability are defined in diate positions of the hull. Section 7. Additional aspects are given in the following. 4.3.6 Elevated (working) condition 2. Overturning Stability The largest possible overturning moments shall be considered, using the most adverse combination(s) of 2.1 The unit, when resting on the sea bed, is to applicable variable and environmental and gravity have sufficient downward gravity loading on the sup- loadings. Forces and moments due to lateral frame port footings or mats to withstand the overturning deflections of the legs are to be taken into account. moment of the combined environmental forces from any direction, for each design loading condition. The Eccentricity of support or partial restraint of the lower overturning safety, defined as the sum of the restoring leg ends may have to be considered (e.g. for spud can moments divided by the sum of the overturning mo- design), depending on the soil conditions. The analysis ments, should not be less than: will usually have to be carried through for several − 1,5 for loading condition 2 water depths and corresponding site and environmental conditions. − 1,3 for loading condition 3 according to Chapter 4, Section 3, C. 4.4 Bottom mat 2.2 It is assumed that noticeable inclinations of 4.4.1 If the sea bed conditions are characterized by the unit will not occur or will be corrected immedi- very soft mud and silt, the lower ends of the legs are to ately, and that the effects of any dangerous changes of be attached to a mat. Particular attention is to be given the sea bed will be kept under control. Corresponding to the attachment and the framing and bracing of the instructions shall be contained in the Operating Man- mat, in order that the loads are properly distributed. ual.

IV - Part 6 Section 3 A Column Stabilized Units Chapter 2 GL 2007 Page 3–1

Section 3

Column Stabilized Units

A. General 2.4 Positional mooring equipment Mooring equipment for position keeping at the work- 1. Definition ing location is defined in Section 8, C. Column stabilized units depend upon the buoyancy of widely spaced columns for floatation and stability for 2.5 Dynamic position keeping all afloat modes of operation or in the raising or low- Dynamic position keeping at the working location ering of the unit, as may be applicable. The columns means maintaining a desired position within the nor- are connected to an upper structure supporting e.g. mal excursions of the control system and under de- drilling equipment or accommodation quarters. Lower fined environmental conditions. The required position hulls or footings may be provided at the bottom of the tolerances during drilling operations have to be de- columns for additional buoyancy or to provide suffi- fined by the Owner/Operator. cient area to support the unit on the sea bed. Bracing members of tubular or structural sections may be used The complete dynamic positioning system requires the to connect the columns, lower hulls or footings, and to following sub-systems: support the upper structure. − power system Operations may be carried out in the floating condi- − thruster system tion, in which condition the unit is described as a Semi-Submersible Unit, or when the unit is supported − control system by the sea bed, in which condition the unit is described Thrusters used as sole means of position keeping shall as a Submersible Unit. A Semi-Submersible Unit may provide a level of safety equivalent to that provided be designed to operate either floating or supported by for mooring arrangements to the satisfaction of GL. the sea bed, provided each type of operation has been found to be satisfactory and suitable. The Class Notations DP 1 to DP 3 will be assigned if the unit is equipped with such a system, compare The Class Notation COLUMN STABILIZED UNIT Chapter 1, Section 2, C.2.7. will be assigned for this type, compare Chapter 1, Section 2, C.2.3. Further details are defined in the Chapter 5, Section 6, E. 2. Scope 2.6 Auxiliary installations and equipment 2.1 This Section covers those specific design Special (auxiliary) installations and equipment are to criteria and features of column stabilized mobile off- be designed according to the specific Sections as far as shore units which are not dealt with in other Sections, applicable. See also Chapter 1, Section 1, D.2. as referred to in the following. 2.7 Lifting appliances 2.2 Subdivision and watertight integrity For the interaction of lifting appliances with the unit, Subdivision and watertight integrity are dealt with in their foundations, etc. see Chapter 4, Section 8. Section 7. Regarding stability see C. Each elevator cabin in a column shall provide for an emergency exit with an escape ladder in the hoistway. 2.3 Machinery and electrical installations The requirements for offshore cranes and other lifting Machinery and electrical installations shall be de- appliances themselves are defined in the GL Rules VI signed according to Chapters 5 and 6, respectively, as – Additional Rules and Guidelines, Part 2 – Life Sav- far as applicable. For ballast and bilge pumping ar- ing Appliances, Lifting Appliances, Accesses, Chapter rangements see Chapter 5, Section 13e, H. and I. and 2 – Guidelines for the Construction and Survey of Chapter 6, Section 12, J. Lifting Appliances. Propulsion installations, designed for conveyances 2.8 Towing and ballasting under own power or for towage assistance, and/or for positioning, shall also be designed according to Chap- Conditions for towing, for ballasting and deballasting ters 5 and 6 and according to the GL Rules I – Ship procedures and for mooring operations shall be clearly Technology, Part 1 – Seagoing Ships, Chapters 2 and indicated in the Operating Manual, compare Section 1, 3, as applicable. C.3.1. Chapter 2 Section 3 B Column Stabilized Units IV - Part 6 Page 3–2 GL 2007

2.9 Drilling 1.4 Stress and motion analysis

Drilling derricks shall be designed according to recog- 1.4.1 As the design of column stabilized units is nized codes/standards and/or applicable national regu- governed by both, structural and motion behaviour, lations. The rated capacity for each reeving shall be calculations will have to be presented for approval included in the Operating Manual. covering both aspects. The investigation shall be carried out for a sufficient number of draughts and envi- Permanently installed piping systems for drilling op- ronmental conditions in order to determine the most erations are to comply with an recognised standard or severe cases of stressing and the associated motions, code. and vice versa.

These Rules do not include requirements for the drill- Model tests may serve as additional basis for design. ing of subsea wells or procedures for their control. 1.4.2 For units of this type, the highest stresses Such drilling operations are subject to control by the may be associated with less severe environmental coastal state. conditions than the maximum specified by the Owner/designer. Where considered necessary by GL, account shall be taken of the consequent increased possibility of encounter of significant stress levels, by B. Structure either or both of the following: − suitable reduction of the allowable stress levels for 1. General combined loading defined in Chapter 4, Section 3, D. 1.1 Structural design shall be based on the prin- − detailed investigation of fatigue properties ciples described in Chapter 4, Sections 1 to 4, see also Particular attention shall also be given to the details of 1.4. Particular attention should be given to structural structural design in critical areas such as bracing details in critical areas such as connections of bracing members, joint connection, etc. members, where high local loads are acting, see also 3.7 and Chapter 4, Section 3, B. and Section 4, B. – D. 1.5 Structural redundancy

1.2 For the dimensioning of ship-like structural 1.5.1 When assessing structural redundancy for members such as decks, bulkheads, deck houses, gird- column stabilized units, the following assumed dam- ers and pillars, the GL Rules I – Ship Technology, age conditions shall apply: Part 1 - Seagoing Ships, Chapter 1 – Hull Structures may be used as a design basis. 1.5.1.1 The unit’s structure shall be able to withstand the loss of any slender bracing member without causing overall collapse of the unit’s structure. 1.3 Wave clearance 1.5.1.2 Structural redundancy will be based on the 1.3.1 Afloat condition applicable requirements of Chapter 4, Sections 2 to 4, except: Unless deck structures are designed for wave impact, − maximum calculated stresses in the structure re- to the satisfaction of GL, reasonable clearance be- maining after the loss of a slender bracing member tween the deck structures and the wave crests is to be are to be in accordance with Chapter 4, Section 3, ensured for afloat modes of operation, taking into D. These criteria may be exceeded for local areas, account the predicted motion of the unit relative to the provided redistribution of forces due to yielding or surface of the sea. Calculations, model test results or buckling is taken into consideration. reports on past operating experience with similar configurations showing that adequate provision is made to − When considering environmental factors, a one maintain this clearance are to be submitted. year return period may be assumed for intended areas of operations, see Chapter 4, Sections 2. 1.3.2 On-bottom condition 1.5.2 The structural arrangement of the upper hull The unit is to be designed for a clearance of either 1,2 is to be considered with regard to the structural integ- m, or 10 % of the combined storm tide, astronomical rity of the unit after the failure of any primary girder. tide and height of the maximum wave crest above the mean low water level, whichever is less, between the 2. Upper structure underside of the hull in the elevated position and the crest of the design wave. This crest elevation is to be 2.1 The scantlings of the upper structure are not measured above the level of the combined astronomi- to be less than those required by the Rules mentioned cal and storm tides. See also Chapter 4, Section 2, above, in association with the loading indicated on the B.4.10. deck loading plan. In addition, when the upper struc- IV - Part 6 Section 3 B Column Stabilized Units Chapter 2 GL 2007 Page 3–3

ture is considered to be an effective member of the lings are not to be less than required for watertight overall structural frame of the unit, the scantlings are bulkheads in association with a head equivalent to the to be sufficient to withstand actual local loading plus maximum waterline in damaged condition; for all any additional loading superimposed due to frame areas subject to wave immersion, a minimum head of action, within the stress limitations given in Chapter 4, 6,0 m shall be used. Section 3, D. 3.3 Where columns, lower hulls or footings are 2.2 When an approved mode of operation or designed as shells, either unstiffened or ring stiffened, damage condition in accordance with the stability the minimum scantlings of shell plating and ring stiff- requirements allows the upper structure to become eners are to be determined on the basis of established waterborne, special consideration shall be given to the shell analysis using the appropriate safety factors and resulting structural loading. the design heads as given in 3.2, see also Chapter 4, Section 3, G.4. 2.3 Tanks 3.4 Openings in columns, like portlights or win- 2.3.1 Tanks for fresh water or fuel oil, or other dows, including those of the non-opening type, or tanks which are not intended to be kept entirely filled other similar openings are not to be fitted in columns. in service, are to have divisions or deep swashes as Regarding openings in external and internal walls, may be required to minimize the dynamic stress on the bulkheads, etc. see also Section 7, G. structure. Tight divisions and boundary bulkheads of all tanks are to be constructed in accordance with the Rules according to 1.2. The arrangement of all tanks, 3.5 Scantlings of columns, lower hulls or foot- together with their intended service, and the height of ings as determined according to 3.2 and 3.3 are mini- the over-flow pipes are to be clearly indicated on the mum requirements for hydrostatic pressure loads. plans submitted for approval. Consideration is to be Where wave and current forces, or bottom contact given to the specific gravity of the liquid in the tank. pressure in case of units resting on the sea bed are superimposed, the local structure of the shell is to be 2.3.2 Tanks are to be tested in accordance with the increased in scantlings as necessary, to meet the Rules and/or specifications. strength requirements mentioned in 1.1 above. Scant- lings in tanks are to be determined for both, full and empty conditions. 2.4 Deckhouses fitted to the upper structure are to be designed in accordance with the Rules defined in 1.2, with due consideration given to their location and 3.6 When the column, lower hull or footing is an to the environmental conditions in which the unit will effective member of the overall structural frame of the operate. unit, the scantlings are to be sufficient to meet the requirements of this paragraph plus any additional stress superimposed due to frame action, within the 2.5 Local structures in way of fairleads, winches, stress limitations of Chapter 4, Section 3, D. etc., forming part of the positional mooring system, shall be designed to the breaking strength of the mooring line. 3.7 Particular consideration is to be given to structural details, reinforcements, etc., in areas subject to high local loading, or to such loading that may 2.6 Special attention is to be paid to the founda- cause shell distortion, for example: tions (supporting structure) and fastening of drilling derrick(s), cranes (see also Chapter 4, Section 8) and − sloshing in partially filled tanks similar installations. − bracing connection forces 3. Columns, lower hulls and footings − loads due to mooring operations − wave impact 3.1 Main stability columns and lower hull or footings may be designed as either framed or un- − bottom bearing loads, where applicable framed shells. In either case, framing, ring stiffeners, bulkheads or other suitable elements used are to be 3.8 Consideration shall be given to objects falling sufficient to maintain shape and stiffness under all the down from the platform onto the lower hull or footing. anticipated loading. The size of objects and the potential area where objects may fall down has to be determined under special 3.2 Where columns, lower hulls or footings are consideration of crane operations. From there the designed with stiffened plating, framing, girders, etc., following angles of fall direction may be assumed: may be determined in accordance with the requirements for tanks. Where an internal space is a void − in air, unit floating: 10° compartment, the design head used is not to be less − in air, unit supported on seabed: 5° than that corresponding to the maximum allowable waterline of the unit in service. In general, the scant- − in water: 15 ° Chapter 2 Section 3 C Column Stabilized Units IV - Part 6 Page 3–4 GL 2007

The endangered main structural elements of the lower and roundness of shape. The necessary buckling in- hull determined in this way have to be reinforced to vestigation has to consider axial stresses and stresses withstand the impact energy of fallen objects. caused by hydrostatic pressure, where applicable, see Chapter 4, Section 3, G.4. 3.9 When a unit is designed for operations while supported by the seabed, the footings shall be de- 4.5 Where braces are designed to be buoyant, signed to withstand the shock of bottom contact due to they shall be designed to prevent collapse from hydro- wave action on the hull. Such units shall also be static pressure. They shall be accessible for internal evaluated for the effects of possible scouring action inspection, or else adequate means should be provided (loss of bottom support). The effect of skirt plates, in order to detect leakage at an early stage. where provided, shall be given special consideration.

4. Bracing members C. Stability 4.1 Arrangement of braces Where braces are essential for the structural integrity 1. General of the unit, see 1.5, they should be so arranged that The general requirements for stability are defined in they are protected as far as possible against boat im- Section 7. Additional aspects are given in the follow- pact (collisions) and other forces resulting from nor- ing. mal operations.

4.2 Bracing members are to be designed to 2. Stability of units resting on the sea bed transmit loading due to environmental and inertia Units designed to rest on the sea bed are to have suffi- forces acting on the structure. When the unit is sup- cient downward gravity loading on the support foot- ported by the sea bed, the possibility of uneven bear- ings or lower hull to withstand the overturning mo- ing loads shall also be considered. Although designed ment of the combined environmental forces from any primarily as brace members of the overall structure direction, for each applicable design loading condi- under the designated loading, the bracing must also be tion. investigated, if applicable, for superimposed local bending stresses due to buoyancy, wave and current The overturning safety factor, defined as the sum of forces. the restoring moments divided by the sum of the overturning moments, should not be less than: 4.3 Where relevant, consideration is to be given to local stresses due to wave impact. − 1,5 for loading condition 1 − 1,3 for loading condition 2 4.4 When bracing members are of tubular section, ring frames may be required to maintain stiffness according to Chapter 4, Section 3, C. IV - Part 6 Section 4 A Surface Drilling Units Chapter 2 GL 2007 Page 4–1

Section 4

Surface Drilling Units

A. General 2.4 Positional mooring equipment An arrangement drawing for the mooring system has 1. Definition to be submitted. Mooring forces and permissible mooring directions are to be defined. As surface drilling units are to be understood: In the drawings for the hull structure the foundations 1.1 Ship type drilling units for the mooring winches and the fairleads have to be shown. As maximum mooring forces the breaking Ship type drilling units are seagoing ship-shaped units strength of the mooring cables defined in the mooring having a displacement-type hull or hulls, of the single, arrangement has to be assumed. catamaran or trimaran types, which have been designed or converted for drilling operations in the float- Mooring equipment for position keeping at the working condition. Such types have propulsion machinery. ing location is defined in Section 8, C.

The Class Notation DRILLING VESSEL will be 2.5 Dynamic position keeping assigned for this type, compare Chapter 1, Section 2, C.2.3. Dynamic position keeping at the drilling location means maintaining a desired position within the nor- 1.2 Barge type drilling units mal excursions of the control system and under defined environmental conditions. The required position Barge type drilling units are seagoing units having a tolerances during drilling operations have to be de- displacement type hull or hulls, which have been defined by the Owner/Operator. signed or converted for drilling operations in the floating condition. These units have no propulsion machin- The complete dynamic positioning system requires the ery. following sub-systems: The Class Notations PONTOON EQUIPPED FOR − power system DRILLING will be assigned for this type, compare Chapter 1, Section 2, C.2.3 and C.2.9. − thruster system − control system 1.3 Other types of surface drilling units Thrusters used as sole means of position keeping shall Units which are designed as mobile offshore drilling provide a level of safety equivalent to that provided units and which do not fall into the categories accord- for mooring arrangements to the satisfaction of GL. ing to 1.1 and 1.2 will be treated on an individual basis and be assigned an appropriate Classification designa- The Class Notations DP 1 to DP 3 will be assigned if tion. the unit is equipped with such a system, compare Chapter 1, Section 2, C.2.7. 2. Scope Further details are defined in the GL Rules I – Ship Technology, Part 1 – Seagoing Ships, Chapter 15 – 2.1 This Section covers those specific design Dynamic Positioning Systems. criteria and features of surface drilling units which are not dealt with in other Sections, as referred to in the 2.6 Lifting appliances following. Drawings showing the location and support of foundations for cranes and davits have to be submitted. The 2.2 Subdivision and watertight integrity forces to the hull structure have to be defined. Subdivision and watertight integrity of surface drilling For the interaction of lifting appliances with the unit, units are dealt with in Section 7. Regarding stability their foundations, etc. see Chapter 4, Section 8. see C. The requirements for offshore cranes and other lifting 2.3 Machinery and electrical installations appliances themselves are defined in the GL Rules VI – Additional Rules and Guidelines, Part 2 – Life Sav- Machinery and electrical installations shall be de- ing Appliances, Lifting Appliances, Accesses, Chapter signed according to Chapter 5 and 6 respectively, as 2 – Guidelines for the Construction and Survey of applicable. Lifting Appliances. Chapter 2 Section 4 D Surface Drilling Units IV - Part 6 Page 4–2 GL 2007

2.7 Towing 3.3 The local structure in way of elements of the position mooring system and of the towing system, if If the unit is towed by tugs, a general arrangement applicable, has to be reinforced accordingly, compare drawing of the towing system has to be submitted. A.2.4 and A.2.7. Towing forces and permissible towing directions are to be defined. In the drawings of the hull structure the measures to transfer the towing forces into the hull have to be C. Stability shown. As maximum towing forces the breaking strength of the towing ropes or cables defined in the Stability according to the requirements defined in towing arrangement has to be assumed. Section 7 has to be investigated for the three occurring modes of operation: Conditions for towing shall be clearly indicated in the Operating Manual, compare Section 1, C.3.1. − drilling operation under defined environmental conditions

− severe storm conditions B. Structure − transit conditions between different drilling locations 1. General Scantlings of the hull structure are to meet the GL Rules I – Ship Technology, Part 1 – Seagoing Ships, D. Drilling Facilities Chapter 1 – Hull Structures. For barge types according to A.1.2 especially Section 31 – Barges and Pontoons has to be observed. 1. Scope Special consideration however is to be given to items These Rules do not include requirements for the drill- which may require some deviation or additions to ing of subsea wells or procedures for their control. these Rules, in particular the items indicated in 2. - 5. Such drilling operations are subject to control by the coastal state. 2. Drilling well 2. Drawings to be submitted 2.1 The required strength of the unit shall be The planned interaction of the drilling systems with maintained in way of the drilling well and particular hull has to be clearly documented, e.g. by: attention shall be given to the transition between fore- and-aft members so as to maintain continuity of the − drawings showing the arrangement of the drilling longitudinal material. Stress concentrations have to derrick including weights and moments avoided by a favourable structural detailed design. In addition, the plating of the well is to be suitably stiff- − drawings showing the pipe storage and handling ened to prevent damage due to foreign objects which may become trapped in the well when the unit is in − drawings showing mud tanks, cement silos, etc. transit. 3. Operating manual 2.2 The drilling well is to be surrounded by cof- The rated capacity for each reeving shall be included ferdams. Such cofferdams may temporarily be used also as tanks for liquids related to drilling operations, in the Operating Manual. if they can be easily emptied for inspection. 4. Drilling equipment 3. Deck area 4.1 Drilling derricks shall be designed according to recognized codes/standards and/or applicable Na- 3.1 The deck area in way of large hatches is to be tional Regulations. suitably compensated where necessary to maintain the strength of the unit. Permanently installed piping systems for drilling operations are to comply with a recognised standard or 3.2 The structure in way of heavy concentrated code. loads resulting from the drilling derrick, pipe rack, set back, drilling mud storage, etc., is to be suitably rein- 4.2 Requirements for drilling systems are con- forced. tained in Chapter 5, Section 11. IV - Part 6 Section 4 E Surface Drilling Units Chapter 2 GL 2007 Page 4–3

E. Safety Aspects 2. Fire protection The requirements for structural fire protection and means of escape are defined in Chapter 5, Section 10, B. 1. Hazardous areas

3. Fire detection and extinguishing The general classification in hazardous and non- The requirements for fire detection and alarm systems hazardous areas is contained in Chapter 5, Section 2, are defined in Chapter 5, Section 10, J. The require- whereas the area classification requirements to be ments for fire extinguishing systems and equipment observed for drilling are defined in Chapter 5, Section are summarized in Chapter 5, Section 10, C. – I. 11, B.2. 4. Life-saving appliances The requirements for explosion protection of electrical The number, size and arrangement of life-saving ap- equipment in hazardous areas are defined in Chapter pliances for the complete crew shall follow the re- 6, Section 13. quirements defined in Section 9 of this Chapter.

IV - Part 6 Section 5 B Pipelaying Units Chapter 2 GL 2007 Page 5–1

Section 5

Pipelaying Units

A. General 2.3.2 If the lifting appliances shall be included into the Certification or Classification by GL, the requirements for offshore cranes and other lifting appliances 1. Definition are defined in the GL Rules VI – Additional Rules and As pipelaying vessels are to be understood: Guidelines, Part 2 – Life Saving Appliances, Lifting Appliances, Accesses, Chapter 2 – Guidelines for the 1.1 Pipelaying vessels Construction and Survey of Lifting Appliances. Pipelaying vessels are seagoing ship-shaped units 3. Safety aspects having a displacement-type hull or hulls, of the single or catamaran types, which have been designed or converted for pipe laying. Such types have propulsion 3.1 Hazardous areas machinery and a dynamic positioning system or positional mooring equipment. The general classification in hazardous and non- hazardous areas is contained in Chapter 5, Section 2. The Class Notation PIPE-LAYING VESSEL will be assigned for this type, compare Chapter 1, Section 2, The requirements for explosion protection of electrical C.2.3. equipment in hazardous areas are defined in Chapter 6, Section 13. 1.2 Pipelaying barges 3.2 Fire protection Pipelaying barges are seagoing units having a displacement type hull or a semi-submersible configura- The requirements for structural fire protection and tion, which have been designed or converted for pipe means of escape are defined in Chapter 5, Section 10, laying. These units have no propulsion machinery, but B. may have positional mooring equipment, adequate tug assistance or dynamic positioning. 3.3 Fire detection and extinguishing The Class Notations PONTOON EQUIPPED FOR The requirements for fire detection and alarm systems PIPELAYING will be assigned for this type, com- are defined in Chapter 5, Section 10, J. The require- pare Chapter 1, Section 2, C.2.3 and C.2.9. ments for fire extinguishing systems and equipment are summarized in Chapter 5, Section 10, C. – I. 2. Scope 3.4 Life-saving appliances 2.1 This Section covers those specific design The number, size and arrangement of life-saving ap- criteria and features of pipelaying units which are not pliances for the complete crew shall follow the re- dealt with in other Sections, as referred to in the fol- quirements defined in Section 9 of this Chapter. lowing.

2.2 Machinery and electrical installations Machinery and electrical installations shall be de- B. Movement and Position Keeping signed according to Chapter 5 and 6 respectively, as applicable. 1. Possibilities 2.3 Lifting appliances For the movement and position keeping of the unit during pipelaying the following possibilities may be 2.3.1 Drawings showing the location and support established: of foundations for cranes and davits have to be submitted. The forces to the hull structure have to be − positional mooring with cables and anchors defined. − dynamic positioning by a greater number of Rules for the interaction of lifting appliances with the thrusters on the unit unit, their foundations, etc. are defined in Chapter 4, Section 8. − combination of mooring and dynamic positioning Chapter 2 Section 5 B Pipelaying Units IV - Part 6 Page 5–2 GL 2007

2. Dynamic analysis of the pipelaying system 4. Dynamic position keeping

A dynamic analysis has to be submitted to GL, which 4.1 Dynamic position keeping at the pipelaying has to consider: route means maintaining a desired position within the normal allowance of the control system and under − arrangement of positional mooring system consid- defined environmental conditions. The required posi- ering elasticity of cables, if applicable tion tolerances during pipelaying operations have to be − function of dynamic positioning system, if appli- defined by the Owner/Operator. cable Thrusters used as sole means of position keeping shall provide a level of safety equivalent to that provided − influence of the laid pipe and forces at the tension- for mooring arrangements to the satisfaction of GL. ers − influence of seastate, wind and current conditions, 4.2 The complete dynamic positioning system see Chapter 4, Section 1 requires the following sub-systems: − power system 3. Positional mooring equipment − thruster system

3.1 If the Class Notation “EQUIPPED WITH − control system POSITION MOORING SYSTEM” will be assigned, such a system consisting of: 4.3 The Class Notations DP 1 to DP 3 will be assigned if the systems complies with the require- − heavy anchors belonging to the unit and regularly ments of the GL Rules I – Ship Technology, Part 1 – changed in position by anchor handling tugs Seagoing Ships, Chapter 15 – Dynamic Positioning Systems, see also Chapter 1, Section 2, C.2.7. − safe stowage of the anchors on the unit and appliances to hand them over to the tugs 5. Combination of positional mooring sys- − anchor cables as wire ropes or chain cables from tems with dynamic positioning the anchors to fairleads and winches on the unit including accessories like shackles, quick release 5.1 Also a combination of the positional mooring devices, wire rope terminations, etc. system according to 3. with a dynamic positioning system according to 4. may be established, if it is of − a winch or windlass for each anchor cable includ- advantage for a special task. ing tension control and measuring of cable length paid out 5.2 It must be secured that all elements of the combined system are operated from one control sta- − central control of all winches to keep position and tion overlooking the unit and the mooring area. allow forward movement of the unit on the planned track 5.3 The detailed requirements for such a combi- has to be provided, see also Chapter 1, Section 2, nation will be defined case by case. C.2.9. 6. Towing 3.2 An arrangement drawing for the mooring system has to be submitted. Mooring forces and per- 6.1 If the unit is towed by tugs, a general ar- missible mooring directions are to be defined. An rangement drawing of the towing system has to be example for a mooring system with 10 anchors is submitted. Towing forces and permissible towing shown in Fig. 5.1 and Fig. 5.2 for the two phases of directions are to be defined. starting of the operation and after a travel of abt. 600 m. 6.2 Towing arrangements and procedures shall be such as to reduce to a minimum any danger to person- 3.3 In the drawings for the hull structure the nel during towing operations. The design and ar- foundations for the mooring winches and the fairleads rangement of towing fittings shall have regard to both have to be shown. The acting forces on the founda- normal and emergency conditions. tions are to be calculated for 100 % of the nominal breaking load of the mooring cables. For the support- 6.3 In the drawings of the hull structure the ing structure under this equipment 100 % of the mini- measures to transfer the towing forces into the hull have to be shown. As towing forces 100 % of the mum yield stress ReH is to be observed as acceptance criterion in the calculation. nominal breaking load of the towing lines have to be considered. For the supporting structure under this 3.4 The mooring equipment for position keeping equipment 100 % of the minimum yield stress ReH is on the pipeline track is defined in Section 8, C. to observed as acceptance criterion in the calculation. IV - Part 6 Section 5 B Pipelaying Units Chapter 2 GL 2007 Page 5–3

Direction of travel

2 3 0 1 0 4

0 0 Bow anchors

1500 m 1500 m

6 0 5 0

Phase 1 1000 m 1000 m Breast anchors (Start of

movement) 0 7 0 80° 30 - 40° 8 800 m 800 m

500 m 800 m 0 10 0 Stern anchors 9

Fig. 5.1 Example for a typical position mooring system in abt. 100 m water depth (starting phase)

Direction of travel

1 4

0 0

900 m 900 m

Phase 2 0

70 - 80° 0 (Change of 5 6 mooring 700 m points after 600 m travel) 1000 m 1000 m

600 m 1100 m 7 8

1400 m

0 10

Fig. 5.2 Example for a typical position mooring system in abt. 100 m water depth (after 600 m travel) Chapter 2 Section 5 D Pipelaying Units IV - Part 6 Page 5–4 GL 2007

7. Operating manual 3. Special aspects for the hull structure For the positioning and towing systems the following The following requirements, which are characteristic aspects have to be included in the Operating Manual, for pipelaying, have to be considered for the design of compare Section 1, C.3.1: the hull structure, e.g.:

− principal functioning and co-operation of the dif- − slot in the rear part of the main deck to lead the ferent elements of the system pipe with the necessary bending radius to the stinger − procedure for the start of pipelaying − transmission of the forces from the stinger to the − procedure for normal pipelaying operation with stern of the unit and of the forces from the A- advancing unit frame for holding the stinger back and adjusting the inclination of it to the main deck − stopping or finishing the pipelaying operation with − transmission of the pipeline forces pulling the disconnecting and abandoning of the pipeline (two) tensioners horizontally to the stern into the − towing conditions midship section of the hull − considerable mooring forces from different direc- procedures in the event of failure of the systems − tions at stern and bow − emergency measures − various loads from the pipelaying facility as described in E. 8. Sea trials

8.1 A schedule for the proposed tests of the positioning and towing systems has to be submitted for D. Watertight Integrity and Stability approval to GL Head Office in due time before the sea trials. 1. Watertight integrity For subdivision into watertight compartments see 8.2 All procedures defined in the Operating Section 7, E. Manual have to be tested as far as practicable in this stadium. 2. Stability 8.3 The trials have to be executed in presence of a GL Surveyor who will sign a detailed trials protocol 2.1 Load cases to be prepared by the builder, if the tests are success- The following load cases have to be considered: ful. The duplicate of this protocol has to be sent to GL Head Office for final approval. 2.1.1 Standard load cases − normal pipelaying operation up to defined environmental limit conditions C. Structure − severe storm and seaway conditions with pipe disconnected and abandoned at the seabed 1. General design 2.1.2 Special load cases Scantlings of the hull structure are to meet the GL − ocean towage for long distances without or with Rules I – Ship Technology, Part 1 – Seagoing Ships, stinger, if applicable Chapter 1 – Hull Structures. For barge types according to A.1.2 especially Section 31 – Barges and Pontoons − field towage for short distances with stinger has to be observed. − inspection or repair of existing pipelines by lifting Special consideration however is to be given to items up a part of the pipeline from the seabed to the which may require some deviation or additions to units side these Rules, in particular the items defined in the following. − influences from crane operation and positional mooring have to be considered

2. Loads 2.1.3 Other load cases The loads established in the dynamic analysis of the Depending on the type of pipelaying unit and the pipelaying system according to B.2. have to be con- method of operation other load cases may be consid- sidered. ered case by case. IV - Part 6 Section 5 E Pipelaying Units Chapter 2 GL 2007 Page 5–5

2.2 Stability criteria − general arrangement of the pipelaying facility and description of the main functions, definition of the 2.2.1 Intact stability environmental conditions up to which the facility Concerning stability criteria the Code of Intact Stabil- is able to operate ity for All Types of Ships Covered by IMO Instru- ments Resolution A.749(18) as amended by resolution − facilities for lifting the pipes from the supply ves- MSC 75(69) shall be applied 1. sels to the storage area and pipe transport on the unit defining all created moments and forces Special considerations shall be given to an unusual arrangement of units, which also may lead to addi- − plans showing the arrangement of the pipe stor- tional stability criteria. age/racks, the maximum weights and the intended foundations on the upper deck 2.2.2 Damage stability − plans defining the foundation forces of the facility The criteria of the Code of Safety for Special Purpose for pipe connections Ships acc. to IMO Res.A.543(13) and of the Code for the Construction and Equipment of Mobile Offshore − plans showing the arrangement of the pipe ten- Drilling Units (MODU Code) shall be used as far as sioners and the maximum tension forces applicable. − plans showing the support arrangement on the pipe ramp and the maximum forces to be experienced

E. Pipelaying Facility − plans showing the integration of the stinger at the stern of the hull and definition of the forces to be transferred into the hull, if applicable 1. Scope In general the facility directly used for pipe storage, − plans showing the stinger including length varia- fabrication of the pipe connections, pipe fixing and tion , if applicable and its floating support, if ap- delivering/recovering to/from the sea bed are not sub- plicable ject to Classification or Certification by GL. But the characteristics of the facilities, which influence: − plans showing the A-frame for variation of the stinger inclination, if applicable − overall design of the unit − GL reserve the right to ask for any other documen- − overall safety of the unit tation necessary to define the interaction of the fa- − weights and forces on all foundations cility with the unit − floating and stability behaviour, etc. 3. Operating Manual will be considered by GL. Therefore GL has to be fully informed by the documents defined in 2. The Operating Manual of the unit, compare Section 1, C.3.1, shall include all safety aspects created by the facility and has also to be submitted to GL. This man- 2. Documents to be submitted ual shall include e.g.: A complete set of documentation to define the influences on the unit has to be submitted by the − functions of the pipelaying facility including repair builder/Operator of the facility, consisting of e.g.: of existing pipelines, if applicable − influence of pipelaying on unit operation –––––––––––––– − special hazards to the unit 1 In addition the criteria of the Code of Safety for Special Pur- pose Ships acc. to IMO Res.A.543(13) and of the Code for the Construction and Equipment of Mobile Offshore Drilling − emergency measures if a failure happens in the Units (MODU Code) shall be used as far as applicable. pipelaying facility, etc.

IV - Part 6 Section 6 D Well Stimulation Units Chapter 2 GL 2007 Page 6–1

Section 6

Well Stimulation Units

A. General 3. Emergency shut down

For all vessels/units an emergency shut down and 1. Definition quick well disengagement concept has to be developed distinguishing different shutdown levels according to Well stimulation vessels or units are self-propelled the used procedures of well stimulation. The require- ship-type vessels equipped for intervention at subsea ments for relevant safety systems are defined in wells with the aim to improve the operational well Chapter 5 – Machinery Installations, Section 17. performance. 4. Evacuation The Class Notations WELL STIMULATION VESSEL or WELL STIMULATION UNIT will be If the stimulation procedures fail and the crew will be assigned for this type, compare Chapter 1, Section 2, in extreme danger the equipment for a quick and C.2.3. smooth evacuation shall be available. The requirements for such equipment are defined in Section 9. 2. Stimulation service 5. Documentation The service of well stimulation vessels/units may be distinguished in: All safety aspects have to be clearly defined in written form, such as a Safety Management Plan, and shall be − stimulation of subsea wells using various operat- included in the Operating Manual of the vessel/unit, ing procedures compare Section 1, C.3.1.

− stimulation of subsea wells including handling and storage of well fluids C. Position Keeping 3. Scope 1. As the well stimulation vessel/unit has to stay In this Section the overall and special aspects for this near or above the well within a very restricted location type of vessel/unit are summarized and references are allowance, the position keeping will be a major pre- given to the different Chapters and Sections of the requisite. Rules where the detailed requirements are defined. 2. Position keeping may be established by the following methods:

− positional mooring with anchors, cables and moor- B. Special Safety Aspects ing winches according to Section 8 and Chapter 5 – Machinery Installations, Section 8, C. 1. Area classification − dynamic positioning with propulsion systems For all types of vessels/units hazardous and non- according to Chapter 5 – Machinery Installations, hazardous areas have to be investigated and a com- Section 6, E. For this type of vessel/unit the re- plete area classification has to be performed, as far as quirements for Class Notation DP 2 are recom- needed. For the relevant criteria of such a classifica- mended. tion see Chapter 5 – Machinery Installations, Section 2.

2. Fire protection D. Well Stimulation Equipment

Special attention shall be given to fire protection and 1. The foundations for such equipment have to measures for fire fighting. Relevant methods are be integrated into the structure of the vessel/unit con- summarized in Chapter 5 – Machinery Installations, sidering extreme loads likely to occur during the Section 10. stimulation process. Chapter 2 Section 6 D Well Stimulation Units IV - Part 6 Page 6–2 GL 2007

2. Well stimulation equipment is in general not 3. Especially equipment to be installed in haz- subject to Classification by GL. Nevertheless this ardous areas shall meet the necessary safety standards. equipment shall be designed and built according to For electrical installations reference may given to recognized regulations and safety standards. Chapter 6 – Electrical Installations, Section 13. IV - Part 6 Section 7 B Subdivision, Stability and Load Line Chapter 2 GL 2007 Page 7–1

Section 7

Subdivision, Stability and Load Line

A. General Remarks, Scope 2 F0,5CC=⋅⋅⋅ρ⋅⋅SH vAN[]

1. This Section refers to the subdivision, stabil- F = wind force [N] ity and load line requirements for mobile offshore units and covers, essentially, the relevant regulations CS = shape coefficient depending on the shape of of the IMO "Code for the Construction and Equipment the structural member exposed to the wind, of Mobile Offshore Drilling Units (MODU Code)", as see Table 7.1 [–] amended. CH = height coefficient depending on the height 2. Any additional National Regulations should above sea level of the structural member ex- be observed, where applicable. posed to wind, see Table 7.2 [–]

4 3. Regarding the effects of (maximum) angles ρ = air mass density (1,25) [Ns²/m ] of inclination on machinery installations see Chapter v = wind velocity [m/s] 5, Section 1, C. and Chapter 6, Section 1, E. A = projected area of all exposed surfaces in either the upright or the heeled condition [m²]. B. Righting and Heeling Lever Curves 4. Wind forces shall be considered from any 1. Curves of righting levers and of wind heeling direction relative to the limit and the value of the wind levers similar to Figure 7.1 with supporting calcula- velocity shall be as follows: tions shall be prepared covering the full range of operating draughts including those in transit conditions, 4.1 In general a minimum wind velocity of 36 taking into account the maximum deck cargo and m/s (70 knots) for offshore service shall be used for equipment in the most unfavourable position applica- normal operating conditions and a minimum wind ble. The righting lever curves and wind heeling lever velocity of 51,5 m/s (100 knots) shall be used for the curves shall be related to the most critical axes. Ac- severe storm conditions. Loading conditions 2 and 3, count shall be taken of the free surface of liquids in respectively see Chapter 4, Section 3, C. tanks. Righting lever Table 7.1 Values of the coefficient CS

Downflooding Heeling Shape CS lever angle Spherical 0,4 Second intercept Cylindrical 0,5 Lever Large flat surface (hull, deckhouse, 1,0 smooth under deck areas)

Angle of inclination Drilling derrick 1,25

Wires 1,2 Fig. 7.1 Righting and heeling lever curves Exposed beams and girders under 1,3 2. Where equipment is of such a nature that it deck can be lowered and stowed, additional wind heeling Small parts 1,4 lever curves may be required; such data shall clearly indicate the position of such equipment. Isolated shapes (cranes, beams, etc.) 1,5 Clustered deckhouses or similar 3. The curves of wind heeling levers shall be 1,1 drawn for wind forces calculated by the following structures formula: Chapter 2 Section 7 C Subdivision, Stability and Load Line IV - Part 6 Page 7–2 GL 2007

Table 7.2 Values of coefficient CH 7. Wind heeling moments derived from wind tunnel tests on a representative model of the unit may be considered as alternatives to the method given in 3. C 1 Height above sea level [m] H to 5. Such heeling moment determination shall include 0 – 15,3 1,00 lift and drag effects at various applicable heel angles. 15,3 – 30,5 1,10 30,5 – 46,0 1,20 C. Intact Stability Criteria 46,0 – 61,0 1,30 61,0 – 76,0 1,37

76,0 – 91,5 1,43 1. Standard criteria 91,5 – 106,5 1,48 1.1 The stability of a unit in each mode of opera- 106,5 – 122,0 1,52 tion shall meet the following criteria, see also Fig. 7.1. 122,0 – 137,0 1,56 1.2 For surface (ship-like) and self-elevating 137,0 – 152,5 1,60 units the area under the righting lever curve to the 152,5 – 167,5 1,63 second intercept or downflooding angle, whichever is less, shall be not less than 40 % in excess of the area 167,5 – 183,0 1,67 under the wind heeling lever curve to the same limiting angle. 183,0 – 198,0 1,70 198,0 – 213,5 1,72 1.3 For column stabilized units the area under the righting lever curve to the angle of downflooding shall 213,5 – 228,5 1,75 be not less than 30 % in excess of the area under the 228,5 – 244,0 1,77 wind heeling lever curve to the same limiting angle. 244,0 – 256,0 1,79 1.4 The righting lever curve shall be positive Above 256 1,80 over the entire range of angles from upright to the second intercept. 1 The higher value of CH has to be used.

2. Severe storm condition 4.2 Where a unit is to be limited in operation to Each unit shall be capable of sustaining a severe storm sheltered locations (protected inland waters such as condition in a period of time consistent with meteoro- lakes, bays, swamps, rivers, etc.) consideration may be logical conditions. The procedures recommended and given to a reduced wind velocity of not less than 25,8 the approximate length of time required, considering m/s (50 knots) for normal operating conditions. both operating conditions and transit conditions, shall be contained in the Operating Manual. It shall be pos- 4.3 In calculating the projected areas to the verti- sible to achieve the severe storm condition without the cal plane the area of surfaces exposed to wind due to removal or relocating of solid consumables or other heel or trim, such as deck undersides, etc., shall be variable loads. However, on application and with included using the appropriate shape factor. Open agreement of GL, loading a unit past the point at truss work may be approximated by taking 30 % of which solid consumables would have to be removed the projected block area of both the front and back or relocated to go to severe storm condition may be section, i.e. 60 % of the projected area of one side. permitted under the following conditions, provided the allowable KG requirement is not exceeded: 5. In calculating the wind heeling moments the − in a geographic location where weather conditions lever of the wind overturning force shall be taken annually or seasonally do not become sufficiently vertically from the centre of pressure of all surfaces severe to require a unit to go to severe storm con- exposed to the wind to the centre of lateral resistance dition, or of the underwater body of the unit. The unit shall be assumed floating free of mooring restraint. − where a unit is required to support extra deck-load for a short period of time that is well within the bounds of a favourable weather forecast 6. The wind heeling levers shall be calculated for a sufficient number of heel angles to define the − geographic locations, weather conditions and load- curve. For ship shaped hulls the curve may be as- ing conditions when this is permitted shall be iden- sumed to vary as the cosine function of unit heel. tified in the Operating Manual. IV - Part 6 Section 7 E Subdivision, Stability and Load Line Chapter 2 GL 2007 Page 7–3

3. Alternative stability criteria 4. A record of all changes to machinery, structure, outfit and equipment that affect the light ship Alternative stability criteria may be accepted provided data, shall be maintained in the Operating Manual, or an equivalent level of safety is maintained, and if they a light ship data alterations log, and be taken into are demonstrated to afford adequate positive initial account in daily operations. stability. The acceptability of such criteria will be determined considering at least the following and taking into account, as appropriate: 5. For column stabilized units, a deadweight survey shall be conducted at intervals not exceeding − Environmental conditions representing realistic five years. Where the deadweight survey indicates a winds (including gusts) and waves appropriate for change from the calculated light ship displacement in world wide service in various modes of operation. excess of 1 % of the operating displacement, an inclining test shall be conducted. − Investigate dynamic response of the unit. The analysis shall include the results of wind tunnel tests, wave tank model tests, and non-linear simu- 6. The inclining test or deadweight survey shall lation, where appropriate. Any wind and wave be carried out in the presence of a GL Surveyor. spectra used shall cover sufficient frequency ranges to ensure that critical motion responses are identified. − Potential for flooding taking into account dynamic E. Subdivision and Damage Stability responses in a seaway. 1. Surface and self-elevating units − Susceptibility to capsizing considering the unit’s restoration energy and the static inclination due to the mean wind speed and the maximum dynamic 1.1 The unit shall have sufficient freeboard and response. be subdivided by means of watertight decks and bulkheads to provide sufficient buoyancy and stability to − An adequate safety margin to account for uncer- withstand in general the flooding of any one com- tainties. partment in any operating or transit condition consistent with the damage assumptions set out in F.

1.2 The unit shall have sufficient reserve stability D. Inclining Test in a damaged condition to withstand the wind heeling moment based on a wind velocity of 25,8 m/s (50 knots) imposed from any direction. In this condition 1. An inclining test shall be carried out with the the final waterline, after flooding, shall be below the first unit of a design, when as near to completion as lower edge of any downflooding opening. possible, to determine accurately the light ship data (weight and position of centre of gravity). 2. Column stabilized units 2. For successive units which are identical by design, the light ship data of the first unit of the series 2.1 The unit shall have sufficient freeboard and may be accepted in lieu of an inclining test, provided be subdivided by means of watertight decks and bulk- the difference in light ship displacement or position of heads to provide sufficient buoyancy and stability to centre of gravity due to weight changes and minor withstand a wind heeling moment induced by a wind differences in machinery, outfitting or equipment, of velocity of 25,8 m/s (50 knots) imposed from any confirmed by the results of a deadweight survey, are direction in any operating or transit condition, consid- less than 1 % of the values of the light ship displace- ering: ment and principal horizontal dimensions as deter- − The angle of inclination after the damage set out in mined for the first of the series. F.3. shall not be greater than 17°. Particular care shall be given to the detailed weight calculation and comparison with the original unit of a − Any opening below the final waterline shall be series of column stabilized semi-submersibles as made watertight, and openings within 4 m above these, even though identical by design, are recognized the final waterline shall be made weathertight. as being unlikely to attain an acceptable similarity of − The righting lever curve after damage as set out weight or centre of gravity to warrant a waiver of the above shall have, from the first intercept to the inclining test. lesser of the extent of weathertight integrity required above and the second intercept, a range of 3. The results of the inclining test, or dead- at least 7°. Within this range the righting lever weight survey and inclining experiment adjusted for curve shall reach a value of at least twice the wind weight differences, shall be indicated in the Operating heeling lever curve, both being measured at the Manual. same angle, see Fig. 7.2. Chapter 2 Section 7 F Subdivision, Stability and Load Line IV - Part 6 Page 7–4 GL 2007

Extent of − vertical extent: from the base line upwards without weathertight Righting lever limit integrity Wind 1.2 The distance between effective watertight heeling bulkheads or their nearest stepped portions, which are r lever positioned within the assumed extent of horizontal h penetration, shall be not less than 3 m. Where there is a lesser distance one or more of the adjacent bulk- Angle of heads shall be disregarded. inclination 1.3 Where damage of a lesser extent than given First intercept Second intercept in 1.1 results in a more severe condition, such lesser extent shall be assumed. r ³ 2 h 1.4 All piping, ventilation systems, trunks, etc.,

within the extent of damage referred to in 1.1 shall be Fig. 7.2 Righting and heeling lever curves for assumed to be damaged. Positive means of closure damage stability shall be provided at watertight boundaries to preclude the progressive flooding of other spaces which are 2.2 The unit shall provide sufficient buoyancy intended to be intact. and stability to withstand, in any operating or transit condition, the flooding of any watertight compartment 2. Self-elevating units wholly or partially below the waterline in question, which is a pump room, a room containing machinery 2.1 In assessing the damage stability of self- with a salt water cooling system or a compartment elevating units, the following extent of damage shall adjacent to the sea, considering: be assumed between effective watertight bulkheads: − The angle of inclination after flooding shall not be − horizontal penetration: 1,5 m greater than 25°. − vertical extent: from the base line upwards without − Any opening below the final waterline shall be limit made watertight. Where a bottom mat is fitted, assumed damage pene- − A range of positive stability shall be proven, be- tration simultaneous to both the mat and the upper hull yond the calculated angle of inclination in this need only be considered when the lightest draught condition, of at least 7°. allows any part of the mat to fall within 1,5 m vertically of the waterline, and the difference in horizontal 3. All types of units dimension of the upper hull and mat is less than 1,5 m in any area under consideration. If damage of a lesser 3.1 The requirements of 1.1 and 1.2 shall be extent results in a more severe final equilibrium condi- determined by calculations which take into consideration, such lesser extent shall be assumed. tion the proportions and design characteristics of the unit and the arrangements and configuration of the 2.2 The distance between effective watertight damaged compartments. In making these calculations, bulkheads or their nearest stepped portions, which are it shall be assumed that the unit is in the worst antici- positioned within the assumed extent of horizontal pated service condition as regards stability and is penetration, shall be not less than 3 m. Where there is floating free of mooring restraints. a lesser distance one or more of the adjacent bulkheads shall be disregarded. 3.2 The ability to reduce heeling angles by pumping out or ballasting compartments, or by application 2.3 Where damage of a lesser extent than given of mooring forces etc., shall not be considered as alle- in 2.1 results in a more severe condition, such lesser viating the requirements. extent shall be assumed.

2.4 All piping, ventilation, systems, trunks, etc. F. Extent of Damage within the extent of damage referred to in 2.1 shall be assumed to be damaged. 1. Surface units 2.5 Positive means of closure shall be provided at 1.1 In assessing the damage stability of surface watertight boundaries to preclude the progressive units, the following extent of damage shall be assumed flooding of other spaces which are intended to be between effective watertight bulkheads: intact. In addition, the compartments adjacent to the bottom shell are also to be considered flooded indi- − horizontal penetration: 1,5 m vidually. IV - Part 6 Section 7 G Subdivision, Stability and Load Line Chapter 2 GL 2007 Page 7–5

2.6 The recessed ends and sides of the drilling G. Watertight Integrity slot need not be subject to horizontal penetration if warning signs be posted on each side of the vessel 1. Openings and penetrations stating that no boats be allowed inside the drilling slot. Instructions to this effect should be included in the The number of openings in watertight subdivisions Operating Manual. shall be kept to a minimum compatible with the design and proper working of the unit. Where penetrations of watertight decks and bulkheads are necessary for ac- 3. Column stabilized units cess, piping, ventilation, electrical cables, etc., arrangements shall be made to maintain the watertight 3.1 In assessing the damage stability of column integrity of the enclosed compartments. stabilized units, the following extent of damage shall be assumed. 2. Valves 3.2 Only those columns, underwater hulls and 2.1 Where valves are provided at watertight braces on the periphery of the unit shall be assumed to boundaries to maintain watertight integrity, these be damaged, and the damage shall be assumed in the valves shall be capable of being operated from a exposed portions of the columns, underwater hulls and pump-room or other normally manned space, a braces. weather deck, or a deck which is above the final waterline after flooding. In the case of a column stabi- 3.3 Columns and braces shall be assumed to be lized unit this will be the central ballast control sta- flooded by damage having a vertical extent of 3 m tion. Valve position indicators shall be provided at the occurring at any level between 5 m above and 3 m remote control station. below the draughts specified in the Operating Manual. Where a watertight flat is located within this region, 2.2 For self-elevating units the ventilation system the damage should be assumed to have occurred in valves required to maintain watertight integrity shall both compartments above and below the watertight be kept closed when the unit is afloat. Necessary ven- flat in question. Lesser distances above or below the tilation in this case shall be arranged by alternative draughts may be applied to the satisfaction of GL, approved methods. taking into account the actual operating conditions. However, the extent of required damage region should be at least 1,5 m above and below the draughts speci- 3. Internal openings fied in the Operating Manual. 3.1 The means to ensure the watertight integrity 3.4 No vertical bulkhead shall be assumed to be of internal openings shall comply with the following damaged, except where bulkheads are spaced closer requirements: than a distance of one eighth of the column’s perime- − Doors and hatch covers which are used during the ter at the draught under consideration, measured at the operation of the unit while afloat shall be remotely periphery, in which case one or more of the bulkheads controlled from the central ballast control station shall be disregarded. and shall also be operable locally from each side. Open/shut indicators shall be provided at the con- 3.5 Horizontal penetration of damage shall be trol station. assumed to be 1,5 m. − Doors or hatch covers which are normally closed while the unit is afloat are to be provided with an 3.6 Underwater hulls or footings shall be as- alarm system (e.g. light signals) showing person- sumed to be damaged while the unit is operating in a nel both locally and at the central ballast control transit condition, in the same manner as indicated in station whether the doors or hatch covers in ques- 3.2, 3.3, 3.5 and having regard to their shape, either tion are open or closed. A notice shall be affixed to 3.4 or between effective watertight bulkheads. each such door or hatch cover to the effect that it is not to be left open while the unit is afloat. 3.7 If damage of a lesser extent results in a more severe damage equilibrium condition, such a lesser 3.2 The means to ensure the watertight integrity extent shall be assumed. internal openings which are kept permanently closed during the operation of the unit, while afloat, shall 3.8 All piping, ventilation systems, trunks, etc., comply with the following requirements: within the extent of damage shall be assumed to be damaged. − A notice shall be affixed to each such closing appliance to the effect that it is to be kept closed while the unit is afloat, except that manholes fitted 3.9 Positive means of closure shall be provided at with close bolted covers need not be so marked. watertight boundaries to preclude the progressive flooding of other spaces which are intended to be − On self-elevating units, an entry shall be made in intact. the official log book or tour report, as applicable, Chapter 2 Section 7 H Subdivision, Stability and Load Line IV - Part 6 Page 7–6 GL 2007

to the effect that all such openings have been wit- 1.7 Special consideration shall be given to small nessed closed before the unit becomes waterborne. hatches with an opening area of 2,5 m² or less at the exposed deck over the forward 0,25 L on seagoing 4. External openings units of length 80 m or more, that are contracted on or after 1st January 2004, where the height of the exposed deck in way of the hatch is less than 0,1 L or 22 m 4.1 All downflooding openings, the lower edge above the summer load waterline, whichever is the of which are submerged when the unit is inclined to lesser. For design details see GL Rules I – Ship Tech- the first intercept between the righting lever and wind nology, 1 – Seagoing Ships, Chapter 1 – Hull Struc- heeling lever curves in any intact or damaged condi- tures, Section 17, D.2. tion, shall be fitted with a suitable watertight closing appliance, such as closely spaced bolted covers. 1.8 Special consideration shall be given to air 4.2 Where flooding of chain lockers or other pipes, ventilator pipes and their closing devices at the buoyant volumes may occur, the openings to these exposed deck over the forward 0,25 L on seagoing spaces shall be considered as downflooding points for units of length 80 m or more, that are contracted on or calculating intact stability. st after 1 January 2004, where the height of the exposed deck in way of the pipes is less than 0,1 L or 22 m above the summer load waterline, whichever is the lesser. For design details see GL Rules I – Ship Tech- H. Load Line nology, 1 – Seagoing Ships, Chapter 1 – Hull Struc- tures, Section 21, E.5. 1. General requirements

1.1 The requirements of the 1966 Load Line 2. Surface units Convention, as amended shall in principle apply to all units. The minimum freeboard of units which cannot be computed by the normal methods laid down by that 2.1 Load lines shall be assigned to surface units Convention shall be determined on the basis of meet- as calculated under the terms of the 1966 Load Line ing the applicable intact stability, damage stability and Convention and shall be subject to all the conditions structural requirements for transit conditions and drill- of assignment of that Convention. ing operations while afloat. The freeboard shall not be less than that computed from the Convention where applicable. 2.2 Where it is necessary to assign a greater than minimum freeboard to meet intact or damage stability 1.2 The requirements of the 1966 Load Line requirements, or due to any other restriction, seasonal Convention with respect to weather tightness and marks above the centre of the ring shall not be water tightness of decks, superstructures, deckhouses, marked, and any seasonal marks below the centre of doors, hatchway covers, other openings, ventilators, the ring shall be marked. air pipes, scuppers, inlets and discharges, etc., shall be taken as a basis for all units in the afloat condition. 2.3 Where moonpools are arranged within the 1.3 In general, heights of hatch and ventilator hull in open communication with the sea, the volume coamings , air pipes, door sills, etc., in exposed posi- of the moonpool shall not be included in calculation of tions and their means of closing shall be determined any hydrostatic properties. An addition shall be made by consideration of both intact and damage stability to the geometric freeboard, if the moonpool has a requirements. larger cross-sectional area above the water line at 0,85 H than below, corresponding to the lost buoyancy (H 1.4 All downflooding openings which may be- = depth). This addition for the excess portion above come submerged, before the angle of inclination at 0,85 H shall be made as prescribed for well/recesses which the required area under the intact righting arm below. If an enclosed superstructure contains part of curve is achieved, shall be fitted with weathertight the moonpool, deduction shall be made for the effec- closing appliances. tive length of the superstructure.

1.5 With regard to damage stability, the require- Where open wells/recesses are arranged in the free- nd ments in E.2.1 (2 item), E.2.2 and G.4.1 shall apply. board deck, a correction equal to the volume of the well/recess up to the freeboard deck divided by the 1.6 Special consideration shall be given to the waterplane area at 0,85 H shall be made to the free- position of openings which cannot be closed in emer- board obtained after all other corrections except bow gencies, such as air intakes for emergency generators, height correction have been made. Free surface effects having regard to the intact righting arm curves and the of the flooded well/recess shall be taken into account final waterline after assumed damage. in stability calculations. IV - Part 6 Section 7 H Subdivision, Stability and Load Line Chapter 2 GL 2007 Page 7–7

2.4 The procedure described in 2.3 shall also the unit when floating since its vertical position rela- apply in cases of small notches or relatively narrow tive to the upper hull may be critical. See also Section cut-outs at the stern of the unit. 2 – Self Elevating Units.

2.5 Narrow wing extensions at the stern of the 4. Column stabilized units unit shall be considered as appendages and excluded for the determination of length L and for the calcula- 4.1 The hull form of this type of unit makes the tion of freeboards. calculation of geometric freeboard in accordance with the provisions of Chapter III of the 1966 Load Line 3. Self-elevating units Convention impracticable. Therefore the minimum freeboard of each column stabilized unit shall be determined by meeting the applicable requirements for 3.1 Load lines shall be assigned to self-elevating units as calculated under the terms of the 1966 Load − the strength of unit’s structure Line Convention taking into account 2.2 to 2.5. When floating or when in transit from one operational area to − minimum clearance between passing wave crests another, units shall be subject to all the conditions of and deck structure, see Section 3, B.1.3. assignment of that Convention unless specifically − intact and damage stability requirements excepted, e.g. from Reg. 39 (minimum bow height). However, these units shall not be subject to the term 4.2 The minimum freeboard shall be marked in of that Convention while they are supported by the appropriate locations on the structure. seabed or are in the process of lowering or raising their legs. 4.3 The enclosed deck structure of each column stabilized unit shall be made weathertight. For the consideration of moonpools see 2.3. 4.4 Windows, sidescuttles and portlights, includ- 3.2 The minimum freeboard of units which due ing those of the non-opening type, or other similar to their configuration cannot be computed by the nor- openings shall not be located below the deck structure mal methods laid down by the 1966 Load Line Con- of column stabilized units. vention shall be determined on the basis of meeting applicable intact stability, damage stability and struc- 4.5 Special consideration shall be given to the tural requirements in the afloat condition. position of openings which cannot be closed in emer- gencies, such as air intakes for emergency generators, 3.3 Some self-elevating units utilize a large mat having regard to the intact righting arm curves and the or similar supporting structure which contributes to final waterline after assumed damage. the buoyancy when the unit is floating. In such cases the mat or similar supporting structure shall be ig- 5. Pipelaying units nored in the calculation of freeboard. The mat or similar supporting structure shall, however, always be For the special requirements for watertight integrity taken into account in the evaluation of the stability of and stability of pipe laying units see Section 5, D.

IV - Part 6 Section 8 B Mooring Equipment Chapter 2 GL 2007 Page 8–1

Section 8

Mooring Equipment

A. General 3. Documents to be submitted Plans showing the arrangement and complete details of the anchoring system, including anchors, shackles, 1. Definitions anchor lines consisting of chain, wire or rope, together with details of fairleads, windlasses, winches and any 1.1 Temporary mooring equipment other components of the anchoring system and their foundations are to be submitted to GL. Temporary mooring equipment in the context of this Section is the mooring equipment consisting of anchors, cables, winches etc. intended to be used while the mobile offshore unit is not in a working condition B. Temporary Mooring Equipment but during voyages and location moves, and for anchoring within harbours or in sheltered areas. The 1. General equipment is to be designed to hold a unit in position when exposed to moderate environmental loads. 1.1 Temporary mooring equipment fitted in accordance with the provisions of this Section is to be designed for quick and safe operation in all foresee- 1.2 Positional mooring equipment able service conditions and for holding the unit at anchor. Positional mooring equipment in the context of this Section is a system for position keeping on the work- Note: ing location. The system is intended to keep the unit in 1. Temporary mooring equipment is, therefore, position, i.e. maintaining the prescribed limits of not intended to hold a unit off fully exposed coasts in movement during the work envisaged and preventing rough weather or to stop a unit which is moving or the unit or other floating bodies from drifting under all drifting. In this condition, the loads on the mooring anticipated sea and weather conditions. equipment increase to such a degree that its components may be damaged or lost owing to the high energy forces generated, particularly for large units. 2. Scope 2. In good holding ground the temporary moor- 2.1 As a condition of Class and for assigning the ing equipment required by this Section is intended to Class Notation  , the unit is to be provided with hold a unit in conditions such as to avoid dragging of temporary mooring equipment complying with the the anchor. In poor holding ground, the holding provisions of B. Deviations from this general require- power of the anchors will be significantly reduced. ment will be stated in the Class Certificate. 3. The Equipment Numeral formula for the temporary mooring equipment required in this Section 2.2 Positional mooring equipment, usually pro- is based on an assumed current speed of 2,5 m/sec, a vided for ship type and column stabilized units, is to wind speed of 25 m/sec, and a scope of chain cable comply with the provisions of C. An appropriate Nota- between 6 and 10, the scope being the ratio between tion may be affixed to the Character of Classification, length of chain paid out and water depth. see C.1.2. 1.2 The temporary mooring equipment shall 2.3 When separate temporary mooring equipment consist of anchors, chain cables, windlass or winches, is not fitted, consideration will be given to accepting chain stoppers, chain lockers (if chains are fitted) and the positional mooring equipment as equivalent to the wire ropes. rule requirements for temporary mooring equipment, The equipment of anchors and chain cables is to be if the provisions of B. are complied with. determined from Table 8.1.

2.4 Where positioning of the unit on the working 1.3 The anchors are to be effectively stowed and location is achieved by a dynamic positioning system, secured to prevent any movement at sea. If the an- the Notation DP will be affixed to the Character of chors are stowed at the shell, the shell plating is to be Class, see C.7. In that case separate temporary moor- increased in thickness and the framing may have to be ing equipment according to B. will be required. strengthened. Chapter 2 Section 8 B Mooring Equipment IV - Part 6 Page 8–2 GL 2007

1.4 The arrangements are to be such as to provide However, upon case-by-case consideration a an easy lead of chain cable/wire rope from the anchor reduced projected area of leeward structures to the windlass/winch and to ensure that the anchor may be accepted. can be dropped by its own weight without assistance. Reduction factors on account of the particular 1.5 Dimensioning shape of structures are normally not to be applied. 1.5.1 For the supporting structure under windlasses, chain stoppers, fairleads, sheaves and any other 3. Anchors items of equipment subjected to loads from the anchor cables as determined in accordance with the provi- 3.1 Number sions of 1.5.2 or 1.5.3, the following permissible stresses are to be observed: Two rule power anchors according to Table 8.1 are to − axial, bending stress: σ ≤ 0,8 ⋅ R be connected to their chain cables and positioned on b eH board ready for use. It is to be ensured that each an-

− shear stress: τ ≤ 0,5 ⋅ ReH chor can be stowed in the hawse and hawse pipe in such a way that it remains firmly secured in seagoing 22 − equivalent stress: σ=σ+⋅τ≤eq b3R eH conditions.

1.5.2 Where chain cables are led through hawse 3.2 Construction pipes, the acting forces are to be taken as 80 % or 45 % of the rated breaking load of the chain cable, i.e. 3.2.1 The anchors are to be made of materials and are to be tested as required in accordance with the GL − for chain stoppers: 80 % Rules II - Materials and Welding, Part 1 - Metallic Materials, Chapter 4 - Equipment, Section 1. − for windlasses: 80 % where no chain stoppers are fitted 3.2.2 The anchors must be of approved design. The − for windlasses: 45 % where chain stoppers mass of the heads of patent anchors (stockless an- are fitted chors), including pins and fittings, must comprise not less than 60 % of the total mass of the anchor. 1.5.3 Where hawse pipes are not installed and the chain cables are guided by fairleads and sheaves, the 3.2.3 In case of stock anchors, the total mass of the acting forces are to be taken as 100 % or 50 % of the anchor including the stock must comply with the val- rated braking load of the chain cable, i.e. ues given in Table 8.1. The weight of the stock should be approximately 20 % of this total mass. − for chain stoppers: 100 % − for windlasses: 100 % where no chain 3.2.4 The mass of each individual anchor may stoppers are fitted deviate from the tabular mass by up to 7 % as long as the total mass of the anchors fitted and attached to the − for windlasses: 50 % where chain stoppers chain cables is not less then twice the tabular mass of are fitted one anchor.

2. Equipment numeral 3.3 High holding power anchors

The equipment numeral Z is to be calculated as fol- 3.3.1 Where anchors with increased holding power lows: are intended to be used, a special approval procedure 2/3 is required, as described in 3.4. The following reduced ZD=+ fW masses may be admitted:

D = moulded displacement [t] in seawater having − for ‘High Holding Power’ (HHP) anchors: a density of 1,025 t/m³ when at anchor 75 % of the tabular mass f = projected area of all surfaces above the water W − for ‘Very High Holding Power’ (VHHP) anchors: line [m²] perpendicular to the wind direction 50 % of the tabular mass when at anchor The masking effect of structures located behind 3.3.2 The dimensions of the chain cable and wind- each other is normally not to be taken into ac- lass are to be based on the tabular anchor mass as count. given in Table 8.1. IV - Part 6 Section 8 B Mooring Equipment Chapter 2 GL 2007 Page 8–3

Table 8.1 Definition of anchors and chain cables

2 stockless bower Stud link chain cables Number. for. Equipment anchors Reg. numeral Z Mass per Diameter Total length anchor 1 d1 D2 d3 [−] [−] [kg] [m] [mm] [mm] [mm] 120 720 – 780 2280 467,5 48 42 36 121 780 – 840 2460 467,5 50 44 38 122 840 – 910 2640 467,5 52 46 40 123 910 – 980 2830 495 54 48 42 124 980 – 1060 3060 495 56 50 44 125 1060 – 1140 3300 495 58 50 46

126 1140 – 1220 3540 522,5 60 52 46 127 1220 – 1300 3780 522,5 62 54 48 128 1330 – 1390 4050 522,5 64 56 50 129 1390 – 1480 4320 550 66 58 50 130 1480 – 1570 4590 550 68 60 52

131 1570 – 1670 4890 550 70 62 54 132 1670 – 1790 5450 577,5 73 64 56 133 1790 – 1930 5610 577,5 76 66 58 134 1930 – 2080 6000 577,5 78 68 60 135 2080 – 2230 6450 605 81 70 62

136 2230 – 2380 6900 605 84 73 64 137 2380 – 2530 7350 605 87 76 66 138 2530 – 2700 7800 632,5 90 78 68 139 2700 – 2870 8300 632,5 92 81 70 140 2870 – 3040 8700 632,5 95 84 73

141 3040 – 3210 9300 660 97 84 76 142 3210 – 3400 9900 660 100 87 78 143 3400 – 3600 10500 660 102 90 78 144 3600 – 3800 11100 687,5 105 92 81 145 3800 – 4000 11700 687,5 107 95 84

146 4000 – 4200 12300 687,5 111 97 87 147 4200 – 4400 12900 715 114 100 87 148 4400 – 4600 13500 715 117 102 90 149 4600 – 4800 14100 175 120 105 92 150 4800 – 5000 14700 742,5 122 107 95

Chapter 2 Section 8 B Mooring Equipment IV - Part 6 Page 8–4 GL 2007

Table 8.1a Definition of anchors and chain cables (Continuous)

2 stockless bower Stud link chain cables Number. for. Equipment anchors Reg. numeral Z Mass per Diameter Total length anchor 1 d1 D2 d3 [−] [−] [kg] [m] [mm] [mm] [mm] 151 5000 – 5200 15400 742,5 124 111 97 152 5200 – 5500 16100 742,5 127 111 97 153 5500 – 5800 16900 742,5 130 114 100 154 5800 – 6100 17800 742,5 132 117 102 155 6100 – 6500 18800 742,5 120 107

156 6500 – 6900 20000 770 124 111 157 6900 – 7400 21500 770 127 114 158 7400 – 7900 23000 770 132 117 159 7900 – 8400 24500 770 137 122 160 8400 – 8900 26000 770 142 127

161 8900 – 9400 27500 770 147 132 162 9400 – 10000 29000 770 152 132 163 10000 – 10700 31000 770 137 164 10700 – 11500 33000 770 142 165 11500 – 12400 35500 770 147

166 12400 – 13400 38500 770 152 167 13400 – 14600 42000 770 157 168 14600 – 16000 46000 770 162

d1 = chain diameter Grade K1 (ordinary quality)

d2 = chain diameter Grade K2 (special quality)

d3 = chain diameter Grade K3 (extra quality) 1 not recommended for offshore use

3.4 Approval procedure 3.4.2 The chain length used in the tests should be approx. 6 to 10 times the depth of water.

3.4.1 For approval as a "High Holding Power An- chor", satisfactory tests are to be made on various 3.4.3 The tests are normally to be carried out from types of bottom and the anchor is to have a holding a tug, however, alternative shore based tests (e.g. with power at least twice that of a patent anchor ("Admi- suitable winches) may be accepted. ralty Standard Stockless") of the same mass. The mass of anchors to be tested should be representative of the Three tests are to be carried out for each anchor and full range of sizes intended to be manufactured. The type of bottom. The pull shall be measured by means tests are to be carried out on at least two sizes of an- of a dynamometer or recorded by a recording instru- chors in association with the chain cables appropriate ment. Measurements of pull based on rpm/bollard pull to the weight. The anchors to be tested and the stan- curve of the tug may be accepted. Testing by compari- dard stockless anchors should be of approx. the same son with a previously approved HHP anchor may be mass. accepted as a basis for approval. IV - Part 6 Section 8 B Mooring Equipment Chapter 2 GL 2007 Page 8–5

3.4.4 The maximum mass of an anchor thus ap- kept on board to facilitate fitting of the spare anchor at proved may be 10 times the mass of the largest size of any time. anchor tested. 4.7 Attachment of cable ends 3.5 Positional anchors 4.7.1 The inboard ends of the chain cables are to be Anchors used as positional anchors in accordance with secured to the structure. The attachment is to be able C., which must be specially laid the right way up or to withstand a force not less than 15 % nor more than which require flukes and profile to be adjusted to meet 30 % of the rated breaking load of the chain cable. sea bed conditions, will not normally be approved for temporary mooring purposes. 4.7.2 The attachment of the inboard ends of the chain cables to the unit’s structure is to be provided 4. Mooring chain cables and accessories with suitable means to permit, in case of emergency, an easy slipping of the chain cables to sea from an 4.1 The chain cable diameters given in Table 8.1 accessible position outside the chain locker. apply to chains complying with the requirements of the GL Rules II – Materials and Welding, Part 1 – 4.8 Wire ropes Metallic Materials, Chapter 4 - Equipment, Section 2, where Where wire ropes are fitted in lieu of chain cables, the following applies: − Grade K 1 (ordinary quality) − The length of ropes is to be equal to 1,5 times the − Grade K 2 (special quality) corresponding tabular chain cable length. − Grade K 3 (extra special quality) − The ropes’ breaking strength is not to be less than are defined. the breaking strength of the tabular Grade K 1 chain cable. Strength according to Grade K 2 chains is recommended. 4.2 Grade K1 chain cable should not be used for offshore applications. Where the installation of off- − A short length of chain cable is to be fitted be- shore quality mooring chains is intended, the provi- tween anchor and wire rope. Wire rope winches sions of C.4. apply. are to be fitted which comply with the rules for windlasses, see Chapter 5, Section 8, A. 4.3 Grade K 2 and K 3 chain cables must be post production quenched and tempered and shall be pur- 5. Chain locker chased only from recognized manufacturers. 5.1 The chain locker is to be of adequate capacity 4.4 Chain cables or wire ropes, if fitted, are to be and depth to facilitate an easy direct lead of the cables made of materials and tested in accordance with the through the chain pipes and to permit self-stowing of GL Rules mentioned under 4.1. the cables. The chain locker is to be provided with internal divisions so that the chain cables may be fully 4.5 Where the total mass of anchors is divided and separately stowed. into three or four anchors, see 3.1, the chain cable The minimum required stowage capacity without mud diameter and lengths are to be determined from Table box for the two bower anchor chains is as follows: 8.1 for the mass of the anchor actually fitted. The chain cable length is to be determined by dividing the 1,1⋅ d 2 ⋅ A S = [m3] tabular length by two and then multiplying by the 100000 number of anchors actually fitted, unless specified otherwise by the Owner/Operator. d = chain diameter [mm] according to Table 8.1 A = total length of stud link chain cable according to 4.6 Accessories Table 8.1 4.6.1 Anchor shackles shall be of an approved type The total stowage capacity is to be distributed on two and the material(s) shall conform to the GL Rules chain lockers of equal size for the port and starboard mentioned under 4.1. Kenter-type shackles are rec- chain cables. The shape of the base areas shall as far ommended. as possible be quadratic with a maximum edge length of 33 ⋅ d. As an alternative, circular base areas may be 4.6.2 A forerunner with swivel is to be fitted be- selected, the diameter of which shall not exceed (30 – tween anchor and chain cable. In lieu of a forerunner 35) ⋅ d. with swivel, an approved swivel shackle may be fitted. However, swivel shackles are not to be connected Above the stowage of each chain locker in addition a directly to the anchor shank unless specially approved. free depth of H = 1500 [mm] 4.6.3 Where a spare anchor is fitted, see 3.1, a sufficient number of suitable spare shackles is to be is to be provided. Chapter 2 Section 8 C Mooring Equipment IV - Part 6 Page 8–6 GL 2007

5.2 The chain locker boundaries and their access 2. Anchoring systems openings are to be watertight to prevent flooding of adjacent spaces, where essential installations or 2.1 Approval documents equipment are arranged, in order to not affect the proper operation of the unit after accidental flooding 2.1.1 Plans showing the arrangement and complete of the chain locker. details of the anchoring system, including anchors, shackles, anchor line components, wires, together with details of fairleads, windlasses, winches, controls and 5.3 Where the chain locker boundaries are also instrumentation, as well as any other components of tank bulkheads, the scantlings of plating and stiffeners the anchoring system and its foundations, are to be are to be determined as for tanks. submitted to GL for approval. 2.1.2 An analysis of the anchoring arrangements 5.4 Special requirements to minimize the in- expected to be utilised during the unit’s operation is to gress of water be submitted to GL. Among items to be addressed are: − design environmental conditions: waves, wind, currents, tides, and ranges of water depth 5.4.1 Spurling pipes and cable lockers are to be watertight up to the weather deck. − anchor holding capacities for various seabed soil conditions

5.4.2 Where means of access is provided, it is to be − air and sea temperature closed by a substantial cover and secured by closely − ice conditions, if applicable spaced bolts. − description of analysis method

5.4.3 Spurling pipes through which anchor cables 2.1.3 Plans showing the towing arrangement(s) and are led are to be of suitable diameter and shall be pro- equipment are to be submitted for information. vided with permanently attached closing appliances to minimize water ingress. 2.2 Design conditions, safety factors

2.2.1 Redundancy 5.5 Adequate drainage facilities are to be pro- The anchoring system should be designed such that a vided. sudden failure of any single anchor line will not cause progressive failure of the remaining lines.

2.2.2 Loads

C. Positional Mooring Equipment Anchoring system components should be designed utilizing adequate safety factors and a design methodology suitable to identify the most severe loading condition for each component. In particular, sufficient 1. General numbers of heading angles together with the most severe combination of wind, current, and waves are to be considered, usually from the same direction, to 1.1 All units, except self-elevating units and determine the maximum tension in each mooring line. submersible units, should be provided with positional mooring equipment designed to maintain the floating When a particular site is being considered, any appli- unit on station in all design conditions valid for its cable cross sea conditions are also to be taken into intended area(s) of operation. account in the event that they might induce higher mooring loads.

1.2 Units provided with positional mooring 2.2.3 Quasi static methods equipment in accordance with 1.1 will be eligible to When the Quasi static method is applied, the tension the special optional Class Notation "EQUIPPED in each anchor line is to be calculated at the maximum WITH POSITION MOORING SYSTEM" added to excursion for each design condition defined in 2.2.4, the Character of Classification in accordance with the combining the following steady state and dynamic GL Rules, see Chapter 1, Section 2, C.2.9. responses of the unit: a) Steady mean offset due to the defined wind, current, and steady wave forces. 1.3 Units provided with thrusters serving (also) for position keeping will be eligible for the special b) Most probable maximum wave induced motions of Notations DP1 to DP3, see 7. the moored unit due to wave excitation. IV - Part 6 Section 8 C Mooring Equipment Chapter 2 GL 2007 Page 8–7

For relatively deep water, the effect from damping and unit, unless GL is satisfied that lesser conditions may inertia forces in the anchor lines is to be considered in be applicable to specific sites. the analysis. 2.2.6 In general, the maximum wave induced mo- The effects of slowly varying motions are to be in- tions of the moored unit about the steady mean offset cluded for column stabilized units when the magni- should be obtained by means of model tests. GL may tudes of such motions are considered to be significant. accept analytical calculations provided that the proposed method is based on a sound methodology which 2.2.4 When the Quasi Static Method outlined in has been validated by model tests. 2.2.3 is applied, the minimum factors of safety at the maximum excursion of the unit for a range of head- Wind loads shall be determined according to the prin- ings should be considered according to Table 8.2 ciples shown in Chapter 4, Section 1, B. and Section 2, B.2. The results of wind tunnel tests, as well as other recognized criteria, may be considered. Table 8.2 Minimum factors of safety 2.2.7 GL may accept different analysis methodolo- Design condition Safety factor gies provided that a level of safety equivalent to the one obtained by 2.2.3 and 2.2.4 is ensured. Operating 2,7 Severe storm 1 1,8 2.2.8 GL may give special consideration to an arrangement where the anchoring systems are used in Operating – one line failed 1,8 conjunction with thrusters to maintain the unit on station, see 1.3 and 7. Severe storm – one line failed 1 1,25 1 see Chapter 4, Section 3, C.: Extreme environ- 3. Anchors mental loads 3.1 General P Safety factor = B Type/design, materials, manufacture and testing of Tmax anchors used for position mooring shall comply with the GL Rules mentioned under B.3., if Certification by Tmax = characteristic tension in the anchor line, equal GL is requested. to the maximum value obtained according to 2.2.2 and 2.2.3 Anchors specially designed for position mooring are normally not to be used for temporary mooring, see PB = minimum rated breaking strength of the an- B.3.5. chor line 3.2 Testing 2.2.4.1 Operating Anchors shall be subjected to load tests according to For the most severe design environmental condition the Rule requirements, in approved testing installa- for normal operations as defined by the Owner or tions. After application of the test load, it must be Designer see Chapter 4, Section 3, C.4.2. shown that the anchor is free of any defects/ deforma- tions resulting from testing, and fully operable. 2.2.4.2 Severe Storm Test loads are shown in Table 8.3. For anchors with For the most severe design environmental condition increased holding capacity, the following test loads for severe storm as defined by the Owner or Designer have to be applied: see Chapter 4, Section 3, C.4.3. HHP anchors: A load corresponding to 1,33 × mass 2.2.4.3 Operating - One Line Failed of anchor. Situation which follows a failure of any one mooring VHHP anchors: A load corresponding to 2 × mass line in the operating condition. of anchor. 2.2.4.4 Severe Storm - One Line Failed 3.3 Anchors are to be securely stowed on board Situation which follows a failure of any one mooring to prevent movement during transit/towage. line in the severe storm condition. 4. Anchor lines (mooring chain cables) 2.2.5 Dynamic analysis When a dynamic analysis is employed, other safety 4.1 General requirements factors may be considered to the satisfaction of GL. 4.1.1 GL are to be ensured that the anchor lines are The defined operating and severe storm conditions are of a type/composition that will satisfy the design con- to be the same as those identified for the design of the ditions of the anchoring system. In general anchor Chapter 2 Section 8 C Mooring Equipment IV - Part 6 Page 8–8 GL 2007

cables may be of wire, rope, chain or any combination Table 8.3 Test loads for anchors 1 thereof. For wire ropes see B.4.8. Mass Test load Mass Test load 4.1.2 Means are to be provided to enable the an- [kg] [kN] [kg] [kN] chor lines to be released from the unit after loss of main power. 2200 367 7800 861 2300 388 8000 877 2400 401 8200 892 4.1.3 Means are to be provided for measuring an- 414 chor line tensions. 2500 8400 908 2600 427 8600 922 4.1.4 Anchor lines are to be of adequate length to 2700 438 8800 936 prevent uplift of the anchors under the maximum 2800 450 9000 949 462 design load condition for the anticipated area(s) of 2900 9200 961 operation. 3000 474 9400 975 3100 484 9600 987 3200 495 9800 998 4.2 Offshore mooring chain cables - material 506 requirements 3300 10000 1010 3400 517 10500 1040 4.2.1 General Requirements 3500 528 11000 1070 3600 537 11500 1090 547 4.2.1.1 Scope 3700 12000 1110 3800 557 12500 1130 These Rules apply to the materials, design, manufac- 3900 567 13000 1160 ture and testing of offshore mooring chains and acces- 4000 577 13500 1180 sories intended to be used for applications such as: 4100 586 14000 1210 mooring of mobile offshore units, mooring of floating 595 production units, mooring of offshore loading systems 4200 14500 1230 4300 604 15000 1260 and mooring of gravity based structures during fabri- 613 cation. 4400 15500 1270 4500 622 16000 1300 Mooring equipment covered are common links, con- 4600 631 16500 1330 nection common links (splice links), enlarged links, 4700 638 17000 1360 end links, detachable connecting links (shackles), and 4800 645 17500 1390 shackles, swivels and swivel shackles. 4900 653 18000 1410 5000 661 18500 1440 4.2.1.2 Chain cable grades 5100 669 19000 1470 5200 677 19500 1490 Depending on the nominal tensile strength of the 5300 685 20000 1520 steels used for manufacture, chain cables are to be subdivided into three grades, i.e.: GL-R3, GL-R3S, 5400 691 21000 1570 GL-R4. 5500 699 22000 1620 5600 706 23000 1670 4.2.1.3 Approval of chain cable manufacturers 5700 713 24000 1720 5800 721 25000 1770 4.2.1.3.1 Offshore mooring chain cables are to be 5900 728 26000 1800 manufactured only by works approved by GL. For this 6000 735 27000 1850 purpose approval tests are to be carried out, the scope 6100 740 28000 1900 of which is to include proof and breaking load tests, measurements and mechanical tests including fracture 6200 747 29000 1940 754 mechanic tests. 6300 30000 1990 6400 760 31000 1030 6500 767 32000 1070 4.2.1.3.2 Manufacturers are to submit for review and approval the sequence of operations from receiving 6600 773 34000 2160 inspection to shipment, and details of the following 6700 779 36000 2250 manufacturing processes: 6800 786 38000 2330 6900 794 40000 2410 a) Bar heating and bending including method, tem- 804 perature control and recording. 7000 42000 2490 7200 818 44000 2570 b) Flash welding including current, force, time and 7400 832 46000 2650 dimensional variables as well as control and re- 7600 845 48000 2730 cording of parameters. 1 Intermediate values can be determined by linear interpolation c) Flash removal including method and inspection. IV - Part 6 Section 8 C Mooring Equipment Chapter 2 GL 2007 Page 8–9

d) Stud insertion method. 4.2.2 Materials e) Heat treatment including furnace types, means of 4.2.2.1 Scope specifying, controlling and recording of temperature and chain speed and allowable limits, quench- These requirements apply to rolled steels, forgings and ing bath and agitation, cooling method after exit. castings used for the manufacture of offshore mooring chain cables and accessories. f) Proof and break loading including method/ machine, means of horizontal support, if applicable, method of measurement recording. 4.2.2.2 Rolled steel bars g) Non-destructive examination procedures. 4.2.2.2.1 Steel manufacture 4.2.1.3.3 Calibration of furnaces shall be verified by The steels are to be manufactured by basic oxygen, measurement and recording of actual link temperature electric furnace or such other process as may be spe- (surface and internal). cially approved. All steels are to be killed and fine grain treated. 4.2.1.4 Approval of quality system at chain cable manufacturers 4.2.2.2.2 Chemical composition Chain cable manufacturers are to have a documented and effective quality system approved by GL, e.g. For acceptance tests, the chemical composition of according to ISO 9001. ladle samples of each heat is to be determined by the steel maker and is to comply with the approved speci- 4.2.1.5 Approval of steel mills for rolled bars fication.

4.2.1.5.1 Bar material intended for chain and accesso- 4.2.2.2.3 Mechanical tests ries are to be manufactured only by works approved by GL. The approval is limited to a nominated sup- .1 Bars of the same nominal diameter are to be plier of bar material. If a chain cable manufacturer presented for test in batches of 50 tonnes or fraction wishes to use material from a number of suppliers, thereof from the same heat. Test specimens are to be separate approval tests must be carried out for each taken from material heat treated in the same manner as supplier. intended for the finished chain. Approval will be given only after successful testing of .2 Each heat of Grade GL-R3S and GL-R4 steel the completed chain cable. The approval will normally bars is to be tested for hydrogen embrittlement. In be limited to a thickness equal to that of the bars case of continuous casting, test samples representing tested. the beginning and the end of the charge shall be taken. In case of ingot casting, test samples representing two 4.2.1.5.2 The steel maker is to submit a specification different ingots shall be taken. of the chemical composition of the bar material, which must be approved by GL and by the chain cable manu- Two (2) tensile test specimens shall be taken from the facturer. central region of bar material which have been simulated heat treated. The specimens shall preferably have For Grade GL-R4 chain cables the steel should con- a diameter of 20 mm, alternatively 14 mm. One tain a minimum of 0,20 per cent molybdenum. specimen is to be tested within max. 3 hours after machining. For a 14 mm diameter specimen, the time 4.2.1.5.3 A heat treatment sensitivity study simulating limit is 1,5 hours. Alternatively, the specimen may be chain cable production conditions shall be applied in cooled to – 60 °C immediately after machining and order to verify mechanical properties and establish kept at that temperature for a period of max. 5 days. limits for temperature and time combinations. The other specimen is to be tested after baking at 250 °C for 4 hours, alternatively 2 hours for 14 mm diame- 4.2.1.5.4 The bar manufacturer is to provide evidence ter specimen. that the material is resistant to strain ageing, temper embrittlement and hydrogen embrittlement. A slow strain ≤ 0,0003 s-1 must be used during the entire test, until fracture occurs. This means approx. 4.2.1.6 Approval of forges and foundries for ac- 10 minutes for a 20 mm diameter specimen. cessories Tensile strength, elongation and reduction of area are 4.2.1.6.1 Forges and foundries intending to supply to be reported. The requirement for the test is: finished or semifinished accessories are to be approved by GL. The scope of approval is to be agreed Z1 with GL. ≥ 0,85 Z2 4.2.1.6.2 Manufacturers intending to supply accesso- Z1 = reduction of area without baking ries in machined condition (e.g. Kenter type shackles) are to submit detailed drawings for approval. Z2 = reduction of area after baking Chapter 2 Section 8 C Mooring Equipment IV - Part 6 Page 8–10 GL 2007

If the requirement Z1 / Z2 ≥ 0,85 is not met, the bar The frequency of non-destructive examinations may material may be subjected to a hydrogen degassing be reduced at the discretion of GL provided it is veri- treatment after agreement with GL. New tests shall be fied by statistical means that the required quality is performed after degassing. consistently achieved. .3 For all grades, one tensile and three Charpy V-notch specimens are to be taken from each sample 4.2.2.2.6 Marking selected. The test specimens are to be taken at ap- Each bar is to be stamped with the steel grade designa- proximately one-third radius below the surface, as tion and the charge number (or a code indicating the shown in Fig. 8.1. charge number) on one of the end surfaces. Other The results of all tests are to be in accordance with the marking methods may be accepted subject to agree- appropriate requirements of Table 8.4. ment. .4 If the tensile test requirements are not 4.2.2.3 Forged steels achieved, a retest of two further specimens selected from the same sample shall be permissible. Failure to 4.2.2.3.1 Forged steels used for the manufacture of meet the specified requirements of either or both of accessories must be in compliance with specifications the additional tests will result in rejection of the batch submitted and approved. represented, unless it can be clearly attributed to im- proper simulated heat treatment. specimen for notched bar impact test 4.2.2.2.4 Dimensional tolerances The diameter and roundness shall be within the tolerances specified in Table 8.5, unless otherwise agreed. r/3

4.2.2.2.5 Non-destructive examination and repair The bars shall be free from pipe, cracks and flakes. Bar material is to be subjected to ultrasonic examination at an appropriate stage of the manufacture. One hundred percent of the bar material is to be examined by magnetic particle or eddy current methods. The bars shall be free of injurious surface imperfec- r/3 tions such as seams, laps and rolled-in mill scale. tensile specimen Provided that their depth is not greater than 1 % of the bar diameter, longitudinal discontinuities may be removed by grinding and blending to a smooth contour. Fig. 8.1 Location of test specimens

Table 8.4 Mechanical properties of offshore mooring chain cables

Charpy V-notch impact tests Tensile Elongation Reduction Average Yield stress 3 Test Average strength A5 of area energy flash Grade temperature energy weld [N/mm2] [N/mm2] [%] [%] [J] [J] [°C] 2 minimum minimum minimum minimum minimum minimum 0 60 50 GL-R3 410 690 17 50 - 20 40 30 0 65 53 GL-R3S 490 770 15 50 - 20 45 33 GL-R4 580 860 12 50 - 20 50 36

1 Aim value of yield to tensile ratio: 0,92 max 2 At the option of Society the impact test of Grade GL-R3 and GL-R3S may be carried out at either 0 °C or minus 20 °C. 3 Reduction of area of cast steel is to be: − for grades R3 and R3S: min. 40 % − for grades R4: min 35 % - cf. item 4.2.2.3.4

IV - Part 6 Section 8 C Mooring Equipment Chapter 2 GL 2007 Page 8–11

Table 8.5 Dimensional tolerances of bar stock 4.2.2.4.4 Mechanical properties material The castings must comply with the mechanical properties given in Table 8.4. Nominal Tolerance on Tolerance on diameter diameter roundness 4.2.2.4.5 Mechanical tests (dmax - dmin) For test sampling, castings of similar dimensions [mm] [mm] [mm] originating from the same heat treatment charge and below 25 -0 + 1,0 0,60 the same heat of steel are to be combined into one test unit. From each test unit one tensile and three impact 25 – 35 -0 + 1,2 0,80 test specimens are to be taken and tested. For the loca- 36 – 50 -0 + 1,6 1,10 tion of the test specimens see Fig. 8.1. 51 – 80 -0 + 2,0 1,50 4.2.2.4.6 Ultrasonic examination 81 – 100 -0 + 2,0 1,95 The castings are to be subjected to ultrasonic examina- 101 – 120 -0 + 3,0 2,25 tion in compliance with the standard submitted and approved. 121 – 160 -0 + 4,0 3,00 4.2.2.4.7 Marking 4.2.2.3.2 Chemical composition 4.2.2.3.7 applies. 4.2.2.2.2 applies. 4.2.2.5 Materials for studs 4.2.2.3.3 Heat treatment The studs are to be made of steel corresponding to that of the chain or in compliance with specifications sub- Finished forgings are to be properly heat treated in mitted and approved. In general, the carbon content compliance with specifications submitted and ap- should not exceed 0,25 per cent if the studs are to be proved. welded in place. 4.2.2.3.4 Mechanical properties 4.2.3 Design and chain cable manufacture 4.2.3.1 Design The forgings must comply with the mechanical properties given in Table 8.4, when properly heat treated. Drawings giving detailed design of chain cables and accessories made by or supplied through the chain 4.2.2.3.5 Mechanical tests cable manufacturer are to be submitted for approval. Typical designs are given in ISO 1704: 1991. For test sampling, forgings of similar dimensions, that means that diameters do not differ by more than 25 In addition, drawings showing the detailed design of mm, originating from the same heat treatment charge the stud shall be submitted for information. The stud and the same heat of steel are to be combined into one shall give an impression in the chain link which is test unit. From each test unit one tensile and three sufficiently deep to secure the position of the stud, but impact test specimens are to be taken and tested. For the combined effect of shape and depth of the impres- the location of the test specimens see Fig. 8.1. sion shall not cause any harmful notch effect or stress concentration in the chain link. 4.2.2.3.6 Ultrasonic examination Machining of Kenter shackles shall result in fillet The forgings are to be subjected to ultrasonic exami- radius min. 3 % of nominal diameter. nation at an appropriate stage of manufacture and in compliance with the standard submitted and approved. 4.2.3.2 Manufacturing process Offshore mooring chain cables shall be manufactured 4.2.2.3.7 Marking in continuous lengths by flash butt welding and are to Marking is to be similar to that specified in 4.2.2.2.6. be heat treated in a continuous furnace; batch heat treatment is not permitted. 4.2.2.4 Cast steels The use of joining shackles to replace defective links is subject to the written approval of the end purchaser 4.2.2.4.1 Cast steels used for the manufacture of ac- in terms of the number and type permitted. The use of cessories must be in compliance with specifications connecting common links is restricted to 3 links in submitted and approved. each 100 m of chain cable. 4.2.2.4.2 Chemical composition 4.2.3.3 Manufacturing process records 4.2.2.2.2 applies. 4.2.3.3.1 Documentation 4.2.2.4.3 Heat treatment Records of bar heating, flash welding and heat treat- All castings are to be properly heat treated in compli- ment shall be made available for inspection by the ance with specifications submitted and approved. Surveyor. Chapter 2 Section 8 C Mooring Equipment IV - Part 6 Page 8–12 GL 2007

4.2.3.3.2 Bar heating 4.2.3.3.4 Heat treatment For electric resistance heating, the heating phase shall Chain cables shall be austenitized above the upper be controlled by an optical heat sensor. The controller transformation temperature, at a combination of tem- shall be checked at least once every 8 hours and re- perature and time within the limits established. cords made. When applicable, chain cables shall be tempered at a For furnace heating, the temperature shall be con- combination of temperature and time within the limits trolled and continuously recorded using thermocou- established. ples in close proximity to the bars. The controls shall Temperature and time or temperature and chain speed be checked at least one every 8 hours and records shall be controlled and continuously recorded. made. 4.2.3.3.3 Flash welding 4.2.3.4 Mechanical properties The following welding parameters shall be controlled The mechanical properties of finished chain cables during welding of each link: and accessories are to be in accordance with Table 8.4. For the location of test specimens see Figs. 8.1 and a) Platen motion. 8.2. b) Current as a function of time. 4.2.3.5 Proof and break load tests c) Hydraulic pressure. Chain cables and accessories are to withstand the The controls shall be checked at least every 4 hours proof and breaking load tests given in Table 8.6. and records made.

specimen for notched specimen for notched bar impact test bar impact test r/3 r/3 r/3

tensile specimen

Fig. 8.2 Location of test specimens

Table 8.6 Formulas for proof and breaking load tests, weight and length over 5 links

Grade GL-R3 Grade GL-R3S Grade GL-R4 Proof test load [kN] 0,0148 d2 (44-0,08d) 0,0180 d2 (44-0,08d) 0,0216 d2 (44-0,08d) Break test load [kN] 0,0223 d2 (44-0,08d) 0,0249 d2 (44-0,08d) 0,0274 d2 (44-0,08d) Chain weight [kg/m] 0,0219 d2

Length over 5 links Min. [mm] 22 d Max. [mm] 22,55 d

IV - Part 6 Section 8 C Mooring Equipment Chapter 2 GL 2007 Page 8–13

4.2.3.6 Freedom from defects 4.2.3.8.3 The stud ends must have a good fit inside the link and the weld is to be confined to the stud end All chain cables are to have a workmanship like finish opposite to the flash butt weld. The full periphery of consistent with the method of manufacture and be free the stud end is to be welded unless otherwise ap- from defects. Each link is to be examined in accor- proved. dance with 4.2.4.5 using approved procedures. 4.2.3.8.4 Welding of studs at both ends is not permit- 4.2.3.7 Dimensions and dimensional tolerances ted unless specially approved. 4.2.3.7.1 The shape and proportion of links and accessories must conform to ISO 1704: 1991 or to the a designs specially approved. d 4.2.3.7.2 The following tolerances are applicable to links: a) Nominal diameter measured at the crown: up to 40 mm nominal diameter: – 1 mm over 40 up to 84 mm nominal diameter: – 2 mm over 84 up to 122 mm nominal diameter: – 3 mm a over 122 mm nominal diameter: – 4 mm

The plus tolerance may be up to 5 % of the nominal A diameter. The cross sectional area at the crown shall have no negative tolerance. off-centre distance: b) Diameters measured at locations other than the A - a X = crown: The diameter is to have no negative toler- 2 ance. The plus tolerance may be up to 5 % of the nominal diameter. The approved manufacturer Fig. 8.3 Tolerances for stud position specification is applicable to the plus tolerance of the flash butt weld. 4.2.3.8.5 The welds are to be made by qualified weld- c) The allowable manufacturing tolerance on a length ers using an approved procedure and low-hydrogen of five links is + 2,5 %, but may not be negative. approved consumables. d) All other dimensions are subject to a manufacturing tolerance of ± 2,5 %, provided always that all 4.2.3.8.6 The size of the fillet weld shall as a mini- parts fit together properly. mum be as per API specification 2F. e) Studs must be located in the links centrally and at 4.2.3.8.7 The welds are to be of good quality and free right angles to the sides of the link. The following from defects such as cracks, lack of fusion, gross po- tolerances are acceptable provided that the stud fits rosity and undercuts exceeding 1 mm. snugly and its ends lie flush against the inside of the link: 4.2.3.8.8 All stud welds shall be visually examined. Maximum off-centre distance "X" is 10 % of the At least 10 per cent of all stud welds within each nominal diameter, Maximum deviation a" from the length of chain shall be examined by dye penetrant or 90°- position is 4°. magnetic particle after proof load testing. If cracks or lack of fusion are found, all stud welds in that length The tolerances are to be measured in accordance with are to be examined. Fig. 8.3. 4.2.3.9 Connecting common links 4.2.3.7.3 The following tolerances are applicable to accessories: 4.2.3.9.1 Single links to substitute for test links or a) Nominal diameter: + 5,0 %, – 0 % defective links without the necessity for re-heat treatment of the whole length are to be made in accordance b) Other diameters: ± 2,5 % with an approved procedure. Separate approvals are 4.2.3.8 Welding of studs required for each grade of chain cables and the tests are to be made on the maximum size of chain cables 4.2.3.8.1 A welded stud may be accepted for grade for which approval is sought. GL-R3 and GL-R3S chains. Welding of studs in grade GL-R4 chains is not permitted unless specially ap- 4.2.3.9.2 Manufacture and heat treatment of connect- proved. ing common links is not to affect the properties of the adjoining links. The temperature reached by these 4.2.3.8.2 Where studs are welded into the links this is links is nowhere to exceed 80 % of the tempering to be completed before the chain is heat treated. temperature. Chapter 2 Section 8 C Mooring Equipment IV - Part 6 Page 8–14 GL 2007

4.2.3.9.3 Each link is to be subjected to the appropri- 4.2.4.3.2 The entire chain cable is to be checked for ate proof load and non-destructive examination as the length, five links at a time. By the five link check detailed in Table 8.6 and 4.2.4.5. A second link shall the first five links shall be measured. From the next set be made identical to the connecting common link; the of five links, at least two links from the previous five link shall be tested and inspected according to 4.2.4.4. links set shall be included. This procedure is to be and 4.2.4.5. followed for the entire chain cable length. The measurements are to be taken preferably while the chain 4.2.3.9.4 Each connecting common link is to be cable is loaded to 5 – 10 % of the minimum proof marked on the stud in accordance with 4.2.4.7 plus an load. The links held in the end blocks may be ex- unique number for the link. The adjoining links are cluded from this measurement. also to be marked on the studs.

Table 8.7 Frequency of breaking load and me- 4.2.4 Testing and inspection of finished chain chanical tests cables

4.2.4.1 General Nominal chain Maximum sampling diameter interval [mm] [m] All chain cables are to be subjected to proof load tests, breaking load tests and mechanical tests after final Min - 48 91 heat treatment in the presence of a GL Surveyor. 49 - 60 110 Where the manufacturer has a procedure to record 61 - 73 131 proof loads and the Surveyor is satisfied with the adequacy of the recording system, he needs not witness 74 - 85 152 all proof load tests. The Surveyor is to satisfy himself 86 - 98 175 that the testing machines are calibrated and maintained 99 - 111 198 in a satisfactory condition. 112 - 124 222 Prior to test and inspection the chain cable is to be free from scale, paint or other coating. The chain cable shall be sand or shot blasted to meet this requirement. 4.2.4.4 Mechanical tests 4.2.4.2 Proof and breaking load tests Links of samples detached from finished, heat treated 4.2.4.2.1 The entire length of chain cable shall with- chain shall be sectioned for determination of mechani- stand the proof load specified in Table 8.6 without cal properties. A test unit shall consist of one tensile fracture and shall not crack in the flash weld. The load and nine impact specimens. The tensile specimen shall applied shall not exceed the proof load by more than be taken at the side opposite the flash weld. Three 10 % when stretching the chain cable. Where plastic impact specimens shall be taken across the flash weld straining is used to set studs, the applied load is not to with the notch centred in the middle. Three impact be greater than that qualified in approval tests. specimens shall be taken across the unwelded side and three impact specimens shall be taken from the bend 4.2.4.2.2 A breaking load test specimen consisting of region. at least 3 links is to be either taken from the chain or produced at the same time and in the same manner as The test frequency is to be based on tests at sampling the chain. The test frequency is to be based on tests at intervals according to Table 8.7 provided that every sampling intervals according to Table 8.7 provided cast is represented. Mechanical properties shall be as that every cast is represented. Each specimen shall be specified in Table 8.4. capable of withstanding the break load specified without fracture and shall not crack in the flash weld. It The frequency of impact testing in the bend may be shall be considered acceptable if the specimen is reduced at the discretion of GL provided it is verified loaded to the specified value and maintained at that by statistical means that the required toughness is load for 30 seconds. consistently achieved.

If the loading capacity of the testing machine is insuf- 4.2.4.5 Non-destructive examination ficient, another equivalent method shall be agreed with GL. 4.2.4.5.1 After proof load testing, all surfaces of every link shall be visually examined. Burrs, irregu- 4.2.4.3 Dimensions and dimensional tolerances larities and rough edges shall be contour ground. Links shall be free from mill defects, surface cracks, 4.2.4.3.1 After proof load testing measurements are to dents and cuts, especially in the vicinity where gripped be taken on at least 5 per cent of the links in accor- by clamping dies during flash welding. Studs shall be dance with 4.2.3.7. securely fastened. IV - Part 6 Section 8 C Mooring Equipment Chapter 2 GL 2007 Page 8–15

4.2.4.5.2 Magnetic particle procedures shall be em- be subjected to the breaking load test. Based upon ployed to examine the flash welded area including the satisfactory results of the additional tests and the re- area gripped by the clamping dies. Procedures and sults of the failure investigation, it will be decided equipment in accordance with those approved shall be what lengths of chain cable can be accepted. Failure of used. The frequency of examination shall be every either or both of the additional tests will result in re- link. Link surface at the flash weld shall be free from jection of the sampling length of chain represented, cracks, lack of fusion and gross porosity. and 4.2.4.6.2 shall apply. 4.2.4.5.3 Ultrasonic procedures shall be employed to 4.2.4.6.7 If a link fails during proof load testing, a examine the flash weld fusion. Procedures and equip- thorough examination, with the Surveyor informed in ment in accordance with those approved shall be used. a timely manner, is to be carried out to identify the On-site calibration standards for chain cable configu- probable cause of failure of the proof load test. In the rations shall be approved. event that two or more links in the proof loaded length fail, that length is to be rejected. The frequency of examination shall be every link. The above failure investigation is to be carried out, The flash weld shall be free from defects causing especially with regard to the presence in other lengths, ultrasonic back reflections equal to or greater than the of factors or conditions thought to be causal to failure. calibration standard. In addition to the above failure investigation, a break- 4.2.4.6 Retest, rejection and repair criteria ing load test specimen is to be taken from each side of the one failed link, and subjected to the breaking load 4.2.4.6.1 If the length over 5 links is short, the chain test. Based upon satisfactory results of both breaking cable may be stretched by loading above the proof test load tests and the results of the failure investigation, it load specified provided that the applied load is not will be decided what length of chain can be considered greater than that approved and that only random for acceptance. Failure of either or both of the break- lengths of the chain cable need stretching. ing load tests will result in rejection of the proof If the length exceeds the specified tolerance, the over loaded length. length chain cable links shall be cut out and 4.2.4.6.2 shall apply. Replacement of defective links is to be in accordance with 4.2.4.6.2. 4.2.4.6.2 If single links are found to be defective or do not meet other applicable requirements, defective 4.2.4.6.8 If the tensile test fails to meet the require- links may be cut out and a connecting common link ments, a retest of two further specimens selected from inserted in their place. The individual heat treatment the same sample shall be permissible. Failure to meet and inspection procedure of connecting common links the specified requirements of either or both of the is subjected to the GL Surveyor’s approval. additional tests will result in rejection of the sampling length of chain cable represented, and 4.2.4.6.2 shall Other methods for repair are subject to the written apply. approval of GL and the end purchaser. 4.2.4.6.9 If the impact test requirements are not 4.2.4.6.3 If a crack, cut or defect in the flash weld is achieved, a retest of three further specimens selected found by visual or magnetic particle examination, it from the same sample shall be permissible. The results shall be ground down no more than 5 % of the link shall be added to those previously obtained to form a diameter in depth and streamlined to provide smooth new average. The new average shall comply with the contours. The final dimensions must still conform to requirements. Not more than two individual results are the agreed standard. to be lower than the required average and not more than one result is to be below 70 per cent of the speci- 4.2.4.6.4 If indications of interior flash weld defects fied average value. in reference to the accepted calibration standards are detected during ultrasonic examination, 4.2.4.6.2 shall Failure to meet the requirements will result in rejec- apply. tion of the sampling length represented, and 4.2.4.6.2 shall apply. 4.2.4.6.5 If link diameter, length, width and stud alignment do not conform to the required dimensions, 4.2.4.7 Marking these shall be compared to the dimensions of 40 more 4.2.4.7.1 The chain cable shall be marked at the fol- links, 20 on each side of the affected links. If a single lowing places: particular dimension fails to meet the required dimensional tolerance in more than 2 of the sample links, all − at each end links shall be examined, 4.2.4.6.2 shall apply. − at intervals not exceeding 100 m 4.2.4.6.6 If a breaking load test fails a thorough ex- − on links next to shackles or connecting common amination, with the Surveyor informed in a timely links manner, is to be carried out to identify the cause of failure. Two additional breaking test specimens repre- All marked links shall be stated on the Certificate, and senting the same sampling length of chain cable are to the marking shall make it possible to recognise lead- Chapter 2 Section 8 C Mooring Equipment IV - Part 6 Page 8–16 GL 2007

ing and tail end of the chain. In addition to the above 4.2.5 Testing and Inspection of Accessories required marking, the first and last common link of each individual charge used in the continuous length 4.2.5.1 General shall be adequately and traceably marked. All accessories are to be subjected to proof load tests, The marking shall be permanent and legible through- breaking load tests and mechanical tests after final out the expected lifetime of the chain. heat treatment in the presence of a Surveyor. Where the manufacturer has a procedure to record proof loads The chain cable shall be marked on the link as fol- and the Surveyor is satisfied with the adequacy of the lows, compare Fig. 8.4: recording system, he need not witness all proof load tests. The Surveyor is to satisfy himself that the testing − chain cable grade machines are calibrated and maintained in a satisfactory condition. − Test Certificate No. Prior to test and inspection the chain cable accessories − GL Surveyor’s stamp are to be free from scale, paint or other coating.

− month and year of test 4.2.5.2 Proof and breaking load tests

The Certificate number may be exchanged against an 4.2.5.2.1 All accessories are to be subjected to the abbreviation or equivalent. If so, this shall be stated in proof load specified for the corresponding chain. the Certificate. 4.2.5.2.2 Chain cable accessories are to be tested to The chain cable Certificate shall contain information the breaking test loads prescribed for the grade and on number and location of connecting common links. size of chain cable for which they are intended. At The Certificate number and replacement link number least one accessory out of every batch or every 25 may be exchanged against an abbreviation or equiva- accessories, whichever is less, is to be tested. lent. If so, this shall be stated in the Certificate. For individually produced accessories or accessories Test certificate no. produced in small batches, alternative testing will be subject to special consideration. Accessories which have been subjected to a breaking load test are to be XXXXXXX scrapped.

4.2.5.3 Dimensions and dimensional tolerances At least one accessory (of the same type, size and nominal strength) out of 25 is to be checked for di- XX XX Month and year of test mensions after proof load testing. The manufacturer is to provide a statement indicating compliance with the Grade of chain cable Surveyor's stamp purchaser’s requirements.

Fig. 8.4 Stamping of chain cables 4.2.5.4 Mechanical tests Accessories are to be subjected to mechanical testing 4.2.4.8 Documentation as described in 4.2.2.3 and 4.2.2.4. For individually produced accessories or accessories produced in small A complete Chain Cable Inspection and Testing Re- batches, alternative testing will be subjected to special port in booklet form shall be provided by the chain consideration. cable manufacturer for each continuous chain cable length. This booklet shall include all dimensional 4.2.5.5 Non-destructive examination checks, test and inspection reports, NDT reports, process records, photographs as well as details of any After proof load testing all chain cable accessories are non-conformity, corrective action and repair work. to be subjected to a close visual examination. Special attention is to be paid to machined surfaces and high Individual Certificates are to be issued for each con- stress regions. All non-machined surfaces are to be tinuous single length of chain cable. sand or shot blasted to permit a thorough examination. All accessories are to be checked by magnetic particle All accompanying documents, appendices and reports or dye penetration methods. shall carry reference to the original Certificate number. The manufacturer is to provide a statement that non- destructive examination has been carried out with The manufacturer will be responsible for storing, in a satisfactory results. This statement should include a safe and retrievable manner, all documentation estab- brief reference to the techniques and to the Operator’s lished for a period of at least 10 years. qualification. IV - Part 6 Section 8 C Mooring Equipment Chapter 2 GL 2007 Page 8–17

4.2.5.6 Test failures 5. Winch system In the event of a failure of any test the entire batch 5.1 Winches represented is to be rejected unless the cause of failure has been determined and it can be demonstrated to the The requirements for mooring winches including their Surveyor’s satisfaction that the condition causing the controls are defined in Chapter 5, Section 8, C. failure is not present in any of the remaining accessories. 5.2 Fairleads and sheaves 4.2.5.7 Marking Fairleads and sheaves shall be designed to prevent excessive bending and wear of the anchor lines. The Each accessory is to be marked as follows: attachments to the hull or structure are to be such as to − chain cable grade comply with the requirements of B.1.5. − Test Certificate No. 6. Quality control GL Surveyor’s stamp − Details of the quality control of the manufacturing − month and year of test process of individual anchoring system components are to be submitted. Components shall be designed, All detachable component parts shall be stamped with manufactured, and tested in accordance with recog- a serial number to avoid mixing of components. The nized standards and, if included in the Classification Certificate number may be exchanged against an ab- procedure according to 1.2, also in accordance with breviation or equivalent. If so, this shall be stated in GL Rules. Equipment so tested shall, insofar as practi- the Certificate. cal, be legibly and permanently marked with GL's stamp and delivered with documentation which re- 4.2.5.8 Documentation cords the results of the tests. Concerning details on A complete Inspection and Testing Report in booklet chain cables see 4.2. form shall be provided by the manufacturer for each order. This booklet shall include all dimensional 7. Dynamic positioning systems checks, test and inspection reports, NDT reports, process records as well as any non-conformity, correc- Thrusters used as a sole means of position keeping tive action and repair work. shall provide a level of safety equivalent to that provided for anchoring arrangements, to the satisfaction Each type of accessory shall be covered by separate of GL, see also Chapter 5, Section 6, E. and Chapter 6, Certificates. Section 12, E. All accompanying documents, appendices and reports The Class Notations DP1 to DP3 will be assigned if shall carry reference to the original Certificate num- the offshore unit is equipped with such a system, ber. compare Chapter 1, Section 2, C.2.7. The manufacturer will be responsible for storing, in a Further details are defined in the GL Rules I – Ship safe and retrievable manner, all documentation estab- Technology, Part 1 – Seagoing Ships, Chapter 15 – lished for a period of at least 10 years. Dynamic Positioning Systems.

IV - Part 6 Section 9 B Life-Saving Appliances Chapter 2 GL 2007 Page 9–1

Section 9

Life-Saving Appliances

A. General − IMO: 1974 SOLAS Convention, Resolution 6(48), Chapter III 1. Scope 2.2 GL Rules 1.1 Life-saving appliances shall comply with the − GL Rules VI – Additional Rules and Guidelines, relevant applicable International Regulations accord- Part 2 – Life Saving Appliances, Lifting Appli- ing to 2.1 and/or National Regulations and shall be ances, Accesses, Chapter 6 – Guidelines for Life- suitable for the type and use of the mobile offshore boats and Rescue Boats unit. − GL Rules VI – Additional Rules and Guidelines, 1.2 The design and testing of lifeboats, liferafts Part 2 – Life Saving Appliances, Lifting Appli- and rescue boats with their launching appliances is in ances, Accesses, Chapter 1 – Guidelines for Live- general not within the scope of Classification of mo- Saving Launching Appliances bile offshore units by GL. However, their arrangement in the overall design of the unit and the structure in way of launching appliances taking into account the 3. Emergency warnings and instructions forces from above appliances are always part of Clas- sification. 3.1 Alarm signals For alarm and pubic address system see Chapter 6, 1.3 On special request lifeboats and rescue boats Section 9. and their launching appliances may be approved by GL on the basis of the GL Rules defined in 2.2. 3.2 Operating instructions 1.4 For the requirements for lifejackets, immer- Illustrations and instructions shall be provided on or in sion suits, lifebuoys, radio life-saving appliances, the vicinity of lifeboats and liferafts and their launch- distress flares and line-throwing appliances, etc. see ing controls and shall: B.1.5. These requirements have to follow the regulations defined in 2.1. − illustrate the purpose of controls and the procedures for operating the appliance and give relevant instructions or warnings 2. Rules and regulations − be easily readable under emergency lighting con- 2.1 International Regulations ditions

− International Maritime Organisation (IMO): In- − use symbols in accordance with the recommenda- ternational Convention for the Safety of Life at tions of SOLAS, MODU Code, National Regula- Sea (SOLAS), Chapter III - Life-Saving Appli- tions, etc. ances and Arrangements

− IMO: International Life-Saving Appliance Code (LSA Code), Resolution MSC.48(66) B. Life-Saving Appliances

− IMO: Testing and Evaluation of Life Saving Ap- pliances, Resolution MSC.81(70), as amended by 1. Type and equipment MSC.200(80) 1.1 Life-saving appliances shall be suitable for − IMO: Code for the Construction and Equipment the type and use of the mobile offshore unit. of Mobile Offshore Drilling Units (MODU Code), Chapter 10 1.2 The lifeboats shall meet the requirements of the LSA Code, Chapter IV and the Testing Regula- − IMO: Code of Safety for Special Purpose Ships, tions defined in A.2.1 and shall be of the following Resolution A.534(13), Chapter 8 type: Chapter 2 Section 9 C Life-Saving Appliances IV - Part 6 Page 9–2 GL 2007

− totally enclosed lifeboats launched by falls with 2.2 Self-elevating and column-stabilized units fire protection and self-contained air support system considering LSA Code § 4.6, 4.8 and 4.9, or 2.2.1 Each unit shall carry lifeboats, installed in at least two widely separated locations on different sides − free-fall lifeboats with fire protection and self- or ends of the unit. The arrangement of lifeboats contained air support system considering LSA should provide sufficient capacity to accommodate the Code § 4.7 to 4.9 total number of persons on board if: − all the lifeboats in any one location are lost or − if the unit is considered as “special purpose ship”, rendered unusable, or the reduced requirements according to IMO Reso- lution A.534(13), Chapter 8 may be applied, com- − all the lifeboats on any one side, any end or any pare A.2.1. one corner of the unit are lost or rendered unusable

1.3 The liferafts shall meet the requirements for 2.2.2 In addition liferafts shall be carried of such davit-launched liferafts of the LSA Code, Chapter IV aggregate capacity as will accommodate the total and the Testing Regulations defined in A.2.1. number of persons on board.

1.4 Lifeboats and liferafts shall be fully equipped 2.2.3 In the case of a self-elevating unit where, due as required by the LSA Code, Chapter IV defined in to its size or configuration, lifeboats cannot be located A.2.1. However, for operation in restricted areas items in widely separated locations to satisfy 2.2.1 the Ad- may be dispensed by the Administration of the state of ministration of the state of location or flag may permit flag or location. the aggregate capacity of the lifeboats to accommodate only the total number of persons on board. How- ever, the liferafts should be served by launching appli- 1.5 Personal life saving appliances shall meet the ances. requirements of the LSA Code, Chapter II, of the relevant Administration and of GL considering cli- matic conditions. C. Arrangement of Lifeboats and Liferafts 2. Number and size The number and size of life saving appliances has to 1. Muster and embarkation arrangements be defined according to the regulations mentioned in A.2.1. 1.1 If separate, muster stations shall be provided close to the embarkation stations. Each muster station If not stated otherwise by the responsible Administra- shall have sufficient space to accommodate all persons tion, each manned unit should be provided with at assigned to muster at that station. least the lifeboats and liferafts listed in the following: 1.2 Muster and embarkation stations shall be 2.1 Mobile surface units readily accessible from accommodation and work areas. 2.1.1 Each unit shall carry on each side, one or more lifeboats of such aggregate capacity as will ac- 1.3 Muster and embarkation stations shall be commodate the total number of persons on board. adequately illuminated by emergency lighting.

2.1.2 In addition, a liferaft or liferafts shall be car- 1.4 Alleyways, stairways and exits giving access ried, capable of being launched on either side of a unit to the muster and embarkation stations shall be ade- and of such aggregate capacity as will accommodate quately illuminated by emergency lighting. the total number of persons on board. If the liferaft or liferafts cannot be readily transferred for launching on 1.5 Davit-launched survival craft muster and either side of a unit, the total capacity available on embarkation stations shall be so arranged as to enable each side should be sufficient to accommodate the stretcher cases to be placed in survival craft. total number of persons on board. 1.6 Survival craft embarkation arrangements 2.1.3 If lifeboats and liferafts are stowed in a posi- shall be so designed that: tion which is more than 100 m from the stem or stern, in addition to the liferafts as provided in 2.1.2, a lif- − lifeboats can be boarded by their full complement eraft shall be stowed as far forward or aft, or one as far of persons within 3 minutes from the time the in- forward and another as far as aft, as is reasonable and struction to board is given practicable. Notwithstanding C.3.3 such liferaft or liferafts may be securely fastened so as to permit − lifeboats can be boarded and launched directly manual release. from the stowed position IV - Part 6 Section 9 C Life-Saving Appliances Chapter 2 GL 2007 Page 9–3

− davit-launched liferafts can be boarded and 3.2 Launching stations shall be in such positions launched from a position immediately adjacent to as to ensure safe launching having particular regard to the stowed position or from a position to which the clearance from any exposed propeller, if applicable. liferaft is transferred prior to launching in compli- Launching stations shall not be located near or even ance with 3.3 above working stations which would hinder the launching at certain working conditions. The exact − where necessary, means shall be provided for position shall be agreed with the Administration and bringing the davit-launched liferaft to struc- GL. ture/hull side and holding it alongside so that persons can be safely embarked 3.3 Preparation and handling of survival craft at any one launching station shall not interfere with the 2. Stowage prompt preparation and handling of any other survival craft or rescue boat at any other station. 2.1 Each lifeboat and liferaft shall be stowed:

− so that neither they nor their stowage arrange- 3.4 As far as possible, launching stations shall be ments will interfere with the operation of any other located so that lifeboats and liferafts can be launched lifeboat or liferaft or rescue boat at any other down a straight side of the structure/shell, except for: launching station

− as near the water surface as is safe and practicable − lifeboats and liferafts specially designed for free- fall launching − in a state of continuous readiness so that two crew members can carry out preparations for embarkation and launching in less than 5 minutes − lifeboats and liferafts mounted on structures intended to provide clearance from lower structures − as far as practicable, in a secure and sheltered position and protected from damage by fire and explosion 3.5 Means shall be available to prevent any dis- charge of fluids on to lifeboats or liferafts during 2.2 Lifeboats shall be stowed abandonment. − that they are protected from damage by heavy seas 3.6 During preparation and launching, lifeboats − attached to launching appliances and liferafts, its launching appliance and the area in the water into which they are to be launched shall be 2.3 Liferafts shall be stowed: adequately illuminated by emergency lighting. − as to permit manual release from their securing arrangements 3.7 Launching and recovery arrangements shall be such that the appliance Operator on the unit is able − within reach of the lifting hooks, if liferafts are to observe the survival craft at all times during launch- davit-launched; unless some means of transfer is ing and lifeboats during recovery. provided which is not rendered inoperable within the limits of trim and list prescribed in Section 7 for any damaged condition or by motion or power 3.8 Falls, where used, shall be long enough for failure the survival craft to reach the water with the unit un- − every liferaft, other than those in B.2.1.3, shall be der unfavourable conditions, such as maximum air- stowed with the weak link of its painter perma- gap, lightest transit or operational condition or any nently attached and with a floatfree arrangement damaged condition as described in Section 7. Only complying with the requirements of the regula- one type of release mechanism shall be used for simi- tions defined in A.2. so that the liferaft floats free lar survival craft on board and the opening of the and, if inflatable, inflates automatically when the mechanism shall be possible under load from inside unit sinks. the boat.

3. Launching and recovery arrangements 3.9 In any case of damage defined in the previous Sections, lifeboats with an aggregate capacity of not 3.1 Launching appliances shall be provided for less than 100 % of persons on board shall, in addition all lifeboats and davit-launched liferafts. They shall to meeting all other requirements of launching and meet the requirements defined in Rules and Regula- stowage defined in this Section, be capable of being tion defined in A.2. launched clear of any obstruction. Chapter 2 Section 9 D Life-Saving Appliances IV - Part 6 Page 9–4 GL 2007

D. Rescue Boats − in compliance with C.3, if they are lifeboats

1. Number and requirements 3. Embarkation and launching Each unit shall carry at least one fast rescue boat complying to the requirements of rules and regulations The rescue boat embarkation and launching arrange- defined in A.2. ments shall be such that the rescue boat can be boarded and launched in the shortest possible time. 2. Stowage Launching arrangements shall include a single point Rescue boats shall be stowed: hoist and release mechanism and in other aspects comply with C.3. − in a state of continuous readiness for launching in not more than 5 minutes 4. Recovery − in a position suitable for launching and recovery − so that neither the rescue boats nor their stowage Rapid recovery of rescue boats shall be possible when arrangements will interfere with the operation of loaded with its full complement of at least six persons any lifeboat or raft of another launching station and the relevant equipment. IV - Part 6 Annex A List of Standards, Codes, etc. Quoted Chapter 2 GL 2007 Page A–1

Annex A

List of Standards, Codes, etc. Quoted

Table A.1 List of Standards, Codes, etc. Quoted

IACS Chapter / Section IMO ISO Others UR (D2.2) 2/1 (D2.1) ISM – 1 July 2002 (D1.6)

2/2 (D.4) (MODU) 2/3 (D.5) (MODU) (D.3) 2/4 (D.6) (MODU) (D.9) A.749(18), MSC.75(69), 2/5 A.543(13), MODU

2/6 (D.3) MODU 2/7 (D.4) (D.5) Load Line 66 1704 2/8 (D.3) MODU 9001 SOLAS Res 6(48) LSA MSC.48(66) 2/9 MSC.81(70) MSC.200(80) A.534(13)

Explanation of abbreviations: D1 – D12 Requirements concerning Mobile Offshore Drilling Units, Unified Requirements of IACS, 1996 IACS International Association of Classification Societies IMO International Maritime Organization ISM IMO International Safety Management Procedures, 1 July 2002 ISO International Standardization Organization Load Line International Convention on Load Lines 1966 MODU Code for the Construction and Equipment of Mobile Offshore Drilling Units, issued by IMO SOLAS Safety of Life at Sea, issued by IMO (……) reference not explicitly declared in the text