Section 1 General
Clasification Society 2024 - Version 9.40
Clasifications Register Rules and Regulations - Rules and Regulations for the Classification of Offshore Units, July 2022 - Part 11 Production, Storage and Offloading of Liquefied Gases in Bulk - Chapter 1 General - Section 1 General

Section 1 General

Parent topic: Chapter 1 General

1.1 Guide to the reader

1.1.1 This Part incorporates risk mitigation measures taken and adapted from the revised International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk (2014 IGC Code - International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk). However, if alternative measures have been defined for an installation, in accordance with the operating philosophy or safety philosophy of the installation, these alternative measures may be considered.

1.2 Application and implementation

1.2.1 The purpose of this Part is to provide requirements to ensure the safe operation and inspection/maintenance of ship units engaged in the production, storage and offloading of liquefied gases at a fixed location. Ship units engaged solely in the storage and offloading of liquefied gases at a fixed location are also to comply with this Part, as applicable.

Mobile offshore units using natural gas or methane solely as a fuel are not considered within the scope of this part and are to comply with the Rules and Regulations for the Classification of Ships using Gases or other Low-flashpoint Fuels, July 2022

1.2.2  The requirements in this Part are applicable to hull construction in steel.

1.2.3  This Part considers only the design requirements for the production, storage and offloading of liquefied gases of the unit. Ship units are to comply with Pt 10 Ship Units and other relevant Parts in addition to the requirements of this Part.

1.2.4  The requirements prescribed in this Part are applicable only to liquefied hydrocarbon gases (liquefied natural gas and liquefied petroleum gas), nitrogen and carbon dioxide. The products for which this Part is applicable are listed in Pt 11, Ch 19 Summary of Minimum Requirements. Requirements are not prescribed for products that are considered toxic by the IGC Code. Proposals to produce, store and offload products not listed in Pt 11, Ch 19 Summary of Minimum Requirements are to be individually considered and the arrangements are to be acceptable to the Administration.

1.2.5  Integral tanks, that form a structural part of the hull, for the storage of gas condensate are to comply with Pt 10 Ship Units, see Pt 10, Ch 1, 1.1 Application 1.1.12.

1.2.6  Integral tanks, that form a structural part of the hull, for the bulk storage of liquid chemicals necessary for treatment of the feed gas, e.g. monoethylene glycol (MEG) and amine solvents, are to comply with Pt 10 Ship Units, see Pt 10, Ch 1, 1.1 Application 1.1.13. The structural design of independent tanks for the bulk storage of liquid chemicals is to comply with the requirements of Pt 11, Ch 4 Cargo Containment and Pt 10, Ch 1, 1.1 Application 1.1.13.(a) and Pt 10, Ch 1, 1.1 Application 1.1.13.(c).

1.2.7 Flammable liquids having a flashpoint of 60°C (closed-cup test) or less and the flammable products listed in Pt 11, Ch 19 Summary of Minimum Requirements shall not be carried in tanks located within the protective zones described in Pt 11, Ch 2, 1.4 Location of cargo tanks 1.4.1, within the longitudinal extent of the hold spaces for those tanks.

1.2.8 Where a risk assessment or study of similar intent is utilised within this Part, the results shall also include, but not be limited to, the following as evidence of effectiveness:
  • Description of methodology and standards applied;
  • Potential variation in scenario interpretation or sources of error in the study;
  • Validation of the risk assessment process by an independent and suitable third party;
  • Quality system under which the risk assessment was developed;
  • The source, suitability and validity of data used within the assessment;
  • The knowledge base of persons involved within the assessment;
  • System of distribution of results to relevant parties;
  • Validation of results by an independent and suitable third party.
1.2.9  The risk and consequences of stratification and rollover of liquefied gas in storage tanks are to be considered. Methods to reduce the possibility of stratification are to be considered, e.g.:
  • ability to fill the tank from both the top and bottom;
  • recirculation of tank inventory through jet nozzles or other mixing devices.

Methods to detect stratification are also to be considered.

1.3 Definitions

1.3.1 Except where expressly provided otherwise, the following definitions apply to this Part. Additional definitions are provided in Chapters throughout this Part:
  1. Accommodation spaces are those spaces used for public spaces, corridors, lavatories, cabins, offices, hospitals, cinemas, games and hobby rooms, barber shops, pantries without cooking appliances and similar spaces.
  2. ‘A’ class divisions are divisions as defined in RegulationRegulation 3 - Definitions .3of the SOLAS Convention.
  3. Administration is defined in Pt 1, Ch 2, 2 Definitions, character of classification and class notations. For the purpose of classification, the definition of Administration is to be taken as Clasifications Register (LR).
  4. Boiling point is the temperature at which a product exhibits a vapour pressure equal to the atmospheric pressure.
  5. Breadth, B, in metres, means the maximum breadth of the ship unit, measured amidships to the moulded line of the frame. For the determination of the scantlings for hull construction, the breadth, B, is to be taken as defined in Pt 4, Ch 1, 5 Definitions.
  6. Cargo area is that part of the ship unit which contains the cargo containment system and cargo pump and compressor rooms and includes the deck areas over the full length and breadth of the part of the ship unit over these spaces. Where fitted, the cofferdams, ballast or void spaces at the after end of the aftermost hold space or at the forward end of the forwardmost hold space are excluded from the cargo area.
  7. Cargo containment system is the arrangement for containment of cargo including, where fitted, a primary and secondary barrier, associated insulation and any intervening spaces, and adjacent structure if necessary for the support of these elements. If the secondary barrier is part of the hull structure it may be a boundary of the hold space.
  8. Cargo control room is a space used in the control of cargo handling operations.
  9. Cargoes are products, listed in Pt 11, Ch 19 Summary of Minimum Requirements, that are carried in bulk by ship units subject to the requirements of this Part.
  10. Cargo machinery spaces are the spaces where cargo compressors or pumps, cargo processing units, are located, including those supplying gas fuel to the engine room.
  11. Cargo pumps are pumps used for the transfer of liquid cargo, including main pumps, booster pumps, spray pumps, etc.
  12. Cargo service spaces are spaces within the cargo area used for workshops, lockers and storerooms that are of more than 2 m2 in area.
  13. Cargo tankis the liquid-tight shell designed to be the primary container of the cargo and includes all such containment systems whether or not they are associated with the insulation or/and the secondary barriers.
  14. Closed loop sampling is a cargo sampling system that minimises the escape of cargo vapour to the atmosphere by returning product to the cargo tank during sampling.
  15. Cofferdam is the isolating space between two adjacent steel bulkheads or decks. This space may be a void space or a ballast space.
  16. Control stations are those spaces in which the ship unit’s radio or emergency source of power is located, or where the fire recording or fire control equipment is centralised. This does not include special fire control equipment, which can be most practically located in the cargo area.
  17. Flammability limits are the conditions defining the state of fuel oxidant mixture at which application of an adequately strong external ignition source is only just capable of producing flammability in a given test apparatus.
  18. Flammable products are those identified by an ‘F’ in column ‘f’ in the Table in Pt 11, Ch 19 Summary of Minimum Requirements.
  19. FSS Code is the Fire Safety Systems Code meaning the International Code for Fire Safety Systems as adopted by the Maritime Safety Committee of the Organisation by Resolution MSC.98(73), as amended.
  20. Gas carrier is a cargo ship constructed or adapted and used for the carriage in bulk of any liquefied gas or other products listed in Chapter 19 Summary of Minimum Requirements.
  21. Gas Combustion Unit (GCU) is a means of disposing of excess cargo vapour by thermal oxidation, see also (ax).
  22. Gas consumer is any unit within the vessel using cargo vapour as a fuel.
  23. Hazardous area is an area in which an explosive gas atmosphere is, or may be expected to be present, in quantities that require special precautions for the construction, installation and use of electrical equipment. See Pt 7, Ch 2, 1 Hazardous areas – General, and Pt 7, Ch 2, 2 Classification of hazardous areas and IEC 60092-502 Electrical installations in ships - Part 502: Tankers – Special features for the complete definition of hazardous areas including Classification of Hazardous Areas. When a gas atmosphere is present the following hazards may also be present: toxicity, asphyxiation, corrosiveness, reactivity and low temperature; these hazards shall also be taken into account and additional precautions for the ventilation of spaces and protection of the crew will need to be considered.
  24. Hold space is the space enclosed by the structure of the ship unit in which a cargo containment system is situated.
  25. IBC Code means the International Code for the Construction and Equipment of Ships carrying Dangerous Chemicals in Bulk adopted by the Maritime Safety Committee of the Organisation by Resolution MSC.4(48), as amended.
  26. Independent means that a piping or venting system, for example, is in no way connected to another system and that there are no provisions available for the potential connection to other systems.
  27. Insulation space is the space, which may or may not be an interbarrier space, occupied wholly or in part by insulation.
  28. Interbarrier space is the space between a primary and a secondary barrier, whether or not completely or partially occupied by insulation or other material.
  29. Length, L, in metres, is the length as defined in the International Convention on Load Lines. For the determination of the scantlings for hull construction, the Rule length, L, is to be taken as defined in Pt 4, Ch 1, 5 Definitions.
  30. Machinery spaces are all machinery spaces of category A and all other spaces containing propelling machinery, boilers, fuel oil units, steam and internal combustion engines, generators and major electrical machinery, oil filling stations, refrigerating, stabilising, ventilation and air conditioning machinery, and similar spaces and the trunks to such spaces.
  31. Machinery spaces of category A are those spaces, and trunks to those spaces, which contain:
    1. internal combustion machinery used for main propulsion for self-propelled units; or
    2. internal combustion machinery used for purposes where such machinery has in the aggregate a total power output of not less than 375 kW; or
    3. any oil-fired boiler or fuel oil unit or any oil-fired equipment other than boilers, such as inert gas generators, incinerators, etc.
  32. MARPOL means the International Convention for the Prevention of Pollution from Ships, 1973, as modified by the Protocol of 1978 relating thereto, as amended.
  33. MARVS is the maximum allowable relief valve setting of a cargo tank (gauge pressure).
  34. Non-hazardous area is an area other than a hazardous area.
  35. Fuel oil unit is the equipment used for the preparation of fuel oil for delivery to an oil-fired boiler, or equipment used for the preparation for delivery of heated oil to an internal combustion engine, and includes any oil pressure pumps, filters and heaters dealing with oil at a pressure of more than 0,18 MPa gauge.
  36. Organisation is the International Maritime Organization (IMO).
  37. Permeability of a space means the ratio of the volume within that space which is assumed to be occupied by water to the total volume of that space.
  38. Primary barrier is the inner element designed to contain the cargo when the cargo containment system includes two boundaries.
  39. Products is the collective term used to cover the list of gases indicated in Pt 11, Ch 19 Summary of Minimum Requirements of this Part.
  40. Public spaces are those portions of the accommodation that are used for halls, dining rooms, lounges and similar permanently enclosed spaces.
  41. Recognised Organisation is an Organisation authorised by an Administration in accordance with IMO Resolution A.739(18) Guidelines for the Authorisation of Organisations acting on Behalf of the Administration, to act on their behalf to survey, certificate and determine tonnages as required by SOLAS, MARPOL and the Load Line Conventions.
  42. Recognised standards are applicable international or national Standards acceptable to LR.
  43. Relative density is the ratio of the mass of a volume of a product to the mass of an equal volume of fresh water.
  44. Secondary barrier is the liquid-resisting outer element of a cargo containment system, designed to afford temporary containment of any envisaged leakage of liquid cargo through the primary barrier and to prevent the lowering of the temperature of the structure of the ship unit to an unsafe level. Types of secondary barrier are more fully defined in Pt 11, Ch 4 Cargo Containment.
  45. Separate systems are those cargo piping and vent systems that are not permanently connected to each other.
  46. Service spaces are those used for galleys, pantries containing cooking appliances, lockers, mail and specie rooms, storerooms, workshops other than those forming part of the machinery spaces and similar spaces and trunks to such spaces.
  47. SOLAS Convention means the International Convention for the Safety of Life at Sea, 1974, as amended.
  48. Tank cover is the protective structure intended either to protect the cargo containment system against damage where it protrudes through the weather deck or to ensure the continuity and integrity of the deck structure.
  49. Tank dome is the upward extension of a portion of a cargo tank. In the case of below deck cargo containment systems, the tank dome protrudes through the weather deck or through a tank cover.
  50. Thermal oxidation method means a system where the boil-off vapours are utilised as fuel for shipboard use or as a waste heat system, subject to the provisions of Pt 11, Ch 16 Use of Cargo as Fuel or a system not using the gas as fuel complying with this Part.
  51. Turret compartments are those spaces and trunks that contain equipment and machinery for retrieval and release of the disconnectable turret mooring system, high pressure hydraulic operating systems, fire protection arrangements and cargo transfer valves.
  52. Vapour pressure is the equilibrium pressure of the saturated vapour above the liquid, expressed in MPa absolute at a specified temperature.
  53. Design vapour pressure ‘P 0’ is the maximum gauge pressure, at the top of the tank, to be used in the design of the tank.
  54. Void space is an enclosed space in the cargo area external to a cargo containment system, other than a hold space, ballast space, fuel oil tank, cargo pumps or compressor room, or any space in normal use by personnel.

1.4 Alternative arrangements

1.4.1  Alternative arrangements or fittings which are considered to be equivalent to those specified in these Rules will be accepted. Arrangements or systems incorporating features not provided for in these Rules will be specially considered.

1.5 Survey requirements

1.5.1  Ship units engaged in the production, storage and offloading of liquefied gases are to comply with the survey requirements given in Pt 1, Ch 3 Periodical Survey Regulations and other relevant Parts of the Rules.

1.6 Class notations and descriptive notes

1.6.1  The class notations and descriptive notes applicable to units classed in accordance with these Rules are to be in accordance with Pt 1, Ch 2 Classification Regulations and Pt 3, Ch 3, 1 General, to which reference should be made.

1.6.2  Where the requirements of this Part are complied with, additional class notations in respect of the following items will be assigned as appropriate:
  • Type of tanks.
  • Name(s) of gas(es).
  • Maximum vapour pressure.
  • Minimum and (where necessary) maximum cargo temperature.
  • Design ambient temperatures.

1.6.3  The class notation ✠ Lloyd’s RMC(LG) is mandatory when reliquefaction and/or refrigeration equipment is fitted. The equipment is to be constructed, installed and tested in accordance with the requirements of Pt 11, Ch 7 Cargo Pressure/Temperature Control and elsewhere in these Rules. The minimum temperature for which the installation is suitable will be that given in the main notation unless otherwise qualified.

SDA, FDA and CM notations are already defined within Pt 1 Regulations and Pt 10 Ship Units.

1.7 Information and plans

1.7.1  In addition to the plans required by the relevant Parts of these Rules, the following information and plans are to be submitted, where applicable:
  • Full particulars of the intended cargo, or cargoes, including maximum vapour pressures, minimum and (where necessary) maximum liquid temperature and other relevant design conditions.
  • General arrangement showing location of cargo tanks and the relative location of fuel oil, water ballast and other tanks.
  • Openings in main deck.
  • Location of void spaces and dangerous zones: openings and access arrangements.
  • Details of hull structure in way of cargo tanks, including support arrangements for tanks and associated pipes and fittings, deck sealing arrangements, etc.
  • Distribution of quality and grade of steel, supported by calculations of the determined hull steel temperature. The steel grade and temperature in regions where cold spots are likely to occur (e.g. pump supports and where pipes pass through the deck) are also to be indicated.
  • Scantlings, materials, and arrangements of the cargo containment system, including primary and (where fitted) secondary barriers, keying and support arrangements, and attachments of fittings, piping, etc.
  • Ladders, suction supports and towers inside cargo tanks (arrangements, materials and loadings).
  • Tank dome plans.
  • End coamings around dome.
  • Particulars of filling, discharging, venting, relieving and inerting arrangements.
  • Details of test procedures.
  • Temperature control arrangements.
  • Such information and data as may be required to enable analysis of the hull and containment system structure to be carried out by direct calculation methods.
  • Details of personnel protection equipment to be included on the safety plan as applicable to the ship unit.
  • Assumptions and details of direct calculations procedures used in the structural analysis of the hull.
  • Where horizontal and vertical girders are used to support the bulkhead, the bulkhead scantlings may be determined using direct calculation procedures. The assumptions made and the calculations are to be submitted.

Additional requirements for information and plans may be found in the appropriate Chapters of this Part.

1.7.2  The following plans and particulars for Type C independent tanks are to be submitted for approval before construction is commenced:
  • Nature of cargoes, together with maximum vapour pressures and minimum liquid temperature for which the pressure vessels are to be approved, and proposed hydraulic test pressure.
  • Particulars of materials proposed for the construction of the vessels.
  • General arrangement plan showing location of pressure vessels in the ship unit.
  • Plans of pressure vessels showing attachments, openings, dimensions, details of welded joints and particulars of proposed stress relief heat treatment.
  • Plans of seating, securing arrangements and deck sealing arrangements.
  • Plans showing arrangement of mountings, level gauges and number, type and size of safety valves.
  • Details of the arrangements proposed to ensure that the tank or cargo temperature cannot be lowered below the minimum cargo design temperature as defined in Pt 11, Ch 4, 1.1 Definitions 1.1.3.
  • Plans showing filling, discharging, venting and inerting pipe arrangements, together with particulars of the intended cargo, maximum vapour pressure and minimum liquid temperature.
  • Details of calculations and/or model tests are required for the assessment of the tank boundaries with partial filling of tanks.
  • Allowable stresses of any materials not covered by Pt 11, Ch 6 Materials of Construction and Quality Control required by Pt 11, Ch 4, 4.3 Design conditions 4.3.2.(e).
  • Details verifying compliance with the periodical examination of the secondary barrier required by Pt 11, Ch 4, 2.4 Design of secondary barriers 2.4.2.(d) if applicable.
  • Details of the heating system of the hull structure required by Pt 11, Ch 4, 5.1 Materials 5.1.2.(e) if fitted.
  • Specification and plans of the containment system are to be submitted for approval. Plans are to include:
    • Details of insulation material and, if used, any adhesive, sealers, coatings or similar products.
    • Details of insulation arrangement.
    • Internal bearers or steelwork.
    • Tank supports, chocks, etc.
    • Hatch trunks.
    • Attachment and support of insulation and linings.
    • Data and information to enable a heat leakage calculation to be carried out to assess the capacity of the arrangements provided to deal with boil-off, including:
      • Thermal conductivity of insulation between upper ambient and design temperatures.
  • The proposed procedure for fabrication, storage, handling, erection, quality control and control against harmful exposure to sunlight of insulation materials.
  • Calculations and/or analysis of strength of insulation where it is subjected to high mechanical or thermal loads.
  • Fatigue and crack propagation properties for insulation in membrane systems are also to be submitted.
  • Specifications of the containment system items are to include both those applicable to initial approval of the material, and those applicable to subsequent delivery of batches of material.

Additional requirements for information and plans may be found in the appropriate Chapters of this Part.

1.7.3  The following plans and particulars for Membrane tanks are to be submitted for approval before construction is commenced:
  • Recovery Duration (as specified in Pt 11, Ch 4, 1.1 Definitions 1.1.9), nature of cargoes, together with maximum vapour pressures and minimum liquid temperature for which the membrane tanks are to be approved.
  • Particulars of materials proposed for the construction of the tanks.
  • General arrangement plan showing location of membrane tanks in the ship unit and location of relieving devices per tank.
  • Plans of membrane tanks showing general construction arrangements and installation methodology.
  • Plans of membrane tanks showing insulation panels distribution, levelling and fastening arrangements.
  • Plans of membrane tanks showing openings, dimensions, and details of welded joints.
  • Details of the arrangements proposed to ensure that the tank or cargo temperature cannot be lowered below the minimum cargo design temperature as defined in Pt 11, Ch 4, 1.1 Definitions 1.1.3.
  • Plans showing filling, discharging, venting, inerting and draining pipe arrangements, together with particulars of the intended cargo, maximum vapour pressure and minimum liquid temperature.
  • Details of calculations and/or model tests, when partial filling of tanks are considered, for the assessment of the containment system integrity.
  • Allowable stresses of any materials not covered by Pt 11, Ch 6 Materials of Construction and Quality Control required by Pt 11, Ch 4, 4.3 Design conditions 4.3.2.(e).
  • Details verifying compliance with the periodical examination or NDT of the secondary barrier required for approval by Pt 11, Ch 4, 2.4 Design of secondary barriers 2.4.2.(d) if applicable.
  • Details of the heating system of the hull structure required by Pt 11, Ch 4, 5.1 Materials 5.1.2.(e) if fitted.
  • Specification and plans for all the containment system components are to be submitted for approval. These plans and specifications are to include:
    • Details of insulation material and, if used, any adhesive, sealers, fillers, coatings or similar products. Properties documented to include:
      • density,
      • elastic modulus and Poisson’s ratio,
      • porosity,
      • thixotropic nature,
      • thermal conductivity,
      • thermal expansion/contraction,
      • and any thermal variation of material properties required by the system.
    • Details of insulation arrangement, including installation, welding, gluing, joining procedures and other mechanical means not already covered.
    • Inner hull anchoring flat bars, including definition of surface and levelling quality required.
    • Repair procedures defining imperfection, defects, their allowable limits and subsequent repair processes.
    • Document showing clear system for identification and traceability of parts and components in order to easily act on failure trends.
    • Attachment and support of insulation and linings including bearing limitations in terms of movement, discontinuous connections, angles, steps and spaces.
    • Data and information to enable a heat leakage calculation to be carried out to assess the capacity of the arrangements provided to deal with boil-off, including:
      • Thermal conductivity of insulation between upper ambient and design temperatures.
    • Details of the means of on-site inspection and repair procedures and details of any loads which will be imparted upon the membranes as a result of the on-site inspection and repair procedures. These details need to include:
      • The method to be used.
      • Any loads which will be imparted upon the membranes.
      • The acceptance criteria.
      • The weather conditions for which it will be permitted to undertake inspection and repair operations.
      • The form of record to be made.

      Entry into tank space for inspection purposes should be avoided where possible.

      The testing and inspection should be commensurate with assumptions made in the design of the containment system, see Pt 11, Ch 4, 4.3 Design conditions 4.3.3.

    • Details of on-site inspection to be carried out following an exceptional severe event (of similar magnitude of a 10 000 years return period event as per Pt 11, Ch 4, 2.1 Functional requirements 2.1.5.(c)).
    • Details of proposal for tank preservation in case the intervening period between the cargo tank completion and the first cool down is expected to be significant.
  • The proposed procedure for fabrication, storage, handling, erection, quality control and control against harmful exposure to sunlight of insulation materials.
  • Testing results and/or calculations and/or analysis of strength of insulation demonstrating capability to withstand high mechanical and thermal loads.
  • Site specific calculations and analyses to include:
    • Sloshing and liquid motion analyses justifying the proposed filling level ranges.
    • Fatigue and crack propagation and tearing properties of insulation system components.
    • Specifications of the containment system items are to include both those applicable to initial approval of the material, and those applicable to subsequent delivery of batches of material.

Additional requirements for information and plans may be found in the appropriate Chapters of this Part.

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