Section 9 Ships for liquefied gases

9.1.1 The requirements of Pt 1, Ch 3, 2 Annual Surveys - Hull and machinery requirements to Pt 1, Ch 3, 7 Special Survey - Oil tankers (including ore/oil ships and ore/bulk/oil ships) - Hull requirements are to be complied with, as applicable.

9.1.2 Prior to the inspection of cargo tanks, surrounding spaces, associated piping, fittings and equipment, etc. the respective items are to be cleaned and thoroughly cleared of gas. Every precaution is to be taken to ensure safety during inspection.

9.1.3 The following documentation, as applicable, is to be available on board the ship:

1. Relevant instruction and information material such as cargo handling plans, filling limit information, cooling down procedures, etc.

2. A copy of the Rules and Regulations for the Construction and Classification of Ships for the Carriage of Liquefied Gases in Bulk, July 2022.

3. Test records of secondary barrier.

4. Loading and stability information, including damage stability.

5. A document specifying the maximum allowable loading limits for each cargo tank and product, at each applicable loading temperature and maximum reference temperature approved by the Administration. The pressures at which the pressure relief valves (PRVs) have been set shall also be stated in the document.
6. The cargo system operation manuals approved by the Administration.

9.1.4 For requirements of Special Survey for electrical equipment, see Pt 1, Ch 3, 14 Electrical equipment.

9.1.5 The survey requirements of Pt 1, Ch 3, 9.2 Annual Surveys − Basic requirements to Pt 1, Ch 3, 9.11 Special Survey III and Special Surveys thereafter (ships 15 years old and over) shall additionally be applied to gas fuel tanks and their associated systems, as applicable.

9.2.1 The Annual Survey is preferably to be carried out during a loading or discharging operation. Access to cargo tanks or inerted hold spaces, necessitating gasfreeing/ aerating will normally not be necessary unless required by the Regulations.

9.2.2 The ship's log and operational records for the cargo containment system covering the period from the previous survey are to be examined. Any malfunction of the system entered in the log is to be investigated, the cause ascertained, and that part of the system at fault is to be found or placed in good order.

9.2.3 Instrumentation and safety systems are to be surveyed as follows:

1. The instrumentation of the cargo installations with regard to pressure, temperature and liquid level is to be verified in good working order by one or more of the following methods:

   1. Visual external examination.

   2. Comparing of read outs from different indicators.

   3. Consideration of read outs with regard to the actual cargo and/or actual conditions.

   4. Examination of maintenance records with reference to cargo plant instrumentation maintenance manual.

   5. Verification of calibration status of the measuring instruments.

2. The low level, high level, and overfill alarms are to be examined and tested to ascertain that they are in working order.

3. The alarms associated with the following are to be tested as applicable:

   1. Cargo tank high and low pressure.

   2. Cargo tank temperature.

   3. Cargo hold pressure.

   4. Interbarrier space pressure.

   5. Inner hull temperature.

   6. Secondary barrier temperature.

   7. Cargo Hold or Interbarrier bilge level detection.

4. Control devices for the cargo containment systems and cargo handling equipment, together with any associated shutdown and/or interlock, are to be checked under simulated working conditions and, if necessary, recalibrated. Such safety systems include but are not limited to:

   1. Cargo tank overfill protection including cargo pump, compressor and other cargo machinery automatic shutdown.

   2. Cargo pump, compressor and other cargo machinery shutdown on low cargo tank pressure or cargo tank and interbarrier/hold space differential pressure.

   3. Cargo pump automatic shutdown on low level or current;

5. The emergency shutdown system is to be tested, without flow in the pipe lines, to verify that the system will cause the cargo pumps, compressors and other cargo machinery, as applicable, to stop.

6. Consideration will be given to the acceptance of simulated tests, provided that they are carried out at the cargo temperature, or comprehensive maintenance records, including details of tests held, in accordance with the cargo plant instrumentation maintenance manual.

9.2.4 Cargo gas leakage detection systems are to be examined and tested to ascertain that they are in working order and calibrated using sample gas.

9.2.5 Inert gas/dry air installations including the means for prevention of backflow of cargo vapour to gas-safe spaces are to be verified as being in satisfactory operating condition.

9.2.6 Ventilation systems and air locks in working spaces are to be checked for satisfactory operation.

9.2.7 Cargo pipeline, valves and fittings are to be generally examined, with special reference to expansion bellows, supports and vapour seals on insulated pipes. It is to be verified that all accessible cargo piping systems are electrically bonded to the hull.

9.2.8 Portable and/or fixed drip trays, or insulation for deck protection in the event of cargo leakage, are to be examined for condition.

9.2.9 The means for accomplishing gas tightness of the wheelhouse doors and windows is to be examined. All windows and side-scuttles within the area required to be of the fixed type (non-opening) are to be examined for gas tightness. The closing devices for all air intakes and openings into accommodation spaces, service spaces, machinery spaces, control stations and approved openings in superstructures and deckhouses facing the cargo area or bow and stern loading/unloading arrangements are to be examined. For ships carrying toxic gases such devices should be capable of being operated from inside the space.

9.2.10 Venting systems, including protection screens if provided, for the cargo tanks, inter-barrier spaces and hold spaces are to be visually examined externally. It is to be verified that the cargo tank relief valves are sealed and that the certificate for the relief valves opening/closing pressures is on board the ship.

9.2.11 Mechanical ventilation fans in gas hazardous zones and spaces are to be visually examined. Adequate spare parts should be carried for each type of fan installed.

9.2.12 Electrical equipment, cables and supports in gas hazardous zones and spaces shall be examined as far as practicable. Alarms and safety systems associated with pressurised lighting systems and any safety device associated with nonsafe type electrical equipment that is protected by air-locks are to be verified.

9.2.13 Heating arrangements, if fitted, for cofferdams and other spaces shall be verified in good working order.

9.2.14 All accessible gas-tight bulkhead penetrations including gas-tight shaft sealings are to be visually examined.

9.2.15 The sealing arrangements for tanks or tank domes penetrating decks or tank covers are to be externally examined.

9.2.16 The survey is to consist of an examination for the purpose of ensuring, as far as practicable, that the hull and piping are maintained in a satisfactory condition.

1. The examination of the hull and piping is to include the following:

   • hull plating and closing appliances as far as can be seen
   • watertight penetrations as far as practicable
   • weather decks
   • flame screens on vents to all bunker tanks
   • bunker and vent piping systems

2. The examination of the cargo pump rooms and compressor rooms and, as far as practicable, pipe tunnels if fitted is to include the following:

   • all pump room and compressor room bulkheads for signs of leakage or fractures and, in particular, the sealing arrangements of all penetrations of pump room and compressor room bulkheads
   • condition of all piping systems (for cargo piping systems, see Pt 1, Ch 3, 9.2 Annual Surveys − Basic requirements 9.2.7).

9.2.17 The Surveyor is to carry out an examination and thickness measurement of structure identified at the previous Special Survey or Intermediate Survey as having substantial corrosion, as defined in Pt 1, Ch 3, 1.5 Definitions. The extent of thickness measurements is to be increased in accordance with Table 3.9.4 Thickness measurement - Ships for liquefied gases - Structural areas with substantial corrosion to determine the full extent of the corrosion pattern. The survey will not be considered complete until these additional thickness measurements have been carried out.

9.3.1 Where reliquefaction or refrigeration equipment for cargo temperature and pressure control is fitted, the following are to be examined, so far as practicable:

1. The machinery under working conditions.

2. The shells of all pressure vessels in the system, externally. Insulation need not be removed for this examination, but any deterioration of insulation or evidence of dampness which could lead to external corrosion of the vessels or their connections, is to be investigated.

3. Primary refrigerant gas and liquid pipes, cargo vapour and liquid condensate pipes and condenser cooling water pipes. Insulation need not be removed, but any deterioration or evidence of dampness is to be investigated.

4. The reliquefaction/refrigeration plant spare gear.

9.3.2 Reference should be made to the Special Survey requirements for guidance on Continuous Survey arrangements.

9.4.1 The following components are to be generally examined externally. If insulation is fitted, this need not be removed, but any deterioration of insulation, or evidence of dampness which could lead to external corrosion of the vessels or their connections, is to be investigated:

1. Heat exchangers and pressure vessels for use with gas fuel burning in boilers or machinery.

2. Cargo heaters, vaporisers, masthead heaters and other miscellaneous pressure vessels.

9.4.2 Controls and interlocks are to be checked.

9.4.3 Alarm systems are to be checked to ascertain that they are in working order.

9.4.4 Exhaust fans and/or pressurising system for gas trunking are to be tested.

9.4.5 Ventilation systems are to be checked for satisfactory operation, if separate from the cargo venting arrangements.

9.4.6 Fuel tanks and relief valves are to be externally examined, where applicable.

9.5.1 Where the insulation arrangement is such that the insulation cannot be examined, the surrounding structures of wing tanks, double bottom tanks and cofferdams are to be examined for cold spots, prior to the survey. This examination is to be held at a convenient cargo discharge operation with the cargo tanks loaded at approximately the minimum notation temperature.

9.5.2 On application by the Owner, consideration will be given to the cold spot examination, where applicable, being carried out by the ship's staff.

9.5.3 When tests are required after repairs, independent cargo tanks, other than independent tanks type C, are to be tested by hydraulic or hydropneumatic means as appropriate. Test heads and pressures should be as defined in Part E - Tank Types of the Rules and Regulations for the Construction and Classification of Ships for the Carriage of Liquefied Gases in Bulk. Cargo tanks of the membrane or semi-membrane type are to be tested by means of a detectable gas in the inter-barrier spaces and discolouring paint on the weld seams of the cargo tanks wall, or other suitable means. Independent cargo tanks of type C are to be tested hydraulically at 1,25 times the approved maximum vapour pressure.

9.5.4 For membrane containment systems, the Surveyor is to receive confirmation from the Master that the nitrogen control system for insulation and inter-barrier spaces is operating normally.

9.6.1 The Intermediate Survey intends to supplement the Annual Survey by testing cargo handling installations with related automatic control, alarm and safety systems for correct functioning. The Intermediate Survey is preferably to be carried out with the ship in a gas-free condition. The extent of the testing required for the Intermediate Survey will normally be such that the survey cannot be carried out during a loading or discharging operation.

9.6.2 In addition to the requirements for Annual Survey and the requirements of Pt 1, Ch 3, 3.3 Intermediate Surveys 3.3.1 to Pt 1, Ch 3, 3.3 Intermediate Surveys 3.3.9, the following are to be dealt with as applicable:

1. Examination of means for draining the vent piping system.

2. Verification that pipelines and cargo tanks are electrically bonded to the hull.

3. Verification that the heating arrangements, if any, for steel structures are satisfactory.

4. Where required by the manufacturer's maintenance instructions, cargo tank and inter-barrier space pressure and vacuum relief valve settings are to be checked and adjusted as required. Cargo tank pressure relief valve harbour settings are also to be checked, if applicable. Cargo tank pressure relief valves are to lift at a pressure not more than the percentage given below, above the maximum vapour pressure for which the tanks have been approved.

   • For 0 to 0,15 MPa, 10 per cent.
   • For 0,15 to 0,3 MPa, 6 per cent.
   • For pressures exceeding 0,3 MPa, 3 per cent.
   • Valves may be removed from the tanks for the purpose of checking.

5. A General Examination within the zones and spaces deemed as hazardous, such as cargo compressor rooms and spaces adjacent to and zones above cargo areas, for defective and non-certified safe-type electrical equipment, improperly installed, defective and dead wiring. An electrical insulation resistance test of the circuits terminating in, or passing through the hazardous zones and spaces, is to be carried out. If the ship is not in a gas free condition the results of previously recorded test readings may be accepted.

9.6.3 For ships over 5 years of age and up to 10 years of age, an overall survey of representative ballast tanks is to be carried out. Where a hard protective coating is found to be in POOR condition, as defined in Pt 1, Ch 3, 1.5 Definitions, where a soft or semi-hard coating has been applied or where a protective coating was not applied from the time of construction, the survey is to be extended to other ballast tanks of the same type.

9.6.4 For ships over 10 years of age, an overall survey of all ballast tanks is to be carried out.

1. If such examinations reveal no visible structural defects, the examination may be limited to verification that the corrosion prevention system remains in GOOD or FAIR condition.

2. The condition of the corrosion prevention system identified during the Survey may result in the tanks being subject to further examination at Annual Surveys, in accordance with Pt 1, Ch 3, 2.2 Annual Surveys 2.2.32. For independent double bottom ballast tanks, the examination at Annual Surveys will be at the discretion of the Surveyor.

9.6.5 The minimum requirements for Close-up Survey are given in Table 3.9.1 Ships for liquefied gases - Intermediate Surveys.

9.7.1 The requirements of Pt 1, Ch 3, 9.1 General to Pt 1, Ch 3, 9.6 Intermediate Surveys are to be complied with.

9.7.2 The requirements for Close-up Survey and thickness measurement are given in Pt 1, Ch 3, 9.12 Close-up Survey and Pt 1, Ch 3, 9.13 Thickness measurement.

9.7.3 All cargo tanks are to be examined internally, also externally so far as practicable, particular attention being paid to the plating in way of supports of securing arrangements, tower structures, seatings and pipe connections, also to sealing arrangements in way of the deck penetrations. Provided that the structural examination is satisfactory, that the gas leakage monitoring systems have been found to be operating satisfactorily and that the voyage records have not shown any abnormal operation, cargo tanks do not require to be hydraulically tested. The primary membranes of 'Gas Transport' design should be examined with the primary insulation space under a vacuum of at least -500 mbar gauge. For 'Moss Type' LNG cargo tanks, the Structural Transition Joints (STJ) are to be examined at the port, starboard, forward and aft locations. Insulation is to be removed as required. Non-destructive testing may be required where considered necessary. For membrane containment systems with corrugated primary barriers, in view of the sloshing loads experienced in service, measurements should, if required, be taken inside the cargo tanks of deformations of the primary barrier corrugations in order to assess the condition of the containment system in accordance with the system designer’s procedures as approved by LR.

9.7.4 The non-destructive testing of cargo tanks is to be carried out as follows:

1. Non-destructive testing is to supplement cargo tank inspection with special attention to be given to the integrity of the main structural members, tank shell and highly stressed parts, including welded connections as deemed necessary by the Surveyor. The following items are, inter alia, considered as highly stressed parts:

   1. Cargo tanks supports and anti-rolling/antipitching devices;

   2. Web frames or stiffening rings;

   3. Swash bulkhead boundaries;

   4. Dome and stump connections to tank shell;

   5. Foundations for pumps, towers, ladders, etc.;

   6. Pipe connections.

2. For independent tanks of Type B, the extent of non-destructive testing shall be as given in the programme specially prepared for the cargo tank design.

3. Independent cargo tanks of Type C are to be subjected to non-destructive testing of the plating in way of supports and also at selected lengths of welds. Where such testing raises doubt as to the structural integrity, a hydraulic test should be carried out at 1,25 times the approved maximum vapour pressure. Alternatively, consideration will be given to pneumatic testing under special circumstances, provided full details are submitted for approval.

4. At each alternate Special Survey (i.e. SSII, SSIV and so on), all independent cargo tanks of Type C are to be either:

   1. Hydraulically or hydro-pneumatically tested to 1,25 times MARVS, followed by non-destructive testing in accordance with paragraph Pt 1, Ch 3, 9.7 Special Survey I (ships five years old) − General requirements 9.7.4 above, or,

   2. Subjected to a thorough, planned, non-destructive testing. This testing is to be carried out in accordance with a programme specially prepared for the tank design. If a special programme does not exist, the following applies:

• cargo tank supports and anti-rolling/anti-pitching devices;
• stiffening rings;
• Y-connections between tank shell and a longitudinal bulkhead of bi-lobe tanks;
• swash bulkhead boundaries;
• dome and sump connections to the tank shell;
• foundations for pumps, towers, ladders etc.;
• pipe connections.

At least 10 per cent of the length of the welded connections in each of the above mentioned areas is to be tested. This testing is to be carried out internally and externally as applicable. Insulation is to be removed as necessary for the required non-destructive testing.

9.7.5 Deck mounted cargo storage tanks are to be examined in the same manner as main cargo tanks.

9.7.6 For membrane containment systems, a tightness test of the primary and secondary barrier shall be carried out in accordance with the system designer's procedures and acceptance criteria as approved by LR. Low differential pressure tests may be used for monitoring the cargo containment system performance, but are not considered an acceptable test for the tightness of the secondary barrier. For membrane containment systems with glued secondary barriers, if the designer’s threshold values are exceeded, an investigation is to be undertaken and additional testing such as thermographic or acoustic emissions testing should be carried out.

9.7.7 Where a cargo tank or the hull structure is insulated and the insulation is accessible, the insulation should be examined externally, together with any vapour or protective barrier, and sections removed for examination, if considered necessary by the Surveyor. Special attention should be given to insulation in way of chocks, supports and keys. Portions of the insulation are also to be removed, if required by the Surveyor, to enable the condition of the plating to be ascertained. Where the insulation is not accessible, see Pt 1, Ch 3, 9.5 Annual Surveys − Cargo containment systems 9.5.1.

9.7.8 Cargo tank internal pipes and fittings are to be examined, and all valves and cocks in direct communication with the interiors of the tanks are to be opened out for inspection and the connection pipes are to be examined internally, so far as practicable.

9.7.9 Relief valves are to be surveyed as follows:

1. The pressure relief valves for the cargo tanks are to be opened for examination, adjusted, function tested, and sealed. If the cargo tanks are equipped with relief valves with non-metallic membranes in the main or pilot valves, such non-metallic membranes are to be replaced.

2. Pressure relief valves are subsequently to be adjusted to lift at a pressure in accordance with Pt 1, Ch 3, 9.6 Intermediate Surveys 9.6.2.(d). Relief valve harbour settings are to be checked, if applicable. Valves may be removed from the shell for the purpose of making this adjustment under pressure of air or other suitable gas.

3. Where a proper record of continuous overhaul and retesting of individually identifiable relief valves is maintained, consideration will be given to acceptance on the basis of opening, internal examination, and testing of a representative sampling of valves, including each size and type of liquefied gas or vapour relief valve in use, provided there is logbook evidence that the remaining valves have been overhauled and tested since crediting of the previous Special Survey.

4. Relief valves on cargo gas and liquid pipelines are to have their pressure settings checked. The valves may be removed from the pipelines for this purpose. At the Surveyor's discretion a sample of each size and type of valve may be opened for examination and testing.

9.7.10 All cargo pumps, cargo booster pumps and cargo vapour pumps are to be opened out for examination. If requested by the Owner, these items may be examined on a Continuous Survey basis, provided the interval between examination of each item does not exceed five years. Pumping systems for inter-barrier spaces are to be checked and verified to be in good working order.

9.7.11 Piping for cargo and process systems including valves, actuators and compensators are to be opened for examination. Insulation may need to be removed, as deemed necessary, to ascertain the condition of the piping. If any doubt exists regarding the integrity of the piping based upon visual examination then, where deemed necessary by the Surveyor, a pressure test at 1,25 times MARVS for the pipeline is to be carried out. The complete piping systems are to be tested for leaks after re-assembly.

9.7.12 Equipment for the production of inert gas is to be examined and shown to be operating satisfactorily within the gas specification limits. Pipelines, valves, etc. for the distribution of the inert gas are to be generally examined. Pressure vessels for the storage of inert gas are to be examined internally and externally and the securing arrangements are to be specially examined. Pressure relief valves are to be demonstrated to be in good working order. Liquid nitrogen storage vessels are to be examined, so far as practicable, and all control equipment, alarms and safety devices are to be verified as operational.

9.7.13 Gastight bulkhead shaft seals are to be opened out so that the sealing arrangements may be checked.

9.7.14 Sea connections associated with the cargo handling equipment are to be opened out when the ship is in dry-dock.

9.7.15 The arrangements for discharging the cargo overboard in an emergency are to be checked.

9.8.1 Each reciprocating compressor is to be opened out. Cylinder bores, pistons, piston rods, connecting rods, valves and seats, glands, relief devices, suction filters and lubricating arrangements are to be examined. Crankshafts are to be examined, but crankcase glands and the lower half of main bearings need not be exposed if the Surveyor is satisfied with the alignment and wear.

9.8.2 Where other than reciprocating-type compressors are fitted, or where there is a program of replacement instead of surveys on board, alternative survey arrangements will be considered. Each case will be given individual consideration.

9.8.3 The water end covers of condensers are to be removed for examination of the tubes, tubeplates and covers.

9.8.4 Refrigerant condenser cooling water pumps, including standby pump(s) which may be used on other services, are to be opened out for examination.

9.8.5 Where a pressure vessel is insulated, sufficient insulation is to be removed, especially in way of connections and supports, to enable the vessel's condition to be ascertained.

9.8.6 Insulated pipes are to have sufficient insulation removed to enable their condition to be ascertained. Vapour seals are to be specially examined for their condition.

9.8.7 The Surveyor is to satisfy himself that all pressure relief valves and/or safety discs throughout the system are in good order. No attempt, however, is to be made to test primary refrigerant pressure relief valves on board ship.

9.8.8 The items covered by Pt 1, Ch 3, 9.8 Special Survey I (ships five years old) − Reliquefaction/refrigeration equipment 9.8.1 to Pt 1, Ch 3, 9.8 Special Survey I (ships five years old) − Reliquefaction/refrigeration equipment 9.8.4 may, at the request of the Owner, be examined on a Continuous Survey basis provided the interval between examination of each item does not exceed five years.

9.9.1 Where gas fuel is used for main propulsion purposes, the associated compressors and heat exchangers are to be opened out and examined as for reliquefaction/refrigeration equipment. The glycol/water or steam side of the heaters is to be hydraulically tested to 1,5 times the design pressure.

9.9.2 Gas fuel pipe trunks or casings are to be generally examined and the exhaust or inerting arrangements for these trunks are to be verified.

9.9.3 All alarms associated with the gas fuel burning systems are to be verified.

9.10.1 The requirements of Pt 1, Ch 3, 9.1 General to Pt 1, Ch 3, 9.9 Special Survey I (ships five years old) - Gas fuel burning equipment are to be complied with.

9.10.2 Water cooled condensers in which the primary refrigerant is in contact with the shell are to have the end covers removed and the shell pneumatically tested to a pressure equal to the designed working pressure.

9.10.3 All other pressure vessels in the reliquefaction/refrigeration system, gas fuel burning system and other handling systems are to be pneumatically tested to a pressure equal to the designed working pressure.

9.10.4 The requirements for Close-up Survey and thickness measurement are given in Pt 1, Ch 3, 9.12 Close-up Survey and Pt 1, Ch 3, 9.13 Thickness measurement.

9.11.1 The requirements of Pt 1, Ch 3, 9.1 General toPt 1, Ch 3, 9.10 Special Survey II and Special Surveys thereafter (ships 10 years old and over) are to be complied with.

9.11.2 For independent tanks of Type B, the Owner is to submit proposals for the extent of non-destructive testing of the cargo tanks well in advance of the Special Survey.

9.12.1 The minimum requirements for Close-up Survey are given in Table 3.9.2 Minimum requirements for Close-up Survey - Ships for liquefied gases.

9.12.2 The Surveyor may extend the Close-up Survey, if deemed necessary, taking into account the maintenance of the tanks under survey, the condition of the corrosion prevention system and the structural arrangements or details which have suffered defects in similar spaces or on similar ships and tanks having structures approved with reduced scantlings.

9.12.3 For areas in tanks where coatings are found to be in GOOD condition, as defined in Pt 1, Ch 3, 1.5 Definitions, the extent of Close-up Survey may be specially considered.

9.13.1 The minimum requirements for thickness measurement are given in Table 3.9.3 Minimum requirements for thickness measurement - Ships for liquefied gases.

9.13.2 In areas where substantial corrosion, as defined inPt 1, Ch 3, 1.5 Definitions, has been noted, then additional measurements are to be carried out in accordance with Table 3.9.4 Thickness measurement - Ships for liquefied gases - Structural areas with substantial corrosionto determine the full extent of the corrosion pattern. The survey will not be considered complete until these additional thickness measurements have been carried out.