Surveys of Liquefied Gas Carriers

(i) Bottles are to be examined internally and externally. If they can not be examined internally they are to be gauged. When considered necessary by the Surveyor, they are to be hydrostatically tested to at least 1.2 times the working pressure. Relief valves are to be proven operable.

(ii) Where an alkali (or other) scrubber is fitted in the system the scrubber, circulating pump, valves and piping are to be examined internally and externally.

2.9.2 Special survey of inert gas system

At each special survey of inert gas system in addition to the requirements for the annual surveys in 2.9.1, the following are to be complied with:

(a) All valves, including valves at boiler uptakes, air seal valves at uptakes, scrubber isolating valves, fan inlet and outlet isolating valves, main isolating valves, re-circulating valves (if fitted), pressure/vacuum breakers and cargo tank isolating valves are to be examined.

(b) Scrubbers are to be examined.

(c) Fans (blowers) including casing drain valves are to be examined.

(d) Fan (blower) drives, either electric motor or steam turbine, are to be examined.

(e) Bellows expansion pieces are to be examined.

(f) Sea water pumps, valves and strainers for scrubbers and water seals together with piping connections at scrubbers, water seals, shell plating and the remainder of the sea water piping are to be examined.

(g) Stand pipes, where fitted, for purging in each cargo tank are to be examined.

(h) Deck seals or double block and bleed assemblies, and non-return valves are to be examined externally and internally.

(i) The special survey may be commenced at 4th annual survey and be progressed during the su cceeding year with a view to completion by the 5th anniversary date. The flue gas system is to be presented for survey within 3 months before the due date of the special survey. The requirements for survey to qualify for the commencement of the special survey are to be no less than those of an annual survey as outlined in paragraph 2.9.1.

2.10 Surveys of Liquefied Gas Carriers

2.10.1 Annual Surveys

In addition to the surveys as per applicable requirements of 2.5, the components, equipment and outfit as listed below are to be examined as to whether they are in unobjectionable maintenance condition.

(a) Cargo handling systems are to be examined as follows:

(i) The cargo and process piping, expansion joints, cargo hoses and machinery, such as heat exchangers, vapourizers, pumps, compressors are to be externally examined.

(ii) The availability of the required spool pieces for piping separation is to be verified.

(iii) The log books are to be examined with regard to correct functioning of the cargo containment an d cargo handling systems. The running hours per day of the re-liquefaction plants or the boil-off rate and the inert gas consumption are to be considered.

(iv) It is to be ensured that the relevant instructions and information material such as cargo handli ng plants, cargo tank loading limit information, cooling down procedures etc. are on board.

(b) Cargo containment venting systems are to be examined as follows:

(i) Venting system for cargo tanks, inter barrier spaces (in case of Type A tanks, cargo holds) are to be visually examined. It is to be verified that the cargo tank relief valves are sealed and that the certificate containing details on opening/closing pressure of the relief valves is kept on board.

2.10 Surveys of Liquefied Gas Carriers

(ii) Protection screens and flame arresters, if fitted, are to be examined for corrosion and cleanliness.

(c) Instrumentation and safety systems are to be examined as follows:

(i) The monitoring and control equipment for pressure, temperature and liquid levels is to be verified as to its good working order, by one or several of the following methods:

(1) Visual external examination.

(2) Comparison of read-outs of different indicators.

(3) Comparison of read-outs with the data of the cargo actually handled.

(4) Examination of repair and maintenance records with reference to the cargo plant repair.

(ii) Emergency shut-down valves at shore connections and tanks are to be tested without flow in the pipe lines. It is to be verified that operation of the emergency shut-down system is to cause the cargo pumps and compressors to stop.

(iii) The fixed and portable gas detection equipment, including indicators and alarms, is to be tested for correct functioning.

(d) In gas-dangerous spaces and zones the electrical equipment including cables and their supports, is to be visually examined, particularly regarding explosion protection.

(e) Ventilation systems for all spaces in the cargo area, including cargo pump rooms, cargo compressor rooms, electrical motor rooms, cargo control rooms, and other spaces used for cargo handling operations are to be examined as to their satisfactory operating condition.

(f) Inert gas/dry air systems, including the means for prevention of backflow of cargo vapour to gas -safe spaces are to be checked as to their satisfactory operating condition. See also 2.9.1.

(g) All fire fighting systems in the cargo area, including the compressor room, are to be checked visually. See also 2.5.1(j).

(h) The following items of equipment are to be inspected for their condition and correct functioning:

(i) Means for ensuring gas-tightness of wheelhouse windows and doors, windows in end bulkheads of superstructures and deck house facing the cargo area or stern loading/unloading arrangements, and closing devices of all air intakes and openings into accommodation, service and control stations.

(ii) Sealing arrangements for tanks or tank domes penetrating decks or tank covers.

(iii) Drip trays or insulation for deck protection against cargo leakage.

(iv) Arrangements for heating of hull structural elements, if any. Access to the heated cofferdams etc. is normally not required.

(v) Electric bonding of cargo piping systems.

(vi) Arrangements for the use of boil-off gas as fuel, including alarm and safety systems.

2.10.2 Intermediate Surveys

In addition to the surveys as per 2.10.1 the checks mentioned below are to be carried out. The intermediate survey supplements the preceding annual survey by testing of cargo handling installations, with pertinent automatic controls, alarm and safety systems, for their correct functioning.

(a) Cargo systems and tanks are to be examined as follows:

(i) The piping system in cargo tanks is to be examined. Bonding of tanks and pipes is to be controlled.

(ii) It is to be checked whether the ship's cargo hoses are approved and in satisfactory condition. At intervals of not more than 2.5 years, the cargo hoses are to be subjected to a pressure and conductivity test.

(iii) Weather deck: Piping systems essential for operation of the ship, e.g. cargo transfer, bunkering and ballast lines, are to be examined.

(iv) For ships between 5 and 10 years of age, an overall survey of representative ballast tanks is to be carried out.

2.10 Surveys of Liquefied Gas Carriers

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

(vi) Close-up survey as required in Table I 2-29A.

(b) Cargo containment venting systems are to be examined as follows:

(i) The drainage arrangements of venting systems are to be examined.

(ii) If cargo tanks are equipped with relief valves with non-metallic membranes in main or pilot valves, such membranes are to be replaced by new ones and the valves are to be adjusted, function tested and sealed. These measures need not be taken simultaneously with the intermediate survey, provided that the non-metallic membranes are renewed at intervals not exceeding 3 years.

(c) Instrumentation and safety systems are to be examined as follows:

(i) The alarm, control and safety systems of the cargo installation are to be visually examined and tested by varying pressures, temperatures and liquid levels, as far as practicable, and comparisons are to be drawn, using test instruments. Simulated testing may be accepted for sensors which are not accessible or for sensors located within cargo tanks or inertised cargo holds. This test is to include testing of alarm and safety functions.

(ii) The gas detection equipment, including indicators and alarms, is to be tested for correct functioning.

The piping of the gas detection system is to be visually inspected for corrosion and damages. The tightness and integrity of suction lines between suction points and analyzing units are to be verified as far as possible.

(iii) On ships having arrangements for the use of boil-off gases as fuel, safety, control, alarm and shut-down systems are to be checked. The extent of the checks is to be determined from case to case.

(d) Electrical installations are to be examined as follows:

Electrical equipment in gas-dangerous spaces and zones is to be examined in respect of the following:

(i) Protective earthing (spot check).

(ii) Integrity of certified safe-type equipment.

(iii) Damage to outer sheath of cables.

(iv) Function testing of pressurized equipment, and of associated alarms.

(v) Testing of systems for de-energizing noncertified safe electrical equipment located in spaces protected by air-locks, such as electric motor rooms, cargo control rooms, etc.

(vi) Checking of insulation resistance of circuits. Relevant measurements are only to be made when the ship is in gas free or inertised condition. If proper test reports are available on board, readings made by the crew may be accepted.

(vii) When the ship is in gas free condition, it is to be verified that the cargo tanks are electrically bonded to the hull.

2.10.3 Special Survey

Where applicable, in addition to the surveys as per applicable requirements in 2.7 and 2.10.2, the examinations and tests as mentioned below are to be carried out:

(a) The cargo containment systems is to be examined as follows:

(i) All cargo tanks are to be examined internally.

(ii) As far as practicable, the outer surface of un-insulated cargo tanks or the outer surface of cargo tanks insulations, including vapour or protective cover if any, is to be examined, as are areas in way of supports, keys and anti-flotation chocks. Partial removal of insulation may be required in order to verify the condition of the tank or the insulation itself, if found necessary by the Surveyor. Where, e.g. in the case of membrane type cargo tanks, the insulation arrangement is such that it cannot be examined, the surrounding structures of wing tanks, double bottom tanks and cofferdams are to be examined for cold spots when cargo tanks are in cold condition. This examination may be dispensed with if the log book, together monitoring instruments gives sufficient evidence of the integrity of the insulation system.

2.10 Surveys of Liquefied Gas Carriers

(iii) Thickness measurements of cargo tanks may be required if deemed necessary by the Surveyor.

(iv) Non-destructive examination of main structural members, tank shells and highly stressed parts, including welded connections is to supplement cargo tank inspections as far as deemed necessary by the Surveyor. The following items are inter alia considered as highly stressed parts:

(1) Cargo tank supports and longitudinal and transverse securing devices.

(2) Y-connections between tank shells and longitudinal bulkheads of slop tanks.

(3) Web frames or stiffening rings.

(4) Swash bulkheads and their fixations.

(5) Dome and sump connection to tank shells.

(6) Foundations for pumps, towers, ladders, etc.

(7) Pipe connections.

(v) For independent Type B tanks, the extent of non-destructive examination is defined in a plan specially prepared for the particular cargo tank design.

(vi) The tightness of all cargo tanks is to be verified by an appropriate procedure provided that the effectiveness of the ship gas detection equipment has been confirmed, it is to be acceptable to utilize this equipment for the tightness test of independent tanks below deck during the first process of filling of the cargo tanks subsequent to the special survey.

(vii) Where the findings of checks according to (i) to (vi) of this subparagraph or an examination of the log book raise doubts as to the structural integrity of a cargo tank, a hydrostatic or hydro -pneumatic test is to be carried out. For integral tanks and for independent Type A and B tanks, the test pressure at the top of tank is to correspond to the MARVS (maximum allowable relief valve setting) of the tank. For independent Type C tanks, the test pressure at the top of the tank is not to less than 1.25 times the MARVS.

(viii) Extended tests

On the occasion of special surveys No.2, 4, 5, etc., all independent type C tanks are to be either (1) Hydrostatically or hydro-pneumatically tested to a pressure at the upper edge of the tanks of

1.25 times MARVS and thereafter, non-destructively, in accordance with (iv)/(v) of this subparagraph, or

(2) Subjected to a thorough, systematically planned nondestructive examination procedure. These tests are to be carried out in accordance with a plan specially prepared for the particular tank design. If a special plan dose not exist, the following applies with regard to nondestructive testing:

Testing is to be concentrated on the detection of surface cracks in welded co nnections in highly stressed areas, as listed in (iv) of this subparagraph. At least 10% of the length of the welded connections in each of the above mentioned areas are to be tested. This testing is to be carried out internally and externally, as far as practicable. Insulation is to be removed as necessary for the required nondestructive examination.

(b) Tank supporting structures and insulation are to be examined as follows:

(i) As far as practicable, all hold spaces and hull insulation (if provided), sec ondary barriers and tank supporting structures are to be visually examined. The secondary barrier of all tanks is to be checked for its effectiveness by means of a pressure/vacuum test, a visual examination or some other acceptable methods.

(ii) For membrane and semi-membrane tank systems, the inspection and testing as per (i) of this subparagraph are to be carried out in accordance with a plan and an approved method specially prepared for the actual tank system.

(c) Pressure and vacuum relief valves are to be examined as follows:

(i) The pressure relief valves for cargo tanks are to be opened up for examination, adjusted, function tested and sealed. The requirements of 2.10.2(b)(ii) regarding replacement of nonmetallic membrane apply. The following tolerances apply regarding the set pressures of cargo tank pressure relief valves:

2.10 Surveys of Liquefied Gas Carriers

Set pressure P Tolerance P ≤ 0.15 MPa  10 % 0.15 MPa< P ≤ 0.3 MPa  6 %

0.3 MPa< P  3 %

(ii) Pressure/vacuum relief valves, rupture discs and other pressure relief devices for inter-barrier spaces and hold spaces are to be examined, opened and tested if necessary, depending on their design.

(d) It is to be verified that cargo tanks are to be electrically bonded to the hull.

(e) Piping systems are to be examined as follows:

(i) Cargo, liquid nitrogen and process piping systems, including their valves and actuators, compensators etc., are to be opened up for examination as deemed necessary by the Surveyor.

Insulation is to be removed as deemed necessary to ascertain the external condition of pipes. At the Surveyor's discretion welded seams at branches and bends are to be subjected to non-destructive random crack tests. If the visual examination raises doubts as to the integrity of pipelines, they are to be pressure tested to 1.25 times MARVS. After reassembly the complete piping system is to be tested for leaks.

(ii) The pressure relief valves in piping systems are to be function tested. A random selection of valves is to be opened up for examination and adjusted.

(iii) Cargo pumps, booster pumps and gas compressors are to be inspected and tested.

(f) The re-liquefaction installation is to be examined as follows:

(i) The parts of compressors subject to wear, such as cylinders, pistons, connecting rods, glands, bearings, auxiliary components, such as shafts, rotors and diffusers of centrifugal pumps, etc., are to be examined.

(ii) The drives of compressors, including those components which are required for operation of the drives, are to be inspected.

(iii) All the covers of heat exchangers are to be dismounted for inspection of pipe plates, if necessary, pressure and tightness tests are to be connected. If only a few pipes have been exchanged, a tightness test may be sufficient.

(iv) The safety equipment (pressure relief valves, rupture discs) is to be checked.

(g) At special surveys Nos. 2, 4, 5 etc. all process pressure vessels are to be tested pneumatically at a pressure equal to 1.1 times the working pressure, unless the result of the survey requires a hydraulic pressure test to 1.5 times the working pressure.

(h) The equipment connected with fuel gas evaporated from the LNG cargo is to be examined as follows:

(i) The gas conditioning plant is to be inspected externally.

(ii) The pipe or duct enclosing the fuel gas line is to be inspected for leaks. The ventilation system of that pipe or duct as well as the inertising equipment of a double wall piping system is to be checked for their operability. Heat exchangers are to be visually examined internally.

(iii) Safety devices: See 2.10.2(c).

(i) In addition to the visual examinations and tests as per 2.10.2(d) the protection devices of electric motors are to be tested.

(j) Miscellaneous items are to be examined as follows:

(i) Drainage systems for removal of water or cargo inter-barrier spaces and hold spaces are to be examined and tested where necessary.

(ii) All gas tight bulkheads are to be inspected. The effectiveness of gas tight shaft sealings is to be verified.

(iii) It is to be checked whether the spare parts stipulated in the GC code or IGC code are kept on board.

(iv) Any installations for heating of hull structures are to be examined for correct functioning .

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