Section 7 Inspection and testing procedures

7.1.1 The test procedures detailed in this Section are to be used to confirm the watertightness of tanks and watertight boundaries, the structural adequacy of tanks and the weathertightness of structures.

7.1.2 A structural and leak test plan is to be submitted defining the compartments or tanks to be tested and the method of testing in accordance with the requirements of this Section.

7.1.3 Although referred to as watertight, some compartments or tanks may require to be tested as gastight or oil-tight.

7.1.4 The testing requirements for gravity tanks, defined as tanks subject to a vapour pressure not greater than 70 kN/m², independent tanks and watertight and weathertight compartments, are listed in Table 6.7.1 Testing requirements. Tests are to be carried out in the presence of the Surveyor at a stage sufficiently close to completion such that the strength and tightness are not subsequently impaired by subsequent work and prior to any sealing and cement work being applied over joints.

7.1.5 For naval vessels which are also required to comply with SOLAS, structural testing is to be carried out for all tanks forming part of the watertight sub-division of the ship in accordance with SOLAS requirements unless:

1. the shipyard provides documentary evidence of the Owner’s agreement to a request to the appropriate Naval or Flag Administration for an exemption from the application of SOLAS Chapter II-1 Regulation 11 - Initial testing of watertight bulkheads, etc., or for an exemption agreeing that the proposed alternative approach is equivalent to SOLAS Chapter II-1 Regulation 11 - Initial testing of watertight bulkheads, etc.; and
2. the above-mentioned exemption/equivalency has been granted by the responsible Naval or Flag Administration.

7.1.6 The testing of structures not listed in this Section is to be specially considered.

7.3.1 Tanks which are intended to hold liquids, and which form part of the watertight sub-division of the ship, shall be tested for tightness and structural strength as indicated in Table 6.7.1 Testing requirements. Tanks which do not form part of the watertight sub-division of the ship need not be structurally tested providing that the watertightness of all boundaries of these spaces is verified by leak tests and thorough inspection.

7.3.2 Where a structural test is specified in Table 6.7.1 Testing requirements unless specified otherwise, a hydrostatic test is to be carried out in accordance with Vol 1, Pt 6, Ch 6, 7.7 Definitions and details of tests 7.7.1. Where practical limitations prevent a hydrostatic test being carried out, a hydropneumatic test in accordance with Vol 1, Pt 6, Ch 6, 7.7 Definitions and details of tests 7.7.2 may be conducted. All external boundaries of the tested space are to be examined for structural distortion, bulging, buckling, or other related damage and/or leaks.

7.3.3 A hydrostatic test or hydropneumatic test can be carried out afloat to confirm the structural adequacy of tanks, provided that a leak test is carried out and the results are confirmed as satisfactory before the vessel is afloat. The testing afloat is to be carried out by separately filling each tank and cofferdam to the test head given in Table 6.7.1 Testing requirements. An internal inspection of the tanks is to be made whilst the ship is afloat.

7.3.4 Consideration is to be given to the selection of tanks to be structurally tested. Selected tanks are to be chosen so that all representative structural members are tested for the expected tension and compression. Tank boundaries are to be tested from at least one side.

7.3.5 Compartments to be tested are to be structurally complete and all fittings which affect the watertight integrity of the compartment such as doors, hatches, manholes, penetrations, valves and glands are to be fitted.

7.3.6 In compartments containing the stabiliser fins, rudder stocks, sonar hull outfit, echo sounders, etc. the bearing houses are to be installed and the seating arrangements completed before testing.

7.3.7 Arrangements are to be provided to ensure the free passage of air from the top of the tank tested. The air pipe or indicator test plug may be used for this purpose.

7.3.8 Where necessary, additional temporary supports are to be fitted to the hull to prevent excessive deformation.

7.3.9 It is recommended that a leak test in accordance with Vol 1, Pt 6, Ch 6, 6.7 Watertight collars is carried out before the structural test commences to identify any leak paths which may compromise the structural test.

7.3.10 Where it is intended to carry out structural tests after the protective coating has been applied, welds are to be leak tested prior to the coating application.

7.3.11 For welds other than manual and automatic erection welds, manual fillet welds on tank boundaries and manual penetration welds, the leak test may be waived provided that careful visual inspection is carried out, to the satisfaction of the Surveyor, before the coating is applied. The cause of any discolouration or disturbance of the coating during the test is to be ascertained, and any deficiencies repaired.

7.3.12 Equivalent proposals for testing will be considered.

7.3.13 Where it is intended to carry out structural tests after the protective coating has been applied, welds are to be leak tested prior to the coating application.

7.4.1 For tanks of the same structural design, configuration and the same general workmanship, as determined by the attending Surveyor, a structural test need only be carried out on one tank, provided that all subsequent tanks are tested for leaks by an air test.

7.4.2 Where the structural adequacy of a tank has been verified by structural testing on a previous vessel in a series, tanks of structural similarity on subsequent vessels within that series (which are built at the same shipyard) need not be structurally tested, provided that the watertightness of all exempt tanks is verified by leak tests and thorough inspection. However, structural testing is to be carried out for at least one tank of each type of tank on every vessel in the series.

7.4.3 For sister ships built two or more years after the delivery of the last ship of the series, the application of the provisions of Vol 1, Pt 6, Ch 6, 7.4 Structural testing for Naval ships 7.4.2 will be specially considered provided that the general practices, equipment and workmanship of the shipyard have been maintained continuously, and an non-destructive testing programme is implemented for the tanks not subject to structural tests.

7.4.4 Tanks exempted from structural testing in Vol 1, Pt 6, Ch 6, 7.4 Structural testing for Naval ships 7.4.2 will require structural testing if found necessary after the structural testing of the first tank.

7.5.1 Generally all boundaries for watertight subdivision are to be given a leak test when structural work is complete. The test is to be carried out before the compartment is fitted out and linings or covering applied.

7.5.2 Testing is to be carried out by applying an efficient indicating liquid, e.g. soapy water solution, to the weld or outfitting penetration being tested, while the tank or compartment is subject to an air pressure of at least 0,15 bar.

7.5.3 It is recommended that the air pressure be raised to 0,2 bar and kept at this level for about one hour to reach a stabilised state, with a minimum number of personnel in the vicinity, and then lowered to the test pressure prior to inspection.

7.5.4 A U-tube filled with water to a height corresponding to the test pressure is to be fitted for verification and to avoid over-pressure. The U-tube is to have a cross-section larger than that of the air supply pipe. In addition, the test pressure is to be verified by means of a calibrated pressure gauge, or alternative equivalent system.

7.5.5 Leak testing is to be carried out, prior to the application of a protective coating, on all fillet welds and erection welds on tank boundaries, except welds made by automatic processes and on all outfitting penetrations.

7.5.6 Selected locations of automatic erection welds and pre-erection manual or automatic welds may also be required to be tested before coating, at the discretion of the Surveyor.

7.5.7 Where a leak test is specified in Table 6.7.1 Testing requirements unless specified otherwise, a tank air test, compressed air fillet weld test or vacuum box test is to be carried out in accordance with the applicable requirements of Vol 1, Pt 6, Ch 6, 7.7 Definitions and details of tests 7.7.4 to Vol 1, Pt 6, Ch 6, 7.7 Definitions and details of tests 7.7.6. A hydrostatic or hydropneumatic test conducted in accordance with the applicable requirements of Vol 1, Pt 6, Ch 6, 7.7 Definitions and details of tests 7.7.1 and Vol 1, Pt 6, Ch 6, 7.7 Definitions and details of tests 7.7.2 will be accepted as a leak test on the condition that safe access to all joints being examined is provided, see Vol 1, Pt 6, Ch 6, 7.8 Safe access to joints 7.8.1. Where a hydrostatic or hydropneumatic test is applied as a leak test, the external boundaries are to be free of any liquid residue prior to the commencement of the test.

7.5.8 A hose test will be accepted as means of verifying the tightness of joints only in specific locations, identified in Table 6.7.1 Testing requirements.

7.5.9 Air tests of joints can be conducted at any stage during construction provided that all work that might affect the tightness of the joint is completed before the test is carried out.

7.5.10 Where acceptable to the attending Surveyor, provided that careful visual inspections show a continuous uniform weld profile shape, free from repairs, and the results of selected NDE testing show no significant defects, the leak testing of automatic butt welds and semi-automatic (flux core arc welding) butt welds may be omitted.

7.6.1 Where LR has been requested to witness gastight testing in accordance with a specified standard, the boundaries of citadels and zones defined in Vol 1, Pt 4, Ch 1, 7 Design guidance for nuclear, biological and chemical defence are to be tested for gas tightness using a pressure drop test. In addition, compartments containing noxious or explosive gases such as Acetone, Dope, Flammable stores, Oxygen, etc. are to be subject to a pressure drop test.

7.6.2 The test is to be carried out with compartment as near to completion as possible. Further work on a compartment after the test may result in a retest.

7.6.3 In certain compartments that are not able to be made fully gastight due to operational requirements, a greater fall in pressure may be accepted at the discretion of the surveyor. In no case is the pressure to drop more than 0,0075 bar (75 mm of fresh water) in 10 minutes from an initial 0,015 bar (150 mm of fresh water).

7.6.4 Consideration will be given to the testing of adjacent boundaries or equivalent in those spaces which are not able to be closed, such as gun rings and main machinery spaces.

7.7.1 Hydrostatic test is a test conducted by filling a space with a liquid to a specified head. Unless another liquid is approved, the hydrostatic test is to consist of filling a space with either fresh or sea water, whichever is appropriate for the space being tested, to the level specified in Table 6.7.1 Testing requirements For tanks intended to carry cargoes of a higher density than the test liquid, the head of the liquid is to be specially considered.

7.7.2 Hydropneumatic test is a combination of a hydrostatic test and a tank air test, consisting of partially filling a tank with water and conducting a tank air test on the unfilled portion of the tank. A hydropneumatic test, where approved, is to be such that the test condition in conjunction with the approved liquid level and air pressure will simulate the actual loading as far as practicable. The requirements for tank air testing shown in Vol 1, Pt 6, Ch 6, 7.7 Definitions and details of tests 7.7.4 and the safety precautions given in Vol 1, Pt 6, Ch 6, 7.5 Leak testing are to be adhered to.

7.7.3 Hose test is a test used to verify the tightness of joints with a jet of water. The jet of water is to be directed perpendicular to the joint. It is to be carried out with the pressure in the hose nozzle maintained at not less than 2,0 bar during the test. The hose nozzle is to have a minimum inside diameter of 12 mm and is to be situated no further than 1,5 m from the joint. Where a hose test is not practical because of possible damage to machinery, electrical equipment insulation or outfitting items, it can be replaced by a careful visual examination of welded connections, supported by an ultrasonic or penetration leak test, or an equivalent.

7.7.4 Tank air test is to be used to verify the tightness of a compartment by means of an air pressure differential and leak indicator solution. An efficient indicating solution (e.g. soapy water) is to be applied to the weld or penetration being tested and is to be examined whilst an air pressure differential of not less than 0,15 bar is applied by pumping air into the compartment. Arrangements are to be made to ensure that any increase in air pressure does not exceed 0,30 bar. A U-tube with a height sufficient to hold a head of water corresponding to the required test pressure is to be used for verification and to avoid overpressure. The cross-sectional area of the U-tube is not to be less than that of the pipe supplying air to the tank. Alternatively, two calibrated pressure gauges can be considered acceptable. All boundary welds, including pipe connections in the compartment are to be examined twice. The first is to be examined immediately upon applying the leak indication solution; the second approximately five minutes afterwards.

7.7.5 Compressed air fillet weld test. This test consists of compressed air being injected into one end of a fillet welded joint and the pressure verified at the other end of the joint by a pressure gauge. Pressure gauges are to be arranged so that an air pressure of at least 0,15 bar above atmospheric pressure can be verified at each end of all passages within the portion being tested. A leak indicator solution is to be applied and the weld line examined for leaks. A compressed air test can be carried out for partial penetration welds where the root face is greater than 6 mm.

7.7.6 Vacuum box test is a test used to verify the tightness of joints by means of a localised air pressure differential and leak indicator solution. The test is to be conducted with the use of a box with air connections, gauges and an inspection window that is to be placed over the joint being tested with a leak indicator solution applied. The air within the box is to be removed by an ejector to create a vacuum, i.e. a pressure differential of 0,20 to 0,26 bar inside the box.

7.7.7 Penetration test can be used where a hose test is not practical to assess butt welds, see Vol 1, Pt 6, Ch 6, 7.7 Definitions and details of tests 7.7.3, by applying a low surface tension liquid to one side of a compartment boundary. When no liquid is detected on the opposite side of the boundary after expiration of a defined period of time, the verification of tightness of the compartment’s boundary may be assumed. A developer solution can be applied on the other side of the weld to aid leak detection.

7.7.8 Gastight test. The pressure in the compartment is to be brought to 0,015 bar and the supply isolated. The fall in pressure after 10 minutes is not to be greater than 0,0013 bar. If the specified pressure drop occurs, the compartment is to be inspected for leaks and the test repeated until the specified standard is achieved. A U-tube filled with water to a height corresponding to the test pressure is to be fitted for verification and to avoid overpressure. The U-tube is to have a cross-section larger than that of the air supply pipe.

7.7.9 Protective coating. Protective coating is the coating system applied to protect the structure from corrosion. This excludes the prefabrication primer.

7.8.1 For leak tests, safe access to all joints under examination is to be provided.