Section 6 Procedures for testing tanks and tight boundaries

6.1.1 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 weathertightness of structures.

6.2.1 The testing requirements for gravity tanks, defined as tanks subject to a vapour pressure not greater than 70 kN/m², and other boundaries required to be watertight or weathertight, are to be tested in accordance with this Section. Tests are to be carried out in the presence of a Surveyor at a stage sufficiently close to completion such that the strength and tightness are not subsequently impaired and prior to any ceiling and cement work being applied over joints.

6.2.2 The testing of structures not listed in this Section are to be specially considered.

6.4.1 Where a structural test is specified in Table 3.6.1 Testing requirements , unless specified otherwise, a hydrostatic test is to be carried out in accordance with Pt 4, Ch 3, 6.6 Definitions and details of tests 6.6.1 . Where practical limitations prevent a hydrostatic test being carried out, a hydropneumatic test in accordance with Pt 4, Ch 3, 6.6 Definitions and details of tests 6.6.2 is to be conducted. All external boundaries of the tested space are to be examined for structural distortion, bulging, buckling or other related damage and leaks.

6.4.2 A hydrostatic test or hydropneumatic test may 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 . Where possible, the leak test is to be carried out before the unit is afloat.

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

6.4.4 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 following the same construction, welding and quality procedure) may be exempt from such testing, 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. The relaxation to accept leak testing and thorough inspections instead of a structural test on subsequent vessels in a series does not apply to cargo space boundaries adjacent to other compartments or to the boundaries of tanks for segregated cargoes or pollutants.

6.4.5 Tanks exempted from structural testing in Pt 4, Ch 3, 6.4 Structural test procedures 6.4.3 and may require structural testing if found necessary after the structural testing of the first tank.

6.4.6 For watertight boundaries of spaces other than tanks, excluding chain lockers, structural testing may be exempted, provided that the watertightness in all boundaries of exempted spaces are verified by leak tests and thorough inspection.

6.4.7 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.

6.5.1 Where a leak test is specified in Table 3.6.1 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 Pt 4, Ch 3, 6.6 Definitions and details of tests 6.6.4 to Pt 4, Ch 3, 6.6 Definitions and details of tests 6.6.6. A hydrostatic or hydropneumatic test conducted in accordance with the applicable requirements of Pt 4, Ch 3, 6.6 Definitions and details of tests 6.6.1 and Pt 4, Ch 3, 6.6 Definitions and details of tests 6.6.2 will be accepted as a leak test on the condition that safe access to all joints being examined is provided. 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.

6.5.2 A hose test will be accepted as means of verifying the tightness of joints only in specific locations, identified in Table 3.6.1 Testing requirements.

6.5.3 Air tests of joints may 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.

6.5.4 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.

6.6.1  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 3.6.1 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.

6.6.2  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 Pt 4, Ch 3, 6.6 Definitions and details of tests 6.6.4 are to be adhered to.

6.6.3  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 may be replaced by a careful visual examination of welded connections, supported by an ultrasonic or penetration leak test, or an equivalent, see SOLAS Reg. II-1/Regulation 11 - Initial testing of watertight bulkheads, etc.

6.6.4  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 may 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.

6.6.5  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 on the opposite side. 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 may be carried out for partial penetration welds where the root face is greater than 6 mm.

6.6.6  Vacuum box test is a test used to verify the tightness of joints by means of a localised air pressure differential and 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. Air within the box is to be removed by an ejector to create a reduction in pressure. The pressure inside the box during the test is to be maintained between 0,20 to 0,26 bar.

6.6.7  Ultrasonic test may be used where a hose test is not practical to verify the tightness of a boundary, see Pt 4, Ch 3, 6.6 Definitions and details of tests 6.6.3. An arrangement of ultrasonic echo transmitters is to be placed inside a compartment and a receiver outside. The receiver is to be used to detect any leaks in the compartment.

6.6.8  Penetration test may be used where a hose test is not practical to assess butt welds, see Pt 4, Ch 3, 6.6 Definitions and details of tests 6.6.3, 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 may be applied on the other side of the weld to aid leak detection.

6.6.9 Other methods of testing may be considered and are to be agreed by LR prior to commencement of testing.

6.7.1  A final coating may be applied over automatic butt welds before the completion of a leak test, provided that careful visual inspections show continuous uniform weld profile shape, free from repairs, and the results of selected NDE testing show no significant defects. For all other joints, the final coating is to be applied after the completion of a leak test. The Surveyor reserves the right to require a leak test prior to the application of the final coating over automatic erection butt welds.

6.7.2 Any temporary coating which may conceal defects or leaks is to be applied at a time as specified for the final coating, see Pt 4, Ch 3, 6.7 Application of coating 6.7.1. This requirement does not apply to shop primer.