Tightness test

An air test or other medium test carried out to demonstrate the tightness of the structure.

- Air test – A test to verify the tightness of the structure by means of air pressure difference.

- Chalk test – A test for weathertightness of the hatch covers or doors. It uses chalk rubbed on the compression bar to imprint on the seal.

- Hose test – A test to verify the tightness of the structure by a jet of water. It is usually applied for hatch covers, doors and windows.

- Hydropneumatic test – A combination of hydrostatic and air testing consisting in filling the tank with water up to its top and applying an additional air pressure.

- Hydrostatic test – A test to verify the structural adequacy of the design and the tightness of the tank structure by means of water pressure. The test employs the filling of the tank with water according to Rules requirements, usually up to the top of overflow or 2.4m above the highest point of tank.

Notes from BNC Leak Tests Program:

1. Where one tank boundary is formed by the ship shell, the leak test is to be carried out before launching.

2. If this is impossible, manually made butt welds on the ship shell can be tested by vacuum box before launching. Butts shall be not coated. Remaining welds can be leak-tested after launching.

3. For tanks without boundary formed by the ship shell, the leak testing may be carried out after launching.

4. Leak tests are to be carried after all attachments, outfitting, or penetration, which may affect the strength or tightness, have been completed, and before any ceiling and cement work is applied over joints. If after the leak test any hot work was carried out in the tank, the leak test shall be repeated. The procedure shall be agreed with Class Surveyor and Owner’s Inspector.

5. Watertightness of welds, which are not subject to air testing, should be checked by chalk and kerosene test at the section fabrication stage.

6. Bottom drain plugs shall be checked by a dye penetrant test at the section fabrication stage.

7. Welds shall be cleaned and all damages to the tank boundaries, if any, shall be repaired before the leak tests.

8. If it is ensured that in adjacent tanks, the same type of liquid is carried, e.g. in adjacent ballast tanks, the erection welds as well as welds of assembly openings may be coated prior to the leak test. Otherwise these welds are to be coated after the leak test is carried out.

9. Shopprimers are not regarded as a coating within the scope of the leak tests.

10. It is not allowed to repair leaking welds when the tank is kept under pressure.

11. After launching, hydrostatic tests of few representative tanks shall be carried out to verify the structural adequacy of the design. Tanks to be selected so that all representative structural members are tested for the expected tension and compression.

12. Hydrostatic tests may be carried out for the first vessel only.

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