There are three methods used for checking the weather tightness of the hatch covers -
1. Hose test : Water spray from a nozzle 12mm in diameter is sprayed over the point where the hatch cover touches the hold coaming and joints in the hatch cover. Water is applied from a distance of 1-1.5 meters and usually 4-6 bars pressure. This test is required to be carried out by two persons and cannot be carried out in sub zero temperatures.
2. Chalk test : it is the oldest and the most traditional method of doing the test. It is used only for testing the joints along the compression bar. Chalk powder is applied to the steel backs and hatch cover closed and tightened and then the hatch cover is opened again to check the gaps in chalk mark which shows the position of the leakage. The disadvantage of this test is it cannot check the degree of tightness between the rubber packing and compression bar. Only an chalk impression cannot guarantee weather tightness.
3. Ultrasonic test : this is the most accurate method of testing the weather tightness. An ultrasonic transmitter is placed at the tank top of a empty hold. The hatch covers are now closed and transmitter is switched on. A person outside on the deck uses a receiving probe and passes over all hatch cover joints. An alarm is given when the leak is detected.
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