Question

(a) Describe how bulkheads are tested. (6)

(b) A double bottom tank containing seawater is 6m long, 12m wide and 1m deep. The inlet pipe from the pump has its centre 75mm above the outer bottom. The pump has a pressure of 70kN/m² and is left running indefinitely, Calculate the load on the tank top: (10)

(i) if there is no outlet

(ii) if the overflow pipe extends 5 m above the tank top.

Answer 1

Part (a)

Testing for Water Tightness:

Hose Test: This involves applying a high-pressure water jet (2 bar from a distance of 1.5 meters, nozzle diameter at least 12mm) to the bulkhead's surface. This test directly checks for leaks. The test is typically done from the side where the stiffeners are attached.
Air Pressure Test: An air pressure test applies pressure (0.2 bar) for about an hour, detecting leaks that may not be apparent during the hose test. This usually happens prior to the application of protective coatings.
Structural Test: Visual inspection, especially of welding joints, is carried out. Non-Destructive Testing (NDT) is done where necessary. Tanks designed to hold liquids, which form subdivisions of the ship, are tested for tightness with a water head up to the deepest subdivision load line or to a head of 2/3 the depth from the top of the tank to the margin line, whichever is greater.

✓ Verified Model Answer (Text Solution)

Testing for Water Tightness: