The working pressures in case of jacket water system or lubricating oil system are usually of higher pressure than sea water system. If the leakage takes place in the jacket cooling water side or lubricating oil side, the flow from any point of leakage is in to the sea water side of the cooler. If the leakage is heavy then, usual indication is loss of jacket cooling water or lubricating oil.
Ensure the end covers are removed from the sea water box side and secure the tube stack by dog clamp arrangement-tube stack should not be disturbed when shell is under pressure.
• Clean the sea water side of the cooler.
• Start the fresh water cooling pump or lubricating oil pump.
• Let the fluid circulate through the cooler spaces on the outside of the tubes.
• Leakage within the tubes or at the junction of the tube plate will show up as liquid trickling.
• Identify the tube which is leaking. It is a time consuming procedure so be patient.
Fluorescent Halo Test
Small leaks are extremely difficult to detect, especially if the time available is very less. Owing to paucity of time it, will be difficult to get sea water cooling spaces dried out. The damp tube plates deter the small amounts of leakage. If the leakage is very small and time availability is less then follow the below procedure:
• A small amount of fluorescent sodium crystals is dissolved in water within the space surrounding the tubes.
• The tube plates are then viewed under a source of ultra violet light.
• Even very small leakage is sharply visible as a fluorescent halo.
Soap Bubble Test
If the time availability is high and if the heat exchanger can be isolated, then carry out then following procedure:
• Ensure the end covers are removed from the sea water box side.
• Isolate the entire cooler and pressurize the shell side with air.
• Use soap solution and apply the same at the tube ends.
• Bubble formation will indicate the leaking tube.
Plugging the Tube
• Once the leaky tube is detected, measure the inside diameter of the tube and find suitable plugs for plugging.
• For plugging the leaky tube or tubes, plugs made of brass [same material as the tubes] or plastic are being used on either end of the leaky tube.
• Plug should be driven securely so as to isolate it completely.
• Carry out a leak test again to confirm that the leakage is arrested.