Leakage Detection in Shell and Tube type Heat exchangers

Tubes are replaced heat exchanger provided that there is a complete tube failure. If the tube is found leaking, the tube is plugged. However the procedure for leakage detection is shown below.
Leakage detection in shell and tube type cooler.
The working pressure in case of jacket water system or lubricating oil system are usually of higher pressure then sea water system. If the leakage takes place in the jacket cooling water side or lubricating oil.

Procedure :
Ensued 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.

Flourescent Halo Test
Small leaks are extremely difficult to detect, specially the time availability is very less, will be difficult to get seawater cooling spaces dried out.
If the leakage is very small and time availability is less then follow the below procedure :
  • A small amount of fluorescent sodium crystals is dissolve in water within the spaces surrounding the tubes.
  • The tube plates are then viewed under a source of ultraviolet light.
  • Even very small leakage is sharply visible as a fluorescent hallo.

Soap Bubble Test
If the time availability is high and if the heat exchanger can be isolated, then carry out the following procedure :
  • Ensure the and covers are removed from the seawater 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 deducted, measure the inside diameter of the tube and find suitable Plugs the plugging.
  • For plugging the leaky tubes, plugs made of brass (same material as the tubes ) or plastic are being used on either end of leaky tube.
  • Plug should be driven securely so as to isolate it completely.
  • Carry out a leak test again to confirm that the leakage arrested.

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