Before jumping to any conclusions it is prudent to check where the leaks are from. It could be from the breach on the tube (a hole etc) or from the origination of small gaps between the tube plate and the expanded portion of the tube.
Procedure to be followed for leak detection/ finding in shell and tube type cooler:
- Drain water completely from drain valve.
- Remove water chamber
- Fill condenser shell with fresh water and apply air pressure or water pressure of 1kg/cm2 to the upper part of the shell.
- Dry up cooling pipe and tube sheet so as to locate leakages easily.
Steps to rectify the leaks of shell and tube type heat exchanger:
The procedure should to be based on the findings.
- A holed tube should be plugged from both the sides. The plugs can be of cork, wood, rubber, brass, or copper as supplied by the manufacturer. Care should be taken when plugging with the metal plugs, not to damage the tube plate.
- If the leaks are from the gaps between the tube plate and the tubes, slight flaring of the tube may help preventing the leaks however this flaring, if excessive will damage the tube plate and also the tube itself.
- Alternative methods are available by carrying out surface preparation and applying metal repair putty, like Devcon’s brush able ceramic repair putty.
FIG.: Different types of plugs
Note: In the above process, if the plugging of the tubes is about 10% the tubes have to be renewed.
Tube removal procedure shell & tube type cooler:
- Cut off both end of faulty tube by the drill 1.0 mm smaller than the outside diameter of the tube.Drilling length should be about 5.0 mm shorter than tube sheet thickness
- Collapse the tube end by chisel tool
- Knock out the tube by punch and tube push out tool