Sunday, April 5, 2020

Locating leak in heat exchangers

Shell and tube cooler

The heat exchanger is first isolated from its systems and after draining the sea water and removing the end covers or headers to expose the tube plates and tube ends , an inspection is made for evidence of liquid flow or seepage from around tube ends from perforations in the tubes . The location of small leaks is aided if the surfaces are clean and dry  . The fixing arrangment for tube stack should be checked before removing covers or headers to ensure that the liquid inside will not dislodge the stack . This precaution also underlines the need for isolation of a cooler from the system.

To aid the detection of leaks in large cooler such as main condenser , in which it is difficult to get the tubes dry enough to witness any seepage. It is usual to add a special fluorescent dye to the shell side of the cooler. When UV light is shown on to the tubes and tube plates leaks are made visible because the dye glows.

Plate type cooler

Leaks can be found by visual inspection of the plate surfaces or they are cleaned and sprayed with a fluorescent dye penetrate on one side . The other side is then viewed with the aid of an UV light to show any defects.

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