KIRLOSKAR CHILLERS PRIVATE LIMITED
A Kirloskar Group Company IOM-KAC-ENG - Page 33
4.2.1.2. Evaporator
The evaporator is of the direct expansion shell-and-tube type U bundle design, the tubes are
precisely expanded into the tube-sheets to form leak tight joints. In dry expansion type
evaporators, refrigerant flows through the tubes and water flowing through the shell over the
tubes. Normally no service work is required on this type of evaporator.
4.2.1.3. Testing Of Evaporator Tube Leaks
There may be instances where a tube leak in evaporator may result in refrigerant leak into the
waterside of the system or vice versa depending on the pressure levels. The tube leak may be due
to any of these reasons:
i) Improper tube expansion
ii) Freeze failure / impingement of foreign solid particles
Once the tube leak is established in evaporator, the old tube shall be plugged. Follow the steps
involved in plugging a failed tube:
i) Stop the unit.
ii) Drain water completely.
iii) Isolate the evaporator from the system.
iv) Open the refrigerant head covers and close the water nozzle with dummy flanges.
v) Gradually increase the pressure level with the help of dry nitrogen on the shell side and check
for the probable leak at the tube joints.
vi) The tubes are mechanically expanded to the tube sheets at the ends. Identify the leaking tubes
and gradually reduce the pressure on shell side.
vii) In cases where only one or two tubes leak, the problem can be solved by plugging the tube at
both ends. If no of failed tubes are more then, it is recommended to replace complete evaporator.
viii) Reassemble the evaporator, perform the leak test with dry Nitrogen gas and once the
exchanger passes pressure test, vacuum the evaporator, break vacuum with refrigerant and hook
up the evaporator with system.
CAUTION: THE BOND PRODUCED BY EXPANSION MUST BE
REFRIGERANT TIGHT. THIS BOND SHALL BE PRODUCED BY
APPLYING LOCKTITE (GRADE 638) OVER THE OUTER SURFACE OF
THE TUBE AND ROLLING IT INTO THE TUBE SHEET.
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