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We are operating cooling tower with circulation rate of about 10,000 m3/hr. Recently a case of oil ingress occurred through one of the coolers in a process unit. This oil ingress resulted in increasing the cooling water supply temperature from 29 degC to about 36 degC. Although oil content in the cooling tower has been reduced to below 10 ppm by appropriate chemical dosing the problem of high CWS temperature still persists. Cooling tower fans and CW distribution through fills have been checked and found to be working fine. Can anyone suggest some measures for reducing this CW supply temperature back to normal?
 
Answers
13/11/2019 A: Bruce Carr, Suncor Inc, bcarr@suncor.com
I take it that this is a wooden structure cooling tower..... It doesn't make sense that the temperature would still be high unless the oil and chemical additives have greatly changed the surface tension of the water preventing it from forming proper sized droplets... (I'm grasping here).... Cooling towers are the most simple in principle of any equipment..... 75% of the cooling comes from evaporation... the oil and chemicals must be preventing this in some way.... I would suggest lowering your cycles of concentration by blowdown and making up with fresh water.
12/11/2019 A: Raghavendra Sangam, Libra Techcon Ltd., rsangam0504@yahoo.co.in
Ensure that the CWS temperature measurement is correct, which was disturbed due to this event. Measure it at various points in the loop and confirm. Also, confirm the oil ppm measurement is consistently below the limit and not a one time measurement. Check if the fans speeds or blade angles were changed/disturbed during the shutdown after the upset. (were the fills removed and physically checked for cleanliness after the event?) If the CWS supply temperature has gone up to 36 degC then there must be upsets/changes in the process at other consumers. Check for those indications. If so, then the entire system needs thorough cleaning.