Heat Exchanger Choked in PLC Liquid Cooling System

Introduction 
There’s a roaster unit from where we get so2 gas in form of byproduct & this so2 processed to acid generation plant with mixture of atmospheric air in the line. This air produces required draught inside the converter & provides good volume of SO2 inside the converter. 

System Problem : There’s one ABB PLC which control the air blower speed. This plc is basically having liquid cooling system which makes its desired temperature within ambient temperature. The coolant used for this purpose is DM water in its heat exchanger unit. Sometimes, this heat exchanger found choked which further trip the blower & make production loss in acid generation plant.

Root Cause: Dm water having PH ratio more than 9 which under heating temperature start scaling inside the heat exchanger tube. After 15 days of cycle, plc starts tripping.

Solution: There was a cooling tower line near by the blower which having pressure almost 3 to 5 kg/cm2, we took a tap of ¼ inch in this cooling tower line & a tube connected with this line. The return line from the heat exchanger further connected to cooling tower return line.

Conclusion : Cooling tower having water temperature 25 to 28 degree C with a pressure of 3-5 kg/cm2 stopped scaling inside the tube of heat exchanger & cooling water out temperature was almost 30 degree C