Feed-water Heater

Heaters are part of power statian for increase efficiency cycle. There are two kind of heaters, low pressure and high pressure heater.

Low pressure heaters is heating dischare condensate line to de-aerator / feedwater tank and high pressure heater is heating feedwater line from feedwater tank to economizer.

Other words we can say low pressure heaters are actually low pressure about 15bar from discharge condensate pump and high pressure heaters are actually high pressure from discharge boiler feed pumps about 190bar for unit capacity around 600MW.


Heater is heating from turbine extraction steam and we can say the cycle efficiency can increase by easy explanation as picture below that useful energy reduce but the losses also reduce more.

















































This post only describe the most of problems at high pressure heater:
Tube leak at shell and tube heater makes low performance of heater. If the leak is going worst, the level of condensation can not controlling anymore by level drain control valve and the heater by-pass valve will be open.


If we found heater #7 low of performance, perhaps the tubes get leak, heater #7 by pass valve passing or also heater #5 & #6 passing and orifice continuous venting line blockage.

Orifice continuous venting line to de-aerator when normal operation for release un-condensable gas and we can measure for DO (dissolve oxygen) content at feed-water system.


Once happen DO get high while normal drain of heater #7 get problem and we should open emergency drain. Un-condensable gas which not maximum release to heater #7 orifice will down to heater #6 and get opportunity again to release through heater #6 orifice. But if the uncondensable directly goes to emergency drain to feed-water tank, the indication of DO at feed-water system can be increase.

When heater #6 out of service and we will put back it into in service, sometimes condensate water trap and can not move down to heater #5. It can be avoided by open heater #6 extraction steam valve first and then open heater # 5 extraction steam.
While start up process, orifice by pass start up valve should be open to reduce load of the heater.