Many don't understand how boilers are rated.  It is called a from and at rating and is based on a feed temperature of 100 C.  These temperatures cannot be practically maintained.  Therefor feed temperatures lower than 100 will reduce the boiler rating as feed temperatures are dropped.  Secondly, boilers are rated in kg per hour.  So a boiler rated at 6000 kg per hour will only produce 100 kg per minute.  If the steam demand exceeds this to say 150 kg in a minute then the boiler will prime and carry boiler water with it.  This is caused priming.  If the boiler pressure drops the same can happen.  The velocity of steam changes dramatically between 7.5 and 5.5 bar so if the pressure drops in the boiler then the speed at which steam can reach its use point is slower and can cause the boiler to prime. Foaming is caused by the things the other comments have been made.  The greatest cause of foaming is high TDS or high caustic levels.  If the pretreatment plant is not working properly, then hardness enters the boiler, which will increase the suspended solids within the boiler.  Once the suspended solids level exceeds a certain level, the water stops acting like water and acts more like a fluid with solids.  Then the boiler will foam.

Published July 30, 2018 12:12 by Don Sharpe