condensate tank noises

phil_27

I was called to a job yesterday on a steam process boiler. The operator informed me that the boiler had failed on low water and he could not restart it! Upon arrival , I found that the operator had drained the condensate storage tank (about 200 gallons) because the tank was making loud banging noises. I filled the tank and the boiler and noticed that the condensate pump can remove more water from the tank than the makeup line can supply! But, my problem doesn't end there! This Boiler is rated for 125# and they are operating at 55#. The pumps were sized for 350ft head. Upon reaching the 55# the boiler goes to low fire, but the tank starts knocking violently! I believe the boiler water is going backwards through the check valve at the boiler inlet and the check at the pump into the tank. Why is this happening? The operator says the check valves have already been replaced 3 times in the past year. What is causing the "Flappers"  to stay open when the pump stops?

DanHolohan

Phil,

is the tank pressurized or open to atmosphere?



Is there a throttling valve on the pump?

kevinj_4

heat?

Also is this tank heated???

Did you valve out the feed line to be sure it was backing out of the boiler??

joe lambert_2

Check Valve

I have seen this a lot.  Flowing back through the check valve once the pump shuts off, then the boiler water flashing in the condensate tank causing hammer.



I recommend a high quality SOFT SEATED check with a spring.  I have even put two in series sometimes.  Look at the DFT SCV series for a start. (I am not affiliated with DFT).