industrial boiler question

Joe V_2

We have three, 600 HP boilers feeding a common header.  The boilers are synced to rotate each day. The internal temperatures are monitored in case a non operating boiler becomes too cold so the burner kicks in to warm it up.

We just noticed that the boiler water feed valve is modulating on one of the non operating boilers.  The water in the sight gage is rising and falling and correlates with the feed water valve.  We manually turned on the boiler to see if steam comes out of the stack but it didn't.  When we turned it off, the valve stopped modulating for a couple hours and then started modulating again.  The blow down valves are not leaking.  Any ideas on what might be happening in there?  We operate at 130 psi.  The other non operationg boiler does not do this.  Thanks for any help!

nicholas bonham-carter

over-filling

could it be that the fill valve [on that boiler] is not closing all the way?  after all it seems as though only this 1 problem boiler shows the symptom. 130 PSI is quite a pressure against which to operate. also, could it be that the 130 PSI pressure has been occasionally exceeded, causing the fill valve mechanism to open at the wrong time?

we always welcome steam problems here, however the usual problems with pressure are usually measured in OUNCES, so we are a little out of practice with the big boy boilers, but stll interested in being of help!--nbc

Joe V_2

Thanks

We closed the feed water gate valve and turned off the pump.  The water level dropped to just above LWCO over night so we're guessing a small leak in an upper fire tube that seals when firing because waterlevel is steady as a rock when boiler is in lead.  The leak must be small small enough that we can't see steam coming out of the stack.  We'll open it up at our next opportunity to inspect.