Low Pressure Boiler Feed System
Low Pressure Boiler Feed System
(OP)
I have an existing low pressure boiler feed system that is becoming problematic (almost from the start). It is not even 1 year old and we have already lost 2 pump seals and one feed water solenoid.
The system consists of four (4) 4,000 MBH boilers, all fed from a single feed pump (with standby pump). Each boiler has a 2-position solenoid valve that cycles to maintain water level.
At first, the pump did not run continuously, but the demand was causing it to cycle every few seconds. So, we install a small bypass back to the feed tank and ran the pump continuously. This caused an increase in the water hammering effect to the point where we had to provide additional bracing on the feed line. Each boiler has a water hammer arrestor, but that doesn't seem to be helping much.
It has been suggested that this setup is poor and is probably the cause of the pump seal failures. It has also been suggested to install either slow acting solenoids or some other modulating control.
This fix will be an out-of-pocket correction, so I need to be economical. Any ideas on how to best deal with this problem?
The system consists of four (4) 4,000 MBH boilers, all fed from a single feed pump (with standby pump). Each boiler has a 2-position solenoid valve that cycles to maintain water level.
At first, the pump did not run continuously, but the demand was causing it to cycle every few seconds. So, we install a small bypass back to the feed tank and ran the pump continuously. This caused an increase in the water hammering effect to the point where we had to provide additional bracing on the feed line. Each boiler has a water hammer arrestor, but that doesn't seem to be helping much.
It has been suggested that this setup is poor and is probably the cause of the pump seal failures. It has also been suggested to install either slow acting solenoids or some other modulating control.
This fix will be an out-of-pocket correction, so I need to be economical. Any ideas on how to best deal with this problem?





RE: Low Pressure Boiler Feed System
If you can give flowrates, pressures, line diameters and lengths, elevations, with valve type and locations, pump characteristics, etc. it might help in identifying some possible causes as to how the transients originate and the best way to calm them down.
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RE: Low Pressure Boiler Feed System
RE: Low Pressure Boiler Feed System
RE: Low Pressure Boiler Feed System
RE: Low Pressure Boiler Feed System
RE: Low Pressure Boiler Feed System
RE: Low Pressure Boiler Feed System
RE: Low Pressure Boiler Feed System
RE: Low Pressure Boiler Feed System
No info = no solution
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RE: Low Pressure Boiler Feed System
I just noticed a descrepancy on my pump. According to the curve, it is rated at 59 GPM @ 20' (my submittal says 20 psig, but it is written in by hand). The curve must be correct, so I probably have about 16 GPM @ 20 psig. My boilers are running at 11 psi, so I probably have enough flow.
RE: Low Pressure Boiler Feed System
Have a look at the third bubble from the left. At 16 GPM and 20 psig, I'd put you're operating point right smack in the middle of that third bubble.
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RE: Low Pressure Boiler Feed System
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RE: Low Pressure Boiler Feed System
The recirc line from your feedpump should discharge to the feedwater tank, not the pump suction.
RE: Low Pressure Boiler Feed System