High Pressure Boiler Feed Pumps
High Pressure Boiler Feed Pumps
(OP)
Is anyone aware of why a multi stage boiler feed pump (providing water to a drum boiler) operating at 350 degree suction temperature, 140 PSI suction pressure, 3600 PSI discharge pressure at 5200 RPM would not have a low suction pressure trip or a low supply tank level trip?





RE: High Pressure Boiler Feed Pumps
pay me now or pay me later!
pumps in critical service should have alarms and safety shutdowns to prevent catastrophic failure of equipment/systems.
low pressure trip/shutdown - yes; as the liquid (boiler feedwater) will flash (evaporate) to steam upon a reduction in pressure.
low drum level, the objective is to avoid a potential equipment failure and/or advise the operator that an abnormal condition exists. a pump not pumping a fluid at those conditions would not be prudent.
-pmover
RE: High Pressure Boiler Feed Pumps
RE: High Pressure Boiler Feed Pumps
I know why you should have protection, my question is Does anyone have any reasons to design a system without protection?
Thanks
RE: High Pressure Boiler Feed Pumps
The suction supply is from an pressurized elevated tank (deairator)which does not have any trips for the feed pump. The number of pump stages varies by manufacture.
Thanks
RE: High Pressure Boiler Feed Pumps
If the sole source of supply for the pump is the plant's deaerator and if the deaerator has level control/indication and alarm, then the function of the level control is to protect the feedwater pump NPSH
If you get a chance to go back into the history of power plant design, you would find out that the FW pump suction piping is subject to a lot of transients and has been the subject of many ASME piping design papers and discussions.
This suction piping is subject to extreme "fluid inertial" loadings during startup and shutdown as well as during deaerator upset conditions. The physical design of this piping is for minimum pressure drop, minimum retention volume as well as for internal transient pressure surge conditions......In the words of my twelve year old daughter...."its special"
I suspect that it may be much more reliable to control the pump NPSH via the deaerator level than it would be by alarming/recording a pressure that may vary considerably.
My opinion only
MJC
RE: High Pressure Boiler Feed Pumps
As in his other responses, MJCronin has shown wisdom and experience that should be heeded.
With the current trends in highly automated instrument and control systems, it is very easy to wind up with needlessly redundant alarm points.
RE: High Pressure Boiler Feed Pumps
I agree with all the responses, that is not the question.
The question was - Is anyone aware of a reason/design that would not include any feed pump trips?
RE: High Pressure Boiler Feed Pumps
Check through your system to see whether there are other alarm and trip points that functionally provide the protections that you think are needed for the BFP.
RE: High Pressure Boiler Feed Pumps
RE: High Pressure Boiler Feed Pumps
while not familiar with your particular situation/design; the short answer is no. the only reason (not a design issue!) i can think of for not including any feed pump trips is a cost issue. which by the way is not a technical issue - in my mind.
you have been provided ample justification for designing trips in bfp systems and sound reasoning by mjc. of course, the choice is yours to take heed.
-pmover
RE: High Pressure Boiler Feed Pumps