typical: BFP in recirculation?

Kindly, any one help that we have recently erected Boiler feed pump and we want to commissinon the pump in recirculation mode as the other system is not ready. The path is BFP to Deaerator through ARC ( Modulation type). Whether is this advisable to commission the pump? Whether to close the deaerator vent or open? Pump can develop 200 bar pressure and temp rise across the pump is 11 deg.c. Just we want to run the pump in recirculation without steam inlet to deaerator. Can anybody suggest? How to go about it?

thanks

mah99

 

[vanstoja]

At what flow fraction is the head 200 bars and the temperature rise 11 degrees C and what is the flow fracton at recirculation flow? If your numbers are for pump rated best efficiency flow (ie, flow fraction=1.0=100%), and recirculation flow is around 40% or less, you're asking for a lot of trouble running such a high head-per-stage pump so far off its design rating presuming that it is a single-stage pump.The temperature rise will go way above 11C and if there are any flow instabilities at the recirc flowrate, such as rotating stall, you may risk serious damage to the impeller. If you've got a tight cutwater clearance then severe pressure pulsations could, in the worst case, blow pieces of shrouding out of your impeller. This has already happenened for some high head-per-stage pumps (approaching 1000 ft. head). US nuclear facilities pumps have, in recent years, gone away from running standby or emergency-use pumps in a recirc mode periodically, just to determine that they are runnable, because of the damage that has been found to result from far off-design operations. vanstoja

 

[mah99]

I am sorry i have not given full details of pump. It is a 14 stage Boiler feed pump. Its maximum flow 20 m3/hr, which has got one booster pump at the inlet. Effi. 40% at above capacity. We want to run the pump only in recirculation fully with 20m3/hr to deaerator. Pump suction also from Deaerator. How much time we can run the pump in this mode/path. Whether this is advisable? We want to stop when water temperature reaches to 90 deg.c. There is no pegging steam to deaerator right now during this mode.
kindly guide me anyone?

mah99