Sizing of Motor for Cent Pump with ARC
Sizing of Motor for Cent Pump with ARC
(OP)
I am facing a Problem in selection of Motor rating for High pressure ~150 bar boiler feed water pump.
the pump requires Autostart facility i.e. its discharge valve will be in open condition at time of starting and also it has an Auto Recirculation Valve (ARC) in discharge line for minimum flow bypass(for pump safety.
Should the selected motor have rating sufficient to cater the 'End of the curve flow' of the pump or not.
Or speaking the other way round - will the pump operate at End of Curve point anytime?
the pump requires Autostart facility i.e. its discharge valve will be in open condition at time of starting and also it has an Auto Recirculation Valve (ARC) in discharge line for minimum flow bypass(for pump safety.
Should the selected motor have rating sufficient to cater the 'End of the curve flow' of the pump or not.
Or speaking the other way round - will the pump operate at End of Curve point anytime?





RE: Sizing of Motor for Cent Pump with ARC
BigInch
-born in the trenches.
http://virtualpipeline.spaces.msn.com
RE: Sizing of Motor for Cent Pump with ARC
Something else to consider, if this pump is an auto-start, does that mean it's set up to come onstream automatically with another pump that's already running? If that's the case, regardless of an open discharge valve, the back pressure in the discharge system against the pump's discharge check valve (or even the ARC valve) will typically be enough to keep the pump from running out beyond the minimum flow rate until it's stabilized. The only time you have to really worry about runout in an auto-start scenario is if the pump is starting up against an un-pressured system, which isn't likely without operator assistance anyway.
Long story short, if your startup procedures work properly, the pump should never run out on it's curve. But that's a big 'if' and a fairly reasonable expenditure for that extra 10% horsepower availibility if it's required.
RE: Sizing of Motor for Cent Pump with ARC
Thanks for he useful information. I would like to eloborate few more things
point 1.
There r 2 pumps 1 working and 1 standby (not in parallel operation anytime)
point 2.
Standby pump shall autostart as soon as the working pumps trips - due to some reason.
it has auto reciculation vale in pump discharge for pump safety.
point 3.
During plant startup operator assistance would be definitely provied but not in case if the pumps starts in above mentioned fashion (point no 2).
point 4.
rated BkW is 900kW and end of the curve(EOC) point power requirement is 1136 kW.MOtor size for EOC requirement
is 1150kW.
Question in my mind is that- when standby autostarts will its operating point anytime shift away from rated point towards EOC and hence motor will have to be sized for catering EOC power requirement or not??
RE: Sizing of Motor for Cent Pump with ARC
BigInch
-born in the trenches.
http://virtualpipeline.spaces.msn.com
RE: Sizing of Motor for Cent Pump with ARC
I have found out the minimum pressure that the pump will see
it is 145 bar and the power corresponding to this point is 950 kW
Now at rated pt power is 917 kw, that means as per project standards the minimum motor rating required is 1.1 X 917 = 1008 kW
Can i select mator rating considering maximum power requirement as 1008 kw in place of earlier 1136 kW.
Please advice.
RE: Sizing of Motor for Cent Pump with ARC
There is no need to consider any flowrate past the maximum flowrate that you can have, due to system conditions, flow or pressure control, or any other operating limitation.
http://virtualpipeline.spaces.msn.com