re: System Design Pressure Upstream and Downstream of a Pump
re: System Design Pressure Upstream and Downstream of a Pump
(OP)
HI,
I came across with a pump + Heat exhanger closed cooling system having the following service conditions in the flowsheet:
At the Pump Suction:
Normal: T= 140 F P = 10 psig
Design T= 200F P = 100 psig
At the Pump Discharge:
Normal: T=140F P = 90 psig
Design T=200F P = 145 psig
The max. pump shut-off head is 180 ft. Over-pressure protection is done by interlocking the main isolation valve with a pump drain valve.
What determines the design pressure? Is it provided by the pump manufactures? Shouldn't one use the design pressure at the pump discharge as a bounding value for the suction side?
Thanks
I came across with a pump + Heat exhanger closed cooling system having the following service conditions in the flowsheet:
At the Pump Suction:
Normal: T= 140 F P = 10 psig
Design T= 200F P = 100 psig
At the Pump Discharge:
Normal: T=140F P = 90 psig
Design T=200F P = 145 psig
The max. pump shut-off head is 180 ft. Over-pressure protection is done by interlocking the main isolation valve with a pump drain valve.
What determines the design pressure? Is it provided by the pump manufactures? Shouldn't one use the design pressure at the pump discharge as a bounding value for the suction side?
Thanks





RE: re: System Design Pressure Upstream and Downstream of a Pump
The maximum allowable suction pressure DOES NOT have to equal to the pump discharge pressure. You should find the pump's specification sheet or check with the mfgr (or better, both). Suction and discharge pressures may be different.
You should have a Pressure Relief Valve WITHOUT any interlock for hi pressure protection.
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RE: re: System Design Pressure Upstream and Downstream of a Pump
Your normal conditions indicate the differential pressure across the pump as 80 psig which is equal to 184 ft. This is beyond the shut off head.
RE: re: System Design Pressure Upstream and Downstream of a Pump
Going the Big Inch!![[worm] worm](https://www.tipmaster.com/images/worm.gif)
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RE: re: System Design Pressure Upstream and Downstream of a Pump
The system is recirculating heavy water, desnity is approx. 10% higher than water. To give a background, this is an exisitng system (25 yrs old) that need gate valves replacement. This system has a huge tank with heating elements, a pump, a HX, and the assoicated isolation gate valves. The function of this system is mainly for cooling of the heating elements. There are rupture discs (brust at 20 psig) mounted on the big tank for pressure relief. The heat tank is located upstream of the pump. When I was reviewing the process conditions for this system, it confused me seeing the design conditions for the pump.
I checked to pump curve, it shows a 250 ft total dynamic at zero flow. At normal operating conditon, it provides 180 ft and 940 L/s.
What factors determine the design pressure and temperature upstream of the pump?
Thanks again for your help
RE: re: System Design Pressure Upstream and Downstream of a Pump
Of course, 240 ft = approx. 100 psig for heavy water at the normal temperature. Is that how the design pressure is set upstream of pump?
RE: re: System Design Pressure Upstream and Downstream of a Pump
Did that answer the question?
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http://virtualpipeline.spaces.msn.com
RE: re: System Design Pressure Upstream and Downstream of a Pump
Geoffrey D Stone FIMechE C.Eng;FIEAust CP Eng
www.waterhammer.bigblog.com.au
RE: re: System Design Pressure Upstream and Downstream of a Pump
Going the Big Inch!![[worm] worm](https://www.tipmaster.com/images/worm.gif)
http://virtualpipeline.spaces.msn.com
RE: re: System Design Pressure Upstream and Downstream of a Pump
Thanks BigInch and others for the insights.