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NPSH for plunger pump

NPSH for plunger pump

NPSH for plunger pump

(OP)
Hi
please what is NPSH for plunger pump have  the folloing data sheet:
LIQUID PUMPED:Condensate
SP. GR. @ PT:0.071
VAPOR PRESS. @PT:0.96
VISCOSITY @PT:0.66
NORMAL ATMOSPHERIC PRESS.: 0.96 bara
MAXIMUM CAPACITY @ PT: 2 m3/hr
DISCHARGE PRESSURE: 65 bara
SUCTION PRESSURE: 0

please to inform me the equation which determine the required NPSH

regards

 

RE: NPSH for plunger pump

NPSHR is something you can only get from the pump manufacturer. If you give us pump model and manufacturer or perhaps plunger diameter and stroke length, we will perhaps be able to make a guess (with some risk) but nobody here can calculate NPSHR of your pump.

RE: NPSH for plunger pump

(OP)
thanks
but can I calculate NPSHA


regards

RE: NPSH for plunger pump

Yes, of course you can. But you need some more information about the suction side installation to do this.

You can search here in the forum or just "NPSHA calculation" through Google and you will find all required information plus calculation formula.  

RE: NPSH for plunger pump

In order to evaluate the cavitation potential for a piston pump, you have to know the stroke rate and suction line length.  With a piston pump, the acceleration head can be quite significant.   

Johnny Pellin

RE: NPSH for plunger pump

Need RPM too...

RE: NPSH for plunger pump

(OP)
thank you for your co-operation, but please what is the exact equation?


regarsd
 

RE: NPSH for plunger pump

Does "Bernouli" ring a bell?

Patricia Lougheed

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RE: NPSH for plunger pump


You may find an answer to your queries in Pump Handbook McGraw-Hill, by Karassik et al., in the chapter: Displacement Pumps.

BTW, SP Gr. seems to be a typing error.

Good luck.

RE: NPSH for plunger pump

(OP)
thanks for all

RE: NPSH for plunger pump

For NPSHA calculation see:
http://www.engineeringtoolbox.com/npsh-net-positive-suction-head-d_634.html

What needs to be added to the NPSHA calculation formula for centrifugal pumps is the suction side acceleration head which is (L x v x n x c)/(k x g) where L is the suction pipe length, v is the fluid velocity, n is the stroke rate of your plunger pump, c is the pump factor (0.066 for a triplex pump), k is a correction factor for laminar flow (= 1.5) and g is the acceleration of gravity. The result must be deducted from the NPSHA result for centrifugal pumps.
 

RE: NPSH for plunger pump

Mical's equation is ok, but if you operate near the limit of suction head, or are comparing different pumps, you need to look at details of the pump construction, finding peak velocity or acceleration (depends on bore, stroke, rpm) through the smallest flow area (typically check valves).  Peak velocity is affected by no. of cylinders, with 3, 5, 7 etc. giving better performance than 1, 2, 4, 6.

RE: NPSH for plunger pump

Its kinda' faint, but I don't see where you've included acceleration head there.  Looks to be for centrifugals only.

RE: NPSH for plunger pump

You mean velocity head.  It could be included on the supply side,however for many systems,it would be too small of a value.  There is a velocity head at the pump inlet in my attachment.
Same first law would apply on the inlet side of the plunger pump for only about half of its cycle.

RE: NPSH for plunger pump

No, he meant acceleration head and it is usually not a small value for multiple plunger pumps unless they have a suction side flow stabilizer (pulsation dampener) - and most of them haven't.  

RE: NPSH for plunger pump

Thanks for the info. Biginch,micalbrch and ione

RE: NPSH for plunger pump

reminds me of the 3 musketeers.
"For Ione and all."

RE: NPSH for plunger pump

This motto sounds better: "All for Big and Big for all"

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