2 replies to this topic

[arman77]

I need to do a calculation for positive displacement (PD) pump (single acting piston pump). NPSH required for a PD pump is calculated in the same manner as for a centrifugal pump, except that additional allowance must be made for the requirements of the reciprocating action of the pump. The additional requirement is termed acceleration head. This is the head required to accelerate the fluid column on each suction stroke so that this column will, at a minimum, catch up with the receding face of the piston during its filling stroke. The formula to calculate acceleration head (from GPSA) is
Ha = L x v x n x C/k x g
Where
L Length of suction pipe (m)
v Liquid mean velocity (m/s)
n Speed of rotation (rpm)
C Reciprocating Pump Acceleration Head Factor
k Reciprocating Pump Acceleration Head Factor
g Acceleration of gravity (m/sec²)

My question is, how to calculate n (rpm) and after calculating the acceleration head do you add it to the NPSHmin?
Any help will be very much appreciated.

[fallah]

I think n would be strokes/min and acceleration head enters NPSH calculation with minus sign.

[ankur2061]

Arman,

Have a look at an earlier post:

http://www.cheresour...__1

Also have a look at the following:

http://www.pump-zone...ation-head.html

There are two pages in the above mentioned article with a solved example in the 2nd page.

Regards,
Ankur.