4 replies to this topic

[krishnamurthy]

I have a doubt, if a water pump is used for hydrocarbon service ,then what would be the discharge pressure of the water pumps, higher or lower?. Please explain me with reasons. 

[latexman]

What kind of pump?

 

For a centrifugal pump, it will produce the same "head" for both water and HC.  So, just convert that head to the hydrostatic pressure of the HC using the density of the HC in the equation we should all remember:

 

P = density x g x H

[breizh]

Hi,

Probably good to read.

Breizh

[shvet1]

In addition to above

For centrifugal pumps see ANSI/HI 9.6.7 or ISO/TR 17766

[snickster]

As indicated above centrifugal pumps produce velocity head not pressure.  More specifically the rotating impeller imparts a velocity to the fluid proportional to the tip speed.  The kinetic energy (in feet of head) of the fluid is proportional to the velocity exiting the impeller in accordance with KE=V²/2g  (where V is velocity in feet per second and g is 32.2 ft/sec² gravitational acceleration constant).  After leaving the impeller the velocity head is converted into pressure head in the volute so that:

 

P(144)/density=KE  (where P is pressure in PSI, density of fluid pumped is in pounds-weight per cubic feet = 62.4 for water, and KE head is in feet of liquid).

 

So the same pump operating at the same RPM and same impeller size will produce the same velocity of fluid exiting the impeller, same velocity head and same Kinetic Energy.  However when converted to pressure, the pressure will be greater for the greater density fluid in accordance with  P=(KE in FEET)(density)/144.  After conversion to pressure head the fluid head is now the same value in feet, but it is pressure head not velocity/kinetic energy head.

 

Typically pumps for pumping hydrocarbons in the process industry are built to API 610 (most expensive) or ASME B73.1.  Water pumps are produced to lesser stringent standards that are not used for pumping hydrocabons normally.

Edited by snickster, 11 April 2023 - 04:26 PM.