4 replies to this topic

[Sherif Morsi]

I am reviewing some pump curves which are all based on water, i.e. Sp. Gr = 1.

 

The pump is specified for 1.6 sp. gr. fluid. The pump head is 20 m according to the vendor curves which gives us an output pressure of 

 

Sp. Gr x g x h = 1 x 0.0981 x 20 = 1.962 bar.

 

The required pressure output is 4 bar, so for water the required head is 40.77m. With simple math, if I were to calculate the pump head using the 1.6 Sp. Gr, can I say that the required head is 40.77 / 1.6 = 25.48?

So the equation would read 1.6 x 0.0981 x 25.48 = 4 bar?

 

Your feedback is appreciated

 

Sherif 

[thorium90]

I don't quite understand. The pump curve is based on SG=1 and the pump is "specified" based on SG=1.6? That doesn't make sense.

Also note that if the SG is different, you might require a different motor size or you might end up overloading your motor... If the pump is designed for a particular fluid, it might not be suitable for another fluid.

Edited by thorium90, 02 August 2015 - 05:54 PM.

[breizh]

Hi ,

This document may clear your doubt.

Good luck,

Breizh

[Sherif Morsi]

thorium90,

 

I meant the pump curves are flow vs. head and head is usually estimated in meters/feet of water.

 

Sherif

[PingPong]

head is usually estimated in meters/feet of water

No. Head is specified as meters LIQUID, irrespective what the s.g. of that liquid is (but assuming its viscosity is not much more than that of water).

 

So a centrifugal pump with a Head of 20 m will give a Differential Pressure of 2.0 bar with water (s.g. = 1),

or only about 1 bar with LPG (sg = ~0.5), or 3.2 bar with a liquid that has a s.g. of 1.6