3 replies to this topic

[chsnoopie]

Hi,

Can anyone explain why do we normally have the 1.25 factor in the following equation?

Shutoff Pressure=Max suction pressure + (1.25 x Differential Pressure)

 

Is it something related to the hydrotest?

[fallah]

_Hi,

 

_{That equation is to be used to estimate the pump's discharge pressure at no flow, just when the pump's shut off pressure isn't available. Please note that the Differential Pressure in that equation is the pump head at design point and to find the pump head at shut off it should be multiplied by a factor of 1.2-1.25. This factor covers the head rising from design point till no flow conditions due to moving to left hand on the pump curve in most cases and nothing to do with the hydrotest pressure...}

_{Of course, when the pump curve would be known, the estimated shut off pressure should be checked with the actual head of the pump at no flow condition.}

Edited by fallah, 26 June 2013 - 03:12 AM.

[shan]

It is true for centrifugal pump only.

[fallah]

shan,

 

O.K, good point, thanks...