Page 23 - Know and Understand Centrifugal Pumps

Know and Understand Centrifugal Pumps

Where: H = head P = psi d = density

Pressure can be converted into head with the following equation:

2.31 x Pressure psi
Head@. =
sp.gr.
Where: H = head in feet psi = pressure in pounds per square inch
2.31= conversion factor sp. gr. = specific gravity

Head converts to pressure with the following formula:

Head@. x sp.8~
Pressure psi =
2.31

Specific gravity

Specific gravity is the comparison of the density of a liquid with the
density of water. With pumps, it is used to convert head into pressure.
The specific gravity formula is:

Density Liquid
Sp.Gz =
Density Water
The standard for water is 60°F at sea level.
Water is designated a specific gravity of 1.0. Another liquid is either
heavier (denser) or lighter than water. The volume is not important as
long as we compare equal volumes. The specific gravity affects the
pressure in relation to the head, and it affects the horsepower
consumed by the pump with respect to pressure and flow. We’ll study
this in depth later.

Pressure measurement

Pressure exists in our daily lives. At sea level the atmospheric pressure is
14.7 psia. This is the pressure exerted on us by the air we breathe. If we
should remove all the air, then the pressure would be zero.