Dear Mohamad,

Please read the following text:

Calculating Horsepower

Horsepower is a measurement of the amount of energy necessary to do work. In determining the horsepower used to pump water, we must know the:

1. pumping rate in gallons per minute (gpm), and

2. total dynamic head (TDH) in feet.

The theoretical power needed for pumping water is called water horsepower (whp) and is calculated by:

(equation 1)                       whp = gpm x TDH (ft)/ 3,960

Since no device or machine is 100 percent efficient, the horsepower output of the power unit must be higher than that calculated with equation 1. This horsepower,

referred to as brake horsepower (bhp), is calculated by:

(equation 2)                       bhp = whp/ (pumping plant efficiency)

Total Dynamic Head (TDH)

TDH may be viewed as the total load on the pumping plant. This load is usually expressed in feet of “head” (1 psi, or pound per square inch = 2.31 feet of head). TDH can be calculated with the following equation:

(equation 3)                TDH = (static head) + (friction loss) + (operating pressure) + (elevation change).

For more details on this topic, please see the publication contained in the attached file.

Hoping this will be helpful,

Rafik