Horse-power of Pumps

The horse-power required for the pumps (HP) is given by  :

                                                          HP = WH/75

where,            W = Weight of water in kg per second, and

H = Total head in meter.

This is known as Water Horse-power (WHP).

Brake horse-power (BHP) is calculated by dividing Water Horse Power with efficiency of pump (E).

                                                         BHP = WH/75 E

In the above equations, total head (H) is normally obtained by following equation:

                                                           H = h + h_f

where, h = total static head or difference in level between the lowest water level in the well and full supply level of the tank whereas h_f = Head lost due to friction.

                                     hf   = flv²/2 gd (modified Darcy-Weibach formula)                                          . . . (4.1)

f = Coefficient of friction,

l = Length of pipe in meter,

v = Velocity of flow in meter per second,

g = Acceleration due to gravity = 9.81 m/sec²,

d = diameter of pie in meter, and

Q = Discharge in m3 per second.

                                                       Q =     (πd²/4). V                                                                              . . . (4.2)

Now h_f can be calculated as

                                               h_f  =(fl/2×9.81×d)× [4Q/ πd²]²