What is the water horsepower requirement for a centrifugal pump achieving a flow rate of 550 gpm against a total dynamic head of 75 ft and a specific gravity of 1.2?

To determine the water horsepower (whp) requirement for a centrifugal pump, the formula used is as follows:

[ \text{whp} = \frac{Q \times H \times SG}{3960} ]

Where:

• ( Q ) is the flow rate in gallons per minute (gpm),

• ( H ) is the total dynamic head in feet,

• ( SG ) is the specific gravity of the fluid.

Given the values:

• Flow rate ( Q = 550 ) gpm,

• Total dynamic head ( H = 75 ) ft,

• Specific gravity ( SG = 1.2 ).

Now substituting these values into the formula:

[ \text{whp} = \frac{550 \times 75 \times 1.2}{3960} ]

Calculating this step by step:

1. Multiply the flow rate and head:

( 550 \times 75 = 41250 ),

2. Multiply by the specific gravity:

( 41250 \times 1.2 = 49500 ),

3. Finally, divide by 3960:

( \frac{49500}{3960} \approx 12