Pumps can be operated at a wide range of speeds in order to compensate

for variations in the pumped product's specific gravity, temperature, and

the pipeline topology. The speed at which the pump is operated also

determines the efficiency and therefore the cost of operation. To

effectively direct a pumping operation you must be able to balance all

the operating parameters of the pumps which is accomplished by the use of

pump graphs.

A pump graph is constructed to show feet of head, flow rate in gallons

per minute (GPM), and barrels per hour. Pumps are equipped with gauges

that register the suction and discharge pressure in pounds per square

inch (PSI). Therefore the operator must be able to convert PSI to feet

of head to determine the flow rate and efficiency of the pump.

2. 31*xPSI*

The equation for converting PSI to feet of head is

.

2.31 is a constant based on a column of water at 60 degrees Fahrenheit, 2.31 feet high and measuring 1

inch by 1 inch. 2.31 feet of head of water at 60 degrees Fahrenheit equals 1 PSI. One foot of head is equal

to 0.433 PSI (1 divided by 2.31). By using the specific gravity of different fuels in the equation the operator

can determine the difference in PSI.

The pressure at which it is being pumped is 325 PSI. Using the

following equation, it is calculated that the feet of head is 909:

2.31*x*325

.

0.8254

The operator knows the pump can overcome 909 feet of head.

The equation for changing feet of head to pressure is P

.

2.31

with a specific gravity of 0.8254 and needs to know the pressure which

must be maintained. Using the equation:

P = pump

H = Head

2.31 = constant

SPUR = specific gravity

909 *x*.8254

325 *PSI *.

2.31

The normal head capacity of a pump station is the total head against

which it will pump at the most efficient operating point for example, the

design speed of the pumping units. Revolutions per minute (RPM) must be

12-98

QM 5099

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