Figure 11-1. Pump graph.

A common application of a pump graph (Figure

11-1) is its use in determining the rate of flow, efficiency, and BHP,

given the total dynamic head in feet and operating speed of the engine in

RPM. Recall the definition of dynamic head--the height to which a pump

can push a column of liquid. Rate of flow is the most commonly desired

variable on the graph, and can be expressed in either GPM or barrels per

hour. At an engine speed of 1,800 RPM and total dynamic head of 160

feet, determine the following:

Rate of flow (GPM).

Efficiency (percent).

Brake horsepower (BHP).

To solve this problem, enter the graph on the Y axis at 160 feet of head.

Follow this line to the right until it intersects the head capacity curve

for 1,800 GPM. At this point, all answers are determined vertically up

and down.

To read rate of flow in GPM, drop down to the X axis and read the

answer 850 GPM.

To determine the efficiency, drop down to the efficiency curve

and read the percent efficiency in the right-hand margin (70 percent).

The BHP is similarly read. Drop down to the BHP curve for gasoline

and read the answer (35 BHP).

purposes, we use 0.8524 specific gravity diesel fuel.

12-100

QM 5099

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