Operation Under Usual Conditions - TM-5-4320-242-140027

2-4. Operation Under Usual Conditions

(3) Flow rate.

Flow rate increases with

increased throttle control setting. It reaches maximum

a. General.

at full throttle (maximum governed engine speed of

(1) When the pump is in operation, check for

3600 rpm); and when cavitation occurs at impeller inlet.

normal instrument readings shown in figure 2-1.

(4) Cavitation. Cavitation will occur when

(2) The engine governor is adjusted to limit

there are air leaks in the suction side of the pump,

maximum speed to 3600 revolutions per minute when

suction lift is too high, or the suction end of the line is

pumping.

not sufficiently submerged to prevent whirlpools. It

(3) The throttle control permits selection of

produces an effect similar to a slipping clutch and a

power settings from idle speed (700-800 rpm) to

noise that sounds like loose pebbles ricocheting inside

maximum governed speed.

of the pump casing.

b. Operation.

CAUTION

(1) Starting.

Start the pump assembly,

Cavitation is harmful to the pump

paragraph 2-2.

assembly. Avoid at all times.

(2) Priming cycle. When the pump and hose

c. Performance Characteristics.

system are initially installed the priming charge is in

(1) Engine horsepower required to drive the

pump body; and the engine is started; the throttle should

pump varies with the weight of the liquid being pumped

be adjusted to 3300 rpm. The pump will operate for a

and the capacity or rate of pumping.

To avoid

short priming cycle period during which the pump is

overloading, adjust throttle control to maintain the

evacuating the air from the suction hose. During this

desired flow rate.

period it will not be pumping liquid.

(2) A composite pump performance curve is

CAUTION

shown in figure 2-4.

After pump has primed and is

a. Pump capacities are shown in

pumping, adjust throttle setting to

gallons per minute. Pump discharge pressures are

1800 rpm until discharge, hose

shown in pounds per square inch and in feet of head of

system has filled.

the liquid pumped.

CAUTION

b. Lines of constant brake horsepower

When suction must be primed and

represent the loading of the engine. The engine will

the discharge lines lie on a grade

give satisfactory life and performance when normal

considerably higher than the pump

operation does not exceed the continuous duty brake

and are full of liquid, follow the

horsepower for the speed at which it is operated.

procedures prescribed in figure 2-1

regarding priming check valve before

starting engine.

2-10