Patterson HSC, Operation And Maintenance

Page: 13 / 16

10

Speed too low – indicated by low pressure on discharge.

Valve closed – indicated by high discharge head.

Impeller completely plugged up – indicated by low discharge pressure.
Abnormally Small Quantities Delivered

Air leaks in suction pipe or stuffing boxes.

Speed too low.

Discharge head higher than anticipated.

Impeller partially plugged up.

Obstruction in suction line.

Mechanical defects: Impeller damaged, casing or seal defective.
Insufficient Pressure

Speed too low. Might be caused by low voltage or current characteristics different from nameplate
reading on the motor.

Air in water will cause the pump to make a cracking noise.

Mechanical defects: worn casing rings, impeller damaged, defective casing or seal.
Intermittent Operation

Leaky suction line.

Water seal plugged (hence, a leaky stuffing box).

Suction lift too high.

Air, gas or vapor in liquid.
Pump Overloads Driver

Speed too high.

Head lower than rated, hence, pumping too much water. (This is valid for low specific speed pumps).

Mechanical defects: stuffing boxes too tight, shaft bent, rotating element binds.

Rubbing due to foreign matter in the pump between the case ring and the impeller.