CENTRIFUGAL PUMP OPERATION
The important information in this chapter is summarized below.
Centrifugal Pump Operation Summary
There are three indications that a centrifugal pump is cavitating.
Fluctuating discharge pressure and flow
Fluctuating pump motor current
Steps that can be taken to stop pump cavitation include:
Increase the pressure at the suction of the pump.
Reduce the temperature of the liquid being pumped.
Reduce head losses in the pump suction piping.
Reduce the flow rate through the pump.
Reduce the speed of the pump impeller.
Three effects of pump cavitation are:
Degraded pump performance
Excessive pump vibration
Damage to pump impeller, bearings, wearing rings, and seals
To avoid pump cavitation, the net positive suction head available must be greater
than the net positive suction head required.
Net positive suction head available is the difference between the pump suction
pressure and the saturation pressure for the liquid being pumped.
Cavitation is the process of the formation and subsequent collapse of vapor bubbles
in a pump.
Gas binding of a centrifugal pump is a condition where the pump casing is filled
with gases or vapors to the point where the impeller is no longer able to contact
enough fluid to function correctly.
Shutoff head is the maximum head that can be developed by a centrifugal pump
operating at a set speed.