Multistage Centrifugal Pump




A simple centrifugal pump use a single impeller mounted on a shaft to produce a specific head and a specific discharge rate but what if you need n times greater head or discharge rate. This problem can be solved by using the multistage centrifugal pump

There are two possible reason why you use multistage centrifugal pump

1. Need high head at constant discharge rate
2. Need more discharge rate at constant head

Mounting more than one impeller on a same shaft and closing them in same casing will produce higher head than single impeller pump but the discharge rate will be same as single impeller

If you install two pump parallel to each other at same sump then the discharge rate will be increase but head will be same as that of single pump


Pump is series

In series arrangement of pumps, more that one impellers are mounted on the single shaft of a centrifugal pump and closed under a same casing. This arrangement can increase the head of the pump by keeping the discharge rate constant.This type is used to deliver small quantity of liquid at high head

In this type of arrangement impeller one take is input from the sump and discharge is at a specific head and discharge rate. This out put if impeller one is the input for the impeller number two. Out put of impeller number two will be same discharge and twice the head.

H total = n H
n = number of impeller
H = head made by single impeller





Advantages


  • Less frictional losses
  • Reduce stresses
  • Less slip leakage
  • Thrust can be eliminated
  • High suction lift at relatively low impeller speed


Pump in parallel


For a single centrifugal pump it is impossible to deliver a huge quantity of liquid at small head but it is possible with parallel arrangement of pump. More that one pumps are install at a single source and both of them work separately to produce a specific discharge rate then their out put is merged in a single delivery pie to get a  greater discharge rate than single pump.

Q total = n Q
n = number of pump installed
Q = Discharge of single pump

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