Multistage Centrifugal Pump

WHAT IS MULTISTAGE CENTRIFUGAL PUMP?

When two or more impellers are mounted on the same shaft or on different shaft in a centrifugal pump is called multistage centrifugal pumps.The function of a multistage centrifugal pump is two types.

   1) To produce a high head

   2)To discharge a large quantity of liquid

When impeller is connected in series with the same shaft of a centrifugal pump, it produced high head and to discharge in large quantity of liquid, impeller should be connected in parallel with the same shaft of the pump. To know the multistage centrifugal pump, read work done by a centrifugal pump on water.

1)    Multistage centrifugal pumps for high heads :

To develop this type of centrifugal pumps, a number of impellers are mounted in series or on the same shaft, see the following diagram.

In the above picture water is coming from a suction pipe and enter to the first impeller. After that water is discharged at outlet with increased pressure. The water with increased pressure from the outlet of the first impeller is taken to the inlet of the second impeller with the help of a connecting pipe. Now the pressure of the water is more then the pressure of the water at the outlet of the first impeller. It is easy to understand that more number of impellers are connected in series with the shaft, pressure of the water at the outlet will be increased further.

Now, Let, n = No. of identical impellers mounted on the same shaft,

H_m = Head develop by each impeller

So, total head developed = n × H_m

The discharge passing through each impeller is same.

2)    Multistage centrifugal pumps for high discharge :

To get high discharge multistage centrifugal pump, the pump should be connected in parallel to the shaft. In the above picture we can see two pumps are connected in parallel position with a common pipe. Now each of the pump lift the water from a common pump and discharge water through the common pipe which is connected to both pumps. Each off the pump is working against the same head.

Let, n = No. of identical pumps arranged in parallel,

Q = Discharge from one pump.

So, Total discharge, = n × Q