The centrifugal pump transfers fluid at a certain capacity from one point to another in a process. The pump builds up fluid pressure to overcome losses in the process. Capacity and pressure are created by the rotating impeller inside the pump casing.
General principle:
· Fluid enters the pump casing and impeller center and is forced into a circular movement by the impeller vanes and the centrifugal force. The fluid thus leaves the casing with increased pressure and velocity.
· Typically suitable for low viscous, non-particulate and non-aerated fluids such as beer, CIP, cream, juice, milk, soft drinks, water etc.
Single-stage principle:
The fluid inlet, the built-up of velocity and pressure and the fluid outlet all happens in one stage (one casing and one impeller).
Multi-stage principle:
· Fluid enters the pump casing and impeller center, and fluid pressure and velocity are built up in the first stage (casing and impeller) similar to the single-stage pump.
· Fluid with increased pressure and velocity is directed to the second stage (casing and impeller), where the fluid pressure and velocity is further increased.
· The result is a pressure increase (boost) in each stage, where the total pressure increase depends on the number of stages in the pump.
· Typically available with 2-4 stages.
Priming of a centrifugal pump:
· The pump casing should always be filled with fluid before starting the pump to ensure correct operation.
· The pump can operate with a positive inlet pressure (flooded inlet) or with a negative inlet pressure (suction lift).
· For suction lift, fluid can remain in the pump casing by using a non-return valve in the suction line.
