Centrifugal pump Grundfos

Centrifugal pumps: get to know everything about this pump type

Centrifugal pump-Hilge-Egger-Grundfos

The centrifugal pump

Centrifugal pumps are used in almost every production process, for a wide variety of applications. Inventflow has a wide range of centrifugal pumps, which you can view here.

Centrifugal pump working principle

The design and operation of the pump is explained here. The pump housing has two openings with the connections for the suction and the discharge pipe. 

The axial opening for the suction connection is at the level of the opening of the impeller. The opening for the pressure connection is on the outer circumference of the pump housing.

The flow

The pump and suction lines must be completely filled with the liquid that is going to be pumped. When the pump is started, the centrifugal force will cause the liquid to flow in the direction of the impeller.

As a result, the liquid flows on the outer circumference of the impeller into the pump housing and then, via the discharge opening, to the discharge pipe.

Negative pressure

Because the liquid flows out of the center of the impeller, underpressure is created. As a result, the liquid from the suction pipe flows into the impeller, which in turn flows through the pump housing to the discharge pipe by the centrifugal force.

In this way a continuous flow is created from the suction line, through the pump housing, to the discharge line.

the Centrifugal Pump: the pros and cons

Pros:

  • Centrifugal pumps are often small in size compared to other pump types with the same volume flow and head
  • Relatively low maintenance costs due to few moving parts
  • Suitable for direct drive
  • Purchase price is low in comparison with other pump types
  • Even volume flow
  • Suitable for heavily contaminated liquids when selected correctly

Cons:

  • Centrifugal pumps usually cannot pump air
  • Volume flow is strongly dependent on the required head
  • Not suitable for dry running
  • Viscosity max. 400 mPas
  • Cavitation in centrifugal pumps

THE CENTRIFUGAL PUMP AND CAVITATION

Imploding vapor bubbles in the water cause noise and vibrations, which are followed by mechanical shocks. Cavitation causes damage to the impeller and the pump housing, and thus has a very negative effect on the life of the pump.

Preventing cavitation

Cavitation can be prevented by keeping the pre-pressure (NPSHa) of the pump higher than the vapor pressure (NPSHr) of the pump. The NPSHa value must be at least 1 mWk higher than the NPSHr value.

It is therefore also very important that the correct pump is selected for the application in question. Inventflow can assure you of correct pump selection by experienced pump specialists.

Centrifugal pump cavitation impeller

Shaft seals for a centrifugal pump

Shaft seals are used to minimize leakage between the pump cover and the rotating shaft. A shaft seal is placed where the pump shaft exits the pump housing.

DEFECTIVE PUMP DUE TO SHAFT SEAL

Shaft seal failure is the most common cause of centrifugal pump shutdown. In addition, failures, leaks and reduced performance of a pump are very often caused by a problem with the shaft seal.

Inventflow supplies and overhauls a wide range of shaft seals for almost every industry and application, read more here.

Different impeller types

One of the main parts of centrifugal pumps is the impeller. Many different types of impellers are available for different applications. This includes: Open impellers, closed impellers, semi-open impellers, retracted impellers and side channel impellers. Each fan type has its own features and benefits, as explained below.

Open impeller

The open impeller is very suitable for pumping liquids with solid particles. The impeller consists of blades without side walls as with a half-open or closed impeller. The maximum dimension of the solid parts is determined by the blade height.

Closed impeller

The closed impeller consists of two side walls with blades in between. These blades are bent backwards with respect to the direction of rotation. This limits internal leakage and allows maximum efficiency to be achieved. This design also allows the impeller to pump a high capacity and pressure.

Half-open impeller

The half open impeller is a combination of an open and a closed impeller. The impeller has no wall on the inlet side, so it can pump more solids than a closed impeller. Incidentally, the efficiency is lower compared to a closed impeller.

Channel impeller

The channel impeller is used for contaminated liquids with solid parts. Channel impellers are available with one, two or three channels. Due to the design, the efficiency is relatively low, but the field of application is very wide due to the clogging-free operation.

Retracted (Vortex) impellers

With retracted impellers, a large space is created between the pump housing and the impeller. This allows large solid parts to be pumped. Incidentally, this makes the maximum capacity and head relatively low in comparison with other impellers. The efficiency of withdrawn impellers is therefore also low.

View our range of centrifugal pumps

click here to view our full range of centrifugal pumps.

Everything about the centrifugal pump
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