Centrifugal Pump Impeller - The Heart Of The Centrifugal Pump

One of the most important parts of a centrifugal pump is an impeller. The fact is that the centrifugal pump impeller combined with the volute helps to create a partial vacuum. It also discharges the pressure required to move water through the pump's casing.

The centrifugal pump impeller combined with the volute forms the pump's heart. It basically decides the pump's flow, its pressure and its solid handling capability.

An impeller is actually a rotating disk, equipped with a set of vanes. It is attached to the engine or the motor shaft that helps in producing the centrifugal force within the casing of the pump.

One of the most popular and frequently used forms of centrifugal pump impellers is the open impeller. These open impellers can pump liquids containing various suspended solid materials. The materials usually include things like paper stock and slurries, among others.

These impellers are not known to plug as easily as the closed impellers. These impellers usually have a simple external adjustment that helps in the maintenance of the correct impeller clearance as the internal parts start to wear.

In order to achieve a higher efficiency and a good commendable performance, the front, or the suction side, of the vanes should be set with a close clearance against the suction wear plate.

However, when the impeller and the suction plate start to wear out with time; the performance of the pump will also start to deteriorate. Still, with regular clearance checks and periodical adjustments, the pump's good performance can be maintained.

The clearance behind the impeller can be increased if the impeller is adjusted towards the suction wear plate.

Usually, the impellers have small vanes located on the non-pumping side. These vanes are called "back pump-out vanes". These smaller vanes are able to act like another centrifugal pump. Also, they can help to maintain a low pressure at the stuffing box.

In the absence of these vanes, the stuffing box pressure may come close to the overall discharge pressure of the pump. This can easily result in the contamination of the packing which may reduce the overall life of the pump's packing.

In case the pump's performance is reduced, the impeller clearance has to be adjusted. In case the packing life is reduced, both the pump's suction as well as the back-side clearances has to be checked.

Also, in case the back-side clearance exceeds the manufacturer's recommendation then the solution is to install a thinner gasket between the pump volute and the stuffing box cover. This can help you achieve the correct and the much needed clearance.

The fact of the matter is that the pump's performance is largely based on the centrifugal pump impeller; therefore it is necessary to keep it in good shape.