Centrifugal pumps

Centrifugal pumps are the most selected pumping devices in the hydraulic world. In this article we will have a theoretical overview of working of centrifugal pumps.

At the core of the design lies the impeller. It has got a series of curving vanes, fitted inside covering plates. The impeller is constantly submersed in water. When the impeller is made to rotate, it makes the fluid surrounding it also rotate. This imparts centrifugal force to the water particles and the water moves radially out. Since rotational mechanical energy is passed to the fluid, at discharge side of the impeller, both pressure and kinetic energy water will rise.

At the suction side water is getting displaced, so a negative pressure will be brought at the eye. Such a low pressure helps in sucking freshwater channel into the system again, and this procedure continues. This is the reason why priming is significant for centrifugal pumps. However, the negative pressure developed by the rotating air at the Eye of impeller will be negligibly little to suck fresh channel of water, If no water is present initially.

Impeller is fitted inside a case. So the water moving out will be gathered inside it, and will move in the same direction of rotation of impeller, to the discharge nozzle. Now you can follow one specialty of housing. It has got expanding area along the flow direction. Correspondent expanding area will help in accommodating, freshly added water channel and will also help in reducing exit flow velocity.

Reduction in flow velocity will influence in increase in static pressure, which is demanded to overcome resistance of pumping system then you can see additional details of veins inside impeller. They’re backward curving vanes with state-of-the- art Eye configuration this vane is pulled from a Centrifugal pump model.

Nonetheless, a dangerous phenomenon could occur, If pressure at suction side impeller goes below vapour pressure of water. Water will start to boil forming vapour bubbles and spoil impeller materials over time this phenomenon is known as cavitation. Further the section head, lower should be the pressure at the suction side, to lift the water. This fact puts a limit to maximum suction head a pump can have. Careful pump selection is needed to avoid the problem of cavitation.

The current impeller type is enclosed, semi-open and open impellers are also in use depending upon the application. However, it’s preferred to use open kind of impeller, if the working fluid is cloggy in nature. But they’re slightly less efficient.

Mechanical design of centrifugal pump is always demanding. A shaft is used to connect between the impeller and motor since water pressure inside the covering is huge, a proper sealing arrangement is imperative in arresting water leakage through the shaft- housing clearance. Mechanical seal or stuffing box grounded mechanism is used for this purpose. Impeller is mounted on bearings, but at the suction side impeller, it isn’t wise to fit a bearing, since it’ll block the flow. So bearings have to be fitted at the other end. This means impeller is mounted like a cantilever. For high flow rate pumps, a bearing casing with cooling oil is necessary for enhancing the life for bearings.

Contact Us

Scroll to Top