Self-priming centrifugal pumps
A self-priming centrifugal pump can remove air from the suction line and draw liquid into the pump without the suction line having to be filled beforehand. This makes these pumps particularly suitable for installations where the pump is positioned above the liquid level or where the suction line drains when the pump is stopped.
IB-Pompen offers a wide range of self-priming centrifugal pumps for applications ranging from industrial wastewater transfer to demanding sewage applications in municipal and industrial environments. The range includes conventional wet self-priming pumps and vacuum-assisted models.
How a centrifugal pump works
A centrifugal pump consists of a pump casing containing one or more impellers. For the pump to operate, the casing must be filled with liquid at start-up. As the impeller rotates, the liquid is flung towards the outer circumference, creating a low pressure at the centre of the impeller. This causes liquid to be drawn in at this point. The liquid velocity is highest at the outer circumference of the impeller. In the pump casing, this velocity is then converted into pressure.
The wider the impeller, the more liquid can be pumped and the higher the capacity. The larger the impeller diameter, the greater the head (pressure) that can be generated. The impeller’s rotational speed has a direct influence on both the capacity and the head, and also significantly affects the power consumed by the motor. The duty point ultimately reached also depends on the characteristics of the system in which the pump is installed.
Different types of centrifugal pump
Centrifugal pumps are available in end suction and self-priming designs. The casing of a centrifugal pump must always be filled with liquid for the pump to operate. An end suction centrifugal pump cannot handle any air, or only very little. Both the casing and the entire suction pipe must therefore always be completely filled with liquid.
A self-priming centrifugal pump is usually designed such that the impeller always remains below the liquid level. If air is drawn in from the suction pipe, it mixes with the liquid present in the pump casing. The air then gradually leaves the casing via the discharge side, whilst the impeller continues to create a low pressure.
To prevent excess air from entering the pump, it is important that both the suction and discharge pipes are correctly designed.
