Why is a seal needed in a centrifugal pump?

The purpose of installing a seal on a centrifugal pump is to prevent the substances inside the pump from leaking out.

To prevent fluid leakage, the seals of centrifugal pumps consist of the following components: First, the shaft seal (at the coupling end) is used to prevent leakage of the medium or intrusion of air through the gap between the pump shaft and the pump casing. Common seal types for this purpose are packing seals or mechanical seals. Second, there is the seal ring seal (in multi-stage pumps, this is also referred to as the inter-stage ring seal). The seal ring, also known as an end ring, is installed at the inlet of the impeller and on the corresponding part of the pump casing. Its function is to prevent high-pressure fluid from the discharge chamber from flowing back into the impeller’s inlet, thereby improving the pump’s efficiency. The sealing mechanism relies on the fluid resistance created by the gap between the seal ring and the impeller. Various types of seal rings exist, including flat rings, angled rings, serrated rings, and labyrinth-type rings.