Centrifugal pump seal has two parts. 1, seal ring. As the centrifugal pump impeller outlet liquid is high pressure, the inlet is low pressure, high pressure liquid through the gap between the impeller and the pump leakage back to the suction place, so the need to install the seal ring. Its role is to reduce the leakage between the impeller and the pump leakage; the other hand, to protect the impeller to avoid friction with the pump body. 2, shaft seal (referred to as shaft seal). There is a gap between the shaft of the pump and the pump housing to prevent the outflow of liquid from the pump or the leakage of air into the pump (when the inlet is under vacuum) and a seal is required.