Centrifugal pumps contain rotating impellers within stationary pump casings- To allow the impeller to rotate freely within the pump casing, a small clearance is designed to be maintained between the impeller and the pump casing. To maximize the efficiency of a centrifugal pump, it is necessary to minimize the amount of liquid leaking through this clearance from the high pressure or discharge side of the pump back to the low pressure or suction side.
Despite the various application types of centrifugal pumps in technical plants the operating ranges of the different designs depending upon size of the delivered flow, the delivery head and the number of revolutions another characteristic impeller form results in the case of aiming at an optimal efficiency. With the help of the rapidity and/or the specific number of revolutions the impellers can be split up according to their targeted application .
If very large volume flow rates are needed, or if the velocity of flow is limited in the entrance for reasons of the suction behaviour, radial flow pumps are frequently implemented in a multi-flow way. Thereby two impellers with same dimensions deliver in a common housing. With same delivery head the two flow rates are added together.
Since the maximum delivery head of an impeller is fixed by the pressure factor in dependence of the design and upward the number of revolutions limited by firmness reasons, for the achievement of large delivery heads several pump stages are connected in series. The delivery heads of the single stages are added with same flow rate.
Some wear or erosion will occur at the point where the impeller and the Centrifugal pump casing nearly come into contact. This wear is due to the erosion caused by liquid leaking through this tight clearance and other causes. As wear occurs, the clearances become larger and the rate of leakage increases. Eventually, the leakage could become unacceptably large and maintenance would be required on the pump.
Some wear or erosion will occur at the point where the impeller and the Centrifugal pump casing nearly come into contact. This wear is due to the erosion caused by liquid leaking through this tight clearance and other causes. As wear occurs, the clearances become larger and the rate of leakage increases. Eventually, the leakage could become unacceptably large and maintenance would be required on the pump.
To minimize the cost of pump maintenance, many centrifugal pumps are designed with wearing rings. Wearing rings are replaceable rings that are attached to the impeller and the pump casing to allow a small running clearance between theCentrifugal pumps impeller and the pump casing without causing wear of the actual impeller or centrifugal pump casingmaterial. These wearing rings are designed to be replaced periodically during the life of a pump and prevent the more costly replacement of the impeller or the casing.
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