Centrifugal pumps used in industrial manufacturing should be inspected every day for signs of wear and tear. One of the most visible signs of wear and tear is damage to the pump casing. There may also be problems with the casing that are less noticeable.
Sometimes, the centrifugal pump casing will fill with gases and vapors. This can be so severe that it prevents the impeller from contacting the fluid and the pump is no longer able to function properly. While centrifugal pumps can tolerate some gas within the casing, there needs to be a working ventilation system to remove gases from the pump. Systems that do not vent automatically will need to be vented manually.
The rotating impeller is contained within the stationary pump casing. The impeller needs to rotate freely within the casing. Therefore, a small amount of clearance is allowed. For the pump to operate efficiently, the clearance for the impeller needs to be as small as possible to minimize leakage. Sometimes, wear and erosion occur to the point where the impeller and casing touch. As both components wear, clearances can be greater to the point where leakage becomes worse. The best way to resolve this problem is with the use of wearable rings that can be replaced. The rings are much more affordable to replace than the pump casing or the impeller.
Rotating Shaft Leakage
Almost all centrifugal pumps have a rotating shaft that penetrates the pressure boundary of the casing. The pump needs to be designed to where it controls the amount of liquid that leaks along the shaft where the shaft penetrates the casing. One of the most simple ways to control this is with a stuffing box. This is a cylindrical space that surrounds the shaft and contains rings of packing material. A gland holds the packing rings in place. The shaft rotates at a high speed and this creates a great deal of heat. Therefore, the packing rings will need to be cooled or protected in some other way or they will need to be replaced regularly.
Packing rings are sometimes not an optimal solution to sealing a shaft and it may be necessary to instead use mechanical seals. These consist of a rotating element connected to the pump shaft and a stationary element that is connected to the pump casing. These have polished surfaces that create seals that prevent leakage.
For more information, contact a business like PFC Equipment, Inc.