Sweep of single-stage centrifugal pumps
Thread Content
Is the shaft runout of a single-stage centrifugal pump equal to the bearing clearance plus the distance from the outer ring of the bearing to the gland?
What operating conditions? It’s that precise; even the axial displacement of single-stage pumps needs to be determined
The engineer said the operating conditions are quite ordinary
It is the axial play of the bearing plus the distance from the outer ring of the bearing to the gland
Bearing clearance is essentially the play; there is only an expansion gap between the bearing outer ring and the cover
The axial play of a single-stage centrifugal pump is the clearance of the thrust bearing inside the bearing housing, plus the gap between the outer ring of the bearing and the gland
Your question is leading us into your trap: a single-stage pump cannot have any axial movement; only play can exist.
Centrifugal pumps with a single-stage cantilever design have three types of clearances. The first one is related to the expansion of the pump shaft, which is addressed through structural design, with one end being equipped with NU series bearings to solve this issue. The clearance for the thrust bearing in the second pairing is **standardized, and you must comply with it. The third gap needs to be filled using end caps and green paper, primarily to adjust the clearance of the paired thrust bearings. Be sure to pay attention to these three clearances during maintenance.
It can be understood in this way: after the pump’s rotor is installed in the bearing housing, the measured gap between the bearing caps represents the thermal expansion gap of the bearings, and it also constitutes part of the axial displacement that occurs as a result of movement during pump operation. When the pump is in operation, the impeller is subjected to an axial force generated by the pressure of the medium, causing the rotor to shift in the direction of the opposite gear. The displacement amount in this shifting process also includes the axial play of the positioning bearing. There is an axial gap between the bearing gland of the pump’s positioning end and the outer ring of the bearing after it has been repaired; during operation, this gap causes movement, which brings the bearing gland and the outer ring of the bearing into contact with each other. When the bearing temperature rises, the bearing and rotor expand in the direction of the impeller.