Maintenance Knowledge Of Centrifugal Pump

We should not use the centrifugal pump until it is broken.In order to make the centrifugalpump a long life,what should we maintenance duing the pump usage?

centrifugal pump (2)

A.Pump shaft maintenance.

1. Clean and check the centrifugal pump shaft. The centrifugal pump shaft shall be free of cracks, severe wear and other defects. If there is wear, crack, erosion, etc., it shall be recorded in detail and the cause shall be analyzed.

2. The straightness of pump shaft of centrifugal pump shall not be greater than 0.05mm in the whole length. There shall be no pitting, groove and other defects on the surface of journal. The maximum allowable value of surface roughness is 0.8 μ m, and the error of roundness and cylindricity of journal shall be less than 0.02mm.

3. The parallelism error between the center line of the key groove of the centrifugal pump and the center line of the shaft shall be less than 0.03mm/100.

4. The allowable bending of shaft diameter is not more than 0.013mm, for the middle part of low speed pump shaft is not more than 0.07mm, and for the middle part of high speed pump shaft is not more than 0.04mm.

5. The surface of the shaft is smooth without cracks, wear, etc.

6. The surface of shaft sleeve shall be RA = 1.6um.

7. H7 / H6 is used for shaft and sleeve.

copper slurry pump

B.Measurement of shaft curvature of centrifugal 

After the centrifugal pump shaft is bent, it will cause the unbalance of the rotor and the wear of the dynamic and static parts, so the bending degree of the pump shaft should be measured during the overhaul.

① Put both ends of the shaft of centrifugal pump on the V-shaped iron, and the V-shaped iron shall be placed stably and firmly;

② Then support the dial indicator so that the measuring rod points to the shaft head. Then, slowly rotate the centrifugal pump shaft. When the shaft is bent, the dial indicator has a maximum reading and a minimum reading every revolution. The difference between the two readings indicates the bending degree of the shaft. This measurement process is actually to measure the radial runout of the shaft, that is, the wobble.

③ Half of the wobble is the bending value of the shaft. Generally, the radial runout of pump shaft shall not exceed 0.05mm in the middle and 0.02mm at both ends

Maintenance of centrifugal pump head, pump casing and guide impeller

C.Maintenance of bearings

sliding bearing

(1) The interference between the bearing and the bearing gland is 0.02-0.04mm, and the contact area between the lower bearing liner and the bearing seat is more than 60%.

(2) When replacing the bearing, the contact angle between the journal and the lower bearing shall be 60-900, and the contact area shall be uniform, and each square centimeter of the contact point shall not be less than 2-3 points.

(3) The bearing alloy layer and the bearing lining shall be firmly combined, and the surface of the alloy layer shall be free of defects such as porosity, slag inclusion, peeling, etc.

(4) The bearing top clearance shall be in accordance with the following table.

(5) The data of the bearing side clearance on the horizontal split is half of the top clearance.

D.Clearance of rolling bearing

The so-called clearance of rolling bearing refers of centrifugal pump  to the maximum displacement of inner ring (or outer ring) in radial or axial direction after the outer ring (or inner ring) is fixed. Radial displacement is called radial clearance, and axial displacement is called axial clearance.

The rolling bearing is allowed to have proper clearance during operation. If the clearance is too large, the number of rolling elements bearing load at the same time will be reduced, which is easy to cause elastic deformation between the rolling element and the ferrule and reduce the bearing life of centrifugal pump. At the same time, it also reduces the rotation accuracy of the bearing and produces radial runout, which causes vibration and noise; if the clearance is too small, the resistance will increase during operation, which will cause the bearing to heat up and accelerate the wear of the bearing.

Preloading of rolling bearing

When assembling the bearing, it is necessary to pre tighten the bearing, that is, to give a certain axial preload to the inner and outer rings of the bearing, so that the relative displacement of the inner and outer rings occurs, and adjust the clearance. After preloading, the bearing of centrifugal pump can control the correct position of the inner and outer rings, thus improving the rotation accuracy of the shaft. Increase bearing life of centrifugal pump.

When disassembling the rolling bearing, what should be paid attention to when applying force to it?

(1) Special tools (press, puller, etc.) shall be used, and hammers shall not be used to avoid uneven force, local injury or direct damage to bearings;

(2) The force shall be applied to the tight fitting ring, not to the loose fitting ring, so as to avoid the bearing contact surface from generating pits and causing the bearing to be damaged in advance;

(3) The force distribution should be symmetrical and even, and perpendicular to the end face of the tight fitting ring, so as to avoid local stress of the bearing

centrifugal pumps