The bearing at the non-driven end of the self-balancing multi-stage pump is too hot, at 88 degrees Celsius. What could be the possible reasons for this?
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Self-priming multi-stage pump, 8 stages, inlet pressure 1.0 MPA, outlet pressure 4.0 MPA, for clean water. Pump bearings: N212 on the drive side and 7212 on the non-drive side. The temperature of the bearing on the non-drive side rose to 88 degrees Celsius after 4 hours of operation; vibration of the pump was minimal, and the vibration level at the end cover was 2.6 mm/s. Several sets of bearings have been replaced, but the problem persists.
Is the clearance of the intermediate throttle sleeve appropriate? High bearing temperatures usually indicate a high load. Which of the back-to-back bearings on the non-driving side shows more wear marks?
Throttling sleeve: originally designed to be made of silicon carbide, but it suffered frequent damage; now it is made of 45# steel, with a Ni625 coating welded on the outer layer of the inner sleeve, and a gap of 0.1 mm
Is it the front-back and hot-cold zoning of the shaft that causes an increase in deflection under operating conditions? ! Is the alignment between the motor and the shaft insufficient? !
Is the interference amount on the shaft too large? Have you measured the dimensions of the shaft journal?
What is used to balance the axial force in a pump?
The clearance of the bearing cover at the non-driving end isn’t properly adjusted; in other words, the axial forces on both ends are not balanced. The bearing at the non-driving end will surely heat up when it is subjected to high axial forces for an extended period of time. Does the grease lubrication still continue at 88°? It’s fine if there isn’t one
For multi-stage pumps, the key issue is the balance of axial forces. It seems to you that the axial forces are not properly balanced; check whether the self-cleaning pipe is blocked, whether there have been any changes in the operating conditions of the medium, and whether there is wear on the balance disc assembly, etc. Another possibility is that there is an interference fit between the bearing cover and the bearing.
The bearing types at both ends are different – roller bearings and ball bearings – so it’s impossible for their temperatures to be the same. Additionally, factors such as oil level, oil quality, and oil lubrication also contribute to higher temperatures; it’s necessary to check each of these aspects one by one