The centrifugal pump is smoking
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During the single-stage centrifugal operation of our pump, smoke started to come from the bearing housing near the motor, so we immediately stopped the pump. At first, we thought it was caused by oil emulsification inside the bearing housing, but after disassembling the pump, we found that the oil seal was in good condition and no water was present. After the second maintenance session, more than half of the oil was added back to the pump, and yet the same problem occurred again after just half an hour of operation – smoke appeared from the bearings once more. When the pump was disassembled, it was found that the impeller and the backing wheel were stuck together so tightly that they couldn’t be separated even with a hydraulic tool. Alignment checks during maintenance showed no issues, and all parameters were within normal ranges. Even if there was some vibration, as long as there was oil present, the pump shouldn’t burn out in just half an hour. I would like to ask other experts: has anyone encountered such a situation? In my opinion, as long as there is enough oil and no emulsification occurs, the pump generally won’t overheat or start smoking; it also won’t vibrate excessively. With sufficient oil, the bearings shouldn’t overheat either. It’s a bit confusing – if oil has been added, could there be other issues?
Is the impeller not properly dynamically balanced? Is the pump shaft bent? Are there any foreign objects in the impeller and the rear cover?
This post was last edited by zg402788469 on 2017-5-14 09:52. Hehe, could it be that the grease on your bearings wasn’t cleaned properly, which caused smoking when the temperature rose?
High axial thrust; principle of turning impellers – turning impellers or enlarging the balance holes in them
Bearings serve different functions, and such problems occur when a thrust bearing is damaged. For example, a tapered roller bearing provides both radial support and axial thrust force. As the wear increases slightly, the shaft alignment changes more, until friction between the rotor and stator occurs. Another factor to consider is the clearance of the coupling; if the installation clearance is too small, the length of the structure increases as the rotor heats up, and this can damage the thrust bearings. . . . . It would be best to send images of both sides of the rotor, to facilitate targeted discussion.
Several factors can be considered: 1) Bearing issues – whether the clearance between the inner and outer rings is appropriate; when installing bearings back-to-back or face-to-face, it is necessary to ensure that the bearing preload is set correctly. If possible, use SKF ****BECBP or BECBM universal mounting bearings. Choosing a bearing with too high precision and thus too small a clearance can also cause problems. 2. Is there any issue with the machining precision of the bearing housing? Can it ensure proper concentricity? Is the position of the oil sight gauge appropriate? If it is too low, the actual oil level will not be sufficient to lubricate the bearings, which can lead to oil leakage! 3. The axial force balance is poor; check whether the diameter of the impeller’s balance holes is appropriate, whether they are blocked, and whether there are any issues that prevent water from flowing smoothly into these holes! Or whether the gap between the impeller back blade and the rear cover plate is appropriate. The clearance for the 3 bearing caps is generally set at 0.10–0.30 mm!
After the inspection, there were no problems with the turning gear; the oil level was also fine, and the turning gear operated smoothly. After removing the pump, it turned out that the impeller was stuck to the backup wheel. The thrust bearing showed slight signs of overheating, turning purple in color. As long as there is oil present, the turning gear functions normally, and the oil film provides a certain degree of stiffness. Even if there is some vibration, the temperature should rise gradually rather than causing leakage right from the start. In the end, we were unable to identify any other issues, so we decided to try increasing the clearance slightly
There’s also that bearing; check whether the tapered bearing is excessively worn, as a change in the thrust position can also be a factor.
Additionally, regarding that bearing, check whether the tapered bearing is excessively worn; a change in the thrust position can also be a factor.