The main thrust bearing of the centrifugal booster turbine is worn out, but the control system shows only displacement alarms – temperatures and other parameters are normal. What’s the reason for this?

The main thrust bearing of the centrifugal booster turbine is worn, but the control system only shows a displacement alarm while parameters such as temperature remain normal. Possible reasons include: 1. Improper setting of the bearing clearance: If the gap between the bearing and the shaft is too large or too small, it may cause the shaft to experience significant relative displacement during operation, even if the bearing temperature stays within normal ranges. 2. Lubricant issues: Poor quality of lubricant, insufficient oil film thickness, or abnormal operation of the lubrication system can lead to increased friction, which in turn triggers a displacement alarm. But if it is dealt with in time before the lubrication system returns to normal operation, it may not cause abnormal temperatures. 3. Early stage of bearing wear: In the initial phase of wear, the bearing may only experience slight wear; no sufficient heat is generated to trigger a temperature alarm, but it is enough to cause changes in shaft alignment. 4. Sensitivity of the displacement detection system: Displacement sensors have a high detection sensitivity, enabling them to issue an alarm even when there are slight changes in shaft displacement caused by bearing wear; in contrast, temperature sensors may require a larger range of deviation before they can detect any issues. 5. Foreign object intrusion: It may be caused by a foreign object entering the bearing surface area, resulting in localized wear rather than widespread wear of the bearings; in such cases, the overall temperature of the bearings may not show any abnormalities immediately. 6. Heat resistance of bearing bush materials: Some bearing bush materials may not cause an immediate increase in temperature even after slight wear; instead, it is first reflected in changes in displacement. 7. Instrument failure or inaccurate calibration: It is also possible that there is a problem with the temperature sensor itself or that it has not been calibrated accurately; in other words, the actual temperature of the bearing shells has changed, but due to issues with the detection equipment, the control system fails to display this correctly. In response to this situation, it is recommended to conduct a thorough inspection of the lubrication system to ensure that the quality of the lubricant and its supply are satisfactory, to carry out more detailed inspections and analyses of the worn bearing shells, and to verify the accuracy of the sensors, in order to determine whether any adjustments or replacements of relevant components are necessary. .

If it is wear of the thrust bearing, the levelness of the rotor should be checked as a possible cause and examined carefully. As for the temperature changes, they are likely due to the effect of the lubricant, which carries away the heat generated. Also, check the trend lines; there should be slight changes when zoomed in. For reference.

It is sufficient to conduct regular tests on the lubricating oil; under normal circumstances, these tests are carried out on a monthly basis. The likelihood of problems is low. I suggest checking the axial force, which includes issues related to the equipment itself as well as changes in process parameters.

Displacement alarm: excessive axial force. Check the operating parameters to see if there have been significant changes compared to normal operation in the past

This unit may not have a high rotational speed, so the temperature will not rise