The vibration of the rear shaft of the compressor turbine is increasing abnormally and irregularly; the cause cannot be identified, seeking assistance
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Recently, the radial shaft vibration values of the steam turbines (back-pressure type) produced by our factory have increased abnormally, as shown in the graph. The highest value reached 67, while the interlock threshold is 75. There are fluctuations; sometimes the difference is 12 hours, and at other times it’s 8 hours, etc. We have checked the steam pressure, temperature, lubricating oil temperature, as well as the base fixation and nitrogen sealing systems, and no issues were found (the fluctuation in the lubricating oil temperature is kept within ±1 degree, and the steam parameters are basically the same as those under normal operating conditions). Currently, the shaft seal extraction cooler is not in use and vented directly to the atmosphere; it was shut down only when the vibration anomaly first occurred, as it was suspected that there was a problem with the extractor, preventing it from properly removing the moisture from the turbine casing. Solve: What is the cause of the abnormal vibration?
It’s difficult to pinpoint exactly which part is problematic with this kind of issue, but one thing is clear: the various configurations on the device should not be suspected of being faulty and disabled arbitrarily. Also, one should not consider only the problems with the turbine itself; it is necessary to take into account the load devices connected to it as well, and to examine the trend records to see if they are related to changes in the load on those devices. Furthermore, before approaching the critical value, it is advisable to disassemble the equipment and conduct mechanical inspections, such as checking the corrosion condition of the flow channels in each guide vane, the corrosion status of the inter-stage steam seals, the dynamic balance of the rotor, the clearance of the bearing shells, the alignment of the couplings, and the levelness of the equipment. Conduct a thorough inspection of all factors that may cause vibration in the equipment.
Conduct a status monitoring; if it’s at twice the frequency, the problem is most likely in the rotor itself
When it starts vibrating, the operating noise of the machine on site increases significantly; this abnormal noise lasts for a little over twenty seconds before disappearing. After each such increase, the machine remains at a low level of noise for some time
The one on the 6th floor is reliable; our situation is the same
1. Is it exceeding the design load? We experienced a similar phenomenon before, which was caused by fluctuations in load leading to fluctuations in the oil film; if conditions permit, it is recommended to reduce the load and observe the situation