Unexplained high shaft vibration in turbine; seeking discussion
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This post was last edited by Lihua Yiduowei Xiaoxiu on 2018-1-30 at 17:06. Our plant currently has a back-pressure steam turbine, with a designed inlet steam pressure of 4.2 Mpa and an outlet pressure of 0.5 Mpa. After the successful load test in December 2017, it operated without any abnormalities until mid-January 2018. Later, the plant was shut down once due to steam issues; after it was restarted, the vibration of the turbine exceeded its critical speed and gradually increased as the speed rose. Once the operating speed of 7000 was reached, the shaft vibration fluctuated in inverse proportion to the inlet steam pressure, with the highest value of vibration reaching 53 μm. The historical trend chart is below. I wonder if anyone else has encountered the same situation?
Is it always this high? If it remains this high while the machine is running, it’s possible that a blade has fallen off. In the past, a blade falling off was the cause of this issue; when using the machine, it’s also necessary to check whether any water has remained and hasn’t been completely drained.
It should be made clear what this turbine is used for – is it to drive a generator to produce electricity, or to power a gas compressor?
If it is a drive gas compressor, then factors such as the pressure, flow rate, temperature of the medium gas, and the operating conditions of the oil-driven motor all have an impact.
If it is a generator, a reducer is needed; those equipped with fans or compressors also require reduction of speed. The original poster can provide more details
Is the steam transmission proper? The insulation effect is poor; it’s not saturated steam, and the turbine blades are unbalanced
Check whether there is any damage to the impeller blades or if any foreign objects are attached to them
During the speed-up process, once the critical speed is exceeded, the value starts to increase as the speed rises; it goes up by a small amount for every 100 revolutions, rising from less than 30μm to the current level of 50μm. After reaching the rated speed, the steam is not that stable, at around 3.8 Mpa; then when the pressure of the steam increases slightly, the vibrations decrease a bit. However, once the steam stabilized, it rose slowly.
Could you please specify which diagrams are needed? I’m going to take a photo of it
If it were up to you to decide, what specific data would be needed?»