Reasons for turbine vibration fluctuations
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Experts, our company has a Hangzhou Steam Company back-pressure steam turbine model NG25/20. The vibration of its support bearings showed slight fluctuations during the time period shown in the figure; among the 4 probes, one had a minimum value of 22.5 μm, which increased to 30.7 μm (with a high reading of 41 μm). 61’s chain). It persisted for 10 minutes before everything returned to normal. During that time, the load on the turbine-driven centrifuge did not change, nor did there be any fluctuations in the vibration or temperature of the centrifuge bearings. The amount of air supplied to the turbine also remained unchanged, and the temperature of the turbine bearings was normal with no fluctuations. Oil temperature and pressure were also within normal ranges. What other possible causes could explain this situation?
If it isn’t vibrating frequently, don’t move it; observe carefully – it might be resonating with some vibration source in the vicinity； If this phenomenon occurs frequently, it needs to be addressed. During operation, the vibrating sections of the pipeline can be reinforced first to see if that helps; if not, the system must be shut down for inspection. Vibration is a quite troublesome issue!
Consider the weight, scaling (dynamic balance), steam quality, quick-close valve filter, insufficient bearing support, and whether the oil temperature and inlet temperature are too high (Over 49°) The simplest approach is to consult a professional for a spectrum analysis, which can help narrow down the areas that need to be checked
Is the support bearing the front bearing or the rear bearing? Has the steam seal pressure been adjusted? What causes the expansion or cooling of the steam seal? Is the vibration of the Hangzhou Steam Condensing Turbine Drive Unit 22.5 μm at the minimum value among the 4 probes? It’s actually already quite large; normally, the value should be below 10 for stable operation. If there is a phase shift, it’s necessary to consider the phase shift value, thermal expansion difference, and displacement together when making a judgment. Secondly, oil film interference may occur, causing instantaneous vibration fluctuations
Checking the trend chart, there have been a few fluctuations in the past one or two months, all of relatively small magnitude
Checking the trend chart, there have been a few fluctuations in the past one or two months, all of relatively small magnitude
Green and red are the front bearings, while white and yellow are the rear bearings. The steam seal pressure has not been adjusted, and there has always been air leakage from the exhaust pipe at the rear steam seal; this problem has existed for a long time. Our company’s unit is a back-pressure steam turbine, as mentioned earlier. What are the causes of oil film interference? Thank you!
The oil temperature is set at 45°; no changes observed. Thank you
It is possible to analyze whether there is a pattern in these fluctuations, such as the time periods in which they occur.
It’s the vibration fluctuations of the rear bearing. So does the compressor’s front bearing have them as well? A significant leak in the steam seal behind the backpressure unit can also cause the sealing sleeve to expand or contract, resulting in transient frictional vibrations. If the rotor shaft deviates from the working center of the bearing shells, it can lead to instability in the oil film, which in turn causes transient vibrations.