The problem of turbine vibration!
Thread Content
I would like to ask: the vibration levels at one point of the turbine’s front bearing and at two points of its rear bearing are gradually increasing. Under normal conditions, these values are around 10 um, but they gradually rise above 20 um before eventually dropping again. There is no fixed pattern to this phenomenon, and it occurs quite frequently. The oil pressure and temperature are normal, and there is no change in the system’s parameters. The intake parameters are also relatively stable. What causes this?
To be honest, the vibration level of yours is quite good; our factory can’t even achieve such levels. The irregular variations in vibration may be due to the warming-up process – that is, after the machine starts operating, the vibration level changes slightly depending on the operating time. As the machine runs continuously for longer periods, its performance generally becomes more stable and better. If the vibration frequency is high, it’s worth checking whether the speed also changes, because an unstable governor can lead to variations in the amount of steam supplied to the control valves, which in turn affects the speed.
Reply to 2# zzlkool: The rotation speed is also normal, the air intake volume remains stable, and there are no fluctuations in the speed control valve. This phenomenon seems unrelated to warming up the equipment, as the vibration occurs during normal operation. It didn’t happen before, but it started appearing gradually; the vibration level rises for a while before dropping again, with no fixed frequency, yet it occurs quite frequently. We still don’t know the reason – could it be related to the equipment?
Please go back and check: 1. What changes have occurred in the intake air temperature? 2. Has the heat exchange efficiency of heat exchangers at all levels deteriorated?
Please check the insulation of the turbine; I personally think it’s likely caused by external temperatures. When the insulation around the turbine is inadequate, it can lead to localized deformation of the casing. Additionally, it would be advisable to recheck the bearing clearance and the tightness of the bearing shells. It is recommended that the person in question compare the spectra during normal operation with those when vibration increases, to determine which frequency range is showing increased vibration levels, which will help in analyzing the specific cause.
Check the pressure and temperature of the steam, as well as whether there are any fluctuations in the air intake volume; all of these can cause the situation you mentioned. However, this isn’t a problem at all – it’s normal
In addition to the bearing clearance and the preload on the bearing shells, if possible, take a look at the spectrum diagram, as well as check whether there is insufficient condensate drainage and excessive acceleration during operation. It is suspected that rotor thermal bending caused mechanical and static rubbing in the turbine. As for the reasons behind thermal bending, there are several: substandard warm pipes in the early stage ； Insufficient degassing ； Failure to turn the shaft in a timely manner or not turning it at all ； Too rapid acceleration ； Steam carries liquid.
Since the problem occurred during normal operation, I believe it is necessary to check whether there are any fluctuations in the process parameters on the unit side. If there is cooling water available, check for any fluctuations in the outlet temperature or changes in the flow rate of the cooling water.
After thinking about it some more, the original poster considered whether pipe thermal stress could possibly cause localized deformation of the casing.
It depends on the specific image; in most cases, it is caused by local friction
There should be no dynamic or static rubbing; if there is vibration, its amplitude will be very high. Check whether there are any changes in the turbine’s process parameters such as steam pressure, temperature, and outlet backpressure.