High vibration in the shaft bearings of the steam turbine generator set?
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May I ask, before the major overhaul of the steam turbine generator set, the vibration levels of all bearing shells were normal; yet after the overhaul, the vibration level of bearing shell No. 3 became high, reaching the alarm threshold. What is the reason for this? (The steam turbine generator set has two shafts with four bearing shells in total, connected rigidly; the 3rd shaft bearing shell is the front bearing of the generator rotor, and there are no issues with its installation alignment or anything else.) Could someone experienced give some advice?
If the coupling is aligned and there are no issues with the foundation bolts or the motor bearings, it’s possible that the clearance of one of the shaft bearings is too large； The clearance deviation around a single bearing shell is relatively large ； The deviation in the clearance direction of the two shaft bushings on the same axis is out of tolerance. Measure the clearances of each bearing shell; if they are out of spec, adjust them again.
The analysis of vibrations is the most complex and requires multi-faceted analysis. In a situation like yours, there are mainly several possibilities: 1. The bolts of the coupling should be numbered when they are removed; they need to be reinstalled in the same positions from which they were taken. If this is not done properly, it could affect the dynamic balance. Also, it’s important to consider whether the bolts were tightened sufficiently when they were removed ； 2. Bushing repair and grinding; excessive bushing tension or clearance ； 3. Has the turbine rotor been cleaned? 4. How is the vibration of the other few watts? Does it increase suddenly, or does the vibration rise slowly as the speed increases?
When the vibration at the drive end is high, it is also necessary to consider the alignment of the coupler; not only cold-state alignment needs to be taken into account, but also whether there are any deviations in the alignment after operation in the hot state.
It is recommended to check the condition of the lubricant, as well as consider things like ferrography analysis
Check the installation clearance, contact area, and pre-tightening force of the 3# tile; if it is a tilting tile, inspect the tile itself
Please attach the spectrum analysis graph and the axis trajectory graph
The coupling bolts are not numbered； The turbine rotor was cleaned of scale, and the accumulated salts and deposits were removed by sanding ； During the speed-up process, the increase is gradual; the greater the load, the higher the vibration level of shaft 3#