Seek help in analyzing the spectral characteristics of pipeline stress
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After maintenance, the bearing on the coupling side of one compressor exhibited excessive vibration levels. Upon inspection, it was found that there was significant stress in the pipes and that the foundation was loose; however, no corresponding characteristics could be detected in the spectrum. Please help to take a look! 1. The compressor is a single-stage cantilever centrifugal compressor; the motor has a power of 6000 kW and rotates at 1483 rpm. The motor drives a gearbox, which in turn drives the compressor, causing the compressor to rotate at 2060 rpm, with a critical speed of 3800 rpm. 2. During testing, the vibration level on the coupling side of the compressor was relatively high, at 70–80 microns. The vibration level of the bearings on the impeller side was also high, at 13 microns (the normal level being below 10 microns). When the compressor stopped, the vibration level on the V-2500 side did not decrease but instead increased, reaching 150 microns, until the compressor came to a complete stop. 3. During compressor operation, the spectrum of the bearing V-2500 on the coupling side is dominated by the first harmonic at 78 micrometers; there is also a second harmonic, but its value is low at 12 micrometers, while values for other frequencies are very small. The comprehensive analysis chart is shown above. 4. The comprehensive analysis diagram of bearing V2501 on the impeller side during shutdown is as follows: 5. The comprehensive analysis diagram of bearing V2501 on the impeller side during operation is as follows. 6. The comprehensive analysis diagram of bearing V2501 on the impeller side during shutdown is as follows. 7. Bode plot during startup. 8. Bode plot during shutdown. Based on these vibration characteristics, there are several issues: 1. What are the characteristics of the pipeline stress? 2. What are the characteristics of loose foundations? 3. Why does the vibration level of the bearing on the coupling side increase when parking?
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I posted it myself, so I have to promote it myself as well. Everyone is welcome to discuss it; I’ve been really stressed these past few days
http://bbs.hcbbs.com/thread-1315516-1-1.html This is an expert; you can give it a try.
Send over your main shaft center diagram
In the comprehensive analysis chart, the diagram in the lower left corner is the axis position chart!
1. Pipeline stress generally causes the connected machinery to twist and deform, resulting in misalignment; therefore, it is usually at 1 or 2 times the frequency； 2. The characteristic of loose foundation is the first harmonic, which is mainly reflected in shell vibration, with an asymmetric waveform above and below ； 3. Is the acceleration rate during startup high around 600 rpm? If it happens quickly, the increase in speed to 600 rpm upon shutdown is likely due to resonance in a certain component. Since the startup process is rapid, the vibration increase is not significant; whereas during shutdown, the deceleration is slow, so the amplitude of vibration increases noticeably. This is merely an approximate assumption – a thorough analysis requires taking into account process parameters as well as on-site inspections.
1. Pipeline stress generally causes the connected machinery to twist and deform, resulting in misalignment; therefore, it is usually at 1 or 2 times the frequency； From a spectral perspective, there are few features indicating misalignment; the axis trajectory is elliptical, and the bearings on the coupling side mainly exhibit the first harmonic, with very little contribution from the second harmonic. 2. The characteristic of loose foundation is the first harmonic, which is mainly reflected in shell vibration, with an asymmetric waveform above and below ； I suspect it’s the combined effect of pipe stress and loose foundations, characterized by a first harmonic; the waveform can be seen on the comprehensive analysis chart. Please take a look – I really can’t tell. 3. Is the acceleration rate during startup high around 600 rpm? If it happens quickly, the increase in speed to 600 rpm upon shutdown is likely due to resonance in a certain component. Since the startup process is rapid, the vibration increase is not significant; whereas during shutdown, the deceleration is slow, so the amplitude of vibration increases noticeably. This is merely an approximate assumption – a thorough analysis requires taking into account process parameters as well as on-site inspections. From the Bode plot, it can be seen that a ring-shaped pattern appears in the vibration levels during startup; it’s not clear why this happens Please give me some advice.
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I’m reaching out to everyone again; I still don’t understand it