Hello everyone, hope you're having a great day. Our company is currently running a 24 MW generator powered by a Steam Turbine (refer to attached diagram). We have been encountering sporadic vibration spikes and ongoing phase fluctuations at bearing no. 07 (Generator drive end) and bearing no. 06 (gearbox low speed shaft). The most significant change is in the 1X vibration. Please see the included Polar, Waterfall, and Trend plots for more details. Your professional insight and expertise are highly appreciated. Best regards,
Is the intermittent peak occurring during normal operation of a 24 MW machine? Has this machine undergone previous maintenance? Can you provide the plots and details of the last startup? Additionally, could you please share the plot mentioned in your post titled "Your expert opinion is required"? It is crucial to provide data for experts to analyze in order to effectively solve any issues. Regards, RG.
Dear Rotating Guy, I appreciate your response regarding the recurring issue. The problem occurs during regular operation, starting after June 20, 2018, following the machine's start-up in March of the same year. Last year, the machine experienced multiple trips due to excessive vibration on the generator, which was later sent to the OEM for inspection. A loose retaining ring at the drive end of the generator was identified as the cause, leading to a short winding. The issue was rectified at the OEM facility and the design of the retainer ring was enhanced. Despite initial improvements, anomalies resurfaced after June 20, 2018. Upon analysis of polar plots and spectra, a potential case of intermittent rubbing was considered (attached for reference). However, the regularity of the event occurring approximately every 7 hours raises concerns, as intermittent rubbing typically does not exhibit such precision in recurrence. Best Regards,
Jrva, can you provide a plot showing the trend of this event? Have you noticed an increase in vibration levels during normal operating conditions at a steady state? It would be beneficial to check the voltage gap of the sensor, as a gap of -16 for a prox probe has been known to cause chattering and intermittent peaks in the trend. I believe the issue may not be mechanical, so I would recommend addressing any electrical and instrumentation problems that may be affecting the trend you are seeing. Additionally, please provide details on how frequently the intermittent spikes occur and if any step changes coincide with these spikes. Your data would be greatly appreciated. Thank you.
Dear RG, Please refer to the attached plots for more information. The maximum amplitude of vibration remains constant during steady-state operation, but there has been a noticeable increase in the frequency of these events. Gap voltages show no abnormalities. Vibration levels gradually increase during these events. Best Regards,
Have you noticed any changes in bearing temperatures, oil pressure, or ambient conditions? To rule out the Morton effect, consider adjusting the oil temperature. If possible, utilize an ultrasonic analyzer to combine data with your vibration analyzer using the demodulator (Peak-Vue) function, which can help identify any potential mechanical rubbing issues more accurately.
Hi there, hope you're doing well. Reviewing the data you’ve provided, these could be symptoms of an unbalanced rotor or misalignment, which can cause an increase in the 1X vibration. You might also want to check your coupling, especially if the spikes are present when launching or stopping. It's best if you could do field balancing or perform rotor alignment to potentially rectify these issues. Also, analyse your Phase readings in more depth as they can provide significant details on the problem source. Let us know how it goes - we're here to help.
Hi there! I've had similar experiences with steam turbines we maintain. It seems like your issue might be related to misalignment or imbalance, considering you mentioned increased 1X vibration. Specifically, misalignment could be at the generator drive end (bearing No.07), given the vibration there. Imbalance, on the other hand, might be present at the gearbox low speed shaft (bearing No.06.) Also, don't rule out mechanical looseness leading to phase fluctuations. Regular maintenance like realignment and rebalancing may help. Lastly, are there any recent operational changes that could contribute? Sometimes it could be as simple as a minor operational shift. Hope this helps!
You've provided a lot of detail here which is great. In my experience, it sounds like your system might be experiencing imbalance or misalignment, which are common causes for 1X vibration. Check for any anomalies in your rotor and bearings, such as wear and tear, and align your shaft properly as it might get misaligned over time. You might also want to ensure proper lubrication, as under-lubrication often leads to these issues. Always remember, regular maintenance is key for the smooth operation of such heavy machinery. Hope this helps!
Hi there! It sounds like a challenging situation with those vibration spikes. For bearing issues like you're describing, it's crucial to consider the alignment and balance of both the steam turbine and the gearbox, as even minor misalignments can lead to significant vibration problems. It might also be worth running a thorough check on lubrication conditions or any signs of wear or damage in the bearings themselves. Additionally, reviewing historical data for patterns could help pinpoint any recent changes or correlations. Have you tried any transient analysis to see if the spikes correlate with specific operational changes? Just some thoughts—good luck with troubleshooting!
Hi there! It sounds like you're dealing with some tricky vibration issues. Given that the spikes are happening at specific bearings and are most pronounced in the 1X frequency, it could be worth checking for misalignment or imbalance in the rotor system, particularly around the coupling area. Also, considering the age and condition of the bearings, a thorough inspection for wear or damage might be beneficial. Have you tried any balancing techniques or alignment checks recently? Those could help narrow down the root cause. Good luck, and I hope you find a solution soon!
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Answer: Answer: The intermittent vibration spikes and phase fluctuations in a 24 MW generator could be caused by various factors such as misalignment, unbalance, resonance, bearing issues, or electrical problems.
Answer: Answer: Sporadic vibration spikes can lead to increased wear and tear on components, reduced efficiency, potential damage to bearings, and overall decreased reliability of the generator.
Answer: Answer: Common troubleshooting steps to address vibration spikes and phase fluctuations in a generator drive end bearing may include checking for misalignment, inspecting for unbalance, examining bearing conditions, analyzing electrical connections, and conducting vibration analysis to identify the root cause.
Answer: Answer: Polar, Waterfall, and Trend plots are essential tools used in vibration analysis to help identify patterns, trends, and anomalies that can provide valuable insights into the behavior of the generator and aid in diagnosing the root cause of vibration issues.
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