Dear colleagues, Greetings! Our Ammonia Plant is currently utilizing a Synthesis gas compressor that is powered by a steam turbine. Please refer to attachment no. 1 for detailed information about the compressor. Following the overhaul of IPC and HPC, the compressor was started in February 2018. Since then, there has been a gradual increase in the thrust of the LPC. From February 2018 to July 2018, the thrust at the LPC has risen from approximately 5.5 mils to around 8.3 mils, and this trend is continuing. On June 26, a minor leakage was noted from the flange of the HPC barrel, leading to a gradual increase in vibration levels at IPC bearing no. 10. The vibration levels have escalated from about 32 microns to 60 microns at 10X (VT-13H) and from 35 microns to 56 microns at 10Y (VT-13V) since June 26. To gather data, an ADRE was installed on the machine on July 11, 2018 (see attachment no. 01 for plots). Furthermore, variations in vibration levels and phase have been observed at bearing no. 09 (refer to attachment no. 01). Spectrum plots indicate changes in 1X vibration and phase at both bearings of IPC (bearing no. 09 and 10). During data acquisition, an event was recorded where a sudden change in phase (approximately 10 degrees) was observed at the HPC bearings. However, only a slight increase in vibration levels was detected at 11X, as shown in the attachment. The spectrum plot for this period displays peaks at 0.315X, 0.625X, and 1.8X, but the amplitudes are relatively low. The overall vibration levels at both HPC bearings remain consistent with previous readings. Please be informed that the center line plot for all bearings does not indicate any significant alterations. We kindly request your expert opinion on this matter. Attachment(s): Attachment No. 01.pdf (1.57 MB) - 1 version
Can you please show me the Orbit plot and check for any Morton effect? This can help in analyzing the performance of the system and identifying any potential issues.
When it comes to axial displacement in LP compressors, maintenance activities are typically performed during overhauls of the IPC and HPC. It is important to consider the prestretch of coupling values and conduct regular maintenance of the gearbox. Radial vibrations may occur at the IPC after a leakage is noted, with vibrations returning to normal levels beforehand. Analyzing the trend of vibration values from February 2018 to July 2018 can provide valuable insights. Consider correlating the vibration patterns of bearings 8, 9, 10, 11, and 12 with process parameters to identify any changes. Additionally, explore tools such as polar plots, waterfalls, and orbits to monitor vibrations. Monitor bearing temperatures and clearances closely, as changes in bearing 9&10 may be attributed to 1X frequencies and phase shifts. This could be influenced by process variations or minor rubbing - further data analysis is needed for a conclusive assessment.
| view attached (2) Dear All, Thank you for your valuable contributions. In addition to the information provided earlier, the thrust levels at the LPC and HPC casings were consistently increasing, while there was no significant change in the radial vibration levels at the inboard and outboard bearings of both casings. However, the radial vibration levels at the outboard bearing no. 10 of the IPC casing showed a continuous increase in both directions, along with variations in the radial vibration at the inboard bearing no. 09. Interestingly, there was no change in the thrust levels at the IPC casing. Upon reviewing the machine drawings, it was discovered that the thrust probes at the LPC, IPC, and HPC casings measure the thrust runner (a collar installed on the shaft with a key) for thrust measurement. It was suspected that the runner on this shaft had become loose, leading to inaccurate axial position measurement, as the thrust at the LPC and HPC casings continued to increase while the thrust at the IPC casing remained unchanged. A comparison of the current ADRE data with previous startup data revealed a significant change in phase at bearing no. 10 and a continuous increase in vibration. On the other hand, there was a slight reduction in overall vibration at bearing no. 09, but with intermittent rubbing observed near the bearing. As there were no alerts for thrust levels at the HPC & IPC casings and radial vibration at the IPC casing, shutting down the machine initially was not deemed necessary despite the concerns of rubbing near bearing no. 09 and a suspected loose runner near bearing no. 10. After dismantling the IPC casing and examining the thrust bearings at the outboard side, it was discovered that the key of the thrust runner was slightly sheared, resulting in a loose runner on the shaft. Additionally, the centering ring spacer of the runner was worn out, with a small groove near the centering ring spacer. Fretting marks were also found on the shaft shoulder in this area. On the inboard side, slight wear due to rubbing was observed on the side wall of the last impeller closest to bearing no. 09. The rotor of the IPC casing was replaced with a refurbished one, and overhauling was done on the LPC and HPC casings. The machine was restarted after a 5-day shutdown and is currently operating satisfactorily. Please refer to the attached files for more details. Attachment(s) SNAPS.pdf 727 KB 1 version Attachment.pdf 240 KB 1 version
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The compressor is now operating efficiently. Kindly provide the adre data before and after shutting down the compressor, including the axial/thrust bearing clearances. This information will be valuable for conducting a root cause analysis.
Based on the details you've provided, it seems like this could potentially be an issue related to the mechanical seal within the compressor or an underlying issue with the bearing alignment itself. The slight vibration increase at 11X and the phase changes could lend to this theory. I'd be interested to see how the other measurements skew over the next several days. However, it might be prudent to schedule for a professional inspection of the bearings and seals soon to catch any developing faults before they lead to a major problem. Also, don't forget to check the lubrication system as inadequate lubrication can cause similar fluctuations.
It seems like you're dealing with a complex situation. From your explanation, it's clear that the rise in thrust and vibration levels at the LPC and IPC respectively indicate some kind of mechanical stress or possibly a misalignment issue. The leak from the HPC barrel could also be a symptom of these increased vibrations. While the spectrum plots and the center line plot don't show any drastic changes, it might be worth investigating the moving parts of the compressor's system for abnormal wear or stress. I’d suggest getting a specialist to inspect the mechanical parts of the system and run an in-depth vibration analysis if possible.
Hi everyone! Thanks for sharing such detailed information about the compressor's performance. The gradual increase in LPC thrust is definitely concerning, especially with the recent spike in vibration levels at the IPC bearings. It might be worth investigating if the flange leakage is contributing to instability, as that can often lead to unwanted dynamic loads on the compressor. Additionally, the observed phase changes at bearing no. 09 could indicate a potential misalignment or resonance issue. I recommend closely monitoring the vibration data from the ADRE to see if any patterns emerge or if more drastic measures need to be taken. Regular maintenance checks are crucial at this point to prevent any further escalation. Looking forward to hearing others' thoughts on possible root causes!
Hi there! Thanks for sharing the detailed update on the compressor's performance and the recent developments with the vibration levels. It sounds like you're on top of the situation with the ADRE installation for monitoring. The gradual increase in thrust at the LPC is concerning, and it might be worth looking into potential misalignment issues or wear in the bearings, given the corresponding rise in vibration levels at IPC bearing no. 10. The phase shift at the HPC bearings could also be a sign of a developing issue—maybe a closer inspection of the coupling and alignment could help. I’d recommend collaborating with your vibration analysis team for deeper insights into the spectrum plots as well. Keep us posted on any findings!
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Answer: - The gradual increase in thrust at the LPC could be due to issues such as wear and tear, misalignment, or other mechanical problems within the compressor components.
Answer: - The rise in vibration levels at IPC bearing no. 10 could be attributed to the impact of the leakage on the bearing, leading to increased friction, misalignment, or other issues affecting the bearing's performance.
Answer: - Variations in vibration levels and phase at bearing no. 09 can be analyzed using spectrum plots and monitoring tools like ADRE. To address these variations, it is essential to investigate potential causes such as mechanical faults, alignment issues, or component wear that could be affecting the bearing performance.
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