| dc.description.abstract | This paper discusses the diagnosis, further analysis and resolution of abnormally high vibration and noise detected on Lube Oil (LO) screw pumps A & B supplying a Turbo Expander Compressor (TEC). During the initial investigation on-site, on 22nd September 2021, the portable data collector was used to capture individual samples across the LO Pump B train. At Stage 5, the Pump vibration was measured as satisfactory. However, when the TEC entered Stage 7 operation increased vibration and noise were observed at the machine skid (Figure 5). A significant number of harmonics were generated during this time, as well as amplitude and impacts in the acceleration time waveform (Figure 6). The conclusion from the vibration data was that the flow was being disrupted, and the potential root cause was the new style LO filters or contamination resulting in blockages of the LO pipework, the former being the more likely theory. The end user requested further confirmation of this theory, and thus a multi-channel analyzer and temporary casing velocity/acceleration transducers were deployed across the train and pipework. This would allow a further picture of the rotor dynamic behavior of the trains to be developed and allow identification of any apparent malfunctions and meaningful, actionable recommendations for future work and/or operation of the trains in question. Investigation of LO Pump A using the DSPI, low-level spikes were observed in the vibration data (Figure 13). Overall, the frequency components for LO PUMP A were comprised of 1X and harmonics of 1X (Figure 15 to Figure 17). The impulse events were seen to cause very slight increases across multiple harmonics (Figure 18). During the test run of LO Pump B, elevated vibration was observed across the Pump, Motor Axial and pipework during Stage 7. Examination of the spectral data showed increased activity in 1X and harmonics of 2X (Figure 21 to Figure 26). Overall, the behavior measured at LO Pump A & B indicated an issue with the flow through the pump. The high-resolution data from the DSPI verified the initial conclusions of the portable data collector, that an issue with the flow through the pump was occurring. It was recommended to the end-user that the filters be exchanged with those of the original design. Several weeks later, the LO filters were replaced with a design comparable to that of the original filters, and the vibration levels returned to normal levels. Overall, this confirmed the inappropriate filter design was causing an excessively high filter DP which resulted in disruption of the flow regime through the LO pumps, with high vibration merely a symptom of this behavior | |
