Background
This case study details detecting coupling wear through vibration analysis in a nutrition facility in Ireland. The Eastway team has been supporting the on-site maintenance personnel in this plant since 2009, both on-site and through online condition monitoring. Eastway provides different services to this company, including remote monitoring, on-site vibration analysis, ultrasonic leakage surveys, steam surveys, and thermography inspections for this plant. This nutrition plant has a proactive maintenance team that works closely with Eastway and provides regular feedback on asset condition.
Case description
In September 2023 during the monthly vibration survey, the condition monitoring engineer noticed high vibration values in velocity (mm/s RMS) at the vacuum pump. Vibration data was gathered from the field with a portable FFT analyser. Refer to Figure 1, which shows the motor drive end velocity (mm/s RMS) trend, indicating an unexpected increase in vibration values.
Figure 1. Velocity (mm/s RMS) trend from motor drive end test point.
Recommended Action
The Eastway condition monitoring team carried out a comprehensive examination of the vibration data, which included analysing velocity (mm/s RMS), acceleration (g RMS), and demodulation (g RMS) data.
The findings of the analysis revealed various signs of coupling wear deterioration, including an increase in low-frequency vibrations, changes in vibration amplitude, and the presence of harmonics in the vibration spectrum observed in both the motor and pump. Figure 2 illustrates the velocity FFT spectra, showing the dominant frequency of the running speed at 1X RPM and its harmonics (2X, 3X, and 4X). Based on this analysis it was recommended to the site maintenance personnel to inspect the coupling condition and replace it at the next available opportunity to prevent further damage.
Figure 2. Velocity (mm/s RMS) FFT spectra at the Motor Drive test point showing harmonics of 1X.
Action taken
As recommended by Eastway, site maintenance personnel carried out an inspection, observed the wear on the coupling, and replaced it accordingly. This action reduced the excessive vibration previously detected at the motor and pump test points. Consequently, the values returned to satisfactory levels and have remained stable since. Refer to Figure 3, which displays the velocity (mm/s RMS) FFT spectrum comparing two readings: the top sample is from September 27, 2023, when the failure was detected, and the bottom sample is from October 24, 2023, after the coupling replacement. It is evident from below, after the coupling job running RPM harmonics (1X,2X,3X & 4X) amplitudes settle down.
Figure 3. Velocity (mm/s RMS) FFT Spectrum comparing two readings, top sample is from 27th September 2023 (before works) and the bottom sample is from 24 October 2023 (after works)
Results
This case study prevented further deterioration of different components of the vacuum pump. Thus, in addition to identifying problems and dramatically reducing downtime, the detection also significantly reduced the man-hours required to repair the equipment and ensured the maintenance work was carried out in an efficient way.
The table 1 below summarises the importance of having predictive maintenance in place to detect failures, in this case coupling wear was detected using vibration analysis before it progressed to a critical level, allowing corrections to be carried out before costly system failures occurred, thus maintaining operational continuity.
Table 1. Estimated cost savings
