Machinery Lubrication magazine published by Noria Corporation
Issue link: https://www.e-digitaleditions.com/i/934530
12 | January - February 2018 | www . machinerylubrication.com 0.3 0.2 0.1 -0.1 -0.2 -0.3 0 4 8 12 16 0 Acceleration in Gs Time (Revolutions) Figure 9. Impacting and looseness in the vibration signature not cause a mechanical problem? Did the analyst not recognize or catch a problem in the vibration signature? Are the ISO cleanliness alarms set too tight? In another example of poor inter- action between the two technologies, the trend plots provided by the oil analyst showed the iron content and ISO cleanliness codes of the oil samples as being high for more than eight months (see Figures 3-4). Meanwhile, the vibration analyst only reported leaking seals on the gearbox (Figure 5) and no mechan- ical defects. A reliability engineer might wonder why the two analysts did not mention that leaking seals allow for the ingression of contaminants. is could have been the perfect opportunity to mention this link and help the asset owner understand the importance of fixing the leaks. e asset owner might also question the reason for concern if the leaks and dirty oil are not causing any other problems. For a final example of poor interaction, consider the trend plots presented by an oil analyst that showed the ISO cleanliness code in the oil samples as being high for more than 16 months (Figure 6), while the vibration analyst reported intermediate gear wear (Figure 7). ese results likely would have prompted a number of questions from the asset owner, such as: Are these two conditions related? Where are the analytics on ferrous wear? A re particles in the oil contaminants causing the gear wear or are there wear particles from the gear wear? If the oil is not dirty, what caused the gear wear? Why did neither analyst discuss the implications of the other findings? EXAMPLE OF GOOD INTERACTION In the following example of proper interaction between oil analysis and vibration analysis, the trend plots from the oil analyst showed a high iron count in the oil samples for more than 16 months (see Figure 8). e vibration analyst reported impacting and loose- ness as well as a possible problem with a thrust washer (see Figure 9). From the perspective of a reliability engineer, this was a well-reported defect. Both analysts referenced the other's findings, and it was apparent they had communicated and likely discussed the results before submitting their report. Although the analysts did not state that one condition caused the other, they indicated the high proba- bility of such an occurrence. In conclusion, both oil analysis and vibration analysis are powerful inspection methods that are capable of identifying faults that the other cannot. However, there are also many defects with bearings and gears in which these technologies should be in lockstep. When they are, confidence in the inspection process grows and the asset owner can be more certain of the right action to take. ML 0 50 100 150 200 250 300 350 400 450 500 7/6/2015 - 10/9/2015 - 4/5/2016 - 8/2/2016 - 10/18/2016 - 1/15/2016 - 141 142 470 334 Iron Iron alarm Iron alert 139 240 Figure 8. High iron counts for more than 16 months COVER STORY