Listen Up: Stop Lube-Related Bearing Failures
Jane Alexander | April 13, 2017
Regardless of industry sector, lubrication methods are crucial to plant reliability and maintenance efforts. Consider the fact that lube-related failures account for 60% to 80% of premature bearing failures. While lack of lubrication and use of the wrong lubricant for an application have been cited as major causes of such failures, over- and under-lubrication are also harmful. Preventing those last two scenarios is one area where ultrasound technology can play an important role.
According to UE Systems (Elmsford, NY), by using an ultrasound instrument to listen to a bearing while applying lubricant and then monitor, i.e., watch, the decibel level, a technician can determine when adequate grease has been applied and, just as important, the threshold at which over-lubrication begins.
In short, when bearings aren’t lubricated properly, friction can cause damage and threaten processes. Ultrasound equipment can read the decibel levels of over- and under-lubricated bearings and indicate to maintenance personnel if adjustments are in order. Consistent dB levels let a technician know that the level of lubrication is where it should be.
Experts at UE Systems describe three tiers of acceptable lubrication practices and where ultrasound technology fits into them.
The baseline lubrication practice is to follow the bearing manufacturer’s recommendations to determine the exact amount of lubrication necessary based on bearing size, speed, and type, and rely on runtime and operating conditions to develop a lubrication schedule. While “good” is a starting place, there is room to improve.
The next level uses ultrasound equipment for more exact lubrication procedures. These tools tell maintenance technicians when to stop lubricating a bearing, rather than hoping the schedule is accurate and guessing at bearing condition. Ultrasound can also inform technicians if there are other problems with the bearing, unrelated to lubrication.
A best lubrication practice is to combine a frequency schedule and ultrasound tools with data collection and trend analysis. By examining the history of lubrication with dB levels and other sound files, maintenance technicians can begin to predict when bearings may be approaching failure and take preemptive action. Alarm levels can be set to alert technicians when lubrication is approaching dangerously low levels.
The best ultrasound programs allow easy integration of data analysis with probes, listening devices, and lubrication tools.
How Ultrasound Technology Works
Air- and structure-borne ultrasound is high-frequency sound that human ears can’t hear. These high-frequency sounds travel through the air or by way of a solid. The ultrasound instrument senses and listens for the high-frequency sound, and then translates it into an audible sound that is heard through the inspector’s headset. The unit of measurement for sound is a decibel (dB) level, which is indicated on the display of the ultrasonic instrument.
Ultrasound can be used in conjunction with (and is supportive of) vibration analysis and other predictive-maintenance approaches. In addition to mechanical inspections of rotating equipment and associated condition-based lubrication programs, applications for ultrasound include detection of compressed air and gas leaks; inspection of energized electrical equipment to detect corona, tracking, and arcing; and inspection of steam traps.
For more ultrasound information and to download a printable infographic on “3 Ways to Incorporate Ultrasound in Lubrication Testing,” visit uesystems.com.