Up Time Magazine- August/September 2008

Figure 11 – Frequencies and Effective Analysis Techniques for Bearing Fault Stage 4. spectrum. 3. As the bearing loses more metal, there will be larger clearances in the bearing. As result, you will witness an increase in the running speed (1X) vibration and its harmonics, i.e. looseness. 4. In the fourth stage the RMS overall level will increase. Because the overall level (according to the ISO standards) is only influenced by vibration below 1000 Hz, it is not until these later stages that it becomes sensitive to bearing damage. at that time you may think the fault is quite severe. However, as the rolling elements continually strike the sharp surface, the edges will become rounded, and the metal pieces may be carried away by the lubricant. The vibration will therefore change. So, there may be situations where the vibration appears to improve – you could be convinced that the bearing fixed itself. Sadly, they don’t make bearings that fix themselves… The EZI way to pump. Data Collection It cannot be stressed strongly enough; the way you mount the accelerometer on the machine will dictate the success of the high frequency techniques (Shock Pulse, Spike Energy, PeakVue, and enveloping). The accelerometer should be mounted as close as possible to the load-zone, and it should be mounted on a clean, flat surface. For the best results, the accelerometer should be stud mounted. Two pole magnets and “stinger” hand-held probes should not be used. Important Note In the article thus far we have discussed the progression of the bearing as though it were a “linear” process. The assumption could be made that all faults develop in the same way, and that there is a gradual degradation of the bearing condition. That is not actually correct. 1. There are many ways that a bearing may fail: cracks, true and false brinelling, rust and corrosion, flaking, skidding, scuffing, fretting, electrical pitting, dents and scratches, and more. (There are excellent application notes by the bearing manufacturers that describe these failure mechanisms – they help you to understand how to avoid the problems in the first place and they allow you to recognize the type of damage and determine the root cause.) For example, if a machine is operated for long periods and false brinelling occurs, you may operate the machine and quickly experience a catastrophic failure. You won’t see stage one, stage two or even stage three characteristics – the bearing went straight to stage four (from the vibration analyst’s point of view). 2. As the bearing fails (depending upon the type of failure) there will be moments when cracks appear, pieces of metal flake away, and so on. At that moment the vibration pattern and amplitude may change. Now there are sharp edges to impact against the rolling elements, and a piece of metal, albeit small, inside the bearing. If you took a vibration measurement www.uptimemagazine.com Conclusion Understanding how and why bearings fail, and understanding how the various vibration analysis techniques work, enables you to get a very early warning of bearing damage, which in turn enables you to be in control of your maintenance and production. If you take care with the data collection methods and settings, and monitor the bearings frequently, you should have fewer unexpected catastrophic bearing failures. And if you take care of the root cause of bearing failures, you will have an even smaller number of failed bearings. Implementing these techniques may take some work, and it may seem that there is no time to make the appropriate changes, but the only way to get out of fire fighting mode is to stop the fires from starting in the first place. Make your ﬂuid dispensing easier with Trico EZI-action™ pumps for quick, clean dispensing of a wide range of ﬂuids. Beneﬁts • Fits 5 to 55 gallon containers • Pumps oil on both the “up” and “down” strokes • Prevents undesired ﬂuid drip • Pumps high viscosity oils • No wearing parts • Color coding system (match pump strap to lids) Jason Tranter is the owner and founder of Mobius and Mobius Institute. With offices in the USA and Australia, the Mobius Institute has training centers in 25 countries. Jason Tranter ran his own business, ARGO, for five years, and then moved to Bainbridge Island, WA when he sold his business to DLI Engineering (ABB) in 1990. Jason is the author of iLearnVibration, iLearnAlignment and the Interpreter spectrum analysis tool, and the author of numerous articles, presentations, and technical papers. Jason can be reached at jason@ilearn interactive.com. You can learn more at www.ilearninteractive.com. Make life EZI. Call Trico. www.tricocorp.com 800-558-7008 67 TRI_drumpumps Uptime 2.937x10.871 1 5/1/07 11:56:50 AM http://www.tricocorp.com http://www.ilearninteractive.com http://www.uptimemagazine.com

Table of Contents Feed for the Digital Edition of Up Time Magazine- August/September 2008

Up Time Magazine- August/September 2008 Contents Upfront Upclose Information Technology Lubrication Infrared Maintenance Management Motor Testing Precision Maintenance Reliability Ultrasound Vibration Upgrade

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