Up Time Magazine- June/July 2008

process will have a definite life. For example, rolls that move steel in a steel mill, or pump impellers that run in an abrasive or corrosive medium, will wear out. But the motors, gearboxes, bearings, etc that lead up to those components can have an indefinite life. Now let’s look at the reliability of some of the key components in our equipment. Avg ISO Code 24/21 23/20 22/19 21/18 20/17 19/16 18/15 17/14 16/13 15/12 14/11 13/10 12/9 Avg Hours between Breakdown 200 250 325 430 600 800 1050 1400 1900 2600 3800 5000 6500 Relative Life Factor 0.19 0.24 0.31 0.41 0.57 0.76 1 1.33 1.81 2.48 3.62 4.76 Flatness & Bore Alignment Bearings There have been numerous surveys done on the cause of failure of rolling element bearings. This data is from SKF bearings, the world’s largest bearing manufacturer. The numbers may vary somewhat from one source to another but the underlying message is still the same. SKF say that 34% of bearing failures are the result of incorrect installation or wrong fitting tolerances, 36% are due to contamination and lubrication problems3. That’s 70 % before we even look at other skills and practices issues such as shaft alignment and balancing. Regardless of the percentages, we should not be having any bearing failures. Rolling element bearings are made to tolerances of millionths of an inch (.025 micron). They are one of the most precise things that mankind makes. If they are properly selected, properly installed, and properly lubricated, they should last indefinitely. This is supported by SKF, who have revised its formula for calculating bearing life.4 Load Load P P 6.19 8.57 19.05 11/8 10/7 9000 20000 LEVALIGN® Figure 3 - Relationship between ﬂuid cleanliness and breakdown frequency, calculated by the British Hydromechanics Research Association. I have not had any experience, nor have I found any data, that shows that rolling element bearings fail due to faults induced during their manufacture. While undoubtedly this may occur from time to time, the inescapable conclusion is that we cause our bearings to fail. BORALIGN® Lubricants Lubrication and contamination are significant issues, not just for bearings but for rotating equipment in general. Research on hydraulic systems and gearboxes shows the impact of contamination on equipment life. The table in Figure 3 is from the British Hydromechanics Research Association, and it shows the relationship between fluid cleanliness and breakdown frequency4. A cleanliness level of 18/15 is fairly typical and has been chosen to have a relative life of 1.0. Now, if we improve the cleanliness level to an achievable 12/9, then we can expect to increase the life of the components by a factor of 6! And remember, this is just from improvements in lube cleanliness. Further benefits can be gained from improvements in other skills and practices issues. h Watc O E VID ne Onli Pu Life Life Figure 2 - Revised SKF Bearing Life Formula As shown in Figure 2, SKF now says that with clean oil, there is a load (Pu) at which the life of the bearing can be unlimited. Their data also shows that contamination can reduce the life of the bearing by a factor of up to 500. Laser tools for demanding measurement tasks. 305-591-8935 • www.ludeca.com www.uptimemagazine.com 11 http://www.ludeca.com http://www.uptimemagazine.com

Table of Contents Feed for the Digital Edition of Up Time Magazine- June/July 2008

Up Time Magazine- June/July 2008 Contents Upfront Upclose: The True Cause of Most Machine Failures Information Technology: Finding Future Perfect Lubrication: Building an Oil Analysis Winner Maintenance Management: Hidden Ways to Increase Safety Infrared: Air Barriers Lower Energy Costs, Increase Profits Motor Testing: Efficient Motor Repair, Part Deux Precision Maintenance: Good Maintenance, Smart Maintenance Reliability: Common Errors in Root Cause Analysis Ultrasound: Avoid the Baghouse Blues Vibration: Don't Let Your Sensors Get Eaten Alive Upgrade: Lining It All Up

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