Improving Rolling Mill Lube Oil Performance and Useful Life

When rolling element or sleeve bearings operate under extreme conditions, it’s more important than ever to follow proper lubrication selection and maintenance procedures to maximize effective life and efficient performance. Long-term analysis of field data shows that the lack of proper lubrication is the most commonly cited cause of bearing failure and accounts for over 40 percent of breakdowns. Bearings for high temperatures must be properly maintained and lubricated to withstand high heat.

The manufacturer using the bearing in his equipment, not the ball bearing manufacturer, determines the anticipated life of a ball bearing. This life, once determined, is called the L10 life of the bearing and it is based on the premise that 90% of the bearings will last a certain amount of revolutions before they experience metal fatigue.

Following this meeting, a professional consultant visited Schmid to determine if the right oil and lubricants were being utilized to meet maintenance goals. After much testing and analysis, the consultant determined that the oils in use were not as high quality as the company originally thought. With hard work and determined mechanics, every piece of equipment and every truck was changed over to the new brand of oil and the company seemed to have fewer lubrication related problems. Still, large amounts of money were poured into repairs and the desired results were not fully achieved.

Rotating-element bearing manufacturers measure the reliability of their bearings using a Load-Life calculation rating, which is known as the L10 rating life. To achieve its design rating, the manufacturer assumes the bearing will be run in a clean operating environment. This takes into account providing an adequate lubricant film (adequate described as a film equal to, or greater than, the composite roughness of the two mating surfaces) of the correct viscosity for the designed maximum bearing speed and operating temperature ratings.

Industry spends millions of dollars each year on improved filtration technology in an attempt to reduce particle contamination, with some of the more advanced companies reducing failure rates by up to 90 percent simply by controlling fluid cleanliness. However, in some industries and environments, water is a far more insidious contaminant than solid particles. Water contamination is often overlooked as the primary cause of component failure.

One of the best ways to achieve fault-free operation of paper machines is to ensure the proper lubricant is applied to the frictional surfaces. Most paper machines have hundreds, if not thousands, of lube points that require periodic application of oil or grease. There are bearings, gears, couplings, journals, cylinders and valves which must all receive the correct lubricant to survive the rigors of the paper-making process.