Machinery Lubrication magazine published by Noria Corporation
Issue link: https://www.e-digitaleditions.com/i/847153
here is a misconception in industry that bearings should be lubricated like bushings. Many people are under the impression that if a little lubricant is good, a ton must be better. However, overlubing a bearing can cause the same or more catastrophic problems than underlubing. Although this practice is slowly being eradi - cated as its ineffectiveness becomes common knowledge, the old ways of overlubing continue to persist in some areas of our workplace. DAMAGING PRACTICES It is inherent in the millwright culture to want to see grease oozing out of bearings. We had oilers that would push 20 pumps into a bearing even if grease started spewing out after the first pump. During my training in the lubrication department, one of our more experienced oilers took me to a machine and told me to put in 10 pumps of grease every week. This machine is indoors in one of the cleanest areas of our mill, except for the big piles of grease directly below the bearings. As I put in the first pump, the same volume came spewing out of the sides of the bearing. On another occasion when I was an apprentice mill- wright, a journeyman told me I had to be their "human Q-tip" to go through all the excess grease that had been dumped out of the bearings via overlubrication. Being new, I hesitantly opened the access panel to find calf-deep sludge made up of grease and bark dust. Luckily, he was joking, and I didn't need to crawl in. Unfortunately, this took overlubri- cation to a whole new extreme. This was common practice. It was normal to see puddles of grease. If I came across a place where there wasn't grease oozing out of the bearings, I knew I had better find an oiler to add a little more grease. IMPROVEMENT OPPORTUNITIES We experienced regular bearing failures that were associated with a lack of lubrication. Everyone knows the old saying that hind- sight is 20-20. Well, now we know that lubrication was a factor in all these failed bearings, but more appropriately they were a conse- quence of our overlubrication culture. After going through Noria's Machinery Lubrication training, it became apparent that we had an opportunity for improvement in this area. Our new and improved predictive maintenance (PdM) depart- ment started cleaning up this practice. We did calculations for specific bearings and started to properly lube our machinery. At first, maintenance personnel were indignant, thinking that since grease wasn't oozing out, the bearings were not being lubed. I had to explain that the bearings were finally being lubricated properly. CALCULATING GREASE QUANTITIES Thanks to SKF and its simplified formula, you can easily calcu- late the volume of grease needed by multiplying the bore diameter by the bearing width and a constant of 0.114. If you can safely reach the bearing, you can measure it, but most of the time our T www.machinerylubrication.com | July - August 2017 | 9 www.machinerylubrication.com | July - August 2017 | 9 ML