Machinery Lubrication magazine published by Noria Corporation
Issue link: https://www.e-digitaleditions.com/i/190260
COVER STORY 3 Other Lubrication Problems to Avoid Besides the top five problems, there are a few honorable mentions that should be included in any discussion of recurring lubrication issues affecting industry. These are problems that aren't quite as common but still deserve to be mentioned. Constant-level Oilers Although constant-level oilers are great for providing small amounts of oil to a sump and replenishing lost oil, these devices require proper installation and maintenance. They should be installed on the appropriate side of the housing so the shaft rotation is toward the oiler. This is more critical on smaller sumps. Also, the oiler must be installed straight, i.e., level and perpendicular to the ground. Finally, the oil level inside these devices should be set so half of the bearing's bottom element is submerged in oil. When using constant-level oilers, it is best practice to install a bull's-eye sight glass on the opposite side of the housing from the oiler to ensure the proper oil level is maintained. Sediment can block the piping and starve the bearing for oil. Air pressure can raise the oil level, causing increased drag and excess heat in the housing. With the sight glass in place, these issues can be recognized and corrected before any lasting damage is done. High-speed Grease Many facilities use a general-purpose grease for almost everything in the plant. However, a multi-purpose grease can cause problems in high-speed bearings. Fan bearings, motor bearings and other bearings that rotate at several thousand revolutions per minute may require a grease with a lower viscosity than what is used for slower, more highly loaded bearings. Most electric motors can be effectively lubricated by a grease with a base oil viscosity of 100 centistokes. If a higher viscosity grease is used, viscous drag can occur, which may result in higher operating temperatures and increased torque requirements to turn the bearings. As the temperature increases, grease can drain from the bearing quicker, which in turn can cause the bearing to fail due to high heat or lack of lubricant. To prevent this problem, assess all bearings and calculate the necessary operating viscosity. Next, select a grease that provides the required viscosity and the appropriate additive package for the application. Improper sampling points and hardware may result in samples that are full of historic data. A primary point is where routine samples are drawn from to provide a snapshot of the entire system. The best place for a primary sample is on the main return-line manifold, before any return-line filters and in an area of turbulent flow (most often an elbow). Secondary points should be installed in the oil return line after each lubricated component. Secondary points allow you to pinpoint problems in the system after an alarm has been triggered by the primary point. In conjunction with sampling hardware installation, all technicians should be trained in the proper way to pull samples. All sample tubing should be flushed with five to 10 times the volume of dead space. Great care should also be taken to reduce the amount of contamination introduced into the sample during the entire process. 3. Overgreasing Most plants I visit do not recognize that grease guns are precision instruments. They also fail to see the problems that can be caused by the misuse of grease guns. Just like many other people, I was taught to grease a bearing by simply attaching the grease gun and working the lever until grease was seen purging from somewhere. While this may be effective for hinge pins and other applications where purging grease won't cause damage, it shouldn't be employed One-dimensional Filter Carts Filter carts offer many benefits, including increased lubricant life and reduced equipment failures. They are great tools for any lubrication program and should be used extensively to decontaminate both new and in-service lubricants. They can be employed to drain oil quickly, top-up with clean oil, flush out lines and hoses, etc. Whenever I walk through a facility and see a filter cart not in use but sitting in the lube room, I think to myself, "what a waste." These systems should never sit unused in a room somewhere. The term "onedimensional" refers to how these machines are often utilized. Many plants only use these carts to transfer oil from a drum to a reservoir, thus limiting their purpose. So avoid type-casting filter carts into a single role and use them for everything you possibly can. evaluated for the proper sampling hardware. Splash-bathed components such as bearings and gearboxes can be equipped with minimess sampling valves with pilot tube extensions. These extenders can be bent up into the "live" zone next to the bearing or gear teeth. Circulating systems should be examined for the best possible sampling points as well. These systems typically require several points. 12 | September - October 2013 | www.machinerylubrication.com Overgreasing can result in higher operating temperatures, premature bearing failure and an increased risk of contaminant ingression. for all grease applications. Overgreasing is a very common problem and can result in higher operating temperatures, premature bearing failure and an increased risk of contaminant ingression. Bearings require a set volume of grease to be properly lubricated. A popular formula used to determine the volume of grease needed is the outside diameter (in inches) multiplied by the width (in inches) multiplied by 0.114. This will provide the