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Effective lubrication for smooth operation
SKF's Phil Burge explains the importance lubrication in order to minimise maintenance and operating costs, and looks at the latest technology to enable this
Effective lubrication of moving surfaces is essential in almost all industrial applications, ranging from conveyors, chains, shafts and cables to steering axles, pivot arms and lift points. Although a large number of systems and component sets are supplied as maintenance free or sealed for life, there are many more devices that need regular lubrication to ensure that they operate effectively and over the long term.
Unfortunately, lubrication is often carried out inefficiently, at best over lubricating equipment, and so wasting materials and polluting the surrounding area, or at worst lubricating moving parts at irregular intervals or, if they are particularly inaccessible, failing to lubricate at all. To address these problems, leading manufacturers such as SKF have developed a new generation of automated lubrication systems. These include centralised systems for use on mobile plants and forklifts, combined oil and grease systems for materials handling robots, and dry lubricant sprays for the surface of conveyors and guide rails.
In particular, centralised lubrication systems have been designed to enable multiple lubrication points or groups of points to be supplied with varying amounts of precisely metered lubricant from one central reservoir. This type of system ensures that every lubrication point, particularly those in hard to reach areas, receives an exact and carefully programmed level of oil or grease at the appropriate intervals and, if necessary, in the appropriate sequence, while eliminating the risk of contamination due to over lubrication.
In addition, this type of system functions automatically while machinery is still running and bearings, shafts or conveyors are still moving, ensuring that oil and grease are distributed consistently across all moving surfaces. As a result, wear and tear, and associated downtime, repair and maintenance costs can be significantly reduced, with the service life of bearings being increased by a factor of at least four in most applications.
As an added benefit, maintaining a centralised lubrication system is generally limited to topping up the lubricant reservoir and an occasional inspection of the lubrication points. When compared with manually maintained lubricating equipment, implementing a centralised system can reduce the consumption of oils and greases by up to 90% due to its precise metering rates, which accurately adhere to the demands of the equipment.
Centralised lubrication systems are available with a broad range of features to suit a wide range of applications. Single-line systems from SKF, for example, typically feature piston distributors to feed metered quantities of lubricant to bearings, cams, gears and power trains, making them ideal for use on printing machines. Typically modular in construction, these systems can easily be extended by adding additional lubrication points as the needs of the application change, and can serve up to several hundred points from an individual supply unit and dedicated control mechanism.
Other types of circulating oil systems are available, combining a constant supply of oil with cooling by collecting the oil or grease after it leaves each lubrication point and then filtering and re-circulating it; this type of system is ideal for lubricating standard bearings and can be particularly cost effective in large power plants or cement works. By comparison, progressive and zoned lubrication systems are designed to provide a sequential and metered supply of lubricant to individual components or parts of a production line.
Likewise, travelling lubricators are ideal for use with moving conveyor chains on assembly lines, or painting and coating lines, to ensure that every chain link is effectively lubricated as it moves; the latest travelling lubricators can work with chain conveyors moving at speeds of up to 2m/s. It is also important to select the correct type of lubricant for each application, taking into account factors that may affect the long term chemical and physical characteristics of the oil or grease and thus its ability to protect moving parts. Typically, these factors include high operating temperatures, fast line speeds, heavy bearing loads or the use of steam cleaning systems, each of which can degrade the performance of lubricants.
Lubricating grease for rolling element bearings typically consists of a thickener, oil and selected additives, which improve desired properties. The oil, which can be mineral, fully synthetic or a blend of the two, provides the lubrication while the different additives are introduced to influence the corrosion resistance properties or to provide a protective layer over the metal surface of a bearing under extreme conditions. Additives also improve the viscosity behaviour of the lubricant at varying temperatures. The task of the thickener, meanwhile, is to absorb the oil and release it in small quantities onto the bearing element over a prolonged period.
By altering oil viscosities, thickeners and additives, grease manufacturers can formulate a lubricant to suit predefined applications and operating conditions. By contrast, mixing grease types directly onto a machine at plant level can result in long term problems and should be avoided. Manual mixing can have the same effects as contamination, resulting in either softer grease that allows lubricant to flow away from the application at a lower temperature or harder grease that decreases its ability to lubricate.
It is widely accepted that accurate and appropriate lubrication is needed for almost all industrial applications. Through selection of the correct method of lubrication and type of grease or oil you can realise benefits of long term, trouble free operation of your equipment, with minimum maintenance and downtime, as well as increased line or machine performance.
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