Published: 21 August, 2007
Phil Burge, marketing manager at SKF, discusses how the latest developments in automated centralised lubrication systems can make a considerable contribution to the improvement of production processes throughout a plant.
The effective lubrication of equipment is essential for the smooth running of a diverse range of production applications; however, the process is commonly managed manually, which can often lead to machinery being either under or over lubricated. The results of this can be significant, with over 36% of all bearing failures alone resulting from the incorrect specification and inadequate application of lubricant.
In response to these issues, a new generation of automated lubrication systems has been developed, which includes both advanced centralised lubrication systems, running either oil or grease, and dry lubricant sprays, ideal for use in a range of industrial plant applications. These latest systems offer production engineers an effective tool for ensuring the reliable and productive operation of machinery.
The problems with manual lubrication
Manually applying lubricant introduces a number of problems as it allows the potential for human error and negligence. In addition to posing potentially serious health and safety and environmental risks, over-lubrication is extremely costly to a business, resulting in considerable amounts of wasted materials, while at the other extreme, under-lubricating systems and components at irregular intervals typically leads to reduced operating efficiency and an increased chance of equipment failure, ultimately resulting in escalated maintenance costs and downtime. In some instances, lubrication is neglected completely, particularly where components are inaccessible, again with potentially disastrous results.
Automating the process
Although manual lubrication can be an effective option, especially on smaller or less complex machines, the real potential for error, and the cost of labour, makes it simpler to use the latest automated lubrication technology. In particular, this will increase the efficiency of lubrication distribution on a production line, cutting costs and increasing the performance of equipment.
Among the latest solutions are centralised systems that enable lubrication points or groups of points to be supplied with the correct amount of lubrication for optimum performance to be achieved. A central reservoir distributes the lubricant to each point, eliminating the previous problems encountered with having to access difficult to reach areas, and ensuring that oil and grease are distributed consistently across all moving surfaces, significantly reducing wear and tear. These systems also ensure that grease is distributed at the appropriate intervals and, if necessary, in the appropriate sequence.
The latest centralised lubrication systems are able to operate automatically while machinery is still running and bearings, shafts or conveyors are moving. As a result, significant reductions can be made in downtime, repair and maintenance costs. It is worth noting that in many cases, by exchanging manual lubrication processes for the automated alternative, the operating life of bearings can be increased by four times or more.
The maintenance requirements for these systems are considerably lower than those associated with manual lubrication, and are generally limited to topping up the lubricant reservoir and occasionally inspecting the lubrication points. Furthermore, when compared with manually maintained lubricating equipment, implementing a centralised system can reduce the consumption of oils and greases by up to 90%, allocating the correct amount of lubrication when necessary.
A range of solutions
A number of centralised lubrication systems are available, which offer a range of features and settings depending on the requirements of a particular application. Single-line systems typically feature piston distributors to feed metered quantities of lubricant to bearings, cams, gears and power trains. These systems can easily be expanded by adding additional lubrication points as an application grows and evolves. Indeed, one single-line system can serve up to several hundred lubrication points from an individual supply unit and dedicated control mechanism.
Additionally, there are a range of solutions available that have been specifically developed for providing a sequential and metered supply of lubricant to individual components or parts of a production line. These include progressive and zoned lubrication systems, and travelling lubricators, which 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.
While single point lubrication devices powered by gas cells can be used effectively in remote or hard to reach areas where a local power supply is unavailable, such as remote areas of factories or in inaccessible plant or mobile equipment, a centralised system can often offer a more suitable solution for critical applications, where maintenance needs to be minimised.
The new generation of centralised battery pack systems are extremely efficient, running at 18VDC and powering a control unit and lubricant distribution and pump unit capable of supplying multiple lubrication points for extended periods. The systems can supply grease or oil from a single 1.0 litre reservoir at pressures of up to 150 bar, ensuring a consistent flow of lubricant even at extremely low operating temperatures.
These systems operate at pre-programmed intervals, which can easily be set and stored via the control unit, with a three-digit LED providing feedback on system operating status. As a result, battery life is often as high as 24 months, considerably reducing the need for regular maintenance.
The right lubricant
For the latest automated lubrication systems to operate most effectively, it is crucial that the correct type of lubricant is chosen for each application, taking into consideration factors such as high operating temperatures, fast line speeds and heavy bearing loads, which may affect the long term chemical and physical characteristics of the oil or grease.
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 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.
It is possible for lubricant manufacturers to formulate a lubricant specifically for predefined applications and operating conditions, by altering oil viscosities, thickeners and additives. By contrast, mixing grease types directly onto a machine at plant level should be avoided, as it can result in long term problems. This type of 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.
With the need to improve efficiency and reduce waste in production process perhaps more important than ever before, the ability to lubricate equipment accurately and appropriately is essential. The latest generation of centralised lubrication systems, together with specifically formulated greases and oils, enable production engineers to reduce considerably maintenance requirements, machine downtime and accidents, ultimately resulting in increased productivity and reduced costs.
For further information please visit: www.skf.co.uk