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Product category: Bearings and guideways - rotary and linear
News Release from: SKF UK | Subject: Bearings and factory efficiency
Edited by the Manufacturingtalk Editorial Team on 25 September 2006

Bearings choice can increase factory
efficiency

Factory managers are under increasing pressure to raise productivity by improving the reliability and performance of their plant, writes Phil Burge, who looks at how bearings can increase efficiency.

Factory managers are under increasing pressure to raise productivity by improving the reliability and performance of their plant What few might realise, though, is that the tools to help them do just that, are already available in the factory

Whether supplied as an integral part of all manner of rotating machinery, or stored on the shelves of the maintenance department, modern bearings - and the technology behind them - are seldom given credit for the vital role they play in today's drive towards more efficient operation.

Take just one common sight in many factories, the ubiquitous forklift truck.

These workhorses of materials handling are often exposed to varying loads under all types of environmental conditions.

And, of course, so too are all the bearings needed to smooth its multitude of operations.

For example, they have to withstand temperatures as low as -40 deg C when moving goods in and out of warehouse freezers - and then cope with the condensation that occurs with such rapidly changing temperatures.

Not to mention the shock loadings that the mast must withstand while being pushed and rammed into the pallets and bins it has to lift.

To meet such varied demands on their products, bearing manufacturers have to keep pace with their customers' expectations.

SKF, for example, can supply forklift truck manufacturers and users with hub bearing units.

These are completely integrated wheel assemblies, pre-adjusted and lubricated for life.

Originally developed for use in cars and trucks to replace traditional taper roller bearings, the hub units are ready to install and are maintenance free with a substantially reduced number of parts to worry about.

Forklift mast control can also benefit from an SKF solution.

This is a control unit that features a bearing fitted with electronic sensors to control the automatic positioning of the mast.

These sensor bearing units also find use in the electronic steering systems of industrial vehicles, where they can replace heavy, expensive mechanical and hydraulic systems.

They can detect shaft speed and acceleration, direction of rotation and angular position.

Another example of where bearing technology is adding to equipment performance can be found in the many applications of industrial fans, such as in cooling systems and heating and ventilating units.

To up the performance of these units it's often necessary to run the fan at higher speed.

But the higher the speed, the more heat is generated.

This often means changing the lubrication of the bearings from grease to a more expensive oil-based system.

SKF has addressed these heat-related problems through its self-aligning bearing system - a combination of an SKF Explorer spherical roller bearing in the locating shaft position and a CARB toroidal roller bearing in the non-locating position.

This system accommodates misalignment, with axial shaft expansion being taken up within the CARB bearing, virtually without friction.

Apart from higher speeds and extended lubrication intervals - which result directly from less heat being generated in the bearing system - the benefits of the self-aligning approach also include reduced energy consumption, extended bearing life and increased reliability.

SKF Explorer deep groove ball bearings are ideal for handling light to moderate radial and thrust loads at very high speeds with low friction, a combination equally suited to pumps as it is to fans.

With the recent trend towards running pumps with variable speed drives, however, some problems have cropped up as a result of stray electric currents generated by the inverter drive.

These eddy currents can flow through the motor shaft and pass through the bearing, damaging the raceway and rolling elements as they arc across the bearing elements.

Often difficult to spot at first, the damage can accumulate, resulting in increased bearing noise, vibration and ultimately failure.

Here again, bearing manufacturers have shown they can stay ahead of the game.

SKF, for instance, offers a wide range of insulated bearings that provide a barrier to these stray currents.

These include hybrid bearings in which the rings are made from bearing steel, but the rolling elements are machined from bearing grade silicon nitride, an electrically insulating ceramic.

Another, originally unintended, consequence of the development of these metal/ceramic hybrid bearings is that they are opening up the possibility of oil-free refrigeration compressors.

Research studies at SKF's Engineering and Research Centre have shown that refrigerants themselves can actually form a thin elasto-hydrodynamic lubricant film when subjected to the very high pressure developed between the rolling elements and raceways of bearings.

This film is too thin to lubricate all-steel bearings, but has proved more than adequate for the ceramic/steel combination of the hybrids.

In many ways, bearings may well have taken on the appearance of commodity products - ordered from the catalogues and stored on the shelves until needed - but appearances can be deceptive.

Behind the scenes, bearing manufacturers are responding to the same pressures as their customers and coming up with innovative solutions to many of industry's long-standing problems.

* About the author - Phil Burge is marketing manager with SKF (UK). Request a free brochure from SKF UK ...

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