Rolling Bearing Selection

Rolling bearings are critical components in rotating plant, machines and equipment, including machine tools, automated handling systems, wind turbines, paper mills and steel processing plants. However, the decision in favour of a specific rolling bearing should always be taken after analysing the whole life costs or total cost of ownership (TCO) of the bearing and not merely on the basis of purchase price alone.

Buying cheaper bearings can often prove more expensive over the long term. Often the purchase price accounts for just 10 per cent of the overall costs. So when it comes to buying rolling bearings, what’s the point in saving a couple of pounds here and there if this means higher energy costs due to higher friction bearings? Or higher maintenance overheads resulting from a reduced service life of the machine? Or a bearing failure that results in unplanned machine downtime, leading to lost production, delayed deliveries and dissatisfied customers?

Today’s advanced high technology rolling bearings offer many improved features that enable TCO reductions to be achieved, providing added value over the complete life of rotating plant, machines and equipment.

For a bearing designed/selected for a given industrial application, the TCO is equivalent to the sum of the following:

Initial cost/purchase price + installation/commissioning costs + energy costs + operation cost + maintenance cost (routine and planned) + downtime costs + environmental costs + decommissioning/disposal costs.

Whilst the initial purchase price of an advanced bearing solution will be higher than a standard bearing, the potential savings that can be achieved in the form of reduced assembly times, improved energy efficiency (e.g. by using lower friction bearing components) and reduced maintenance costs, often more than outweigh the initial higher purchase price of the advanced bearing solution.

Adding value over life

The influence of an improved design in reducing TCO and adding value over life can be significant, as designed-in savings are often sustainable and permanent. Sustained reductions over the life of the system or equipment are worth far more to the customer in terms of savings than a reduction in the initial purchase price of the bearings.

Early design involvement

To industrial OEMs, the design of bearings can add value to their own products in many ways. By engaging with these OEMs early in the design and development stages, bearing suppliers can customise fully optimised, integrated bearings and assemblies, which meet the specific requirements of an application. Bearing suppliers can add value by, for example, creating and customising internal bearing designs that maximise load carrying capacity and stiffness or minimise friction.

In applications where design envelopes are small, the bearing design can be optimised for ease of assembly and to reduce assembly times. For example, screw threads on assembly mating surfaces can be incorporated into the bearing design. It may also be possible to incorporate components from the surrounding shaft and housing into the bearing design. Features such as these add real value to the OEM customer’s system and can potentially lead to cost savings over the whole life of the machine.

Other features can be added to the bearings that add further value over the life of the machine. These include special sealing technology within the bearing to help save space; anti-rotation features to prevent slippage under the effects of rapid changes in speed and direction of rotation; coating the surfaces of bearing components to minimise friction; and optimising bearing operation under boundary lubrication conditions.

The bearing supplier can examine closely the overall costs of machines, plants and their components – from purchase, energy consumption and maintenance all the way through to repairs, dismantling and disposal. Well-known cost drivers and hidden expenses can therefore be identified, optimised and eliminated.

by Dean Palmer

Sharing is caring!