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Better bearings drive improved efficiency

Supplier: NSK Australia
05 June, 2012

In the quest for energy efficiency, friction is the enemy. Bearings provide an answer for overcoming friction and they are found at the heart of pretty much any moving apparatus.

Replacing worn bearings in existing equipment is vital, but the development of more efficient bearings is a priority.

NSK's constant bearing improvement program was designed to help equipment manufacturers meet energy targets.

The program, a synergy of materials, design, lubrication and sealing technology, has achieved a 30 per cent improvement in efficiency for the company's standard deep groove ball bearings, and an even larger 47 per cent saving for domestic appliance bearings; both compared to conventional ball, bearings of the same size. These savings are helping to reduce energy use in high consumption equipment like electric motors, air conditioners and domestic appliances.

"Bearings are components that make a big contribution towards energy efficiency," Kevin Delehanty, senior applications engineer at NSK said.

"We, as a bearings company, have an opportunity to drive up efficiency levels, reduce torque and reduce friction. This is the main driver of our improvement program."

"There are a few different things we can address to achieve greater efficiency.

"There's the relative motion of the ball bearing on the raceway — which generates friction; there's the lubrication, grease, oil — which has an effect on the torque and the efficiency; then there's the materials — the steel of the bearings and the cage.

"Optimising these three areas will increase efficiency. There are benefits for the consumer in terms of less energy used and lower energy bills, but also the appliances will have longer lifetimes. Downtime is reduced, meantime between failures is increased and you can lengthen maintenance intervals."

But there are certain limits to design. The basic ball bearing hasn't changed in a hundred years, although small tweaks to the surface finish of the raceway have been achieved and improved accuracy has resulted from better machining practices, improvements in the materials have also had an impact. Steel cleanliness has improved enormously over the last 20 to 30 years.

NSK has improved the steel-making process and operating conditions to reduce impurities substantially, thereby achieving a decrease in oxides. The resulting long-life Z steel is now the standard material for the company's bearings.

Bearings manufactured from Z steel have a significantly extended service life when compared to conventional vacuum degassed steel: up to 1.8 times longer. In addition, Z steel also benefits from more uniform response to heat treatment, a process that ensures good hardness and excellent wear resistance.

And then there is the important question of lubrication.

"Grease formulation and developement is an on-going process," Delehanty said.

"New, better greases come on the market all the time. We develop our own, so improvement is step-by step but we don't really anticipate any great leaps forward."

When it comes to producing better bearings for domestic goods, however, there are certain limitations in terms of design.

"High capacity bearings for white goods have to fit into the same envelope as the existing bearings but have a higher capacity.

"We can put larger and more balls into the bearing giving longer lifetime and higher reliability.

"You can also downsize the equipment. If you are using say, a standard 20mm bore inside diamter ball bearing at the moment, in the same application you could potentially put a 15mm high-capacity bearing with the same load rating and the same lifetime, but you've reduced the size, so you can design your equipment to be more compact which what everybody wants to do."