High-performance tapered roller bearings reduce frictional torque

Paul Boughton

The new X-life FAG tapered roller bearings from Schaeffler are now available in sizes up to 635mm outside diameter (OD). This means that Schaeffler can now offer customers the widest range of high performance tapered roller bearings on the market today.

FAG tapered roller bearings in X-life quality can achieve a reduction in frictional torque of up to 50 per cent compared with conventional tapered roller bearings. The dynamic load rating (load carrying capacity) of the X-life bearing has increased by 20%, with a resulting minimum 70% improvement in the basic nominal operating life of the bearing.

As well as improving the performance and energy efficiency of the bearing, X-life tapered roller bearings also provide additional benefits in terms of a reduced design envelope, weight and friction. Design engineers can now potentially replace a standard tapered roller bearing with a smaller X-life version, therefore downsizing the system and related components. Alternatively, a standard tapered roller bearing can be replaced with an equivalent sized X-life tapered roller bearing, which will provide improved performance and energy efficiencies.

X-life tapered roller bearings also contribute significantly towards reducing operating, servicing and maintenance costs, particularly with regard to the Total Cost of Ownership (TCO).

During the development of the X-life tapered roller bearings, particular attention was paid to achieving high reliability and minimising friction, particularly in high load applications and those that require rotational accuracy. This means that manufacturers of hydraulic units or gearboxes (pinion bearing supports) such as those found in wind turbines, agricultural vehicles and construction machinery, can now surpass previous performance limits, whilst significantly improving operational safety. In terms of downsizing, the improved characteristics of the X-life bearings mean that the performance of the gearbox is improved, whilst the design envelope remains the same.

The 20% improvement in dynamic load rating and minimum 70 per cent improvement in basic rating life were achieved by improving the geometry, surface quality, materials, dimensional and running accuracies of the bearings.

The premium bearing material used in the manufacture of the X-life tapered roller bearings is specially adapted to meet the requirements of the rolling bearings and is an important factor in the increased performance of the bearings. The fine grain structure of this material provides high toughness and therefore high resistance to solid contaminants.

In addition, a logarithmic profile was developed for the bearing raceways and the outside surface of the rollers, which compensates for high stress peaks under high loads and any 'skewing' that may occur during operation. These optimised surfaces assist in the formation of an elasto-hydrodynamic lubricant film, even at very low operating speeds, which enables the bearings to withstand high loads during start-up. Furthermore, significantly improved dimensional and geometrical tolerances ensure optimum load distribution. Stress peaks are therefore avoided, which reduces material loading.

The frictional torque of the new X-life tapered roller bearings has been reduced by up to 50 per cent compared to conventional products. This is due to high dimensional and running accuracy in conjunction with improved surface topography. The revised contact geometry of the inner ring rib and roller end face also assists with the reduction of friction. As a result, bearing operating temperature has also been reduced by up to 20%.

The new X-life tapered roller bearings are not only more economical, but also result in lower bearing operating temperatures, which in turn, places significantly less strain on the lubricant. This enables maintenance intervals to be extended and results in the bearing operating at reduced noise levels.

For more information, www.schaeffler.co.uk

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