Rolling and plain bearings operate in cold temperatures

In cold environments such as ski resorts, strong winds, snow and condensation are a constant challenge for machinery. Rolling bearings and plain bearings both play important roles in ensuring that material ropeways, guide pulleys, cable cars, ski lifts, mountain railways and other critical transportation systems remain in operation at all times and require little or no maintenance.

The Schaeffler Group is working with a number of manufacturers whose equipment is required to operate in temperatures as low as -30degC and in high-altitude locations where snow and high winds are a constant threat. These manufacturers produce ski lifts, inclined elevators, detachable and fixed chairlifts, gondola ropeways, aerial tramways and funicular railways.

Most of these systems use pulley wheels, guide pulleys or rope pulleys. Each of these systems normally requires some sort of bearing to support the loads with low friction. In material ropeways, for example, design loads can be up to 40 tonnes. Line inclination is up to 45 degrees with spans of 1500m over often-difficult terrain. Aerial tramways or cable cars are used to transport either heavy goods or passengers, some of these systems catering for up to 2000 passengers per hour, depending on cabin size (from 6-200 passengers), travel speed (up to 12m/s) and system length.

Sealed ball bearings

Operators of the ski lifts or tramways want to minimise maintenance and servicing costs and will certainly not wish to replace bearings more then once during a skiing season. For ropeways, accelerators and guide pulleys, Schaeffler supplies manufacturers such as LEITNER and Doppelmayr with its single-row deep-groove ball bearings. These are provided with lip seals on both sides that are made from nitrile butadiene rubber (NBR). The bearings are suitable for moderate speeds and axial loads, but are lubricated for life using a high-quality grease.

Schaeffler's single-row deep-groove ball bearings are capable of withstanding operating temperatures from -30 up to +70degC. They are designed to deal with the accumulation of condensate and offer a longer operating life.

Spherical roller bearings

In similar applications, bearings in vertical mounting configurations are often required for ropeways and pulley wheels. For these types of applications, spherical roller bearings are the recommended choice. Schaeffler's standard spherical roller bearings with metal cages can also be used at temperatures down to -30degC.

Spherical roller bearings are double-row, self-retaining units that comprise solid outer rings with a concave raceway, solid inner rings and barrel rollers with cages. The inner rings have cylindrical or tapered bores. The symmetrical barrel rollers position themselves freely on the concave outer ring raceway. As a result, the bearings compensate for shaft flexing and any misalignment of the bearing seats. Spherical roller bearings can support axial forces in both directions as well as high radial loads. The bearings are designed for with the maximum possible number of large and extremely long barrel rollers, which means they support heavy loads. Due to the narrow osculation between the rollers and raceways, uniform stress distribution is achieved in the bearing.

Schaeffler's spherical roller bearings are also available in premium quality standard. Branded X-life, these units represent improvements in product design, product performance and service life that far exceed current standard values. As a result, under identical operating conditions, the basic dynamic load rating and basic rating life of these bearings are significantly improved. In certain applications, this means that a smaller bearing arrangement is possible.

Spherical plain bearings

In applications such as funiculars or mountain/cable railways, liquid and solid contaminants can cause vertically-mounted rolling bearings to fail prematurely. Schaeffler's GE..SW angular-contact spherical plain bearings are therefore used as a plain bearing alternative to tapered roller bearings. GE..SW bearings are complete units comprising an inner ring with a convex outer slideway and an outer ring with a concave inner slideway that has a hard chromium Elgoglide low-friction sliding contact surface. These bearings can support axial loads as well as radial loads and are therefore suitable for reciprocating dynamic loads. The bearings can also be used in pairs as preloaded units. Just as important, the bearings are maintenance-free throughout their operating life. These bearings are available for shafts from 25mm up to 200mm.

Elgoglide is a highly wear-resistant sliding layer made from PTFE fabric, which is embedded in synthetic resin and bonded to the outer or inner ring bore. This low-friction sliding material neither expands when exposed to humidity, nor heat-seals with metal. Elgoglide is also resistant to most chemical agents and is suitable for use in rotary and linear motion applications. Spherical plain bearings with Elgoglide can be classed as maintenance-free because they replace the lubrication function. Elgoglide bearings offer a number of advantages for applications requiring high load-carrying capacity and small swivel angles, such as long service life, small installation space and low friction.

For more information on Schaeffler's range of bearings for cold environments, call the UK Marketing Department on +44 (0)121 313 5870 or email [email protected].