Renewable energy systems, including solar, wind, wave and tidal power, are ideal applications for composite plain bearings.
In solar energy systems, for example, plain bearings are particularly suitable to the operating conditions, which often involve slow swiveling movements with high loads. In addition, plain bearings are also suitable for operation in media such as water (hydro power) and for dry running applications.
The Schaeffler Group has a rapidly expanding range of plain bearings for renewable energy systems. In addition to its Metal-Polymer Composite Bearings range, Schaeffler also recently launched its ELGOTEX plain bearings.
Metal-polymer composite plain bearings
Schaeffler’s metal-polymer composite bearings are particularly effective in oscillating applications, where the bearings achieve a higher basic rating life than conventional bearings. These products are available as bushes, flanged bushes and thrust washers and are ideal for applications where there are very small radial or axial design envelopes.
The metal-polymer composite material provides low-wear sliding characteristics, as well as a high load carrying capacities and high thermal conductivity. Static load carrying capacities of up to 250 N/mm2 can be achieved. Composite materials can also be used in water or other media due to its high moisture resistance.
Metal-polymer composite bearings are a cost-effective alternative for applications with minimum available space and a comparatively high sliding speed. The plain bearings are available as bushes and flanged bushes, as well as thrust washers and strips. The material can also be easily formed to specific customer requirements for rotary, linear and oscillating movements. All Schaeffler’s metal-polymer bearings are lead-free.
Three different materials are available in the range: a selection of bearings with maintenance-free and low-maintenance materials E40 and E50. The two material structures are similar: a porous bronze-sintered structure is applied to a steel or bronze backing and impregnated with a special plastic compound. The solid lubricant produces a lubricant film between the sliding surfaces, which provides low-noise operation with a constant low friction coefficient throughout the entire service life of the bearing.
E40 bearings are generally maintenance-free, i.e. lubrication is not required over the entire operating life. PTFE and different chemically inert additives are used as the lubricant. E40 is recommended for rotary and oscillating motion applications, as well as for short stroke linear movements.
Bearings with E50 are low maintenance, although initial grease lubrication is required at start-up. The sliding layer comprises mainly polyoxymethylene (POM), a high-molecular thermoplastic characterised by its low friction properties, as well as chemical and thermal stability. E50 is a low wear material that has good damping properties and long relubrication intervals. The material is ideal for rotary and oscillating movements and is also recommended for long stroke linear motion applications.
Bearings with the E60 sliding layer are maintenance-free foil bearings. These have a lattice structure in which a sliding layer of PTFE and other additives is rolled and sintered. The structure functions both as a backing and a sliding layer. The PTFE sliding layer is on both sides of the foil so that the sliding motion can take place on the inside and outside of the bushes. A further advantage is that E60 can be easily moulded.
ELGOTEX plain bearings
Schaeffler’s ELGOTEX® range of plain bushes provides a variety of technical advantages that stem from the product’s unique, entwined double-layer design.
Each bush comprises two layers of wound (twisted) material. The inner, sliding layer is made from synthetic fibres and PTFE fibres in epoxy resin, whilst the outer layer comprises continuous glass fibres (filaments) in epoxy resin. This combined, double wound material is stabilised by applying a specific winding angle to the glass fibres, which significantly increases the strength of the bush.
The result is a host of technical advantages, including extreme robustness, compactness and low wear (due to consistent friction levels). In addition, ELGOTEX® plain bushes are lighter than their bronze equivalents.
The bushes are easy to mount and require no further axial location. Due to their dry-running characteristics, the bushes are also environmentally friendly. The bushes are maintenance-free for life, resulting in reduced maintenance costs for the end user.
ELGOTEX® has already proved itself in many customer applications, including those in which high radial loads or high static loads are present. The new bushes are also insensitive to shock loads and edge pressures.
The product is available with integrated seals and is resistant to corrosive media. The bushes also perform well in applications where swivel or axial movement is required. Good vibration damping properties is a further benefit of ELGOTEX®.
INA plain bushes with ELGOTEX® are available with bore diameters from 20-200mm, outside diameters from 24-220mm, and widths of 15-250mm. Custom versions with outside diameters up to 1,200mm are also possible.