Precise bearing supports for high efficiency and long life
Irrespective of whether solar power plants are photovoltaic or use solar thermal technology, they are particularly efficient if the collectors track the course of the sun. The more precise and trouble-free they operate, the better and more profitable the plants are. Rolling and plain bearings as well as linear units from the INA, FAG and ELGES brands make a decisive contribution here, since they have high rigidity and high load carrying capacity and operate reliably even under extreme operating conditions. With its extensive range of products and specialist expertise for materials, coatings, and seals, Schaeffler is an important development partner and supplier for projects involving parabolic trough, solar tower, Dish Stirling and Fresnel power plants. Besides standard products, individual solutions for specific customer requirements are offered. Depending on the type of power plant and its individual design, suitable rolling bearing solutions can include slewing rings, angular contact roller bearings, ball screw drives, housing units and radial insert ball bearings as well as track rollers. Plain bushes, spherical plain bearings, and linear units are also used. Schaeffler will be presenting this extensive product range at the Intersolar Europe trade show in Munich on June 13 – 15, 2012 in hall C2, booth 170.
Plain bearings for single-axis tracking systems
Schaeffler has systematically expanded its range of plain bearing solutions. In addition to the plain bearings with ELGOGLIDE that have proven themselves for several years, the product range also includes metal-polymer composite plain bearings as well as plain bearings with ELGOTEX.
ELGOGLIDE stands for a sliding layer that essentially comprises a technical woven material comprising support fibers and Teflon fibers and a synthetic resin matrix. The advantages of these bearings are the total freedom from maintenance and very high load carrying capacity, especially in the case of very high loads on one side and swiveling motion.
The special characteristics of metal-polymer composite plain bearings are due to the combination of plastic and metal materials. This material compound allows low-wear sliding characteristics as well as a high load carrying capacity and thermal conductivity. The excellent material formability also enables customer-specific components to be designed for various rotary, linear and swivel motions.
The combination of materials in bearings with ELGOTEX means they are resistant to corrosive media and facilitates a constant low friction value with low wear and absolute freedom from maintenance. The material comprises two layers that are wound onto each other. The internal sliding layer, which is embedded in a resin matrix with fillers and solid lubricants, is made of synthetic and PFTE fibers. The external layer comprises continuous glass fibers (glass filament) in epoxy resin. A specific winding angle of the glass fibers stabilizes the layer, thereby significantly increasing the strength of the bush.
Angular contact roller bearings AXS for double-axis tracking systems
Rolling bearings, such as AXS angular contact roller bearings, are used, for example, in the double-axis tracking systems of solar thermal plants such as solar tower and Dish Stirling power plants. Typical applications are reflector adjustment systems. High load carrying capacity, rigidity and positioning accuracy also play a decisive role here. These features are the prerequisites for a secure and smooth bearing support without vibrations for solar collectors. The bearings must also support high forces and moments, for example during sudden gusts of wind. The bearing supports are therefore decisive for the plants’ reliability and cost-effectiveness. Angular contact roller bearings AXS can be integrated in existing and new designs. They are very easy to fit securely. The geometry of the bearing rings is identical, which means no errors can occur during fitting. Simple, turned bearing seats are sufficient for supporting the bearing rings manufactured using forming methods. In addition, special lubricants (both grease and oil can be used) mean the bearing supports have particularly low maintenance requirements.
Modular System for Automation Tasks
The Linear Technology Business Unit is a system supplier that delivers fully-equipped linear modules designed to match customer-specific requirements in addition to a wide standard range of driven, ready for use linear units, both for the manufacture of solar collectors and photovoltaic modules as well as for solar tracking itself.
The linear units (modules and tables) are based on anodized aluminum profiles and designed according to the modular principle, so they can be optimally equipped according to the specific requirements of the application. In many applications, the stable and rigid body construction eliminates the need for complicated frames. The compact design facilitates the integration and installation into handling and production facilities for solar panels.
The linear units are available as monorail guidance systems and shaft guidance systems. The drive function is carried out by a ball screw drive, toothed belt drive, or direct drive. Schaeffler also supplies the full range of accessories for power transmission applications, and delivers the driven linear units as complete systems that are ready to fit and ready for use (including the control system).
Seals and coatings are often indispensable
The prevailing environmental conditions place extremely high demands on the development and design processes of bearing supports for power plants. The environment – often desert or desert-like regions – is usually characterized by aridness, sand, high temperatures and significant temperature fluctuations. Such conditions require the use of reliable seals that prevent particles from entering the bearing and keep the high-quality bearing grease inside the bearing, as well as special materials and coatings that protect the bearing from corrosion. Schaeffler offers a modular seal system comprising a variety of sealing principles, sealing systems, sealing element arrangements and combinations. Schaeffler has been a leader in the area of innovative surface and coating technology for many years and has optimized the functionality of surfaces of rolling bearings and precision components that are subjected to high loads. Schaeffler’s Surface Technology Center performs development work on laboratory scale and reliably transfers developments to volume production processes. Zinc and zinc alloys are predominantly used for anti-corrosion protection. Under the Corrotect® name, Schaeffler has brought various coatings onto the market, such as zinc (Corrotect® ZK), zinc iron (Corrotect® ZI) or zinc nickel (Corrotect® ZN).
The sliding partner (shaft/pin) of plain and spherical plain bearings can be coated with chromium mixed oxide (LC layer) on a columnar chromium layer (Durotect® CK+) to provide anti-corrosion protection and to improve the sliding function. Combining the basic layer with a soft sliding layer in this way improves not only the running-in behavior but also the friction and wear behavior.
Durability and resistance to corrosion are often underestimated but decisive criteria for ensuring high reliability and long operating life with low maintenance requirements and high cost efficiency. Schaeffler offers durable bearing solutions with an operating life of up to 20 years.
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