Spherical plain bearings smooth Spanish solar generation plant 07 June 2010

More than 1,000 high precision plain bearing rod ends are enabling the efficient operation of the Andasol solar power plants in southern Spain, currently the largest parabolic trough solar power station in the world.

Dr Arndt Schweigert, head of power generation sector management at Schaeffler, explains that the Andasol 1 solar power plant, which went on line in mid-2009, uses a total of 1,248 Elges hydraulic rod ends, from Schaeffler. These support several hundred hydraulically adjustable parabolic troughs, positioning them with millimetre precision to maximise solar energy capture.

"High precision bearings are required here so that the power plant can operate at maximum efficiency," says Schweigert. "Moreover, the bearings also have to withstand loads that should not be underestimated," he adds.

In these types of projects, he says, plain bearings are optimised for the slow, precise swivel motion, which has to be smooth, without any stick-slip or jolting on start-up.

Equally, though, the hydraulic rod ends can support high forces and are also suitable for alternating loads. This means that the 150m-long collector chains on the plant can be adjusted precisely to within a tenth of a millimetre, enabling the troughs to follow the sun.

In this case, the hydraulic rod ends have been fitted with manganese phosphate-coated radial spherical plain bearings, with steel/steel sliding contact surfaces. This surface treatment improves the running-in characteristics and reduces friction.

In brief detail, Schweigert explains that the inner ring of the spherical plain bearing has a width of 70mm, a cylindrical bore diameter of 110mm, as well as a spherical outer slideway. The 160mm diameter outer ring has a cylindrical outer surface and a concave inner slideway with a diameter of 140mm.

Incidentally, Schaeffler also provided 7,488 environmentally-friendly (lead-free) plain bearing strips for the Andasol 1 plant. These strips have been mounted in the supports between the individual segments of the 150m collector chains, ensuring smooth slewing movements during sun tracking.

Brian Tinham

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