Revolvo’s SRB Bearings Operate Under Water
Operating under water, in an abrasive solution, and at ambient temperatures up to 400C, Revolvo’s SRB split roller bearings are providing a reliable solution to the problem of support for the twin 11-metre long Archimedes ascender screws that deliver water to the massive Zambezi Rapid Water ride in the Gold Reef City theme park, Johannesburg, RSA.
The lower SRB bearings on the ascender screws have been installed to replace plain bearings that were inefficient under operating conditions of complete submersion in an abrasive sand and silt solution: this is the result of the constant churning action of the screw in the water. In contrast, the upper SRB bearings operate in dry conditions, but have to accommodate hefty 16-tonnes of axial load.
The twin problems of difficult operating conditions and high thrust loads are the result of the rides challenging application and the sheer size of the screw conveyors, which rely on the SRB bearings for location. The ascender screws are 11m long and 2.7m diameter; they are angled at 30 degrees and rotate at 27.5 rpm. Together, they are capable of supplying 7 cubic meters of water per second or 25,200 tonnes per hour.
The lower bearings on the ascender shafts are 200mm units from SRB’s Light Series range. These bearings are equipped with a special sealing arrangement that allows them to operate completely submerged, excluding water and other contaminants from the bearing enclosure. This is achieved via an arrangement of two lip seals with garter springs, and centralised positive grease feed. The positive action of the grease purge between the two seals combined with the efficiency of the sealing arrangement delivers consistent reliable long- term operation.
The upper bearings on the ascender screws are 250mm diameter SRB Medium Series units, designed to accommodate large axial loads. The bearing load is carried between the inner race shoulder on one side and the outer race lip on the other. Both shoulders and lips are specially designed to facilitate the generation of an oil film between the sliding surfaces of roller ends and lips, thereby reducing wear and limiting heat generation.
“This application demonstrates how SRB can design and manufacture units to accept conditions completely outside of the normal perceived split bearing capabilities,” said SRB Sales & Marketing Director Adrian Menzies. “Our SRB split roller bearings perform exceptionally well in harsh operating conditions even with shaft misalignment, whereas solid mounted roller bearings can suffer from non-concentric ineffective seals that will rapidly lead to expensive premature bearing failure. Moreover the number of standard sealing solutions with SRB is far greater, which extends the range of applications for our bearings.”
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