Cell-house Davey Hoist Beams Wear Investigation - Manganese Metal Company

The Cell-house Davey Hoist Beams at Managanese Metal Company experienced high wear, causing a need for the beams to be replaced on a 10 year cycle because the Hoist support flanges (the bottom flanges of the I-beams) wear so thin that it causes a safety risk. The present beams were already 12 years in service, making an immediate replacement advisable.

Although the prevailing environment is also corrosive, as is evident from photos taken in the near vicinity, an inspection of the beams themselves did not reveal corrosion that will cause beam replacement on such a regular basis. If the wear problem is addressed such that the beams need not be replaced so regularly based on the safety risk caused by wear, the beams will probably last at least 30 years before corrosion will lead to a need for replacement.

The main motivation for the project was that the production in the cell-house is affected negatively while the beams are being replaced. If the wear problem can thus be addressed adequately, the production loss suffered during beam replacement can be eliminated for at least two cycles.

The plant is fitted with two crawl beams, one on the East side (44 m long), and one on the West side (40 m long) of the knock-off area. Each of these beams is fitted with two Crawl Hoists, linked together to form the Davey Crawl Hoist for that location.

We investigated the options of surface modification (Tribological Solutions), Wear Strips, and Lubrication. We concluded that Wear Strip option is the best one, welded to the steel beam, with Borox 400 our first choice of material, with Creusabro 8000 not far behind. We suggested that the crawl beam lengths be supplied to Borox in Edenvale, there to be pre-fitted with 60x10mm Borox 400 wear strips, and then transported to site for fitting. The benefit of this was that they will guarantee the correctness of the fitting (pre-heating and welding) process.

This solution will then, according to Borox, give a service life of 6 to 8 times that of the same thickness mild steel. Added to this, even after the wear strips wearing away, you still have the full thickness of the mild steel beam, which would give another 10 years of service life (presently, the mild steel beams can only wear about half of its 17,7 mm nominal thickness before needing replacement). So, the mild steel beams fitted with Borox will easily live to very high lives, possibly 50 years or longer (although we only set or sight on a practical 30 years).