The reconditioning of scraper idlers on a submerged scraper conveyor (SCC) has increased the average mean time between failures (MTBF) from between three months and six months to between 12 months and 18 months.  

SKF asserts that this increase in MTBF was achieved with the use of the company’s sealed bearings, combined with upgraded internal modifications and locally manufactured custom seals.

The submerged scraper idlers convey water-quenched, hot coarse ash to the front of the SSC which then collects and dewaters the boiler bottom ash before discharging it at a controlled rate onto downstream plant. The SSC’s water-filled top trough, which works in conjunction with the dipper plates, provides boiler sealing by preventing air ingress into the boiler via the SSC.

The cost of frequent plant downtime to replace the failed scraper idlers was further exacerbated by the regular purchase of new units. SKF proposed the supply of sealed spherical roller bearings, a quality reconditioning procedure on the scraper idlers and an overall redesign of the internal sealing arrangement. SKF senior application engineer Cody Petersen explains that the highly contaminated operating conditions called for the use of sealed bearings, which help eliminate contaminant ingress, and increase overall bearing life expectancy, equipment availability and application running time.

The SKF team carried out a redesign of the entire internal geometry, shaft, hub and guide wheel. “We also manufactured custom seal cartridges to house custom seals manufactured by SKF locally and we partnered with an accredited SKF supplier to recondition the housings,” added Petersen.