Engineering components company BMG is working closely with KwaZulu-Natal’s sugar mill engineers in the industry’s off-crop period to refurbish and replace worn components in preparation for high productivity in the upcoming season.

Original-equipment manufacturer (OEM) Dorstener brand gearboxes have been used on diffuser drives, mill drives and feeder tables for many years and three of these planet carriers recently needed to be replaced, owing to excessive bearing journal wear and cracking.

“In spite of tight time restrictions before the seasonal start-up of the mill, coupled with manufacturing challenges, BMG has designed, fabricated and installed new carriers, reducing the normal 24-week delivery period to only four weeks, with cost savings of about 7.5 times that of the OEM,” explains BMG engineering GM Mike Cooper.

He explains that carriers are normally manufactured by Dorstener from cast iron, which is extremely difficult to repair.

Cooper says in this case, there was the additional problem of bores positioned close together, with virtually no wall thickness between the bearing journals, which was where the cracking occurred.

“Because of the harsh operating conditions of the mill and the high torque load of these units, we decided replacement was the preferred option over refurbishment,” he says.

These planet carriers were reengineered and fabricated out of 355 WA steel plate, which is not only stronger than the original cast iron units, but also allowed BMG to manufacture these carriers in a far shorter lead time than usual – three weeks.

The team was on a tight deadline to have drawings and designs approved to ensure highly accurate dimensions for a perfect fit with clearances to accommodate the gear mesh.

Welding challenges to maintain the structural rigidity of the system were overcome by machining interlocking tabs in the top and bottom main plates as well as in the webs and side rings, to ensure a more precise assembly for welding, with less distortion.

The webs and side plates were welded to the bottom ring and the entire assembly was then fitted fit onto the top ring, for welding into place. Slots were later filled with weld, so that the webs formed an integral part of the structure.

BMG’s specialist services to KwaZulu-Natal’s sugar sector include bearing and gearbox inspection, bearing and chain refurbishment, large size bearing assembly and alignment and balancing as well as customised product design.

The company’s mobile field services team conducts breakdown and routine maintenance on plant and carries out troubleshooting to ensure the highest level of plant output and reliability.

BMG’s total plant maintenance solutions service is geared to optimise productivity and enhance process plant operating reliability to make a difference to the efficiencies of every plant.