Brevini engineered gearbox keeps rock salt moving 10 June 2013

A challenging drive and gearbox re-engineering and replacement project has recently been completed by Brevini Power Transmissions at an unnamed mine in Cheshire on-time, and on budget.

With the original hoist equipment, driven by a helical gearbox, installed in 1973, concerns had been raised over the reliability and safety of this plant. But when the the main contractor approached Brevini to advise on the project, initial site investigations revealed a complex engineering problem.

The original hoist lifted a nine tonne skip over 155 meters in just over one minute, but the operator wanted to improve capacity, as well as gaining in terms of efficiency and reliability.

The new motor power was specified at 780kW, with an operating speed of 590rpm and output of 21rpm. The duty cycle would see the skip accelerate for 10 seconds, travel at constant speed for 25 seconds before decelerating for 10 seconds and unloading. This had to be repeated 24 hours per day, six days per week.

Brevini designed the new gearbox, while the main contractor planned how to facilitate the exchange. The new drive had to be designed to fit into the footprint of the original helical gearbox and not interfere with the existing machinery. This included the original tacho drive system, which provides real-time data on the position and speed of travel of the hoist.

The layout of the original drive train included the gearbox and coupling, as well as a long driveshaft, which would have to be cut and then machined to match the new drive coupling, supplied by Brevini.

Engineers at Brevini based the gearbox on one of the largest models of the PIV Posired 2 range, the PD85 gearbox, which was modified to ensure that it fitted in to the space available.

The output shaft of the PD85, measuring 370mm, was designed for a shrink fit to the drive coupling, which was also supplied by Brevini. The final connection to the driveshaft of the hoist would require on site machining before the whole installation could be commissioned.

"We delivered a bespoke solution to meet the exacting requirements of the client by using our expertise in the field of heavy duty drive applications," comments Dave Brown, sales manager for Brevini UK.

"More and more of our retrofit work for similar applications is being won on the basis that we will provide a customer-specific solution, rather than something off the shelf, but without the downsides of cost and long lead times."

Brian Tinham

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Brevini UK Ltd

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