WHEN a mining operation in South Africa found that one of its planetary gearboxes on a high-torque conveyor was failing, it called Sew-Eurodrive for a solution.
Leveraging the latest intelligent technology, the solution is a pioneering innovation providing a cost effective replacement that will ensure reliable performance. Greg Lewis, business development manager: projects for Sew-Eurodrive, says the application at the mine demanded a customised and carefully considered approach.
“The application itself was in the plant where a steel-belt transfer conveyor moves extremely slowly – with the 4 metre diameter head pulley turning just one revolution every 25 minutes,” says Lewis. “Two planetary gearboxes drive the pulley, with one on each side, and the mine had been facing the pending failure of one of these, which needed to be replaced.”
With the original installer of that gearbox unavailable, the mine came directly to Sew-Eurodrive, he explains. The drive specialist already has a good relationship with the mine, and has provided most of the power transmission items on the site.
“One of the key challenges was that the mine required only the one gearbox to be replaced at that stage,” Lewis says. “It is important to understand that in this application the two gearboxes must run together, at exactly the same speed and torque. Any variation in the speeds is not an option.”
Sew-Eurodrive was able to match one of its units very closely with the unit being replaced, but there was still a very slight difference in the ratios. This led to a 0,001 difference in the revolutions per minute.
“While this may sound insignificant, it makes a difference when the gearbox torque is a couple of hundred thousand Nm’s,” he says. “At this high torque level, any misalignment or desynchronisation can affect the foundation and potentially cause catastrophic failure.”
With the expert input of one of Sew-Eurodrive’s in-house mechatronics engineers, the solution uses the company’s MOVI-C technology in a way that has never been done before. The new planetary gearbox supplied by the company will match the torque of the original gearbox – ensuring that they turn at precisely the same speed. The solution involves removing the existing base plate and providing a new, drop-in solution with a Sew-Eurodrive planetary gearbox – designed to match the current infrastructure in the plant.
“The technology on our planetary gearbox constantly changes the torque to match the existing equipment,” he said. To prove this intelligent design, Sew-Eurodrive built a small-scale working mock-up for the customer to witness. Together with its own customised base-plate, the ‘model’ arrangement was taken to site and demonstrated to the customer’s satisfaction.
The mock-up was so successful that Sew-Eurodrive colleagues around the world asked to see it, so that they could learn from the achievement. It was also a showpiece at the company’s exhibition stand at the 2022 Electra Mining Africa event near Johannesburg.
Lewis explains that the project was designed and delivered by Sew-Eurodrive as a complete solution – from the fully customisable panels to the electronics and the installation of the gearbox. The installed unit is an XP planetary gearbox with shrink disk, with a primary X-series gearbox as a further reduction unit to achieve the required ratio.
“We engineered the steel base to fit onto the existing concrete foundation without any modifications required from the customer’s side,” he says. The significance of the project is enhanced by the considerable scale of its elements. At about 1,7 m in height – and measuring 2,1 m wide and long – the gearbox itself is sizeable, weighing about 6 t. Moving at 0,07 rpm, it moves the steel belt that carries a fine cake of raw chrome material.
“There are not many companies who can produce a solution to meet these very slow revolutions,” Lewis says. “Being among those who can is a source of great pride for us. This project has been particularly rewarding as it demonstrates our capability in matching another footprint, eliminating the need for the customer to break down existing structures and build new ones.”
The unique requirements of the project meant extensive on-site engagement with the customer and detailed measurement of plant requirements. Sew-Eurodrive’s engineers in Johannesburg generated the working drawings from which global counterparts within the group could begin manufacturing the unit in Germany.
Lewis highlights the assurance that Sew-Eurodrive can give the mine in terms of support, as the company has had a long and established presence in the sector and the country. The customer was extremely happy with this creative solution that its other plants may well be looking at similar replacements in the coming years.
“We are already assisting with our full-service technicians, and we can provide experts in electronics, mechanical engineering and mechatronics, as the need arises,” he says. “The electronics in this solution will allow the mine to implement a range of enhancements in the future, including safety features and monitoring of operations.”
