Pressure. It can be both good and bad, sometimes simultaneously. Tim Rorison and Keith Punkari know this firsthand. In 2018, Tim, an Electrical supervisor/scheduler at Garson and a 32-year Vale employee, noticed the skip hoist motors and specifically the brush rigging (160 carbon brushes and holders) was wearing quickly and creating dust inside the motor assembly.
“The brush rigging didn’t have equal pressure across them,” Tim explained. “We were constantly replacing the brushes across all three motors. On a weekly basis, up to about four brushes were being replaced.”
As it turned out, the unequal pressure wasn’t just a brush problem. It was also a motor problem, which became a labour problem, which became a production problem, and because the purpose of a skip hoist is to transport ore to surface, it became a profit problem.
“The residual dust was causing resistance breakdowns, and we knew that this ongoing problem was affecting the motor itself and production,” Tim said.
Bring in the experts
It was time to bring in some experts. Keith, a senior hoist specialist and 20-year Vale employee who works in All Mines, and some employees from Divisional (Div) Shops, met with Tim to discuss options. Div Shops rebuilds motors, amongst other things, and they suggested reaching out to a U.S.-based company that manufactures a new type of brush rigging.
A company rep made a visit to site and recommended $20,000 custom-made brushes that would ensure equal pressure. The rep estimated a lifespan of about one year of service from regular use – a big difference from the weekly replacements that Tim and his team were undertaking. It was decided that a new brush rigging would be trialed with one skip hoist motor, and performance would be closely monitored to determine potential for the other motors at Garson (one other skip hoist and one cage).
The result? According to Tim, “It was fantastic. The new brushes have actually lasted three years (three times what the rep estimated). Also, dust was virtually eliminated, maintenance and time between brush changes has been significantly reduced and it’s safer than ever.”
Inspections require climbing a ladder to get to the underside of the motor in the pit, and before the new brushes were installed, the team was doing that climb on a weekly basis. Keith said regular visual inspections can now be done from the floor; getting into the pit is only needed for hands-on repairs. Another benefit: “We used to have to grab onto the wire brush shunts to check freedom of movement and adjust spring pressures. But the new brush boxes have a constant pressure system so there is no need to adjust the springs now.”
It was better than anyone could have hoped for. And so, in 2019, the second skip hoist motor brush rigging was replaced. Then came the cage motor brushes, and only this year were the first new set of brushes replaced on the first skip motor that was trialed back in 2018.
Bill Bailey, who Tim reports to and is the Electrical and Mobile superintendent at Garson and 20-year Vale employee, said: “The brush holder revision has resulted in an 1,100 per cent performance improvement. We went from a brush lasting approximately 40,000 tonnes (three months) to now lasting more than 500,000 tonnes (three years).
“Between Tim and the Electrical team and Keith and Div Shops,” he added, “there is no shortage of innovation here!”3