Nordic Minesteel Technologies, a North Bay manufacturer of haulage, loading and shaft solutions, has won contracts to supply compensating sheaves for two Blair Multi Rope hoist installations – one for Glencore’s Onaping Depth project in Sudbury an another for Kirkland Lake Gold.
Blair Multi Rope hoists are becoming more popular in Canada because they allow mining companies to use steel instead of wood guides and still offer protection in the event that one of the two ropes fails. Compensating sheaves are necessary to maintain the same tension in each rope and keep the conveyance level.
“Because the two ropes will tend to stretch at different rates over time, and because of potential for eccentric (uneven) loading in the conveyance, something must be done to ensure the conveyance will remain level during hoisting,” explained Jim Brownlee, Nordic Minesteel’s product manager for shaft equipment. “This is done by maintaining the tension equally on both ropes. Our sheaves compensate for this hydraulically by maintaining a common pressure between the two supporting cylinders. The system includes features that adjust the sheave levels and also interlock with the hoist controls.”
Wood guides, which are much more common in Canada, work with spring loaded dogs that dig into the wood to arrest a falling conveyance if a rope breaks.
“The problem is that wooden guides deteriorate from water and wear, and need to be continually adjusted and realigned,” said Brownlee. “It’s ongoing, intensive maintenance and can get expensive. By using the Blair hoisting system, there is a redundant rope in the event of a failure.
“Because of this redundancy, the Ministry of Labour is satisfied that personnel are protected. The elimination of the safety mechanism means that the wood guides can be replaced with steel guides, which minimize maintenance and will last the life of a mine. Long term, this is a great savings for the mine.”
To date, said Brownlee, there are only three Blair Multi Rope hoists in Canada. The first one was installed at Cigar Lake in Saskatchewan, the second one at Glencore’s Nickel Rim South Mine in Sudbury and the most recent one at Goldcorp’s Hoyle Pond Mine in Timmins.
“The single drum hoist has a divider in the middle, and they run two ropes on it instead of one. The two ropes go up into the headframe, over our sheaves and then go down to the skip or cage,” said Brownlee.
“There are two sheaves side by side. They’re each mounted in carriages and they’re supported by large hydraulic cylinders. The cylinders are linked to a common manifold so the pressure between the two cylinders is always the same.
One sheave may rise and one may lower, so there’s always the same tension in the ropes. Now, the conveyance will stay level all the time.”
Nordic Minesteel has made several improvements to the compensating sheave designs in the past.
“We’ve made improvements in the way the bearings mount and we’ve made changes to reduce the friction in the system,” said Brownlee, a mechanical engineer who has worked on mine shaft equipment for over 25 years.
Nordic Minesteel manufactures the compensating sheaves at its plant in North Bay and works with North Bay’s Feldcamp Equipment for the hydraulic components.
Mines using wood guides are difficult to retrofit with Blair Multi Rope hoists, compensating sheaves and steel guides because of the cost, but more and more mines are specifying them for new shafts, said Brownlee, “because with a greenfield installation, you can do what you want.”