Headgear sheave wheel manufacturer Kew Foundries has been awarded the contract to replace existing deflection sheave wheels on mineral resources miner Rio Tinto’s Palabora mine, in Phalaborwa, in Limpopo province.
The contract heralds the manufacture of Kew Foundries’ first-ever six-sheave wheel cluster set.
The project involves the supply of two-sheave wheel cluster sets, comprising four wheels each, to be used on the mine’s production hoist and a six-wheel cluster set for use on the mine’s service hoist. The new sheave wheels will each have a tread diameter of 6,152 m and an outside dia- meter of 6,345 m.
“We were approached by Rio Tinto Palabora mine management to replace the existing sheave wheel deflection clusters, as the current deflection clusters require excessive maintenance resulting in increased down time,” says Kew Foundries technical director Jaime Goncalves.
The sheave wheels that are currently in use were imported and feature a welded assembly. The welded assembly has become problematic as the welds develop stress cracks during normal operation.
To perform repairs, a technician needs to climb up into the headgear, inspect and reweld the sheave wheel assembly welds. This has resulted in unacceptable amounts of down time for the business unit.
Kew Foundries has designed a solu- tion which features an 80% cast iron construction. The hubs and rims will be cast in grey cast iron, while steel will be used to manufacture the spokes of the wheel. Kew Foundries’ design does not incorporate any welds into its assembly. Rather, all mating parts will be assembled using a bolted construction method. This eliminates the possibility of stress cracks developing, and results in a superior product which will help to ensure that the mine does not experience any unplanned down time resulting from sheave assembly maintenance.
Kew Foundries’ design also differs from the current solution in that an external bearing assembly has been incorporated, as opposed to the current internal bearing design.
“The current sheave wheels feature an internal bearing assembly. This solution is acceptable while the bearings are function- ing properly. However, once a bearing fails, the entire cluster assembly needs to be stripped to repair a single bearing. The mine has reported excessive down time as a result of a failed bearing. Our design features sheave wheels mounted on phosphor bronze bushes and external bearing assemblies. In the event of a bearing failure, the bearing can be accessed directly. “However, as long as the bushes are greased and the bearing inspected annually, this design will negate any down time,” Goncalves explains.
Kew Foundries provides total cast solutions for its clients. The company’s technical team has more than 100 years combined experience in designing cost- effective winding solutions either independently or working together with clients to achieve solutions that meet the requirements of the mining industry under the most demanding conditions.