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DavyMarkham, a Sheffield heavy engineer, has won a USD20m (GBP13.7m) order to supply mining hoists and associated electrical drives and controls to Iamgold of Toronto, Canada.

The contract includes an enormous double-drum hoist with a diameter of 21ft (6.4m), a drum width of 8ft (2.4m) and a payload capacity of 44,000lbs (20,000kg).

It will serve as the main production hoist, operating at depths of 8,700ft (2,652 metres) at the Iamgold Westwood exploration programme.

DavyMarkham has recently supplied more than a dozen new hoists for gold and nickel mining projects in Canada.

DavyMarkham complies with the internationally-recognised South African SABS codes of practice for deep shaft exploration.

DavyMarkham has worked with ABB Montreal on the provision of electrical plant for these projects.

For the Westwood project, DavyMarkham will design, manufacture and supply a 21ft diameter production hoist and an 18ft (5.5m) double-drum service hoist, together with associated clutch assemblies and a multi-channel hydraulic brake-control system.

ABB has been sub-contracted to provide drive systems for both hoists, including high-voltage motors, industrial drive units, digital hoist-control systems and a hoist-operator station.

Delivery is scheduled for summer 2010 on a supply-to-mine-site basis although there may be the option of providing installation and commissioning services at a later stage.

The Iamgold Westwood exploration programme is located 2km from its existing Doyon Mine operation in north Quebec, in one of the most prolific gold production areas in Canada.

A raise-boring machine is already excavating an initial shaft and, once this is complete, the sinking of the main 5.5m diameter exploration shaft will begin.

The principal DavyMarkham components were subjected to a rigorous engineering analysis process to predict stress levels and deflections at all critical points in the hoist.

The drums were modelled using finite element studies, which accurately represent the thickness of materials to be used throughout the structure.

This process enabled DavyMarkham to recommend a smaller 18ft diameter service hoist with geared drive as the optimum size commensurate with duties, rather than the more expensive 19ft-diameter direct-drive configuration originally specified.

Both double-drum hoists are being manufactured at the DavyMarkham Sheffield works in halves, for ease of transportation and assembly on site.

The drum shells will be precisely machined on modern CNC machinery to provide parallel grooving, with two anti-synchronous crossover sections, suitable for the specified diameter of hoist rope.

The drumside assembly will be bored and face-machined for accurate location onto raised flanges on the drum shaft.

Each drum shaft will be machined from a single forging and supported by a pair of self-aligning bearings, generously rated to give an L10 life of 200,000hrs.

The drive motor for the production hoist will be an overhung rotor-type and the drum shaft will have a removable, solid flange for connection to this motor, eliminating the need for additional bearing supports.

The DavyMarkham mine-hoist design features a multi-channel hydraulic-brake control system, which ensures full SABS compliance and maximum safety under fault conditions.

This system has been specified on Iamgold hoists and will be interfaced with ABB digital hoist-control equipment so that if a fault occurs with one brake channel only one cluster of brake units will be affected and the remaining clusters will provide correct brake application and controlled deceleration.

ABB will supply a water-cooled ACS6000 series multi-drive coupled to a 6800kW AC synchronous motor for the main production hoist, with an ACS800 multi-drive and two 1205kW cast-iron induction motors for the service hoist.

It will also provide its digital hoist-control and safety supervisory system to monitor the hoist operating speed envelope and will ensure reliable and accurate control of brake systems and other hoist subsystems.

This will be linked to a Type PA1 hoist-operator control station and Hoistlogger monitoring system, for an intuitive, simple and clear means of mine-hoist operation when full production starts in 2012.

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