DavyMarkham - News
Recycled and Remanufactured Hoist For Canada Gold Mine

Sheffield heavy engineering company, DavyMarkham has been awarded a contract for the mechanical parts of a new 16ft (4.89m) double drum hoist, for use underground at the largest gold mine in Canada. This follows a competitive tender call issued by Agnico-Eagle Mines, one of North America's leading mineral exploration companies, with more than 30 years' continuous experience of gold production, mainly through underground operations. The hoist will be deployed for shaft sinking, then production duties on the LaRonde II project, the 3300m (2 miles) deep extension to the current LaRonde operation, based around 650km northwest of Montreal.

In an order worth around £700k, the 16ft hoist is to be built incorporating reusable components, such as drum sides and disc brake frames, salvaged from a Markham double drum unit originally supplied in 1996. The complex machining and fabrication work, being carried out by the Sheffield firm's newly established Reconditioning Service, necessitates matching these existing parts precisely with newly-manufactured mechanical components, such as the drum shell plates, shaft, water-cooled gearbox and clutch operating system. Recycling and reutilising existing parts leads to significant savings over the price of a new double-drum hoist, which can cost as much as C$2 million, especially as NDT (non-destructive testing) methods are applied to verify freedom from service-induced structural defects.

Agnico-Eagle's flagship LaRonde operation, which includes underground mining, a mill complex, treatment plant and secondary crusher building, has produced more than 2.9 million ounces of gold since 1988 and currently uses the 2,250m deep Penna Shaft, the deepest single-lift shaft in the western hemisphere. The LaRonde II project involves a deeper ore reserve containing an estimated 3.6 million ounces of gold, inaccessible by the existing Penna Shaft, which requires sinking an internal shaft or 'winze' to a depth of around 2,900 metres below ground. A series of ramps will then enable mining down to approximately 3,300 metres.

The 16ft hoist will be used initially to sink the new winze, before being converted to a production-only winch carrying 17 tonne skips, and it is being manufactured by DavyMarkham to meet health & safety criteria for both duties. With a line pulling rate of 87,000lbs, it consists of two drums on a single shaft, one fixed and the other clutched, which means they can work independently, one drum being disengaged via the clutch for loading, while the other is raised to the surface for emptying. The hoist will actually be installed deep underground at a depth of 2,060m, enabling Agnico-Eagle to sink a shaft a further 810m, then ultimately mine to a depth of 3,300m below ground. For the initial duty, the total cycle time for each drum will be 125 seconds, including loading, raising and emptying, and, for the final stage, 171 seconds, the hoist typically working 10 hours per day.

The reused components of the hoist itself have an interesting engineering history that links back to Britain's coal mining industry, In 1996, DavyMarkham acquired a used hoist from Frickley Colliery in Yorkshire for Agnico-Eagle, designing and fabricating two new 16' diameter drums to fit the existing shaft, bearings and bedplates. Then in 1999, it upgraded the same unit for skip hoisting duties down to 2,250 metres in the Penna Shaft, supplying new 19' drums, a new shaft, clutch mechanism and disc brake system. Now, the original 16' drum sides and other components from the original upgrade are being used in the build up of the latest hoist, in an impressive exercise in recycling.

Having been structurally verified using advanced NDT techniques, the two existing 16' x 90' drum sides are being utilised in the rebuild, complete with newly manufactured cast steel/phosphor bronze bosses and an automatic grease lubrication system. The disc brake frames and base plates are also being reused, newly equipped with a disc brake system, supplied as part of the electrical package by ABB. Existing sprag units for preventing drum rollover during maintenance are also being reconditioned and fitted.

Since hoist components must be taken underground via a narrow ramp, all parts must fit within a 3m wide x 2.5m high x 6.5m long envelope and the existing drum shaft was considered too large and cumbersome, in addition to having the wrong type of clutch mechanism and motor mount design. Thus, DavyMarkham is supplying a new shaft, fabricated in two pieces from solid steel and joined by high tensile bolts, which will run on newly-manufactured roller bearings and pedestals, rated for a minimum service life of 200,000 hours.

A geared drive configuration will be employed for winding at rope speeds up to 11m/s and, for this application, DavyMarkham commissioned a custom water-cooled parallel shaft helical gearbox from David Brown of Huddersfield; this will be mated to twin 1600kW motors, with a nominal input speed of 750rpm. A new clutch assembly and operating system are also included.

Installation underground is expected to commence in May, with commissioning completed by the end of July 2007.