Muckling and hauling a continuous process

* a small-scale tunnel boring machine is being constructed specifically for mining applications;

* three types of continuous mucking machines are competing in the Canadian market;

* an electric trolley truck has been introduced into two Canadian mines;

* a semi-mobile crusher has been commissioned in at least two mines; and

* continuous conveyor belt systems can now be used in drifts which turn corners.

Ten years ago, variations on this technology could only be found in underground softrock mines where thousands of tonnes of material are handled every day. In order to remain competitive while metals prices were low, many mining companies concentrated their efforts on reducing the cost per tonne of material handled. In many cases that meant using bulk mining methods that produce several thousand tonnes of broken muck per day. Devising inexpensive ways to move that muck to surface has been the driving force behind the development of hardrock continuous mining equipment.

At Brunswick Mining & Smelting, for example, the cost per tonne of ore hauled by loader/truck combinations is more economical than load-haul- dump haulage to an ore pass when haulage distances exceed 150 to 250 m. With an increasing amount of ore coming from stopes on the 1000 level, situated 450 to 500 m from an orepass, the company decided to investigate various loader/truck combinations. This year about 4,100 tonnes per day will come from this one level. After an exhaustive study of two continuous loaders available, the company concluded that the AL60 loader manufactured by Voest-Alpine was considered to be potentially more applicable at Brunswick than the CL450 manufactured by Continuous Mining Systems of Sudbury, On t.

The qualitative factors in favor of the AL60, according to Brunswick, included: muckpile accessibility, operator location, unit ruggedness, component accessibility, component wearability and oversize handling. Major disadvantages included loading flexibility, drawpoint mobility and stope-to-stope movement. The AL60 is crawler-mounted and hydraulically operated, with prime power supplied by a 160-kw electric motor and trailing cable. The 2-cu-m bucket is pushed into the muckpile and is then rotated so that the muck is dumped on to an apron feeder which feeds the muck on to a belt conveyor. The conveyor discharges into a truck.

Voest-Alpine also manufactures a continuous loader that is smaller than the AL60. Called the AL30, the smaller unit is designed to work in headings with cross-sectional areas of 9 to 20 sq m. The unit is wheel- mounted, articulated and self-propelled by a 37-kw motor.

Another innovation in muck haulage has been the introduction of two high-speed, 50-tonne capacity electric trolley trucks at two Canadian mines earlier this year. The Kiruna Electric Systems were introduced in Sweden in June, 1984. The system can economically haul ore up a ramp 500 m deep compared to about half that for diesel truck haulage. The truck runs on an overhead trolley system but also has the capability of running for short distances on a nickel-cadmium battery pack that recharges once the truck is reconnected to the trolley system.

One installation, at the Kidd Creek mine in Timmins, Ont., is a 1,280-m haulage distance up a 10% ramp from the 4600 level to the 4400 level. Although the truck is capable of speeds up to 30 km per hr, the system is being operated at about 18 to 20 km per hour, says Brock Morrison, product specialist for Atlas Copco.

The other Canadian installation is at the Hope Brook mine, in southwestern Newfoundland. This system is designed to haul ore from the 5015 level a distance of 1,100 m up a 12% grade, then a further 390 m to the crusher on surface.

The increased availability of broken ore at a single drawpoint in mines of Inco Ltd. in the Sudbury Basin has focused attention on more efficient materials-handling systems there. The widespread use of Vertical Retreat Mining methods in the company’s Ontario division has created the potential for producing a lot of muck at each drawpoint. The amount of muck involved is beyond the handling capability of conventional mucking systems. Inco has therefore focused much of its attention on developing new, more efficient ways to handle this ore.

The first continuous ore-handling system was introduced on the 2430 level at the Copper Cliff South mine in 1987. It consists of a CMS CL-1000 Osciloader, a CMS/Eagle 3640 low- profile crusher and a DME extendable conveyor system with a mobile 90 degrees belt bender. The system is capable of handling more than 1,000 tonnes of ore per working shift, says P. W. Golde of Inco’s Mine Research. The average 8-cu-yd LHD, by comparison, will haul about 100 tonnes per hour.

Six CL-1000s have been operated in Inco mines since 1984. Powered by a 200-HP electric motor, the unit has an adjustable frequency oscillating lip that acts in a similar way to the digging action of an LHD. This oscillating lip lifts the muckpile, allowing ore to drop on to a belt conveyor constructed of Kevlar. The conveyor is supported by polyethylene wear bars and standard conveyor idlers.

To minimize the distance to an underground crusher, Inco has elected to use a low-profile crusher called the Eagle crusher. This unit is a 36×40- inch jaw crusher powered by a 150-HP motor which has a patented inclined crusher chamber that significantly reduces the feed height. This allows it to b e used in an underground opening with a normal back height of 14 to 16 ft. The unit is mounted on D-7 size Caterpillar crawlers and is fitted with a vibratory feeder and a discharge conveyor. Four outrigger jacks lift the unit off the ground to minimize vibration while operating. The unit reduces muck to –8 inches at a rate of 200 to 300 tonnes per hour.

The ore is moved from the crusher by a 36-inch wide conveyor system, designed by DM Enterprises of Saskatoon, Sask. A series of portable, telescopic, floor-mounted conveyors on stands allows the osciloader/crusher system to advance into the muckpile over a distance of about 10 to 30 ft.

A Belt Bender, also manufactured by DM Enterprises, turns a continuously running conveyor belt horizontally through 90 degrees . The unit is powered by a 75-HP motor and is capable of feeding out or retracting 400 ft of conveyor.

It is hoped that the continuous mining system will increase, by up to 100%, daily production from the 2430 level of the Copper Cliff South mine.

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