Inco’s Crean Hill mine is using the latest in mining technology minus the diesel equipment. It could become Canada’s safest, most efficient operation when it resumes full production in 1989. By Patrick Whiteway The mine is 82 years old, but Inco Ltd. sees it as the first of a new generation. Any new mines in the Sudbury Basin, the company says, will be built on this model. Compared to Inco’s other Sudbury mines, the 3,000-ton-per-day Crean Hill mine, on the southwest rim of the basin, will produce only a small percentage of the 55,000 tons of copper-nickel ore Inco’s Ontario division produces each day. But Crean Hill will stand out from all the other operating mines in Canada for two reasons.
First and foremost, the miners will have a cleaner, quieter working environment, according to Choon Park, area superintendent of technical services. This is because all the equipment that’s now on order will be electrically driven. While the initial costs of the equipment will be high, it should nevertheless prove to be more efficient.
Secondly, mining costs should be low because of the numerous pieces of technology which Inco has decided to bring together to mine the lower portion of the orebody at Crean Hill. In fact Park is certain that the mine will be the lowest-cost copper-nickel producer in Inco’s Ontario division.
Since all equipment will be driven by electric motors, the mine should save considerable capital in ventilation costs, says mine superintendent Robert Russel. This will be accomplished in two ways. First, there will be no soot or diesel exhaust gasses in the mine air; and secondly, there will be less heat generated by the equipment. In a typical deep mine, air must be cooled to make working conditions tolerable. According to Ontario’s Mining Act, 100 cu ft of air per minute must be supplied to a workplace for every unit of horsepower operating in that workplace. Since dust will be the only contaminent in the air to be diluted, ventilation requirements at Crean Hill are expected to be much lower than those of most mines.
The decision to switch to all-electric equipment was made solely by the company. The United Steelworkers of America, the union that represents all of Inco’s non-salaried workers in Sudbury, has yet to comment on the plans.
Discovered at the turn of the century, Crean Hill was originally mined by open pit, sublevel caving and shrinkage mining methods on the upper levels. The orebody has, at the very least, 9-10 years of proven ore reserves remaining below the 1,800-ft level. And it is still open along strike and at depth, Russel says. Grades are generally higher than the Ontario division average.
Today about 60 men are on the site doing pre-production development work (ventilation raises, crosscuts and draw points). Some 300 tons of development rock and ore will be hoisted daily by August and some 600 tons per day by late 1987.
The mine hoist has already been converted to 60-cycle power and there are plans to replace the existing 8-ton skip with a new, light-weight, 10-ton unit for more efficient hoisting.
“Crean Hill is ideal for bringing together all the innovations we’ve developed at other mines over the past six years,” Park says. But, at the ripe age of 82, this is no virgin mining situation (most of Inco’s mines aren’t). So, again, engineers will be faced with the delicate balancing act of using the new with the old.
For example, in the early 1970s seven development drifts on 250-ft intervals from the 1,800-ft to the 3,900-ft level were driven parallel to the strike of the orebody. Also, a huge new crushing facility, complete with a 48×66-inch Traylor jaw crusher with a 300-hp motor, was excavated on the 3,900-ft level in 1976. The development drifts’ design, however, make it impractical to use conveyor belts to carry ore from drawpoints to the orepass. The only conveyor belt to be used will be on the 4,000-ft level (below the crusher) which will take the crushed ore to the loading pockets below the level. The conveyor belt is 42 inches wide, 1,475 ft long and has a rated capacity of 300 tons per hour.
Continuous mucking machines for loading 70-ton manless electric trolley trucks (now being developed at Inco’s Murray Shop) may be used on the production levels in the future. For the time being, however, the company has decided to use the more flexible electric 8-cu-yd scoops manufactured by Wagner Mining Equipment of Portland, Ore. These 149.2 kw units run on 3-phase, 50-cycle, 660/1000 vac power. Five of the scoops are on order from Blackwood Hodge, in Sudbury, and the first should arrive at the mine site in May. The distance from the orebody to the ore passes varies from 350 ft.
Mining of the orebody, which averages 150 ft long and 100 ft wide, will be done strictly by vertical retreat mining (vrm). Starting from the bottom level and working their way up, operators will be able to use the fill floor of one stope as the draw point for the stope above. This, of course, will cut down on the amount of development work that has to be done for each stope and will eliminate the need for crown pillars between levels. Experience at Inco has shown that the optimum distance for accurate drilling of 6 1/2-in blastholes is about 250 ft — the distance now separating the lower production levels at Crean Hill.
Production blast-hole drilling will be done by two CD-360 electric- hydraulic in-the-hole drills, which are capable of drilling both upholes and downholes. This means the drills may be able to drill off the stope above while the one below is being blasted — without having to move to the next level. But, as it stands, upholes can be drilled accurately over distances of only 100 ft, so plans are to drill only downholes.
Once a stope is mined out, high- density cemented sand-fill will be used to support the walls so that ore between the primary stopes can be extracted. Dry sand will be transported underground and combined with water and cement at a ratio of about 30:1 at the workplace just prior to going into the mined-out stope. This novel technique should mean that no water will come from the filled stope. That will reduce the problem of leachable calcium from the cement getting into the ore, which is suspected of reducing nickel recoveries in the milling stage.
The existing ore-handling system is old. Installed in 1976, two years before the mine closed, the crusher station on the 4,000-ft level is one of the biggest in Inco’s Ontario division. The Crean Hill operators plan to fit the crusher, feeders and skip-loading pocket with a sophisticated monitoring system. This system, consisting of video monitors and programmable logic controllers, should minimize the number of operators responsible for the ore-handling. One man will be required. The system will include vibration, lubrication, temperature and pressure sensors on the crusher itself. It will also include tv monitors showing the area as viewed by cameras positioned on the skip loading pocket and the feeder chutes on both the ore and waste pass.
Surface facilities will also be highly automated. All engineering drafting and record-keeping will be done on Hewlett Packard computers using a standard computer-aided design package developed in-house by Inco’s engineering department. Maintenance will also be handled by an ibm-pc-based system called automaint, a software package written and marketed by Maymarg Computer Services of Pittsburg, Pa. Underground surveying will be handled by just one man, Denis Delaire, using laser surveying equipment.
The total workforce needed to produce 3,000 tons of ore per day is expected to be only 119. In the past up to 3,800 tons of ore have been pushed through the crusher, so productivity may be even higher than this target indicates. By 1989 the typical miner at Crean Hill is expected to have anywhere from 13 to 30 years of experience with the company.
GEOGRAPHICAL LOCATION: Crean Hill
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