At the heart of the new system is a primary crushing installation that has increased capacity from 1000 tonnes/h to 1800 tonnes/h while reducing the average primary truck haul from 1200 m to 300 m. Set in the quarry floor, the gyratory primary is connected to the secondary plant by a series of conveyors totalling over 915 m in length, including a 715 m conveyor and one the country’s largest tripper conveyors over a 100 000 tonne surge pile. Significant improvements have also been made in the secondary plant, where capacity has been increased to 1250 tonnes/h by the installation of a 7-ft cone crusher, two triple-deck screens and a number of new conveyors. The changes continue into the wet tertiary plant, which has benefited from the addition of a third 8x20, 4-deck wash screen, plus a larger screw washer and increased pumping capacity. Last but not least, the project includes Manitoulin’s fifth onsite generator.

Plant manager Perry Newman reports that last year’s record number was fuelled by strong internal demand coupled with Manitoulin’s ability to produce a full range of products including construction aggregates as well as glass sand and metallurgical grades. The quarry’s principal markets for construction aggregates markets are Sarnia and Windsor in Ontario as well as Cleveland, Ohio and Saginaw, Michigan. Its metallurgical flux stone is in demand from customers such as the Chicago, Illinois lime plant of Carmeuse (Lafarge’s joint venture partner in the lime business), and Quebec Cartier Mining.

Dolomitic limestone from the Amabel formation is mined at Manitoulin in a single 16 m face. With over 50 years of confirmed reserves and the recent growth in demand, it was clear that a significant increase in primary crushing capacity was needed. The ageing 48x60 jaw primary was operating at full stretch, while the absence of a primary surge pile further limited its operating flexibility. Replacing the primary would not only address these issues, but also provide the opportunity to relocate the primary crushing process. Following a review of the mining plan, a new primary location was chosen near the current active quarry faces and the main body of reserves, thereby optimizing the primary haul for many years to come.

When it came to choosing the type of crushing equipment, Newman explains that portable plants were ruled out at an early stage, given the high capacity requirement and also recognising that stone from different faces is blended to maintain consistent chemical properties for metallurgical applications. A gyratory crusher was chosen in preference to an impact crusher in order to minimise fines generation at the primary stage and also avoid the expected wear costs associated with an impactor.

Before installing the new crusher, members of the Manitoulin team visited a number of other operations utilising Svedala’s 54-74 gyratory crusher, including company operations at Dundas, Alpena and Presque Isle as well as the Milton quarry of Dufferin Aggregates. Discussions with operators at these locations confirmed that two features were key to the successful operation of this widely used crusher. Firstly, the surge bin underneath the crusher should be able to accommodate any anticipated increases in haul truck size and secondly, the bin should be fitted with two feeders, rather than a single feeder, to maintain production during feeder repair or maintenance. Newman reports that the surge bin underneath Manitoulin’s primary was built with the next generation of haul truck in mind. With a gross capacity of 300 tonnes and a live capacity of about 200 tonnes, there is still sufficient remaining capacity in the hopper to receive full loads from two 96 tonne trucks after the high level alarm is triggered.

In terms of the primary installation itself, it was decided to set the primary into the quarry floor. This set up optimizes primary haul truck efficiency, unlike above ground installations where increased fuel consumption and transmission wear inevitably result from the repetitive loaded haul up a crusher ramp. The in-floor layout also ensures that all the quarry’s reserves remain accessible. Depending on the individual operation, reserves may be sterilized when an above ground crusher and access ramps are set against a quarry face. At Manitoulin, the in-floor concept has been refined by slightly raising the truck dump and turn area relative to the quarry floor, thereby helping to slow approaching trucks.

During operation, Manitoulin’s fleet of four Caterpillar 775 haul trucks – two 775D’s and two 775B’s – discharge 1220 mm minus shot rock directly into the primary where it is reduced to 203 mm minus at an average rate of 1800 tonnes/hr. Material falls into the flow onto a 1524 mm x 134.2 m conveyor, the first of a series of four 1524 mm wide Assinck conveyors that transport material to the primary surge pile. The second 715 m long permanent field conveyor discharges onto a 61 m long inclined conveyor, which in turn discharges onto a 122 m long horizontal tripper conveyor over the primary surge pile. The head pulley of the tripper conveyor is mounted on a rail-mounted car that travels the full length of the pile, while the belt wrap arrangement maintains a constant belt tension. Material is discharged on either side of the conveyor through a pant leg chute, producing a long, straight pile with about 100 000 tonnes gross and 25 000 tonnes live capacity.

Four 1000 tonnes/h Jeffrey feeders in the roof of the surge pile’s concrete reclaim tunnel discharge onto and 1524 mm x 13.7 m tunnel conveyor. This discharges onto the 1524 mm x 56.4 m inclined feed conveyor that replaces the old belt feeding the secondary plant. Here, crushing capacity has been increased by the installation of a 7-ft heavy duty Symons cone crusher, while two Simplicity 8x20 triple-deck screens have increased screening capacity. New conveyors here include an Assinck 914 mm x 55 m radial luffing stacker for stockpiling granular base product as well as a 1220 mm x 45.7 m radial conveyor to stockpile surge material.

Upgrades to the wet tertiary circuit include a shop-built 914 mm x 30 m conveyor feeding a Deister 8x20 four-deck, twin-shaft screen. In addition, fine material washing capacity has been increased by the replacement of the existing Eagle single screw washer with an Eagle 1676 mm x by 10.6 m twin screw unit producing up to 550 tonnes/ h. Pumping capacity has been increased here with the installation of Ingersoll Dresser pumps. Two high lift centrifugal split case units have tripled the water flow rate to 6,000 gpm, and to handle this increased volume, the fines pump to the twin screw and the waste water pump to the settling ponds have both been replaced.

Additional power for all this additional processing capacity is being supplied by a recently added fifth generator as well as a new substation and Motor Control Centre (MCC). Manitoulin’s relatively remote location makes mains power supply impractical, and the new 1200 kW generator, driven by a Caterpillar 3516 engine, increases the total on-site generating capacity to no less than 5.7 mW, or enough power for nearly 2000 homes.

A number of modifications were made to the gyratory during its installation, including an increase in its operating speed to 600 rpm from the 500 rpm of the Mk 1 version. In addition, its power is now provided by twin 350 hp motors instead of a single larger motor, reducing electrical demand on start up. Further improvements include a new lubrication system as well as a counterweight balance to reduce the dynamic loading resulting from its eccentric motion. At the primary installation, additional support equipment includes a Teledyne 830 series hammer and a Demag 55-tonne capacity overhead crane, while the sheeted structure itself has been extended to provide a truck repair bay.

The changes in primary production have improved the production process in a number of areas. Upstream of the primary, assistant manager Mark Wickett told Aggregates & Roadbuilding that different blasting patterns have been tried since the new primary was installed. Blast holes of 165 mm and 185 mm diameter were previously drilled on a pattern of 4.88 m x 4.88 m (burden and hole spacing, respectively) and after experiments with enlarged patterns of 5.5 m x by 5.5 m, 5.5 x 6.1 m and 6.1 m x 6.7 m, the 5.5 m x 5.5 m pattern has been found to deliver the optimum balance between good fragmentation and reduced blasting costs. Product consistency from the secondary and tertiary plants has improved as a result of improving the shape of the feed stone, from slabby 254 mm to cubical 203 mm material and the addition of the primary surge pile.

The new layout also facilitates staggered plant operating and maintenance schedules, as the surge pile holds sufficient inventory for two full shifts of the secondary plant without any primary production. Its straight design optimizes capacity and material recovery compared to the conical surge pile of a static conveyor or the kidney shaped pile produced by a radial conveyor.

The overall project was completed in a very short time frame following preliminary discussions in spring 1999. The sinking cut for the 23 m deep crusher pit and conveyor ramp was begun in August of that year and the first of some 7000 m 3 of concrete was poured a month later. Work continued throughout the winter of 1999/2000 on both the primary, secondary and tertiary improvements. At peak, 100 people were working on the job, supported by a temporary plant shop, site batch concrete plant, and 20-room site camp.

The new plant was commissioned in May 2000, with the primary producing 670 000 tonnes in its first month of operation.

Company expertise on the project included the project manager Dave Carr, construction manager Steve Marko and specialists Walter Carr, Harry Assinck and Richard Robin who were in charge of the primary crusher, conveyors and structures and electrical installations respectively. The project also provided valuable site experience for three engineers in training (EIT’s).

External resources included J.L. Richards and Associates Ltd. for engineering design and contract administration, Tera North for earthworks and conveyor footings, and concrete contractor Laamanen Construction Ltd. Castonguay of Sudbury drilled and blasted the primary pit and ramp, while Harley Electrical installed the plant’s control system. Key equipment suppliers included Rockwell Automation for conveyor pulleys and drives and Goodyear for conveyor belting.

Looking forward, Newman anticipates that the focus of investment at Manitoulin will turn to mobile equipment, with haul truck sizes increasing from the Cat 775’s current payload of 63 tonnes to the 96 tonne capacity of the Cat 777, its larger stablemate. Should the need arise in the future, Manitoulin’s primary crushing capacity can be readily increased by fitting a super spider to the 54-74, thereby enlarging its maximum opening from 1370 mm to 1524 mm.