Grand Valley rings in major equipment changes

Grand Valley Aggregates 2000 Ltd. has been busy meeting demand from the strong Toronto construction market, and this demand has highlighted the need for increases in both capacity and operating efficiency. This year the company added two new crushers and two new screens to its portable aggregate spread, complementing changes to a primary haul fleet that now comprises just two units compared to the previous five-piece set up.

The portable spread is currently located in the main pit operation some 70 km north west of Toronto. A Cedarapids 30x54 jaw crusher has replaced a smaller track-mounted unit in the primary position, while a Cedarapids 380 MVP Rollercone has replaced a horizontal impact crusher on secondary crushing duty. Two screens, Cedarapids 6x16 and 7x20 triple deck units, round out the new spread. Owner Mike Crupi explains the background to these changes: "Each change has a specific objective. The changes made to the primary haul fleet last year were cost driven, and have delivered significant savings while maintaining the required plant feed rate. This year, the addition of the 30x55 primary jaw, with a larger feeder apron and grizzly screen than its predecessor, has improved the separation of moist feed material. The switch to cone crusher in the secondary position targeted maintenance costs as the Rollercone is expected to deliver significantly improved wear life over the impactor."

The 10 m thick floodplain deposit at Grand Valley is worked underwater and has similar properties to the underlying limestone bedrock. It contains about 70% coarse material (larger than 4.5 mm), with most of the coarse fraction sized at between 200 mm and 50 mm. These properties directly affect the production process, as nearly all of Grand Valley’s products are sized at 19 mm or smaller. The high coarse content necessitates a high reduction ratio of over 5:1 at the secondary crushing stage, short of adding a tertiary crusher. The previous secondary, a 150 hp single rotor impactor, was effective and produced good particle shape, but was subject to excess wear, necessitating weekly rotation of its blow bars.

The changes at the primary crusher reflect both the origin of the raw feed and last year’s changes to the primary haul fleet. The Grand Valley deposit is worked underwater, with raw feed cast out and allowed to drain before being hauled to the primary. Even with this draining period, it retains a significant amount of moisture that binds the material together. As a result, effective size separation across the primary crusher’s grizzly (coarse material bypass screen) is relatively slow, and requires a uniform feed rate or the longer retention time of a larger grizzly. The binding was not a concern with the previous primary set up, where a track-mounted jaw received a steady flow of material from a static excavator fitted with a 1.1 m 3 bucket. Since the changes to the primary haul fleet, however, the jaw has been fed instead by a 4.5 m 3 front end loader on load and carry duty, resulting in larger, less frequent loads. As expected, the crusher continued to deliver good throughput rates, but excess material was now carrying over the grizzly and into the jaw. The efficiency of the grizzly was further reduced by mismatch in width between the loader bucket and the jaw’s feeder apron. The loader bucket was some 1 m wider than the grizzly apron, so that part of each bucket load was being dumped directly on top of the grizzly bars.

By contrast, the new Cedarapids jaw has an apron/grizzly combination with an over-all length of some 7 m long or 1.8 m longer than its predecessor. As a result the bucket width is contained within the apron and the dumped material has an opportunity to spread and settle before passing over the grizzly.

The grizzly bar is set with a typical bar spacing of 127 mm, while the jaw itself typically runs at a 100 mm closed side setting and reduces oversize in the feed to a nominal 127 mm minus.

The new 6x16 screen receives primary crusher run and is currently fitted with 1 in and 22 mm screens on the top and middle positions, with the bottom position empty. Here, 22 mm minus material is scalped off and stockpiled, while material larger than 22 mm continues forward to the rollercone. The cone reduces the 127 mm x 22 mm feed material to 22 mm minus, operating in closed circuit with the new 7x20 screen. The screen is fitted with 22 mm and 14 mm screens on the top and middle decks respectively, while its bottom deck currently has one panel of 8 mm square cloth in the feed position and the three panels with in opening in the remaining three panels. Material larger than 22 mm is returned to the cone, while finished products off the screen include 19 mm clear (minus 22 mm to plus 14 mm), H L3 (minus 14 mm to plus 6.3 mm), and 6.3 mm minus screenings. On this product mix, the current average plant throughput rate is a between 250 and 300 tonnes/h.

Power for the new spread is provided by a Caterpillar 3412 diesel engine driving a 545 kW generator. The mobile equipment fleet includes three Caterpillar wheeled loaders – two 980G’s and a 972G – as well as a Thomas 245 HDS skid steer on clean up duty.

Crupi points out that the changes to the crushing set up are no reflection on the predecessor machines: " We have transferred the track-mounted jaw to our recycling yard in Toronto, where it is better matched to the application and is producing good aggregates from recycled concrete and asphalt. With respect to the impactor, we are planning to put it back into the portable spread, but in a new tertiary circuit instead. There, its proven ability to produce good particle shape should be accompanied by reduced wear, thanks to an easier reduction ratio of about 3:1. It will be fed with clear sized 63.5 mm by 1 – in feed, reducing all this material to 22 mm minus."

Further additions to the portable spread include a surge bin and extra product stackers. The surge bin will be inserted between the first screen and the Cedarapids MVP 380 Rollercone to provide a steady feed rate the crusher and maximize its output of cubicle product.

Additional work at Grand Valley includes the rescreening of _-in minus screenings at 3/32 –inch on a separate PEP screen set up. This aims to recover valuable HL3 fraction material that is otherwise being lost in relatively low value screenings. According to Crupi, screenings are typically priced around $5 per tonne in the Toronto area while HL3 commands prices as high as $12 per tonne.

In other company developments, Crupi reports that Grand Valley Aggregates 2000 Ltd. is opening a Toronto aggregate distribution depot to facilitate internal distribution and develop external sales. Based Richmond Hill, the company has aggregate operations near Grand Valley, Orangeville and Campbellville. Mike Crupi and Rod Crockford are president and operations manager, respectively. Sister companies Paveco and Sanan Construction are involved in asphalt production and general construction.

By Andy Bateman

Aggregates and Roadbuilding Magazine
4999 St Catherine Street West. Suite 315
Westmount, Quebec H3Z 1T3
Tel: (514) 487-9868 Fax: (514) 487-9276
EMail: rocktoroad@sympatico.ca

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