New portable spread combines productivity, control and portability

Madoc, Ont.-based Danford Aggregates Ltd., a division of Danford Construction Ltd., is a relative newcomer to aggregate production, having utilised contract crushing at the company’s quarries and pits until just two years ago. The switch to in-house production was made last year and represents a major commitment for a company of this size. Consistent product quality, high productivity, and ease of portability were listed as key requirements for its new plant, and the resulting spread has successfully combined all of these in a com-pact package. Alan Danford expects the plant to produce about 400 000 tonnes of aggregates this construction season, divided equally between the company’s own aggregate operations and contracted production.

This workload will take the plant to Danford’s Francis and Madoc quarries as well as its Thompson and Ivanhoe pits and customer operations. The new spread was acquired from ELRUS Aggregate Systems in two phases, with the primary crusher, control tower and generator acquired initially, followed this spring by a new cone crusher and 6x20 screen. When visited by Aggregate & Roadbuilding, the plant was configured to reduce all of its 610 mm minus feed to 22 mm minus Granular A. The plant had just completed a run of three products – Granular B Type II (75 mm minus), HL3 (13 mm x 6 mm) and 6 mm minus screenings at the company’s Francis quarry.

For the job, a Caterpillar 966G loader fed the plant’s ELRUS 24x42 primary jaw crusher, with product from the jaw conveyed to a 7.6 m 3 ELRUS surge bin. The bin in turn fed a 6x20 ELRUS triple-deck screen, where Granular A product was screened off and stockpiled by a 30 m Powerscreen stacker fitted with a Siemens Milltronics belt scale. Meanwhile, material larger than 22 mm was conveyed to a Sandvik H3800 Hydrocone crusher where it was reduced to 22 mm minus and returned to the screen feed belt.

Jamie Danford, in charge of aggregate operations for the business, explains that the operator is able to regulate the flow of material at two separate locations, providing smooth flow for consistent quality as well as maximum productivity. At the front end, the feed rate to the jaw is regulated by the 5.5 m long vibrating grizzly feeder with variable speed control. In addition, the variable speed belt under the 7.6 m 3 surge bin provides the operator with close control of the feed rate to the secondary plant.

Product quality is further enhanced by the Sandvik ASR Plus system that automatically maintains a preset closed side setting on the H3800 hydrocone. Here, continuous adjustments are made to the crusher setting in response to load fluctuations, as reflected by changes in the hydraulic pressure that maintains the crusher opening, as well as the power required to drive its 200 hp electric motor. As a further refinement, the system also provides the operator with the option to fine tune the product size by making on the fly adjustments to the crusher setting. When different products are required, automatic size selection for up to five different sizes can be made from preset programs.

To boost productivity, the jaw is fitted with an optional hydraulic grizzly as well as a conventional grizzly screen ahead of the jaw. In operation, the loader operator dumps shot rock over the hydraulic grizzly, which then retains any oversize lumps and prevents them from entering the jaw. The hinge mounted hydraulic grizzly is then tilted up periodically to clear its bars of material.

Another simple but effective touch on this spread is the optional overflow chute above the hydrocone. In normal operation, the cone’s feed hopper is kept full to ensure that the crusher itself is choke fed. Should the crusher feed rate exceed the crusher throughput for any reason, material building up in the hopper merely bypasses the cone and returns on the next cycle, minimizing spillage and clean up.

Jamie Danford reports that the plant averaging 200 tonnes/h when on straight Granular A (19 mm minus) production. In terms of productivity, this translates into an impressive 65 tonnes plus per man-hour, given a crew of just three, including one plant and two loader operators.

All the trailer units incorporate hydraulic jacks that assist in rapid set up and take down, while the 6x20 screen and its trailer incorporates a number additional devices. The screen itself has hydraulic raise and lower capability, with a box section bar holding the screen at a preset 15-degree inclination while working. The conveyor belt from the screen to the cone also has hydraulic side shift adjustment, so eliminating the need for the screen and crusher trailers to be precisely positioned during set up.

Finally, the screen’s two reversible and extendable cross belts retract within the over-all chassis width for travel. All the new units are on ELRUS tandem chassis, with the exception of the heavier jaw that is on a three-axle unit. Each chassis is fitted with a small hydraulic pump, driven by a 12-volt motor, with power for the motor itself provided by cable connections to the battery of a service truck. The new spread includes the familiar ELRUS 8x10 control tower, set in the roof of a 13.7 m trailer and raised or lowered by a similar hydraulic system. The trailer also houses spare parts, a Cutler Hammer Motor Control Centre (MCC) and a Cat 3406 diesel engine and 365 kW generator set. This provides power for the whole plant apart from the self-powered stacker, with long running times provided by the under-slung 6365-litre capacity diesel fuel storage tank incorporated into the trailer.

The Francis quarry is Danford’s most recently commissioned aggregate operation. Located about 25 km north of Belleville, it began operation in 1995 and is one of the few approved sources for coarse concrete aggregates in the area, supplying customers as far as 100 km away. Its Bobcaygeon limestone reportedly delivers good results in the MicroDuval abrasion test, (successor to the L.A. abrasion test) with results between 10 and 12% compared to, for example, a maximum allowable limit of 21% for Heavy Duty Binder Course (HDBC) asphalt aggregates.

Danford Construction Ltd. was estab-lished in 1948 and still operates out of its original Madoc location. Today’s five co– owners include Walter and Doug, sons of founder Samuel, together with third genera-tion sons Alan, Jamie and Sam.

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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