Innovations HGOODBYE BITS AND STEEL

The mining industry could be facing a revolution in rock drilling within the next three years.

“Indications are that our costs will be lower than those of either pneumatic or hydraulic drilling,” says John Stirling, chief executive officer of Indescor Hydrodynamics. He is referring to his company’s dramatic development of a rock drilling machine that uses the tremendous forces of high-speed water jets to cut through hard rock at rates of 1.5 m per min. Dr Richard Puchala, Indescor’s director of research and development says a prototype machine, designed for cutting 1 1/2-in slots in granite should be ready for testing in a Quebec quarry this month. The unit will be used to minimize waste rock when cutting blocks of granite from the quarry. This machine has been clocked at a rock removal rate of 2 cu m per hour in Stansted granite. Water consumption is about 20 gal per min. With slight modifications, Stirling says, the same machine will be redesigned to drill small-diameter holes for installing rock bolts in underground hardrock mines. The rough rock surface on the wall of the hole produced by the drill provides better load-carrying capacity for cement-grouted and Swellex rock bolts because of an added friction component compared to holes with smooth rock walls.

The company should know by the end of this year whether or not both of these machines can be developed into a marketable form. If a marketable machine can be built by early 1988, this will put the company well ahead of all the optimistic objectives set out in a financing agreement with the National Research Council (nrc). That agreement, negotiated in October, 1985 through the nrc’s Program for Industry/Laboratory Projects (pilp) granting system requires the company to build two prototype machines by the end of 1987. These prototypes would be used to prove whether or not the machines can be operated at an economic rate. “If it’s not economic, we wouldn’t be going any further,” Stirling says. The nrc put up $330,000 and Indescor, which is a publicly traded company listed in Vancouver, put up an equal amount for product development.

Because of the success of the development program so far, Stirling sees no reason why the company could not manufacture water jet drilling machines capable of drilling drift rounds, longhole blastholes or large- diameter blastholes 150 ft long for the mining industry. Noise levels produced by the machine are no higher than those of hydraulic machines, and water consumption can easily be handled by standard mine pumps. Indescor has no experience marketing machines in the mining industry, so it has consulted with hdrk Mining Research (a joint venture established in 1984 by Inco, Noranda, Kidd Creek and Falconbridge) and the Ontario Centre for Resource Machinery Technology in Sudbury, Ont.

Indescor is instead, aggressively attacking the concrete demolition and quarrying industries. They have already brought a concrete cutting machine, called a concrete demolisher, up to the operating standards of the construction industry. It is providing the company with modest revenues this year. Two machines are working in the field and seven more are on order.

Closer to mining, geotechnical engineers from Atomic Energy of Canada’s underground research lab near Pinawa, Man., are interested in using the rock-slotter as a cost- effective way to bore large-diameter (40-in) holes 15 ft deep in solid granite for storing spent nuclear fuel canisters in underground repositories. They visited Indescor’s manufacturing plant in Concord, Ont., in August to see the 1 1/2-ton prototype machine in operation before it went to the Rock of Ages granite quarry in Quebec’s Eastern Townships.

For the mining industry, the machines promise several distinct advantages over conventional pneumatic and hydraulic drilling technology. Because no large mechanical forces are involved, the equipment can be small and lightweight — definite advantages in any underground operation. And the only big, consumable components of the units are the water nozzles and diesel or electric energy. This could translate into considerable cost savings in terms of the inventory control and management typically required for drill steel and bits. In terms of energy efficiency, the triplex pumps used by Indescor are about 90% efficient. It operates at relatively moderate pressures of 100 mpa and hydraulic power of 100 kw.

In mineral exploration, the waterjet slotting machine could conceivably be used as a substitute for circular saws that use diamond-impregnated blades to cut trenching samples from rock outcrops. However, recovering the cuttings from the high-pressure slotting machine could be a problem. Indescor already has plans to use the machine to cut slots in outcrops to assist utilities laying fibre-optic cables across rough terrain.

The machine may also find application in taking large-scale rock core samples. The rock-cutter could be programmed to cut in a circular motion, producing a long, cylindrical sample of rock. Then, by changing the nozzle in solid granite. Whether or not it could be more cost-effective than diamond drilling is not known.

Once the company has a prototype machine ready and knows what criteria to apply to the final design of a marketable machine, it will get a better handle on penetration rates and costs per foot.

Spar Aerospace, which has recently developed a rock-bolting and screening machine for Inco Ltd, is one company interested in Indescor’s work. If penetration rates and the cost of drilling holes for rock bolts are competitive with hydraulic drilling technology, these new machines will make an attractive addition to the Spar bolter.

Dr Puchala has co-authored a paper on the slotting machine, which was presented at the Fourth U.S. Water Jet Conference, held at the University of California in Berkely, Calif., August 26-28, 1987.