BY SCOTT HUNTER HADDOW
There is a new development in an old invention on the rise that could help blast away the cost of mining at deeper depths.
Paul Dunn, director for the Centre of Mining Technology and chair for mining technology with Mirarco, has developed a better water-jet scaling nozzle and system used in the scaling process of drift walls.
“Water jet scaling is showing promise,” says Dunn.
It all started when Dunn went in to inspect a water jet scaler in operation at Falconbridge’s Fraser mine. The unit was not functioning properly and Dunn evaluated the system. He made some changes to the unit to get better results, but he saw an area where he could drastically improve the whole process.
“I have actually been dabbling with high-pressure water jets since 1986.”
With financial backing from Inco Ltd., Falconbridge Ltd., Placer Dome, and additional support from Consolidated Rubber/ Mansour Mining Inc. and Sandvik-Tamrock, Dunn began to create a better system based on a lower pressure with higher flow rates.
“We are looking at 2000 psi (pounds per square inch) with a flow rate of 300 litres per minute,” Dunn says.
At present, a person will go in and do manual scaling with a bar or there will be a mechanical impactor. Dunn’s water jet will provide non-contact scaling from a distance. There are several advantages to the water jet process, he says.
“It is very easy to automate, and you can tune the pressure and flow rate depending on the material and it is very quick,” says Dunn. “It can scale a drift four-and-a-half metres wide by four-and-a-half metres high by three metres deep in nine minutes.”
The real advantage will be saving time in the support system. After drilling, blasting, mucking and scaling, a drift needs support. Right now a bolt-and-mesh support process is used.
“The bolts and mesh are a reliable system, but it can take an hour and a half to do the work in the space.”
The water jet would work inconjunction with a shotcrete or membrane liner support system.
“Both of those methods need a clean surface to adhere to,” says Dunn. “The water jet does that and the equipment used for shotcrete and membrane lining can be retrofitted to use the water jet.”
The water jet can be safer than standard methods, he notes.
“You can sit in the cab and blast the loose material away from a distance.”
Dunn has carried out preliminary tests at the Norcat adit in Sudbury. The aim was to determine the feasability of water-jet scaling in hard-rock mining.
“The trials went brilliantly,” says Dunn.
Because of the success of the trial runs, the next stage is to test the water jet scaling in conjunction with spray-on liner supports. The testing is expected to begin later on this year.“There have been no real problems so far, and the development will go quickly now.”
Besides attracting interest from local mines, the water jet has also gained interest from around the world.
“There has already been some interest from Western Austrialia and Scandanavia,” Dunn says.
