March/April 2013


Straight talk on longwall mining

By Antony Strickland

As an experienced longwall miner, who has worked on longwall coal mining projects around the world including in Canada and China, I feel the need to dispel misconceptions about the technique and to comment on the idea of Chinese miners being imported to work in B.C. For the Canadian mining community, finding skilled miners to operate the longwall is not the greatest concern; instead, it is the geology of the site and the logistics of sustaining longwall operations in the long term that are crucial to safe and successful mining. Longwall failures in Western Canada have occurred under foreign (British) management before, in geological conditions with which they were unfamiliar, at sites operated by imported longwall miners. Let’s not repeat this mistake.

In mountainous areas of Western Canada, there will be few (if any) places where the geology will be suitable for longwall mining. Faults with a displacement greater than half the thickness of the seam are difficult for longwalls to negotiate. Roof and floor conditions are often weakened by mountain building tectonic forces.

Even if a suitable site exists, any longwall mine will fail without attention to efficiency and best practices. Detailed logistics planning is key to success. While a panel is being mined, the next panel has to be developed. As soon as a panel is mined out, the longwall equipment – which includes the shearer, 300 metres of face conveyor, 200 support units, electrics and other ancillary equipment – must be disassembled and transported up to four kilometres to the new face and then re-assembled. The process requires careful planning and special equipment for loading and transporting large, heavy loads over long distances, and special care of roof control while the hydraulic face supports are being withdrawn. In the U.S., this process is done in about seven days.

From my observations of the longwalls in China, which I visited as a technical advisor in 2004, I doubt that a longwall equipment transfer would be accomplished safely in seven days. At mines I visited in Heilongjiang Province, only single entries were used at each end of the face so that there was no way to keep “gob” gases away from the working face. In the U.S., having three entries is common practice. In China, the hydraulic supports oil reservoir allowed dirt to enter the system. I saw four or five hydraulic support legs out of service and awaiting replacement. Where I visited, there were no geologists on the engineering staff for 12 mines. Rock mechanics was not applied to mining and roof control – it was hardly understood.

And finally, to address the issue of Chinese labour, let us consider the manpower requirements of both the longwall and the development phases: longwall equipment is simple to operate, requiring no special physical strength or dexterity. The equipment can only be operated as it is designed; therefore, little decision-making skill is needed. In the U.S., a typical longwall operating crew consists of 10 miners or less per shift, including the supervisor. Longwall operations require no more than 30 miners for three shifts. Canadian miners with underground experience could, in my opinion, master the process in one week. Excluding the various support and maintenance workers, typical longwall development work requires about 48 miners, including two mechanized development units, working three shifts per day.

Most Canadian miners can handle this work and it would not be difficult to find men familiar with the equipment used. In addition, British Columbia legislation requires the mine manager to be conversant in the English language and to know the Provincial Mines legislation. Employees, too, should be able to read and understand the literature given to them. There is also a need for communication between the inspectorate, mine management and miners.

How these safety-related questions might be resolved has not yet been addressed.

Antony Strickland received his mining education and training in the U.K. He came to Canada in 1967 where he worked as supervisor, mine manager, and project engineer in Rocky Mountain underground coal mines in Alberta and B.C. He joined Norwest Mining Consultants in Calgary in 1982 and has worked on longwall projects in the western U.S., Indonesia, Australia and Mexico. He is now retired.

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