lthough roof-bolting is the most effective means of strata control, the continued use of antiquated strata-control equipment poses its own dangers to the operators of these machines, reveals Rham Equipment MD Robert Alcaraz.

Launching a scathing attack against one of the country’s largest collieries, he reports that, despite the availability of safer technologically-advanced equipment, mines persist in the use of unsafe, obsolete equipment due to perceived lower running and capital costs.

This has resulted in rockfalls still being one of the main causes of death and injury in collieries.

“In spite of the successful introduction of remote-controlled roof-bolters to the market five years ago, 90% of mines still use, and specify, old-style machines that require the operator to venture under a roof supported by a temporary roof-support only,” he tells Mining Weekly.

These machines are typically operated manually, requiring the operator to insert the resin capsules and guide the bolts by hand while standing under temporary roof-supports only.

Often, erection of the temporary roof support itself dislodges portions of the roof directly above the operator.

A 20 kg or 30 kg piece, falling from the typical heights mined in South Africa, is a potential killer, explains Alcaraz.

These machines were also not designed for today’s mining heights, and operators have to clamber on top of the machines to reach the actual drilling site, resulting in further injuries from slipping and falling, he points out.

A report from the Department of Minerals and Energy indicates that 43 fatalities and 257 injuries were reported in coal-mines alone last year.

This indicates a fatality rate of 0,75 per 1 000 people at work, and an injury rate of 4,46.

Despite the availability of safer, more advanced equipment, this rate has remained stable over the last three years, with no meaningful improvement having been attained.

The remote-controlled roof-bolter was specifically designed for South Africa’s higher-seam mines, and allows the operator to insert a bolt from an operations station while remaining underneath a substantial steel canopy, reports engineering manager Theo Genis.

“These machines, weighing four to five times the 3 t lightweights of old, are naturally more complex and expensive,” he says.

Still, they remain cost-effective and, at 16c/t, a relatively small component of the continuous miner’s R3/t.

Too often, mines desire the sophistication, but expect the running cost of the old, unsafe, simpler machines, reveals Genis.

The ever-increasing production-cost pressures and the rapidly deteriorating level of available maintenance expertise underground has brought about a tendency for collieries to opt for the cheaper roof-bolting machines, thereby prioritising cost above safety, states Alcaraz.

“The company’s challenge this year has been to come up with an alternative bolting machine taking cognisance of South African mining conditions, available expertise and cost,” explains Genis.

The latest offering from the company is a four-head, manually-operated, totally-enclosed bolter requiring two operators, and which will be able to bolt four times faster than previous machines.

The roof can therefore be secured immediately after exposure, and prevent separation in the roof strata, reveals Genis.

The machine will weigh about 17 t, and will be operate in seams between 2,3 m and 6 m.

The first prototype is due off the line in the next two months, says Alcaraz.

Rham equipment was reportedly the first original-equipment manufacturer in South Africa to manufacture hydraulic roof-bolting machinery, and was established in 1980.

More than 95% of the industry’s roof-bolter requirements have been produced by the company since that time.

Machines capable of bolting in seam heights from 900 mm to 6 m have been designed and built at the company’s facility at Olifantsfontein, Gauteng.

Apart from exports to China and Wales, the company has secured contracts to supply all the roof-bolters for the mechanisation project at Wankie Colliery in Zimbabwe.

Negotiations are also under way at present to supply bolters to the US market.

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