South Africa Digs Out of Its Mining Crisis

The country's sagging gold industry looks to research to develop less costly and safer deep-level mining techniques

THERE is a sense of expectation in the crowded change-room as we fasten white overalls and straighten our hard hats. Minutes later the huge metal cage - with three decks containing 30 people on each deck - is hurtling toward the center of the earth at 2,500 feet per minute.

The deafening noise of steel-on-steel, the humid air, dank aroma, and surrounding darkness reminds the visitor that he is entering an alien and dangerous world.

Western Holdings mine - No. 3 shaft - is typical of hundreds of shafts that penetrate deep into the reef of gold-bearing rock that describes an arc from a point east of Johannesburg and southward to this Orange Free State town. But the magic of gold - a symbol of South Africa's economic wealth - is beginning to fade because of soaring production costs and a static world gold price.

``Gold has become more a luxury commodity used in jewelry than a store of wealth,'' says Anglo American Gold Division chairman Clem Sunter, announcing a 19 percent fall in profits for the first quarter of this year.

As South Africa's gold industry enters its worst crisis since its inception a century ago, it is looking to its research wing to streamline techniques and cut costs.

Recent advances in deep-mining technology hold out the prospect of a safer working environment and savings for mine owners that, in turn, could reduce the number of retrenchments and mine closures.

``If you put together all the progress that has been made, it will certainly help the gold industry through difficult times,'' says John Sheer, director of the Chamber of Mines Research Organization.

Despite safety measures in effect, South Africa's 450,000 black workers in the gold mines face constant danger in the form of rock bursts, gas leaks, underground fires, and land falls.

About 9,000 mine workers are injured - and 500 die - each year. But the most serious threat facing black mine workers at present is that of retrenchment in a climate of economic recession.

Since black mine workers went on a nationwide strike in 1987, some 80,000 jobs have been cut - at least 40,000 through direct retrenchment. The industry predicts that a further 80,000 jobs are threatened.

Last week(Apr.18) the giant Anglo American Corporation announced that it is cutting back its work force - which numbered 200,000 two years ago - by a further 12,500 to about 180,000.

South Africa's share of world gold production has dropped from 70 percent in 1980 to 36 percent in 1990.

But recent breakthroughs in the cooling of deep-level mines, hoisting methods, and techniques for stabilizing rock could hasten the mining of new gold deposits.

One major advance has been in the area of overcoming heat stress in mines that go two miles down, such as the Anglo American's Western Deep Levels mine - the world's deepest mine - near Carletonville.

``About 250,000 [50 percent] of the work force in the gold-mining industry operate at one mile or deeper and about 25,000 work at depths of below 1.6-miles,'' says Horst Wagner, senior operations manager for the Chamber of Mines.

Temperatures, which average 15 to 20 degrees C (59 to 68 degrees F) on the surface in summer, increase by 1 degree C for every 250 feet of depth in most of South Africa's gold mines.

This means rock temperatures of up to 50 and 60 degrees C (124 to 140 degrees F) can be encountered at a depth of two miles.

`WHERE environmental temperatures approach body temperature (37 to 38 degrees C.), the danger of heat stress occurs,'' Dr. Wagner says. ``Research has shown that about 10 percent of people are heat intolerant.''

Methods have been devised to identify such people and ensure they have surface jobs.

The ideal is to cool the air in the mine to a temperature of 28 degrees C (82 degrees F).

The gold-mining industry has pioneered a system of ice-cooling that is more efficient - and cheaper - than water- or air-cooling.

``In deep mines, air-cooling is ineffective because the air increases by 5 or 6 degrees C for every 900 yards of depth due to contact with the rock, friction, and auto-compression,'' says Wagner.

Water-cooling involves massive refrigeration costs to cool the water, and electricity costs to pump the used water out of the mine.

``The beauty of ice-cooling is that when it changes from solid to liquid the latent heat factor is utilized,'' Wagner says. ``Four times the volume of water would be needed for the same result.''

The new two-mile deep East Rand Property Mine east of Johannesburg has been designed to run on ice-cooling with an ice-making machine that produces 6,000 tons in 24 hours. ``The ice is then pumped down the mine in a pipeline and cools down the air through rock contact and direct heat exchange through water sprays,'' Wagner says.

Increasing use of hydro-power mining equipment - rock drills driven by hydrostatic pressure - means electricity savings, improved labor productivity, and safer conditions in deep-level stoping (rock-face) operations.

A first visit to a stope-face is a sobering experience for a stranger to the mines. This is where black mine workers - supervised mainly by whites - operate the heavy hydraulic drills, often crouched in narrow openings in the rock. Here sweat mingles with water-sprays in a relentless battle to release the gold ore from the compacted rock. But technological research can make a difference.

The industry has developed a water-powered impact hammer for breaking quartziferous rock that is so efficient that it eliminates the need for explosives - the ultimate goal of mining research.

The new Northam platinum mine owned by Goldfields north of Johannesburg has been developed exclusively on the basis of hydro-power.

Other major advances have been made in the field of rock stabilization. Hazardous rock bursts currently account for more than half of all mine accidents.

One method, known as back-filling, fills the mined areas by pumping coarse sand and mined material back into the void. The technique is being used in coal mines in Poland and in the deeper coal and silver mines in the United States, according to Wagner.

THE industry has also developed a stope-face support system that allows props to be placed within a yard of the stope-face. ``This significantly reduces the chances of blast-induced rock falls,'' Wagner says.

Perhaps the most revolutionary breakthrough in this field is the development of hydraulic props to replace the old wooden pillars. The rapidly yielding hydraulic prop gives way quickly but then returns to take up the slack after a rock burst, thereby achieving a far higher degree of control in rock movements.

Already about 250,000 hydraulic props are installed in mines nationwide. They are also being used in mines in the US, China, and Germany.

The biggest potential cost-saving is in hoisting, where advances in the steel used for wire rope and the findings of safety research have brought the industry to the verge of a breakthrough.

Instead of two sub-shafts having to be sunk in deep mines in the future, a single shaft with one hoist will suffice in even the deepest mines.

Reduced safety standards are being tested with ore hoists and the industry is waiting for the government to approve legislative implementation.

Wagner predicts that using single hoists could cut the time needed to build a new mine by two years.

On capitalization of $800 million, this could mean a savings of $250 million over two years in interest alone.

It would also mean a huge savings in capital expenditure and far greater efficiency in the running of the mine.

``As most new discoveries are around the two-mile mark this could help the industry immensely in the midst of its deepest crisis,'' says Adrian Du Plessis, a senior general manager of the Chamber of Mines.

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