SCOOPING OUT
the riches of Broken Hill
with a smooth- running fleet
of mine vehicles

In 1928, the owner of a farm in South Africa decided to drill for minerals on his land. He missed a main orebody and gave up. At the same location today, copper, lead and zinc has been mined for 17 years.

The Broken Hill mine, located in the area of Northern Cape Province known as Bushman Land, was opened in 1980 following exploration of the orebody.

Today the mine employs nearly 900 people and produces 1.5 million tonnes of ore per year, from which processing yields the end products of copper, lead and zinc.

Broken Hill is operated by the Black Mountain Mineral Development Company (BMM), whose parent company is Gold Fields of South Africa Ltd.

Spiral declines

Because of varying ground conditions, BMM uses several modifications to the conventional cut-and-fill stoping methods, such as ramp-in-stope and crown ramp-in-stope mining.

These methods are supported by mechanized equipment from Atlas Copco, which includes a total of six Boomer, Boltec and Simba drilling rigs - and a considerable fleet of Atlas Copco haulage vehicles.

Access to the mine is via two spiral declines, 5 m wide and 4 m high and at a gradient of 20%, which descend into the footwall of the orebody. The declines give access to levels at vertical intervals of 35 m.

With an ST1000: From left, Houston Fyfe, Atlas Copco South Africa, Simon Greyling, Dave Thompson, Atlas Copco Wagner, Casper Swart, Atlas Copco South Africa and Koos van Zyl, Atlas Copco South Africa.

The management says that the nature of the orebody, which becomes narrow and twisting with deteriorating ground conditions, makes it essential to have equipment which is small, manoeuvrable and productive enough to maintain production targets, adding: "In some cases a good, reliable and remote-controlled scoop is essential."

And that is why the Atlas Copco vehicle fleet consists of two MT-426 articulated dump trucks of 26-tonne capacity, with a third on order, and nine Scooptram LHD vehicles comprising six ST-8B 12-tonne units, two 10-tonne ST-6C vehicles and one ST1000 10-tonne Scooptram, with a further ST1000 on order.

BMM initially used Wagner trucks before switching to another supplier. The first Atlas Copco MT-426 arrived in 1996. Now a third unit is on order. The company likes the robust design of the vehicles and considers them a successful investment.

Few problems

Says Chief Engineer Simon Greyling: "We have very few problems with them - they just run. Instead of air brakes, they have the spring applied hydraulic release (SAHR) braking system, which functions at less cost."

In addition, BMM has not encountered the high costs of repairing axle differentials and transmissions associated with other trucks. Simon Greyling comments: "The Atlas Copco Mine Trucks can certainly take the abuse they get when working underground here!"

There were a few initial hydraulic problems when the first ST1000 LHD vehicle arrived in December, 1996. But after some changes were engineered by Atlas Copco, BMM says it has performed successfully and achieved good productivity, moving 25,133 tonnes per month.

Charlie Howard: "There have been no problems with the Scooptram's advanced technology."

Engineering Manager Charlie Howard adds: "Initially, we were nervous about the new technology incorporated in the Scooptram 1000 - but its performance has been a pleasant surprise. It is extremely manoeuvrable and there have been no problems with the advanced technology. Now we are committed to buying another."

Easy transition

LHD operator Manie Booysen has handled all the Scooptrams as well as trucks - and has been delighted with the ST1000 since its arrival.

"The joystick controls make it easier to handle than other models and it's simple to load in one pass," he says. "It is a very comfortable ride, visibility is excellent and everything we need to get at for the daily checks is easily accessible.

"It was also a very easy transition from the older machines to the new ST 1000. I had no problems with using the monitor system and card reader."

In a report on the ST1000, the mine noted the following advantages over older machines:

- high-lift Z-bar geometry with an aggressive bucket which enables single-pass loading
- reduced maintenance due to easy replacement of components
- electronic transmission, giving total control in automatic or manual operation
- clean-burning engine producing lower emissions and uses less fuel.