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July 8, 2015
High altitudes and harsh weather conditions go hand in hand in Latin America, not least in the mountains of Argentina.
Close to the Chilean border, about 350 km northeast of the city of San Juan, is the Veladero gold mine operated by Minera Argentina Gold, a subsidiary of Barrick, one of the world’s leading gold producers.
Located at 4 000–4 850 m above sea level, the mine can only be accessed via a 156 km road which sometimes reaches heights of more than 5 000 m. It takes about seven hours to drive and conditions in winter can be so severe that shelters have been built every 20 km to protect workers and travellers from the elements.
At this altitude, the temperature drops 2 C° for every 300 m of elevation. In winter, the temperature averages –10° C during the day, dropping as low as –16° C at night, or even as low as –40° C with the wind chill.
The winds can be very strong, sometimes 80–100 km per hour and extreme winds of up to 220 km per hour have been recorded by the weather station, says Mining Superintendent Jose Luis Fornés.
Winter can be so harsh that the road is often blocked, prompting the mine to adopt emergency measures and it also has its own operating theatre and surgeon should a medical problem occur while the road is closed. Added to this is the constant threat of violent thunderstorms.
So what does such a harsh, unpredictable environment mean for the equipment? “The special conditions here complicates our logistics,” admits Fornés. “This is a very remote site. There’s nothing within a 100 km radius so we expect reliability from our equipment and suppliers.”
The drilling fleet consists of 11 diesel powered rigs including an Atlas Copco Pit Viper 271. It is deployed in Pit Amable, drilling 105/8″ production blastholes. The mine uses standard 15 m high bench drilling with a hole spacing of 7×8 m in waste rock and 6.5×7 m in ore.
A sturdy and powerful blasthole drill rig, the PV-271 features a pulldown force of up to 311 kN (70 000 lbf) and a 34 tonne bit load capacity for maximum productivity in hard rock formations.
The rock here is of silica-type and varies in quality throughout the site. “We have areas where the rock is hard, others where it is quite fragile and others where it is not only hard but also highly abrasive,” says Ramón Arjona, Drilling & Blasting Senior Supervisor.”
Victor Astudillo, operator of the PV-271, knows this only too well. He explains that depending on the area where they are working, drilling a production blasthole can take from 18 minutes to one hour. “Most of the rock is hard so on average it takes about 45 minutes to drill a hole,” he says.
Veledero extracts 230 000 tonnes of rock per day from its three orebodies – Amable, Filo Federico and Argenta. Gold production in 2011 was 0.96 million ounces.
Working at this altitude means that with every additional meter of elevation, air density and pressure decrease and certain components and materials can no longer be relied on. “Our winters can affect a machine drastically,” says Arjona, explaining that some aspects of the machine such as the air and water circuits freeze easily.
In order to beat the conditions, the PV-271 had to be equipped with special features such as a more powerful engine and compressor and a cold weather kit which includes additional covering of the machinery housing, allowing for warm start-up and operation in extreme ambient conditions. Arjona says the PV-271 is doing “very well” with reported good availability ratings and adds: “That’s our little princess. We can rely on that machine and that’s what’s important.”
The fact that Atlas Copco was able to equip the rig for the conditions was decisive. Now it is expected to please the miners even more when it is upgraded with the Rig Control System (RCS) technology.
This will provide automated options including autoleveling, autodrilling, GPS hole navigation, rig remote access and communication, wireless remote tramming, measure while drilling data log files and tele-remote operation. As Carlos Cavanillas, Drilling & Blasting General Supervisor, says: “We’re going for the full set of RCS functions and looking forward to using this technology at Veladero.”