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July 8, 2015
High in the Andes mountains in the northernmost part of Chile is the giant Collahuasi mine, one of the world’s largest copper resources.
Here, mining operations take place at altitudes of 4 000–4 800 m above sea level. Operated by Compañia Minera Doña Inés de Collahuasi and owned by Anglo American, Xstrata and a Japanese consortium, the mine extracts and processes sulphide ores to produce copper and molybdenum concentrates. Of these, copper concentrate accounts for more than 90 percent of the mine’s output.
In this demanding environment characterized by low oxygen levels, extremely cold temperatures in winter and unpredictably violent electrical storms, two diesel powered Pit Viper drills from Atlas Copco are taking the conditions in their stride.
These units, a PV-271 and the larger PV-351, were delivered to the mine site during 2011 and are the only diesel powered units in a fleet of 11 blasthole production rigs, the others being electric.
Carlos Correa Echeverría, Superintendent, Drilling & Blasting, told M&C that the rigs are proving to be ideal for the conditions.
“To reach our strategic objectives, we need all our equipment to sustain consistent and reliable performance while operating at maximum production capacity,” he says. “Also important is the versatility of the rigs. Moving electrical cables around results in lost time which is why we decided to go for a diesel version. We like the versatility of the Pit Viper drills as we can move them around quickly and easily.
“We have also hit a phase here at the Rosario deposit where the working area is narrow and there is an influx of water so it is very convenient for us not to have to deal with the cables of the electric machines in that area.”
However, the high altitude of this worksite presents other challenges in terms of power loss due to the low oxygen level. “This makes the rigs less efficient so we had to compensate for this by fitting them with higher-powered engines and compressors,” explains Paulyn Espindola, Product Manager at Atlas Copco.
The PV-351 for example, is fitted with an engine that delivers 1 650 hp at 1 800 rpm, as well as a larger compressor – 3 800 cfm (110 psi/ 7.6 bar) instead of 3 000 cfm. The high altitude of this region also means extreme cold, especially in winter (July to September), when temperatures often drop to –40 C°. “As a result, the rigs also have to be fitted with a heater and an on-board generator,” continues Espindola, adding that the performance of other items such as the water pump, fuel, battery and oil can all be affected by the low temperature.
The rock at Collahuasi has an average compressive strength of 100 MPa with some sectors reaching even 250 MPa. For comparison, the rock at other local mines has a typical strength of 60 MPa.
Blasting is carried out once a day and four different drilling patterns are used, depending on the area. The presence of water decides whether heavy ANFO or ANFO and emulsion explosive is used.
Atlas Copco also supplies all consumables such as rotary bits (including Secoroc Tricone bits), drill pipes, bit adaptors, top sub adaptors and rotary deck bushings.
Although both rigs are performing well, it is the larger PV-351 that appears to be stealing the show. During M&C’s visit, this unit was drilling about 10 percent faster than the fleet’s electric rigs – roughly 58 m per hour compared to an average of 50 m/h for the electric rigs.
This was confirmed by the operator Eduardo Macheo. “I like this machine,” he said. “It’s fast and I’ve been able to drill 780 meters with it in one 12 hour shift, including a one hour break, but I can do better. My personal record is 800 meters in one shift and I’m sure I can reach that with the PV-351,” he laughs confidently.
Macheo was familiar with this rig from the start having previously worked on a Pit Viper 271 at another copper mine, although not equipped with the Atlas Copco Rig Control System (RCS).
“Before I came here I had the opportunity to operate the PV-271. I had a console, not joysticks, so the joysticks and the whole computerized system were a new experience for me.”
The RCS computerized system is standard on all PV-351 rigs and provides a high level of automation, including options like autodrilling, GPS hole navigation, rig remote access with communication, remote tramming, Measure While Drilling, tele-remote operation and other advanced features.
All the functions are controlled through a touch screen, two joysticks and push-buttons on the operator’s seat, so when the seat swivels, so do the joysticks and screen.
When the two Pit Vipers arrived at the mine, Atlas Copco provided two instructors, Luis Galleguillos and Hugo Moyano, to train approximately 20 operators. The technical training was completed in January this year. Macheo admits it has been a learning curve but an easy and enjoyable one.
“It wasn’t a problem at all to learn to operate the rig – the controls are very straightforward,” he says. “I really like the cabin and its great visibility. It’s easy for me to work in here and it feels safe.”
Featuring a powerful hydraulic pull-down of 130 000 lbf (534kN), the PV-351’s high capacity has also impressed the Collahuasi miners. “A diesel rig with this capacity didn’t exist before and it has resulted in increased availability for us,” says Correa.
Operations at Collahuasi started in 1999 and after expansion in 2004 the mine reached its current production capacity of 500 000 tonnes of copper per year. A prefeasibility study was initiated in mid-2011 to determine whether a second expansion would be viable in order to take production to more than 1 Mt/year – and a step closer to the mine’s vision of becoming the world’s leading copper producer by 2020. The mine employs about 5 500 people, including contractors, and operates non-stop, 365 days a year, working two 12-hour shifts per day.
The technology was one of the main reasons why Collahuasi decided to use Pit Viper rigs. “Atlas Copco offered us the possibility of automated drilling and this is very important for us,” confirms Correa. He says he believes that totally automated drilling is the future and that the mine needs to get ready for it.
“Ideally, we will reach a stage where drilling can be carried out without an operator inside the machine. We have been looking at the Aitik mine where they’ve been drilling remotely with the operator placed at a distance from the rig,” he says, referring to the Swedish copper mine, one of the world’s most cost-efficient operations where four Pit Viper 351 drills are at work.
“Continuous improvement and innovation through the use of new technology is another important strategic objective for our company,” he points out. “Autonomous technology would mean being able to standardize our drilling operations and increase our production.”
In addition to the newly opened Rosario South 1, Collahuasi is planning to start up another area, Rosario South 2, in 2013.
“Next year we have to replace two of the older drilling rigs in our fleet as they’re coming up for retirement and I’ll be looking for the best machines for our needs,” concludes Correa. “There are a great number of Pit Viper rigs operating in the Chilean mining industry which proves that these machines work in our conditions and that Atlas Copco provides appropriate support.”