Atlas Copco at Fresnillo

Transcription

1 UNDERGROUND DRILLING 41 Atlas Copco s Simba M4 C drill rig is used at the Fresnillo mine in Mexico Ace in the hole Ailbhe Goodbody looks at the use of in-the-hole drilling in the underground mining industry, as well as related technologies such as drilling consumables and training simulators In-the-hole (ITH) drilling is a commonly used method in the mining industry. It is also known as down-the-hole (DTH) drilling, particularly for surface applications where the direction of drilling is downward; however, in underground drilling the term ITH is more commonly used as the rigs may drill in other directions too. In ITH drilling, the drill string rotates while the drilling hammer continuously strikes into the rock. Inside the hammer, a piston powered by compressed air gives the drill bit its striking power. Combined with the rotational movement, this means the rock is crushed very efficiently. Rock cuttings are then blown clear by the air exhaust from the hammer. ITH drilling is preferable in many drilling applications for a number of reasons. For example, hole deviation can be a major problem with top-hammer drilling and this problem becomes exacerbated when drilling deep holes. Also, while they have a very high penetration rate for shorter holes, top hammers experience a considerable loss of penetration rate when drill depths exceed 15-20m. This is because energy is reflected at every drill-rod connection, so the penetration rate decreases as new sections of drill rod are added while at the same time hole accuracy deteriorates rapidly. With ITH drilling there is no such energy drop, as the percussion unit is located in the hole and delivers the energy directly to the drill bit as opposed to being transferred through a long drill string. As a result, ITH drilling consistently provides straighter drilling. Peter Corcoran, director of sales support and business development, underground ITH drilling at Sandvik Atlas Copco at Fresnillo Fresnillo, the world s largest primary silver producer, is using Atlas Copco equipment at its Fresnillo mine in Mexico. For production drilling at the San Jaime level in the San Carlos zone, the mine uses the Simba M4 C in-the-hole (ITH) drill rig with 114mm rock drills to maintain straight holes, although these are reduced to 76mm if unconsolidated rock is encountered. The blocks are mined in 25m depths from stopes 4.5m x 4.5m in diameter and 200m in length. The Mining, explains: A top-hammer drill is faster at the collar of the hole. As the hole gets deeper, the penetration rate balances out because the energy within an ITH-drilled hole doesn t change. ITH drilling also excels in removing cuttings from the bore hole, while top-hammer drilling quite often suffers in this area when drilling to depths over 15-20m. Top-hammer drilling can also have a high consumable cost. Consumable cost for ITH drilling is considerably less as the cost of drill-string components are significantly less than for top hammers With ITH drilling there is no such energy drop, as the percussion unit is located in the hole and delivers the energy directly to the drill bit holes are 30m deep to allow for the stope heights and drilled at 65 angles in a 2.4m x 2.6m pattern. Both the Simba 1254 top-hammer model and the Simba M4 C-ITH production rigs are used. Antonio Gonzalez, superintendent at the Fresnillo mine, says: The ITH hammer works better here. It s faster and more accurate. It s important not to have deviation when production drilling, and the ITH hammer ensures that we continue at the correct angle through the entire hole. September 2013

2 42 UNDERGROUND DRILLING Sandvik Cubex s Centaur drill rig, launched in 2012, has been re-branded as the Sandvik DU421 In April, Sandvik purchased the drilling-solutions business and operations of Cubex. There had been a global distribution agreement in place since 2009 between the two companies, which have worked together to increase unit sales and market penetration globally. The ITH products that Sandvik acquired from Cubex have more than 25 years of design behind them. A new ITH drill was released in 2012 called the Centaur under Cubex, it has now been re-branded as the DU421. Sandvik has recently been involved in reverse circulation (RC) drilling tests in North America, South Africa and Australia, and long-hole drilling for pre-conditioning in Australia. The company has also been working on a double-post mining (DPM) drill for single-pass 24in (61cm) drilling in Mexico (see Doubling down on page 59) In 2014, Sandvik will launch the maxi-hoist system. With a hoist capacity of 27,220kg, it will allow the drilling of shallow exploration RC holes to 500m and allow for pre-condition drilling applications past 250m in block-caving applications. It will also be used for deep underground freeze-hole drilling with Wassara water-powered ITH hammers in Canada. ITH drilling accuracy remains more consistent the longer the hole gets. So, when accuracy is paramount, ITH drilling is preferable Mincon s MC range of hammers and they are not subjected to the same high-energy drilling characteristics. In addition, top-hammer drilling produces significantly more noise than ITH drilling ( dB for top hammer versus 80dB for ITH). This can present issues for underground miners being exposed to unsafe levels of noise that can be very detrimental to hearing. Corcoran recommends that ITH drilling be considered when drilling sub-levels of 25m or greater, when bulk-mining underground stopes using hole sizes of mm in diameter, or when accuracy is paramount due to hole length and geology. Also, when production-drilling into broken/fractured ground, ITH flushing technology will be an asset and provide a lower cost of operation than top hammer. He says: With good drilling practice we can experience a 1 2% deviation over 100m. ITH drilling accuracy remains more consistent the longer the hole gets. So, when accuracy is paramount, ITH drilling is preferable. In certain mining applications ITH drilling can provide a lower total mine cost per tonne. ITH drilling may allow the mine to lengthen its production holes, which would then enable the reduction of sub-level development requirements. This would mean less development, ground support, basting and mucking, etc, reducing the cost of mining. The best ways to minimise deviation during drilling include proper time and care spent on setting up the holes, and angle indicators with on-screen displays are also important. More than 60% of deviation is due to incorrect set-up, for example if the drilling feed is pointed in the wrong direction. Operators pushing the feed system of the equipment can also be a problem, for example adding too much feed force or high rotation, as this typically reduces penetration time and accuracy. Drilling consumables Several OEMs make consumables for their own drills, which can often be used on competitor rigs as well. Corcoran says: One of the advantages of Sandvik producing the rig, hammer and bit is that we can fine-tune the application of the ITH hammer to the hole size with the tools and booster compressors. That means we can look at savings in power consumption by matching the output of the compressor to the hammer. When we can control the entire ITH drilling process, we can optimise each part of the drilling programme and provide our customers with a more efficient drilling programme. However, there are some advantages to using consumables from an independent company, rather than those produced by OEMs. With larger OEMs, rock drill tooling is generally one of many product lines offered and represents a very small percentage of their revenue, while independent companies tend to be specialists. Tom Purcell, sales & marketing director at Mincon, recommends: The most important criteria when selecting a tool are performance (drill speed), reliability and tool life. The combination of these three will ensure the lowest cost per metre for drilling operations. When choosing consumables for an ITH drill rig, companies should consider a number of factors. The job requirement is the most important in underground drilling, ITH hammers are commonly used for both exploration and production drilling applications. The diameter of the hole being drilled will determine the size of hammer required as well as drill-bit size. The ground conditions should also be taken into account. It is critical to match the appropriate input energy to the optimal operating parameters of the ITH hammer. This translates to selecting the appropriate ITH hammer model type to the specific air package on the drill rig. The hammer model chosen must correspond to the air flow and pressure settings of the on-board compressor on the drill rig. Mining Magazine spoke to three independent producers about their newest products and the mine sites where they have been used. Mincon In 2008, Mincon introduced its MC range of standard hammers. Since then the range has been filled out to include 3in (7.6cm), 4in (10.2cm), 5in (12.7cm), 6in (15.2cm) and 8in (20.3cm) hammers. Purcell says: The MC range includes a patented bit-retention system that allows for a fully supported bit in the chuck. This provides for a much sturdier shank design, greatly reducing the possibility of drill bit shanking. With more spline engagement than a traditional ITH bit, the amount of spline wear is greatly reduced when compared with other traditional drill bits. The Mincon MC hammers and bits are specifically built for applications where high penetration rates are important.

3 44 UNDERGROUND DRILLING Wassara waterpowered drilling in LKAB s mine in Kiruna, Sweden Rockmore has recently specialised its focus on DTH drilling tool solutions In 2012, Mincon began the launch of its next generation of reverse-circulation hammers, the MR range, including the MR120 and MR132 hammers and bits. Earlier this year the MR116 was added to complete this range of tools. Mincon states that performance tests showed up to 20% increase in production in both grade control and exploration applications versus some competitor tools. Purcell explains: The tools performed extremely well in deep-hole drilling in dry applications and where there is a lot of water in the borehole. With a variable length available on the chuck sleeve, the hammer can be easily set up for either dry- or wet-hole drilling. Rockmore International Rockmore has recently specialised its focus on DTH drilling-tool solutions. The company manufactures various DTH hammer models to suit specific compressor air packages. For example, the recent A series of DTH hammers offers a number of advantages and efficiencies for smaller compressor packages. Rockmore recently achieved a milestone in the DTH drilling market by delivering over 150 units Mincon and the Chilean miners of hammers during the last 12 months to the underground gold market in Nevada, US, which relies heavily on DTH systems for production and exploration drilling. Various models and sizes were delivered to the Nevada mines and drilling contractors during that time. Pejman Eghdami, executive vice-president at Rockmore International, says: Rockmore s SonicFlow design technology promotes hammer performance and raises energy efficiencies, so the benefits for the mines included faster penetration, longer service life, easier serviceability and better overall hammer performance, leading to lower drilling costs. Wassara Wassara recently launched the water-powered W200 hammer, suitable for hole sizes of 216mm and 254mm. Kent Boström, communications manager at LKAB Wassara, tells MM: It is the largest hammer available for water-powered drilling. Since Wassara hammers are water-powered, the need for a cost-effective re-circulation of the water is a top-priority R&D project. Wassara says that water-powered ITH achieves better hole accuracy than air-powered ITH, and that it can also maintain a high penetration rate even when water is encountered in the rock Mincon was involved in establishing the initial lifeline holes to the 33 miners who were trapped 701m below ground in the San José gold and copper mine outside Copiapo, Chile in August A 136mm-diameter hole was drilled through on August 22, 2010, using a Mincon MX5053 reverse-circulation hammer and drill bits. The lifeline hole established an important communication link and a conduit to pass food, water and medicines to the trapped miners for their long wait underground until they were finally brought to the surface. A number of holes had been drilled to try to locate the trapped miners, and finally Terraservice broke through with the Mincon hammer, 17 days after the mine collapse. When the hammer was retrieved from the bore hole, a note was attached to the hammer s drill bit that said: A Mincon MX5053 reverse-circulation hammer on display. The sign reads: Contact was made with the trapped miners using this tool, and a message attached by them to the drill bit was subsequently seen around the world, stating: The 33 of us are well in the shelter. This hammer reached the refuge a second time, allowing electricity, water and communications to reach the trapped miners. Estamos bien en el refugio los 33 The 33 of us are well in the shelter. Communications had been set up with the miners and food and water was being sent down to them. They were alive and well in a cramped 50m 2 shelter where they had survived by sharing tiny portions of canned fish stored in the shelter room. Two more lifeline holes were subsequently drilled with the Mincon MX5053 hammer, one by Adviser Drilling and the other by Geotech. One of these three lifeline holes was then used for the now famous plan B rescue that freed the 33 trapped miners on October 15, Purcell says: One of the main advantages of the Mincon MX5053 hammer versus competitive brands on this vital job was the ability to effectively drill at very deep depths where many other products cannot perform.

4 UNDERGROUND DRILLING 47 formation, which would lead to a loss of penetration rate in air-powered ITH drilling. The overall project cost is another advantage the technology can reduce the number of drifts needed by 70% and still generate eight times more ore per blast, as at the LKAB mines in Sweden. Boström says: We believe that Wassara represents a technological advance. Although it has been used in the LKAB mines since the beginning of the 1990s, the potential has not been fully appreciated by most of the mining world. Wassara says that its water-powered drilling system can be found on drill rigs from all major brands, as the drilling OEMs do not produce any water-powered drilling products themselves. Drilling simulators Training drill operators properly is very important, as poor drilling can have extensive safety and production implications. Correct drilling practice ultimately ensures that a mine achieves good-quality blasts and hence optimal ore extraction while maintaining a safe work environment. The best way to ensure this happens is a stringent, comprehensive training programme for all drill-rig operators, as well as all other vehicle operators and staff on the mine. Drill-rig crews are under constant pressure to maintain targets, explains Greg Lew, executive vice-president, global business development at ThoroughTec Simulation. A comprehensive training programme eases that pressure by producing competent drill-rig operators who create fewer accidents, who are more aware of their surroundings, operate their machines according to good practice and correct operating procedures, and are more efficient at operating their equipment. Simulator-based training has a number of advantages for operator training. The drill operators can train without the fear of damaging expensive equipment, and it frees up the equipment to be used for actual drilling. Wayde Salfinger, executive director marketing at Immersive Technologies, says: Rather than undergo training in the actual equipment, operators learn in a highly realistic simulator, allowing the transition to the real machine to be completed faster and with more confidence. A major benefit of simulator-based training is the ability to replicate emergency scenarios that cannot be trained for on the actual drill rig, either because of the danger to the operator or damage to the machine. Examples of this include an engine fire, hose damage or boom collision. Trainees can also be introduced to a wide variety of conditions, even those that might not be available for actual drill-rig training. Not only does this give trainees confidence in adverse conditions, but it also allows them to be trained in reacting to specific scenarios such as fissures behind the rock face, differing rock hardness and even or uneven rock faces. Instructors can also easily and quickly switch between drill bits if necessary. All of these scenarios can be simulated time and again, with no cost implications, until the correct operator response becomes second nature. Lew says: This obviously has long-term safety benefits to the mine, but simulator training also positively affects mine safety in the short term. By removing trainee operators from actual OEM machines until they are competent in drill rig operation, operating procedures and emergency procedures, simulators reduce the frequency and severity of training accidents. Lew says: Another feature unique to simulation is the ability the go behind the rock face and measure the angle of the hole drilled. This angle determines the effectiveness of the blast, but is obviously impossible to do on the actual rig. Measuring and recording these angles gives the operator and instructor valuable feedback, which in turn leads to more accurate drilling. Different regions and different mine sites vary in the amount of training hours that a drill-rig operator requires, and in the different criteria that need to be met before an operator can be declared competent. For example, rig operators in South Africa need a total of 150 hours of training; this is broken down into 30 hours of classroom teaching, 100 hours of on-the-job training and 20 hours of coaching. Of the on-the-job training, up to 80% (or 80 hours) can be performed on a simulator system, depending on in-house regulations. Training costs are greatly reduced by the reduced use of the actual drill rig. MM asked two leading simulator providers, Immersive Technologies and Thoroughtec, to talk us through their product offerings. Immersive Technologies Immersive Technologies has exclusive alliances with several major mining OEMs. Salfinger says: These OEMs provide Immersive Technologies access to proprietary technical information that allows unrivalled levels of simulation fidelity and accuracy. Immersive Technologies Conversion Kits are interchangeable equipment modules that fit onto base simulator platforms, allowing a range of different equipment to be simulated. Immersive launched such a kit for the Sandvik DD420 jumbo drill last year, which features realistic drilling physics coupled with a drilling assistant feature to maximise operator training effectiveness. The comprehensive recreation of the DD420 has a cabin that features tramming controls, drill and boom controls, jack controls, dials, gauges and a variety of the ancillary functions. The controls are all based on the fully hydraulic version of the machine, with the software supporting both closed-cab and open-cab arrangements. The simulator allows a range of specific jumbo-drill operator errors and events, with a focus on areas such as engine fires, hose damage and boom collision, low water pressure and hydraulic oil temperature. An operator using Immersive Technologies Sandvik DD420 jumbo drill simulator Training drill operators properly is very important, as poor drilling can have extensive safety and production implications September 2013

5 48 FEATURE UNDERGROUND NAME DRILLING ThoroughTec Simulation s CYBERMINE4 drill rig simulators feature a drillpattern editor Immersive Technologies SimControl software can monitor a range of specific operator errors and events, allowing greater operator efficiency to be obtained while monitoring and training for equipment damage and potentially life-threating emergency scenarios. Operator errors focus on areas such as hydraulics management, engine management, preventative maintenance, productivity, site safety procedures and situational awareness. Immersive also offers continuous improvement projects to drive operational improvement. Through close communications and a collaborative effort Drill More Bits Rods Couplings Shanks DTH with RockMore Wilsonville, Oregon USA Tel +1 (503) info@rockmore-intl.com Mining Construction Quarrying Tunneling Water-well R o c k M o r e International Rock Drilling Tools Judenburg, Austria Tel austria@rockmore-intl.com with mine site management, Immersive says that it can help to define mine business improvement and strategic objectives through a data-driven approach, including the customer s mine and equipment monitoring data. A targeted training programme is developed to reduce a mine site s cost and operational risks, leaving the mine site with a template and expertise for future continuous improvement projects. Immersive also offers training systems integration (TSI), which is a best-practice implementation programme that delivers training materials, and also institutes processes to co-ordinate and enable the training function. This allows training departments to understand and contribute towards achieving the mine-site and corporate objectives. Immersive s TSI team has delivered dozens of advanced equipment simulator implementations globally. ThoroughTec Simulation ThoroughTec Simulation s CYBERMINE4 drill-rig simulators feature a drill-pattern editor, which enables the instructor to create a custom drill pattern for each of the rock faces, as well as the optimum sequence for drilling. For novice operators, alignment guides assist in The company says the simulatortrained operators are on average achieving better results than the rig-based operators correct positioning of the drill boom. As a result, the trained operator is able to exercise correct drilling techniques for each scenario and rock type. Instructors are also able to monitor a trainee s yaw, pitch and drill depth for optimal drilling technique. CYBERMINE4 simulator training also caters for standardised, quantifiable evaluation of every training exercise. Trainee operators can be evaluated against a benchmark standard, against their previous training sessions, and against their peers. Operator evaluation is also against a set of predefined checks for the cab type and each is categorised into affecting one of health and safety, machine use or productivity enhancement. ThoroughTec recently evaluated drill-rig operators on the CYBERMINE4 simulator system at a Newmont Mining site in Nevada, US. The operators were required to drill a significant number of holes over a period of two days, and improvements in speed and accuracy were made by over 80% of operators. Gold Fields uses ThoroughTec s CYBERMINE4 drill-rig simulators at its South Deep mine in South Africa, and reports that it has experienced a significant reduction in the time taken to train an operator to full competency from three weeks on the vehicle to one week of simulation and five days on the actual vehicle. In addition, the company says that the simulator-trained operators are on average achieving better results than the rig-based operators, completing the training with higher proficiency levels. South Deep has also reduced its operating costs while training and production has improved since the introduction of the drill-rig simulator. ThoroughTec also recently completed the installation of a number of new drill-rig simulator systems around the world. Hindustan Zinc in India recently took delivery of a Sandvik DD320 drill-rig simulator as part of a larger order, as did Yamana Gold in Chile. In the US, a Sandvik DD420 dual-boom drill-rig simulator was recently installed at Newmont Elko. Murray & Roberts Cementation from South Africa has purchased a Sandvik DD320 drill-rig simulator, while Gold Fields South Deep mine will be taking delivery of extended functionality software for its Atlas Copco 282 rig simulator in the near future. Freeport McMoRan s Grasberg mine in Indonesia is another mine that will soon be commissioning a Sandvik DD420 drill-rig simulator.