Feature: Rock drilling

The latest generation of drill rigs and bits feature evolutionary technology designed to help contractors increase productivity, reduce operating costs and downtime and do so in a safer environment.

Global product manager at Boart Longyear, Craig Mayman told CE, "Productivity and safety continue to be the definitive factors in well designed drilling equipment. That said, rigs designed for maximum productivity also have to suit site and application requirements such as accuracy and manoeuvrability."

The latest launch from Boart Longyear, in the shape of the DB95GT, is a rig designed for geothermal applications that is capable of handling several drilling methods and multiple site conditions at efficient drill speeds.

"Versatility is a key consideration. Customers are increasingly looking for drills that can handle several different drilling methods for work across a variety of applications and ground formations. As well as being multipurpose, construction drilling often requires drills to be portable and compact without sacrificing power," he said.

The DB95GT features a pullback capacity of 9,8 tonnes and a torque rating of up to 24 kN on its mast making it ideal across a spectrum of ground formations. Highly efficient hydraulics boost performance by delivering more power to the rotary head, yet the rig's compact size aids manoeuvrability in confined spaces.

The new Sandvik DI550 down-the-hole (DTH) drill rig has been designed to balance power with hammer size to offer high productivity while keeping fuel consumption and operating costs to a minimum. A spokesperson said, "Small and medium size quarries and contractors in particular have to continuously improve productivity in their operations. The selection of the right machine for the job is therefore of the utmost importance."

The DI550 is powered by a 324 kW diesel engine and features 24,4 m³/min of compressor air at 24 bar, making it a perfect match for the company's 5'' (127 mm) DTH hammer.

"Aside from high performance, the focus when designing the DI550 was on simple and comfortable machine operation. We set out to design a rig that enables seamless cooperation between man and machine," said the spokesperson.

The DI550's cab is fitted with a roll over protective structure (ROPS) and a falling object protective structure (FOPS) and the large windscreen, for enhanced visibility, is fitted with a strong safety bar that is easy to open for cleaning.

All daily maintenance points are located at ground level to simplify the process and improve the safety of service personnel, while a fast fuel filling option and large tank combine to reduce downtime.

Atlas Copco has combined the best of its ROC L8 DTH drill rig with the advanced automation and control found in its SmartRig family to produce a new, highly productive SmartRig ROC D65s.

Fitted with Atlas Copco's Rig Control System (RCS), the SmartRig ROC D65s is designed for drilling in the 110 - 203 mm hole range. Using Secoroc COP 44, 54 or 64 DTH hammers to a maximum depth of 54 m, drilling power is provided by an on-board mounted compressor supplying 30 bar pressure. The rig itself is powered by a 402 kW Caterpillar C15 diesel engine.

Product manager of automation for surface drilling equipment, Olav Kvist said, "RCS controls the entire handling of the drill rig, including the drilling cycle and automatic tube handling. The system also enables the transfer of planning and performance data between the rig and the site office.

"The capabilities of the ROC L8 and SmartRig have now been brought together in a single rig that offers a completely new drilling experience. This is the future of small hole drilling in open pit mining operations," he said.

A key feature of the SmartRig ROC D65s is that it can automatically add and retract drill tubes, which frees operator time to prepare materials on the bench while the rig completes the hole by itself.

A similar concept can be found with Boart Longyear's DB95GT on which the rod management system is made up of a removable rod rack, a pivoting main winch, magnetic rod lift and rod alignment arm for safe and efficient operation.

Following over 12 months of 'live testing' FRD unveiled its DCR 20 DTH drill rig at the Bauma exhibition. Capable of drilling in the 89 - 165 mm hole range to a depth of 40 m, the new rig weighs 21 tonnes and is powered by a 328 kW Caterpillar diesel engine. An Airman high pressure compressor discharging 24 m³ at 25 bar powers the drilling.

A spokesperson said, "The DCR 20 is a compact design offering high performance and maximum safety."

Compact dimensions and versatility describe Atlas Copco's new ROC T20 four-wheel hydraulic drill rig designed for hole diameters from 38 mm to 64 mm. Suited to urban drilling applications, the ROC T20 is powered by an 82 kW Cummins diesel engine, while drilling is powered by a compressor producing up to 50 litres/second.

The ROC T20 features an advanced rock drill control system that controls drilling performance through rotation pressure. The system also features an anti-jamming function that continually monitors the drill bit to help prevent the drill string being jammed or lost in the hole.

Bit part

Versatility, penetration rates, straighter holes and lower energy consumption are not the sole preserve of drill rigs. All are influenced by the drill bits themselves and to this end Sandvik launched its RT300-Uniface range of threaded button-bits earlier this year.

"As the leading component in the production chain, the drill bit plays a vital role in project advancement and must therefore be chosen carefully. Today this is hindered by a bewildering array of drill bits, which makes it hard to choose the right one and also leads to 'tailored' drill bits having to be changed whenever rock conditions alter," said spokesman Andres Nyström.

In its new range, Sandvik has consolidated more features into fewer drill-bit models in order to widen each bit's range of application. This has been achieved, in part, through the adoption of XT48, a new harder and tougher grade of cemented-carbide for the button bits.

The range features just three bit-face designs for drills of between 51 - 64 mm, 70 - 96 mm and 102 - 152 mm. "The bit design combines the diverse features that would previously have been found in two or more different models," said Mr Nyström.

"The guidelines for choosing the right Sandvik RT300-Uniface bit are simple. Spherical buttons for very hard rocks, ballistic buttons for less hard rock, regular bit-skirt for solid homogenous formations and retrac skirt with a stepped splein for best possible hole straightness in situations of mixed, jointed or fractured formations. Through these bits the changeover boundaries are much less strict," he said.

Boart Longyear also launched a new line of Surface Set XP drill bits earlier this year, including 11 configurations designed to give deeper penetration. The company says the new bits last up to three times longer than conventional surface-set bits and eliminate the need to use alternative bits when drilling in inconsistent ground formations.

"Our goal was to redefine the surface-set category and set a new benchmark for productivity in soft and sedimentary applications," said Monika Portman, product manager for coring products.

The new bits feature an impregnated crown with multiple layers of diamonds for an increased lifespan. "The Ultramatrix crown holds large, synthetic diamonds in place as it continues to cut, compared to traditional surface-set bits that used only a single layer of diamonds," said Ms Portman.

"With better, more sustained penetration rates, drilling contractors can achieve a cost per metre advantage," she said.

Electric dreams

While evolutionary designs shape the newest drilling rigs, further advances in electronics could well shape the next generation. As Mr Mayman told CE, "Electronics offer the scope to better control drilling parameters, as well as managing and monitoring overall rig performance. Strategic use of electronics could also increase operator safety and effectiveness by removing them from the immediate drilling area. I think this will be a key point moving forwards," he said.