Stopping a drill rig to change a bit always hampers productivity – but so does prolonged drilling with a worn-out bit. Rock-tool suppliers are attacking the problem from both ends by designing products that last longer in the hole while maintaining consistent performance.
By Russell A. Carter, Contributing Editor
In the current economic environment, rising costs are a universal concern throughout the mining industry. And, given that every stage of mining involves some type of drilling, a cost-control campaign wouldn’t be totally effective unless it includes a strategy for managing drilling consumables. Drilling is the costliest component of mineral exploration and is a significant factor in cost per ton of ore produced at active mines, representing a large chunk of the 35% or so of operating costs typically earmarked for replenishing a mine’s materials and supplies. And although the size, power and type of equipment can vary considerably among exploration, production and geotechnical drilling activities, the need for consumables – everything from bits, hammers and rods to fluids – is constant and, if recent financial results reports from the world’s top miners are any indication, those consumables will also be getting more expensive as global inflation rates continue their upward path.
This comes at a time when some of the world’s leading mining companies are signaling to make sizable increases in drilling activity for the near future. So, while drillers typically focus on what’s below the surface or behind a stope face, the near-term outlook for this sector is definitely upward and outwards, with the largest drilling services contractors reporting good prospects for continuation of positive trends – battery-metals demand is rising, gold reserves are shrinking and ore grades steadily dropping – that portend an increasing number of rigs turning in the field.
A quick look at recent financial results of the industry’s top three drilling services companies – Boart Longyear, Major Drilling and Foraco – supports this favorable outlook; at Major Drilling, for example, annual revenue is the highest it’s been since 2013, and fourth-quarter 2022 results show a quarterly increase of 48% over the same period last year. Major operates 603 rigs and spent almost $50 million last year to add 29 new drills and support equipment to its fleet, while getting rid of four of its oldest, most inefficient rigs.
Foraco, noting that drilling-services contracts typically ranged from three months to a year during the last mining downturn, said its current contract duration period now is between 1–3 years and major clients such as Rio Tinto and BHP are asking for options to extend ongoing contracts.
Boart Longyear reported its EBITDA grew during the first half of 2022, with both its drilling services and products business experiencing price and volume increases; however, the company, and others, also noted it had encountered higher input costs and supply chain difficulties.
All signs point to a growing number of rigs working around the world, and an accompanying expansion of consumables demand. At least one market survey predicts the global market for mining drill bits will reach $1.7 billion by 2026, growing at a CAGR of just over 5%. Leading drilling-consumables providers such as Epiroc, Sandvik, Mincon and others are leaning into the anticipated strong demand for their drillstring products by offering new products, techniques and services.
Maintaining Maximum Performance
During boom periods when drilling activity spikes, it’s not unheard of for drill crews to cut corners on technique and/or maintenance in order to maximize drill rates and results. However, there are a number of factors strongly favoring continued, close attention to bit condition. A 2019 study*, for example, showed that bits that are kept in use too long can have a drastic impact on efficiency. The study was aimed at analyzing the effects of overused (over-bored) top-hammer drilling bits with regard to various type of bit failure modes. More than 300 drill bit samples were visually inspected to determine if they had been over-bored, and if so, what the failure mode was; e.g., chipped or missing button, button sheared off at/below body level, cracked tungsten carbide, etc.
The authors reported that the incidence of chipped buttons or cracked tungsten carbide was far higher – at least 2.5 times – in over-bored bits. In terms of cost analysis and efficiency, the cost per meter (CPM) drilling with a bit that had 30% or less wear-flat area in relation to the original button diameter was almost half ($1.6 CPM) that of a bit with 75% wear flat area ($3.2 CPM) under the same drilling conditions. Annual operating cost analysis for normal vs. over-bored bits also showed relatively huge increases in per-meter cost as well, when using new or correctly ground bits vs. over-bored units.
As the study indicates, there’s no economic benefit in keeping a worn bit in the hole longer than necessary, but the flip side of the problem is that rigs need to keep turning as long as possible in order to maintain productivity. It’s a challenge that calls for innovation from suppliers to provide longer-life bits and other drilling consumables, and attention by drill crews to rotational speed, force/weight on bit, torque, penetration rate and other performance parameters to get the best service life and results from the bits they’re using.
Interviewed on the floor of the Bauma 2022 trade show held earlier this year, Martin Karlsson, Epiroc’s Vice President, Marketing, Rock Drilling Tools, commented on the industry’s need for improved bit longevity, noting that one of the biggest obstacles for improved drilling productivity is simply the need to stop the rig for a bit change.
He pointed to the company’s recent introduction of Powerbit X, designed initially for underground applications and promising the capability to significantly prolong replacement intervals which, in addition to improving productivity, would also enhance worker safety; fewer bit changes reduce the risk of slips, falls or back and hand injuries. Longer life also eases the need for time-consuming regrinding, as the company maintains that, by the time a Powerbit X bit is finally worn out, it’s ready for recycling, not re-use.
Consistency is another claimed benefit: A constant hole diameter is essential for optimal blasting. Traditional drill bits typically wear in a manner that reduces their diameter over time, leading to smaller and smaller holes. With Powerbit X, said Epiroc, the diamond-protected buttons keep their shape throughout the life of the bit.
Powerbit X, according to Epiroc, can help operations take advantage of the full potential of remotely and automatically controlled drilling by providing longer bit life that enables an operation to continue drilling – in auto mode – throughout lunch breaks, shift changes and blast ventilation cycles. The prospect of longer bit-changeout intervals, however, also brings with it the necessity for crews to be constantly aware of bit and overall drill-string status, both to maintain an acceptable drilling rate and to support the data collection and analysis tools that the industry is increasingly relying on to make operational decisions.
Recognizing this trend, Epiroc announced earlier this year that, in partnership with autonomous-solutions provider ASI Mining, it was introducing Mobius for Drills, a platform designed to convert data into useful, actionable information, and accordingly, help lead mines toward automation and connectivity. The system features embedded artificial intelligence and enables multi-vehicle command, control and monitoring.
Tyler Berens, Automation Director, Surface Mining, at Epiroc, said, “We think of [Mobius] as a tool to directly support making quick and effective interrelated decisions. Mines can get greater productivity and economies of scale as a single operator controls multiple remote and autonomous vehicles. Mobius for Drills is designed to tie the whole value chain together.”
According to Epiroc, Mobius for Drills displays data in an easy-to-use layout to map drill usage, evaluate statistics, track consumables and compare planned outcomes against actual results.
It is intended to serve as a single platform for all stakeholders within the drilling operation, allowing users to quickly navigate the information, filter it to their needs and streamline the decision-making process, day-to-day or over time.
Epiroc said the Mobius platform imports drill plans, monitors drilling and creates reports over a secure system on site or remotely. It supports manned operations, teleoperation, semi- and fully-autonomous modes and covers applications from drill and blast through autonomous haulage systems. An added value to Mobius for Drills, according to Epiroc, is its ability to work across fleets with drills from multiple manufacturers, condensing all sources of information. Mobius for Drills may be used as a Fleet Management System or integrated with a mine’s existing system.
The company also unveiled another product – its Automatic Bit Changer (ABC) for hands-free bit changes on Pit Viper 270 and Pit Viper 290 series drill rigs used in rotary drilling – which doesn’t qualify as a “consumable” itself but offers the capability to make safer and more efficient use of tricone bits. The ABC option, said Epiroc, is designed to change rotary tricone bits significantly faster than manual procedures and eliminates human interaction with the drill string, enabling workers to safely replace worn drill bits with a range of bit types and sizes from a safe distance without exposure to live work.
With the bit changer, operators can make or break joints, select drill bits, and add or remove them from the safety and comfort of a remote control room or the rig’s cab. The carousel design allows up to bits to be changed significantly faster and safer than a single manual exchange, and the removable carousel can store up to four tricone bits in different sizes and cutting structure for versatility on a drill site.
Extended wear life in automated drilling applications is also a featured highlight in the new Autobit line from Sandvik Mining and Rock Solutions. Sandvik said it’s their first drill bit designed specifically for automated longhole drilling, offering a longer initial interval before regrinding – more than twice that of standard bits – that can translate to several more hours of drilling every day. This is made possible, said Sandvik, by innovative bit design and the inclusion of Sandvik’s PowerCarbide inserts.
Autobit combines a strong gauge row, fully ballistic button profile and carved out front design, plus PowerCarbide SH70 grade inserts. PowerCarbide is a high-performance carbide technology that Sandvik introduced a few years ago and which now includes nine different grades (DP55, DP65, GC80, SH69, SH70, SH75, XT49, XT70 and XT90) to present a variety of wear and usage options. PowerCarbide SH70, developed for use in hard, competent ground, features homogeneous properties throughout the material and is self-hardening, becoming more wear resistant throughout bit life. According to Sandvik, Autobit’s design elements, when combined with the self-hardening carbide grade, can more than double grinding intervals when compared with a standard product.
Another newcomer to Sandvik’s mining drilling portfolio is its next-generation bit for rotary applications – the Charger RR450 – which also features PowerCarbide inserts as well as new cone steel protection, computer optimized cutting structures and a patented sealed journal bearing system. Testing shows that bit life can be increased by up to 90% while maintaining consistently high penetration rates, according to Sandvik.
Carsten Mijic, Product Manager for Rotary Bits at Sandvik Mining and Rock Solutions, said “We can now offer our customers nearly double the bit life compared to other premium sealed bearing bits. This can translate into hundreds of thousands of dollars saved, while at the same time reducing the need for operator interactions with the bit and drill deck.”
“[In 2021] we introduced the PowerCarbide SH75 grade to our rotary drill bit offering with the launch of the Sandvik RR240 air bearing bit range,” said Mijic. “It performs incredibly well, and we are pleased to be able to now include it in our ultra-premium sealed bearing bit offering.”
Sandvik said the Charger RR450 bit would initially be available in sizes ranging from 9 in. to 12 1/4 in. with additional sizes to come.
After introducing its Rbit series of larger-diameter button bits in early 2021, Robit recently announced that it has filled out the bit line by adding smaller 32-mm to 57-mm versions for drifting and tunneling applications. Designed to help Robit’s customers reduce total drilling costs by achieving faster rate of penetration and the lowest cost-per-meter, the principal features of the Rbit line include an optimized button layout configuration to ensure maximum rock contact and energy transmission; optimized placement of flushing holes to provide improved flushing and even improved rate of penetration (ROP); and redesigned wider flushing grooves that deliver better flow for cuttings.
Sandvik’s new Tundo RH650 DTH hammer is claimed to be capable of reducing fuel consumption by up to 15% while increasing penetration rates by up to 20%. The hammer’s design features a new efficient air cycle, eliminates the foot valve and is smaller and lighter compared to other hammers in its class. Flushing is done through the splines. A more efficient air cycle means that the new hammer can be used on smaller class drill rigs, delivering fuel savings and efficiency benefits, according to the company.
Edgar Halling, Product Manager, DTH Hammers at Sandvik, explained that “For a customer using a six-inch DTH rig with a conventional hammer, the transition to Tundo RH650 could increase annual drilling productivity by 32,000 meters. Customers choosing to use a five-inch rig would enjoy significant investment cost savings and reduce fuel consumption by up to 71,000 liters per year while reducing CO2 emissions by about 185 metric tons.”
In October, Mincon Group plc unveiled its next-generation DTH hammer range that will be available starting in 2023. The MP-Series product range is centered around high-efficiency DTH hammers that combine superior penetration rates with energy savings. The line begins with the MP30, a 3-in.-class hammer that can be equipped with drill bits between 85 mm and 105 mm, and tops out with the MP400, a 40-in.-class hammer for large-diameter drill bits between 1,000 mm and 1,524 mm.
Simpler, Speedier Tube System
Epiroc now offers a new tube drilling system, labeled ET51 and designed to replace the previous T51 system. The new system is claimed to significantly outperform traditional speed-rod systems and allow for straighter and deeper drilling. Unlike its predecessor, ET51 comes with only one tube type which simplifies procurement and management.
According to Epiroc, the ET51 system’s improved capability for extremely straight drilling is the result of a new tube design, a stiffer drill string thanks to the shoulder drive, a new coupling geometry and greatly improved bending endurance resulting in up to twice the strength of the T51. Lighter tube ends, which also have an improved geometry, allow more energy to be transferred into the rock. The advantage increases with each tube in the drill string, reducing the rate of penetration loss per tube, adding up to considerably deeper holes. Additionally, besides improving straightness, shoulder drive reduces tube wear. The new optimized coupling geometry, including patented threads, means less mechanical wear.