By Steve Fiscor, Editor-in-Chief

The mind set underground has steadily changed from installing the most bolts to installing as many bolts as possible while doing so safely and cost effectively. But, increased productivity means more bolts installed per shift. Fortunately, equipment improvements for roof bolting machines have evolved with technology over time. Today’s bolting machines are more powerful and maneuverable. Through improvements in hydraulics and controls, the machines now have the ability to drill holes faster than they did only five years ago. In some cases, miners can expect push-button functionality.

Improved productivity also translates into an increase in interaction between the miners and the equipment, which explains why many of the improvements have revolved around ergonomics and operator safety as far as machine positioning, dust control, noise, etc. After all, common sense would lead one to believe that a safer, more comfortable operator will install more bolts.

Bucyrus Offers a Safe, Productive Line of Roof Bolters
Bucyrus offers three different roof bolter models for various mining conditions. The LRB-15AR is a single-arm bolter recommended for ranges of 32 inches and above; the dual-arm RB2-52A for ranges of 42 inches and above; and the dual-arm RB2-88A for ranges of 54 inches and above.

The product lines formerly held by DBT, which included Long-Airdox and Simmons Rand machines, have been consolidated into three units that cover the entire range of seam heights, explained Keith Alley, market development manager for the room-and-pillar division of Bucyrus. “We support some of the legacy products that came through acquisition,” Alley said. “We keep these three models current with the latest technology, especially in the area of hydraulics and control systems. We also make sure that they comply with all of the recommendations and requirements from MSHA, such as dust sampling, noise levels, etc.”

According to the company, many of its customers prefer Bucyrus roof bolters because they have the ability to get to any space thanks to their compact and/or articulated chassis frames. “They get the job done quickly and efficiently while maintaining excellent availability and minimizing operating cost per ton,” said Alley. “Another advantage of Bucyrus’ RB2 dual-arm models is that they feature articulated steering which means lower tire usage compared to models using skid steer.

“The articulation point between the front and rear sections improves the machines’ maneuverability,” Alley said. “It allows them to get close to the rib. These bolters can make the turns into and out of the crosscuts easier, when compared to the rigid frame system where an operator might have to make a three-point turn. The Bucyrus bolter can turn within its length.”

The LRB-15AR is a rigid-frame, single-arm skid steer machine with an Automated Temporary Roof Support (ATRS) integrated into the boom.  It has a 40-hp electric motor with a two-stage gear pump. When equipped with 26-inch tires, it provides 6 inches of ground clearance, 32 inches of tramming height and a 76-inch ATRS reach. It complies with MSHA ATRS load certification with a capacity of 11,250 lb, and features a 50-inch drill boom feed and 7,000 lb of drill feed thrust. The drill pot speed is able to be operated anywhere from 0-480 rpm.

Bucyrus dual-arm roof bolters feature hydraulically operated drill and boom functions, hydraulically driven planetary wheel motors with a free-wheeling feature, ATRS, a 75-hp electric motor and four-stage gear pump, a vacuum blower driven dust collection system and fail-safe parking brakes. Features unique to the Bucyrus RB2 series include a four-wheel independent planetary drive and a horizontally and vertically articulated chassis frame which steers the machine and allows it to maneuver through vertical swells while helping to maintain traction by keeping all four tires on the ground. This feature also allows the user to position the machine for faster crosscut bolting.

“The four-wheel independent planetary drives on the wheel ends are powered by hydraulic motors,” said Jamie Whitlow, product engineer-roof bolters, Bucyrus. “The machines essentially have four-wheel drive and the ones with the articulated frames can keep all four wheels on the ground. These bolters will have a better ability to tram through muddy bottom conditions.”

The RB2-52A meets MSHA ATRS load certification requirements,  and features a 52-inch drill boom feed, 10,000 lb of drill feed thrust and a drill pot that can be operated at anywhere from 0-614 rpm. When equipped with 32-inch tires, it provides 8 inches of ground clearance, 37 inches of tramming height, and a 96-inch ATRS reach.

The RB2-88A, when equipped with 35-inch tires, provides the most ground clearance of the Bucyrus roof bolters, giving a total of 9.5 inches of ground clearance, 48 inches of tramming height, and a 120-inch ATRS reach. ATRS load certification is 33,750 lb.  This model has an 88-inch drill boom feed, 10,000 lb of drill feed thrust, and a drill pot that is able to be operated at any speed between 0 and 614 rpm.

Roof Bolting Technology at Joy
According to Brian Thompson, business manager-development mining systems for Joy Mining Machinery, Joy has seen several changes in bolting products over the past few years. “Some of the biggest surround the rigs and controls themselves,” Thompson said. “While the company manufactures and ships many mobile bolting products such as Multibolters, Quadbolters, Ramtraks, and Miner-Bolters, the core bolting components are common. Drill feeds, rotation units and control systems have seen the biggest change in the past few years.”

Through the acquisition of Cram, Joy patented and pioneered the HFX drill feed in 1996. “Since that time we have shipped more than 1,000 rigs into the field,” said Thompson. “More recently we have added the AFX product line to our range. The AFX allows for the next level of rig automation while providing increasing feed thrust by 50% over the HFX.”

Rotation units, according to Thompson, have also undergone several step changes. With the release of Joy’s Two Speed Rotation Unit (TSRU), the company claims customers can increase productivity in more difficult applications. TSRU provides 20% increase in drilling speed, 25% increase in torque, while requiring 33% less hydraulic power.

“Bolter controls are migrating toward electro-hydraulic controls, which provide push-button functionality and a more practical human interface,” Thompson said. “The end-goal is full automation and the removal or limitation of human interaction.”

Thompson believes that the improvements were motivated by Joy’s Center of Technical Excellence for bolting equipment in Australia. “As you survey the relevant markets today you’ll note varying degrees of customer expectation and national regulation,” Thompson said. “Australia continues to lead those markets through safety focused requirements. Therefore, many new concepts and human interface develop from the local market.”

Joy is committed to “Zero Harm, Increased Productivity, and Lowest Lifecycle Cost.” “To achieve this, we must keep focus on both safety and production,” Thompson said

Technology has provided an evolutionary path to improvement, according to Thompson. “Smaller, smarter valving along with integrated fluid logic circuits produce more reliable and user friendly products,” Thompson said. “Productivity increases as the package size is reduced. Removal of additional hoses and potential leak points add to the increase in productive time.”

Increased productivity means more bolts installed per hour. Therefore, there is an increase in human interaction with equipment making ergonomics critical. “We have worked directly with customers to address human interface areas and drive improvements in multiple areas,” Thompson said. “From the design of top plates that position and guide drill steels, the position of rotation units in relation to rig controls, completely through to full automation and complete removal of the interface, all have been addressed.”

The future for roof bolting, according Thompson, is full automation and reducing the human interface with the machine. “Giving the operator the ability to load standard consumables or self drilling bolt technology, set the rig in place and let it do the work is our goal,” Thompson said. “The future is not to far away as we see it. Some exciting developments are underway to make this a reality within the next 12 months.”