Smarter Bolters May Help Level the Field

The latest bolter solution releases feature technologies that will improve job safety, satisfaction and even opportunities

by jesse morton, technical writer

Recent innovation in the roof bolter space has taken a path similar to that taken in others. Automation and machine monitoring capabilities are increasingly available, and the benefits are numerous. Those benefits include increased safety and control, which is helping to change the underground worksite, and perhaps even society, for the better.

Smart Bolter Offers Data, Efficiency

The Joy Smart Bolter on the 12CM miner bolter gives actionable insights, performance monitoring, automated controls, improved uptime, and increased efficiency and productivity, Komatsu said. “Our customers desire to maximize productivity, and we can support that by providing high-value data and analytics,” said Jez Leeming, product director, entry development, Komatsu.

The electrohydraulic smart roofbolter features automatic drilling and bolting cycles that can be initiated from the push-button control station. It has adaptive drilling, anti-stall and damage prevention functionalities.

The bolter is now offered integrated to 12CM miner bolter models. For mid- to high-seam applications, the line employs Komatsu’s multi-motor concept. Individual motors with direct-drive transmissions power the cutter, traction, gathering and hydraulic systems. “This permits service or repair quickly and easily, reducing downtime and costs,” the company reported.

Options include the Wethead cutterhead, onboard dust scrubbers, Smartconveyor, Smartzone Proximity System, the Faceboss control platform and high-voltage capability.

Built on to the miner, the Smart Bolter generates valuable data to drive decision making. “Real-time high-speed data streams every 35 milliseconds and can be viewed live or stored on a server for access, and includes information like feed position, feed speed, water flow rates, water pressure, cycle status and home position,” Leeming said.

It also generates data on oil flows and pressures, drill feed position and current bolter function. “This real-time data enables real-time drill status and input/output data available to monitor overall performance and functionality in detail,” he said.

The data can also be used to solve problems and to plan maintenance.

“To maximize uptime, real-time fault monitoring and data logs with onboard intelligence facilitates efficient problem resolution,” Leeming said. The monitoring and logs can be used to determine maintenance requirements.

The bolter features automation that helps improve efficiency. “Pre-set bolting support requirements can be loaded into the machine parameters, allowing the operator simple push-button initiation of auto-drilling and auto-bolting functionality for roof bolts, as well as extension drills for most different types of cable bolts,” he said.

The drilling functionality uses auto-control and monitoring of oil pressure and water-flushing pressure to maximize drilling speed through various strata types.

“The water-flow and pressure monitoring reduces and eliminates drill-steel blockage as the roof bolter can back off the feed if water pressure shows the drill steel is becoming blocked,” Leeming said. “Feed-pressure monitoring affords variable drilling in different strata to reduce drill stall and drill buckling during collaring of the hole.”

Integrating the smart bolter to the continuous miner answered specific customer needs, Leeming said. “Komatsu’s legacy as an innovation leader stems from a persistent, shared belief that collaborative partnerships are the best way to meet the ever-changing needs of our customers, solving tough job-site challenges and creating lasting value.”

Indexing Bolting Module Improves Safety, Control

J.H. Fletcher & Co. reported sales of the upgraded HDDR roof bolter in South Africa. The bolter can include a new indexing bolting module with “groundbreaking design elements” that improve the safety and the operation of the rig, the supplier reported. It also speaks to an initiative in that country to bring more women into the mining workforce.

“The module surely will improve ergonomics and reduce fatigue for women in mining, which is very important to our government,” Francois Meintjes, international sales manager, J.H. Fletcher. “The indexing bolting and drilling module on the HDDR eliminates the need to frequently handle drill steel to help improve operator safety.”

Each mast on the dual-head roof bolter is equipped with individual crowds. One mast is for drilling and inserting resin. The other installs the bolt. “The indexing mast design eliminates the need to stow and manipulate the drill steel,” the supplier reported in a white paper.

The drill steel uses the same roof reference guide as the resin inserter. “This reduces the potential for misalignment,” J.H. Fletcher reported.

The operator compartment has advanced hydraulic controls, including an automatic drill and platform leveling system. “The controls reduce the physical effort required of the operator,” the report stated.

A latched drilling system allows for hands-off drilling. The operator starts drilling, and then latches the controls. “A hydraulic latch circuit was developed to maintain operator safety and compliance,” the com-
pany reported.

To use it, the hole must be collared, the drill steel must be in the chuck. “Without feed and rotation pressure, the latched drilling circuit cannot be engaged,” J.H. Fletcher reported. “This ensures that the drill must be in material and not free air to operate.”

To activate the system, the operator pushes on the feed-and-rotation joystick with one hand, and then pushes the latched drilling handle with the other, the company reported. The drill steel then continues upward as far as it can go or until the operator stops it.

A laser curtain system creates an invisible barrier between the operator and the steel that when breached stops rotation. It helps prevent the operator from accidentally touching the rotating steel.

A hydraulic stinger helps stabilize the mesh against the roof. “Combined with a mesh-handling system on the TRS, it decreases the amount of manual labor required by having the bolter carry and lift the mesh,” the report stated.

An automated temporary roof support (ATRS) and the operator canopy provide superior protection against rock falls. “Fletcher’s ATRS is an advanced system that sets against the roof as a temporary support during the bolting process, to help stabilize the roof in the active working area,” the company reported. “MSHA-rated canopies are placed over the tramming and bolting stations of the machine.”

As a safety feature, the drill steel is supported at the top with a guide bushing, eliminating the need for a hydraulic guide. “Combined with Slow Rotation Retract Circuit,” the Fixed-in-Position steel “allows for a safer, more secure movement of the drill head while drilling,” J.H. Fletcher reported.

When the steel is lowered, some of the rotation oils goes back into the tank to slow the rotation. “Once the drill head is in an extended direction, the rotation speed returns to normal,” the report stated.

A pneumatic resin injection valve eliminates the need for the operator to insert the resin by hand.

The Resin Timer Circuit and the Anti-Jam valve package helps improve bolt installation performance. The operator can use the circuit after the bolt is fed through the resin. “The bolt head will automatically spin and mix the resin for a preset time, hold, and subsequently torque the bolt nut to a preset value,” J.H. Fletcher reported.

The Anti-Jam valve uses a pressure-feedback system to give the maximum required feed and rotation speed and pressure. “The valve package will adjust feed and rotation settings depending on roof strata hardness, helping prevent rotation stall and excessive feed force,” the supplier reported.

Since the release of the new indexing bolt module for the HDDR bolter, the supplier has seen growing interest from miners in South Africa, Meintjes said.

“Customers have been very enthusiastic,” he said. The machines are built to meet the individual needs of customers. “We draw from our years of experience in various mining markets, such as coal, hard rock and industrial minerals, to customize our equipment and optimize it for each particular customer.”

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Self-drilling Hollow Bolts, Grouts Offer Savings

JENNMAR reported its injectable bolting systems and grout offerings are field-proven, safe, efficient and cost effective.

“They are a problem-solving suite of tools that can be tailored to mine-specific applications,” said Benjamin Mirabile, vice president, JENNMAR Engineering. “The systems typically involve some type of bolt and chemical grout that can provide bolt anchorage, consolidate strata, and mitigate water influx, or all of the above.”

The more commonly used bolts are the Fully-Grouted Non-Tensioned (FGNT) cable bolts and self-drilling hollow-core bolts. Exemplary grouts include the US Grout, the TDS-240 and the J-PLUG Acrylate Grout.

FGNT cable bolts are for supplemental roof support, strata consolidation or water control. “These areas include longwall headgates, longwall setup faces, low-cover stream valley crossings and longwall recovery chutes,” Mirabile said.

The bolts are initially installed for supplemental support the same way that standard cable-bearing bolts are installed. Then, later, when strata consolidation is needed during longwall retreat, the bolts can be injected with grout or other consolidating chemicals without impacting the longwall operation.

“The system integrates well into the mining cycle and allows for injection of grout long after the bolt has been installed and the mining section has advanced,” Mirabile said. “And the support capacity and performance of the FGNT system is equivalent to standard cables, even without post-grouting.”

By doing double duty as supplemental bolts and injection points for strata consolidation or water control, the cables offer cost benefits and efficiency savings.

“This system reduces the overall quantity of grout required by increasing the stiffness of the cables that, in turn, reduces roof movement and fracturing,” Mirabile said. “This reduction in roof movement then leads to a reduction in the volume of grout required to make a safe and competent roof beam.”

The system was originally designed to be a simple post-grouted cable that could resist corrosion and have a functional lifespan greater than a decade. It was co-developed with a major coal customer.

“During the course of development and testing, it was found that grout pumped into the cable bolt could migrate into surround strata much like the function of an inflatable packer commonly used for strata consolidation,” Mirabile said.

“Thus it was a natural progression to use the cable as a best-of-both-worlds approach in areas where supplemental support was commonly needed,” he said. “An added benefit of the system was a cost advantage compared to a separate bolt, inflatable packer and grout.”

Self-drilling hollow-core bolt technology was originally co-developed with a hard rock customer who had soft ground conditions and was having to redrill holes multiple times to install a bolt. “Often, the drill hole would collapse when the drill steel was retracted to insert grout,” Mirabile said.

The hollow bolts have a sacrificial bit tip, and are drilled directly into the rock. They can then be grouted without having to be retracted. “This system virtually eliminates the need to re-drill bolt holes due to hole collapse,” he said.

The system has proven to be “a real problem-solver” in several applications for coal customers, Mirabile said. “The system has proven effective for special applications in coal, particularly in very weak or consolidated conditions,” he said. “It has been used for highwall stabilization, and for engineered seal bottoms.”

Both systems are compatible with standard 70-lb/ft³ Polyurethane (PUR 70) grout. JENNCHEM has developed a line of grouts that better speak to mine-specific needs, Mirabile said. “We can tailor the grout selection to address water control, migration requirements and strength.”

For instance, US Grout does not react to water that may be encountered in mine strata, he said. “In wet conditions, US Grout tends to maintain its strength and migration properties and has been proven an effective product for water control.”

Contrast that with standard PUR 70, which “tends to foam when it hits water,” he said. “This leads to a decrease in strength and grout migration.”

For highly fractured, broken strata, TDS-240 Urea Silicate Resin is a high-viscosity grout that does not tend to migrate from the drill hole, and provides optimal anchorage, Mirabile said. “In applications where strata consolidation and grout migration is a secondary concern to bolt anchorage, TDS-240 is the grout of choice since it tends to stay in the borehole where it is needed.”

When extensive grout migration is needed, the low-viscosity J-PLUG Acrylate can flow through “the smallest spaces in strata,” he said.

“Further, the reaction time of J-PLUG is nearly infinitely adjustable at the point of installation,” Mirabile said. “Thus, set times can be tailored to the migration distance desired.”

The systems integrate easily with existing solutions and processes, he said. “In most cases, the only new infrastructure the customer has to provide is air or hydraulic power for the grout pumps.”