Seize the Opportunity to Upgrade

A continuous miner rebuild offers the chance to adopt new techniques that can yield big benefits

by jesse morton, technical writer

The continuous miners repair and rebuild space is seeing brisk business these days. Beyond booking overdue work, customers are increasingly interested in upgrades, suppliers said. Those upgrades can offer much-needed gains in efficiency, safety and production. Oftentimes, the result is a customized machine with capabilities specific to the mine and the vigor to beat its old performance records.

Updated Controls Enable Automation

Komatsu reported strong demand for its rebuild program offerings, and that program customers increasingly add on machine monitoring, automation and safety solutions.

“The life cycle management (LCM) program will be extended for another five years, adding 16 continuous miner rebuilds,” said Dan Spears, vice president, sales and service, soft rock.

A major repair or rebuild is a great opportunity to upgrade, he said. For example, one recent program customer “wanted to try a new wider web cutter gearcase,” Spears said. “It is now producing good results and helping promote a longer life for the gearcase.”

Or the opportunity is to trial advanced telemetric solutions. “Customers can incorporate other services to our LCM packages, such as remote machine monitoring, which provides timely machine health and performance information to help increase asset utilization, efficiency and productivity,” he said.

“We’re also upgrading the control platforms on all the miners to Faceboss 2.0,” Spears said. “This new platform helps the operator manage and control the machine from a remote location to increase productivity and reduce operator exposure to harm.”

FaceBoss 2.0 is an advanced automation platform that gives short-range remote control capabilities and features an updated, ergonomic handheld controller, improved data integration, and a 50% faster start time over the previous version. It offers the ability to store historical data and to do high-speed sampling.

Compared to the previous version, FaceBoss 2.0 offers improved diagnostics and troubleshooting via wireless two-way communications between the machine and the handheld controller. “Base diagnostics can be displayed on the two-way remote control unit,” Komatsu said.

The new remote also allows “the operator to maneuver the equipment from a safer distance,” Komatsu said. “Being farther away results from the desire to remove operators from the working face, placing them ‘around the corner’ in a location from which the machine can be remotely controlled.”

To further ensure operator safety, Komatsu offers the Joy SmartZone Personal Proximity Detection (PPD) system for continuous miners, which can be adopted with a rebuild or repair. “This system helps detect workers in low visibility and obscured operator line-of-sight locations,” Spears said. “By helping reduce accidents and collisions, we’ve reported an increase in machine availability with our system installed.”

PPD uses active radio frequency transceivers and advanced algorithms to track and monitor personnel movements in real time. Originally developed for longwalls, the system can be configured to create zone-based alarms and triggers that pause automation.

The LCM partnership offerings gives customers the option to subscribe to different levels of rebuild and repair services.

“To help control costs, this tiered program gives our customers the ability to select the level of repair based on the level that best matches their budgetary and time constraints,” Spears said.

In an LCM partnership, the miner and Komatsu collaborate on certain strategic goals. Based on the level of the partnership and the goals, Komatsu can track data, supply parts, consult on planning, and rebuild machines on a schedule that adds the most value.

“The demand for rebuilding continuous miners is increasing, and with this program, our LCM customers are able to secure available production slots in a very tight market,” Spears said.

Komatsu also offers the Machine Exchange Program (MEP), a rebuild partnership agreement offering. In the typical MEP partnership, Komatsu tracks tonnage data on Joy machines, and, when the time comes, exchanges new or rebuilt machines for old ones.

“For our non-LCM, non-MEP customers who are looking for more select repairs on their miner rebuilds, we tailor the scopes of their repairs
to meet their needs through our tiered component repair program,” Spears said.

The repair-and-return service contract tiers are Prime, Select and Base. In a Base contract, the repairs are per request and come with expert advice on possible future services. A Select rebuild improves the machine to add life between rebuilds. A Prime rebuild gives maximum equipment life at the lowest cost per ton and comes with a warranty, which can be extended based on consumable usage.

AC Motor, Drives Offer Safety Gains

Saminco reported strong demand for drives and motors for new builds, rebuilds and upgrades.

“We are starting to see mines willing to invest back in equipment,” said Barbara Rippy, marketing director. “That has been good for us.”

For continuous miners, the supplier makes two variable frequency drives, the JD400 and the JR1000. Saminco also makes the TM1200, a water-cooled motor.

The company’s flagship offering for continuous miners, the JR1000 VFD System, includes the 1,000-volt AC JR1000, the motor, and an optional radio remote control. “Saminco’s cool-torque motor, when paired with the JR1000 inverter, consumes significantly less current for the same amount of torque compared to competitive products,” the company said.

The motor replaces existing DC motors with the same motor mountings. Purpose-designed to run cool, it “uses a liquid cooling of the entire enclosure,” said Kenny Boles, vice president, sales and services. The motor “is virtually maintenance free.”

Many customers “go an entire 3- to 5-year rebuild cycle without touching the motor,” he said. “When you get away from DC motors, you get away from DC motor repair and maintenance.”

The motor has a copper-barred rotor. “A lot of the competition uses an aluminum-barred rotor,” he said.

“The efficiency is so much better with the copper-barred rotor,” Boles said. “We’re among the only people that do that.”

The JR1000 drive system “provides inverter control for left and right traction, along with an auxiliary output for either a pump, scrubber fan, or an auxiliary fan,” he said.

The system is “able to achieve peak torque of 1,375 Nm at 87 Amps,” the company said. Supply voltage ranges are 850 to 1,260 V, and at 50 and 60 Hz.

“Rectification occurs inside the module,” Boles said. “So there is no need for a stand-alone rectifier.”

Internal overload protection “means there is no need for the old mechanical overload protections to be mounted,” he said.

The system has three set speeds, but “can also be operated at infinitely variable speeds down to 0,” the company said.

“During heavy cutting conditions it will reduce sumping speed all the way down to almost 0 tram speed so that the cutting will occur at below the rated capacity of the cutting head motor,” Saminco said. “Infinitely variable speed control of the tramming motors allows for easy maneuverability in a clockwise or a counterclockwise movement.”

Regenerative braking can stop the machine faster than would mechanical braking, the company said.

The entire drive-motor system “is designed to fit in existing explosion-proof boxes,” the company said.

The remote control can be easily used while wearing gloves, the company said. The remote has a built-in safety functionality that shuts down the machine automatically under certain set circumstances.

A screen on the controller enables the user to monitor all functions of the system, “such as the stab jack, the gathering head, the conveyor boom, the cutter head, as well as subsystems such as lights, water, and dust control,” Saminco said.

The MSHA-approved remote supports both immediate diagnostics and data logging, Boles said.

The system can support proximity detection capability. “Since we have encoder feedback on the AC motors we are able to precisely control the speed of the motor,” Boles said.

With the regenerative system, “in the event that there is a proximity trigger, you are able to regen the machine down to the exact frequency you want to operate on,” he said. “If you get into a warning zone, you can tell the machine that you want it to go to no greater than 30 Hz and the machine will go to 30 Hz.”

In contrast, a DC system with mechanical braking is not as precise, he said. “With a DC motor you are at the mercy of inertia, gravity and other things to determine a set speed,” Boles said.

Further, with the AC solutions, “you get away from directional contactors, and instead come into an IGBT-based system,” he said. “You eliminate the maintenance of contactors in the panel, of brushes and the commutator.”

The system was originally designed roughly a decade ago for a customer in Asia. “We quickly discovered that not only could we use this in continuous miner applications, but the JR1000 at its core can be used on feeder breakers, can be used in belt drives, can be used in many other applications,” Boles said.

The drive is based on predecessor technology Saminco made for highwall miners. “It is the same situation, 1,000 V in and 1,000 V out,” he said. “It is a very versatile drive.”

The JR1000 VFD System has sold primarily to larger OEMS in Europe, South Africa and Australia, Boles said. “We currently have orders for three here in the United States.”

The smaller drive, the JD400, is a “low cost but reliable, proven system,” Boles said. It also features regen and diagnostic capability.

The solution is “a traction module for left traction and right traction, an interface box that allows cutterhead feedback to come in so that you can sump and scale accordingly, and internal overload electronics protection.”

The drive has been “really taking off in some areas of India and in some of the smaller mines in America, the small, privately owned mines that just want to keep costs down.”

Like everyone else, the supplier has recently been “hamstrung” by the ongoing supply chain disruptions, but has found viable workarounds. “Our vice president of operations saw this coming, as did some of the forecasting we did, and we have been able to pull in a few additional quantities on some of our standard orders,” Boles said.

“We have had some key suppliers, like industrial PLC systems suppliers, that have let us down,” he said. “We have had to switch to a couple of different alternatives from our standard control system in certain circumstances.”

The supply chain issues have hit amid a spike in new demand. Apart from that of OEMs, some of it is now coming from third party service suppliers, Rippy said.

Saminco can support miners directly, or their preferred OEMs and third party service suppliers. “If you have an issue, you come to Saminco,” Boles said. “We are a one-stop shop with a drive that is field proven.”

As-new Rebuilds Cut Costs

Phillips Global reported its continuous miner rebuild business is booming. “We have three shops across the country and all have significant miner work booked throughout 2022,” said Derek Baughan, vice president, Phillips Global. “We have a few customers already booked for 2023 as well.”

With the coal market in “an upward trend, we are forecasting the next 5 to 10 years to continue at the current pace,” he said. “Many mines are opening new sections, and mines are reopening that were once out of production.”

For four decades, Phillips has rebuilt, repaired and serviced continuous miners of all sizes and brands. The company offers both contract rebuilds and service exchanges. With the latter, the old machine is pulled and replaced with a rebuilt machine.

A contract rebuild can be completed on a schedule that helps the miners meet core goals. “We look at our customers in terms of long-term relationships and not just as a single transaction,” Baughan said. “We remain transparent with our customers throughout the rebuild process, keeping an open line of communication.”

Rebuilt machines can hit the same performance metrics as new machines, but give up to 30% cost savings. Each rebuild is fully tested and serviced prior to delivery.

“Our quality and workmanship is second to none,” Baughan said. “We offer fair prices and superior customer service before, during, and after the sale.”

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Study: Protective Shields Developed After Rockburst Kills Two 

Researchers from the University of Wollongong with funding from the Australian Research Council developed a protection system made of shields to protect operators of continuous miners after two were killed by a rockburst.

The two died after “a major rib and sidewall pressure burst occurred in a longwall development roadway” during operations at a coal mine in New South Wales” in April 2014.

As a result, “the industry is interested in developing a protective system that can be installed on the continuous miner as the last line of defense,” the researchers said in a report.¹

“As mining progresses into deep ore deposits in Australia, geo-hazards such as coal burst and outbursts are becoming a major concern for mine workers,” the report said. “The last line of protection will be the installation of a protective canopy on the continuous miner to shield mine workers from these deadly dynamic impacts of coal and rock resulting from a burst or outburst.”

The researchers calculated that “ejected coal blocks can reach 20 m/s high velocity.” A lab test was arranged to determine the impact force.

Coal blocks dropped from 6 m landed on a load sensor. The action was filmed by a high-speed camera.

“The energy carried by coal can be determined by the working energy theorem,” the study said. “The impact force and energy caused by a 175-g (0.7-m-diameter) coal block with 20 m/s velocity are 406 kN and 25,658 J, respectively.”

The researchers built a metal canopy, referred to as a protection system, of panels and a steel frame. Each panel had a honeycomb-like core that was 0.7 mm thick and surface plates that were 5 mm thick.

“A core is cut into pieces by water-jet cutting and assembled according to a specific arrangement,” the report said. “Then the two steel faceplates are welded with the core part,” it said. “The honeycomb panels are slid into a steel frame and connected to the frame members using bolted and welded connections.”

The system shields “both sides” of the continuous miner. “The total height of the protective structures is 1.5 m, which can provide enough refuge space for operators when dynamic hazards occur,” the report said.

The system was tested using drop hammer impact tests, which were also simulated using computer modelling.

For the tests, a panel was mounted on a frame designed for the tests, and “tested by a drop hammer system with 6.4 kN weight and 4-m dropping height,” the report said. “The falling hammer is gravitationally accelerated to over 8 m/s with 25,088 J impact energy.” Two high-speed laser displacement sensors and two strain gauges gathered data on the impact.

The panel absorbed the energy “via plastic deformation and crushing of the honeycomb core,” the report said.

“The far end of the square hollow sections showed around 26 mm of permanent displacement after the test,” it said. “The peak dynamic displacement of the center of the top honeycomb panel was 170 mm and permanent displacement was around 95 mm.” In other words, the panels were badly dented, but the structure held.

To complement the tests, numerical models were developed “using LS-DYNA R10.0 finite element code.”

The results agreed with the experimental results. “It can be observed that the honeycomb panel showed large plastic deformation and simulation well captured it,” the report said. “However, the experimental honeycomb panel showed asymmetric nature of deformation but numerically deformed symmetrically.”

The tests and modelling showed the shields could withstand the impact force and energy caused by ejected coal with 20 m/s velocity, the report concluded. “The system is capable of absorbing the energy of multiple large impacts with controlled deformations and limited damage to the main energy-absorbing components of the protective system.”

¹ Ren, Ting; et al. (2021) Developing an innovative protective structure on continuous miners against coal burst hazards. Proceedings of the 2021 Resource Operators Conference, Mining Engineering, University of  Wollongong.