The latest in equipment, technology and consumables
By Donna Schmidt, Field Editor
| Joy Global has shipped more than 6,000 continuous miners to operations since 1948, many from the popular 12CM series. |
With hundreds of room-and-pillar mines dotting the nation’s coalfields, the wheels of technology and innovation that keep the industry sector safe, healthy and productive is long from slowing down. Efficient room-and-pillar mining is essential for every undergound coal operation.
Coal Age recently examined where some of this work is being done, from technological improvements for continuous miners and other associated equipment, as well as what lies ahead in the world of consumables. That future, true to form, looks bright.
Raising the Bar for Today, Tomorrow
Joy Global Underground Mining LLC has shipped more than 6,000 continuous miners to customers since 1948. It is safe to say that there is nothing the OEM has not seen, no major coal seam it has not met – and it has been present for many operations’ productivity milestones.
Of the OEM’s offerings, the Joy 12CM series has been at the top for North American customers. Designed for mid- to high-seam applications, the line includes six models. The 12CM15 is likely the most popular of that group for mid-level seams and the 12CM12 for mid- to high-seam applications.
Another in that line is the 12CM27, with a beefier frame and increased conveyor clearance to improve productivity. The 12CM27 is a high-voltage machine that is operated at 2300 volt 60 Hz (3300 volt 50 Hz) to provide a significant increase in horsepower to the cutting system. Reduced thermal losses in the cutter motors and trailing cable increase the available continuous cutting time almost indefinitely, leading to improved production levels.
All of Joy Global’s 12CM continuous miners are equipped with its dual-sprocket continuous miner conveyor chain. The patented dual-sprocket chain is 50% stronger in tension than conventional chains and is driven by two parallel eight-tooth sprockets to provide better torsional rigidity, according to Joy.
The Joy 14CM product line, ideal for low- to mid-height seams, is made up of eight models with loading rates between 10 and 40 tons per minute (tpm). The most popular is the 14CM15, with a wide 38-in. (965 mm) conveyor for increased capacity, and the Joy 14CM10, which has a ripper chain cutterhead for small diameter durability. The 14CM27 features a strong frame and good conveyor clearance to provide operations with longevity and productivity.
The 14CM’s cutting options include a solid head or Ripperveyor model, and they are available in drum diameters ranging from 30 to 44 in. with rated cutting power as high as 590 hp.
The basic elements of each continuous miner are similar in design. Each machine employs the OEM’s multimotor concept with outboard access to motors, gearcases, controllers and other major components. Joy’s philosophy has called for a design that isolates major components for easier troubleshooting and maintenance, and individual motors with direct drive transmissions to power the cutter, traction, gathering and hydraulic systems; the latter permits quick and easy service or repair to keep downtime and maintenance at a minimum.
Joy Global’s Wethead cutter system, a popular solution for coal mines, incorporates a fine spray behind each cutting bit of the cutter drums to reduce the potential for frictional ignitions and to reduce respirable dust levels. The water spray acts as both a cooling and wetting agent in order to address both issues, and also provides bit life-extending lubrication for the machine – all while consuming less water.
Regardless of a mine’s size, Joy officials are fast to note that they have a solution that will fit the operation’s needs and budget. “Base-level models like the 14CM15 and 12CM12 are standard across the industry,” according to Director of Marketing and Application Engineering Brian Thompson. “They offer exceptional reliability and longevity in an entry-level package, [while] the 14CM27 and 12CM27 are also available in high-voltage configurations.”
In addition to its work on remote controls that incorporate operator assistance tools, automated sequences, advanced diagnostics and performance monitoring analysis, Joy Global’s Faceboss control platform also allows for outby communications and advanced diagnostics in a user-friendly interface.
Also, the SmartZone proximity detection system is now available on all Joy continuous miner models. The system’s zones can be varied within limits to suit specific operational designs, and are automatically adjusted in the cut mode and tram mode to provide both warning and shutdown zones.
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| Caterpillar recommends its CM235 for seam heights of 43 to 116 in. (1,092 to 2,946 mm). |
Joy Global’s SmartConveyor technology encompasses sound abatement technology for mines that have returned noise level improvements of 45-65% in underground testing (versus standard machines).
SmartConveyor, an option on all of Joy Global’s current CM models, combines multiple technologies such as Joy’s Dual Sprocket Conveyor Chain and auto-tensioning features.
Overall, Joy Global CMs possess elements that reduce noise levels. The first is the dual-sprocket continuous miner conveyor chain and two parallel eight-tooth sprockets for increased torsional rigidity; together, they reduce the likelihood of abrupt chain breakage.
Finally, using Joy polymer-coated conveyor chains can provide an additional 3 dB reduction for the miner. “Utilizing the coated conveyor chain along with previously proven controls for the CM chain conveyor will provide operators with the opportunity to be within the Mine Safety and Health Administration (MSHA) permissible exposure limit,” Thompson said.
Friends in Low Places
Caterpillar has placed a sizable level of attention to the low- to mid-seam mines of the U.S. over the last few years, and its newest available model for those applications, the CM235, was unveiled at MINExpo 2012.
At 135,000 lb, it is among the most compact designs available from any OEM, and it has power all tied up with 2 x 205 kW/2 x 275 horsepower cutterhead motors. The CM235’s motors are parallel to the cutterheads, and they are perpendicular in the CM235T. Both have a variable frequency drive (VFD) traction system and have the same – and numerous other – features as other models in the CM200 series.
Cat recommends the CM235 for seam heights of 43 to 116 in. (1,092 to 2,946 mm), with a minimum clearance of 27 in.; maximum cutting height on the unit is 128 in. (3251 mm) and has a total power of 940 hp, as well as a balanced power-to-weight ratio and loading rates of 15 to 32 tons per minute (tpm).
The Machine Control Unit (MCU) is based on a mine-duty PLC and is designed to maximize coal production and operator safety while minimizing downtime, and traction motors are controlled by a microprocessor-based system, which minimizes electrical connections and enhances reliability. The MCU provides data logging, fast diagnostics and advanced troubleshooting capabilities. The control system is proximity-detection system ready, and a radio remote control unit with self-diagnostics is available.
The CM235 also has a graphic display to provide the condition of all motors and VFD components and the condition and position of hydraulic control valves and solenoids. Both standard and compact remotes are available to suit operator preference.
Easy, simplified maintenance and access also can be found on the unit, with centralized grease ports and fill points and easy-to-locate diagnostic ports and panels and a split cutterhead gear case for easier repairs as needed.
Safety and health are another point of concentration for Cat, and on the CM235 and 235T, enhancements to both are found via a quieter dual-sprocket conveyor chain that permits lower ambient noise, and a hydraulic temperature and spool position monitoring (over CAN bus) herald a new level of safety in which the machine can determine points of failure and recognize valve malfunction.
Looking ahead, the company said that electronic controls and technology are offering good opportunities for mines’ improved performance and simplified diagnostics. While rebuild orders are up versus new machine requests, the U.S. still is largely the leader in room-and-pillar innovation.
The OEM is also planning to announce further enhancements to the CM235 later this year.
On a related note, Caterpillar is also putting much effort into its scoop scene. Over four decades later in scoop engineering and manufacturing, and more than 6,500 battery-powered units produced, the manufacturer and its predecessors have developed and refined its low-maintenance, efficient utility vehicle, the Cat SU488, which remains the most popular low-profile scoop in underground coal operations.
An optional Cat HiPAC 10, a DC-to-AC variable frequency inverter control system to drive high-performance AC electronic motors, possesses superior speed-torque characteristics. Overall, the system is up to 14% more efficient than traditional DC motors, allowing for higher loaded tram speeds, more responsive hydraulic functions and more work per battery charge.
Cat scoops are also available with Cat diesel power. The SU488 D and SU482 DN are capable of operating over long distances at high speeds and are designed for challenging roadway conditions with steep gradients. Both units have advanced braking systems and are available for Pennsylvania and West Virginia operations.
Flexibility, Operating Performance Tops List for GE
GE Mining introduced several new items late last year at the China Coal and Mining Expo in Beijing, including the GE Fairchild F330 continuous miner.
The company also unveiled its GE Mining Load Haul Dump (LHD) loader to enhance operator safety and utility functionality with its sophisticated design technology, and the GE Mining Drill Guidance System with an Intrinsically Safe steering tool approved for operation throughout the world.
GE Mining Commercial Director, North America, David Willick looked ahead to the next great turn in room-and-pillar mining, and told Coal Age customers are seeking a reliable and durable unit.
“Our continuous haulage systems provide flexible ore haulage while articulating around 90?-ft corners,” Willick said. “This flexibility and operating performance are key differentiators needed in today’s demanding coal mining climate. Our continuous miner requires less time repositioning the machine…more available cutting time, which translates to approximately 40% more cutting time per available lift and no delays waiting on shuttle cars or to reposition the miner.”
Willick also noted that the industry is sweating existing assets more than they have recently, and pushing out rebuilds and replacements as long as possible while also looking for good used equipment from closed operations.
“The U.S. coal industry is in a challenging point and time,” he said. “Continuous mining equipment continues to be the equipment of choice for most effective and efficient bulk tonnage.”
Operations are also achieving excellent dust suppression with a system that utilizes a Venturi spray with a fine, air saturated atomized water spray, providing a number of advantages.
Working in Tandem for a Safer, More Productive Mine
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| Reducing noise-induced hearing loss in roof bolting remains a major issue in mining, according to Kennametal. |
The progress of mining equipment is vital, but complementary to that is the advancement of research and development for consumables. One of coal’s largest suppliers of these key suppliers, Kennametal, is most certainly keeping its eye on the future in that regard.
The Pennsylvania-based company was recently honored alongside the National Institute for Occupational Safety and Health (NIOSH) by the Society for Mining, Metallurgy, and Exploration (SME) with its 2013 Health and Safety Research and Educational Excellence Award, which was bestowed to NIOSH’s Office of Mine Safety and Health Research (OMSHR) Hearing Loss Prevention Branch for its research efforts and interventions to reduce noise-induced hearing loss. Specifically, the agency cited Kennametal’s bit isolators as being effective in reducing noise exposure during roof bit operations.
SME specifically mentioned the bureau’s “disciplined approach to identifying the sources of high levels of noise exposure and comprehensive process for noise-control development,” with focus on collaborating with partners to transfer research findings into commercial products to significantly reduce or prevent noise overexposure for miners.
The award also highlighted the NIOSH team partnering with Kennametal and Corry Rubber on developing bit and chuck isolators for roof bolting machines that are notably quieter in operation, better protecting operator hearing.
NIOSH characterizes noise-induced hearing loss, or NIHL, as the most common occupational illness in the United States today. Noise-induced hearing loss can be caused by a one-time exposure to an intense “impulse” sound, such as an explosion, or by continuous exposure to loud sounds over an extended period of time, such as noise generated when roof bolting in mines.
When individuals are exposed to harmful noise – sounds that are too loud or loud sounds that last a long time – sensitive structures in the inner ear can be damaged. These sensitive structures, called hair cells, are small sensory cells that convert sound energy into electrical signals that travel to the brain. Hair cells, once damaged, cannot grow back.
According to Kennametal, NIOSH has been conducting hearing loss prevention research through various initiatives including surveys designed to monitor worker dose; measurements of equipment noise levels; laboratory studies to analyze hearing loss; hearing protection device (HPD) research; and recommendations for appropriate and consistent use of soft foam earplugs.
These studies have been completed in underground coal mines including both room-and-pillar and longwall mining sections, or have generated results that are directly applicable to both room-and-pillar and longwall mining.
A NIOSH analysis of NIHL in miners presented a snapshot of the extent of NIHL in the mining industry. This analysis of several thousand audiograms indicate the number of miners with hearing impairments (defined as an average hearing threshold level of 25 dB or greater for the frequencies 1000, 2000, 3000, and 4000 Hz) increased with age until 50 years old, at which time 49% of the metal/nonmetal and 90% of the coal miners had a hearing impairment.
Roof bolting is one of the main contributors to miner hearing loss, affecting the quality of life of the bolter operator, and is an increasing cost to the mining company. Noise sources related to roof bolting are centered roughly 100 to 200 mm (4 to 8 inches) below the drill steel/roof interface and above the drill chuck. As the drill steel advances during cutting, so does the source of the chuck drill steel noise, while the upper source essentially remains the same.
NIOSH, Kennametal, and Corry Rubber research revealed that by isolating the chuck from the drill steel and the bit from the drill steel with a flexible, shock-absorbing material, the sound level is lowered considerably. Reducing the vibration transmitted to the drill steel means less excitation, which equates to significantly less noise produced.
An improved elastomer being investigated for use as a chuck isolator offers the advantages of durability, lower stress, a fail-safe design and greater flexibility in terms of stiffness “tuning.” NIOSH has been testing the system in normal working mine conditions underground, and initial data indicates that the isolators can significantly reduce the noise exposure by 3-5 dB.
According to Chad Swope, Kennametal manager, global underground mining, product management, the company works hard to deliver custom and standard solutions that are wear-resistant, from drums and drum designs, bit and block systems to roof full range of drilling systems and much more.
“The goal with consumables has always been to get things to last longer,” he said. “We began to change that thinking from ‘providing a bigger sledgehammer’ to supplying a sharper pick with the ProPoint tool line. The result has been a reduction in respirable dust and other benefits.
“This was the idea behind our Defender line, finding product improvements to in turn create a safer environment for the operators. The bit and chuck isolator developed with Corry Rubber, and NIOSH came out of that.”
Swope said that awareness for health issues is definitely growing, and the Mine Safety and Health Administration has also listed the bit isolators as a product option to keep companies in compliance with noise rules.
Another new product, he added, has been Kennametal dust catchers – a bit system accessory that keeps roof dust in the bit vacuum system and off of the operator.
“Safety will always remain a big thing as well as performance. Super-hard materials for cutting systems and roof bits are a good example of how our industry experience and knowledge can provide new products with appreciable safety and performance improvements,” Swope said.
Kennametal mining products are used in high-, mid- and low-horsepower continuous miners as well as high- and low-horsepower longwall shearers. With its long history and experience in the mining business, Kennametal can supply complete cutting systems or separate conical tools, bushings, sleeves, and blocks, so customers can assemble the best possible cutting system for light, medium, heavy and severe cutting conditions. Kennametal mining products are used in high-, mid- and low-horsepower continuous miners as well as high- and low-horsepower longwall shearers. With its long history and experience in the mining business, Kennametal can supply complete cutting systems or separate conical tools, bushings, sleeves, and blocks, so customers can assemble the best possible cutting system for light, medium, heavy and severe cutting conditions.
Dust and its Impact on R&P Mines
In June, the Mine Safety and Health Administration (MSHA) responded to a series of questions from across the industry on its new lower dust level requirements. Below are several of the issues addressed by the agency that have direct impacts on the room-and-pillar (R&P) community.
What controls does MSHA think I can use to lower the dust levels in my mine? I am doing all I can now.
MSHA response: Existing engineering controls are available that can be used to reduce the respirable coal mine dust concentrations in the mine. MSHA has reviewed the engineering controls in use on many inspection surveys to evaluate whether using additional engineering controls would have likely reduced the dust concentration to levels at or below the standard. Survey results indicated that additional or adjustment to controls would likely reduce respirable dust concentrations. MSHA determined that many MMUs could increase air quantity, air velocity, the number of water sprays, and water pressure; change the type of sprays and/or direction of sprays; balance the quantity of air delivered to the face with the scrubber air quantity; change the type of screen that is used in the scrubber system; and/or change from blowing face ventilation to exhausting face ventilation. Changing dust controls was an option at all MMUs that MSHA reviewed. On some MMUs that used blowing face ventilation and a scrubber, the air quantity provided was less than the scrubber air quantity, causing an imbalanced system and the potential for respirable dust overexposures. Because the amount of air available at the last open crosscut will be greater than at the face, the air could easily be increased at the face to provide greater protection of miners’ health. The number of water sprays, while important, is not the only spray variable affecting dust control; the location, flow rate, spray pattern, and droplet size are variables that impact dust levels where miners work. MSHA will provide compliance assistance on dust controls that are available and practical and hold workshops for interested stakeholders to disseminate this information.
My mines use continuous mining machines with a scrubber. The scrubber “makes” air in the face. Why does the rule require me to determine the air in the mining face with the scrubber turned off?
MSHA: A dust scrubber does not “make” air. The scrubber is a supplemental dust control device and does aid in directing the air provided in the face area. However, the scrubber can only work with the air that is provided to the face. It is important that the scrubber be balanced with the ventilating air provided to the area where the continuous mining machine is working. The air provided by the MMU ventilation system must be determined without the aid of the scrubber so that the scrubber can be provided with the amount of air for which it is rated and dust-laden air is not recirculated.
MSHA is making me put a lot more rock dust in my mine. How am I supposed to meet this rock dust requirement and still comply with the new respirable dust standard on each shift?
MSHA: Rock dust is required to prevent coal mine dust explosions. The respirable dust samples from underground mines do not reflect an increase in respirable dust levels with rock dusting increases since 2010. Rather, the average respirable dust concentrations have been dropping steadily since 2010.
Mine operators should obtain from suppliers rock dust that has as little respirable size particles as possible and exercise care in the application of the rock dust to limit the exposure of miners who are working downwind. These actions will reduce or eliminate the potential impact on respirable coal mine dust levels.
I use blowing face ventilation. Why do I need to sample my shuttle cars while those using exhausting face ventilation are not required?
MSHA: The need to sample shuttle cars on blowing face ventilation is because these occupations are in the return air from the continuous mining machine and are subject to exposure to higher concentrations of respirable dust.
If the dust parameters are the same on every MMU, is there a need to have a separate mine ventilation plan for each MMU?
MSHA: Yes. The general plan does not address the differences between MMUs and different mining machines. No two units are exactly alike and those differences must be addressed. Specifying general controls does not let miners and management personnel know what specifically works to control respirable dust concentrations for a specific mining machine in a specific location in the mine.
