U.S. longwall production grew by more than 21 million tons in 2021.

OEMs adapt service to meet increasing demand

by steve fiscor, editor-in-chief

In a year where total U.S. coal production climbed nearly 8%, it seems only natural that production from America’s most productive underground coal mines would grow too, and it did indeed. More than half of the additional 40 million tons produced in 2021 came from the largest underground coal operators. Total U.S. longwall production grew by 17.3% to 142.7 million tons from 121.7 million tons in 2020.

Not all of the U.S. longwalls reported production increases and two of them closed. The total number of faces shrank to 37 from 40 and the total number of longwall mines declined from 35 to 33. Those figures include two trona mines in Wyoming and five mines that operated two longwall faces. Bridger Coal Co. in Wyoming closed its longwall mine and Panther Creek Mining is no longer operating a longwall at the American Eagle mine in  West Virginia. American Consolidated Natural Resources (ACNR) closed the Monongolia County mine in West Virginia. Longtime Coal Age readers would remember it as the Blacksville mine. Murray Energy Corp. purchased it from CONSOL Energy in 2013.

According to the latest statistics from the U.S. Mine Safety and Health Administration, two of the major longwall complexes, CONSOL Energy’s Baily Complex and ACNR’s Marshall County mine, achieved more than 11 million tons per year (tpy) during 2021. Both operate two faces in the Pittsburgh No. 8 seam. A dozen longwall mines produced more than 5 million tpy in 2021, compared to seven in 2020 (see Table 2). In 2019, 13 longwall installations produced at a capacity of 5 million tpy or greater.

A couple of new names appear in this year’s longwall census. ACNR’s Century mine in Ohio is now known as the Belmont County mine and the company’s Lila Canyon mine in Utah is also now known as the Emery County mine.

Arch Resources started the longwall at its new Leer mine in West Virginia during September. It is expected to produce up to 4 million tpy of high-vol A coking coal. It will operate in tandem with Arch’s flagship Leer mine for the next 20 years or more.

Industry Demographics

Longwall ownership in the U.S. remained relatively unchanged. ACNR and the companies it controls (Foresight Energy and Hatfield Metallurgical) operate 12 longwall faces spread across Alabama (1), Illinois (4), Ohio (1), Utah (1) and West Virginia (5). CONSOL Energy operates three mines with five longwall faces in Pennsylvania. Alliance Resource Partners, Arch Resources and Warrior Met Coal own three longwall faces.

With nine faces, West Virginia remains the longwall leader, followed by Pennsylvania (6), Illinois (5) and Alabama (5).

Looking at the numbers, the average U.S. longwall mine operating in coal produced 4.20 million tpy in 2021 compared to 3.75 million tpy in 2020. On average, it has a cutting height of 96.3 in., a panel width (or face length) of 1,236.9 ft, and a panel length of 13,091.6 ft. Last year, those numbers were 95.6 in., 1,210.1 ft and 12,341.3 ft, respectively. A total of seven longwall faces have face lengths of 1,500 ft or greater. A total of 13 longwalls operate in the Pittsburgh No. 8 seam. The maximum overburden on average reaches 1,107.6 ft. Except for a few mines in Utah, most are developed with three entry gates. Using an 1,883-hp double-drum, ranging-arm shearer, they take a 40.4-in. cut. The average yield setting on the shields is 1,058.3 tons. All of the faces except for three are high voltage (4,160 volts). Iron Senergy’s Cumberland mine operates the longest face at 1,580 ft. Coronado’s Buchanan mine in Virginia and ACNR’s Emery County mine are the deepest at 2,000 ft. At 26,000 ft, Foresight Energy’s Mach No. 1 mine has the longest panel.

Longwall Associates Turns Rebuilds Quickly

The world of longwall mining has changed dramatically in the past few years. The global pandemic, supply chain disruptions, labor shortages, rebounding coal prices and demand has created quite a challenge for the mines and the suppliers.

Longwall Associates said its shop is extremely busy right now. “We’re very fortunate,” said Dennis Heninger, engineering manager for Longwall Associates. “We are very thankful for the current, very busy situation, even though it can be challenging.”

Much of Longwall Associates’ work is rebuilds. “We’re running about 60:40 rebuilds to new equipment, primarily servicing the mines in the Appalachian Basin and Alabama,” Heninger said. “However, we can provide service for any longwall mine and we have recently supplied new equipment to Signal Peak in Montana.

When it comes to rebuilding armored face conveyors (AFCs), replacing and rebuilding the deck plate is standard procedure for the equipment that arrives on site, but there’s been quite a bit of upgrade work, Heninger explained. “There has definitely been an increase in coal demand and there are a lot of people wanting to increase production,” he said. “In the past 12 to 24 months, we have upgraded equipment to improve production and capacity, as well as just the normal repair work.”

With longer faces and higher production rates, customers are looking for larger chain sizes, larger sprockets and larger sigma sections to accommodate that gear, Heninger explained.

“Our focus right now really is supply chain management and keeping the workforce healthy,” Heninger said. “We have to have raw materials on site and we have to be able to process that and that equipment has to get to the mines without affecting their production. Most of our resources are going toward that effort right now.” Everyone is familiar with supply disruption, but the workforce issue is twofold with health issues related to the virus as well as general labor shortages, Heninger explained. “While I would like to say we’ve implemented some fantastic innovations at the shop, the reality is that we have to focus on those two areas to keep our customers supplied with equipment on time and ready to run coal,” Heninger said.

As far as steel supplies, Longwall Associates uses Hardox for the deck plate and they have several sources for mild steel. “Mild steel has not been a problem,” Heninger said. “Specialty steels, however, are a different story as far as plate, castings and forgings. We are spending a lot of time working with our customers to ensure that orders are placed with enough lead time.

“The average longwall rebuild for Longwall Associates, from the time we bring it from the yard into the shop until we start delivery, is about three months,” Heninger said. “That three months is from the time we bring it in the door. It all depends on the level of advance planning to secure a spot in the schedule. If the mines don’t plan ahead and they don’t secure a spot, then of course that affects when we can start. With new equipment, however, the lead time is about a year.”

“It all depends upon the customer and how proactive they are,” Heninger said. “Compared to five years ago, when it was a just-in-time mentality, a lot has changed and most of our customers are making arrangements and scheduling with sufficient time to accommodate everyone’s needs. Sometimes production timelines deviate from the plan and all of our customers do a good job of working with us to make sure that we know in advance to plan properly,” Heninger said. “What we are doing right now is trying to be very flexible, as much as possible to accommodate all of our customers, so that when things change, we can try to adapt to that change to meet our customer’s needs.

Joy Pursues Systems Approach

Komatsu is focusing on the next level of automation for its Joy brand of longwall mining machinery. The objective is to fully integrate technologies, such as the Landmark technology for shearers, proximity protection and enhanced geometry control.

The Landmark system, which looks after the operational side of the longwall, has proven itself, according to Shawn Franklin, shearer product manager for Komatsu, who explained why it has really taken in the last few years. “Its adoption level among U.S. longwall mines is approaching 20% and some now consider it an industry standard,” Franklin said.

Even though it’s described as a shearer technology, the system works with the powered roof supports and does much more. The shearer’s inertial navigation system collects data as it traverses from the main gate to the tailgate and vice versa and steers the longwall. “The intelligence and the corrections are carried out by the power roof support’s control system,” said Allan Black, roof support production manager, Komatsu. “Using data from linear transducers inside the double-acting, advancing rams, the roof supports make the necessary adjustments to bring everything back in line.”

Proximity detection protects longwall operators, which is especially important as mines shift more toward automated operations. Automation has reduced the amount of eyes and ears on the longwall face.

“Proximity protection is a nice feature,” Black said. “Operators wear a tag. All the hardware is built into the Joy RS20s control system. That tag is detected as the miner walks up and down the longwall. If an automated prime sees a miner in the way, it will pause operations. If someone has had a medical emergency, for example, it would prevent a roof support from being pulled over them causing more problems.”

Enhanced geometry control is another safety feature Komatsu is currently developing for longwalls. It relies on three tilt transducers installed within the powered roof support — one in the canopy, one on the base and one on the linkage. “Taking the data from those transducers and applying it to the known geometry of the shearer and the roof supports, we can determine potential collision hazards using algorithms,” Black said. “We see the pick marks on the canopies. Enhanced geometry is a very nice feature that stops the shearer from progressing if it sees a potential collision hazard.”

Beyond those three main areas of improvement, Komatsu is also improving the use of peripheral items such as cameras, which allow people in remote locations to continuously monitor the operation. “If there’s something that the transducer or the algorithm hasn’t detected, the camera serves as a fall back measure,” Black said. “They also provide a comfort factor. Operators can see that the system is operating the way it was expected to.”

Komatsu is now offering Rest API for shearers. “We have had it available on roof supports for a while, and we have just started to offer it for shearers,” Franklin said. “Rest API allows high level control of the equipment using software from a webpage so you can manage the equipment from a PC or a tablet or even a smart phone remotely. We have Rest API on one powered roof-support installation right now in the U.S., and we are starting to roll it out as option for shearers.”

Komatsu is also investing in shearer projects aimed at increasing productivity and reliability the old-fashioned way.  One example is the J7500 ranging arm currently in final design that is aimed at increasing both power and life.  “It will offer an arm, similar in size to the Joy J525 model, but with a 30% increase in power,” Franklin said.  “It will also be longer in length to keep up with wider panels with larger drives to improve gate-end cut-outs.  It will be our next generation arm to better serve the industry now and well into the future.”

Supporting Roof Supports, But No Longer Making Them

Komatsu made the announcement last year it would no longer manufacture powered roof supports. “However significant that move looked, the industry needs to know that we haven’t walked away from the powered roof support business,” Black said. “We have redefined our business model, whereby we no longer physically manufacture the support, however, we are still retaining the design and engineering capabilities, so we can still design roof supports for any customer’s requirements.”

As an example, Black cited project management as a service Komatsu offers. “We have in-house testing capabilities for original equipment support or aftermarket rebuild support,” Black said. “We have final element analysis (FEA), which detects high stress areas, and flow studies to determine the lower, advance and set cycle time for a roof support, or the flow characteristics for the entire longwall to determine the pumping requirements.”

Komatsu still provides key components, such as hydraulic leg seals, blipper valves, leg pocket castings, etc. “The valve gear is still manufactured in-house, as is the control system,” Black said. “We are still advancing work with electrohydraulic controls. We have a new development, the RS20n, which is a replacement for our RS20s control system.”

With its 1 Gb/s high-speed data backbone, the RS20n control system represents another significant change for longwall mining. “1000Base T1 two-wire system using a four core cable with two dedicated power lines,” Black said. “It’s physically robust and offers 10 times the speed of what is currently available on the market.”

With the other modules that will come with that system, the longwall operator will be able to tailor the longwall to suit the company’s automation as well as transmitting data very quickly from one support to the next to the gate end, Black explained. “It can interface cameras and other devices through media converters, so it provides the best communications infrastructure for a modern, automated longwall system,” Black said.

Black said Komatsu is also developing a new global dual solenoid with serial connectivity. “The Joy longwall control system was traditionally a three-component system, with mimic and micro-computing ‘the brains’ and the solenoid driver board,” Black said. “The serial connection removes the need for the solenoid driver board, making it a two-component system. It’s a lot simpler in the fact that the cable is just daisy-chained between the solenoids. The cable runs are tighter and shorter and it lends itself to easier fault finding.” Komatsu currently has a system running on larger roof supports in Australia and there are probably one or two applications where it could be used in the U.S.

Komatsu is also developing a “cost-competitive” tier 1 hydraulic valve control system, which replaces its traditional Compac system. “It’s got all the hydraulic benefits of a high flow unit,” Black said. “It’s designed to provide really quick response times and can be driven through the new RS20n control system.”

“Yes, we’ve moved away from the actual manufacture of roof supports, but we’re still designing them, supplying key components for them, and developing the next generation of controls,” Blacks said. “The goal is to offer better control mechanisms and improve cycle times as we advance toward a more remotely operated, automated longwall.”

Komatsu will assist mine operators in the manufacturer selection process. “We haven’t manufactured structures in-house since 2000,” Black said. “We’ve reacted very much toward the way the market was driving us. The highest cost items for a longwall system are the powered roof supports. It represents 80% of the cost of the longwall. We have retained the key components and the electrohydraulic controls. If you take the emotions out of the decision and look at what we’ve done, the mines will see this as a positive move.”

Longer Faces Require More Robust AFCs

For its line of AFCs, Komatsu is taking a more holistic approach. “We are looking at where our customers expect to be in five to 10 years and designing the AFCs that will meet those needs, while continuing to support today’s systems,” said Daniel Sharpe, AFC product manager for Komatsu. “We are positioning ourselves to make sure that we can provide the automation benefits that the customers want, which could be high-level automation with something like OptiDrive or simply meeting the geotechnical requirements of the equipment.”

The average face length among U.S. longwalls continues to grow. “To meet that need, we may need to increase the size of chains, and adapt our line pan designs,” Sharpe said. “We are also looking at shearer haulage as part of a larger system.”

As an example, Sharpe said engineers need to consider the seam height and the face length. “When you start specifying the system, in addition to the amount of coal loading on to the AFC, you also need to consider chain strength, chain size and the installed power on the face,” Sharpe said. “Going back to the systems side of things, the line pan has to be adapted to the size of the shearer to balance its center of gravity. We’ve seen a transition toward the upper end of our current capabilities and moving forward, we are positioning ourselves to meet the future needs of the industry.”

To add 300 ft of line pan to a longwall, there is more to consider than stronger chain and increased horsepower. “You’ve got to find that sweet spot where the system is robust enough to manage that, but there’s also the softer side around the automation and the things that we could put in place to make sure the system doesn’t get itself into trouble,” Black said. “You don’t want to bog the AFC down. The system needs to be intelligent enough to realize it’s approaching an overload condition and slow the shearer until the AFC clears.”

Chain management has become much more important with longer systems, Sharpe explained. “The system needs to be more sensitive to anomalous situations that could create a chain event,” Sharpe said. “Putting these technologies in place, we can assure that the longwall can handle it. We now have three fully developed chain management offerings that range from a relatively simple system to one directly measuring tension in the chain.”

Komatsu is currently looking at the interaction with the shearer and controlling the speed of the chain on the AFC. “It’s something that’s still being developed, but initial indication is showing a tangible reduction in chain travel, which is obviously beneficial to controlling the production and the load on the AFC, and other impacts in terms of equipment life and wear,” Sharpe said.

To back all of this up, Komatsu offers Joy Smart Solutions. “All the information gathered through the transducers and the equipment itself feeds into the control mechanisms that also is recorded remotely,” Black said. “Joy Smart Solutions allows people to interrogate the data either live or historically to look at trends.”

With Smart Solutions, Franklin explained, adoption levels among U.S. longwall operators are approaching the 40% level. That feedback is vital to mine management, as far as making decisions regarding performance and productivity.