Coal mining operations are facing huge cost pressures as the long slump in prices of both thermal and metallurgical coal shows little sign of ending – and longwall mines are no exception.
“Decreased demand for coal, with the accompanying reduction in coal prices, forces a mine operator to focus on reducing operational costs,” explained Jim Haughey, Global Product Manager for Shearers/AFC at Joy Global. “The reduction of operating costs through staff reductions and reduced equipment maintenance results in fewer personnel to operate and maintain longwall equipment and increased intervals between maintenance.”
This cost pressure has also impacted longwall equipment sales, according to Dr Uli Lange, Deputy Director of Sales at Eickhoff. “From our perspective as a supplier of premium coal cutting equipment, one of the biggest challenges the longwall mining industry has had to face has been the massive decrease in commodity prices,” Lange said. This has resulted in “longwall operators being put under massive pressure to reduce costs; hence less sales volumes at OEMs for longwall equipment.”
At the mines, this means that operators are looking to extend the life of existing equipment. This can lead to reduced productivity, said Haughey, as older equipment significantly increases the likelihood of equipment breakdown – with the consequent growth in maintenance requirements. Older equipment can also lead to increased dust generation – either from worn bits or poorly-maintained dust suppression systems – an important issue as regulators around the world are imposing stricter limits on the amount of dust to which miners can be exposed.
To counter this, some mines are looking to automation to help boost the amount of coal they can cut using existing equipment. “Operators intend to increase production with their existing equipment in order to balance out low revenues resulting from low coal prices,” explained Lange. “This can be achieved by means of automation while cutting at less gaps in production flow, hence higher average cutting rates. Automated systems usually do not allow for production records over one shift; however, in the long run, such systems guarantee higher average production rates per month and year.”
Away from the economic challenges, geology is also becoming more difficult, according to Dr John Stankus, President of Keystone Mining Services, a Jennmar affiliate, with deeper overburden, weak geology and increased horizontal stresses all requiring more difficult and expensive roof control.
Haughey agreed: “Due to the depletion of ‘good seams’, mine operators are now forced to mine lower-quality coal seams that include more rock – or to mine large amounts of reject material to get to the coal seam.” This again increases the amount of dust – as well as noise – produced during mining, adding to health and safety challenges, as well as increasing the time required to mine the desired amount of coal and wearing the cutting tools more quickly (again a source of dust).
New technologies for new challenges
To meet these new challenges, mines are turning to technology to maintain productivity and ensure their personnel work in safety. Automation is the buzzword here – but it is not the only development that is helping to make longwall mines safer places to work in.
“New roof control products are being developed to deal with more difficult ground conditions: e.g. higher-capacity cable bolts, pumpable cribs for roof-to-floor support, easy-to-operate steel props and cuttable non-metallic rib control products,” said Stankus. “Additional advancements have been made in computer modelling technology and methods that provide improved and more accurate determination of stress conditions that affect roof control.”
And in terms of the equipment, “underground coal mining machinery will probably become more and more intelligent in order to avoid unsafe interaction and to cope with negligence of human beings in close proximity,” predicted Lange. “It is essential to have reliable sensor technology onboard that gathers a lot of information from the environment around the equipment in order to support various kinds of jobs at the coal face.”
“Data gathering, storing and analysis is crucial for further development of automated by safe systems,” Lange continued. These systems can also provide information on the condition of the components, supporting predictive maintenance rather than risking hazardous breakdowns while in operation.
Sensor technology was also highlighted by Haughey: “Advanced sensor technologies, along with the latest cameras, coupled with high-speed date communications, are enabling mine operators to move mine personnel away from the face and to monitor longwall operations from a distance.”
Meanwhile, before a miner even enters the mine, technology – in the form of computer or simulator-based training – can help operators to learn safe operating and maintenance procedures without putting themselves and colleagues at risk underground, added Lange.
The search for the Holy Grail: longwall automation
Ultimately, however, the increased use of technology will be used to reduce the number of miners underground through the use of automation. And a fully-automated longwall system is an achievable goal, according to all three interviewees.
There is, however, always likely to be a need to have people underground, as Lange explained: “A fully-automated longwall face seems to be a realistic aim, when speaking only about production. Nevertheless, it seems very unlikely that maintenance and repair services will be able to be conducted without personnel. When breakdowns occur, quick reaction times are essential for operating companies. From today’s point of view, only mine personnel can guarantee those quick reaction times.”
“We expect that there will always be a need to send mine personnel underground to perform normal maintenance tasks associated with longwall equipment (e.g. changing bits, checking and replenishing oil and chain maintenance) and to deal with exceptions (e.g. geological changes, high methane gas readings and water infiltration)” concurred Haughey.
Health and safety improvements
So what is on offer now to improve health and safety in longwall mines?
“Joy Global offers a number of technologies to reduce the exposure of mine personnel to longwall mining hazards,” said Haughey. These include the following:
- Advanced face straightening to align the longwall system with the face during operation.
- Advanced shearer automation to provide an automated mining system for the longwall shearer.
- Proximity detection and shearer radio motion monitoring to help protect longwall operators and other personnel on the longwall face from being injured by the longwall equipment.
- Cameras mounted on shearers and powered roof supports, coupled with high-speed data communication, allowing face visualisation from a remote location, either at the headgate or on the surface.
In addition, JoySmart Solutions, which analyses longwall data that has been captured through the use of various technologies and transferred to a central location through high-speed communication systems, further enables a mine to operate a longwall system from a remote location and with fewer personnel.
“In general, one could claim that Eickhoff shearer loaders are AFC-mounted-and-moving sensor packs,” said Lange. “Many safety features based on sensors within the electrical system and attached to it have been deployed underground for many decades, monitoring temperatures, currents, earth faults and methane levels, as well as necessary water flow. Flameproof enclosures and intrinsically safe equipment is standard safety technology with shearers. Other types of sensors recently came into action: e.g. radar technology for collision avoidance or acceleration sensors in remote controls for detecting uncommon movements (tumbling, falling) of machine operators.”
Eickhoff also collects and monitors relevant information from the field at its headquarters in Bochum, Germany, allowing quick reaction to any problems that may be experienced. Meanwhile, a centralised server-based database, with multiple access levels and containing all reports, provides valuable information and statistics for clients for monitoring the performance and reliability of their machines.
On the ground control front, Jennmar offers a range of products designed to improve health and safety in mines, including SUMO™ cable bolts, fully-grouted cable bolts (FGCB), TT anti-friction washers, J-SAND® props, J-SANDY™ yieldable props, J-CRIB® pumpable cribs, fiberglass rib mats and cuttable cellular concrete for pre-development longwall recovery entries.
“SUMO cable bolts provide a very high-strength steel wire strand with metallurgy designed to resist stress corrosion cracking for applications in both coal and hard-rock mining,” explained Stankus. “Compared with 0.6 and 0.7 in. dia., grade 270 cables commonly used in US coal mines, the SUMO cable has a larger diameter of 1.10 in. and a minimum 66.2 short t strand ultimate tensile strength (UTS), which is much higher than the 28 and 38 short t respective capacities of 0.6 and 0.7 in. cables.”
“The TT anti-friction washer is used for various roof bolting applications to provide higher and more uniform tension and improve the beaming effect and roof stability,” continued Stankus. “It consists of two zinc-coated hardened-steel washers joined together with an exclusive polymer. The zinc coating provides a smooth clean surface to apply the polymer, which then allows for an optimum bond between washers. The zinc coating also enhances the lubricating effect and prevents corrosion. The combination of zinc coating and hot melt lubricant provides a much-improved friction-reducing medium.”
Into the future
“The biggest improvements to longwall health and safety will result from moving personnel away from the longwall face to remote locations,” said Haughey. “Therefore, Joy Global continues to work towards the development of a fully-automated longwall system, which includes expanding the use of advanced sensor technologies on longwall equipment.”
These sensor technologies will, according to Haughey, make further advances to face visualisation possible. “Improvements in face visualisation will result in a more accurate, remote picture of the longwall system’s operation, with the goal of removing mine personnel from the mine face – and thus farther away from the risks associated with moving machinery, dust and noise,” concluded Haughey. “The use of new sensor technologies is also expected to result in the ability to measure additional parameters, resulting not only in increased quantities of relevant data, but higher-quality, more accurate data, all of which can be analysed to assist in, and improve, the operation of the longwall system.”
“Eickhoff has and is always pushing the boundaries when it comes to improving operator safety, machine reliability and general functionality of design,” said Lange. “As well as mechanical design improvements, intangible developments, such as background data storage, processing and analysis, lay the foundation for improvement plans and are a fundamental part of our strategy. Close cooperation with our customers, a direct presence at the mines and quick support are further key aspects of our efforts in improving health and safety.”
“This paves the road for a structured R&D strategy leading to technologies, such as radar technology and high-definition video streams onboard our machines,” concluded Lange. “We strongly believe that automation and a good health track record go hand in hand, enabling operators to stay out of critical areas of operation and to manage the machines from a safe distance.”
About the author: Jonathan Rowland is the editor of World Coal.
Read the article online at: https://www.worldcoal.com/special-reports/07072015/adapting-to-straitened-times-2523/