Service Strength Supports Terex SHM and their Mining Equipment

Through innovative design and 24 hour technical service, Terex SHM is instilling confidence in its surface mining customers.

As mining technology becomes increasingly sophisticated, the complexity of the systems involved can present both challenges and solutions. Invariably the challenges occur at the least convenient time and place. On the other hand, the diagnostic capabilities that are built into today’s systems can speed their resolution significantly.

As the world’s leading supplier of highwall mining systems, Terex SHM has achieved a dominant position in this specialized mining equipment sector since the company was founded in 1994.

In mid-2006, the company shipped its fiftieth machine, its market having grown rapidly during the early 2000s as an increasing number of coal mining companies and contractors joined those that had already seen the system’s capabilities in terms of producing low-cost coal.

Supporting this surge in sales has been Terex SHM’s commitment to design development on the one hand, and in providing on-demand, round-the-clock service support to its customers on the other. Continuing engineering and software development has been a feature of Terex SHM’s business philosophy since Day 1, according to the company’s director of sales, J D Fairchild, who points out that not only are current upgrades fitted as a matter of course to its new machines, but that all of the previous generations of its highwall miners can be retrofitted in order to bring them up to today’s mining equipment specifications.

See the Terex SHM Highwall Mining System in action in our new High Definition Highwall Mining Video. 

“Our aim is to make sure that all of our customers can benefit from new engineering and software concepts,” he adds, going on to list some of the innovative designs that Terex SHM has introduced in recent years. “One of our customers wanted a different discharge system from the one that we had,” he explains, “so we designed the rear-discharge system for them and modified their machine. Since then all of the miners we’ve sold have been rear-discharge.”

“What the rear-discharge design also did for us was to reduce some of the constraints on mining to depths of over 1,000 ft,” he adds. “While the original vertical-discharge system could handle most coal flows from low- and medium-height seams, it was possible that flows might be tight where the machine was working in thick seams. Using rear-discharge means that we can now work in seams of any thickness without any risk of bottlenecking.”

Other major innovations have included the company’s bench-anchoring system, designed to provide increased stability for the launch vehicle even in the deepest holes, its right-angle conveyor (used in conjunction with the rear-discharge system), which allows cut coal to be stacked on either side of the machine, and its most recent success, the introduction of natural gamma radiation sensors to improve cutterhead position control within the coal seam.

New-generation control

Terex SHM has always relied on a Programmable Logic Control (PLC) at the heart of its mining equipment, with touch-screen operation from a central control cabin mounted up high at the rear of the launch vehicle. Simple to use with its clear screen-based controls, this has served the system well, not only in the field but also in terms of its training capabilities for new operators.

The new control system now installed is also PLC-based, but as Terex SHM’s director of service, Frank Nett, explains, it provides some significant advantages in terms of both usability and its maintenance capabilities. “The whole mining equipment system has been upgraded to run on a Siemens Step 7 PLC,” he notes. “Its Profibus loop architecture means that there is less hard wiring involved, and the whole unit is smaller, so that we have been able to bring the soft-start module into the main control cabinet, for example. It also has much greater diagnostic capabilities built-in,” he goes on, “which means that troubleshooting is much more straightforward and quicker than before.”

His comments are echoed by service manager, Doug Meador, who has the responsibility for ensuring that Terex SHM’s customers receive the full level of support for which the company has developed a strong reputation.

“There’s much more in the way of internal diagnostics than in the past,” he agrees, “the circuit diagrams that we have to work with are much more detailed and the new software makes finding where problems are so much easier.”

Not only does the operator benefit from simpler servicing capabilities, but the whole display has been improved, according to the company’s director of engineering, Stewart Myers. “As well as the new graphics-based touch-screen system being easier for operators to use,” he states, “it also provides us with greater international capabilities by using symbols rather than lettering. When we sell machines overseas,” he adds, “the control system is already set up, even if the operators use a different language.”

“With the company guaranteeing 24/7 service backup to all of its machines.”

Wherever they may be, the ability to make diagnosis over the phone is a major advance for both parties involved. As Doug Meador notes, guidance for many service-assistance requests can initially be provided by phone, with on-site technical support as the second stage in the process if this becomes necessary. Every aspect of machine assembly and service is ISO 9001 certificated, he points out, with an ISO logbook being compiled for each highwall miner as it is built. “That way, we can ensure that full quality control is in place for all of our mining equipment.”

“In addition, Terex SHM provides each machine owner with a day-by-day preventative maintenance requirement list,” he goes on, “so there is a clear record of all the work that has been done to the miner. Where backup is needed, we have seven technicians based here at Beckley, plus another three at Pikeville, Kentucky, specifically to look after the machines that are working in that part of the coalfield.” In terms of the distance that the company’s technicians have to travel to provide service support to machines in the field, “Around 600 miles at the moment,” he says, “to a machine in southern Illinois, but we have also provided support in New Mexico and Colorado when machines have been working there.”

Customer-led design developments

Not only has Terex SHM invested heavily in operability, but the ‘hardware’ aspects of its mining equipment are also continuously evolving. As Frank Nett explains, a lot of the development projects the company undertakes are done in response to specific requests from individual customers. “We have a policy of working closely with our customers,” with regular site visits to see how the machines are working in those particular conditions, and what can be done to make them more productive.

“The introduction of the rear-discharge design is a key example of that.” The new system has proved to be more reliable, without the high-wear areas that could affect the original vertical-discharge design. In fact, "when we field-converted the first machine to rear-discharge, there was a 50% drop in the load on the horizontal auger motors. The owner saw two major benefits immediately: higher production and less maintenance."

Other customer-led developments have included improvements to the linear position sensors used on the machine’s hydraulic cylinders, and the introduction of natural gamma sensors on the cutterhead, says Stewart Myers. “We found on the machines that we have supplied to Russia that the previous position-feedback units were vulnerable to damage and to the extreme cold there,” he notes, “so we have redesigned them to be located inside the cylinders rather than outside. That way,” he adds, “the units are completely protected, and provide real-time feedback on the ram position to the PLC unit."

Meanwhile, the natural gamma radiation sensor system has meant that at least one Terex SHM system operator can mine clean direct-shipping run-of-mine coal that would otherwise be unrecoverable. Working in the Pittsburgh coal seam, contract-mining company Contour Mining Corp. is using gamma sensors on both the top and bottom of the cutterhead to control its vertical range, and is thus able to leave a skin of coal to protect the product from dilution with out-of-seam waste rock. As the Contour Mining’s vice-president, Dave Bundy notes, not only is the company now able to produce a low-ash product, but from a machine-control point of view, the gamma sensors have taken the place of the normal current-draw measurement for determining when the cutterhead reaches the seam boundary between coal and waste. “With the thickness of coal remaining being shown on-screen instead, our operators are not using amps any more,” he says. “They just rely on the gamma read-out to control the cutterhead position."

The increased productivity capabilities the Terex SHM has built into its mining equipment over the years have meant that although the machine is now considerably heavier than before, at around 250 tons, its modular construction means that it is still easy to transport, assemble and break down again when moves between coal mine sites are needed. The launch vehicle needs just 11 truck-loads for transport, with an assembly time of typically less than four days. Meanwhile, the need to maintain maneuverability on the bench, given the increased weight, has led Terex SHM to upgrade the machine’s track units, which now have heavier-duty hydraulic motors and gearboxes than before, with a 60% higher output in terms of tractive effort.

Looking to the future

With recent market conditions having strongly favored highwall coal mining, Terex SHM is not just relying on its reputation to maintain its position as a top mining equipment manufacturer. As both Stewart Myers and Frank Nett explain, the company has a number of concepts under development, aimed at both better machine control and further productivity enhancements.

With long-term highwall stability a key factor in ensuring the safety of coal recovery this way, maintaining the correct entry orientation can be critical, according to Mr. Nett. “Following on from the introduction of natural-gamma cutting control,” he says, “we have been working with a Honeywell laser ring gyro system that will give us the opportunity to ensure that each entry is aligned correctly. Improving the steerability of the cutterhead module within the seam means that we can improve the resource recovery as well.”

“Other current projects include improvements to the bearings for the pushbeam auger.” adds Mr. Myers. “The problem is always made worse by the conditions that the augers work under, but if we can get longer life out of the bearings there, we can cut the power needs for the augers and get deeper holes as well as increasing the time between pushbeam maintenance.”

The power available for transporting the cut coal back to surface is also a key factor in terms of developing a highwall miner for steep dipping seams, since the current generation of machines is constrained to a maximum of 7-8° dip. “As a rule of thumb,” Frank Nett notes, “you lose about 2% of your productive capacity for each degree of dip, since the augers have to lift the coal up the gradient as well as move it horizontally.  As well as this,” he adds, “other factors that have to be taken into consideration include a clamping system to hold the pushbeam string when you’re removing individual pushbeams during cutterhead retreat, higher-capacity anchoring for the launch vehicle, and a self-levelling operators’ cab, not to mention operational basics like water control and ensuring lubrication."

“Interest in steep-dip applications has really taken off over the last couple of years,” adds Stewart Myers, “and this has to be one of our longer-term aims in terms of adapting our existing designs to these requirements. In the mean time,” he concludes, “we’ll just keep on making whatever improvements to our mining equipment that our customers need.”