Advancing Automation

James Yates, Caterpillar, Australia, reviews a recent longwall system update implemented by the company at an underground coal mine.

Situated in the Southern Highlands Region of New South Wales, Australia, the underground Tahmoor Coking Coal Mine, operated by Tahmoor Coal Pty Ltd (a member of the SIMEC Group and part of the GFG Alliance), has produced coking coal since 1979. Prior to 1987, the mine site used board and pillar mining for primary coal extraction. For more than 30 years since that time, a high-production longwall mining system has extracted most of the coal.

The Bulli seam mined at the site produces a hard coking coal used in the production of steel. Supplying material for both domestic and export customers, the Tahmoor Mine includes a coal handling and preparation plant capable of processing up to 650 tph of high-quality metallurgical coal.

The current coal panel being mined off ers an approximate 2.1 m high seam and spans just shy of 280 m long from main to tail gates. The longwall system consists of 159 Cat roof supports measuring 1.75 m wide, which were, until recently, operated by Cat PM4 roof support control units. Running longwall operations 24 hr/d to meet production targets exceeding 60 000 tpw, the mine now produces approximately 2.5 million tpy run of mine (ROM) coal.

Signifi cant system upgrade

The last complete longwall system upgrade made at the Tahmoor mine was over 15 years ago. Tahmoor was the last

company in Australia to purchase the Cat PM 4 roof support control unit in 2004, with the manufacturer introducing the Cat PMC-R unit upgrade shortly aft er.

With regulations driving strict limits on worker exposure to dust, remote control operation of the longwall system is the best solution, which partially contributed to the mine’s latest system upgrade. In addition, the mine was looking for ways to increase longwall system reliability and reduce overall operating costs.

Tahmoor mining off icials began working with Caterpillar in 2018 for upgrades to several longwall components. The investment included the new Cat PMC-R 2.0 roof support controller and Caterpillar technology upgrade, combined with a new power and ‘intrinsically safe’ lighting systems for the roof supports, complete with colour change functionality.

A new slope angle measurement (SAM-6) inclinometer system for measuring height and angle was also installed on the shields. This provides remote control operators with more information regarding the orientation of shields and added functionality for the roof supports to be set to height, rather than only pressure. In addition, SAM-6 provides enhanced anti-collision and unintentional movement detection capability, bringing the 2004-model roof support structures up to the latest technological standard.

Tahmoor also invested in numerous electrical system improvements to increase longwall operation and communication eff iciency, including the Cat Remote configurable input/output system (CIOS) ‘intrinsically safe’ programmable logic controller (PLC) racks for coal clearance system drive monitoring and health.

With materials delivered in 3Q20, system upgrades were completed for a December longwall operation restart. Despite so many new moving parts, the start-up process was successful, with a 20% reduction in start-up time, setting a new mine record.

A typical longwall system restart requires approximately 20 days from initial commencement to the first 100 000 t of ROM coal extracted. This start-up period, however, lasted only 15 days, and this was attributed to the major upgrade in technology designed to improve autonomous capability, plus the product support provided by the local Cat dealer, WesTrac.

Figure 1. Tahmoor’s longwall system upgrade included the new PMC-R 2.0 roof support controller and technology upgrade, combined with new power and ‘intrinsically safe’ light systems.

Figure 2. CAN extension devices and Ethernet ports provide improved connectivity and enable updates without controller hardware upgrades.

Automation and effi ciency

Maintaining consistent productivity to meet extraction targets for an underground coal mine largely depends on the eff iciency of the longwall production process. Advancing automation is key for the success of a longwall, and quality and reliability of the automation system are primary factors in the operation’s success.

For this reason, Caterpillar approached Tahmoor representatives with an opportunity to skip over the current Cat PMC-R series of roof support control system, originally introduced shortly aft er the mine purchased the PM4 units in 2004. The mine would be the first in the world to production-validate the next generation of Caterpillar’s successful PMC-R series: the PMC-R 2.0.

While the PM4 was cutting-edge for its time, the new PMC-R 2.0 system is light years ahead of where Tahmoor’s previous roof support controls were. The new controllers increase functionality due to more memory and a faster processor – allowing for more complex application soft ware, improved user interaction within the unit, and advanced visualisation and diagnostics with fast process data refresh rates. These, plus other enhancements, help to significantly improve the overall longwall performance and advance productivity and eff iciency.

Controller technology transformation

The new PMC-R 2.0 roof support controller off ers the same proven and reliable system topology as the PM4 and PMC-R, but has undergone a complete electronic and network architecture update. One benefit of the new design is its Ethernet backbone that delivers faster refresh rates and lower latency connections than the PM4 and PMC-R. The new controller has multiple processors compared to the PMC-R single processor, equipping it with the power required for future adaptation to autonomous technologies.

Its clock speed is more than 28 times faster than the PM4’s, while its 100 MB/s data transfer rate is more than 1700 times faster to off er virtually real-time system feedback, which improves remote operation capabilities. Memory has also been upgraded to allow for larger application soft ware, which contains more function modules and advanced features, providing the end-user with a future-proof platform for expanded autonomous capability.

Tahmoor’s new controller also helps to advance Caterpillar’s vision for longwall automation functionality of off ering sustained, consistent production at a specified rate for a defined period of time. Standard functionality includes the remote-control technology, providing the option for removal of the operator from the face and the utilisation of a machine interface graphical application running on a standard PC. This application provides a user-friendly interactive experience, which allows the remote operator to issue automatic commands to an individual roof support or initiate automatic functions like Batch Advance or SRB functions from the safety of a diff erent location, including the surface control room.

SRB start/stop flexibility has also increased with the new roof support controller. Tahmoor’s previous controller off ered only main- and tail-gate SRB starting points. In addition to main to tail and tail start sequences, SRB cycles with the PMC-R 2.0 can be set for all other sequences within the shear cycle, making remote initiation easier and safer. This improves shearer batch eff iciency and reduces the number of roof supports manually repositioned to increase productivity.

Tahmoor also equipped its longwall system with the Cat Pan Angle Measurement System to help better understand the floor conditions and provide real-time indication of the pan line pitch and roll, enabling the operators to react quickly if the pan starts to dive and correct prior to incurring operational delays.

The PMC-R 2.0’s colour LCD graphical display provides 50% more information at a glance than the PM4 and PMC-R units, improving the user interaction with the controller while on the longwall face during mining and maintenance operations. Off ering intuitive interaction, multiple keys allow direct menu and diagnostic access, and its reduced weight facilitates handling.

Minimising downtime and helping Tahmoor schedule maintenance, the PMC-R 2.0 off ers expanded VSoft ware feature capability. VShields graphically displays the overall health and condition of each roof support and provides complete local and global parameter control. The soft ware’s valve cycle count (VCC) application provides an overview of the operation cycles of each solenoid valve in the roof support, chain tensioning system, hoses, and staples. This allows Tahmoor to monitor equipment condition and set trigger points that provide an alert when a circuit is reaching a pre-defined limit, streamlining the maintenance management of hydraulic circuits.

Table 1. Comparison of Cat® roof support control units PM4 PMC®-R PMC®-R 2.0 Future-proofing the new PMC-R 2.0, additional communications ports and wireless connectivity allow for easy integration of new technology without a controller hardware upgrade, off ering simple plug-and-play operation of future devices.

Processor 8-bit 32-bit 3 x 32-bit Memory 288 kB 6000 kB 10 500 kB Data rate 57.6 kbps/ UART 600 kbps/UART Up to 100 mbps 2 wire Ethernet Display One line; 16 char Two lines; 22 char 30 keys 320 x 240 pixels; 31 keys IR receiver External Internal Internal Wireless No No Yes Alternate connections One spare data port (Zbus) Multi-function ports Multi-function ports Controller Area Network Weight 10 kg 10 kg 5.5 kg Figure 3. A new slope angle measurement (SAM-6) inclinometer system installed on the shields allows roof supports to be set to height rather than only pressure. Figure 4. PMC-R 2.0 provides backwards compatability, which allows for an easy upgrade of PM4 and PMC-R systems.

The controller is backward compatible with existing PM4 and PMC-R system components and compatible with Cat electrohydraulic systems and sensors currently installed on field roof supports.

Initial results

Longwall system upgrade investments at the Tahmoor mine have resulted in increased productivity and reduced ownership costs. Serviceable controller parts allow minor repairs to take place at the mine site, lowering total cost of ownership and reducing the operational risks associated with sending equipment off site for repair. Lower latency communications provide virtually real-time updates on equipment performance and health, simplifying remote operation and improving decision-making for reducing longwall start/stops.

Three test periods were conducted over the span of four months to determine the advanced functionality and uptime availability of the new PRM-R 2.0 roof support controller. Comparing calendar time, unscheduled downtime, scheduled production time and unplanned delays, the total PMC-R 2.0 availability reached 99.79%, exceeding the expected 98% availability.

The controller’s advanced functionality test conducted in May 2021 consisted of 17 diff erent acceptance parameters, ranging from shearer drum height adjustments and automatic target lines to VShield operation and automatic shield tow functionality. The PMC-R 2.0 functioned within established parameters and passed all critical operating tests with minimal soft ware updates required.

Since installing the system upgrades and new PMC-R 2.0 roof support controllers, Tahmoor has seen consistent and sustained improvement in longwall productivity and output. The significant technology advancements, including automation improvements with the PMC-R 2.0 controllers, coupled with the experience and service support provided by WesTrac, attribute to the increase in overall longwall system reliability.

Feedback on the new system from the Tahmoor Coal Project Manager mentioned that the PMC-R 2.0 delivered an out-of-the-box availability of 99.6% from first-shear with only improvements since to beyond 99.9%.

Two of Tahmoor Coal’s business values are ‘Change’ and ‘Sustainability.’ Changing its roof support control system to improve overall longwall eff iciency was key to the company’s sustainability plans.

Additional challenges to a greenfield project existed, with needs of retrofitting PMC-R 2.0 to the roof supports and interface with several existing site networks. Close engagement occurred between Tahmoor stakeholders and Caterpillar during the project, having a common goal to deliver safe and production-ready equipment. The now realised reliability in this goal has given Tahmoor confidence to quickly explore the full off erings of its first-in-the-world PMC-R 2.0 units.

Figure 5. Reported out-of-the-box controller availability was 99.6% and improved to beyond 99.9%.

Conclusion

The successful global production validation of the Cat PMC-R 2.0 roof support controllers has been noteworthy for the new control system, entering service and setting the benchmark for performance and reliability. Faster refresh rates, lower latency connections, and multiple processors make the system future-ready to accommodate further autonomous technologies as they emerge. Successful implementation of the PMC-R 2.0 upgrade continues the strong relationship between Tahmoor, Caterpillar and WesTrac, providing a solid platform to continue the journey Figure 6. Valve cycle count (VCC) allows Tahmoor to monitor equipment condition and set trigger toward autonomous coal points for pre-defined limits to streamline maintenance. production.