VDMA

INDIA 2018

Best of Germany 2014 - Mining Equipment and Mining Technology

Issue link: https://vdma.epubxp.com/i/1047212

Contents of this Issue

Navigation

Page 23 of 51

VDMA 22 VDMA MINING SUPPLEMENT • 2018 19.5 µS. The system can be adapted to water characteristics and the required volumes of water. The main 6,000-l tank holds 5,000 l of water-HFA-emulsion and 1,000 l of HFA concentrate. An automatic emulsion-mixing system enriches the water with concentrate. Analog measurement devices in the HFA and concentrate compartment show the filling level. A transmitted light refractometer with a biprism monitors the emul- sion. "All of our pumps and components are running with HFA [97% water and 3% emulsion] or clear water," Hoffmann said. "Clear wa- ter is of course used for dust suppression." The high-pressure station is also equipped with two hydraulic accumulators that reduce pressure spikes and shocks. Two auto- matic high pressure double back-flush filters clean the mixture again before it leaves the high-pressure station for the roof sup- ports in the longwall. Mines in different parts of the world use different pump station designs. Hauhinco for example supplies high-pressure pump sta- tions and water spray stations mounted on crawler tracks through- out mines in Australia. Onboard the crawler track mounted pump station is a dual-shaft motor system with pumps on either end of the motor. A variety of pumps with different flow and pressure ap- plications can be suited to this system. This system was developed to ensure all equipment is located in the one high-pressure area and therefore simplify transport lo- gistics when only moving one piece of equipment in the mine. On the run, maintenance with minimal downtime can also be achieved with this design. "With the dual-shaft arrangement, one pump can be quickly disengaged without any hot works or additional labor re- quired to achieve this, then the other pump application can still be left in operation. General maintenance can be carried out or the pump can planned to be removed if required, therefore continuing operation reducing downtime and production. This design is very compact and mobile, but the mine also must have a minimum 2.2-m seam height to accommodate the dual shaft design on crawler tracks. The dual shaft application can be incorporated into a monorail mounted station or a transportable base sled design. However, gen- erally we can accommodate all types of configurations. Improving Longwall Productivity and Safety While the use of automation grows, Caterpillar Global Mining Europe GmbH, continues to develop new longwall system components that lend themselves to automation, such as its High Torque Drive system. The armoured face conveyor (AFC) drive system improves longwall performance by replacing traditional components with more efficient ones. Such evolving and new technologies, according to Cat, promise to drive longwall production higher and cost per ton lower while reduc- ing exposure of miners to health and safety hazards. Recent production results recorded during automation implemen- tation on a high-production Australian longwall illustrate the positive roll that automation can play. In brief, weekly production grew from 61,592 metric tons (mt) to 118,094 mt as automation grew from 0% to 98%. Production grew more than 90% as the use of automation increased, as indicated by shearer ranging arm override commands. Cat said it has found similar results at two other Australian longwall mines owned and operated by different mining companies. In the first case, the average time taken per shearer pass dropped from 56 minutes to 44 minutes as automation was imple- mented. The reduced travel time increased the average number of passes per week from 68 to 91. In addition to increases in productivity, automation increased equipment availability and reduced in-panel parts usage, specifi- cally replacement of conveyor flights, shear pins and conveyor con- nectors, also known as dog bones. Over three panels, longwall sys- tem availability increased from 91% to 96.5%. The data collected, however, does not distinguish between mechanical availability and mine attributable delays, such as repair time and parts availability. The use of variable frequency drive (VFD) technology in longwall applications is a recent trend that has already made a positive im- pact on many installations. Using VFD technology and an innovative low-speed, high-torque motor, Caterpillar is working to step up long- wall face conveyor performance even more. The permanent magnet synchronous motor (PMSM) combined with the VFD promises multiple benefits, such as higher productivity and reduced total cost of owner- ship through low maintenance and high mechanical availability. The drive system also features an extensive automation pack- age, programmable for the application. It can be adapted to special applications or geological situations (roof falls, geological faults, etc.). Because the torque motor delivers max torque at any speed, the automation system can adjust speed to optimize production, reduce electricity consumption, and minimize wear on components such as sprockets and flight bars. The automation system is combined with enhanced condition monitoring to make sure that the machinery is protected and can run at maximum output. All of the necessary data is linked to a database to support predictive and condition-based maintenance. The High Torque Drive system is built around the low-speed mo- tor, which delivers the same high torque at all speeds. The convert- er-controlled torque motor operates at speeds between 0 and 300 rpm versus 1,500 rpm for induction motors. Lower speed reduces inertia acting on the output shaft by a factor of eight and enables the system to react quickly, which translates to little or no damage to the gearbox and conveyor chain in the event of a conveyor blockage. In addition to soft start and stop, the High Torque Drive delivers very fast acceleration. The variable conveyor chain speed can be efficiently adapted to the production conditions — resulting in less wear on the conveyor. The system also is about 5% more efficient than conventional drives. The improved system efficiency means lower energy consumption and reduced cooling requirements. The new drive system consists of two main components — a variable frequency converter and the motor-gearbox combination. As compared to previous systems, a medium-voltage converter-con- trolled torque motor replaces the AC induction motor. The control principle of the drive is direct torque control — the most advanced AC-drive control technology available. High torque even at low speeds enables using only one gear stage, which results in smaller dimensions while retaining the same torque capabilities as systems that are as much as 20% larger. The low speed of the motor also reduces wear and extends service intervals. In addition to soft starts and stops, Cat's High Torque Drive system reduces AFC wear.

Articles in this issue

view archives of VDMA - INDIA 2018