Capital Equipment News May 2018

MINING NEWS

Metso helps Ghana mine double valve lifespan

Problems with valves can lead to unplanned downtime and equivalent losses in output. This is why saving on valves can end up being expensive. With the help of Metso’s service experts, Ghana-based Tarkwa mine has been able to achieve consistent reliabili- ty, leading to improvements in the plant’s overall efficiency. Valves play an important role in the CIL (Carbon in Leach) refining process, which Tarkwa mine adopted in 2004, both in terms of their numbers and functionality. Prema- ture failure has the two-fold outcome of unplanned downtime and subsequent losses in output. Metso’s Service Sales Engineer for Valves business, Christian Appiah, explains that valves in the mining environment work under extremely demanding conditions. “Valve and actuator failure can arise for a number of reasons. For example, high levels of pollution owing to dust and other contaminants results in very poor air quality. Added to this are the problems of very high ambient temperatures and pressures, not to mention the challenges posed by vibration. An erratic and low-voltage power supply Three new Cat articulated trucks – 730, 730 EJ (Ejector), and 735 – have been extensively re- designed, enhancing the field-proven features and performance of their C-Series predeces- sors (730C2, 730C2 EJ, and 735C) with new operator stations – including innovative new controls, transmission-protection features, new hoist-assist system, advanced traction control system, new stability-assist system and a fuel saving ECO operating mode. In addition, the design of the 730 and 730 EJ is enhanced with automatic retarder control and a hill-start feature. The 735 retains these features from its C-Series pre- decessor and further incorporates significant design refinements that include a new Cat C13 ACERT engine, Cat CX31 transmission (also on the 730 and 730 EJ) and structural and dimensional modifications that reduce empty weight by 22%, while retaining the productivity of the outgoing 735C. These features combine for an up to 19% gain in fuel efficiency. The new 735 replaces the Cat C15 ACERT engine, rated at 441 net horsepower, with the Cat C13 ACERT, rated at 428 net horse- power. The new 730 and 730 EJ continue to use the Cat C13 ACERT engine, rated at 367 net horsepower. The C13 engine used in all the new trucks is available in configurations

also compounds potential issues,” he says. Appiah goes on to explain that the valves fitted as original equipment to the sec- ond-generation plant performed as expected in terms of life expectancy, however it was after routine replacements that problems began to emerge. Metso has enjoyed a longstanding rela- tionship with Gold Fields Ghana through its supply of heavy duty equipment, including crushers, pumps and mills. It was from this association that Tarkwa was approached with regard to the possibility of sourcing alternative valve requirements from Metso’s Valves business services. That was the beginning of an intensive process involving a great deal of ground- work and technical analysis over a five-year period. Appiah was deeply involved in the process that ultimately provided the solution to the customer’s needs. To cover the de- manding application requirements, the best fitting valves were selected from Metso’s large portfolio of products for different min- ing and mineral processing plants. For the Tarkwa mine, the solution was control and on/off valves, including ball, butterfly and to meet emissions standards of both high- ly-regulated and lesser-regulated countries. The 730 EJ is designed to eject loads while traveling, providing positive dump- ing of the entire load, and also to work in areas with overhead restrictions and with soft underfoot conditions with improved machine stability. The cab’s new external “spinal-ROPS” design incorporates a rear-quarter glass that eliminates a structural pillar in the C-Series design, for enhanced rear visibility. Also, a new “wake-up” feature initiates the machine’s displays when the door is opened. The door is of a lighter, stronger design with

Christian Appiah, Metso’s service sales engineer for Valves business.

V-port control valves that had been supplied in 2015 as replacements for items that had reached the end of their working lives. The dual advantages of the scientific selection and installation of valves to the correct specification and of a durable quality were soon recognised by Tarkwa Engineer- ing management. “There has been signif- icant reduction in downtime and gain in productivity matched by reduced operational expenses,” says Solomon Boateng, Plant Engineer for Tarkwa mine – CIL. b monitors the working angle of the tractor and body, as well as the grade, and cautions the operator if the machine is approaching the set threshold angle, stopping the dump process if continued action may result in potential tipping. Further enhancing safe operation is the Cat Advanced Automatic Traction Control system, which features refined technology for proactively applying differential locks to avoid wheel spin. Also, a “terrain-based”, throttle-smoothing system prevents acceler- ation surges when traveling over extremely rough terrain that makes keeping a steady pressure on the throttle pedal difficult. b

Design refinements for new Cat ADTs

a shut-assist feature for improved sealing against dust infiltration. The overall cab design results in lower inside sound levels at 72 dB(A), a 7 dB(A) reduction compared to previous models. The optional Cat Connect PAYLOAD technology calculates payload via sensors on the walking-beam suspension, and load-status lights at all four corners of the cab roof ensure visibility to the loader operator from any angle. In addition, the standard Cat Detect/Stability-Assist system

The new 735 replaces the Cat C15 ACERT engine, rated at 441 net horsepower, with the Cat C13 ACERT, rated at 428 net horsepower.

CAPITAL EQUIPMENT NEWS MAY 2018 34