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Leveling the Pilbara

MM joined the Vermeer Specialty Excavation team at Christmas Creek mine in the Pilbara for a sneak peek of the company’s newest surface excavation machine – the T1655 Terrain Leveler

Sep-2012

Christmas Creek iron-ore mine is part of Fortescue Metals Group’s Chichester Hub located near the town of Newman in the Pilbara, Western Australia. The Hub comprises Fortescue’s flagship mine site, Cloudbreak, and its second site, Christmas Creek, 50km east of Cloudbreak. Together, the mines produce 55Mt/y of iron ore and the hub will ramp up to a targeted 95Mt/y (including 5Mt from the nearby Nullagine operation which Fortescue co-owns with BC Iron) through 2012.
 
Mining began at Christmas Creek in May 2009 and since then, major expansion projects had been undertaken to increase the site’s capacity. During the first phase of the expansion, a new ore-processing facility was constructed and successfully wet-commissioned in March 2011. The facility is now operating
at its targeted capacity of around 25Mt/y. The expansion also included a 50km extension to the existing Port Hedland- Cloudbreak rail line to serve Christmas Creek, and the addition of a 1,600-bed permanent operations village, built by Decmil Australia to house the growing Christmas Creek workforce. The village was complete when MM visited in early June, with plans to expand the facility further.
 
Work on the US$1 billion second phase of the Chichester Hub expansion was more than 75% complete when MM visited in June. During the December 2011 quarter, the product reclaimer at Christmas Creek was commissioned enabling significant reductions in the train loading times. A second 27Mt/y oreprocessing facility featuring a remote crushing station was under construction when MM visited, as was a new workshop to serve Christmas Creek’s growing fleet of surface miners (the workshop opened in August).
 
First ore through the new processing facility is slated for September, with the ramp-up to a combined Christmas Creek total run rate of 50Mt/y planned for the December quarter this year. The mine will also open its own airstrip in 2012 (visitors and workers currently fly into Cloudbreak and drive to Christmas Creek), and the mine’s power station is also undergoing expansion.
 
THE T155 PROJECT
The Chichester Hub expansion forms part of the larger US$9 billion T155 project to increase total production from Fortescue’s Chichester and Solomon mining hubs to 155Mt/y by mid-2013.
 
T155 will also require increasing the capacity of Fortescue’s 300km rail line that carries ore from its mines to accommodate 13 trains of ore daily (the line currently carries six each day), and a US$2.4 billion expansion at Port Hedland to manage the increased loads.
 
In its March quarter 2012 report, Fortescue stated that it had produced 12.6Mt since the start of the year. This was slightly less than expected, as the region suffered two cyclones, which meant the temporary closures of Port Hedland port. However, the company plans to make up the figures later in the year, and when MM visited, production was on schedule to hit 17.8Mt by the end of the June quarter.
 
MINING AT CHRISTMAS CREEK
Pre-pit stripping and production began at Christmas Creek in May 2009 in preparation for mine ramp-up. Like Cloudbreak, the mine has chosen to use a technique called precision surface mining. This involves using surface miners to exploit the wide, shallow deposits of iron ore situated near the surface. The Chichester hub is the only Fortescue mining hub to use this technique.
 
Surface miners cut the material from the top of the deposit following a pre-set pattern. The cutting drum uses teeth to break up the ore, which is then deposited on the ground behind the machine ready for loading and hauling, or is conveyed directly to waiting trucks. While drilling and blasting is very much a stop-start
process, surface mining smoothes the ore production cycle, making it more continuous, and eliminates the need for drilling and blasting. Surface mining also produces a smooth pit floor that can minimise wear and tear on mine trucks and loaders, especially on machines with rubber tyres, and enables operators to create vertical pit walls, thus maximizing mineral recovery. It produces small-sized material in a uniform configuration. This allows the ore to be handled more efficiently, and effectively removes the need for primary crushing. The uniform product size also allows more efficient settings on secondary and tertiary
crushing systems.
 
At Christmas Creek, Fortescue employs Australian contractors – Downer EDI, UEA and WA Surface Mining – to operate its surface mining fleets. The mine will operate 32 surface mining machines by year-end, including nine Wirtgen 4200SM units, 16 Vermeer T1255 Terrain Levelers, and seven units of Vermeer’s latest model, the T1655 Terrain Leveler.
 
The Vermeer units share a common control system, allowing the operators to be switched out each day. This gives them the chance to work with both the smaller T1255 and the larger T1655 models.
 
At Christmas Creek, the machines deposit the ore on to the ground after cutting, scrapers then pile and segregate the ore, and a fleet of loaders and trucks (mainly Caterpillar 777 and 785C models, mixed with some Terex trucks) remove the ore for processing. The smaller machines are used to clean the edges of the pits, for shorter runs and for tight spots, while the larger machines are used for large areas and long, straight runs.
 
Christmas Creek was the first recipient of Vermeer’s new T1655 Terrain Leveler in 2011. The machine will be officially launched at the MINExpo 2012 exhibition in Las Vegas, US, in September, but MM was able to gain some insight into the machine’s development while on tour.
 
DEVELOPING THE T1655
Vermeer’s specialty excavation business has been manufacturing track trenchers since 1958. These machines were originally designed to dig deep trenches in soil and rock to enable utility pipes and services to be laid. However, the market was small, so Vermeer decided to expand the potential of its products by modifying them to dig shallower, wider excavations more suited to road construction and site preparation.
 
In June 2001, a Vermeer dealer came forward with news that a US mining company was using Terrain Levelers to chase gypsum seams at one of its operations. Spying the potential opportunity, the Vermeer development and engineering teams set to work on creating a machine specifically for this market. They tried various designs and not long after, the T1255 Terrain Leveler SEM was launched.
 
The model featured 600hp (447kW) (much more than previous track trencher models) and a patented tilt-head drum equipped with teeth which cut the ground using a top-down rotating motion to
enable precision mining.
 
Top-down cutting allows the teeth to gain penetration without using the machine’s tractive effort to drive the teeth into the minerals. As the unit travels forward and the drum rotates, the teeth on top of the drum advance over the top of the ore deposit. As the teeth come down to the ground, they make contact by impacting the ore.
 
This technique also allows operators to control material sizing by changing the drum depth – increased tooth penetration boosts the material size, and decreased tooth penetration reduces material size.
 
As the concept of precision surface mining took off and more operators began to see the benefits, competition in the market began to increase. Vermeer believed it could do better, and so set about creating a Terrain Leveler to rival its competitors largest surface miner models.
 
DESIGN WORK
Using the design of the T1255 as a benchmark, the Vermeer team began work on the T1655 in February 2007. A number of issues needed to be addressed, and one challenge was to decide whether to use the chain-driven drum design from the T1255 for the new model, or to develop a direct-drive system. The width of the chain-driven drum allowed the creation of vertical highwalls, but maintenance of the drive
was one of the highest operating costs for the machine. A direct-drive drum was created and tested on a T1255 at a gypsum mine in Oklahoma. The concept was a success, and, by using direct drive, the team was also able to increase the power rating of the machine and reduce the associated costs.
 
There was also the question of loading. Vermeer carried out a thorough analysis to determine the best way to load material after the surface miner had cut it. Some competitors’ surface miner models incorporate a loading system that transfers material directly into a waiting truck, eliminating the need for scrapers and dozers. However, the varying characteristics within orebodies mean that rates of advance differ with the Terrain Leveler (the unit must move more slowly to cut harder deposits efficiently) and it would have been hard to co-ordinate loading trucks and managing a haul fleet to accommodate this. Vermeer calculated that it was more efficient to deposit the material on to the ground and load it into trucks using scrapers or dozers.
 
The next challenge was manufacturing the machine. Mark Cooper, senior director for specialty excavation at Vermeer, explained: “The T1655 was so far north of any other project we had undertaken. We needed to construct a new manufacturing facility just to create the prototype.”
 
In August 2008, work to build a new manufacturing centre at Vermeer’s headquarters in Iowa, US, began. The project was temporarily halted in 2009 due to the global financial downturn, but it resumed as soon as possible and the first high bay was completed in July 2010.
 
The prototype was finished in May 2011 and, to celebrate, Vermeer held an open-house event to introduce the unit to the local community and its workers. A month later, the machine was dismantled and shipped to Western Australia for testing at a facility in Bindoon.
 
After successful testing and a few minor design tweaks, such as adding more shocks to the suspension of the newly designed cab, the prototype was transported to Christmas Creek and the unit began production in September 2011.
 
PERFORMANCE AT CHRISTMAS CREEK
Testing of the T1655 prototype at Christmas Creek was due to last three months, or 3,500 operating hours. However, the mine management team were so impressed by its performance that, after 1,000 hours, Fortescue committed to buying seven more units.
 
When MM visited in early June, the prototype had been removed and was on its way to a BC Iron mine for testing. Two units were working in the pit, and a third had been assembled and was waiting at the local Vermeer dealership for delivery. The fourth unit was in transit from the US and a fifth was due to be shipped to Australia at the end of June.
 
Bill Vanderweele is Vermeer’s principal dealer for Western Australia. He has been working closely with the Fortescue team to deliver and support the Vermeer machines on site. He explained to MM that, on the T1655 drum, the picks are positioned at 4in (10cm) intervals in a chevron pattern so that, as the drum rotates, the ground is cut every 2in (5cm). The teeth on the edge of the drum are positioned facing outwards so they cut slightly wider than the drum width. This allows the operator to get close to the edge of the pit without damaging the machine.
 
At Christmas Creek, Fortescue uses Caterpillar’s MineStar fleet management system to guide its surface miners and monitor their performance (although it uses Trimble GPS units with Leica’s Jigsaw system at Cloudbreak). The engine microprocessors can sense the changing characteristics of the ore and slow or speed up the advance of the machine to compensate for this.
 
The nature of the ore at the mine (which can reach strengths of 250MPa in places) means that, on average, picks are changed out after cutting about 25 bank cubic metres (bcm), though this varies and picks often last longer.
 
The picks are fixed to the drum with an easy-release retaining pin. MM personally watched a pick change-out and it took no more than 30 seconds; no special tools were required. The design of the drum and rear-end of the machine means that technicians don’t have to stand beneath it to change the picks, which is a major safety boon.
 
Overall, the project can be deemed a success, and just two days into the month of June, the production teams using the T1655’s had already broken their daily targets: a feat that looks set to continue.
 
T1655 SPECIFICATIONS
At about 180t, the T1655 is much larger than its predecessor, the T1255. It stands 5.2m high with the air ride cab at full extension. The machine is 13.4m-long and 6.4m wide
 
The T1655 features two Cat C18 ACERT engines for a total of 894.8kW (1,200hp). The dual-engine configuration provides power to a common pump drive so that each engine supplies power equally to the unit; however, if one engine is not operational, the machine is still able to function with one engine. A 3,028L fuel tank provides 13h of continuous operation
at maximum horsepower.
 
The T1655’s dual hydrostatic tracks provide independent rotation in either direction. The machine can quickly reposition up to 360º in either direction for the next cut. The load control feature allows the machine to adjust ground speed automatically to use full engine power, therefore making the machine
more productive. This gives a stable ground drive speed for maximum productivity in varying conditions.
 
The T1655 has a direct-drive drum, with the drive motors attached directly to the cutter drum. This improves efficiency and reduces wear costs associated with chain, sprocket or belt transmissions.
 
The cutter drum is fitted on the rear of the machine, allowing the drum to cut material while the tracks remain on uncut ground so not to spoil the excavated material. This, and the unit’s low centre of gravity, provide additional traction and stability. The cutter drum’s patented tilt feature allows it to tilt 5º in either direction for a smooth excavated area.
 
Vermeer also designed several enhancements to the operator cab. An air-ride suspension system gives a the operator smooth, comfortable and quiet ride. The cab can also elevate to a maximum height of 5.2m and extends out an additional 58cm for enhanced visibility. The enclosed cab is roll-over protection structure (ROPS)-compliant. It features a filtered air system, dual heating/cooling systems, sound attenuating foam, as well as dual, full-suspension seats.
 
A key feature, the TEC Plus display, allows the T1655 to communicate with the various control modules through out the machine, as well as the engine. The display allows the operator to monitor and control machine functions and improves the onboard diagnostic capabilities.
 

The unit can also be fitted with a GPS navigation system, which can be used to create a 3-D map of the orebody and mining plan. The system collects production data and transmits it back to the office in real time for analysis.

 

Courtesy of Mining Magazine.