Cutting-edge unloaders boosting export capabilities

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 08 Jul 2013   Posted by admin


IN keeping with its growth strategy, Fortescue Metals Group has successfully completed an impressive upgrade to its bulk material handling facilities at Port Hedland that will pave the way for the company to reach its target export capacity of 155 million tonnes per annum.
From humble beginnings in 2003 Fortescue has grown into the world’s fourth-largest iron ore producer. Its first mining operations began at its Cloudbreak mine in August 2007, with the constructionof all mine, rail and port infrastructure completed in 2008.
A critical part of the company’s port infrastructure, a Metso TU601 twin cell tandem train unloader, was put into operation in April 2008 when Fortescue unloaded its first trainload of ore at its Herb Elliott Port, near Port Hedland in WA.
Since then, the company has fast-tracked its growth by steadily increasing production from Cloudbreak mine and beginning operations at its second mine Christmas Creek in 2009.
Fortescue general manager – port Gerhard Veldsman said that the company’s unloader was able to cope with initial production from the two mines.
“At that stage, the mines were running at about 70 to 75mtpa; car dumper one was running really well, matching the capacity of our mines,” Mr Veldsman said.
“Even now, I don’t think that anyone in the Pilbara is able to unload at that rate. The problem was that we had more mining capacity and shipping capacity than dumping capacity.”
In 2010 Fortescue approved an ambitious expansion plan to triple production to 155mtpa. The US$9 billion project not only included an expansion of mining operations at its Chichester Hub and a greenfield development at its Solomon mine site, but an expansion of the company’s port, train unloading capacity and main rail network and a new line to the Solomon site.
Fortescue port shutdowns supervisor Brad Stillman was involved in all aspects of the first TU601 train unloader’s maintenance, which ranged from basic weekly inspections to major change outs. Mr Stillman said that the TU601 was at home in the harsh conditions of the Pilbara, due to its sturdy construction and reliability.
“We’re not in a pharmaceutical lab – it’s a really rugged environment out here. But even so, the unloader is like a Swiss watch – everything just works. That’s why it’s my favourite piece of the plant. It is a big, heavy, powerful piece of gear that needs to be treated with respect,” he said.
On the back of the reliable performance of the first Metso twin cell tandem train unloader commissioned in 2008, Fortescue awarded Metso Mining and Construction a contract to supply two more identical systems.
The first of the two new unloaders  (TU602) was commissioned ahead of schedule in mid-September and the second (TU603) in November 2012.
Mr Veldsman said it was crucial that the TU602 unloader was delivered on or ahead of schedule and that the ramp up had to go well, because the business was experiencing a “real bottleneck” when it came to unloading trains.
“It was delivered two weeks early, which was fantastic. The original ramp-up schedule was meant to be eight weeks, but we shortened that to six and we did it in four,” he said.
Mr Veldsman said the early delivery of the second train unloader resulted in Fortescue being able to dump 580,000 tonnes of unbudgeted ore in September 2012.
“At $100 a tonne, that’s $58 million in extra revenue that we hadn’t counted on. So the early delivery helped cover our capital investment,” he said.
According to Fortescue operational readiness and commissioning manager Mark Shirley, the company is clearly benefitting from the additional capacity of the TU602. He said that although it was not yet needed for full time use, the TU603 unloader was also already playing an important role. As well as catering for future expansion of the company’s production capacity, Mr Shirley said the TU603 provided overall system redundancy in case of any problems occurring with the other unloaders.
“Train unloader two is hugely important to the business, taking us to between 110 and 115 million tonnes capacity,” he said. “TU603 is also one of the critical parts in our supply chain; if you’ve only got two train unloaders and you lose one, you’ve lost 50 per cent of your capability.”
Mr Veldsman agreed, adding that the installation of the two new train unloaders represented a significant part of the company’s move to expand Herb Elliott Port.
Delivering ore from mine to port Fortescue’s railway is the heaviest haul line in the world, with a 40t axle load capacity.
The company’s rail infrastructure operates 24 hours-a-day, seven days-a-week. Each train is about 2.7km long and carries up to 32,800t of iron ore in 240 freight cars.
Trains arriving from the mine sites are moved through one of the unloaders. During unloading, two wagons are simultaneously unloaded every 90 seconds. The unloader clamps and then inverts the wagons, rotating them through 150 degrees. This is done without uncoupling the wagons, as each pair of wagons has a swivel coupling at either end.
The wheels of the train are locked in place before unloading to prevent the train from moving during the rotation cycle. The contents of the wagons are dumped into a chute that feeds an apron feeder, which then transports the ore onto a conveyor feeding one of the facility’s stackers. The stackers create the port’s stock piles, which are later consumed by reclaimers that feed the company’s ship loaders. Unloader composition and functionality
Each unloader consists of three main parts: the indexer, the tippler and the train holding devices.
The indexer is a rail-mounted vehicle that advances the train through the unloader, two wagons at a time. This heavy-duty work-horse moves back and forth along a short, straight rail track at the entry to the unloader. It is moved by 13 vertically mounted drive units, each powered by a 90kW, three-phase motor that turns a pinion via a gearbox.
These pinions engage the indexer’s rack which is mounted down the middle of the rail section, along which the indexer moves.
The indexer also incorporates a retractable hydraulic arm that is inserted between the wagons and pushes the train along by two wagons for each cycle; the arm is then retracted at the end of the indexer’s forward travel.
Photoelectric laser sensors are used to locate the gap between wagons, allowing the indexer arm to be precisely positioned before it is extended. The position of the indexer is monitored by a rotary encoder as well as inductive proximity travel limit sensors. This is backed-up by mechanical over travel limit switches which trigger an indexer ‘fast stop’ in case the travel limit sensors fail. The indexer’s drive motorsare controlled by variable speed drives that deliver an amazing combined power of 1.1MW to move the train.
The tippler or freight car tipping and emptying device is a rotary machine made up of two unloading cells. Each cell comprises a main cell structure, a drive unit and support roller assemblies, as well as a braking and lubrication system. The tipplers are located in an enclosure that is part of a pressurisation and dust extraction system. The cells are each equipped with train rail sections and on-board hydraulic clamps that hold the wagon in place as the cell rotates during the unloading cycle.
The clamping system consists of four hooked arms that have three positions: fully raised to allow a locomotive to pass; intermediate position allowing wagons to pass; and engaged position where the wagons are held. The intermediate position is the normal retracted position during unloading, allowing a gap of just 20mm between an ore car and the bottom of the clamp, greatly reducing engagement and retraction time compared to the fully raised position, allowing for optimal unloading times.
Each tippler cell has its own drive unit to rotate it. When the train unloader is tipping, the drive units of both cells are connected together via a cardan shaft to make sure that they are perfectly co-ordinated. The position of each cell is also monitored by its own encoder and fed back to the system’s PLC. Both drive units comprise a three-phase 200kW electric motor which drives a pinion in either direction via a gearbox. The pinions act on geared drive racks that are mounted on theouter diameter of the cell end rings. The motors are controlled via variable-voltage variable-frequency (VVV F) drive units that incorporate closed-loop speed control, ensuring smooth and efficient operation. Finally, each cell drive has a disc brake with two pairs of brake callipers. Each calliper has a dedicated hydraulic power pack to operate it independently of the other, providing redundancy in case of brake failure.
Hydraulically powered train holding devices are located at both the inbound and outbound sections of the unloader.
Four sets of wheel locks are located before the tippler entry and six sets of wheel grippers are located after the tippler exit to prevent movement of the two ore cars being unloaded. Each set of holding devices is powered by its own hydraulic power pack.
Mr Shirley said the system provided a lot of flexibility, along with failsafe measures to protect staff and guard against downtime and production loss.
“It’s certainly very easy to utilise the redundancy that’s provided by the new train unloaders by simply switching from one to another. Each train unloader is able to link with at least two stackers, providing operational flexibility. This is one advantage of having the three up and running,” he said.
“What we want to do is keep train unloader three in a ready state so that within 24 hours we can fire up and run it if we need to. So certainly the arrangement that we have provides a lot of flexibility.”
Safety is a top priority for Fortescue, and the company’s team worked with Metso to ensure maintenance personnel were keptout of harm’s way.
“Our scheduled shut-down happens every 12 weeks where we’ll go in and do work, which is mainly driven around the conveyor belt maintenance and chutes,” Mr Shirley said.
“We have trialled a new idea with TU602 and 3 where we’ve located the hydraulic power units off-board – on TU601 they’re actually on the tippler cell itself which creates a few maintenance issues. So we’ve taken the power packs off the tipplers and we’ve just got hoses running to them now.
“This means the maintenance technicians no longer have to go on the tippler itself, meaning a couple of the major hazards we had identified in our business are completely removed. With safety our number-one priority, the associated safety benefits are significant.”
While the automation of the train unloaders is rather complex and is managed by a standalone system, each unloader also has to co-ordinate with the control of the other port equipment such as apron feeders, conveyors and stackers.
“Our process has to be highly automated because we run very lean structures. Themore we can automate the better,” Mr Shirley said.
“We’re certainly on the bleeding edge of that technology. The automation platform is GE and its all Ethernet connected, so there’s massive capability there; we can set-up remote condition monitoring at these locations and have it all reporting to a central data centre.” said Mr Shirley.
On site, Fortescue employs a process control team resourced with a lead, process control engineers, and on-shift technicians.
One operator and one electrician together run an entire train unloader asset, while the train circuit itself is controlled from an integrated operations centre in Perth. Two operators are responsible for inload and outload duties at the operations centre in Perth; this includes managing the activities  of the on-site operators, such as directing who attends issues as they arise on the circuit.
“Two operators and two electrical technicians are on-site on a 24-hour basis. But essentially the system is all controlled out of Perth, so the role of our site staff is to do inspections and to provide rapid response if there is an issue,” Mr Shirley said.
“We can direct them very quickly and they can attend to the issue and get it resolved in the shortest possible time.” Fortescue director development Peter Meurs said the commissioning of TU602 was a major milestone for the company as it continued its expansion to 155mtpa.
“The second train unloader takes our unloading capacity to 120mtpa, which gives us the capacity to reach a run rate of 115mtpa by the end of the March 2013 quarter, comprised of 95mtpa from the Chichester mines and 20mtpa from Firetail,” Mr Meurs said.
“The third train unloader will give us in-loading capacity well in excess of the 155mtpa we need for our current expansion project.”