Home > Heavy materials handling - Keeping iron ore on the rails

Heavy materials handling - Keeping iron ore on the rails

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Over the last few years mining heavy weight Rio Tinto has worked hard, making significant efficiency improvements to its Pilbara rail network. 
A key contributor to this success was the optimisation of train loading operations at Yandicoogina.

An essential part of their integrated iron ore production process, Rio Tinto's rail system directly affects the company's capacity to blend ore to customer specifications. 

Linking 12 mines with 3 shipping terminals, this impressive piece of infrastructure is the largest privately owned heavy freight rail network within Australia. 

Spanning some 1400km of track, it's responsible for moving 220 million tonnes of ore from Rio's Pilbara mine sites through some of the harshest and remote country on the planet to their port facilities.

Due to the weight and length of each train, three locomotives are used to pull the load at the front and two to push at the end of the train. 

With such an arrangement, the correct loading of the cars is critical. 

While consistently loading each car with as much iron ore as possible yields optimum network efficiency, it is important not to exceed the car's maximum load capacity.

Overloading places stress on critical components and infrastructure, causing failures that can lead to the possibility of train derailments. 

On the other hand, under loaded cars represent wasted capacity and poor network efficiency. 

Lightly loaded cars that are sandwiched between fully loaded cars can be lifted off the rails which also leads to derailments. 

Train derailments have a catastrophic effect on mining operations because they damage the tracks and depending on where they occur, and can halt rail traffic from multiple mine sites to the port. 

Repairing the line after such an incident and getting the train back on track can take days. 

If in the meanwhile, sites can't load and dispatch their final product, their stock piles reach maximum capacity forcing them to shut down their processing plants and mine production. 

Mine to port logistics operations are of such importance to Rio Tinto that in 2008 they launched a major project called 'Drumbeat' to optimise the efficiency of their entire supply chain. 

As part of this strategic project, mine sites were encouraged to improve the speed and accuracy of their train loading operations.

Responding to the challenge
The team at Yandicoogina, recognising 'Drumbeat' as a mine site improvement opportunity responded to the challenge. 

They decided to target a long standing issue responsible for heated debate between the site and port operations. 

The issue related to a discrepancy between car load weights measured and estimated during train loading operations at the mine site and those measured at the port. 

The mine operates two train loaders, one had a weighing system with a 2% accuracy, which introduced a variability of around 2.3 tonnes per car. 

The other relied on a weightometer that provided the weight of ore loaded on each train. 

This data was then divided by the number of cars to obtain an average weight per car. 

The port operations on the other hand have a facility to weigh each car individually giving a better indication of the ore weight per car. 

Unfortunately, by the time the train reached the port, was weighed and the data fed back to the mine, 24 hours had passed during which another 5 to 6 trains had potentially been loaded incorrectly. 
The net result was that while the site was targeting 116 tonnes of ore per car, they were actually loading anywhere between 110 and 120 tonnes per car and were seldom achieving their target weight. 
The team realised that the only way to improve their loading accuracy was by weighing the wagons accurately at the point of loading rather than at the port.
A project team comprised of a number of key staff including process engineers and the site's production superintendant, was assembled to identify ways of improving overall train loading performance. 
The key to delivering these improvements was their ability to accurately measure the weight of each car before and after loading and to provide the operator with rapid feedback as to how well they are loading the cars. 
Because loading speed was also an important consideration to operational efficiency, weighing had to be accomplished dynamically while the cars were moving through the loader. 
The key selection criterions for the system were accuracy and ease of integration into the existing train loader's automation system. 
The team gained management approval for the project's capital expenditure based on an average gain of one extra tonne of ore per car. 
Having received the green light from management, the project was handed over to Sang Nguyen, a planning and engineering superintendant.

Implementing the system:
Sang said "I guess that I took the project on myself due to its size, complexity and automation intensive nature." 
Reflecting on the choice of Schenck Process as the system supplier, he said that "in choosing our supplier, we were looking for a 'one stop shop'.
"We needed a partner that could not only supply a weighing system to match our needs, but one that could also provide seamless integration into Yandicoogina's existing PLC and Citect SCADA system. 
"Schenck Process was a good choice because they were the OEM that had originally supplied the train load out and associated weighing and automation systems. 
"The fact that MULTIRAIL was already being used successfully in many European 'Legal-for-Trade' applications with an accuracy of 0.5% made the system appealing to us." 
The weighing system for each train load out (TLO) is based on two separate MULTIRAIL train scales. 
The 'Tare' scale located on the inbound side of the TLO provides the weight of each empty car heading in for loading. 
On the outbound side of the TLO is the 'Gross' scale that measures the weight of each loaded car as it leaves the load out. 
The MULTIRAIL electronic modules are connected to PC's that are responsible for logging the car weights.
Each car is identified using an RFID tag, then its empty and loaded weights are logged. 
The scale PC's are linked to the TLO's Modicon Quantum PLC via a Modbus TCP/IP Ethernet network. 
The PLC interprets the weight data and reports back to the loading operator in real time via the TLO's SCADA system. 
This allows the operator to make instant adjustments to the way that they are loading which has lead to a vast improvement in loading accuracy and consistency. 
The real time tracking system also provides site production staff with valuable statistical data as to loading performance. 
Because the track scales PC's are linked to the internet via the company's corporate network, Schenck technical staff are able to access the system remotely via the internet, providing Rio Tinto with commissioning and troubleshooting support along with remote software updates. 

System usability:
Gerry West, Yandicoogina's fixed plant production superintendant said "the MULTIRAIL track scale implementation has enabled us to control our loading within much tighter limits allowing us to increase the average load per car by 2 to 3 tonnes." 
Gerry and his team analyse the site's loading performance and compare it to the car's weighing data measured by the port operations. 
He said that before the system was installed, data provided from the port indicated that 13% of their cars were being overloaded. 
Since the MULTIRAIL scales have been installed that number has dropped down to less than 5%. 

Project outcomes:
Rio Tinto's management were extremely pleased when they discovered that instead of the projected one extra tonne per car, Yandi were able to achieve between two and three extra tonnes per car. 
The discrepancies between the estimated tonnes per car loaded at the site and those reported from the port were a major concern for Mark Rodgers, Rio Tinto's general manager - Yandicoogina. 
The last thing that he wanted was for his site to be responsible for a derailment on a critical part of the line that could disrupt production at multiple mine sites. 
This type of event is considered within the group as 'major' and is said by staff to be on par with the impact of a tropical cyclone. 
Not only did the project improve the company's bottom line through the improved efficiency of Rio's Pilbara rail logistics, it also provided significant peace of mind to the management team and helped the company reduce its environmental footprint. 
On top of this, the payback period was only a few months.
Commenting on the impact of the project Mark said, "from an overall perspective, we are now probably the most consistent operation with respect to tonnes per car." 
"We have a number of different weighing systems throughout the business and it gives us a lot of confidence to know that ours is on track. 
"I used to constantly be questioned about having the right number of tonnes per car," he said. 
"We're always trying to squeeze out as many tonnes as we can so a key benefit of the system is that it has helped us to achieve that." 

*Peter Newfield was a technical support manager at Schenck Process Australia at the time of original publication.

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