Minifex Rosebery Mine, an underground lead-zinc operation on the West Coast of Tasmania, has been operating in its current form for more than 60 years. Mining has taken place in the area for more than 100 years. The mine has historically had a five year life for the past 40 years. Recent underground exploration indicates that the orebody is not closed off at depth, plunging down dip to the north of the mine. Rosebery is one of the deepest mining operations in Australia, relying on a combination of truck haulage, internal shaft hoisting and a rail haulage system to deliver ore to the concentrator. In 2003, taking into account advances in truck design and truck haulage technology, the mine decided to decommission the internal shaft and rail haulage systems.

To effectively deal with the challenges of moving to truck haulage methods, Rosebery researched technologies to support its continued drive to incorporate best practice in truck haulage. In 2004 the mine embarked on a project in association with Maptek to implement a real-time fleet management system by integrating the MineSuite software and hardware modules into the existing mine operating systems.

One key challenge was managing the increased traffic flow underground with bigger trucks and more mobile equipment due to improved underground access for site service providers. Traffic management was critical for productivity and personnel safety - the interaction of light and heavy vehicles was of particular concern. Decommissioning the shaft also meant that the most accurate method of measuring tonnes mined was eliminated. Mine to mill reconciliations required the development of a reliable truck weighing system.

Another issue was the increasing mining cost with depth. Exploration drilling indicates that future orebodies will be deeper, requiring longer haulage distances. It was vital for Rosebery to optimise its truck haulage operation to offset cost pressures associated with longer haul distances. Additional challenges included increasing demands on the mine ventilation.

MineSuite technology had first been trialled as a vehicle alert initiative. In 2003 work began on a trial to determine if MineSuite's real-time information management system that allowed tracking, monitoring and reporting of equipment, processes and personnel, could be adapted to the underground environment. At that time, most applications for MineSuite had been surface-based using GPS systems.

The most attractive aspects of MineSuite were its ability to minimise human error as a factor in information input, and its compatibility with existing mine communications infrastructure.

Significant upgrades were required and new frequencies commissioned to allow voice and data to be transmitted by the mine's leaky feeder radio system. Tags were placed strategically around the mine; tag readers were installed in all trucks and loaders, along with software to allow reports to be generated. Problems with the information being generated were initially tracked to tag reliability, then to mine radios.

Further problems were traced to the tag readers. Vibrations were causing hardware component failures and the onboard payload system was found to be running at the same frequency as MineSuite. After more robust readers were installed and the frequency issue resolved, reliable reports on fleet performance were generated by 2006. The real-time information system and condition monitoring technology has been established at Rosebery with the continued development of MineSuite's hardware and software. Many man-hours hours have gone into the development of the system for underground operations.

MineSuite relies on vehicle tag readers collecting data from strategically located tags. As the mobile equipment traverses the mine, the tag readers continually send information through the 2-way radio system to a database storing all sent information. Tag readers, also known as Viper units, are remote processing units containing a single board computer, interface board and internal radio housed in a tough cast aluminium outer enclosure.

Viper units are located on all operating trucks and loaders. The devices receive signals from tags throughout the mine and send this information (time, date and tag location) through the 2-way radio co-axial cable to a central database. These units can also interrogate/receive data from onboard equipment management systems and transfer information such as engine hours, speeds, gear selection and engine temperature, to a central database.

Touchscreens in trucks and loaders display information from the MineSuite database and light vehicle tags. They are configured to display the vehicle alert system at all times.

The user interface enables interaction with stored information in the MineSuite database from data manipulation to reporting. Typical outputs include key performance indicators, delays, quality parameters and physical locations. KPIs include tonnes, equipment utilisation, tonnes per hour and cycle time. Delays are captured and rated by level of importance.

In 2005, surface scales were installed near the portal to obtain reliable truck weights, measuring every load of ore delivered to the coarse ore bins. MineSuite is now integrated with the scales, which are fitted with a tag reader to send information to the database.

MineSuite allows continuous monitoring and recording of truck movements and condition. This information is highly reliable, requiring no human input. The focus to date has been on movements and load weights. Reports allow the analysis of truck cycle times, truck and loader startup and shutdown times, individual truck tonnages, traffic delay times and truck tipping locations.

Cycle time analysis

MineSuite allows the analysis of truck cycle times from load to tip point. A summary of the cycle times was obtained for a fully loaded AD55 truck tramming from the 42P horizon to the surface stockpile.

Two routes are available - one is shorter but truck drivers believe that the longer route is quicker due to the shallower grade in various sections. A theoretical haul time was calculated as a base for comparison, for the ideal situation with no traffic delays. Times were obtained from MineSuite for both routes while the route was cleared of all traffic. Over the next few shifts haul times were recorded under normal operating conditions. The data revealed a significant difference between expected and actual cycle times (below).

Cycle times are up to 21 minutes longer (40%) depending on the route used. It is known that loading times are not the bottleneck; the added time taken per load effectively means less material delivered to the surface. Before the introduction of MineSuite, data collection was subject to operator error. Anecdotal evidence suggested the quickest route to be the Back Decline. In contrast MineSuite reports favoured the B-P Decline. This information is unquestionably reliable and replaces opinion with facts. The next phase is to determine the reasons for delays. Since MineSuite has the ability to determine the location of other vehicles in the vicinity, reports can be developed to analyse their impact. A working group will then be formed to analyse the data and develop systems to optimise cycle times.

Startup/shutdown and overloading

A MineSuite report was developed to analyse individual truck startup/shutdown times and locations, load weights, truck numbers, load and dump points, and loader type for the haulage of ore to the surface.

Analysis highlighted two areas of the haulage process that impacted on performance. Trucks were consistently starting up or shutting down at two particular locations in the mine. The result was that trucks were often queuing at the stope at the start of shift and queuing at the surface refuelling/service bay at the end of shift.

Further analysis revealed inefficiencies in the LHD servicing process. Project teams are currently using MineSuite data to review loader servicing schedules and are developing an end-of-shift operator pickup system using a mine bus.

Truck overloading can reduce equipment component life and compromise truck safety systems. Rosebery ore has high specific gravities and overloading has historically been difficult to quantify. Concerns with overloading were primarily based on anecdotal evidence from maintenance personnel. Due to poor reliability of the 'load rite' systems used at Rosebery, control and monitoring of this issue was ineffective.

Using MineSuite to monitor and report reliable truck load weights in a timely and consistent manner highlighted the issue. Information was fed back to the crews and the supervisor was made accountable for overloads, resulting in improvements (above).

Surface tipping locations

A recent study of surface tipping locations revealed that different ore types were not reporting to the right areas on the surface. For example, high grade ore was being tipped into the low grade bins instead of the stockpile, having a significant impact on operations, even though not directly related to trucking performance. A process was developed to ensure better stockpile management control and monitoring.

Vehicle awareness

MineSuite's vehicle awareness system has helped Rosebery address the issue of heavy and light vehicle interaction. Light vehicles entering the mine are fitted with programmable tags featuring a unique identification number. The heavy vehicle tag reader reads the light vehicle tag when within range (approximately 50 metres). The graphic touchscreen flashes a warning to the truck operator and the 'name' of the light vehicle (electrician, surveyor) is displayed. Since introduction of the system in September 2005, no accidents between heavy and light vehicles have been recorded.

MineSuite offers Rosebery the opportunity to be a leader in truck haulage systems in the underground environment. Several projects involving MineSuite are in progress or planned in the near future.

Thanks to Sean Pearce Manager of Mining Zinifex Rosebery Mine

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