Industry News

Mobile hopper challenge out west

Rocktec, which specialises in the manufacture of quarrying and mining equipment in Australia and New Zealand, has gained the reputation of ?thinking outside the box? with its innovative approach to unconventional challenges, but none more so than with the mobile ship-loading system that was designed and built for the Port Hedland Utah Point Berth project, commissioned by PINC Group Pty Ltd on behalf of the Port Hedland Port Authority.

Rocktec does not manufacture off-the-shelf mobile crushing equipment. As CEO Rick Johnson confirmed: ?The market for stock type mobile crushing plant is well served by a plethora of existing suppliers. Our expertise is targeted towards providing custom solutions for more project-specific applications.?

However, following this policy of bespoken configurations, Rocktec has, in recent years, built and supplied a variety of wheeled mobiles, incorporating jaw and cone crushers, screen/HSI combinations, specialised screening and washing outfits, as well as the largest tracked impact crusher in Australasia.

When it was appointed for the Utah Point Berth shiploading scheme in September 2009, Rocktec had to design rail-mounted hoppers, each capable of delivering a maximum of 2500 tph to an integrated 1500mm wide conveying system, and with the capability of being loaded from large front-end loaders. The trains were designed to operate over a central load-out conveyor, with trailing power cables and water pipes for dust suppression. The six hoppers and two motor control centres required for this solution have achieved considerable capital and operating cost savings.

The contract imposed strict time schedules on Rocktec to meet and, with manufacture commencing in October 2009, these deadlines were met, and shipment from New Zealand to Australia completed in April 2010 ? a challenge in itself with a total supply exceeding 700 tonnes in weight, mostly of over gauge items (no disassembly for shipment was undertaken).

A special vessel was chartered to ship the equipment direct from Tauranga, New Zealand to Port Hedland. This substantially reduced the transit time as it enabled shipment of complete units (avoiding part dismantling). Trans-shipment via Perth, followed by a road train to the site and reassembly in Port Hedland, would have required substantially higher labour costs.

Installation commenced immediately upon arrival of the equipment on-site, and commissioning and acceptance taking place by late May 2010.

Technically, Rocktec faced a wide array of challenges to comply with the performance requirements of the contract, as well as strict environmental, safety and standards compliance issues. The complete scope of supply complied with and surpassed all applicable Australian Standards.

Provisions were made to ensure that all lifting points were properly designed to suit the physically large and open hoppers, whilst corrosion protection was also a prerequisite in the design.

Conditions were imposed on time to manufacture, supply and install, as well as performance guarantees to a maximum of 7500 megatonnes per hour of iron ore. A design life of 25 years was also built into the design criteria and there had to be a 95 to 98 per cent operational availability on a 358 days per year operation (2575 hours per year), with an annual throughput in excess of nine million tonnes per annum (9MTPA).

An automated water spray/dust suppression system with additional sprinklers at transfer points was incorporated into each of the six hoppers, together with hoods to minimise dust emissions. The water supply, using fixed tension hose reelers on each unit, also comprised a wash-down function.

Removable enclosures/covers were included to reduce noise levels to below 85 decibels at a one metre distance.

Other operational conditions which had to be met included:

  • A standard hopper design to permit hopper interchangeability in case of damage.
  • Hopper and transfer points design to cope with extremely abrasive material, with the potential for handling high percentages of fines in some products.
  • An interface with prescribed definitions of feeder types, and the inclusion of a facility for access to skid steer loaders for spillage clean-up from the loading process. This condition dictated the maximum height of hoppers to avoid building ramps. The slope angle of the hoppers had to enable complete self-emptying to avoid any contamination between changes of material being handled.
  • The conveyor system was designed to handle high impact loads, maintain high capacity at high levels of availability, and the inclusion of effective skirting, ensuring low levels of maintenance.
  • Each feeder (a Rocktec XHD apron feeder for each of the six hoppers) is capable of 2500 tph sustained capacity at 100 per cent speed and each incorporated 20 to 100 per cent speed variability. Provision was made for each hopper to be discharged even in the event of a feeder failure. Dribble conveyors were supplied with each feeder to collect any fines spillage between the pans.
  • Redundancy of key components was built into the design in all areas ito allow for operation in the event of a component failure.

Each train is equipped with a dedicated Motor Control Centre (MCC), with electrical supply provided through a trailing cable for power, and fibre optic cable for communications. Each MCC, being air-conditioned, dust proof, insulated and sound proof, provides a safe, comfortable working environment, and is positioned clear of the hopper area to avoid damage from falling ore. Each MCC incorporates an on-board PLC, with a control philosophy providing interlocked operational and safety functions, remote emergency stops and lock-out facilities for maintenance. Visual operational devices, such as beacons, have been included, as well as external lighting aimed at the hopper area. Full instrumentation, with visual and audible alarms, has been incorporated into the controls.

As summarised by Neil Parker, managing director of the PINC Group and project manager of the Utah Point Berth Project: ?We required infrastructure to facilitate loading out at 7500 tph a wide range of ores in an environmentally challenging application. Under a fixed lump sum design, fabrication and supply contract, Rocktec delivered on time two unique rail mounted hopper trains that were assembled and commissioned with relative simplicity and performed to expectation. It was a breath of fresh air to work with a vendor that got on with the job without fuss and delivered above expectation on a part of the project that presented potentially significant risks.?

Source: Rocktec Australia

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