The April issue of IM includes the penultimate article on PT Freeport Indonesia (PTFI) and looks at oreflow to the concentrator and overburden handling. Obviously an operation of this size employs hundreds of kilometres of conveyor belt. Cleaning those belts properly is vitally important and relies on Martin Engineering belt cleaners.
The Upper Ore flow requires 13 separate conveyors, 11 2,134 mm belt width conveyors rated at 9,300 t/h and two 6,800 t/h, 1,829 mm conveyors. Four of the 18 Lower Ore Flow conveyors are 2,134 mm belt width conveyors rated at 9,300 t/h and the other 14 are 6,800 t/h, 1,829 mm conveyors. Overburden handling employs two 2,134 mm belt width conveyors rated at 10,000 t/h and four 2,134 mm grasshopper conveyors rated at 10,000 t/h.
Martin Engineering through its Indonesia joint-venture partner and distributor PT Suprabakti Mandiri (Supra) provides belt cleaning systems and cleaner maintenance services for these. Five years ago, Martin Engineering was one of several cleaning systems suppliers to Freeport Indonesia.
Martin belt cleaners were used in the North/South concentrators (IM May 2010) and Oreflow areas; equipment from other suppliers was used on the belts in the operation’s three SAG mills. But in a move to simplify its supplier arrangements and improve maintenance, PTFI solicited plans to consolidate cleaning systems while providing installation and service. An international team from Martin Engineering spent a week at the Grasberg site. The team, with personnel from company headquarters in Neponset, Illinois, and from the business unit in Brazil, worked with Supra personnel to prepare a detailed site survey. This report reviewed every conveyor and belt cleaning system in the Grasberg operation, and discussed the cost of carryback in similar, large-scale operations and the benefit of outsourcing the specialised cleaner maintenance work.
Supra now services most of the conveyors at the operation with belt cleaning systems and other components. These conveyors are high output, severe-duty systems. The belts in the Oreflow and SAG mill areas are typically 1,800 to 2,100 mm in width, and operate at 4 m/s, with carrying capacities of 10,000 t/h. Together, Supra and Martin Engineering have made a number of improvements to the belt cleaning systems to upgrade efficiency, including:
■ Installing water sprays on some wide belts to improve cleaning
■ Installing pressure rollers above tertiary cleaners to reduce belt dynamics
■ Unifying the cleaning systems to improve consistency and manage spare parts.
In unifying the operations on Martin Engineering cleaners, Supra has now ‘systemised’ the operation’s conveyors with pre-cleaning, secondary cleaning and tertiary cleaning systems. Pre-cleaners are installed on the face of the head pulley, below the material trajectory; secondary cleaners are typically installed at the point where the belt is leaving the head (discharge) pulley.
The belt cleaners installed were selected to minimise the differences in systems while matching the requirements of each conveyor’s specifications and material conditions. Typically, the equipment includes an SHD (Super Heavy Duty) precleaner for high speed/high tonnage conveyors, or an XHD (Extra Heavy Duty) precleaner on medium-speed belts. A Martin Orion Belt Cleaning Systems® ORION-2000 secondary cleaner, and a Martin SQC2T cleaner are used as the tertiary system.
Supra has a team of service technicians permanently based at the mill site. Led by an engineer/planner, this crew is charged with servicing all the belt cleaners from Oreflow to the Mill. Other Supra personnel maintain the cleaners at the port site.
The Supra belt maintenance and cleaner service crew now work as part of the PTFI maintenance team. All the belt cleaner service is left to the Martin Engineering/Supra crew, from planning, adjustment, and blade change-out. Grasberg has scheduled shutdowns, and incorporates belt cleaner installation and maintenance tasks into the total shutdown plan.
With the systemisation of cleaners and the outsourcing of cleaner maintenance, the operations have noted significantly reduced levels of carryback. This provides the additional benefits of an improvement of component life and the reduction of cleanup labour.
There are still challenges, but working together, Martin Engineering, Supra, and PT-FI anticipate continued improvement in the performance and life of belt cleaners and other conveyor components, resulting in reduced fugitive material and improved conveying for the Grasberg operations.
