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Turnkey conveying equipment for dynamic leach pad system

In 2003 the Chilean copper producer BHP Billiton was planning a new leaching system for the copper mine SPENCE in Northern Chile. In 2004 BHP charges FAM Förderanlagen Magdeburg with the turnkey erection of this complex system. For the planned commission by August 2006 FAM had to deliver and assemble about 7500 tonnes of materials handling technology including the trial operation. Despite this short period it succeeded completely with the result of a stable copper production since August 2006.

This characteristic Chilean technology of copper production is based on the leaching process of copper ore by requiring a systematically and technologically handling of huge bulk material masses. In addition to the required conveying systems and facilities the complex control engineering for the automatic operation mode had been delivered and installed by FAM Förderanlagen Magdeburg. While the FAM parent company in Germany engineered and manufactured the more complicated structural steel elements, basic steelwork was contracted out mostly to Chilean suppliers. The electrical and process control and instrumentation systems incorporating advanced features such as GPS, WLAN und ZEDAS, a complex condition and event monitoring facility, were developed and built by GPA, a Magdeburg based FAM subsidiary.

Crawler-mounted conveyor system with tripper car, 3,500 tonnes/h of copper ore

For leaching the produced copper oxides and sulfides, already crushed and pretreated, are discharged onto two separate large piles (2,5 x 1 km). These piles reach a maximum height of 10m. The leaching process is effected by acid, which is supplied via pipelines passing through the piles. It dissolves the copper contained in the ore. The acid is recovered in a drainage system and fed to the electrolysis plant where copper is extracted.
The SPENCE mine uses dynamic piles for an effective utilization of the huge stockyard area. The piles are continuously reclaimed after finishing the leaching and subsequently rebuilt with fresh or. The leached material „Ripios“ is conveyed to the final storage by a dumping system.

FAM’s scope of supplies included the following main items:

1 crawler-mounted stockpiling belt conveyor (300 m long) for the copper oxide pile
1 crawler-mounted stockpiling belt conveyor (425 m long) for the copper sulfide pile
1 crawler-mounted recovery belt conveyor (300 m long) for the copper oxide pile
1 bucket wheel reclaimer
1 spreader on crawlers
1 belt wagon on crawlers
4 stationary conveyor systems, total length 5,700 m
1 shiftable conveyor system, 950 m long
5 tripper cars
2 hopper cars

Stockpiling system

Ore is crushed and chemically preconditioned at the agglomeration plant and subsequently conveyed by a longitudinal conveyor to the stockpile.
A tripper car transfers the material supplied by the belt conveyor running along the pile to a crawler-mounted conveyor system, which moves along the length of pile. This in turn carries a tripper car with a cross belt for stockpiling the material systematically in one line after another. This way continuous operation is ensured and the required highly accurate pile shape (achieved with GPS control) is built up.

Depending on the material to be conveyed it is fed either to the oxide pile with a width of 245m or to the sulfide pile with a width of 375m.
For operation on the sulfide pile, the tripper car is switched over to through delivery. As a result, the material is delivered to a second belt conveyor running along the pile. The further operation is effected as mentioned above.

Crawler-mounted conveyor system with tripper car, 3,500 tonnes/h of copper ore

Both piles have a designed stacking capacity of 3,500 tonnes/h and an average rated capacity per day of 50,000 tonnes of copper ore.
After stacking the final length of pile, the crawler-mounted conveyors swing round in a half circle to the side opposite the belt conveyors running along the piles and continue operation. In doing so, these crawler-mounted conveyors traverse the underfloor sections of the belt conveyors running along the piles in a clockwise direction.
The specific design of the crawler-mounted conveyors makes few demands on subgrade building. The crawler-mounted conveyors of the SPENCE project include novel function and control principles applicated for the first time. Individual crawler undercarriages now incorporate new features, which make it easy to compensate differences in level and inclination in every direction. The positions of the entire mobile conveyor can be adjusted at any time, even lengthwise. The system is insensitive to temperature so that belts run with a high degree of reliability.

Reclaiming system

FAM bucket wheel reclaimer – compact design, capacity 4,000 tonnes/h Ripios

After a procedural caused idle period the leached ore is reclaimed for dumping on a final pile.
During reclaiming operation, a bucket wheel reclaimer picks up the leached ore in bench-type operation, line after line. Via mobile hopper car the ore is transferred over a crawler-mounted conveyor system to the belt conveyor running along the pile to take the material away.

After a procedural caused idle period the leached ore is reclaimed for dumping on a final pile.
During reclaiming operation, a bucket wheel reclaimer picks up the leached ore in bench-type operation, line after line. Via mobile hopper car the ore is transferred over a crawler-mounted conveyor system to the belt conveyor running along the pile to take the material away.

Pile reclamation using bucket wheel reclaimer and crawler-mounted belt conveyor

Copper ore stockpiling and the subsequent pile reclamation are continuous and dynamic processes. In practice, new ore is piled on the same pile shortly after spent material has been reclaimed so as to make efficient use of available pile capacity.

When they reach the end of a pile, the crawler-mounted conveyors swing round in a half circle to the side opposite the belt conveyors running along the piles and continue operation. In doing so, these crawler-mounted conveyors traverse the underfloor sections of the belt conveyors running along the piles in a clockwise fashion.
The specific design of the crawler-mounted conveyors makes few demands on subgrade building. Individual crawler undercarriages now incorporate new features, which make it easy to compensate differences in level and inclination in every direction. The positions of the entire mobile conveyor can be corrected at any time, even lengthwise. The system is insensitive to temperature so that belts run with a high degree of reliability.

Maintenance and service

FAM mobile compact spreader for "Ripios“ dumping, 4,000 t/h

The leach pad system for copper oxide at the SPENCE mine has given reliable operation since August 2006. The agreed performance data has been achieved. In the meantime copper sulfide system and conveying route for Ripios are in full operation.

The entire facility has been designed for easy maintenance, with a high level of component standardization to reduce the number of spare parts to a minimum. This includes individual parts, drive assemblies and even complete undercarriages.

Diagnostic data for the most important drive assemblies is centrally collected by a teleservice station as a base for ZEDAS, a condition and event monitoring system, which uses these system parameters (transmitted by WLAN) to calculate servicing intervals and data for necessary maintenance and repairs, and even forecasts potential defect spots. Faults can also be diagnosed retroactively.

A CCTV (Closed Circuit Television) system has been installed using a large number of Ethernet-capable cameras and workstations, which are linked via another wireless network. The images of each camera are fed to the network and may be recorded or reproduced at any internal or external workstation.

A three-year maintenance contract for the facility described has been awarded to the Chilean company FAM América Latina Ltda., a wholy owned subsidiary of FAM GmbH.