Mechanized limestone mining for cement production without blasting

In 2014 and first half of 2015, Trencor shipped a total of four T1460SM, 630Hp, mechanical drive Surface Miners to Indonesia to fill an order placed by PT. Semen Jawa (Siam Cement Group) from Thailand. They were looking to mine 2.4 million ton of limestone annually at their new Cement factory near Sukabumi, West Java, 139 km (68 mi) south of the national capitol Jakarta.

The 10-million-dollar investment for a fleet of four Trencor Surface Miners was part of a total 350-million-dollar investment to build the first SCG owned and operated cement factory in Indonesia as part of their South-East Asia strategic expansion plan.

One of the main issues they faced when planning the project was that traditional Drilling & Blasting would certainly lead to social unrest in the villages adjacent to the mining areas, especially as several villages where located very close to the boundaries of the mining site.

With SCG being a foreign investor, blasting was a sensitive issue, more so as the Sukabumi region is represented by many conservative non-government organizations (NGO), lobbying for the welfare and best interest of the local society in this highly populated West Java district.

At that time, the stringent government regulations around the applications for blasting permits as well as the risk of storing explosives and detonators on site was heightened by the growing Islamic state around the world.

Being a Royal Thai company, all SCG subsidiaries were directed to create a sustainable balance between Society, Environment, and bottom line profitability. The internal directive was to move away from the traditional Drill & Blast where possible but remain focused on maintaining balance and best practice.

A project team of six SCG senior mining engineers was tasked in 2012 to find a mining method to mine 2.4 million ton of limestone annually, without requiring a blasting permit. They had two objectives: First, the daily production needed to be guaranteed. Second, the operating cost had to remain cost competitive for the industry and conventional mining methods.

The project team concluded that using 3 Surface Miners and having one unit as back up in conjunction with a progressive mine-plan would enable SCG to avoid drill & blast and still meet their production and cost targets.

Choosing to produce the limestone with Surface Miners helped SCG to re-think and re-design the mining plan, resulting in reduced CAPIX, OPEX, and environmental impact.

Savings were achieved by centralizing the semi-mobile secondary impact crusher between the two mining areas, reducing the haul distance to a maximum distance of 400m from the mining areas. Reducing the haul distance lowered the number of dump trucks needed by 50% and avoided the investment in a large capital intensive (non-mobile) primary crusher.

A conveyor system was designed to connect the semi-mobile crusher with the limestone storage dome over a 3.5km distance. The semi-mobile crusher can be moved when new mining areas are opened once the existing mining areas are depleted, keeping the hauling distance to a minimum.

The following cost reductions have been achieved by utilizing Surface Miners and bringing the semi-mobile crusher closer to the mining area:

  • Reduction of hauling distance
  • 50% less haul trucks required
  • Reduced fuel consumption
  • Reduction in maintenance and tire consumption of the wheel loaders and dump trucks
  • Less capital investment
  • Reduction in labor cost
  • Higher overall efficiencies
  • No in-pit breaking required
  • Reduction in power consumption as only maximum 30% of the Surface Miner production needs to be crushed to minus 50mm
  • Stable high walls
  • Easier to rehabilitate the mining area

Trencor was awarded the order by SCG after a two-year process. During this period the SCG project team met and visited with the 4 leading manufacturers of Surface Miners and visited the sites where equipment was operational.  The project team concluded that the mechanical drive Trencor Surface Miner was the best suited Surface Miner, considering the steep terrain and the hardness of the limestone.

Points of Evaluation by the project team included:

  • Production capability and guarantees
  • Gradation of cuttings
  • Operating Cost
  • Lifetime of the Surface Miner
  • Ease of repair
  • Cutting depth
  • Expertise Trencor Sales and Service team

The first 3 Trencor Surface Miner where deployed 12 months prior to the start of the quarry operation to:

  • Create haul roads
  • Excavate the crusher area
  • Excavate parking areas
  • Create a slope for the construction of the conveyor landing area
  • Development of the mining areas

SCG has been extremely satisfied with the ease of operation, using the Surface Miners for Site preparation, moving them into production in August 2015, producing 10,000 tons of limestone daily at a cost competitive rate versus traditional drill & blast. The operation cost will further decrease once the softer calcareous deposits are reached. “SCG and PT. TSS appreciate the expertise of Trencor and the performance of the Trencor Surface Miners, in terms of its, production performance, reliability, technical services, part supplies, and fast response times” said Sitthipong Khunpirom, Director of PT. Tambang Semen Sukabumi, West Java Indonesia, A subsidiary of The Siam Cement Public Co. Ltd, “Trencor has been more than just an equipment supplier. It has been a trusted advisor from the early stages of exploration”