Mobile Sizer Station connecting to movable conveyor

In June 2002, two MMD 850 series Mobile sizing units were put into operation at the Lotschberg Rail base-tunnel in Switzerland (news item in 2002). These units were designed to be compact and flexible to allow the benefits of both short haul shovel and long haul conveying to be fully exploited in the tunnel, eliminating the problems, costs and safety implications incurred by using long haul truck and shovel operations.

Material entering Sizer

During the three years spent in the tunnel the Mobile sizer stations were used to process the as blasted material from the mine face (nominally 800mm), and reduce it to a 200mm product, discharging the sized material onto a long haul conveyor out to the surface to a concrete production plant. Tthe concrete produced at the plant was put back in the tunnel in the form of tunnel linings and platforms.

Mobile Sizer Station moving away from blast area and under the conveyor system

The mobile units followed the advance of the tunnel as it progressed, sizing mainly granite with small deposits of quartzite and gneiss at a throughput r ate of approximately 800TPH per sizer station. After all the blasted material had been processed, both the sizer and shovel were positioned away from the blast area and sited under a movable conveyor structure. The compact size of the sizer station allowed the drilling machine and various other machines to get to and from the mine face. After blasting had taken place the sizer station and shovel were located directly at the mine face ready for processing the material.

The tunnel is scheduled to come into operation in 2007 as a main route between Switzerland , Italy and countries to the north.