The transportation of mine products incurs a cost which can have a significant bearing on the competitive position of the product. This statement not only holds true for the transportation of the finished product but certainly as much for the in-plant haulage of the raw materials.
First of all, it should be differentiated between 3 categories of movable equipment.
a) The idea of a PORTABLE crusher is not new. Many such wheel-mounted installations are available but their size and capacities were mostly limited to 500 or 600 tph. Portable plants can be relocated -even over the road- from one quarry into another by simply hooking them on a trailor-truck.
b) Larger units can be mounted on skids or rail and are known as SEMI-PORTABLE. In some cases they require extensive preparation or partial dismantling for a relocation and are, therefore, used in mines or quarries where frequent relocation is not required.
c) As the word MOBILE already indicates, these plants move under their own power and may be mounted on crawlers or walking pads.
Loading costs are certainly also reduced by the use of movable precrushers since, according to Kochanowsky the volume loaded per hour by the shovel can be increased by as much as 50% through elimination of truck maneuvering and waiting time.
Of special interest to the minerals industry is the reduction of R.O.M. shot rock down to-1″ or -¾” as mill feed. Hard rock, however, can in the primary stage only be broken economically with jaw or gyratory crushers. One of the problems in the adaptation of gyratory crushers has been overall size and weight. In a new design a German manufacturer solved this problem and reduced the overall height by 40% without reducing the feed size.
Ground pressure of Mobile plants should not exceed 21 PSI when moving. A crawler mounted plant weighing 500 tons would require 350 sq.ft. of crawler plates on the ground. It is obvious that the surface of walking pads can be increased at less expense than crawlers.