Storage and homogenisation of various bulk materials form a significant integral part of the bulk handling processes within the overall logistics network.
Dynamic and efficient handling of the bulk materials requires the stockyards to be equipped with appropriate technology. The scope of a typical stockyard basically includes:
- Storage areas (reinforced to support the materials’ weight)
- Equipment for stacking and reclaiming the bulk materials
- Feeding and discharging belt conveyors
- Additional equipment such as sprinkling, de-dusting and fire-fighting systems.
When stockpiling operations require stacking and reclaiming to be performed at the same time, separate machines are absolutely necessary. However, in many applications simultaneous stacking and reclaiming are not required. This is when stacker-reclaimers, i.e., combined machines, become an excellent solution because their functional principle combines both types of operation.
The bucket wheel reclaimer with a reversible boom conveyor has proven to be an extremely functional, versatile machine. Stacker-reclaimers, as a rule, consist of a slewable superstructure and a rail-mounted sub-frame. Both the bucket wheel boom and the counterweight boom are hinge-mounted on the superstructure and guyed by ropes or tiebacks via a pylon. The bucket wheel boom is raised or lowered with the help of hydraulic cylinders or cable winches.
The machine can be operated also as a stacker with the belt direction reversed and the bulk material transported to the boom head where it is discharged. Similarly to a regular stacker, the stacker-reclaimer is fed via a tripper car. When the stockpile is being built, the bucket wheel remains in its rest position.
As the boom’s inclination can be adjusted and the boom itself can be slewed, it gives room for various methods of building bulk material stockpiles. The blending process or pre-homogenization within one stockyard facility is ensured by combining a specific type of stacking technology with a specific type of reclaiming technology.
Generally speaking, the material is stacked in consecutive layers, and depending on the type of reclamation, individual, several or all of the layers can be reclaimed at the same time. The efficiency of such a blending bed is expressed by the homogenizing effect, also known as the blending effect.
For stockpile reclaiming, the material is taken up by the bucket wheel, transported to the machine’s rotation center by the reversible belt conveyor, and dumped into the central chute, from where the material is transferred onto a discharging stockpile conveyor running between the rails of the reclaimer.
The reclamation process can be carried out in a bench-type or block operation. During the bench-type operation, after reaching the end of the stockpile, the reclaimer boom is lowered by a depth of cut and the reclamation process continues in the opposite direction. This procedure can be repeated until the stockpile is completely unloaded. In the block operation (reclamation at the face), the stockpile is reclaimed by the bucket wheel with the boom performing periodical, crescent-type slewing motions. Every time the slewing direction changes, the chip thickness is reset by the machine traveling a short distance further. The face reclamation has been found to be especially suitable for blending beds, which provide excellent homogenization of bulk materials.
Stacker-reclaimers are often designed for the handling of several different materials. This increases the flexibility of the storage location in terms of materials processing, in particular in port areas, enhances the attractiveness of the entire cargo handling complex.
FAM quality prevails. Customer-specific project designing and manufacturing of the systems and devices is one of the core competences of the FAM Group. After providing to the Australian coal terminal in 2010 four identical stacker-reclaimers each equipped with a 60m-long bucket wheel boom for the hard coal, FAM assembled and put into operation the 5th device of this kind in 2018.
For specific applications, FAM developed a range of other types of multifunctional stockyard systems. For example, portal scrapers can be also designed to work in both stacking and reclaiming mode. To this end, the portal scraper’s main boom works in reversible operation while the auxiliary boom is only used for reclaiming.