To produce high-quality rock products, intensive and effective scalping of the raw material upstream of the primary crusher is very important. In both companies, there was a need for improvement to increase the screening rate and quality. Besides the effective and clogging-free scalping, the focus was on reducing the load on the primary crusher with a heavy-duty, load-independent screening system.
The family-run company Gebr. Arweiler contracted the HAVER NIAGARA GmbH with the planning and execution of a complete primary crushing installation incorporating the tried and tested NIAGARA® eccentric screen. The around 50-year-old primary crusher with a free-vibrating screen as a scalper no longer met today‘s requirements with regard to operational reliability and quality.
The new primary crusher consists of the main components feed bin, a push feeder, eccentric screen, jaw crusher, flip-flow screen, steel engineering and various troughed belt conveyers. Some components of the old primary crusher like, for example, bin and jaw crusher were taken over for use in the new facility. The plant engineering and complete assembly round off the complete package for the installation of a modern plant.
The feed rate at the bin amounts to around 300 t/h at a max. edge length of 1 100 mm for the raw material. The feed material is fed by means of a HAVER push feeder onto a HAVER® double-deck eccentric screen, type DSS 1400 x 4800/3500. The upper deck reduces the load on the downstream jaw crusher by scalping at around 100 mm. The lower deck of the scalper screens off screenings and stony soil at around 32 mm. The scalped material is then rescreened on an equally newly installed flip-flow screen at around 5 mm, to improve the quality of the chippings. Alternatively, the scalped material 0 – 32 mm can be stockpiled.
The new precrushing unit was built in a classical, very stable and maintenance-friendly design. As a result, products of higher quality thanks to the lower filler content are produced. The professional and high-calibre planning, assembly and commissioning of the new equipment convinced Gebr. Arweiler‘s direct neighbour, the company Hartsteinwerke Johann Düro in Taben-Rodt. HAVER NIAGARA GmbH was contracted to supply a classical HAVER® eccentric screen and a hydraulic push feeder.
The supplied eccentric screen type DSS 1600 x 4600/3000 replaces the existing technology and guarantees reliable and safe operation of the installation. The feed rate here is up to 750 t/h, the edge length of the feed material measuring up to 1 200 mm. In the upper deck, the crusher load is reduced at around 150 mm while on the lower deck, scalping at around 56 mm is performed. Since their commissioning, the two load-independent HAVER scalpers on the bank of the River Saar have fulfilled their purpose to the fullest satisfaction and improved the product quality at these two family-run companies.
A vibrating screen equipped with an eccentric drive produces an almost uniform circular motion of the screen box. Such vibrating systems therefore work independently of load and are predestined for high feed rates even with intermittent material feed. Eccentric vibrating screens have proven efficient for the following purposes:
Capacity increase of an existing primary crusher with retrofitting of a scalper
Reduction of load on the downstream crusher by screening off of the material smaller than the crusher discharge particle size
Screening off of the overburden (loamy or clayey constituents) from the feed material with the use of a scalper in double-deck design
Screening off of foreign material in combination with loading and filling equipment
The use of eccentric vibrating screens is also advantageous
to reduce the load on the secondary crushing stage,
with widely varying feed throughputs and feed sizes
and for difficult-to-screen materials, i.e. wet or sticky feed materials.