New limestone crushing unit for Giant Keystone

Following the positive experience with Giant Cement at the Harleyville working site, Bedeschi America supplied a limestone crushing unit to Giant Keystone, Summerville SC/USA. It is a double crushing unit composed of two double-toothed roller crushers (Fig. 1, Table 1).These machines are ideal for use with this kind of processed material since they are particularly suitable for working also with very moist materials; in addition, they work at low speed rotation, which is extremely important to reduce the wear and tear as much as possible, especially taking into consideration the high abrasiveness of the material.
 
For the above-mentioned parameters the following machines have been selected:
–    a receiving hopper (volume of 110 m3) for discharge of ­material from trucks (Fig. 2), to unload from 3 sides
–    an apron feeder type CNA 10/2500B complete with scraper chain
–    a primary double-toothed roller crusher type RL 650/2500 with double rotor
–    a secondary double-toothed roller crusher type RL 450/2500
 
The technical data of the machines are summarized in Table 2.
 
The apron feeder is widely dimensioned to tolerate the stress due to the unloading of large-sized lumps. It is manufactured according to the standard Bedeschi technology. The bended blades apron feeders can be cleaned very well by means of a frontal blade scraper. Both the crushers are composed of two-toothed cylinders, with hardfaced teeth which are extremely important to limit wear and tear as much as possible, due to the abrasiveness of the material (Fig. 3). This type of technical solution facilitates the maintenance operations that can be performed without disassembling any of the components of the machines.
 
The two crushers are connected by a stationary screen. This connection makes it possible to select the material to be fed from the primary to the following secondary crusher, permit the fine material pass directly to the underlying belt and, at the same time, to optimize the positioning of the secondary crusher. The two crushers are in an easily accessible position; they are complete with wheels which can be moved (by means of an external device) to an even easier area for maintenance purposes. This is very important to have access to the rotors and to hardface the rotor teeth during the maintenance stages and to ensure a simple and safe method of operation. This aspect has to be particularly taken into consideration when material with high abrasive characteristics has to be processed. The selection of the above-mentioned machines ensures the achievement of a total reduction ratio of 1:12. The crushing unit is scheduled to be commissioned in late spring 2009.