Rosi’s reunion with her grandson, Svenja’s breather in the park, and Jakob’s sand castle … they all depend in some way on stones. Without gravel, chippings and sand, railroad tracks couldn’t be laid, parks couldn’t be built, and sandpits couldn’t be filled. Machinery from thyssenkrupp Industrial Solutions makes it possible to crush rocks of all kinds – from limestone to the hardest basalt.
To cushion the enormous forces and vibrations on railway lines, the tracks are laid on a bed of ballast – known as the permanent way. As a rule hard rock such as granite, basalt or diabase is used. The all-important factor here is particle shape and size. To ensure the individual stones lock together and form a secure bed, they need to have suitable edges and a minimum particle size of around 30 millimeters. Smaller stones could be easily swept away by fast traveling trains. Crushed rock is also used in the construction of roads. To ensure the road surface can withstand the tons of traffic, the subsoil first has to be secured with a bed of gravel or sand. Aggregate with or without a binder is used to form the road surface. Stone materials in different gradations are also needed to create long-lasting paving and pathways in gardening and landscape construction.
From boulder to grain of sand
To break rock into the required particle size, extremely tough and powerful machines are needed. They are classified into primary, secondary and tertiary crushers. For large boulders up to 2.5 cubic meters in size, gigantic primary crushers are used. Gyratory crushers, jaw crushers and impact crushers from thyssenkrupp Industrial Solutions can break this kind of material into stones with an edge length of no more than 120 millimeters – at a rate of up to 13,000 tons per hour. For pre-crushed rock between 150 and 280 millimeter edge length, secondary crushers are needed. They break the material into stones no more than 35 millimeters in size. Tertiary crushers are used to produce finer material such as chippings and sand: 20 millimeter feed is broken down into grains less than four millimeters in size. With the variopactor®, thyssenkrupp Industrial Solutions has developed a special impact crusher for tertiary crushing which with its modular design can adapt to a wide variety of applications. Fitted with different combinations of rotors, aprons and milling beams, it can produce gravel, chippings or sand. The material is fed via an inlet into the crusher and comminuted by the blow bars fixed to the rotor and the adjustable aprons. The crushed material is then discharged through an outlet at the bottom of the machine. Optional milling beams can be used to produce cubic crushed material which is as crack- and stress-free as possible – particularly important for use in road construction and as an aggregate in concrete.
The special feature of the variopactor® is its symmetrical design, which allows the rotor to be operated in both directions. This has the advantage that the blow bars always operate with a sharp edge and need to be replaced or turned much less frequently. And the modular design of the variopactor means that over 95 percent of the wear plates are interchangeable. The apron and milling beam can be hydraulically adjusted from the outside at the push of a button to adapt the crushing chamber to individual requirements.