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BHS-Sonthofen: New twin-shaft mixers for dry building materials

At BAUMA 2013, BHS-Sonthofen unveils twin-shaft mixers of the new DMX series. They are adapted to the special requirements of mixing dry materials, such as cement, dry mortar, bonding compounds and dry shotcrete.

The new mixers are specially tailored to the production of dry material mixtures. They are suitable for mixtures containing all manner of aggregates, cement, small dry components, plastic fibers and cellulose. With an extensive modular system and various options, they can be customized to the products of the user, from fine-grained materials such as cement to mortar mixtures with coarse particles up to 8 mm in size. BHS offers a range of machines with throughput rates of up to 300 t per hour.

Compared with single-shaft mixers, they offer considerably better mixing with short mixing cycles. Furthermore, the DMX mixers are more compact than single-shaft mixers and also represent good value for money.

Mixers from BHS have proven their worth in numerous applications in the cement industry and in the production of dry mortar. One recent example is the replacement with a BHS mixer of an intensive mixer in a dry mortar plant.

Homogeneous mixtures

BHS has developed the DMX series on the basis of the twin-shaft batch mixers, which have been used in thousands of concrete mixing applications.

The mixing mechanism consists of mixing tools that are arranged in the form of a discontinuous spiral on each of two counter-rotating mixing shafts. They generate a three-dimensional spiral motion with intensive exchange of material in the turbulent zone of overlap between the two mixing cycles. Counterblades positioned at the ends of the shafts deflect the material in such a way that all material is repeatedly routed back into the mixing process. Due to the three-dimensional motion and the recirculation of the material, there are no dead zones anywhere in the mixing trough, unlike with single-shaft mixers.

Thanks to the sophisticated mixing mechanism with the directed three-dimensional motion pattern, the speed of the mixer can be less than that for comparable single-shaft or intensive mixers while still producing a greater mixing effect. This considerably reduces the energy consumption and is also gentler on sensitive components in the material to be mixed, such as perlite, styrofoam or expanded clay – the particles are not crushed.

Compared with other mixing systems, twin-shaft mixers are filled to a much greater extent, making them more compact for a comparable throughput rate. In the case of new plants, these mixers are thus ideal because of their small dimensions; for modification to existing plants, they allow the installation of a more powerful mixer in the existing space.

Custom adaptation

Since dry building materials encompass a wide range of aggregates, cements and admixtures, different application-specific drive variants are available for the mixers with different speeds and different mixing tools. These can be individually configured according to the application, e.g., for abrasive or adherent input materials.

Due to the very good mixing effect, agitators, which generally have high power consumption and rates of wear, only need to be used for their actual intended purpose: disintegrating undesired agglomerations.

An optional sampling device is available, allowing the quality of the mixture to be checked at any time.

Residue-free discharge

Since many manufacturers produce different products in succession, a residue-free discharge of the trough is important. In the case of the DMX, this is carried out by means of large, hydraulically operated discharge door wings that are available in two variants for fine and coarse-grained mixture products. The discharge door wing for fine-grained mixtures has a seal to prevent fine-grained materials, such as cement, from escaping; it is also waterproof.

The mixing shafts are fitted with special sealing air seals.

Excellent resistance to wear

Depending on the abrasiveness of the mixture, various wear liners are available. All wearing parts in the mixer, such as mixing arms or blades, are screw-fitted and are thus easy to adjust or exchange. This simplifies maintenance and increases the availability of the plant.

Tests in our BHS technical center

Every dry material mixture has different characteristics; for this reason, BHS conducts tests at its in-house technical center on request. These tests give the customer the certainty that his outlay is well invested and that the new plant is future-proof.

BHS-Sonthofen at BAUMA in Munich, April 15 to 21, 2013:
Hall B2, booth 325/420