Twin Shaft Mixers

Bennett Twin Shaft Compulsory mixers are designed for use in areas where large amounts of concrete are required to be mixed thoroughly in the shortest possible time. Typically they are used on infrastructure projects for roads, dams, power plants and large multi-storey buildings. Two synchronized counter-rotating shafts and intermeshing blades cause an intense shearing action on the mix especially in the region of the mixer where the blades on either shaft intermesh. Twin shaft mixers are available is sizes from 750 up to 9000 litres of dry unmixed material and with a maximum aggregate size of 150mm.

The mixing tub is lined with wear resistant liners of varying hardness and thicknesses depending on the size of the mixer and the end user's requirements, from 10mm Hardox 400 to 17mm thick Ni-Hard. Mixing blades are available in 16mm Hardox 400 to 27mm Ni-Hard. The number of blades, their orientation and position combine to produce the ultimate mixing action with the minimum of wear on the blades and tub liners.

The two counter-rotating shafts have power transmitted to them by two highly efficient, epicyclic planetary gearboxes that are kept synchronized by a separate synchronizing shaft. Power is provided to the gearboxes via belt drives from either one or two electric motors depending on the size of the mixer. Bearings that support the shafts are isolated from the mixing tub seals so that, even in the event of the seals failing, the bearings will still be protected.

The hydraulically powered mixer discharge door opens the complete length of the mixing tub for rapid discharge. It can be opened to either the right or left so that concrete can be discharged to two different points without having to resort to a distributing belt conveyor.

Bennett Twin Shaft mixers can be supplied with a variety of options including:

• Automatic centralized greasing unit for the main shaft bearings
• High pressure washing system
• Skip loading hoist
• Aggregate surge hopper
• Cement and water weigh hoppers
• Concrete discharge chute
• Support trestles, maintenance platforms and stairways

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