sigma-mixer-design-construction-operation-applications

In operation, material is loaded through the top of the container to typically 40 to 65 percent of the mixer’s total volumetric capacity. The rotation of the blades is through heavy duty drive systems typically consisting of a motor, gearbox, couplings, and gears.

The tip speed of the sigma mixer is generally limited to 60 metres per minute. Mixing may be carried out at ambient temperature or under controlled temperature conditions.

The mixer troughs can be provided with jackets for circulation of hot or cold media to maintain the required temperature conditions within the mixer.

The discharge of the material from the mixer container is either by tilting of the mixer container , bottom discharge valve (see figure 5), or through an extruder / screw located in the lower portion between the two trough compartments .

The mixer may be equipped with any one of these discharge arrangements.

The tilting discharge arrangement is most common. The tilting arrangement of the container may be designed for manual operation or may be mechanized using motorized or hydraulic arrangement.

For materials of lower viscosity, the bottom discharge valve may be provided on the mixer trough. The design profile of the valve should be flush with the mixer trough to avoid any dead or unmixed pockets of material).

The extruder/screw discharge has an advantage that materials can be directly discharged, extruded, in the required shape or size for further processing.

In addition, the screw design eliminates operator exposure to hot materials if the mixing processes are carried out at high temperatures and/or with materials that are toxic in nature.