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Mixers are blending devices used in process engineering. Mixers consist of the following components: propeller, submersible motor and installation accessories. See Fig. 1 Submersible mixer

Other mixer types are driven by dry-installed standard motors and medium-exposed shafts.
Mixers are used for homogenising, emulsifying, dispersing, suspending and flow generation.

Main hydraulic tasks

  • Introducing and mixing various gases, liquids or solid substances into a fluid
  • Preventing conglomeration of sludge flakes
  • Circulating phase mixtures
  • Preventing sedimentation (in the case of insufficient fluid flow velocity in the tank)
  • Aligning the mixer to break up floating sludge layers

The applications and wide range of hydraulic tasks to be fulfilled by mixers entail different requirements for these machines. Assessment criteria include propeller diameters, thrust and the thrust/power ratio to ISO 21630.

Mixers are designed for stationary installation on the tank floor or tank wall, or for pedestal mounting. Specific propeller orientation helps create a circumferential flow. If required, several mixers should be installed in a tank.

Mixers are sealed to prevent ingress of water and come either in a close-coupled design or with gear unit. They are driven by three-phase asynchronous motors which are safe to run dry. The bearings used are maintenance-free rolling element bearings. Mechanical seals are used for sealing on both the product side and the drive end.

The propellers are designed with fibre-repellent, self-cleaning blades with backward curved incidence edges and are made of grey cast iron, stainless steel or a synthetic material depending on the fluid to be handled.

Mixers are installed via a guide bracket fitted to the mixer; it allows the submersible mixer to be lowered into the tank along a guide rail. The positioning of the mixer (including installation accessories) is performed in such a way that it is correctly orientated before being lowered into its working position in a mounting bracket. Appropriately designed installation equipment ensures that the forces developing during operation are transmitted to the tank floor.

A mixer can be withdrawn from the tank for repair and maintenance work at any time.