A mixer is a device that is used in process technology to disperse, suspend, homogenize or emulsify substances or to generate flows, e.g. in basins, in which the generated flow is to prevent a sedimentation. Other applications of mixers are mixing and adding solids, liquids, and gases in or to a fluid or recirculating phase mixtures. Submersible mixers are equipped with a propeller and a submersible motor, but there are also variants with dry installed motor and open shaft. Mixers are installed on the floor or on a wall. The choice of mixers depends particularly on the medium to be mixed. Mixers are used, e.g. in wastewater treatment plants or biogas installations.