A mixing unit is essential for mixing emulsions and grinding solutions. By means of two needle valves, the ARIANA Duo Mixing Unit permits fast and precise adjustment of the emulsion concentration of liquid coolants and lubricants. In this way, it is pos-sible to produce liquids using optimum concentrations. The Duo Mixing Unit has one water inlet and two concentrate inlets. Once the optimum mixing ratio has been determined, the user can always rely on this ratio being the case. Of course, it is possible to change the mixing ratio at any time. For safety reasons, a return valve is installed on the water inlet side to prevent any suctioning into the potable water system. Unlike the Mono Mixing Unit, the Duo Mixing Unit has two concentrate inlets. This makes it possible to mix two different concentrates without having to reposition the mixing unit.