In this article, a simplified fluid-dynamic model was developed to identify the basic parameters for the design and operative setting of an olive oil decanter. The working principle of the decanter is based on the centrifugation of malaxed olive paste, which allows separation of the solid particles in the paste from the liquid phase. The model analytically describes the operating principle of an olive oil decanter, a radio‐axial machine in which the mass flow of the olive pomace follows a helicoidal path determined by the relative motion of the bowl and the screw conveyor. The model is thought to be self consistent and easy to engineer. This result was accomplished by including the main design and operative parameters of olive oil mill working phases (crushing, malaxing, and extraction) as well as olive composition and physical properties (density and viscosity). As a result, the model allows one to apply to olive oil decanters the same design and operating procedures typical of all fluid based machines, which exploit a set of machine characteristic curves provided by the equipment manufacturer.