Agitated film evaporators are used in the processing of very viscous and fouling liquid foods, or suspensions of particulates, which cannot be handled in normal tubular or plate evaporators. The main feature of these evaporators is a rotor within the evaporator body, which agitates the viscous fluid, improving heat transfer and preventing fouling. Various types of low-wear rotors are used: fixed, scraping, or hinged. In the vertical units, the vapor/liquid separator and the motor can be placed either at the top or at the bottom of the unit. The agitated film units are often used in combination with tubular film evaporators, when a very high concentration of solids is required. The evaporation surface of agitated film evaporators is limited, due to mechanical limitation. In contrast, tubular evaporators can be constructed with a large number of tubes, i.e. large evaporation surfaces. In the vertical-type agitated film, the rotor can be removed by a hydraulic lift for inspection or repairs.