Overhung impellers are mounted on the extreme end of the shaft in a cantilevered condition hanging from the support bearings. They are also subdivided into a class known as motor-pumps or close-coupled pumps where the impeller is directly mounted onto the motor shaft and supported by motor bearings. Overhung impeller pumps are frequently used in pumping stations for pumping clear water, wastewater and thin sludge. This impeller is normally open type to achieve high tip speeds with low stress levels and high-pressure ratios per stage. Each impeller inlet is coaxial whereas the outlet is tangential. They are also used to protect the bearings whenever the fan handles hot, dirty or corrosive gas.