MD, D, DG and DF pumps mainly consist of four major parts:stator, rotor, bearing and shaft seal; Stator part; it mainly consists of suction section, middle section,discharge section, guide vane and so on. Those sections are clamped by tension bolts to form a working room. The D pump's inlet is horizontal and its outlet is vertical; while the DG pump's both outlet and inlet are vertical. Rotor part: it mainly consists of shaft, impeller, balance disc,bushing and so on. The shaft transmits power to the impeller to make it work; the balance disc is used to balance the axial force; the shaft is .mounted with a replaceable bearing to protect it. Bearing part: it mainly consists of bearing seat body, bearing,bearing gland and so on. Both ends of the rotor are supported by two single-Tow roller bearings mounted inside the bearing body. Bearings are lubricated with grease. Shaft seal: the soft packing seal is adopted, which mainly consists of' packing box body, packing, water fender and other parts on the water inlet section and the tail hood. Water with a certain pressure is filled into the seal cavity for the purpose of water seal, cooling and lubrication. The water for water seal of the D pump is from the pressure water inside the pump while that of MD, DF and DG pumps from the external water supply. Besides, DG and DF pumps can adopt the mechanical or float ring seal. . Drive: the pump is driven directly by the motor through the elastic coupling, which rotates clockwise when seen from the motor end.