Three-screw pump

The main structure and working principle of the triple-screw pump: A triple-screw pump is primarily composed of a bushing (pump cylinder) fixed within the pump body, as well as an active screw mounted in this pump cylinder and two passive screws that mesh with it. Three intermeshing screws form a sealed chamber within the pump cylinder at each pitch, thereby creating a seal between the suction and discharge ports. When a triple-screw pump is in operation, since the two driven screws engage with the driving screw in a symmetrical manner on both sides, the radial forces acting on the driving screw are completely balanced, and the driving screw does not experience any bending load. The radial force acting on the driven screw is supported by the pump cylinder liner along its entire length; therefore, there is no need for an additional bearing at the outer end, and it essentially does not experience any bending loads. During operation, an oil film formed between the outer surface of the screw and the inner wall of the pump cylinder prevents direct contact between the metals, thereby **reducing** wear on the screw teeth. When a triple-screw pump is in operation, suction and discharge pressures act on both ends, thereby generating an axial thrust on the screws. For small pumps with a pressure difference of less than 10 kilogram-force/cm2, thrust bearings can be used. Furthermore, high-pressure oil is introduced to the bottom of each screw shaft sleeve through the central oil hole of the driving screw, thereby generating a counteracting thrust at the lower end of the screw that is opposite to the direction of the axial thrust. Like other positive displacement pumps, when the discharge outlet of a screw pump is completely closed, the pressure inside the pump rises to a level that can damage the pump or overload the motor. Therefore, a safety valve must be installed at the suction and discharge ports of the pump. The shaft seal of a triple-screw pump is usually a mechanical shaft seal, and different types can be used depending on the operating pressure.

Can the medium temperature cause the screw to lock up? Here, two screw pumps were damaged due to high oil temperatures; upon inspection, it was found that the rotors had locked up

The rod in the middle drives the two adjacent ones