Knowledge of screw pumps, introduction to principles, classification, and structural forms | Principles

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1. Screw pump: A screw pump is a new type of pump that operates on the principle of rotary meshing positive displacement. Its main working components are an eccentric screw (rotor) and a fixed sleeve (stator). Due to the special geometric shapes of the stator and rotor, separate sealing chambers are formed; the medium is pushed to flow uniformly in the axial direction. The internal flow velocity is low, the volume remains constant, and the pressure is stable, thus preventing the formation of vortices and turbulence. In addition, the stator of screw pumps is made from a combination of various elastic materials, which gives them significant advantages over conventional pumps when it comes to transporting high-viscosity fluids, media containing hard suspended particles, or media containing fibers. As a result, screw pumps are widely used in sand-producing wells and heavy oil wells. 2. Classification of screw pumps ► By the number of screws: 1) Single-screw pump – a pump in which a single screw rotates by meshing with the internal threaded groove of the pump body ； 2) Twin-screw pump – a pump that transports liquid through the intermeshing of two screws ； 3) Multi-screw pump — a pump in which multiple screws mesh with each other to convey liquid. ►Classified by screw suction method: 1) Single-suction type: The medium is sucked in from one end of the screw and discharged from the other end ； 2) Double-suction type: The medium is drawn in from both ends of the screw and discharged from the middle. 3. Classified by pump shaft position: horizontal pumps, vertical pumps. 3. Screw pump drive and structural types: There are various ways to drive pumps; common options include direct connection to a low-speed motor (6-stage, 8-stage), drive by a gear-reduced speed motor, and drive by an infinitely variable speed motor. Transmission can be achieved through direct coupling, or by using speed-regulating motors, V-belts, gearboxes, and other devices for speed control. 4. Working principle of the screw pump: When the motor drives the pump shaft to rotate, the screw rotates around its own axis while also rolling along the inner surface of the sleeve, thereby creating a sealed chamber within the pump. With each rotation of the screw, the liquid in the sealing chamber is pushed forward by one pitch. As the screw continues to rotate, the liquid is forced in a spiral manner from one sealing chamber to another, and eventually is expelled from the pump body.