The single screw pump is a single screw type delivery pump. Its main working parts are eccentric screw (called rotor) and screw sleeve (called stator) whose inner surface is double helix. Its working principle is that when the motor drives the pump shaft to rotate, on the one hand, the screw rotates around its own axis, on the other hand, it rolls along the inner surface of the bushing, thus forming the sealing cavity of the pump. Each time the screw rotates, the liquid in the sealing cavity is pushed forward by a screw pitch.

With the continuous rotation of the screw, the liquid is pressed from one sealing chamber to another in a spiral way, and finally squeezed out of the pump body. Screw pump is a new type of liquid conveying machinery, which has the advantages of simple structure, safe and reliable operation, convenient use and maintenance, continuous and uniform liquid output, stable pressure and so on. When the pump is working, the two driven screws are symmetrically meshed with the driving screw.

The radial force acting on the active screw is completely balanced, and the active screw does not bear bending load. The radial force of the driven screw is supported by the pump barrel bushing along its whole length, so there is no need to set another bearing at the outer end, which basically does not bear bending load. When working, the oil film is formed between the cylindrical surface of the screw and the inner wall of the pump barrel, which can prevent the direct contact between metals and greatly reduce the wear of the screw tooth surface.

Screw pump work, the liquid suction pressure and discharge pressure at both ends, so the screw to produce axial thrust. For small pump with pressure difference less than 10kgf / cm2, thrust bearing can be used. In addition, high pressure oil is introduced into the bottom of each screw shaft sleeve through the central oil hole of the transmission screw.

Thus, a balanced thrust opposite to the axial thrust direction is generated at the lower end of the screw. Like other positive displacement pumps, when the outlet of the pump is completely closed, the pressure in the pump will rise to the dangerous level of damaging the pump or overloading the motor. Therefore, the safety valve must be set at the suction and discharge of the pump.