The structure of the three-screw pump


It is mainly composed of a bush (pump cylinder) fixed in the pump body, a driving screw inserted in the pump cylinder and two driven screws meshing with it. Three mutually meshing screws form a sealed cavity according to each lead in the cylinder of the three-screw pump, resulting in a sea

It is mainly composed of a bush (pump cylinder) fixed in the pump body, a driving screw inserted in the pump cylinder and two driven screws meshing with it. Three mutually meshing screws form a sealed cavity according to each lead in the cylinder of the three-screw pump, resulting in a seal between the suction and discharge ports.

 

When the three-screw pump is working, since the two driven screws are symmetrically meshed with the driving screw, the radial forces acting on the driving screw are completely balanced, and the driving screw does not bear bending load. The radial force of the driven screw is supported by the pump cylinder bushing along its entire length. Therefore, there is no need to install a bearing at the outer end, and basically it does not bear the bending load. During operation, an oil film formed between the outer surface of the screw and the inner wall of the pump cylinder can prevent direct contact between metals and greatly reduce the wear of the screw tooth surface.

 

When the three-screw pump is working, the suction and discharge pressures of the liquid are acting on the two ends respectively, so an axial thrust is generated on the screw. For small pumps with a pressure difference of less than 10 kgf/cm2, thrust bearings 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 active screw, thereby generating a balanced thrust opposite to the axial thrust at the lower end of the screw. The screw pump is the same as other positive displacement pumps. When the discharge port of the pump is completely closed, the pressure in the pump will rise to the dangerous degree of damage to the pump or overload of the motor. Therefore, a safety valve must be installed at the suction and discharge port of the pump.

 

The shaft seal of the three-screw pump usually adopts a mechanical shaft seal, and it can take different forms according to the working pressure.

28 Views

Read more