Structure of a Screw Pump

Structure of a Screw Pump

A screw pump is a type of positive displacement pump that uses one or more rotating screws to move fluid along the axis of the pump. The core structure mainly includes the pump casing, drive shaft, rotors (screws), bearings, and sealing system.

The pump casing forms a sealed chamber that guides fluid flow. Inside, one or more precision-machined screws are installed. In a single-screw pump, there is one metal rotor and a rubber stator. In twin or multi-screw pumps, multiple intermeshing metal rotors are used.

Working Principle

The working principle is based on axial fluid transport through rotating screw engagement. When the screw rotates, it creates sealed cavities between the screw threads and the casing (or between multiple screws). These cavities continuously move from the suction side to the discharge side.

As a result, the fluid is trapped in closed chambers and pushed forward smoothly, ensuring a continuous and pulse-free flow. This makes screw pumps highly suitable for handling viscous, shear-sensitive, or lubricating fluids such as oil, fuel, and industrial liquids.

Key Features in Operation

The screw pump operates with low vibration, stable flow, and high efficiency at varying pressures. Because the flow is not dependent on centrifugal force, it performs well even at low speeds and high viscosities.

Another important feature is gentle fluid handling, which prevents emulsification or damage to sensitive media. This is especially important in chemical, marine, and petroleum applications.

Summary

In essence, a screw pump works by converting rotational motion into smooth axial fluid movement through sealed screw chambers, ensuring reliable and continuous delivery.

References

• Hydraulic Institute Standards (HI)

• Pump Handbook, Igor Karassik et al.

• Karassik, I. J. Centennial Pump Handbook

• API 676 Rotary Positive Displacement Pumps Standard