The multiphase pump of twin-screw is positive displacement type, Twin-screw multiphase pumps work with fixed displacement pump chambers, where each chamber, formed when the two meshing screws rotate, delivers a constant volume from inlet to outlet. In order to compress gas, the liquid phase of the multiphase flow becomes very important. The twin-screw pump uses two opposing sets of screw profiles to move inlet flow from opposite ends of the screw sets towards the middle where it discharges to the pump outlet. Using rotational speed of the screws, centrifugal forces will cause the liquid phase to split and separate from the gas phase. As a result, the liquids will concentrate in the perimeter of the screw set and in the annulus between the liner and the screw tips and the gas along the root of the profile.

When the pressure increases from inlet to outlet, the liquid phase will become more defined and a laminar stream of liquid is formed along the screws tips moving in the opposite direction of the main flow stream from high to low pressure. As the liquid reaches and fills the next upstream pump chamber, it will compress the gas collected in the core of each chamber. Overflow liquid will continue to fill the next upstream chambers and gas is compressed as the liquid continuously fills the chambers. This process continues as long as the screws rotate; the re-combined liquid and compressed gas will reach the outlet of the pump and continue to move downstream. Although the twin-screw multiphase pump is a constant displacement machine, the back flow of liquid makes it a virtual variable displacement pump thereby allowing it to compress gas.

A typical multiphase twin-screw pump skid system consists of a twin-screw pump, electric motor applicable for VFD, common baseplate for pump, motor and piping, variable frequency converter, control system and junction box, strainer and pressure relief valve, forced lubricating system, external API flushing system for shaft double-mechanical seal, vibration, temperature and condition monitoring system, flexible coupling with non-sparking guard.