The Helico-Axial Pump design has been used successfully around the world and is the proven option for subsea multiphase boosting.
The Twin Rotor Pumps have been available for ages and they are typically used for pumping heavy crude oils and emulsions. The adaptation to multiphase pumping has required considerable engineering that is on going. There are many examples of successful applications of twin rotor design to multiphase services. The challenge remains in producing a reliable non-contacting rotor design for higher differential pressures and flow rates.