RR and RRH pumps are P.D. twin-screw pumps, designed and manufactured according to API 676 standards. They represent the result of over one century’s experience in the design of this technology. The two rotors are machined from a single-block piece, and the intermeshing screws provide a synchronous operation thus balancing the axial hydraulic trhusts. The screw bearing housing can either be internal or external in a wide variety of configutations according to customer requirements. Screw motion is trasferred by a coupled timing gear located inside one of the bearing housing. This configuration prevents metal-to-metal contact and resultant wear between the pump screws and provides a synchronous yet rotation of the screws.