Twin Screw Pumps are rotary, positive displacement pumps with capability of handling various clean liquids without containing solids. The pump is made of two sets of opposed screws. During pump running, the screws on the two shafts are engaged, and form sealed cavity with the surrounding pump casing. The pumped liquid are shifted axially as the screw shafts turn and steadily and constantly conveyed to the center of the pump where the discharge port is located. Since hydraulic forces on two screws are opposite and equal, the hydraulic axial stress on shafts are automatically balanced.