Two-Screw, Low-Pitch, Screw Pump:

The two-screw, low-pitch, and screw pump consists of two screws which mesh along with close clearances, mounted on two parallel shafts. A single screw has a right-handed thread and another screw has a left-handed thread. A single shaft is the driving shaft and drives the other shaft by a set of herringbone timing gears. The gears serve to manage clearances among the screws as they turn and to promote quiet operation. A screw rotates within closely fitting duplex cylinders which have overlapping bores. Whole clearances are small, other than there is no actual contact among the two screws or among the screws and the cylinder walls.

Figure: Two-Screw, Low-Pitch, Screw Pump

The fully assembly and the common flow path are displays in Figure. Liquid is trapped at the outer end of every pair of screws. As the first space among the screw threads rotates away from the a one-turn, opposite screw, spiral-shaped quantity of liquid is enclosed while the end of the screw again meshes along with the opposite screw. Since the screw continues to rotate then the entrapped spiral turns of liquid slide along the cylinder toward the middle discharge space although the next slug is being entrapped. Every screw functions same, and every pair of screws discharges an equivalent quantity of liquid in opposed streams toward the center, therefore eliminating hydraulic thrust. A removal of liquid from the suction end through the screws generates a reduction in pressure that draws liquid by the suction line.