A marine twin screw pump is a kind of rotary positive displacement pump, contains a pair of rotating shafts, mostly used to transder L.O.
Although each pumping screw may be pressed onto and pinned to its shaft, a one-piece rotor design in which the screw is an integral part of the shaft is frequently used in high-pressure or high-horsepower application. Loads applied to the pump’s rotors are generally absorbed by bearings located at both ends of each shaft. Torque from the pump shaft that is coupled to the driver is often transmitted to the idler shaft through timing gears. The pump’s bearings and timing gears are sometimes located within the casing where they are lubricated by the pumped fluid. With this design, only one shaft seal is required to prevent leakage at the point where the driven shaft penetrates the casing. If the pumped liquid is not a suitable lubricant,however,bearings and timing gears must be usually installed in separate housings located outside the pumping chamber and lubricated with oil supplied from an independent source. Four seals are required in a twin screw pump with external bearings and timing gears to seal the openings where the shafting penetrates the casing. Because contact between the screws and the casing cannot always be avoided, the tips of the threads and the bore of the casing are sometimes coated with various wear-resistance materials.
