Marine gear pump is a kind of rotary positive displacement pump with two meshing gears as moving elements, there are external-gear pumps and internal-gear pumps, today, the external-gear pumps have been widely used on board.
marine gear pump mainly comprises of drive gear, idle gear, drive shaft, idle shaft, shaft seal and bearings. In and external-gear pump, the two pumping gears, which can be of the spur, helical or herringbone design, are mounted on parrallel counter-rotating shafts. Torque from the drive shaft to the idler can be transmitted through the meshing teeth pf the two pumping gears. In addtion, the bearing are typicallly mounted at both ends of each shaft.
Fluid entering a gear pump is trapped within the cavities formed between the teeth of two meshing rotating gears and is forced through a close-clearance casing. The meshing teeth of the two gears separate the suction port from discarge port. As the gears rotate, cavities formed between the teeth of two meshing rotating gears are filled with liquid at the suction port and trapped liquid will be dicharged at the discharge port.
Because gear pump has too many friction surfaces, it is generally used to deliver lubricating liquid.
There are axial and radial clearances in the pump. The axial clearance is the clearance between the face and the cover of the pump. The radial clearance is the clearance between the top of the teeth and inner wall of the pump’s casing. Internal leakage due to the axial clearance takes up about 80% of the total leakage. Internal leakage due to radial clearance takes up about 10%~15% of the total leakage. Leakage also occurs between the meshing lines of teeth.
The rotary direction of the driving shaft should be kept correctly, otherwise, the flow direction will be reversed.
