Circular arc gear pump rely on the work of the pump cylinder and the meshing gear formed between the volume change and movement to transfer liquid or make the pressure booster pump. Outer meshing double gear pump structure. A pair of intermeshing gears and pump cylinders separate the suction chamber from the discharge chamber. When the gear rotates, the volume of the tooth between the tooth on the suction side and the tooth on the tooth side gradually increases and the pressure decreases, and the liquid enters the space between the teeth under the pressure difference. As the gear rotates, liquid between the teeth is brought to the discharge chamber. At this time, the volume between the teeth on the discharge side of the tooth on the side of the cavity is gradually reduced, and the liquid is discharged. Gear pump is suitable for conveying non-solid particles, non-corrosive, large viscosity range of lubricating liquid. Pump flow to 300 m 3 / hour, the pressure up to 3 × 107 Pa. It is commonly used as a hydraulic pump and delivery of various types of oil. Gear pump structure is simple and compact, easy to manufacture, easy maintenance, self-priming capacity, but the flow, pressure pulsation and noise. The gear pump must be fitted with a safety valve to prevent damage to the pump or prime mover if the outlet pressure of the pump exceeds the allowable pressure for some reason, such as blockage of the discharge pipe. Circular arc gear pump is a kind of positive displacement pump, which consists of two gears, the pump body and the front and back covers. When the gear rotates, the volume of the space on the side of gear disengagement increases from small to large to form a vacuum, , The volume of the space on the meshing side of the gear changes from large to small, and the liquid is squeezed into the pipe. The suction chamber and the discharge chamber are separated by the meshing line of two gears. The pressure at the outlet of the gear pump depends entirely on the resistance of the pump.