Rotary pumps that deliver or pressurize liquids by changing and displacing the working volume created by the pump cylinder and meshing gear. 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. Gear pump must be equipped with safety valve to prevent for some reason, such as the exhaust pipe plugging the pump outlet pressure exceeds the allowable value to damage the pump or the prime mover (a), the working principle: gear pump is a positive displacement pump, the two A gear, the pump body and the front and the back cover form two enclosed spaces. When the gear rotates, the volume of the space on the side where the gear is disengaged becomes larger and larger, forming a vacuum, sucking the liquid in, the volume of the space on the meshing side of the gear decreases from large to small, And squeeze the liquid 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. (B), operation and maintenance 1, start: (1) check before starting all flanges, joints of the tightness. (2) Disc drive coupling, no friction and collision sound. (3) The first start should be injected into the pump liquid. (4) should be fully open before inhalation and discharge of the valve in the pipeline, closed valve is strictly prohibited to start. (5) After verifying the direction of motor rotation, start the motor. 2, parking: (1) turn off the motor. (2) Close the pump inlet and outlet valves.