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Use and maintenance of precision gear metering pump


The precision gear metering pump is a kind of rotor pump in the displacement pump, which consists of a stationary pump casing and a rotor that rotates. It has no suction valve and discharge valve, relying on the rotor in the pump body and the liquid contact side of the energy in the form of static pressure directly on the liquid, and through the rotating rotor extrusion effect of the liquid discharge. At the same time, the space left on the other side to form a low pressure, so that the liquid continuous suction. The pressure head of the rotor pump is high, the flow rate is usually small, and the discharge is uniform, so it is suitable for conveying liquids with high viscosity and lubricity, but without solid particles.

precision gear metering pump

The working principle of precision gear metering pump

There are a pair of meshed gears in the pump, one of which is the active gear, the other is the driven gear, driven by the active gear mesh rotation. Gears and the pump, gears and gears between to leave a small gap. When the gears rotate in the direction, the teeth gradually out of mesh in the left side of the suction chamber, the volume between the teeth increases, forming a local vacuum, the liquid is sucked into the suction chamber under the action of the pressure difference. As the gears rotate, the liquid is pushed forward by the gears between the gears and the pump casing in two ways and sent to the discharge chamber on the right side, in which the volume becomes smaller due to the gradual engagement of the two gears, the pressure increases and the liquid between the gears is squeezed to the outlet. The gears keep rotating, and the liquid is continuously sucked in and discharged to achieve the purpose of conveying liquid. Therefore, the gear pump relies on the volume gap change of the gear workshop which is meshed with each other to complete the work of conveying liquid.

Outlet pressure of precision gear metering pump (p)

The outlet pressure of precision gear metering pump is the maximum outlet pressure allowed by the pump, which determines the strength of the pump body, the seal and the power of the prime mover.

The outlet pressure of precision gear metering pump in actual operation depends on the back pressure of the outlet piping and is required to be less than the maximum allowable outlet pressure of the pump. The outlet pressure of the gear pump is not more than 4MPa and the speed is 150~1450r/min.

Working characteristics of precision gear metering pump

(1) The theoretical flow rate Q of the gear pump is independent of the characteristics of the pipeline and depends only on the pump itself, while the pressure provided is determined only by the characteristics of the pipeline and has nothing to do with the pump itself. When the discharge pressure of the gear pump increases, the leakage loss inside the pump increases.


(2) The shaft power of the pump increases with the increase of the discharge pressure. The efficiency of the pump also increases accordingly. However, after the pressure exceeds the rated value, the efficiency decreases due to the increase of leakage in the pump.

(3) With the increase of liquid viscosity and gas content, the flow rate of the pump decreases and the efficiency decreases.

MRA Gear Pump / Micro Flow

(4) Gear pumps must be equipped with a safety valve.

(5) Gear pump flow cannot be adjusted by the outlet valve, often using the bypass adjustment, speed adjustment method to adjust the flow.

(6) Gear pumps do not need to fill the pump before starting, but be sure to open the outlet valve before starting.