Metering pump basics


Metering pumps are pumps designed to meter liquids. Most metering pumps use the structure of a plunger pump and a diaphragm pump. They are also useful for gear pumps because they can maintain a constant flow regardless of the discharge pressure. There are two types of metering pump: adjustable flow rate and non-adjustable flow rate. The former has wider applicability. The flow is mainly adjusted by changing the stroke length, such as changing the crank radius, the position of the back dead center when the plunger returns, and the gap between the plunger rod and the cross head. The flow can also be adjusted by changing the number of reciprocations or using both methods. Although the stroke length can be adjusted from zero to the maximum, in order to ensure the measurement accuracy, it is generally limited to the range of 30 to 100%.

的 The metering accuracy of the metering pump refers to the accuracy of flow reproducibility, which is usually calculated based on the maximum flow rate. Within the range of 10 to 100%, the metering accuracy of general metering pumps is ± 1% (special metering pumps have higher accuracy). The main factors affecting the measurement accuracy are the tightness of the plunger packing and the integrity of the suction and discharge valves.

Plunger metering pump has the advantages of high metering accuracy, wide adjustment range and high pressure, but there is a leak at the packing seal, which will affect the meter's metering accuracy after the packing is corroded and worn. The flow rate of this metering pump is generally 4 to 4000 liters / hour, and the pressure is generally below 5 × 105 Pa.

The main advantage of the diaphragm metering pump is that there is no leakage, so it is particularly suitable for places where leakage is not allowed, such as conveying flammable, explosive, toxic and radioactive media. It can also be used to convey liquids containing solid particles, so it has developed rapidly. . Such metering pumps generally have flow rates below 2500 liters / hour and pressures up to 35 MPa.

The use of metering pumps can complete three functions of transportation, metering and adjustment, thereby simplifying the production process, realizing automation and semi-automation, and improving product quality. With multi-cylinder or multiple metering pumps, several media can also be fed into the reactor in exact proportions for mixing.

Plutonium metering pumps are increasingly used in chemical, oil refining, pharmaceutical, food and nuclear energy industries. The efficiency of metering pumps is low, generally 20%, and the power is very small.