The metering pump is driven by the motor shaft to rotate the worm gear, which decelerates the main shaft and eccentric wheel to rotate and operate, and drives the tappet to move back and forth in the guide cylinder. The tappet, together with the diaphragm, gradually forms a vacuum in the pump chamber through the action of a one-way valve, and the suction valve opens (at this time, the discharge valve closes) to suck in the liquid; When the diaphragm moves forward, the suction valve closes and the discharge valve opens. The liquid is discharged under the push of the diaphragm, and after continuous reciprocating operation, there is pressure to form a quantitative discharge of liquid. The selection of it is very strict. Below, the metering pump manufacturer will provide you with a detailed introduction.

List basic data:

1. Characteristics of the medium: medium name, specific gravity, viscosity, corrosiveness, toxicity, etc.

2. What is the particle diameter and content of the factor contained in the medium.

3. Medium temperature: (℃)

4. The required flow rate for industrial pumps can generally ignore the leakage rate in the pipeline system in the process flow, but the impact of process changes on flow rate must be considered. If agricultural pumps use open channels for water transportation, leakage and evaporation must also be considered.

5. Pressure: suction pool pressure, drainage pool pressure, pressure drop (head loss) in the pipeline system.

6. Pipeline system data (diameter, length, type and number of pipeline accessories, geometric elevation from suction tank to pressure tank). If necessary, a device characteristic curve should also be made.

7. When designing and arranging pipelines, the following precautions should be taken:

A. Reasonable selection of pipeline diameter. With a larger pipeline diameter, at the same flow rate and lower liquid flow velocity, the resistance loss is small. However, with a higher price and smaller pipeline diameter, the resistance loss will increase sharply, leading to an increase in the head of the selected pump, an increase in belt power, and an increase in both cost and operating expenses. Therefore, a comprehensive consideration should be given from both technical and economic perspectives.

B. The discharge pipe and its fittings should consider the maximum pressure they can withstand.

C. The pipeline layout should be arranged as straight as possible, minimizing the number of accessories in the pipeline and minimizing the length of the pipeline. When turning is necessary, the bending radius of the elbow should be 3-5 times the diameter of the pipeline, and the angle should be greater than 90 ℃ as much as possible.

D. The discharge side of the metering pump must be equipped with valves (ball valves or shut-off valves, etc.) and check valves. Valves are used to adjust the operating point of the pump, and check valves can prevent the pump from reversing when the liquid flows back, and prevent the pump from being hit by water hammer. (When the liquid flows back, a huge reverse pressure is generated, causing pump damage)

Determination of metering pump flow rate, head flow rate

a. If small, normal, and large flow rates have been provided in the production process, the maximum flow rate should be considered.

b. If only normal flow rate is provided in the production process, a certain margin should be considered. For ns>; A pump with a large flow rate of 100 and a low unintentional head, with a flow margin of 5%, is suitable for ns<; For small flow high lift metering pumps with a flow margin of 50, a flow margin of 10% should be taken. For pumps with a flow margin of 50 ≤ ns ≤ 100, a flow margin of 5% should also be taken. For pumps with poor quality and poor operating conditions, a flow margin of 10% should be taken.

c. If the basic data only provides weight flow rate, it should be converted to volumetric flow rate.