Selection of metering pumps
First, determine the pressure: the rated pressure of the selected metering pump is slightly higher than the actual maximum pressure required, generally 10 to 20% higher. Don't choose too high, too much pressure will waste energy, increase equipment investment and operating costs. 2. Determine the flow rate: The selected metering pump flow rate should be equal to or slightly larger than the required flow rate of the process. The use range of the metering pump flow rate is preferably 30 to 100% of the rated flow rate of the metering pump, and the repeating reproduction accuracy of the metering pump is high. Considering the economical and practical, it is recommended that the actual required flow rate of the metering pump be 70 to 90% of the rated flow rate of the metering pump. Third, determine the pump head (hydraulic end) material: After the specific model specification of the metering pump is determined, and then select the material of the over-current part according to the properties of the over-flow medium, this step is very important. If improperly selected, it will cause corrosion damage of the medium. Overcurrent components or media leaks contaminate the system, etc. In serious cases, it may also cause a major accident.Other aspects: When selecting a metering pump, you also need to consider the accuracy level of the metering pump required. The higher the level of accuracy, the higher the investment. The general working temperature of the metering pump is -30~100°C, and the special metering pump has a wider working temperature range (such as the high temperature liquid metering pump with insulation jacket, the conveying temperature can reach 500 °C). For the particle size of the medium, it should be less than 0.1mm. For media larger than 0.1mm, the overcurrent structure of the pump can be changed to meet the needs. For the viscosity of the medium, generally should be 0 ~ 1000mm / s, the special metering pump can reach 6000 mm2 / s, the flow rate of the mechanical diaphragm metering pump is the maximum flow measured under the rated pressure (water delivery at room temperature) When the pressure drops, the output flow rate will be higher than the calibration.
Characteristic measurement range: 0-400 liters / hectare
Pressure range: 0-1.0 MPa
Drive mode: motor drive
Control mode: manual, automatic control (can receive 4-20mA signal to adjust the flow)
1. Cast aluminum housing, high heat dissipation performance, light overall weight, suitable for all kinds of acid and alkali liquid, non-toxic and tasteless.
2, the use of cam mechanism. There is no leakage at all and it can be placed on the tank or pipeline.
3. The contact medium pump head is made of PVC, optional PTFE, and stainless steel.
4, cost-effective, generally applicable to the water treatment industry with low pressure requirements.
5. The flow can also be adjusted arbitrarily or quantitatively when the pump is running or stopped.
6. The diaphragm is pressed into a multi-layer composite structure, the first layer of super-tough Teflon acid-resistant film, the second layer of EPDM elastic rubber, the third layer of thickness supporting iron core, the fourth layer is reinforced with reinforced nylon fiber, and the fifth is EPDM. Elastic rubber is fully wrapped to increase diaphragm life.
Comparison of characteristics of different types of metering pumps
Plunger metering pump
1, the price is lower
2, the flow rate can reach 76 m 3 / hour, the flow rate is in the range of 10% to 100%, the measurement accuracy can reach ± ​​1%, and the pressure can reach 350 MPa. When the outlet pressure changes, the flow rate is almost constant.
3, can transport high viscosity medium, not suitable for conveying corrosive slurry and dangerous chemicals.
4. The shaft seal is sealed by packing, there is leakage, and the packing needs to be adjusted periodically. Fillers and plungers are prone to wear and require pressure flushing and discharge of the packing rings.
5. No safety relief device.
mechanical
Mechanical diaphragm metering pump
1. The price is lower.
2, no moving seal, no leakage.
3, can transport high viscosity medium, abrasive slurry and dangerous chemicals.
4. The diaphragm is subjected to high stress and the diaphragm life is low.
5, the outlet pressure is less than 2 MPa, the flow range is small; the measurement accuracy is ± 5%, when the pressure is from the minimum to the maximum, the flow change can reach 10%.
6, no safety relief device.
Hydraulic diaphragm metering pump
1. No moving seal, no leakage, safe relief device, easy maintenance.
2, the pressure can reach 35 MPa; the flow rate is in the range of 10..1, the measurement accuracy can reach ± ​​1%; for every 6.9 MPa increase in pressure, the flow rate drops by 5% to 10%.
3. The price is higher.
4. Suitable for medium viscosity media.
Bellows metering pump
1. The price is lower.
2, no moving seal, no leakage.
3. It is most suitable for conveying vacuum, high temperature and low temperature medium. The outlet pressure is below 0.4 MPa, and the measurement accuracy is low.
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