Electromagnetic flowmeter in the water plant the right way to use

　　1. Selection of caliber and range

　　The transmitter caliber is usually selected to be the same as the pipeline system caliber. If the pipeline system is to be designed, the caliber can be selected according to the flow range and flow rate. For electromagnetic flowmeters, a flow rate of 2-4m/s is more suitable. In special cases, such as when there are solid particles in the liquid, considering the wear, a common flow rate of ≤3m/s can be selected. For fluids that are easy to attach to management, a flow rate of ≥2m/s can be selected.

　　The range of the transmitter can be selected according to two principles: one is that the full scale of the instrument is greater than the expected maximum flow value; the other is that the normal flow is greater than 50% of the full scale of the instrument to ensure a certain measurement accuracy.

　　2. Choice of temperature and pressure

　　The fluid pressure and temperature that electromagnetic flowmeters can measure are limited. When selecting, the operating pressure must be lower than the working pressure specified by the flowmeter. At present, the working pressure specifications of electromagnetic flowmeters produced domestically are: less than 50mm diameter, the working pressure is 1.6MPa, 900mm diameter, the working pressure is 1MPa, greater than 1000mm diameter, the working pressure is 0.6MPa.

　　3. Selection of lining material and electrode material

　　The lining material and electrode material of the transmitter must be correctly selected according to the physical and chemical properties of the medium, otherwise the instrument will be quickly damaged due to corrosion of the lining and electrode, and the leakage of highly corrosive media is likely to cause accidents. Therefore, the materials of the electrode and lining must be carefully selected according to the specific measurement medium in the production process.

　　Installation of electromagnetic flowmeter

　　①The transmitter should be installed in a dry and ventilated place indoors. Avoid installing it in places where the ambient temperature is too high. It should not be subjected to strong vibrations. Try to avoid equipment with strong magnetic fields, such as large motors, transformers, etc. Avoid installing it in places with corrosive gases. The installation location should be convenient for maintenance. This is the environmental condition to ensure the normal operation of the transmitter.

　　② In order to ensure that the measuring tube of the transmitter is filled with the measured medium, the transformer is installed vertically and the flow direction is from bottom to top. Especially for liquid-solid two-phase flow, it must be installed vertically. If only horizontal installation is allowed on site, it must be ensured that the two electrodes are on the same horizontal plane.

　　③ Valves and bypasses should be installed at both ends of the transmitter.

　　④ The millivolt AC potential measured by the electrodes of the electromagnetic flow transmitter is based on the liquid potential in the transmitter. In order to stabilize the liquid potential and keep the transmitter and the fluid at the same potential to ensure stable measurement, the transmitter housing and both ends of the metal pipe should be well grounded, and the converter housing should also be grounded. The grounding resistance should not be greater than 10, and it cannot be shared with the grounding wire of other electrical equipment. If it is not possible to ensure that the transmitter housing is in good contact with the metal pipe, use a metal wire to connect them and then reliably ground them.

　　⑤ In order to avoid interference signals, the signals between the transmitter and the converter must be transmitted using shielded wires. It is not allowed to place the signal cable and the power line in parallel in the same cable steel pipe. The length of the signal cable shall generally not exceed 30m.

　　⑥The installation location of the converter should avoid strong AC and DC magnetic fields and vibrations, the ambient temperature should be -20 to 50°C, it should not contain corrosive gases, and the relative humidity should not exceed 80%.

　　⑦ In order to avoid the influence of the relative measurement of flow velocity, the flow control valve should be set at the downstream of the transmitter. For small-diameter transmitters, because the distance from the center of the electrode to the inlet of the flowmeter is equivalent to several times the length of the diameter D, there is no requirement for the upstream straight pipe. However, for flowmeters with larger diameters, there should generally be a straight pipe section of more than 5D upstream, and there is generally no requirement for a straight pipe section downstream.