在安装、接线完毕后，正式投入运行之前，应该检查以下安装、接线是否正确，电磁流量计是否能正常工作。 After the electromagnetic flowmeter is installed and connected, and before it is officially put into operation, you should check whether the following installation and wiring are correct and whether the electromagnetic flowmeter can work normally.
It must be emphasized here that for some units that lack experience in use, flowmeter installation and operation personnel should carefully read the relevant technical descriptions in the relevant electromagnetic flowmeter installation and operation manuals, and be good at analyzing and thinking about problems encountered during the initial operation. . The electromagnetic flowmeter has been adjusted and calibrated on the flow calibration device of the manufacturer. As long as the matching numbers of the sensors and converters and the meter coefficients are correct, they can generally be put into operation without any adjustment. Otherwise, the original adjusted flowmeter will be messed up.
投入运行前，流量计测量管必须充满实际测量介质，通电后在静止状态下进行零点调整。 Before the electromagnetic flowmeter is put into operation, the flowmeter's measuring tube must be filled with the actual measurement medium. After the power is turned on, the zero point adjustment is performed in a static state. After being put into operation, it is necessary to periodically stop the flow to check the zero point according to the medium and the use conditions. Especially for non-clean media that is prone to precipitation, easy to pollute the electrode, and contains solids, it should be checked at the beginning of operation to gain experience and determine the normal inspection cycle.
For qualified users, several basic parameters of the sensor should be measured and recorded before the instrument is put into operation.
1. Insulation resistance of the electrode (when the sensor is empty, the two resistances to the instrument case or the ground insulation resistance);
2. Insulation resistance of the excitation coil (insulation resistance of the excitation coil to the instrument case or ground);
3. The cold resistance value of the excitation coil (ie the copper resistance value of the excitation coil enameled wire);
4. The contact resistance of the electrode is filled with liquid. Measure the resistance between the electrode and the ground. The contact resistance of the two electrodes should be approximately the same.
These data are very useful for analyzing the cause of sensor failure after a period of operation. For example, when the contact resistance of two electrodes changes, it means that the electrode is likely to be contaminated; the contact resistance becomes larger, and the contamination may be an insulating deposit; the contact resistance becomes smaller, and the contamination may be a conductive deposit The contact resistance of the two electrodes is asymmetric, indicating that the two electrodes are not contaminated to the same degree; the decrease in the insulation resistance of the electrode and the excitation coil indicates the degree of moisture in the sensor; when the insulation resistance drops to a certain level, it will affect the normality of the electromagnetic flowmeter jobs. The cold resistance value of the field coil is a parameter to check whether the field coil is normal.
的调试要注意以下几个方面： Pay attention to the following aspects when debugging the electromagnetic flowmeter :
1. In fluid, the liquid contains uniformly distributed small bubbles, which usually does not affect the normal measurement. However, when the measured volume flow is the sum of both liquid and gas, the output signal will fluctuate due to the increase of the bubble. If the bubble is too large to flow through the electrode to cover the whole The electrode surface makes the electrode signal loop momentarily open, and the output signal will have greater fluctuations.
When two or more liquids are used in the pipeline mixing process, if the conductivity of the two liquids (or their respective potentials with the electrode chapters) is different, they will enter the flow sensor for flow measurement before the mixing is not uniform, and the output signal will also fluctuate.
Low-frequency (50/16 ～ 50 / 6Hz) rectangular excitation electromagnetic flowmeter will measure slurry noise when the solid content in the liquid exceeds a certain content, and the output signal will fluctuate to some extent.
Improper selection of electrode material and measured medium will cause chemical effects such as passivation or oxidation, the formation of insulating films on the electrode surface, and electrochemical and polarization phenomena, which will prevent normal measurement.
2. The piping system and installation are usually failures caused by the incorrect installation position of the electromagnetic flowmeter sensor. Commonly, the flow sensor is installed at the high point of the pipeline network where it is easy to accumulate retained gas; the back pressure of the flow sensor, and the liquid is directly discharged into the Atmosphere, forming a non-full pipe in its measuring tube; installed on a vertical pipe from top to bottom, may cause emptying and other reasons.
3. The environmental aspects are mainly the stray current interference of pipelines, electromagnetic interference in space, and magnetic field interference of large motors. Pipeline stray current interference can usually be achieved by taking a good separate grounding protection. However, if the pipeline has a strong stray current (such as the electrolytic workshop pipe), it may not be overcome, and measures must be taken to isolate the flow sensor from the pipe. Space electromagnetic wave interference is generally introduced through signal cables, and is usually protected by single-layer shielding, but it has also been encountered that shielding protection cannot be overcome.