Intelligent Electromagnetic Flowmeter Five Steps to Solve the Zero Instability Analysis In industrial production, the electromagnetic flowmeter is often unstable. The reasons for this problem are various. According to the technicians of Mingyu Automation Equipment for many years. Experience, there are mainly the following factors:
1. The pipeline is not filled with liquid or contains bubbles in the liquid. Objectively, there is no activity in the flow sensor, and there are practical activities in the flow.
2. If the valve is used for a long time or the liquid is dirty, the valve will be sealed tightly, which will lead to zero instability.
3. The liquid conductivity changes or is uneven. When it is at rest, the zero point will change, and when it is active, the output will be shaken.
4. Because the scale of the inner wall and the level of electrode contamination are not complete and symmetrical, the equilibrium of the initial zero setting is destroyed.
5. The change of the state of the power equipment near the flow sensor (such as the increase of leakage current) constitutes the change of the ground potential, which will also cause the zero point change of the intelligent electromagnetic flowmeter. Through the analysis of the problem, we can find the corresponding solution according to the corresponding phenomenon.
Electromagnetic flowmeter zero drift control First, the inspection is excluded: Check the program to check the unstable process of the zero point intelligent electromagnetic flowmeter. Firstly, make a preliminary investigation and judgment according to the process, and then carefully check and try to eliminate the faults. The order of order of the item is:
(1) It can be observed or asked to understand that there is no need for a large operation, that is, it is difficult to be easy afterwards;
(2) According to the past on-site maintenance experience, the frequency of occurrence is higher and the probability of occurrence in the future is higher;
(3) Check the sequence requirements required by itself. If the preliminary investigation confirms the cause of several failures after the team is completed, it can also be carefully examined in advance.
Second, the intelligent electromagnetic flowmeter sensor is not perfect according to the ground, such as stray current and other external interference: Pipeline stray current and other external interference affect the main electromagnetic flowmeter good grounding protection, usually requires the grounding resistance is less than 1000, do not share with his motor Grounding. Sometimes the environmental conditions are good, the intelligent electromagnetic flowmeter can work normally without grounding, but once the good environment does not exist, the instrument will malfunction, and then the inspection will bring the state of the power equipment near the troublesome flow sensor. Changes (such as increased leakage current) form a change in ground potential, which causes a zero point change in the intelligent electromagnetic flowmeter.
Third, the intelligent electromagnetic flowmeter liquid (such as liquid conductivity uniformity, electrode contamination and other issues); liquid conductivity changes or uneven, will change the zero point when stationary, the output will shake the output. Therefore, the flowmeter position Keep away from the injection point or downstream of the chemical reaction section of the pipeline. The flow sensor should be installed upstream of these places. If the liquid contains a solid phase, or impurities deposit on the inner wall of the measuring tube, or scale on the inner wall of the measuring tube, or the electrode is contaminated by grease. Etc., there may be zero variation. Because the surface fouling of the inner wall surface and the degree of contamination of the electrode may not be exactly the same and symmetrical, destroying the balance of the initial set-off setting of the plant. Active measures to remove the fouling and sediment layer; If you have little change, you can try to re-zero.
Fourth, the electromagnetic flowmeter signal loop insulation decreases. The signal loop insulation will form a zero point instability. The signal loop insulation is reduced due to the soil, and the insulation of the pole portion is caused by the drop, but the signal cable and its terminal insulation cannot be excluded. Falling or destroying. Because sometimes the site environment is very harsh, a slight negligence in the instrument cover/wire connection is inadvertently sealed, and the moisture mist or dust particles are infiltrated into the instrument junction box or cable protection layer, so that the insulation is lowered. The insulation resistance check is carried out according to the two side points of the cable side and the flow sensor side, and is tested with a megger. The signal cable can be easily used first. The flow sensor is divided into two times: the liquid is filled with the surface contact resistance of the electrode and after the tube is filled. Measurement, U-pole insulation resistance.
5. Check the electrode contact resistance and the electrode insulation resistance in 2 steps.
(1) Fill the liquid measuring electrode surface spoon liquid contact resistance flow sensor to remove the signal cable wiring, use a multimeter to measure the resistance between each electrode and the grounding point, the left electrode should be between 10% and 20%. The measurement of "one/electrode contact resistance" in Section 9 will be further explained.
(2) Empty tube measurement electrode insulation venting measuring tube, dry cloth on the inner surface, after completely drying, use H500VDC megohmmeter to measure the resistance between each electrode and ground, the resistance must be above 100MΩ. Under normal circumstances Through the above five steps of inspection and operation, the zero instability can be basically solved.
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