Electromagnetic flowmeter use of common failures

Common faults in the use of electromagnetic flowmeters and clever solutions:

Common faults in the use of electromagnetic flowmeters, some are caused by damage to the components of the instrument itself, and some are due to improper selection and improper installation. Faults caused by factors such as improper operation, environmental conditions, fluidity, etc., such as display fluctuations, reduced accuracy, or even instrument damage. It can generally be divided into two types: faults that occur during installation and debugging (faults during commissioning) and faults that occur during normal operation (faults during operation).

(1) Faults during debugging. Debugging expects faults to generally occur during the instrument installation and debugging phase. Once eliminated, they will generally not reoccur under the same conditions in the future. Common faults during commissioning are generally caused by improper installation, environmental interference, and fluid effects. 1. In terms of installation, faults are usually caused by incorrect installation positions of electromagnetic flow sensors. Common problems include installing the sensor at a piping point where gas is likely to accumulate; or installing it on a vertical pipe from top to bottom, which may cause emptying; or There is no back pressure behind the sensor, and the fluid is directly discharged into the atmosphere, resulting in a non-full tube in the measuring tube.

2. Environmental aspects are usually mainly caused by stray current interference in pipelines, strong electromagnetic wave interference in space, magnetic field interference from large motors, etc. For stray current interference in pipelines, satisfactory results can usually be obtained with good single grounding protection. However, if a strong stray current is encountered (such as electrolytic workshop pipelines, sometimes the peak AC potential Vpp induced on the two currents can be as high as 1V), it is still possible to obtain satisfactory results. Additional measures and flow sensors and pipe edges need to be taken. Space electromagnetic wave interference is generally introduced through signal cables and is usually protected by single or multi-layer shielding.

3. In terms of fluids, the measured liquid contains evenly distributed tiny bubbles, which usually do not affect the normal operation of the electromagnetic flowmeter. However, as the bubbles increase, the instrument output signal will fluctuate. If the bubbles are large enough to cover the entire electrical surface, As the bubbles flow through the electricity, the electrical circuit will be instantly disconnected and the output signal will fluctuate even more. When an electromagnetic flowmeter with low-frequency square wave excitation measures slurry with excessive solid content, it will also produce slurry noise, causing the output signal to fluctuate. When measuring mixed media, if the flow sensor is entered for measurement before the mixture is uniform, the output signal will also fluctuate. Improper matching of electrical materials and measured media will also affect normal measurement due to chemical effects or chemical phenomena. Electrical distribution materials should be selected correctly according to instrument selection or relevant manuals. 2. Faults during operation: Faults during operation are faults that occur after the electromagnetic flowmeter has been debugged and operated normally for a period of time. Common faults during operation are generally caused by factors such as the adhesion layer on the inner wall of the flow sensor, lightning strikes, and changes in environmental conditions. 1. Adhesion layer on the inner wall of the sensor. Since electromagnetic flowmeters are often used to measure dirty fluids, after running for a period of time, an adhesion layer will often accumulate on the inner wall of the sensor and cause failure. These failures are often caused by the conductivity of the adhesion layer being too large or too small. If the attachment is an insulating layer, the electrical circuit will be open and the instrument will not work properly; if the conductivity of the attachment layer is significantly higher than the conductivity of the fluid, the electrical circuit will be short-circuited and the instrument will not work properly. Therefore, the electromagnetic flow meter should be cleared in timeThe attached scale layer inside the measuring tube. 2. Lightning strikes Lightning strikes can easily induce high voltage and surge current in instrument circuits, causing damage to the instruments. It is mainly introduced through power lines or excitation coils or flow signal lines between sensors and converters, especially the majority of them introduced from the control room power lines. 3. Changes in environmental conditions. During debugging, because the environmental conditions are good (for example, there is no interference source), the flow meter works normally. At this time, it is often easy to ignore the installation conditions (for example, the grounding is not very good). In this case, once the environmental conditions change and new sources of interference appear during operation (such as electric welding on the pipeline near the flow meter, large transformers installed nearby, etc.), it will interfere with the normal operation of the meter and the output of the flow meter. The signal will fluctuate.