Analysis of the causes of electromagnetic flowmeter failures during use and corresponding measures

1. Product Overview: As a type of flow measurement instrument with increasing usage in industrial production, electromagnetic flowmeter is not affected by the temperature, viscosity, density and conductivity (within a certain range) of the measured medium because its measurement results are not affected by the temperature, viscosity, density and conductivity (within a certain range) of the measured medium. Electromagnetic flowmeter can be used directly to measure the flow of other conductive liquids after being calibrated with water. There are also no throttling components that hinder the flow of fluid. Therefore, when the fluid passes through the flowmeter, it will not cause any additional pressure loss. It is one of the flowmeters with the lowest operating energy consumption. As a professional electromagnetic flowmeter company, Runzhong Instrument Technology has summarized a lot of experience in installation and maintenance of electromagnetic flowmeters over the years. We summarize the common faults of electromagnetic flowmeters, which can generally be divided into two types: faults that occur during installation and commissioning (commissioning period faults) and faults that occur during normal operation (operation period faults). Some are caused by damage to the components of the instrument itself, and some are caused by improper selection, improper installation, environmental conditions, fluid characteristics and other factors, such as display fluctuations, reduced accuracy and even instrument damage.

2. Analysis of faults generated during product commissioning
Commissioning failures usually occur during the instrument installation and commissioning stage. Once eliminated, they will not reappear under the same conditions in the future. Common commissioning failures are usually caused by improper installation, environmental interference, and fluid characteristics.
1) Installation It
is usually caused by incorrect installation of the electromagnetic flow sensor. Common examples include installing the sensor at the highest point of the pipe system where gas is easily accumulated; 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, forming a non-full pipe in the measuring pipe.
2) Environmental aspects
It is usually mainly pipeline stray current interference, strong electromagnetic wave interference in space, and magnetic field interference of large motors. Pipeline stray current interference usually takes good separate grounding protection to obtain satisfactory results, but if encountering strong stray currents (such as electrolysis workshop pipelines, sometimes the AC potential peak Vpp induced on the two electrodes can be as high as 1V), additional measures and flow sensor and pipeline insulation are required. Spatial electromagnetic wave interference is generally introduced through the signal cable, and is usually protected by single or multi-layer shielding.
3) Fluid aspect
The measured liquid contains uniformly distributed tiny bubbles which usually do not affect the normal operation of the electromagnetic flowmeter
, but as the bubbles grow, the output signal of the instrument will fluctuate. If the bubbles are large enough to cover the entire electrode surface, the electrode circuit will be instantly disconnected as the bubbles flow through the electrode, causing greater fluctuations in the output signal. When
the electromagnetic flowmeter with low-frequency square wave excitation measures slurry with excessive solid content, slurry noise will also be generated, causing fluctuations in the output signal.
When measuring mixed media, if the flow sensor is used for measurement before the mixture is evenly mixed, the output signal will also fluctuate.
Improper matching of electrode materials and measured media will also affect normal measurement due to chemical reactions or polarization phenomena. The electrode materials should be correctly selected according to the instrument selection or relevant manuals.

III. Analysis of instrument failures during operation
Operational failures are failures that occur after the electromagnetic flowmeter has been debugged and operated normally for a period of time. Common operational failures 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, adhesion layers often accumulate on the inner wall of the sensor and cause failures. These failures are often caused by the conductivity of the adhesion layer being too large or too small. If the adhesion is an insulating layer, the electrode circuit will be open and the meter will not work properly; if the conductivity of the adhesion layer is significantly higher than the conductivity of the fluid, the electrode circuit will be short-circuited and
the meter will not work properly. Therefore, the adhesion scaling layer in the measuring tube of the electromagnetic flowmeter should be removed in time.
2) Lightning strike
Lightning strikes can easily induce high voltage and surge current in the instrument circuit, causing damage to the instrument. It is mainly introduced through power lines, excitation coils, or flow signal lines between sensors and converters, especially from the power lines in the control room, which account for the vast majority.
3) Changes in environmental conditions
During the commissioning period, the flowmeter works normally because the environmental conditions are still good (for example, there is no interference source). At this time, it is often easy to neglect the installation conditions (for example, the grounding is not very good). In this case, once the environmental conditions change and new interference sources appear during operation (such as welding on the pipeline near the flowmeter, installing a large transformer nearby, etc.), it will interfere with the normal operation of the instrument and the output signal of the flowmeter will fluctuate.

3. Summary
Electromagnetic flowmeters may have various faults during use, but generally speaking, all faults can be attributed to two categories, namely, debugging period faults and operation period faults. As long as we always pay attention to these two types of faults in daily work and eliminate and solve them well, I believe that electromagnetic flowmeters will be able to play their due role.