Failure analysis of electromagnetic flowmeter Posted by : admin / Posted on : Jun 11， 2021

Failure analysis of electromagnetic flowmeter

1. Failure during commissioning
Faults during the commissioning period generally occur during the installation and commissioning phase of the instrument. Common faults during the commissioning period are usually caused by improper installation, environmental interference, and fluid characteristics.
2. Installation
The fault is usually caused by the incorrect installation position of the electromagnetic flow sensor, such as installing the sensor at the highest point of the piping system that is easy to accumulate gas; or installing it on a vertical pipe from top to bottom, and emptying may occur; or there is nothing behind the sensor. With back pressure, the fluid is directly discharged into the atmosphere to form a non-full tube in the measuring tube.
3. Environmental aspects
Usually, it is mainly caused by pipeline stray current interference, strong electromagnetic wave interference in space, and magnetic field interference of large electric motors. Pipeline stray current interference usually takes good separate grounding protection to obtain satisfactory results, but if it encounters strong stray currents (such as electrolytic workshop pipes, sometimes the peak value of the AC potential Vpp induced on the two electrodes can be as high as 1V). Additional measures and insulation between the flow sensor and the pipeline must be taken. Space electromagnetic wave interference is generally introduced through signal cables, and is usually protected by single-layer or multi-layer shielding.
4. Fluid aspect
The evenly distributed microbubbles in the measured liquid usually do not affect the normal operation of the electromagnetic flowmeter, but as the bubbles increase, the meter
The output signal of the meter will fluctuate. If the bubble is large enough to cover the entire electrode surface, as the bubble flows through the electrode, the electrode circuit will be instantaneously disconnected and the output signal will fluctuate more.
When the electromagnetic flowmeter with low frequency square wave excitation measures the slurry with too much solid content, it will also produce slurry noise, which will cause the output signal to fluctuate.
When measuring mixed media, if the flow sensor is used for measurement before the mixing is not uniform, the output signal will also fluctuate.
Improper selection of electrode material and measured medium will also affect normal measurement due to chemical effects or polarization phenomena. The electrode material should be correctly selected according to the instrument selection or relevant manuals.