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Analysis of the failure of electromagnetic flowmeter

The electromagnetic flowmeter can be divided into faults during the commissioning period and the running period according to the different fault time. The following is the frequently occurring fault phenomenon of the electromagnetic flowmeter.
First, the commissioning period failure
Generally, during the initial installation and commissioning of the instrument, once the instrument is improved, the electromagnetic flowmeter failure can be eliminated. Common faults caused during the commissioning period of the electromagnetic flowmeter are improper installation, interference from the external environment, and fluid characteristics. 1. Fluid piping systems and instrument installation.
Such faults are generally caused by improper installation of the sensor. For example, the sensor is installed at a high point of the industrial pipe network where gas is easily accumulated, and the liquid is directly discharged into the atmosphere through the flow sensor, forming a non-full pipe phenomenon in the measuring tube, and the sensor is installed in the fluid self. On the vertical pipe that flows up and down, it is easy to form an emptying phenomenon.
2. Environmental aspects
Most of the faults caused by the external environment are caused by the interference of external electromagnetic waves, motor magnetic fields, stray currents and the like. External electromagnetic wave interference is mainly introduced by signal cables, and is usually protected by single or multiple layers of shielding. Current interference is usually achieved by a relatively good separate grounding protection.
3. Fluid aspects
The tiny bubbles in the fluid generally do not affect the normal electromagnetic flowmeter measurement, but the measured fluid volume flow is the sum of the fluid and the gas. The increase of tiny bubbles in the fluid will change the output signal of the flowmeter. If the tiny bubbles in the fluid increase to cover the entire surface of the electrode, the electrode signal loop will be momentarily disconnected, so that the measured output signal will be relatively large. Variety.
Second, the operating period failure
The cause of the malfunction of the electromagnetic flowmeter during operation is generally the fouling of the inner wall of the electromagnetic flow sensor, the lightning strike of the instrument, and the measurement of environmental conditions by the flowmeter.
Inner wall adhesion layer
Since the fluid measured by the electromagnetic flowmeter mostly contains suspended solid phase or dirty body, the fault frequency of the adhesive layer on the inner wall of the electromagnetic flow sensor is high. If the conductivity of the adhesive layer and the liquid are close, the instrument can still perform normal signal output. Just changing the flow area of the fluid will lead to a hidden fault of the measurement error; if the adhesion layer is high conductivity, the potential between the electrodes of the electromagnetic flow sensor is easy to be short-circuited; if the adhesion layer is insulating, the surface of the electrode of the electromagnetic flow sensor is insulated and broken. The measurement loop is opened. The latter two phenomena require cleaning the adhesive layer or replacing the sensor to make the meter work properly.
2. Lightning strike
When the line encounters a lightning strike, it will instantaneously generate high voltage and surge current, and the instrument is easily damaged after being struck by lightning. Lightning strikes enter the instrument mainly through three channels: the instrument power line, the excitation line and the flow signal line between the converter and the sensor. From the analysis of instrument parts damaged in lightning faults, most of the lightning strikes enter the instrument through the control room power line, causing failure, while the other two ways are less.
Knowing when it is easy to cause failure, it can cause relevant attention during daily installation and use, which can effectively avoid the abnormal use of the flow meter and bring convenience to daily production.

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