Electromagnetic flowmeter common fault analysis - Database & Sql Blog Articles

Common Fault Analysis of XD-LDG Series Electromagnetic Flowmeter of Jiangsu Xianda Instrument Co., Ltd.

1, debugging period failure

Debugging expectation failures generally appear in the instrument installation and debugging phase. Once excluded, they will not appear again under the same conditions in the future. Common commissioning failures are often caused by improper installation, environmental disturbances, and fluid characteristics.

1) Installation aspects

Usually the fault caused by the incorrect installation position of the electromagnetic flow sensor, such as installing the sensor at the highest point of the pipe that is easy to accumulate gas; or installing it on the vertical pipe from top to bottom, may appear empty; or after the sensor Back pressure, the fluid is directly discharged into the atmosphere to form a non-full tube inside the measuring tube.

2) Environmental aspects

Usually mainly due to pipeline stray current interference, space strong electromagnetic wave interference, large motor magnetic field interference. Pipe stray current interference usually takes good single grounding protection to get satisfactory results, but if you encounter strong stray current (such as electrolysis shop piping, sometimes the peak potential Vpp induced on the two electrodes can be as high as 1V), still Additional measures and insulation of the flow sensor and piping are required. Space electromagnetic interference is typically introduced via a signal cable and is typically protected by a single or multiple layers of shielding.

3) Fluid aspects

The evenly distributed tiny bubbles in the liquid to be tested usually do not affect

High pressure electromagnetic flowmeter

Normal work, but as the bubble increases, the instrument

The output signal of the meter will fluctuate. If the bubble is large enough to cover the entire surface of the electrode, the output signal will be more fluctuated as the bubble flows through the electrode and the electrode circuit will be momentarily broken.

Low frequency square wave excitation

High pressure electromagnetic flowmeter

When the solid content is too much, the slurry noise will also be generated, causing the output signal to fluctuate.

When measuring mixed media, if the flow sensor is measured before the mixing is not uniform, the output signal will also fluctuate.

Improper matching of the electrode material and the measured medium will also affect normal measurement due to chemical action or polarization. The electrode material should be properly selected according to the instrument selection or related manual.

2. Runtime failure

Runtime failure is

High pressure electromagnetic flowmeter

Common faults during commissioning and normal operation for a period of time 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) Sensor inner wall adhesion layer

due to

High pressure electromagnetic flowmeter

Often used to measure dirty fluids, after running for a period of time, often accumulate on the inner wall of the sensor to cause failure. These failures are often caused by the electrical conductivity of the adhesion layer being too large or too small. If the attachment is an insulating layer, the electrode circuit will be broken and the meter will not work normally; if the conductivity of the adhesion layer is significantly higher than the fluid conductivity, the electrode circuit will be short-circuited.

The meter also does not work properly. Therefore, it should be cleared in time

High pressure electromagnetic flowmeter

The scale layer attached to the tube is measured.

2) Lightning strike

Lightning strikes easily induce high voltages and surge currents in the meter circuit, causing damage to the meter. It is mainly introduced through the power line or the excitation coil or the flow signal line between the sensor and the converter, especially from the control room power line.

3) Changes in environmental conditions

During commissioning, because the environmental conditions are still good (for example, there is no source of interference), the flowmeter works normally, and 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, a new source of interference occurs during operation (such as welding on the pipeline near the flowmeter, installing a large transformer nearby, etc.), which will interfere with the normal operation of the meter, and the output of the flowmeter. The signal will fluctuate.