1 Introduction

Common troubles in the use of electromagnetic flowmeter, there is the instrument itself component damage caused by failure, there is the use of improper, improper installation, environmental conditions, fluid characteristics and other factors, such as the display of fluctuations, the accuracy of the instrument damage, etc.. It can be generally divided into two types: the installation and debugging of the failure (commissioning) and normal operation of the failure (running time fault).

2 debug phase fault

Debugging and look forward to the general appearance of the instrument installation and commissioning stage, once ruled out, the same conditions will not occur in the future. Common debugging phase fault is usually caused by improper installation, environmental interference, and fluid characteristics.

1) installation

Usually electromagnetic flow sensor installation position is not correct cause failure, common as the sensor is installed in the highest point of the gas pipe, or installed on the top of the vertical tube, may appear emptying; or the sensor without back pressure, the fluid is directly discharged into the atmosphere and the formation of non full tube.

2) environment

Usually the main duct is stray current interference, strong electromagnetic interference, large motor magnetic field interference, etc.. The stray current interference of the duct is usually adopted to protect the good individual. However, if there is a strong stray current (such as an electrolytic plant pipe, the peak Vpp of two electrodes can be as high as 1V), the other measures are required to be taken as well as the insulation of the pipe. Space electromagnetic wave interference is usually introduced by the signal cable, and it is usually protected by single or multi-layer shielding.

3) fluid

The measured liquid contains a uniform distribution of tiny bubbles usually do not affect the normal work of the electromagnetic flowmeter, but the bubble increases, the instrument output signal will fluctuate, if the bubble is large enough to cover the entire surface of the electrode, the electrode will flow through the electrode circuit and make the output signal more volatile.

When the low frequency square wave excitation electromagnetic flow meter measures the solid content of the slurry, it also generates the slurry noise, so that the output signal has a fluctuation.

When measuring the mixed medium, the mixture is not even before entering the flow sensor to measure, it will also make the output signal fluctuations.

The electrode material and the measured medium are not properly selected, and the chemical effect or polarization phenomenon is also affected. Selection of electrode materials for the selection of instruments or the relevant manual.

3 running phase fault

The operating period of the fault is the fault of the electromagnetic flow meter and the normal operation of a period of time after the common operation of the fault generally by the flow sensor wall attached layer, lightning strikes and environmental conditions and other factors.

1) sensor inner wall attachment layer

Electromagnetic flowmeter is used to measure the dirty liquid, after running for a period of time, often accumulate on the inner wall of the sensor attached layer and malfunctions. These failures are often caused by the electrical conductivity of the attached layer, too large or too small. If the attached material is an insulating layer, the electrode circuit will be open, the instrument can not work normally. If the adhesion layer conductivity is significantly higher than the fluid conductivity, the electrode circuit will appear short circuit,

Instrument to work properly. Should be cleared in time to measure the electromagnetic flow meter tube inside the tube.

2) lightning strike

The high voltage and surge current are induced in the circuit of lightning stroke, which can cause the instrument to damage. It is introduced into the main power line or the excitation coil or the flow signal line between the sensor and the converter, especially from the control room.

3) environmental conditions

During the commissioning of the environment is still good (for example, there is no interference source), the flow meter work is normal, at this time is often easy to neglect the installation conditions (for example, the connection is not good). In this case, once the environmental conditions change, the emergence of new sources of interference (such as the flow of electric welding near the flow meter, near the installation of large transformers and so on), will interfere with the normal work, the flow meter output signal will fluctuate.

4 knots

The use of electromagnetic flowmeter, there may be a variety of failures, but generally speaking, all the fault can be attributed to two categories, that is, debugging and operation of the fault, the daily work of the two types of failures, and very good to be excluded from the settlement, I believe that electric magnetic flowmeter will be able to play its due role.