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According to the classification problem, it can be divided into:
(1) Operation failure;
(2) Debugging stage failure. The main reason for the failure of the debugging stage is the new and early stage of debugging. The main reason is that the selection or setup of the tool is unreasonable, the installation error is incorrect, and the main reason is that the fluid inclusions are attached to the electrode Li Ning, and the environmental changes are caused during operation. New sources of interference, etc.
According to the external source of the fault, it is analyzed from three aspects:
(1) Reasons for piping system installation; (2) Environment; (3) Fluid induced.
Failure, initial cycle of the operation cycle and normal operation for a period of time, failed during operation. Common causes of failures are: internal flow sensor connection layer, lightning strikes, and environmental changes.
1, the internal connection layer due to the electromagnetic flow meter to measure the chance of containing the suspended solids or dirty dirty body than any other flow meter, the inner connection appears to produce a relatively high probability of failure. If the adhesion layer of conductivity and liquid conductivity is tight, the instrument can also output normal signal, only changing the flow field, forming a hidden failure of the measurement error; if the high-conductivity adhesion layer, the electromotive force between the electrodes will short circuit; if the insulating layer Connection, electrode surface insulation and disconnection circuit. Both phenomena can make the instrument unable to work.
2. Lightning Strikes Lightning Strikes High-voltage transients that induce transient currents into the instrument may damage the instrument. Lightning damage damages the instrument in three ways: power lines, excitation signals and streamlines between sensor spoon transducers. However, from the lightning damage analysis of various parts of the failure, leading to the failure of high voltage and surge currents from the control room of the power circuit, other methods. Lightning strikes the electromagnetic flowmeter from the scene of the accident, not only fails, the control room, often in the other instrumental electricity lightning strike accident at the same time. Therefore, the use of the unit knows the importance of power line control room instruments, lightning protection facilities. If there is currently a general and exploratory design unit team solve this problem.
3. The main reason for the change of environmental conditions is the fault environment day of the commissioning phase, not only during the commissioning but also during the operation of the interference source. For example, ground fault protection is not ideal, electromagnetic flowmeters, there is no air source plant during commissioning, and the equipment is working properly, but during operation, new sources of interference (such as point pipe or near-to-far pipe welding) interfere with the normal operation of the instrument Large fluctuations in the output signal.
Secondly, the debugging of electromagnetic flowmeters with faults such as faults and initial debugging, but once the faults are improved, they will not appear again under the same conditions. Common faults are mainly due to the installation and commissioning period, environmental disturbances, and the influence of fluid characteristics. There are three reasons.
1. Incorrect installation of common electromagnetic flow sensors, such as piping system installation, is common. For example, the flow sensor is installed on the network of natural gas pipelines, which is easy to accumulate and retain high; the flow sensor does not have any pressure, and the liquid flows directly into the atmosphere to form a complete The measuring tube; installed in the empty due to the vertical line may appear empty, the installation of the flow meter is special because of potential underwater, to ensure that there is no floating.
2. Stray current interference in the main pipeline of the environment, electromagnetic interference in the space, disturbance of the magnetic field of the large electrical machine, etc. The interference of the stray current of the pipeline is usually taken with good grounding protection. A satisfactory individual measurement can be obtained, but there is strong stray current in the case tube ( Such as the electrolysis workshop assembly line can not be overcome, should take the unique measures of the flow sensor and piping edge. Introduction of electromagnetic wave-space signal cable, usually single or multiple shielded protection, but also encountered shielding protection can not be overcome.
3, fluids containing micro-bubbles are usually evenly distributed, do not affect the normal measurement, only the volume flow of liquid and gas combined; bubbles will increase the output signal fluctuations, if the large bubbles cover the entire flow through the electrode surface of the electrode, so that the electrode signal instantaneous Disconnect the circuit, the output signal will produce greater fluctuations.
Frequently encountered in the use of electromagnetic flowmeter failure, the first is the common instrument failure, that is, instrument structure or components cause damage failure; followed by the external causes. Such as installation and flow distortion, deposition and scaling. The focus is on the causes of failure of the second category and applications.