The radar level gauge is a new type of liquid level measuring instrument, and its application in the petrochemical industry is particularly extensive. In the production process, people often do not have sufficient familiarity with the new instrumentation and troubleshooting methods, and can intensify the failure of the radar level gauge when it is not timely useful to solve the fault of the radar level gauge. This article is based on the radar liquid level. Measured faults common topics suggest some solutions. 
The radar level gauge is a new type of liquid level measuring instrument, and its application in the petrochemical industry is particularly extensive. In the production process, people often do not have sufficient familiarity with the new instrumentation and troubleshooting methods, and can intensify the failure of the radar level gauge when it is not timely useful to solve the fault of the radar level gauge. This article is based on the radar liquid level. The common problems of the metering faults have provided some solutions. Using a combination of theoretical analysis and field tests, the reasons for the faults of the level gauges are briefly explained. Through the analysis and demonstration of the causes of the faults, some radar levels are finally summarized. Calculate the method of troubleshooting. The following is the common cause of the failure of the radar level gauge and the possible reasons for its existence:
1. There is an error in the measured value
The faults show that the actual liquid level and the measured value are in the same trend, but the values ​​are not equal. This is a common failure that is simpler and easier to eliminate. The traditional distance measuring method is used to measure the actual distance over the sky. If the measured value is consistent with the distance displayed by the instrument, the quality of the instrument itself is no problem. According to the working principle of radar level gauge, the actual liquid level is obtained by subtracting the distance D from the reference point to the surface of the medium from the empty distance E, so the empty height must be accurate to ensure accurate and reliable measurement. Therefore, before calibration It must be measured on the ground to obtain the most realistic data. If the instrument is connected to a computer system, check whether the full-scale parameters of the instrument are consistent with the computer configuration data.
2. The measured value is obviously distorted
The fault is manifested as the change of the liquid level and the measured value is always constant. When the tank is empty or nearly full, the meter maintains a clear false material level, or it shows that the tank will bounce back to a low value when the material in the tank is full. This type of failure is usually caused by the following reasons:
(1) Antenna formation. Thick and wet scabs will have a strong reflection of the microwaves, keeping the instrument measurement at a constant high level.
(2) When the material is empty, the antenna or nearby agglomerates produce interference echoes.
(3) When the material is empty, the fixed components in the tank cause a strong echo. The following methods should be taken to solve the above situation:
(1) Carefully clean the antenna and the attachment near the antenna.
(2) Activate and reasonably set the "window boycott" distance. "Window suppression" is also called "near-field suppression". This function is used to eliminate the impact of mounting flange welds, antenna or its vicinity hanging on the measurement, and is an effective measure to optimize measurement. It sets the near-site inhibition distance and the instrument registers echoes in this range as interference echoes without measuring.
(3) Perform "fixed component echo suppression". In addition to intelligent filtering of interference echoes, radar level gauges can also register fixed wave echoes by registering interference waves.
(4) The meter displays a lower material level when the material in the tank is full, due to the increase of multiple echoes in the liquid level rise tank. When the program is processing, a long echo of a time course is erroneously recognized as the measurement back. Waves to calculate a larger distance over the sky. For this situation, the near-field suppression distance should be modified to eliminate the effects of multiple echoes.
3. Measurement fluctuations
In the tank, the surface of the stirring medium fluctuates violently, or because the lower material causes temporary interference echoes in the tank to increase, so that the measurement value fluctuates. In addition to improving application parameters (floating point average curve algorithm), activating near-site suppression, and increasing output damping, you should also check the installation location of the instrument or consider installing a larger antenna.
According to the author's experience, if the card is powered by a two-wire meter, it should also check whether the DCS analog input card has enough load capacity. The 160-slot radar level gauge for settling has experienced failures in which the measured liquid level is stable but the measured value fluctuates dramatically. After a thorough inspection, it is determined that the AI-cassette load capacity of the DCS system is insufficient. The instrument is changed from the card channel power supply to the external power supply method. The measurement signal is sent to the card through the isolator and the instrument fault disappears.
Loss of wave
The failure manifested as a "lost wave" error or a crash in the instrument. When measuring low-dielectric constant liquids, the phenomenon of loss of waves often occurs because the reflection ability of the liquid is weak, but in the alumina industry, there is no problem of weak liquid reflection ability, so the loss of wave is mostly due to vortices and turbulence. The liquid surface, thick and thick foam makes the radar wave diffuse or be absorbed, so the echo is weak and there is no echo. To treat this situation, the optimal application parameters should be set according to the process characteristics in the vessel. If the above measures have no obvious effect, the installation position or larger antenna should be changed to enhance the echo strength. The use of waveguides or bypass tubes is an effective method to solve the problem of frequent wave losses, but the installation workload is large and it is not suitable for easy slurrying.
The radar level gauge is the most widely used, most accurate, and most convenient for maintenance in all types of liquid level measuring instruments. With the further reduction of the price and the improvement of the cost performance, the application will become more and more extensive and play an increasingly important role in the level measurement. To optimize the measurement, we must start from the root of the selection and installation, and then eliminate the interference measures in use to minimize the probability of occurrence of instrument failure, truly reflect its reliable, high-precision features, and provide for the production process control. Accurate basis.
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