Handling Common Radar Level Gauge Faults

Radar liquid level gauge is one of various liquid level measuring instruments with wide application range, convenient measurement and maintenance. With the new price reduction and improved cost performance, the application will become more and more extensive and play an increasingly important role in liquid level measurement. To optimize the measurement, we should start from the source of the selection, installation, etc., and then take better measures to eliminate interference during use, so as to minimize the probability of instrument failure, truly reflect its reliability and high precision characteristics, and provide control over the production process. Provide accurate evidence.

Based on common experience, today I\'m going to summarize some common failure causes, hoping to help you:

1. There is an error in the valuer of measurement

The failure shows that the change trend of the actual liquid level and the measured value are consistent, but the values ​​are not equal. This is a common fault, relatively simple and easy to eliminate. Use the traditional rope measurement method to measure the actual distance above the sky. If the measured value is consistent with the distance above the meter, it proves that the quality of the meter itself is not a problem. According to the principle of operation of the radar level gauge, the actual liquid level is obtained by subtracting the distance D from the measurement reference point to the surface of the fluid from the distance E from the empty tank. Therefore, the height of the empty tank must be accurate to ensure accurate and reliable measurement. Therefore, before calibration, field measurements should be performed to obtain real data. If the meter is connected to the computer system, it cYou should also check if the meter\'s full scale settings are consistent with the computer\'s configuration data.

2. The measured value is obviously distorted

The fault indicates that the liquid level changes and the measured value remains constant. When the storage tank is empty or nearly full, the meter maintains an obvious false material level, or it may show a low value when the material in the reservoir is nearly full. This type of failure is usually caused by the following reasons:

(1) The antenna is damaged. Thick, moist crusts will reflect microwaves strongly, keeping the gauge reading at a constant high level.

(2) When the equipment is emptied, the antenna or nearby condensate produce spurious echoes.

(3) When emptying the equipment, the fixed elements in the tank cause strong echoes. The following methods should be adoptedes to solve the above situation:

(1) Thoroughly clean the antenna and the accessories near the antenna.

(2) Turn on and set the \"window resistance\" distance reasonably. \"Window suppression\" is also referred to as \"near site suppression\". This function is used to eliminate the influence of mounting welds, antennas or materials hanging around it on the measurement. This is an effective way to optimize the measurement. It sets the near site suppression distance and the instrument records the echo in this range as an interference echo and does not measure it.

(3) Perform \"fixed component echo cancellation\". In addition to intelligently filtering the interference echo by software, the radar level gauge can also resist the fixed component echo by recording the interference wave.

(4) When the material in the tank is about to be plein, the instrument displays a lower material level. This is due to the increase in multiple echoes in the tank due to the rise in liquid level. waves are incorrectly identified as measurement echoes, fromAnd calculate the greatest air distance. In this situation, the near-field suppression distance must be changed to eliminate the influence of multiple echoes.

3. Fluctuation of the measured value

In the tank, due to the violent fluctuation of the surface of the stirring medium, or the temporary interference echo in the tank is increased due to the power supply, the measured value fluctuates. Besides improving application settings (enabling floating point average curve algorithm), enabling near site suppression, and increasing output damping, you should also check the position of installation of the meter or consider installing an antenna of mores large size. .

In the author\'s experience, if it is a board-powered two-wire instrument, you should also check whether the DCS analog input board has a capacity of sufficient charge. The radar level gauge in Settlement Tank 160 had a fault indicating that the measured liquid level was stable but the measured value fluctuated violently. After a full inspection, the DCS AI Cassette was determined to have insufficient load capacity. Change the instrument power supply from the board channel to external power supply mode, and the measurement signal is sent to the board through the isolator, and the instrument fault disappears.

4. Lost wave

The failure is manifested by a \"lost wave\" error or an instrument crash. When measuring liquids with low dielectric constant, wave loss often occurs due to the low reflectance of the liquid, but there is no\'there is no problem of low liquid reflectability in the alumina industry, so the wave loss is mainly due to vortex and turbulence The liquid surface and thick thick foam make the radar wave scatters or is absorbed, so the echo is weak or even no echo. To deal with this situation, the application parameters must be set according to the characteristics of the process in the container. If the above measures have no obvious effect, the installation location should be changed or the larger size antenna should be used to improve the echo strength. Using waveguide or branch pipe is an effective way to solve the frequent phenomenon of wave loss, but the installation workload is large and not suitable for slurry that is easy to scar .

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