Radar level meter adopts non-contact measurement, and has the advantages of high measurement accuracy, are not being affected by process conditions, easy to install and maintain, so it is widely used in offshore oil platforms in recent years. Today, we would like to take you through several actual cases in the offshore oil platform to understand the reasons and solutions for the jump in the measured value of the radar level meter.
The first case is an oil field where the radar level meter in the left crude oil tank jumped to the full range several times during production. A sealed metal cover was used to cover the sensor body and during the test, it was found by connecting the radar level transmitter that the closed metal cover would result in more false signals throughout the measurement range and the overall noise line would rise. When the cover above the closed metal cover is opened, the false signal disappears, the overall noise line decreases and the echo curve is reduced.
After analysis, it was determined that the closed metal cover was the main cause of the false signal. The radar level meter antenna is made of plastic and the radar waves emitted by the antenna leak into the external environment.
The enclosed metal shield was used to cover the instrument, and the leaked radar wave signal was reflected inside the shield several times and then received by the antenna, producing a false level.
Therefore, the metal shield was later modified into a ring-shaped non-sealed shield, and the radar level meter jump was significantly reduced.
The second case is that in order to ensure the fluidity of crude oil, offshore oil platforms usually use hot medium oil heating pipes to heat the crude oil to ensure that the crude oil is stored within a certain temperature range.
As the lower bilge crude oil contains a small amount of water, some of the bottom water will settle out of the bilge after resting, and the water vapor will evaporate during the continuous heating process.
The water vapor condenses on the antenna at the top of the tank to form water droplets, causing a strong false signal at the top. Therefore, the false signal is suppressed in the range of 0~0.25m, and the suppression line is set to 120dB to avoid the false signal caused by water vapor condensation and liquid level jump at the top.
In response to this situation, it was decided after on-site analysis and research tests to do a good job of pre-dehydration treatment, to control the water content of crude oil in the lower tank below 0.5%, to control the heating temperature of the crude oil tank so that the crude oil in the tank is lower than 65°C, and to cover the outside of the meter with thermal insulation materials, etc.
Through the above measures, the level meter jump phenomenon caused by condensation forming at the antenna of the radar level meter was eliminated.
The third case is that during the commissioning stage of platform construction, when the liquid level was higher than 3800mm, the radar level meter of the foul oil tank would frequently jump to 0mm, resulting in the shutdown of the four-stage production unit. After on-site inspection, the power supply voltage of the radar level meter transmitter was only 9.5V, which was lower than the working power supply voltage of the radar level meter. By further finding the cause of the fault, it was found that the voltage at the power supply was 23.7V when the liquid level was high and dropped to 9.7V after the safety grid output, which was judged to be a failure of the safety grid transmitter. After replacing the safety grid, the voltage returned to normal and the cabin radar level meter was eliminated in the test.
In this article, there are three situations that cause the radar level meter measurement value to jump, respectively, a closed metal cover, condensation on the antenna, and a power supply are insufficient.
In fact, the radar level meter measurement value jumping belongs to a relatively common problem, resulting in this problem there are many reasons, the problem in time to find the cause and solve is the most important.