Radar level meter adopts non-contact measurement, and has the advantages of high measurement accuracy, not affected by process conditions, easy to install and easy to 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 offshore oil platform to understand the reasons and solutions of the radar level meter's measurement value jumping.

The first case was an oil field where the radar meter in the left crude tank jumped to full scale several times during production. A sealed metal cover was used to cover the main body of the sensor, 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 decreases. After analysis, it is determined that the closed metal cover is the main cause of false signals, the radar level meter antenna is made of plastic, and the radar waves emitted by the antenna leak into the external environment. The closed metal shield is used to cover the instrument, and the leaked radar wave signal is received by the antenna after several reflections inside the shield, generating a false level. Therefore, the metal shield was modified to a ring-shaped non-sealed shield at a later stage, and the radar flow 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 it is stored within a certain temperature range. As the crude oil in the lower tank contains a small amount of water, some of the bottom water will precipitate out of the bilge water after standing, 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, false signals are suppressed within 0~0.25m and the suppression line is set to 120dB to avoid false signals caused by water vapor condensation and level jumps at the top. In response to this situation, after on-site analysis and research tests decided to do a good job of pre-dewatering treatment, the water content of the crude oil in the lower tank is controlled at less than 0.5%, the heating temperature of the crude oil tank is controlled so that the crude oil in the tank is lower than 65 ℃, and the instrumentation is covered with thermal insulation materials on the outside, etc. Through the above measures, the phenomenon of level jumping caused by the formation of condensation at the antenna of the radar liquid level meter is eliminated.

The third case is that, during the commissioning stage of a platform construction, when the liquid level is higher than 3800mm, the radar type flow meter of the dirty oil tank will frequently jump to 0mm, which leads to the shutdown of the fourth-stage production unit. After on-site inspection, the power supply voltage of the radar level meter transmitter is only 9.5V, which is lower than the working power supply voltage of the radar level meter. By further searching for the cause of the failure, found that when the high liquid level, the voltage at the power supply is 23.7V, the safety gate output drops to 9.7V, judged as a safety gate transmitter failure. After replacing the safety grid, the voltage returns to normal, the cabin radar level meter in the test to rule out the problem.

In this paper, there are three situations that lead to the radar level meter measurement value jump, respectively, closed metal cover, condensation on the antenna, power supply power supply is insufficient. In fact, the radar level meter measurement value jump belongs to a relatively common problem, leading to the emergence of this problem for a number of reasons, the emergence of problems in a timely manner to find the cause and solve the problem is the most important.