The correct use of radar level gauges

The radar level gauge uses electromagnetic waves (microwaves) for continuous non-contact level measurement and is specifically used for liquid level measurement of liquids, pastes and slurries in storage vessels. But how to correctly use radar level gauges in sewage treatment?

Sewage homogenization tanks are used to homogenize water quality at different time intervals, and the adjustment of water volume is an important equipment that affects the effect of sewage treatment. Maintaining a certain amount of water in the tank is a prerequisite for good sewage treatment. Therefore, the accurate measurement of the level of the homogenizer tank is particularly important for the normal operation of the hydrophobic treatment.

The level of the homogeneous tank was originally measured by the air-blowing method, but the pressure-injection tube often blocked and coagulated, which caused many difficulties for the operation and maintenance of the instrument. To this end, in June 1997 a new BM70 radar level gauge manufactured by Jiuji Instrument Co., Ltd. was newly installed. The level gauge of a homogeneous tank was monitored, as shown in Fig. l.

Radar level gauge Introduction The radar level gauge is a new type of instrument that has been gradually applied in China in recent years. It uses electromagnetic waves (microwaves) for continuous non-contact liquid level measurement, specifically for liquid level measurement of liquids, pastes and slurries in storage vessels. It is not affected by the upper gas density and thermal stratification of the contents of the container tank, and even if the air in the container tank contains smoke, dust or noise during the injection process, accurate measurement can be guaranteed. The radar level gauge consists of a probe and a signal converter, which can be on-site indication or remote transmission indication (output 4-2/hnA standard signal) or connected with a microcomputer.

Working principle The BM70 radar level gauge works on the basis of the FMCW (Frequency Modulation Continuous Wave) radar method. A microwave FM signal with a fixed amplitude is emitted through the antenna and reflected on the object. The reflected microwave signal is received after a certain period of time and is mixed with a part of the transmitted signal. The frequency of the output signal of the mixer is proportional to the interval time, so it can accurately reflect the distance from the surface of the measured medium (level), as shown in FIG. 2 .

Installation, adjustment and improvement measures The installation of the radar level meter Bl'd70 is required to be on the same level, and the microwave hole area should extend out of the connecting device. It can not be installed near the population connection pipe of the tank, and should be installed far away from the source of interference. Figure 3 and Figure 4 are incorrect installation methods. The correct installation is shown in Figure 5.

There are two things to note when installing:

1) In order to eliminate the effect of the ineffective vibration, a method of reinforcing the short tube is used to reduce the vibration of the instrument.

2) The instrumentation piping was not fixed during the original installation, and the liquid level of the meter fluctuates greatly. After adopting the method of fixing the bracket and then welding, the error of the amount of é’¡j caused by the shaking of the instrument is avoided.

During the actual operation, it was found that the liquid level indicated by the instrument was sometimes not zero when the homogenized tank was not fed into the sewage. We verified the instrument by preprogramming the microcomputer. We found that the internal signal of the instrument was strong. We eliminated the interference signal, recalibrated the zero calibration, and the instrument entered the normal liquid level display state, as shown in Figure 6 and Figure 7, respectively.

After more than one year of operation, the results prove that the liquid level gauge has good performance, smooth operation, small maintenance workload, and intuitive indication (a level can be displayed directly at a level and can also be remotely transmitted to the operating room). It can work normally in environments with oil and oil and gas, and it also throws abnormalities at 8o°C. The author believes that for the petrochemical wastewater treatment, the instrument is used for liquid level measurement, with advanced technology, reliable performance, and strong practicality.