In recent years, the radar level meter has been widely promoted and applied in the chemical industry because of its advantages such as small dead zone of liquid level measurement, high continuous measurement accuracy, small influence of medium characteristics, large measurement range, high temperature and high pressure resistance and non-contact measurement method. Radar level gauge measurement principle
The measurement principle of radar liquid level meter is to measure the clearance distance of the surrounding space through the linear propagation characteristics of electromagnetic waves, that is, the linear space distance between the measured object and the radar, which is specific to the industrial production that is the liquid level of the liquid to the air height of the radar antenna. The vertical distance from the radar antenna to the bottom of the container can be set through the configuration of the radar level meter, and the liquid level height can be calculated according to the measured liquid level height. Construction of radar level gauge
The radar level meter produced by different manufacturers has different forms, but the overall components are generally the same, which mainly includes the circuit part (radar wave generator, signal detection, signal processing), antenna and receiver and installation accessories table body three parts. According to the different antenna, radar level meter can be divided into guided wave radar and ordinary radar two types.
Guided wave radar level gauge
Guided wave radar is a metal wave guide installed below the electromagnetic wave transmitter, so that high-frequency radio waves propagate vertically down the metal body. When the electromagnetic wave hits the liquid surface of the measured substance, the electromagnetic wave will reflect on the contact surface and return vertically along the waveguide body to the receiver inside the radar level meter antenna, and then process the circuit for analysis and calculation. Obtain the liquid level height of the measured liquid. According to the different metal waveguide, waveguide radar can be divided into two categories: cable type and rod type.
The waveguide body of the cable type waveguide radar is a flexible stainless steel metal rope with a metal weight tied at the end to ensure that the metal rope extends vertically into the bottom of the container in the measured liquid to prevent the metal rope from floating and swinging during use. The radar level meter of this structure is mainly used in the measurement of the liquid level below the ground, such as the bottom tank and the zero tank. The waveguide radar used in the general field is shown in the figure: the waveguide body of the rod waveguide radar is divided into many kinds according to the difference of the waveguide rod and the antenna, there are metal rod waveguide radar, there are horn antenna waveguide radar through the metal tube, and there are guided wave radar with a by-pass measuring cylinder. These guided wave radars are mainly used to measure the level of storage tanks that are above ground level or where production equipment tower storage tanks can have side-by-pass pipes.
Common radar level gauge
The antenna of a common radar level meter is only an electromagnetic wave transmitting and receiving device, and its electromagnetic wave propagates freely through the gas phase after being emitted. Since the electromagnetic wave of the radar level meter is a high-frequency microwave signal with poor divergence and propagation, and the measured liquid is small in height from the radar level meter, the electromagnetic wave propagation process can be regarded as vertical propagation, so this radar level meter meets the requirements of liquid level ranging. Compared with the waveguide radar, the waveguide body is less, the cost is saved, and the installation is convenient, so it has been widely used in the measurement of higher liquid level such as storage tank.
According to different manufacturers of antenna, different types of radar level meter are made to adapt to different working conditions. The antenna of the common radar level meter used in the factory has four types: horn, drop shape (to prevent liquid volatilization and condensation), eccentric type (to prevent multiple reflection electromagnetic wave interference), and wide mouth horn (to prevent electromagnetic wave attenuation in gaseous medium).
Common radar level meter is mainly used in storage tank level detection. On-site installation and antenna are shown as follows: Due to the complexity of the measured object, high temperature and high pressure corrosion, as well as serious damage caused by foam, stirring, steam and many other reasons, radar level meter frequently fails, and the maintenance of the instrument is large, which seriously affects the production unit. Therefore, it is necessary to understand the daily fault problems of radar level gauge and its treatment methods. The troubleshooting method of radar level gauge is sorted out for you, hoping to be helpful to you.
Check whether the power supply is normal
If the production site finds that the radar level meter changes very slowly after the liquid level rises to a certain value, it should immediately check whether the power supply of the radar level meter is normal, and the relevant staff should also check the power supply of the radar level meter in detail in the daily maintenance, and whether there is normal output after the power supply. The liquid level changes slowly or does not change at all, it is necessary to check whether the fuse of the equipment is burned out at the first time, if there is no current output, it can be basically judged that there is a problem with the instrument, which should be replaced or repaired according to the situation. In addition, management should be strengthened in the process of instrument installation and debugging to prevent inaccurate instrument parameter Settings from affecting production. Relevant staff also need to strengthen daily maintenance work, regular outage maintenance, so as to ensure the normal operation of radar level meter.
Check whether the communication device works properly
Once the communication equipment is found to be abnormal, the radar debugging software can be installed to read the radar configuration data and monitor the status of the radar sensor. The main check radar sensor can accurately judge the difference between the reflected echo and the false echo, whether the intensity of the reflected wave meets the predetermined standard, if there is no problem in the above test, you need to check other electronic components, if the communication unit of the radar level meter is damaged, you need to replace the components according to the situation, so as to ensure the normal communication of the radar level meter. In the daily maintenance work, the relevant staff should also strengthen the check of the communication of the radar level meter, and the radar debugging software can be used to access the signal line and the regulator can be used to maintain the communication equipment of the radar level meter.
Service temperature
In order to make the normal measurement of the radar level meter, the internal temperature of the radar level meter should be ensured to be below 50 ° C. Generally speaking, radar level gauges are used to measure high temperature media. Therefore, the shell of the radar level meter is made of materials with strong heat resistance, so in general, the interior of the radar level meter will not exceed 50 ° C, if the internal electronic components exceed this value, it must not be cooled with ice water, ice water will not only play a cooling and cooling role, and even paralyze the radar level meter. A copper tube can be used to blow a small amount of wind into the radar head to scientifically reduce the internal temperature of the radar level gauge.
Display values are not accurate
Inaccurate display value is a common problem of radar level meter, leading to the cause of inaccurate display value, which may be the contrast of the initial setting is not appropriate, or because the plug-in connection of the display module is not correct, relevant staff should try to avoid this problem, once the display value is not visible, the initial setting of the radar level meter should be checked. And check whether the connection of the display module plug-in is normal. If the two items are normal, it is necessary to deeply check whether the output current of the radar level meter is normal. If the output current is greater than 22mA, it can be judged that the display module of the radar level meter is faulty and needs to be replaced in time. If the output current is less than 3.5mA, it can be judged that the electronic module of the radar level meter is faulty, and the electronic module of the radar level meter needs to be replaced in time.
The system displays an error message
The system of radar level gauge often displays error information, which is usually caused by the power cut off before the end of data storage, which needs to be calibrated and reset and re-calibrated. If the alarm is still sounded after the calibration reset and recalibration, the electronic module of the radar level meter needs to be replaced.
Antenna stained, crystallized
When dealing with the failure of light contaminated oil tank, the possibility of antenna contamination and crystallization should be considered first. The treatment method is to wear appropriate protective equipment after power failure, remove the radar and put it down at a tilt, wipe the dirt or crystallization with a rag, do not let the antenna bend and damage, pay attention to handling gently, avoid scraping with iron, so as not to damage the antenna skin.
Bloom
If the liquid level is low or no liquid level, the biggest reason may be that there is a bracket or pipe at the bottom of the test container, or steam is generated during the process, which forms a diffuse reflection of the radar wave and leads to the liquid level failure. At this time, it can be automatically restored after the process level is normal and restarted. The diffuse reflection caused by steam will automatically recover after the temperature is normal.