Factors to consider when choosing a magnetic flap level gauge

The following factors should be considered when selecting a level meter: (1) measurement object, such as the physical and chemical properties of the measured medium, as well as the working pressure and temperature, installation conditions, speed of liquid level change, etc.; (2) measurement and control requirements, such as measurement range, measurement (or control) accuracy, display mode, on-site indication, remote indication, interface with computer, safety and corrosion resistance, reliability and construction convenience. The　 
　　commonly used level meters and selection points in water supply projects are as follows:　 
　　a. Float-type level meter　 
　　puts a hollow float in the liquid. When the liquid level changes, the float will produce the same displacement as the liquid level change. The displacement of the float can be measured mechanically or electrically, with an accuracy of ±(1~2)%. This level meter is not suitable for high-viscosity liquids. Its output end has switch control and continuous output.　 
　　In the design of water treatment plants, this type of level meter is often used for liquid level measurement in water collection wells to control the automatic start and stop of drainage pumps.　 
　　b. Static pressure (or differential pressure) level gauge　 
　　Since the static pressure of the liquid column is proportional to the liquid level, the liquid level can be measured by measuring the static pressure of the liquid column on the reference surface with a pressure gauge. The pressure or differential pressure range is calculated according to the density of the measured medium and the liquid measurement range, and then a pressure gauge or differential pressure gauge with appropriate range, accuracy and other performance is selected. The accuracy of this level gauge is ±(0.5~2)%.　 
　　c. Capacitive level gauge　 
　　inserts electrodes into the container. When the liquid level changes, the medium inside the electrode changes, and the capacitance between the electrodes (or between the electrode and the container wall) also changes accordingly. The change in capacitance is then converted into a standardized DC signal. Its accuracy is ±(0.5~1.5)%.　 
　　Capacitive level gauges have the following advantages: the sensor has no mechanical moving parts, simple and reliable structure; high accuracy; low power consumption at the detection end, fast dynamic response; easy maintenance and long service life. The disadvantage is that the unstable dielectric constant of the measured liquid will cause errors. Capacitive level gauges are generally used for level measurement of regulating tanks, clear water tanks, etc.　 
　　When the measuring range does not exceed 2m, rod-shaped, plate-shaped, and coaxial electrodes are used; when it exceeds 2m, cable-shaped electrodes are used. When the measured medium is water, an electrode with an insulating layer (polyethylene can be used) is used.　 
　　d. Ultrasonic level meter　 
　　The sensor of the ultrasonic level meter consists of a pair of transmitting and receiving transducers. The transmitting transducer emits ultrasonic pulses facing the liquid surface, and the ultrasonic pulses are reflected back from the liquid surface and received by the receiving transducer. The distance between the sensor and the liquid surface can be determined based on the time from transmission to reception, which can be converted into the liquid level. Its accuracy is ±0.5%.　 
　　This level meter has no mechanical moving parts, high reliability, simple and convenient installation, non-contact measurement, and is not affected by the viscosity and density of the liquid. Therefore, it is mostly used for liquid level measurement of medicine pools, medicine tanks, mud drainage pools, etc. However, this method has certain blind spots and is expensive. 
　　In addition, the host mentioned the magnetic flap level meter, and the demagnetization of magnetic materials must be considered. Demagnetization causes the level meter to not work properly, and the measurement results cannot be trusted by the operator. Magnetic flap level gauges are recommended for use in high places where it is not easy to approach to read the liquid level, such as towers. However, you cannot only set up a magnetic flap level gauge, you must also set up a glass plate level gauge, and the magnetic flap level gauge can only be used for reference. In addition, for more important liquid levels (related to process safety and equipment safety), such as drum liquid level, it is not recommended to use a magnetic flap level gauge. 
　　The magnetic flap level gauge must also consider the corrosiveness and service life of the medium, because the magnetic flap is a magnetic float installed in the process medium, and the corrosion resistance and thickness of the float must also be considered! 
　　 Magnetic flap level gauge maintenance
　　1. No solid impurities and magnetic impurities should enter the cylinder of the level gauge to avoid blocking the float and reducing the buoyancy. 
　　2. According to the medium conditions, the main pipe can be cleaned regularly to remove sediment impurities in the pipe. 
　　3. After cleaning the level gauge or replacing the float, open the drain flange. When installing the magnetic float, pay attention to the heavy end with the magnet facing up, and do not install it upside down! 
　　4. For low-temperature and liquefied gas special products, the main body of the level gauge is insulated with a vacuum jacket. Be careful not to damage the jacket during installation and use to avoid affecting product quality. 
　　 Installation
　　1. The level gauge must be installed vertically to ensure that the float assembly can move up and down freely in the main pipe. 
　　2. No magnetic conductors are allowed to approach the main body of the level gauge, otherwise it will directly affect the correct operation of the level gauge. 
　　3. After the level gauge is installed, it is necessary to use magnetic steel to calibrate the guide of the flip column once so that the display below zero is red and the display above zero is white. 
　　4. When the level gauge is put into operation, the valve of the lower liquid pipe should be opened first to allow the liquid medium to enter the main pipe smoothly to avoid the liquid medium carrying the float assembly to rise rapidly, causing the flip column to fail and flip randomly. If this phenomenon occurs, the magnetic steel can be used to recalibrate after the liquid level is stable. 
　　5. In order to prevent the float assembly from being damaged during transportation, the float assembly is removed from the main tube of the level gauge before leaving the factory. After the level gauge is installed, open the bottom drain flange and reinstall the float assembly into the main tube. Note that the heavy end of the float assembly should face upwards and cannot be installed upside down. If the float assembly has been installed in the main tube at the factory, in order to ensure that the float assembly is not damaged 
　　during  , we use a soft card to fix the float assembly in the main tube. When installing, just pull out the soft card.
　　6. According to the medium conditions, the drain flange can be opened regularly to clean the sediment in the main tube.