Principle of magnetic flap level gauge and solutions to abnormalities

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Magnetic flap level gauges can be used to detect the liquid level of media in various equipment such as towers, tanks, vats, spherical containers, and boilers. Magnetic flap level gauges offer high sealing performance, prevent leakage, and are suitable for use in high-temperature, high-pressure, and corrosive environments. It overcomes the drawbacks of glass plate (tube) level gauges, such as poor indication clarity and susceptibility to breakage; it offers no blind spots in the entire measurement process, provides clear readings, and has a wide measurement range. Magnetic flap level gauges offer greater safety advantages over other types of level measuring instruments, as they enable local display of the liquid level without relying on any additional electronic devices. They are stable and reliable, with minimal fluctuations. These gauges are now widely used in pressure vessels in thermal power plants: high and low pressure deaerators, feedwater heaters, heat network heaters, high and low pressure heaters of the turbine units, condensers, and other heat exchangers all employ such level gauges. Furthermore, in cases where the working medium of the heat exchanger is a liquid that vaporizes easily, with pressures ranging from vacuum to 2.5 Mpa and temperatures ranging from 40°C to 390°C, the regular maintenance of the level gauge as well as the accuracy of its readings play a crucial role in ensuring the safe operation of pressure vessels. Next, Chengfeng Instruments will provide you with a detailed overview of the knowledge related to magnetic flap level gauges. Let’s take a look! Magnetic flap level gauge I. Working principle of magnetic flap level gauge The operating principle of the magnetic flap level gauge – also known as a magnetic float level gauge – is based on the principles of buoyancy and magnetic coupling. As the liquid level in the container under test rises or falls, the float in the main tube of the level gauge moves up or down accordingly. The permanent magnet inside the float transmits a magnetic signal to the on-site indicator, causing the red and white flip column to rotate 180°. When the liquid level rises, the flip column changes from white to red; when the liquid level drops, it changes from red to white. The boundary between red and white on the indicator represents the actual height of the liquid level in the container, thereby enabling the indication of the liquid level. The relationship between the rotating column and the float in a magnetic flap level gauge. II. Factors to consider when selecting a level gauge: 1. The substance being measured, such as its physical and chemical properties, as well as the operating pressure and temperature, installation conditions, and the rate of change in liquid level. 2. Measurement and control requirements, such as measurement range, measurement (or control) accuracy, display method, on-site indication, remote indication, interface with computers, safety and corrosion resistance, reliability, and ease of installation. 3. The demagnetization of magnetic materials also needs to be taken into account; demagnetization can prevent the level gauge from functioning properly, and the measurement results may be inaccurate as well. III. Features of magnetic flap level gauges 1. Wide measurement range, not limited by the height of the container. 2. The indication is novel; the readings are intuitive and prominent, and the direction of the indicator can be adjusted according to the user’s needs. 3. Suitable for measuring the level and interface of liquid media in containers. In addition to on-site indication, it can also be equipped with remote transmitters and alarm switches, offering comprehensive detection functions. 4. Simple structure, easy to install and maintain, corrosion-resistant, power-free, and explosion-proof. IV. Problems with inaccurate indication of magnetic flap level gauges>>>>1. Methods for diagnosis (1) The container is always in operation, but the liquid level within it remains fixed at a certain point. (2) When the load on the container increases or decreases, the liquid level in the container remains unchanged. (3) The local level gauge does not match the pressure difference level gauge on the indoor display screen. >>>>2. Reasons: (1) The water level in the container rises or falls too quickly; in other words, the float moves up or down too fast, and the magnetic flap does not have time to turn. (2) The center of gravity of the magnetic flap is not at the center point; as the magnetic float rises and flips, when it rises again the flap returns to its original position, so no indication of water level is shown. (3) There are too many impurities in the water in the container, which adhere to the surface of the maglev. This causes a decrease in the magnetism of the maglev system; when the maglev rises, it is unable to drive the flap to rotate. (4) Different blockages in the liquid-phase conduit of water cause the actual water level in the container to rise. The maglev does not rise accordingly. >>>>3. Solution (1) Try to ensure that the water level in the container rises or falls not too quickly. (2) The magnetic flap of the water level gauge has its center of gravity not at the center point. The manufacturing quality does not meet the standards; it should be replaced. (3) If the water quality is substandard, it should be flushed regularly. >>>>4. Maintenance (1) No solid impurities or magnetic contaminants should enter the level gauge cylinder, as this could cause jamming of the float and reduce its buoyancy. (2) Depending on the conditions of the medium, the main pipeline can be cleaned regularly to remove deposits and impurities inside it. (3) After cleaning the level gauge or replacing the float, open the drain flange. When installing the magnetic float, make sure that the magnetic end, which is the heavier one, faces upward; it must not be installed upside down. (4) For low-temperature and LPG-specific products, the level gauge body is insulated with a vacuum jacket; care should be taken during installation and use to avoid damaging the jacket, so as not to affect product quality.