Analysis of the characteristics of magnetic flap level gauges

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　　As is well known, all instrumentation products are manufactured based on relevant scientific principles. As the name suggests, a magnetic flap level gauge uses the magnetic properties of metals to measure liquid levels. Let’s take a look together at what a magnetic flip-top level gauge really is. Specifically, the structural principle of a magnetic flip-top level gauge is based on the principles of buoyancy and magnetic coupling; as the liquid level in the container being measured changes, the magnetic float inside the gauge’s tube rises or falls accordingly. The permanent magnets contained within the float transmit magnetic forces to the magnetic flip columns, causing the red and white flip columns to rotate 180°. When the liquid level drops, the flip columns change from red to white; when the liquid level rises, they change from white to red. The point where the red and white flip columns meet on the panel indicates the actual height of the liquid level inside the container. 　　We know that in a magnetic flap level gauge, the magnetism arises because certain small circuits within the material arrange themselves in a particular way for some reason (such as keeping a non-magnetic iron piece in a constant magnetic field for an extended period), resulting in a greater total magnetic field strength in one direction than in the other directions, which is what gives it magnetic properties. High temperatures cause the molecules within a magnet to move more vigorously, disrupting their arrangement; this results in the magnet losing its magnetic properties. This was discovered by Marie Curie, and that’s why the temperature at which a magnet loses its magnetism due to high temperatures is called the Curie temperature of that magnet. This demagnetization point is a very important concept in the manufacturing and use of magnetic flip plates. Due to the existence of this demagnetization point, magnetism does not persist indefinitely in all magnetic materials; it is closely related to temperature. 　　Generally, magnetic materials have a critical temperature Tc; above this temperature, due to the intense thermal motion of atoms at high temperatures, the arrangement of atomic magnetic moments becomes chaotic and disordered. Below this temperature, the atomic magnetic moments align neatly, resulting in spontaneous magnetization and the material becoming ferromagnetic. If the temperature is too high, it will cause the magnetism inside the float or tilt column to become demagnetized. When purchasing a product, users need to provide the instrument manufacturer with the exact medium temperature in order to determine the appropriate high-temperature float to use. 　　Regarding how to deal with the demagnetization issue of magnetic flap level gauges, attention can be paid to the following aspects: First, in high-temperature magnetic flap level gauges, the magnetic float can experience demagnetization over time, and this demagnetization leads to the failure of the gauge. High-temperature magnetic flap level gauges (especially those designed for high temperature and pressure) are typically used in environments where the temperature exceeds 180 degrees Celsius. Therefore, from a design perspective, it is necessary to select the appropriate hard magnetic material. For example, magnetic materials with a Curie temperature that is at least 20% higher than the operating temperature should be chosen, to ensure that the residual magnetism remains above the critical value after five years (the coupling critical value required for the magnetic flap level gauges I design and manufacture is around 1400 gauss). Secondly, from a production perspective, the following points need to be taken into account when manufacturing the magnetic floats: 1. During the product manufacturing process, cooling measures must be employed during welding (TIG welding) in order to prevent the temperature of the magnetic material of the float from exceeding its Curie temperature. 　　2. Fill the magnetic float inside the measuring tube of the instrument with an inert gas (such as argon). Thirdly, from the user’s perspective, the following points need to be addressed: 1. Select the appropriate model when placing an order, ensuring that the operating temperature does not exceed the nominal temperature specified for the magnetic flap level gauge; 2. During use, it is necessary to constantly monitor how well the level gauge is functioning (whether it is operating properly), and also keep track of the actual temperature of the medium. I have seen situations where the actual operating temperature is higher than the temperature indicated in the specifications, as the people who developed those specifications may have overlooked certain factors.