The magnetic level indicator (MLI) or magnetic Level Gauges are used to measure levels of fluid using a floatable device that can float in both high and low density fluids. The magnetic Level Gauges were initially designed as an alternative to glass sight gauges but they are now being widely used in process industries, new constructions and plant expansions. The magnetic Level Gauges are often used in applications where the glass sight gauges are unsafe, environmentally risky or difficult to see.
Principles of operation of the magnetic Level Gauges
The magnetic Level Gauges use the principle of magnetic field coupling to provide information on fluid level, to activate a switch and to provide continuous level data. During measurement, the coupling allows the magnetic level gauge to measure without any direct contact between the indicator and the fluid in the vessel. The magnetic field consists of lines of flux surrounding the magnet and the magnet field acts on other objects with sufficient force to move the object.
In the MLI, the magnets within the float and the indicator are magnetically coupled to create a magnetic field which penetrates the chamber wall to couple with the magnetic field created by the magnets in the indicator flags that displays the levels. The float which is located inside the chamber tracks the surface of the liquid. Selecting the appropriate magnetic level gauge for a specific application depends on several factors that include the kind of process fluid, its specific gravity, operating temperature and pressure including the necessary level range.