• Introduction

A Magnetic Level Indicator (MLI) is a versatile and highly visible liquid level measurement solution designed to provide real-time monitoring in tanks and pressure vessels without the risks associated with traditional glass gauges. It operates on the principle of magnetism and buoyancy, utilizing a float containing an internal magnet assembly that rises and falls with the liquid level inside a bypass chamber. This internal magnet interacts through the chamber wall with an externally mounted indicator—typically a series of bi-color magnetic flaps or a follower—causing them to flip and change color to represent the current liquid height. Because the process fluid is completely contained within the metallic or plastic piping and never touches the indicator itself, MLIs offer a leak-proof, low-maintenance, and robust alternative for high-pressure, high-temperature, or chemically aggressive industrial environments.

  • Working Principles

The working principle of a Magnetic Level Indicator (MLI) is based on the physical laws of buoyancy and magnetism, specifically utilizing a “bypass” configuration to mirror the tank’s liquid level. A float containing a powerful internal magnet assembly is designed to match the specific gravity of the process fluid, allowing it to move vertically within a non-magnetic bypass chamber as the liquid level fluctuates. Outside this sealed chamber, a column of bi-color magnetic flags or a follower is mounted; as the float moves, its magnetic field penetrates the chamber wall to rotate the flags 180 DEG C or move the follower. This magnetic coupling ensures that the indicating scale changes color—typically from white to red—to provide a clear, high-visibility representation of the liquid level without any direct contact between the process media and the indicator, effectively eliminating the risk of leaks or glass breakage.

  • Applications

Magnetic Level Indicators (MLIs) are utilized across various sectors due to their ability to handle extreme conditions while maintaining a seal between the process fluid and the operator. Key applications include:

  • Oil and Gas Industry

  • Chemical Processing

  • Power Generation

  • Water and Wastewater Treatment

  • Pharmaceutical and Food Production

  • Petrochemical Plants

  • Cryogenic Services

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