Magnetic level indicator principle

The magnetic level indicator working principle is widely used in level instrumentation. The interaction between float magnets inside the chamber and magnetic flags outside the chamber provide virtually maintenance-free, continuous level information. This type of level indicator doesn’t require power, making it ideal for a variety of applications across industries.

The magnetic level indicator working principle is based on the effects that one magnet has on nearby magnets. The mechanics are simple yet very effective, yielding reliable and repeatable level information for continuous monitoring and recording of fluid levels.

What Is the Magnetic Level Indicator Working Principle?

Like other level measuring instrumentation, a magnetic level indicator (MLI) uses a float that rests on the fluid’s surface, moving up or down as the fluid level rises or falls. The float is housed in a chamber attached to the tank. Since the chamber is affixed to the tank, the level of the fluid inside the chamber is always the same as the fluid level within the tank.

The difference between an MLI and other types of float-based level instruments is that the float is equipped with internal magnets. Just outside the chamber is a visual indicator consisting of a series of magnetic flaps or flags – painted one color on one side and a starkly contrasting color on the other side. As the float moves up or down, its internal magnets flip or rotate the magnetic flags, changing it from one colored side to the other.

Since the magnetic level indicator working principle relies on the interaction between magnets, MLIs do not need a power source. It is also virtually maintenance-free. The colored flags are easy to see, even from a distance, and are paired with a scale for precise readings. As for any level instrumentation, the size and material of the float are chosen according to the media, temperature, pressure, and density of the process media.

WIKA’s High-Performance Magnetic Level Indicators

WIKA has over 60 years of experience in this field, as our subsidiary KSR-Kueblerobtained one of the first patents for a magnetic level indicator. WIKA manufactures the WMI series, a complete line of high-quality magnetic level indicators that provide years of accurate level information. The float in each MLI is designed for each application. The materials of the float magnet are carefully chosen to minimize the size of the float and the chamber, and to provide the best coupling for the particular pipe wall material and thickness. Bypass chambers can be made of several different types of stainless steel and alloys (Hastelloy®, Inconel®, etc.) and other materials (Teflon™, PVC, etc.) to suit media and process temperature.

Model WMI magnetic level indicators are highly adaptable. They work from −320°F to 1,000°F (−195°C to 537°C), from full vacuum to 5,000 psi (344 bar), and for specific gravities as low as 0.35. Indicator flags can be red–white, yellow–black, or fluorescent. The scales can be indicated as imperial units (feet/inches), metric units (mm/cm/m), or percentage, or even customized to your specific requirements. You can also choose from several process connections, connection sizes, vents, and drains. Other useful options include high temperature insulation and cryogenic insulation.

WMI magnetic level indicators fit most industrial and commercial applications in:

  • Refinery and chemical industries
  • Energy and power plant technology
  • Feed water heaters and boilers
  • Oil and gas industries
  • Offshore exploration and drilling
  • Pipeline compressor applications
  • Pulp and paper
  • Food and beverage
  • Gas plants
  • Pharmaceutical

A level instrument based on the magnetic level indicator working principle can give you the accuracy and reliability you need. WIKA can help you find the best one for your application.



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