Magnetic Level Gauges: Versatile and Highly Visible Tank Level Measurement

Magnetic level indicators are used widely in liquid level measurement. Also known as Magnetic Level Gauges, or “Mag Gauges,” they are used, generally, to provide a display of liquid level in tanks and other vessels. They are popular solutions because they are visible from far distances and they have a non-invasive design which reduces the possibility of points points and the risks of fugitive emissions.

Magnetic level gauges are often employed in along with magnetostrictive, guided wave radar, or other measurement means to provide a reliable local display of liquid level. They can also be used to provide an an electrical signal that can be transmitted to recording instrumentation or controllers.

"Mag Gauge" construction is fairly simplistic – here's how it works: A magnetic float, designed for the specific gravity of the material being measured, rides inside a vertical pipe on top of the process media. A gauge with a magnetically coupled visual indicator is fastened to the pipe. As the media inside the pipe rises and falls, the visual indicator moves in the same fashion.

The features of Magnetic level gauges include:

• Visual tank level indication. 
• Wide operating temperature and pressure range.
• Continuous level measurement.
• No electric power required for operation.
• Low maintenance. 
• Easier to read from greater distance than glass sight gauges. 
• Can be applied to wide fluid level ranges with a single instrument. 
• Break resistant, sturdy.
• Wide range of construction materials available.
• External mounting of ancillary indicators, switches, and transmitters with isolation from process media. 

There are a number of options available so you can customize the level indicator for each specific application. The best way to proceed is to combine your process knowledge with that of a product specialist. Collectively, you'll be able to achieve an effective solution to your application challenge.

Magnetic Level Gauges for Visual Tank Level Monitoring and Control

Magnetic Level Gauges
(courtesy of Hawk Measurement)

Magnetic Level Gauges (MLG) are widely applied in the monitoring and process control of liquid level and interface for many industries; such as petroleum, chemical, power, paper, metallurgy, water treatment etc. They are suitable for real time, precise, safe and reliable continuous measurement of process level.

Based on the principle of magnetic coupling and buoyancy, the magnetic level gauge provides real-time measurement for level and interface. The Magnetic Level Gauge (MLG) is connected to a process vessel. Within the chamber is a float containing a 360° magnetic ring. Outside of the chamber is an indicator equipped with a vacuum glass tube, which contains a bi-colored two-face magnetic bargraph. In response to the level movement, the float moves accordingly, forcing the magnetic bargraph to turn and change color. True liquid level is indicated or “read” from the corresponding point on the measuring scale. The indicator uses hermetical sealed glass tube technology to clearly indicate the level, which eliminates the common problems of glass gauges, such as vapor, condensation and liquid leakage etc.

Typical Applications:

• Boiler: Steam drum liquid level
• Power generation: Auxiliary machinery liquid level (HP reheater, LP reheater, deaerator, condenser and heating network heater etc), chemical water
• Coal Chemical: Methanol, dimethyl ether, synthesis ammonia/urea, MTO, CTL, SNG
• Silicon industry: Organic silicon, polycrystalline silicon
• Petroleum and petrochemical: Oil and gas, ethylene, trimerization and etc.
• Fine Chemicals: Methane oxide, epoxy ethane, aniline, PTMEG, BDO, carbon fiber, POM,acetic acid, styrene, rubber, crude benzol refining
• Others: Metallurgy, paper-making, water treatment, biological, pharmaceutical, food and beverage etc.

Magnetic Level Gauges have a simple modular design, composed a main chamber, a float and an

Mag level gauge construction

indicator.

Typical main chamber features:

• ANSI standard design or special manufacture
• Multi-forms installation and process connection
• Chamber Material: 304/304LSS, 316/316LSS, 317SS, 321SS, 347SS, Ti2, Hastelloy C-276, Zr-702, Nickel-6, 304+PTFE, CPVC and PP.

Typical float features:

The float is the key component of the level gauge, which magnetically couples to the outside indicator, liquid level switch and transmitter.

• Hermetically sealed incompressible
• 360° magnetic ring
• 316LSS, Hastelloy C-276, Zr-702, Nickel 6, Ti2, 304SS+PFA, grade V aviation titanium alloy and other materials
• Special structure and precision manufacturing technology of pulse TIG and laser weld
• Range of temperature: -320 to 1000°F (-196 to 538°C)
• Range of pressure: vacuum to 600 psig (vacuum to 42MPa)
• Suitable for harsh working conditions, such as HTHP, cryogenics and strong corrosion.

Relationship of float, chamber and indicator.

Typical indicator features:

• 316SS or aluminium ruler
• Hermetically sealed glass tube with no contact with medium
• Magnetic bargraph is made from special high and low temperature - resistant materials
• Magnetic bargraph is mechanically interlocked to avoid random rotating
• Selectable engineering units
• Immune to oxidation, corrosion and the effects of dust