Magnetic level gauges: matching materials, accessories and applications

01 / Passive indication with configurable signals

A magnetic float follows the liquid inside a chamber and couples to external flags. This is why the same instrument is often called a flag-type gauge. The mechanical local display needs no power; transmitters or heating accessories may still require a supply.

Compatible switches and a transmitter can combine field inspection with control-room monitoring. Unlike a glass gauge, the display does not rely on seeing through the liquid, which helps with colored liquids that allow free float travel. It does not show actual color, turbidity or bubbles, and needs an unobstructed chamber and freely moving float.

DOERS ENGINEERING / MAGNETIC

Change the level. Observe magnetic coupling.

01 Vessel level · 02 Magnetic float and chamber · 03 External flags

Ideal steady-state illustration, not measured product performance. Red/white indicates liquid/gas position; density, field strength, inertia and faults are not simulated.

02 / Match the service to a configuration

02 / Match the service to a configuration
Application	Configuration to consider	Selection condition
Water / cooling-water tanks	Metal chamber and compatible float; add scale, switches and transmitter as needed.	Check density, span, connections and drains; prevent deposits in the bypass.
Clean oils / low-density solvents	Select a float against minimum density and check metal, polymer or lining compatibility.	No conductivity requirement, but density, temperature and hazardous-area classification affect configuration.
Acids / alkalis / corrosive service	Evaluate PP, PVC, PVDF, FRP or PTFE/PFA-lined chamber configurations.	Check concentration, temperature, pressure and cleaning fluids, including float and gasket compatibility.
Outdoor freezing conditions	Consider anti-freeze heating, insulation or a jacket.	Specify minimum ambient temperature, supply and heating control. Loss of power can still allow freezing.
Solidifying / crystallizing liquids	Half/full jacket with draining and cleaning provisions.	Establish temperature and cleaning frequency. Avoid float technology where deposits cannot be controlled.
Walk-by inspection without color observation	Flag indicator and scale, with separately specified alarms/outputs.	Assess distance, mounting height and lighting; visibility is not unlimited.

03 / Separate indicator housing, chamber and float

Our 562, 563 and 564 gauges use aluminum alloy, 304 stainless steel and 316L stainless steel indicator housings, respectively. They do not define the complete wetted assembly. Specify the chamber, float, gaskets and valves separately.

Metals are not always more corrosion-resistant, and polymers are not automatically suitable at higher temperature or pressure. We help match these materials to your fluid and operating conditions; they are not universally interchangeable combinations.

03 / Separate indicator housing, chamber and float
Part / material option	Why consider it	What to verify
Chamber: 304 / 316 / 316L stainless	Mechanical and pressure/temperature requirements in compatible water, oil or process service.	Chlorides, chemical composition, welding and assembly ratings; stainless is not a universal corrosion specification.
Chamber: PP / PVC / PVDF / FRP	Non-metallic options for some corrosive services.	Chemical compatibility, temperature derating, pressure, nozzle loads and outdoor exposure; polymers differ.
Chamber: 316 stainless with PTFE/PFA lining	Metal structure with a separately selected wetted barrier.	Lining integrity, connection seals, float compatibility and vacuum/pressure/temperature conditions.
Float: 316 / 316L, titanium, PP, PVC, FRP, PVDF	Match chamber size, minimum density and chemical compatibility.	Float pressure rating and density range. Titanium is not suitable for every acid.

04 / Choose accessories by task

04 / Choose accessories by task
Task	Accessory / product	Specify before ordering
High/low alarms	528 / 529 reed switches	Positions, quantity, SPST/SPDT, latching behavior and load. A switch is not automatically an independent safety system.
Continuous control-room signal	531 4–20 mA transmitter	Compatible mounting, span, scaling, supply and wiring.
Digital communication	532 HART transmitter	Verify chamber compatibility, host HART support and supplied version.
Cold / viscous service	U560A anti-freeze heater, half/full jacket options	Heat source, temperature control, insulation, cleaning and actual accessory/environment ratings.
Reading and maintenance	A560 scale, vent/drain/isolation valves and junction box	Units, valve materials and orientation, removal space; verify ingress/hazardous-area ratings for the actual supplied accessories.

05 / When to compare another technology

Solids, fibres, deposits and crystals can obstruct the float. Blocked connections may leave the flags showing a plausible but stale value. If a clear chamber cannot be maintained, compare ultrasonic, radar or another suitable method rather than merely adding a transmitter.

For color, mixing behavior or liquid interfaces, compare the 542 transparent gauge. Magnetic indication does not provide that visual information. Interface floats need a separate density-difference and configuration assessment; an ordinary single-level float is not automatically suitable.

Provide minimum operating density, viscosity, composition/concentration, operating/design pressure and temperature, connection centers and signal requirements to specify a workable assembly.

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We help match the model and accessories to your fluid, pressure, temperature, installation and signal requirements. Share your application details with our technical team for a configuration review.

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