Level gauge

01

Choose magnetic indicator or glass gauge

Barksdale explains that a magnetic rotary indicator keeps the visual indicator and switches isolated from the liquid, with the tank sealed from the surroundings, so spills from sight-glass breakage are eliminated. Its float housing is a pressure vessel mounted on the tank and built for the tank's pressure and temperature, in stainless steel or in PVC, PP or PVDF for corrosive service. [2]

ABB describes its LMG100 magnetic level gauge as a float, a chamber connected to the vessel and an indicator of shuttle or flags in a sealed tube beside it, coupled magnetically to the float. [1] Glass and tubular gauges instead show the liquid itself.

Give the supplier the liquid and its specific gravity range, operating and design pressure and temperature, connection centre-to-centre distance and flange rating, and whether switches or a transmitter are needed.

02

Size the float to the liquid's specific gravity

ABB's manual explains that the float is designed and weighted for the process liquid, sitting about 70–80% submerged, and that magnets and indicator are aligned so the indication matches the level at the reference specific gravity. If specific gravity falls, the float sinks deeper and the gauge reads lower than the true level; if it changes significantly in service, the float should be checked. [1]

Barksdale lists its LevelSite indicator for liquids down to a specific gravity of about 0.50, pressures to 310 bar and temperatures to 316 °C, which shows how much float and chamber design depend on the service. Give the supplier the lowest specific gravity the liquid will reach. [2]

03

Install it vertical and aligned

ABB states the chamber must be vertically level, or the float may rub the walls or move too far from the indicator and decouple. Barksdale warns that misaligned tank flanges distort the float chamber so the float may stick, that the indicator must be mounted vertically, and that the flags should be reset with a magnet before commissioning. [1] [2]

Ask for the connection centre distance tolerance, vent and drain arrangements, and whether the float is shipped inside the chamber or separately (ABB notes floats are labelled with top, specific gravity and chamber serial number). [1]

04

Add switches or a transmitter if needed

ABB explains that magnetically actuated limit switches can be clamped to the chamber and adjusted over the whole range, actuated by the float's magnet, and that a magnetostrictive transmitter can be added to an existing gauge for a remote signal. [1]

If you need a continuous 4–20 mA signal, decide whether to add a transmitter to the gauge or install a separate level transmitter.

05

Magnetic, magnetic-float and tank level gauges on the linked makers' sites

BCST lists customisable magnetic level gauges; Aister lists magnetic level gauges with flow meters; Dongrun lists magnetic float level gauges among level instruments; Aether lists level gauges among level sensors; Donjoy lists level gauges for tank equipment. [3] [4]

06

Chamber, float, indicator, glass and frame, connections, switches and transmitter

Tie the float row to your liquid: ABB designs and weights its float for the process liquid at about 70–80% submerged, so the order needs the specific-gravity range. [1]

07

Visible range, accuracy at your specific gravity, pressure, temperature, connection and material for a gauge order

Accuracy follows from how well the float matches the liquid's specific gravity, so ask for it at the lowest and highest SG in service; measuring range, protection class, supply voltage and weight have no published value here. [1]

08

Send the liquid, vessel and connection data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Liquid: [name; specific gravity range; temperature; corrosive or not; interface if any]
Vessel: [design pressure and temperature; connection centre distance; flange size and rating]
Gauge: [magnetic indicator or glass; indicator type; scale]
Options: [limit switches; transmitter and output; vent and drain valves]
Installation: [indoor or outdoor; insulation or heating]
Documents: [drawing; float SG label; pressure test certificate]

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