Level gauge glass

ISA 5.1-2009/2022 (primary element symbols) / PIP PIC001

Drawn as

A tall narrow rectangle beside the vessel, joined to it by two horizontal nozzles (top and bottom), with an LG bubble.

Meaning

Reflex or transparent sight glass showing the level directly. Common on older plant; many operators now use magnetic gauges, which are tagged LG too. No separate component; magnetic-level-gauge is the closest.

Variants

Stacked or overlapping glasses are drawn as two or three offset rectangles
Look-alike: magnetic level gauge (chamber with a float and a flag indicator)