Sight glass (sight flow indicator)
ISO 10628-2 (groups 24-25, fittings and piping) / PIP PIC001
Drawn as
Two concentric circles on the line (a viewing window).
Meaning
In-line window to see that liquid is flowing: pump seal flush, lube oil, chemical injection. ISA calls it FG (flow glass). Becomes sight-glass.
Variants
- Some legends draw a circle with two short vertical bars
- ISA style: a bubble with FG
- A level gauge glass on a vessel is LG, not this
Tags
SG · FG · FG