Spectacle blind, closed (blank in line)

ISO 10628-2 (groups 24-25, fittings and piping) / PIP PIC001 / ASME B16.48

Drawn as

A figure-8 between two flange bars: the solid (filled) blank sits on the pipe, and the open ring is off the line.

Meaning

Spectacle blind in the closed position: positive isolation, nothing passes. Typical on spare connections, start-up lines and vessel isolations.

Variants

Some legends write "NC" beside it
A filled circle without a ring is a spade (line blank)
The offset form (figure-8 beside the flange pair on a short stem) means the same thing: see spectacle-blind-offset