Dual-plate check valve

ISO 10628-2 (group 22, check valves) / PIP PIC001 / API 594

Drawn as

Two vertical bars (a wafer between flanges) with two short plates hinged at the centre and opening downstream in a "<" shape, and a flow arrow above.

Meaning

Wafer check valve with two spring-loaded half-discs on a central hinge pin. Short and light, so common on compressor and pump discharges and on large water lines.

Variants

Many legends just use the general check symbol and write "dual plate" or "DPC"
Some draw a single vertical bar with a filled triangle