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A ball or flap against a seat, permitting flow one way only.
Also known as: Non-return valve, One-way valve, Ball against a seat
A check valve permits flow in one direction and blocks the reverse. Its symbol shows the mechanism rather than an arrow, so a reader can see *why* it is one-way rather than merely being told.
Marks a valve permitting flow in one direction only and closing against reverse flow.
Contexts: Technical drawing
Draws the mechanism — a ball or flap seated against a stop — rather than an arrow, so the direction is visible from the geometry.
Contexts: Technical drawing
A valve body with a small circle or flap drawn against an angled seat on one side, so the closing direction is evident from the drawing.
Valve symbols on a process diagram.