A butterfly disc is the rotating closure element inside a butterfly valve. This butterfly disc controls fluid flow by turning 90 degrees from fully open to closed. A well‑designed butterfly disc has a low profile to minimize pressure drop.

The butterfly disc is often made of ductile iron with a nylon or epoxy coating. A stainless steel butterfly disc resists corrosion in chemical and marine environments. The thickness of a butterfly disc determines its pressure rating (PN10 to PN100).

Butterfly discs with a eccentric shaft design reduce wear on the seat. A resilient‑seated butterfly disc uses a rubber lining for bubble‑tight shutoff. The disc face of a butterfly disc can be polished to a mirror finish for sanitary applications.

A lug‑type butterfly disc allows dead‑end service downstream. The wafer design of a butterfly disc fits between two pipe flanges. A butterfly disc with a keyed shaft connection prevents slippage under high torque.

The flow coefficient (Cv) of a butterfly disc varies with opening angle. A double‑offset butterfly disc cams away from the seat to reduce friction. The disc edge of a butterfly disc is ground to a precise angle for sealing.

Butterfly discs are available in sizes from 2 inches to 120 inches. A high‑performance butterfly disc handles temperatures up to 500°C. The compact design of a butterfly disc saves space compared to gate valves. Proper butterfly disc selection ensures reliable flow isolation and regulation.