Butterfly Valves

The butterfly valve is a quarter-turn valve in which a disc mounted on a central shaft rotates within the pipe bore. A ninety degree turn moves the disc from fully closed, where its rim seats against a resilient or metal seat, to fully open, where it sits edge-on to the flow. The design is compact and light for its bore, needs modest operating torque and gives good throttling behaviour across much of its travel, which makes it a practical choice from medium bores upward where a gate or globe valve of the same diameter would be heavy and expensive.

Three geometries cover most duties. The concentric (resilient seated) design places the shaft on the disc and seat centreline and uses a full rubber liner for bidirectional bubble-tight shut-off at moderate pressure. The double eccentric (high performance) design offsets the shaft so the disc cams away from the seat as it opens, cutting friction and wear and extending seat life at higher pressure. The triple eccentric design adds a further offset and a metal seat for tight shut-off in high-temperature and fire-rated service.

Typical applications span water treatment and distribution, wastewater, HVAC and building services, marine systems and general industrial process lines. Butterfly valves are found on pump headers, treatment plant pipework, cooling water circuits and any large-bore line where space and weight favour a compact valve. Concentric types suit clean and lightly loaded water and air, while high-performance and triple-offset types are chosen for hydrocarbons, steam and demanding process conditions.

The governing product standards include EN 593 and API 609 for design and face-to-face dimensions, with flange drilling to EN 1092 or ASME B16.5 and testing to EN 12266 or API 598. Bodies are commonly ductile iron, cast or stainless steel, or aluminium bronze for seawater. Seat materials range through EPDM, NBR and PTFE to metal, selected for the medium and temperature. Actuation options cover lever, gearbox, electric, pneumatic and hydraulic, with position feedback where remote operation is required.

When specifying, confirm the bore, pressure rating, medium and temperature, the seat and body materials, the end connection (wafer, lug or flanged) and the actuation. Share these details on an enquiry and we can propose a configuration and supporting documentation for the duty.