Butterfly Valves

Concentric (centric) butterfly valves have the shaft running through the disc centre with a rubber elastomer seat - simple, low-cost, suitable for water and HVAC up to 200°C (limited by elastomer). Double-offset (high-performance) butterfly valves move the shaft behind the disc centreline, reducing seat rubbing and allowing PTFE soft seats for tighter shut-off and higher temperatures to 260°C. Triple-offset butterfly valves add a third geometric offset creating a cam-action, friction-free closure - the metal-to-metal seat provides ANSI Class VI (bubble-tight) shut-off from -196°C to +815°C and is inherently fire-safe.

API 609 covers butterfly valves for general refinery and petrochemical service. Category A includes wafer and lug types (clamped between flanges) - applicable to lug-body designs used in dead-end service and most standard applications. Category B covers double-flanged designs with raised face or ring joint flanges, rated for higher pressures and temperatures. Category B also requires more stringent testing - including seat leak test per API 598 - making it the specification of choice for critical or high-integrity shutoff requirements.

Triple-offset butterfly valves with metal-to-metal seats are inherently fire-safe - there are no elastomers to burn. Concentric and double-offset designs with elastomer or PTFE seats are NOT fire-safe in their standard form; fire-safe versions with secondary metal seat rings and graphite stem seals are available and tested to API 607. If your process handles flammable or combustible fluids, always specify API 607 fire-tested butterfly valves or use triple-offset metal-seated designs.

Standard production butterfly valves are available up to DN1200 (48") for double-flanged and triple-offset designs. Concentric wafer and lug designs are typically available to DN600 (24") in stocked production; larger sizes up to DN1200 on request. For special requirements above DN1200 - such as large dam, power plant inlet, or water authority trunk main applications - please contact our engineering team for a bespoke quotation.