Butterfly Valves

The Double Offset Butterfly Valve—commonly called a High Performance Butterfly Valve (HPBV)—incorporates two geometric eccentricities to improve on the limitations of concentric resilient-seated butterfly valves. The first offset positions the disc rotation axis behind the plane of the seat, and the second offset positions the axis to one side of the pipe centreline. Together these two offsets cause the disc edge to separate from the seat immediately upon opening, eliminating continuous rubbing contact.

The practical result is dramatically extended seat life, lower break-away torque, and the ability to achieve ANSI/FCI Class IV through Class VI leakage tightness with both elastomeric and metal seats. Metal seats in stainless steel, Stellite, or Inconel enable the valve to operate in high-temperature steam, cryogenic, and chemically aggressive services.

This valve is a direct replacement for the Fisher 8532 / 8560 high-performance butterfly valve, Neles (Metso) L/LD-series HPBV, Samson STEVI butterfly valve, and Flowserve Durco high-performance butterfly valve.

The Triple Offset Butterfly Valve (TOBV) extends the eccentric butterfly valve concept to its logical endpoint: a geometry in which the seating and unseating motion is absolutely free of friction. The third offset—a cone-angle offset that makes the disc seating surface a section of an oblique cone—causes the disc to withdraw from and advance toward the seat along a pure conical path, with zero rubbing contact at any point during rotation.

This friction-free geometry has profound consequences for valve performance: seat life is measured in hundreds of thousands of cycles; there is no stick-slip torque peak at the closed position; and a hard metal seat ring—stainless steel, Stellite, Inconel, or laminated graphite—can be used without generating galling or accelerated wear. The result is IEC 60534 Class V or Class VI bi-directional leakage performance from an all-metal trim that tolerates temperatures from -196°C to +600°C and pressures through ANSI Class 2500.

This valve is a qualified replacement for the Fisher 8580 triple-offset butterfly valve, Metso/Neles triple-offset BFV, Cameron DYNATORQUE triple-eccentric butterfly valve, and Adams Armaturen triple-offset butterfly valve.