Triple Offset Butterfly Valve

The Triple Offset Butterfly Valve is designed for isolation and flow-control duties where conventional resilient-seated butterfly valves may not provide the required sealing performance, temperature capability or service life. Its shaft and disc are positioned away from the valve body centreline, while the sealing surface incorporates a third angular offset. This geometry creates a cam-like movement that allows the sealing surfaces to separate quickly during opening and make controlled contact near final closure. The reduced rubbing helps limit seat wear, lower operating friction and maintain sealing performance during repeated cycling. African Valve is a top Triple Offset Butterfly Valve Suppliers in South Africa, supplying valves in different body materials, pressure classes, seat arrangements and operating configurations for industrial pipeline systems.

Engineering Design & Operation

The valve operates through a quarter-turn rotation of the disc. Its sealing arrangement uses three separate offsets. The shaft is displaced from the seat sealing plane, positioned away from the pipeline centreline, and the sealing cone is arranged at an angular offset relative to the valve body.

As the valve begins to open, this geometry moves the disc sealing surface away from the seat, reducing sliding contact. During closure, the disc approaches the seat through a controlled cam action and develops sealing contact close to the final closed position. This arrangement is particularly useful for laminated or solid metal seating.

Depending on the service, Triple Offset Butterfly Valves can be supplied in wafer, lug or flanged construction. Larger valves are commonly gear operated, while pneumatic, electric or hydraulic actuators may be selected for automated operation. Actuator sizing should account for differential-pressure torque, bearing friction, packing friction and final seating torque.

Technical Specifications

For large-diameter process and water pipelines, flanged construction is commonly selected where rigid pipeline connection and stable valve alignment are required. Flange drilling, face-to-face dimensions and pressure rating should be confirmed against the piping specification before final valve selection.

Materials & Components

• Body: ASTM A216 WCB / ASTM A352 LCB / ASTM A351 CF8 / ASTM A351 CF8M / ASTM A890 Duplex / ASTM A890 Super Duplex / Alloy Steel

• Disc: ASTM A536 Ductile Iron / ASTM A216 WCB / ASTM A351 CF8M / ASTM A890 Duplex / ASTM A890 Super Duplex

• Stem: AISI 316 / UNS S17400 (17-4PH) / UNS S31803 Duplex / UNS S32750 Super Duplex

• Seat: Metal-to-Metal / Laminated Metal / Stellite-Faced

• Shaft: AISI 316 / UNS S17400 (17-4PH) / UNS S31803 Duplex / UNS S32750 Super Duplex

• Bearing: Stainless Steel / PTFE-Based Composite / Bronze

• Retainer: AISI 316 / Carbon Steel / Stainless Steel

• Packing: Graphite / PTFE / Low-Emission Packing

• Fasteners: ASTM A193 B7 / ASTM A193 B8 / ASTM A193 B8M / ASTM A320 L7 with compatible ASTM A194 nuts

Applications

• Water Transmission

• Water Treatment

• Wastewater Treatment

• Irrigation

• Desalination

• Pumping Stations

• Power Generation

• Oil & Gas

• Mining

• Chemical Processing

• Steam & High-Temperature Services

Depending on valve construction, pressure rating and connection configuration, applicable requirements may include EN 593, ISO 5752, ISO 5208, EN 558, API 609 and API 598, where relevant to the selected design and project specification.

Testing may include shell pressure testing, seat leakage testing, dimensional inspection, disc and shaft alignment checks and complete open-close operation. For actuated valves, seating torque, actuator travel and limit-position settings should also be verified. PMI, NDT or additional material inspection may be specified for high-pressure, high-temperature or corrosive service.