Duplex Butterfly Valve

Large water and process lines often need a compact valve that fits between existing flanges without the weight of a full flanged body. Duplex stainless steel improves resistance to chloride-related corrosion, while wafer construction keeps the installation short and light. African Valve is a leading Duplex Butterfly Valve Manufacturer  in Africa, supplying South Africa, Nigeria, Egypt, Angola, other African markets and international projects.

Duplex Materials for Wetted Parts

Cast bodies may use ASTM A995 Grade 4A, while shafts, discs or forged parts may use ASTM A182 F51 or another compatible duplex grade. The body, disc, shaft, pins and retainers must be reviewed as a complete wetted assembly. ASTM A995 covers duplex castings for pressure-containing parts, while ASTM A182 covers forged valves and components.

Duplex material offers higher strength than common austenitic stainless steel and improved resistance to pitting and stress-corrosion cracking. Warm seawater, concentrated brine or severe crevices may require Super Duplex.

Seat and Offset Options

Concentric wafer valves commonly use resilient or fluoropolymer seats for moderate-temperature water and chemical service. Double-offset designs reduce seat rubbing during opening. Triple-offset valves use metal sealing geometry for higher temperature, frequent cycling or demanding leakage requirements.

The seat material and offset arrangement should be selected independently from the body material. A duplex body does not automatically make the valve suitable for severe temperature or abrasive duty.

Technical Specifications

Size Range: DN50 to DN1200

Pressure Ratings: ASME Class 150 to Class 600

Design Standards: API 609 and ASME B16.34 where applicable

Testing Standard: API 598

End Connections: Wafer, installed between specified flanges

Operation: Lever, gearbox, pneumatic actuator, hydraulic actuator or electric actuator

Body Material: ASTM A995 Grade 4A or equivalent duplex grade

Disc and Shaft Materials: Duplex stainless steel or project-specified compatible grades

Offset Options: Concentric, double offset or triple offset

Seat Options: EPDM, NBR, PTFE, laminated or metal seat

Actuator Mounting: ISO 5211

API 609 covers butterfly valves with double-flanged, lug and wafer body configurations.