API 609 Butterfly Valves
What API 609 requires for butterfly valves — applicability, key and testing requirements, the alternative standards, and compliant supply with full certification.
What does API 609 require for butterfly valves?
API 609 (Butterfly Valves: Double-Flanged, Lug- and Wafer-Type, American Petroleum Institute (API)) sets the design, material and testing requirements for butterfly valves in its scope. API 609 is the dimensional and performance standard for butterfly valves in petroleum and natural gas service. It covers double-flanged (wafer), lug, and tapped-lug body designs in concentric (resilient seat), double-eccentric (high-performance), and triple-eccentric (metal seat) configurations. API 609 aligns butterfly valve design with ASME pressure classes and defines testing requirements for seat tightness.
Applicable Pressure Classes
Key Requirements
- Category A: concentric design, resilient seats (EPDM, NBR, PTFE), maximum ASME Class 150
- Category B: offset disc, fire-safe per API 607, Class 150–600
- Category C: triple-offset, metal-to-metal seat, Class 150–600, −29°C to +600°C
- Face-to-face dimensions per API 609 Table 1 (or ASME B16.10 for flanged)
- Shaft sealing - stem blowout prevention design mandatory
- Maximum operating torque at full differential pressure
Testing Requirements
- Shell test: 1.5× rated pressure
- Seat leakage test: 1.1× rated pressure, Class A or D per API 598
- Torque measurement at rated differential pressure
- Fire test per API 607 if fire-safe designation
Alternative Standards for Butterfly Valves
Other standards that also govern butterfly valves — useful for spec cross-acceptance.
Related Standards
Connected Engineering
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