Valve Standard Reference

API 609

American

Butterfly Valves: Double-Flanged, Lug- and Wafer-Type

API 609 is the dimensional and performance standard for butterfly valves in petroleum and natural gas service.

What is API 609?

API 609 (Butterfly Valves: Double-Flanged, Lug- and Wafer-Type) is an industrial valve standard issued by American Petroleum Institute (API). Covers butterfly valves from NPS 2" to 200" in pressure classes 150 to 600.

Issuing Body:
American Petroleum Institute (API)
Category:
design

Overview - API 609

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.

Scope

Covers butterfly valves from NPS 2" to 200" in pressure classes 150 to 600. Three categories: Category A (concentric resilient seat, general service), Category B (offset seat, high-performance / fire-safe), and Category C (triple-offset, metal-seat, high-pressure / high-temperature).

Vajra Industrial Solutions manufactures and supplies valves engineered to comply with API 609, each delivered with API 609 design conformance on data sheet and Hydrostatic test certificate as standard.

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Applicable Valve Types

Butterfly Valves - concentric (resilient seat)

Butterfly Valves - double-eccentric (high-performance)

Butterfly Valves - triple-offset (metal seat)

Applicable Pressure Classes

Class 150Class 300Class 600

Key Requirements - API 609

01.

Category A: concentric design, resilient seats (EPDM, NBR, PTFE), maximum ASME Class 150

02.

Category B: offset disc, fire-safe per API 607, Class 150–600

03.

Category C: triple-offset, metal-to-metal seat, Class 150–600, −29°C to +600°C

04.

Face-to-face dimensions per API 609 Table 1 (or ASME B16.10 for flanged)

05.

Shaft sealing - stem blowout prevention design mandatory

06.

Maximum operating torque at full differential pressure

Testing Requirements - API 609

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

Documentation Required for API 609 Compliance

API 609 design conformance on data sheet

Hydrostatic test certificate

API 607 fire test certificate (for fire-safe valves)

Material certificates (EN 10204 3.1)

Related Standards

Browse API 609 Compliant Valves

Technical Articles Referencing API 609

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API 609 by Valve Type

Part of the Vajra Valve Standards Library

Engineering references

Reviewed by Valve Standards Engineering, Vajra Industrial SolutionsDiscipline: Industrial Valve Standards & ComplianceLast reviewed: 20 June 2026

Connected Engineering

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We supply valves to API 609 with full certification documentation. Share your requirements for a 24-hour quote.

Relevant Products