API Std 609

Please note that the API Monogram Program effective date for the this document's next edition is October 2021. Until then, this edition will still be considered active and not historical.

This standard covers design, materials, face-to-face dimensions, pressure-temperature ratings, and examination, inspection and test requirements for gray iron, ductile iron, bronze, steel, nickel-based alloy, or special alloy butterfly valves.

The following two categories of butterfly valves are included.

a) Category A--Manufacturer's rated cold workingpressure (CWP) butterfly valves, usually with aconcentric disc and seat configuration. Sizes coveredare NPS 2 to NPS 48 for valves having ASME Class125 or Class 150 flange bolting patterns.

b) Category B--ASME Class and pressure-temperaturerated butterfly valves that have an offset seat andeither an eccentric or a concentric disc configuration.These valves may have a seat rating less than thebody rating. Sizes covered are listed below.


• For lug and wafer, Class 150: NPS 3 to NPS 48.
• For lug and wafer, Class 300 and Class 600: NPS 3 to NPS 48.
• For double-flanged long pattern, Class 150, 300, and 600: NPS 3 to NPS 36.
• For double-flanged short pattern, Class 150 and Class 300: NPS 3 to NPS 48.
• For double-flanged short pattern, Class 600: NPS 3 to NPS 24.

Valve configurations include double flanged, lug- and wafer-type with facings that permits installation between ASME and MSS flanges that conform to the standards and specifications listed in Section 2. Typical valve construction and nomenclature for valve parts are shown in Annex C.