API 609 vs API 608: When to Specify Butterfly vs Ball Valves

Technical guide · Supreme Valves India · 2026

Procurement teams specify API 609 butterfly valves for large-diameter isolation in water, HVAC, and many hydrocarbon utility lines. API 609 defines categories of butterfly valve design, face-to-face dimensions, and testing references — distinct from API 608 ball valves which address quarter-turn ball designs for different pressure-velocity service.

When to specify API 609 butterfly vs API 608 ball

Choose API 609 butterfly when: line size is large (typically 8" and above), weight and face-to-face matter, and the duty is primarily on-off isolation with acceptable pressure drop in the open position. Choose API 608 ball when: full port pigging is required, higher pressure class trunnion designs are needed, or fire-safe API 607 certification is mandated on the valve type.

Category A vs Category B

Category A concentric butterflies suit water and general industrial media. Category B offset designs (high performance) improve shutoff for higher pressures — see our high performance butterfly valve guide.

Testing and documentation

Factory tests reference API 598 unless the project ITP invokes additional pneumatic seat tests. Request EN 10204 3.1 MTCs with RFQ.