API · ASME · DIN · EN standard industrial valves
Butterfly Valves
Quarter-turn valves with a rotating disc, compact for large diameters in utility and process isolation.
Last updated: 2026-11
Family specifications
| size range | DN40 to DN2000 |
|---|---|
| pressure class | PN10 to PN63, ANSI Class 150 to Class 1500 |
| body materials | WCB (ASTM A216), CF8, CF8M (ASTM A351), F316L (ASTM A182), F51/2205 duplex (ASTM A182), F53, F55/2507 super duplex (ASTM A182), C95400, C95800 aluminium bronze (ASTM B148) |
| end connections | Wafer, Lug, Flanged |
| leakage class | Resilient seats can often achieve bubble-tight shutoff, typically equivalent to ANSI/FCI Class VI leakage performance; many metal-seated designs target lower leakage classifications such as Class IV. |
| design standards | API 609, ASME B16.34, MSS SP-67 (where applicable), EN 593, BS 5155 |
| testing standards | API 598 |
| designs | Wafer, Lug, Double Flanged, Double Offset (double eccentric), Triple Offset (triple eccentric), High Performance Wafer/Lug |
| offset geometry sealing principle | Concentric designs are position-seated with continuous disc-seat contact; double offset adds a camming action so the disc contacts the seat only in the final 5-7% of closure; triple offset uses a conical inclined sealing geometry where disc and seat engage without rubbing and tight shutoff comes from metal-to-metal wedging, not seat compression |
| seat family tiers | Resilient seats (EPDM/NBR/FKM): bubble-tight shutoff, temperature limited by the elastomer. Polymer seats (PTFE/TFM): near-universal chemical compatibility but cold flow/creep under sustained load. Metal seats (stainless, hard-faced, laminated): zero elastomers, extreme temperature and pressure, torque-seated |
| seat material chemistry windows | EPDM: water, steam, dilute acids and alkalis, ozone — fails (swelling, seal loss) with mineral oil, diesel, gasoline and most hydrocarbons. NBR: oils and fuels, but weak in ozone, sunlight, hot water and steam. PTFE: near-universal chemical inertness, but creeps/cold-flows under sustained load. FKM/Viton: higher temperature plus oils and aggressive fluids, but poorer low-temperature flexibility and unsuitable for some amines, hot water/steam conditions or strong bases |
| seat rating vs body rating | API 609 notes some butterfly valve categories can have seat ratings different from body ratings — never assume body pressure rating equals seat pressure rating |
| potable water approval compound level | Drinking-water approval (WRAS, ACS, WaterMark, NSF/ANSI/CAN 61) attaches to the exact valve, coating and wetted components, not to the material name alone |
| throttling sizing rule | Size a throttling butterfly valve as a control valve: check required Cv at minimum, normal and maximum flow; an oversized valve passes normal flow at a small opening, leaving little useful actuator travel |
| partly open failure chain | Partly-open discs accelerate flow around the edges; in liquid service pressure can fall below vapour pressure causing cavitation (noise, erosion, downstream piping damage); the uneven pressure field creates dynamic torque that may open or close the valve; an actuator sized only for seating and friction may not hold position, causing hunting |
| no universal min opening | No single minimum opening angle applies to every design and service; fixed rules such as 'never below 20 degrees' are useful warnings but not a substitute for sizing — use manufacturer Cv, cavitation and torque data to establish the acceptable operating window |
| flow direction and bidirectionality | Most butterfly valve designs are bidirectional, though some designs have a preferred flow direction; in throttling duty flow direction changes disc loading and seat behaviour |
| seat construction | Molded tongue-and-groove elastomer seat construction is used in hydronic resilient-seat executions: the molded profile lowers operating torque and provides bubble-tight shutoff. |
| lifecycle testing example | Hydronic resilient-seat executions are cycle-tested to 30,000 full strokes and 300,000 repositions and meet ANSI 125 standard. |
| throttling dp guidance | For modulating (throttling) duty the pressure drop across the valve is recommended to be no higher than 29 PSI or sized to match the design pressure drop; 3, 4, 5, and 6 PSI are commonly accepted for modulating applications. |
| hydronic body materials | Cast iron body to ASTM A126 Class A is used in hydronic resilient-seat executions. |
| api609 category a | API 609 Category A covers manufacturer-rated cold working pressure (CWP) valves, usually with a concentric disc and seat configuration, commonly associated with ASME Class 125 or Class 150 flange bolting patterns in NPS 2 through NPS 48. |
| api609 category b | API 609 Category B covers pressure-temperature-rated valves with an offset seat and either eccentric or concentric disc configuration, with size coverage such as NPS 3 through NPS 24 for Classes 150, 300, and 600. |
| face to face series landscape | Butterfly face-to-face dimensions follow standardized series: JIS B 2002 series 46 (double-flanged long pattern) and series 42/1, DIN 3202 F4, EN 558 series 109/110/20/13, ISO 5752 long series, ASME B16.10, BS 5155 short and long, and MSS SP-68 for lug and wafer types, with double-flanged short pattern options. |
Ordering & documentation
Documents
Ask for the documentation set with the inquiry — typical items (material certificates, test reports to the listed inspection standard, dimensional drawings) are confirmed and supplied with the quotation.
Quotation
Send the medium, temperature, pressure, size and connection for a quotation-ready inquiry. Lead time, MOQ and price are confirmed at quotation, together with the documents to be supplied with the order.
Sample & supply
Supply terms, order quantities and lead time are agreed per order — state the destination country and required schedule with the inquiry.
Storage & shipping
Store valves with seats and seals protected from UV, ozone and deformation, and keep end-face protectors on until installation; storage limits and shipping arrangements for the selected materials are confirmed at quotation.
Frequently asked questions
What standards govern the design and testing of butterfly valves?
The published specification for this family lists API 609, ASME B16.34, MSS SP-67 (where applicable), EN 593, BS 5155 as the design standards. Testing follows API 598.
What sizes and pressure ratings are available for butterfly valves?
The published size range is DN40 to DN2000, and the published pressure ratings are PN10 to PN63, ANSI Class 150 to Class 1500. Availability of a specific size and rating is confirmed at quotation.
What materials are butterfly valves available in?
The published specification lists body materials: WCB (ASTM A216), CF8, CF8M (ASTM A351), F316L (ASTM A182), F51/2205 duplex (ASTM A182), F53, F55/2507 super duplex (ASTM A182), C95400, C95800 aluminium bronze (ASTM B148). Material availability for a specific size and rating is confirmed at quotation.
What end connections do butterfly valves support?
The published specification lists Wafer, Lug, Flanged as the available end connections. The connection for a specific size is confirmed at quotation.
What should a quotation inquiry for butterfly valves include?
The governing standard and class, nominal size, body and seat materials, the service medium with temperature, and the destination — anything missing is confirmed during quotation.
Knowledge: selection guides
Types in this family
Type
Wafer Butterfly Valves
Wafer butterfly valves sandwich between the line flanges, giving pipeline isolation with the shortest face-to-face and lowest weight per diameter of the common
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Lug Butterfly Valves
Lug butterfly valves carry threaded lugs around the body so the disc can isolate one side of the line while the other stays flanged off — the dead-end service a
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Double Flanged Butterfly Valves
Double flanged butterfly valves bolt to the pipe on both faces with their own integral flanges, so they suit buried, water-works and pump-station lines where a
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Double Offset Butterfly Valves
Double offset butterfly valves move the shaft off both the centreline and the plane of the seat, so the disc lifts clear of the seat almost immediately on openi
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Triple Offset Butterfly Valves
Triple offset butterfly valves add a third, conical geometry to the double-offset disc so the seat touches only at the final degrees of closure — metal-to-metal
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Concentric Butterfly Valves
Concentric butterfly valves keep the stem centered in the disc and the disc centered in the bore, so the rubber-seated disc bears evenly all round — the economi
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Jacketed Butterfly Valves
Jacketed butterfly valves keep media that solidifies, crystallises or thickens at ambient temperature in a flowable state: the body carries a full heating jacke
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