The Fergo double eccentric butterfly valve combines high tightness, minimal wear and maximum operational safety under extreme conditions. Available from DN50 to DN600, PN10/16 and ANSI Class 150, in wafer (AX130) or lug (AX131) design. Body in ASTM A216 WCB (carbon steel) or ASTM A351 CF8M (stainless steel). Two seat materials: RPTFE (PTFE+25 % GF) up to +220 °C or INCONEL 718 (metallic) up to +360 °C. Certified ATEX II 2GDc to 2014/34/EU and TA-Luft to ISO 15848-1. Tightness to Class VI / ISO 5208, leak rate A (RPTFE) / AA (INCONEL). 28 variants in stock.
In a double eccentric butterfly valve — also called a double offset butterfly valve — the shaft axis is off...
The Fergo double eccentric butterfly valve combines high tightness, minimal wear and maximum operational safety under extreme conditions. Available from DN50 to DN600, PN10/16 and ANSI Class 150, in wafer (AX130) or lug (AX131) design. Body in ASTM A216 WCB (carbon steel) or ASTM A351 CF8M (stainless steel). Two seat materials: RPTFE (PTFE+25 % GF) up to +220 °C or INCONEL 718 (metallic) up to +360 °C. Certified ATEX II 2GDc to 2014/34/EU and TA-Luft to ISO 15848-1. Tightness to Class VI / ISO 5208, leak rate A (RPTFE) / AA (INCONEL). 28 variants in stock.
In a double eccentric butterfly valve — also called a double offset butterfly valve — the shaft axis is offset from the seat plane in two directions. The disc lifts immediately off the seat ring on opening, eliminating sliding friction. This reduces seat wear and extends service life significantly — especially on frequently operated valves in chemical, steam and oil/gas service. Full product details for both series are on AX130 wafer and AX131 lug. Use the product configurator above to select size, body, seat and actuation.
What is a double eccentric butterfly valve?
A double eccentric butterfly valve offsets the shaft axis in two planes from the seat centreline — axially (behind the seat plane) and radially (out of the pipe centre). On opening the disc swings clear of the seat instantly, without rubbing. On closing the disc contacts the seat ring only at the last moment and presses in evenly. Compared to a concentric butterfly valve, the double offset design delivers higher tightness, lower wear and longer service life. The construction follows DIN EN 593 for metallic butterfly valves.
Concentric vs. double eccentric — key differences
| Feature | Concentric butterfly valve | Double eccentric butterfly valve |
|---|---|---|
| Shaft axis | centred in pipe | double offset (axial + radial) |
| Seat wear | higher (disc rubs on seat) | minimal (disc lifts immediately) |
| Tightness | Class IV–V | Class VI / ISO 5208, leak rate A/AA |
| Seat | EPDM, NBR, FKM | RPTFE or INCONEL 718 |
| Temperature | up to +180 °C | up to +360 °C (INCONEL) |
| ATEX / TA-Luft | no (standard) | yes (ATEX II 2GDc, ISO 15848) |
| Typical use | water, HVAC, general industry | chemicals, steam, oil/gas, Ex zones |
RPTFE vs. INCONEL 718 — which seat?
| Feature | RPTFE (PTFE+25 % GF) | INCONEL 718 |
|---|---|---|
| Seal type | soft-seated | metal-seated |
| Temperature | −29 °C to +220 °C | −29 °C to +360 °C |
| Leak rate | A (Class VI) | AA (Class VI) |
| Packing | PTFE | graphite |
| Typical media | chemicals, solvents, gases | steam, hot gases, thermal oil |
Above 225 °C we recommend fitting a heat dissipator on the INCONEL version. Check material compatibility with our resistance check tool.
ATEX butterfly valve & TA-Luft — certifications
The double eccentric butterfly valve is certified as an ATEX butterfly valve to Directive 2014/34/EU (ATEX II 2GDc). It is approved for use in hazardous areas Zone 1 (gas) and Zone 21 (dust). It also meets TA-Luft requirements for stem sealing to EN ISO 15848-1. All approvals are on the Certificates page.
Technical data — AX130 (wafer) and AX131 (lug)
- Nominal size: DN50 to DN600
- Connection: wafer (AX130) or lug (AX131), PN10/16, ANSI Class 150
- Face-to-face: EN 558-1 Series 20 / ISO 5752 Series 20
- Body: ASTM A216 WCB or ASTM A351 CF8M
- Disc: ASTM A351 CF8M
- Shaft: ASTM A276 F316
- Seat: RPTFE (PTFE+25 % GF) or INCONEL 718
- Packing: PTFE (RPTFE) or graphite (INCONEL)
- Top flange: ISO 5211
- Tightness: Class VI / ISO 5208, leak rate A (RPTFE) / AA (INCONEL)
- Pressure: max. 25 bar
- Temperature: −29 °C to +220 °C (RPTFE) / −29 °C to +360 °C (INCONEL)
- Actuation: hand lever (SS316), gearbox, pneumatic or electric actuator
- Certifications: TA-Luft (ISO 15848-1), ATEX II 2GDc (2014/34/EU)
- Conformity:EU Pressure Equipment Directive 2014/68/EU
Applications — chemicals, steam, oil/gas and water
The double eccentric butterfly valve suits high-performance applications across process industries. In chemical and petrochemical plants, ATEX-certified valves with INCONEL seat and graphite packing secure aggressive chemicals and process gases in Ex zones up to +360 °C. In power plants and steam systems, metal-seated valves isolate hot water and steam circuits. In water and wastewater treatment, WCB valves with RPTFE seat and TA-Luft approval deliver the required emission protection. In oil and gas including offshore, the ATEX certification ensures safe operation in hazardous areas.
Double eccentric butterfly valve in stock — EU-wide delivery
Fergo stocks all 28 double eccentric butterfly valve variants — delivery typically in 1–2 weeks across Europe. Each valve ships with datasheet, 3D model and declaration of conformity. For pneumatic or electric automation Fergo assembles the complete actuator package.
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