Description
Nickel-iron-chromium alloy industrial valve
Alloy 20 Triple Offset Butterfly Valve
A chemical-process valve material associated with sulfuric-acid, pickling and fertilizer duties. The triple offset butterfly valve configuration is engineered for compact high-temperature or severe-service process isolation.
What is a Alloy 20 Triple Offset Butterfly Valve?
A Alloy 20 Triple Offset Butterfly Valve combines a nickel-iron-chromium alloy containing copper and molybdenum, developed for resistance in sulfuric-acid and related chemical environments with a quarter-turn metal-seated design using three geometric offsets to reduce seat rubbing and support severe-service isolation.
Alloy 20 selection must use concentration-temperature corrosion data and account for contaminants, aeration, velocity and crevices. Seat-stack design, pressure direction, leakage class, shaft loading, thermal cycling and actuator torque are configuration-specific.
Alloy 20 Triple Offset Butterfly Valve specifications
| Product | Alloy 20 Triple Offset Butterfly Valve |
|---|---|
| Valve construction | Triple-eccentric metal-seated butterfly valve in wafer, lug, double-flanged or butt-weld body pattern |
| Nominal material | Alloy 20 |
| UNS / EN reference | UNS N08020; EN 2.4660 |
| Product forms | Wrought/forged ASTM B462 or ASTM A182 F20 as applicable; cast ASTM A351 CN7M; component specification controlled by design |
| Design standards | API 609 and ASME B16.34; EN 593 option for applicable European projects |
| Pressure testing | API 598, EN 12266-1 or project-specified shell and seat testing |
| Pressure rating | ASME Class or PN rating verified against exact material, size, construction and design temperature |
| End connections | Wafer, lug, double-flanged or butt-weld body patterns according to design |
| Operation | Gearbox, pneumatic, electric or hydraulic actuator |
| Documentation | EN 10204 3.1 material records, pressure test report, GA drawing and project inspection records as ordered |
This is an engineered inquiry product, not a universal stock specification. Final availability depends on valve size, pressure class, material form, trim, seat system, operator, quantity and required code edition.
Alloy 20 material selection
| Selection point | Engineering guidance |
|---|---|
| Material profile | a nickel-iron-chromium alloy containing copper and molybdenum, developed for resistance in sulfuric-acid and related chemical environments |
| Why it is selected | Useful resistance to sulfuric acid and a range of chemical environments, with fabrication characteristics familiar to stainless-alloy shops. |
| Typical service | Sulfuric-acid processing, fertilizer, pickling, chemical transfer and pharmaceutical process systems. |
| Limitations to check | It is not a universal acid alloy. Hydrochloric acid, oxidizing contaminants and mixed acids can change performance significantly. |
| Specification route | Wrought/forged ASTM B462 or ASTM A182 F20 as applicable; cast ASTM A351 CN7M; component specification controlled by design |
| Verification | PMI for nickel, chromium, copper and molybdenum plus heat traceability and component-specific MTC review. |
Triple Offset Butterfly Valve design and standards
API 609
Common design basis for butterfly valves; category, body pattern, seat design and edition must be identified.
ASME B16.34
Pressure-temperature and general valve design requirements where applicable.
API 598 / EN 12266-1
Shell and seat testing selected for the applicable project and market.
API 607 / ISO 10497
Fire-safe qualification applies only to the exact seat, seal and valve configuration.
Seal ring, seat stack, pressure direction, shaft/packing system, bearing loads and actuator safety factor must be reviewed as a complete package.
Fire-safe, fugitive-emission, sour-service, oxygen, cryogenic, chlorine and PED requirements apply only when explicitly defined and supported for the exact offered configuration.
Typical applications
| Industry | Material service context | Valve selection focus |
|---|---|---|
| Sulfuric-acid processing | Transfer, dilution and process systems within verified concentration-temperature limits | Pressure direction, leakage class, metal-seat design, temperature, torque and fire-safe/emissions qualification |
| Fertilizer | Acid and chemical handling systems after compatibility review | Pressure direction, leakage class, metal-seat design, temperature, torque and fire-safe/emissions qualification |
| Pickling | Selected acid circulation and transfer duties | Pressure direction, leakage class, metal-seat design, temperature, torque and fire-safe/emissions qualification |
| Pharmaceutical and fine chemical | Corrosive reagent and batch-process systems | Pressure direction, leakage class, metal-seat design, temperature, torque and fire-safe/emissions qualification |
Application examples are not a corrosion or design approval. The end user must verify process chemistry, contaminants, pressure, temperature, velocity, cycling, emissions and regulatory requirements.
Quality, testing and traceability
Heat-number traceability and EN 10204 3.1 records matched to the ordered component specifications.
PMI for nickel, chromium, copper and molybdenum plus heat traceability and component-specific MTC review.
API 598, EN 12266-1 or project-specified shell and seat testing, with acceptance and leakage criteria stated on the order.
GA drawing, dimensions, marking, operation, pressure test and specified NDE/third-party records.
RFQ checklist
- Valve design standard and required edition
- Nominal size and ASME Class or PN rating
- Exact material specifications for pressure boundary, trim, seats, packing and bolting
- Body pattern, face-to-face, pressure direction, leakage class, seal-ring design and actuation
- End connection, facing and face-to-face requirement
- Fluid composition, concentration, contaminants and solids
- Design and operating pressure/temperature
- PMI, corrosion testing, NDE, witnessing and document requirements
Frequently asked questions
Why is Alloy 20 used in sulfuric-acid service?
Its nickel, chromium, molybdenum and copper balance can provide useful resistance across selected sulfuric-acid conditions. Exact concentration, temperature and contaminants remain decisive.
What cast grade is commonly associated with Alloy 20 valves?
ASTM A351 CN7M is a commonly specified cast grade associated with Alloy 20-type service. Forged components use their applicable wrought specification.
Can Alloy 20 replace Hastelloy C276?
Not as a blanket substitution. The alloys have different chemistry, strength and corrosion behavior. Selection must follow actual process corrosion data and the piping material specification.
What are the three offsets?
They separate the shaft from the seat and body centerlines and add a conical sealing geometry, allowing rapid seat disengagement during opening.
Is every triple offset butterfly valve bidirectional?
No. Some designs have a preferred pressure direction or different leakage capability by direction. Confirm the tested performance of the exact configuration.
Can Alloy 20 be used for every component in this triple offset butterfly valve?
Not automatically. Pressure-boundary, trim, stem or shaft, seating, packing, gasket and bolting materials have different mechanical and corrosion duties. The complete bill of materials must be engineered for the service.
Related Alloy 20 valve products
Need a broader comparison? View the general stainless steel and alloy butterfly valves guide or browse all Butterfly Valves.
Request a Alloy 20 Triple Offset Butterfly Valve quotation
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