Alloy 825 Butterfly Valves

Superior Sulfuric and Phosphoric Acid Resistance: Outstanding performance in H₂SO₄ (all concentrations up to moderate temperature), H₃PO₄, and mixed acids – premier material for acid service butterfly valves.

NACE MR0175 / ISO 15156 Compliant: Fully qualified for sour service (H₂S) up to 232°C (450°F), with documented HIC and SSC test reports available.

Excellent Chloride SCC Resistance: High nickel content (38-46%) provides outstanding resistance to chloride-induced SCC, outperforming all austenitic and duplex stainless steel grades.

Good Pitting and Crevice Corrosion Resistance: Molybdenum (2.5-3.5%) and chromium provide enhanced localized corrosion resistance.

Titanium Stabilization: Prevents sensitization and intergranular corrosion after welding – no PWHT required.

Multiple Offset Designs: Zero offset (concentric), double offset (high performance), and triple offset (metal seated) available.

Low Operating Torque: Disc and shaft design provides smooth quarter-turn operation with low torque requirements.

Bubble-Tight Shut-Off: Resilient seat (PTFE/PFA) provides zero leakage shut-off for critical acid service.

Multiple End Connections: Wafer, lug, flanged (ASME B16.5), and butt weld ends.

Full Range of Types: Concentric (1-1/2″–24″), double offset (3″–48″), triple offset (3″–48″), lug style, wafer style.

Pressure Ratings: Available in Class 150, 300, 600 (PN6 to PN100).

Temperature Range: Suitable for -196°C to 260°C (-321°F to 500°F) depending on seat material.

International Certifications: Valves can be certified by ABS, BV, DNV, LR, GL, RINA, CCS, KR, and NK, and comply with API 609, ASME B16.34, NACE MR0175, and ISO 17292 standards.

Critical Note: Alloy 825 butterfly valves are fully NACE MR0175 / ISO 15156 compliant for sour service applications. For offshore chemical injection and sour gas service, Alloy 825 is the preferred material over duplex and austenitic stainless steels.

Raw Material Selection: High-quality Alloy 825 (UNS N08825) from certified premium mills (Special Metals, VDM Metals, Carpenter) with certified chemical composition (Ni 38-46%, Cr 19.5-23.5%, Mo 2.5-3.5%, Cu 1.5-3.0%, Ti 0.6-1.2% verification) and traceability.

Casting/Forging: Valve body and disc cast or forged with strict temperature control.

Heat Treatment – Solution Annealing: Solution annealing at 925–1040°C followed by water quenching to restore corrosion resistance.

Machining: CNC lathes and machining centers produce precise dimensions – body bore, disc O.D., stem bores, flange faces, and bolt holes.

Disc Machining: Disc machined to precise dimensions for proper seating.

Seat/Liner Molding: PTFE/PFA liner molded into body or bonded to disc.

Stem Machining: Stem machined with keyways and bearing surfaces.

Assembly: Body, disc, stem, seat, bearings, and bolting assembled.

Testing: Hydrostatic shell test, seat test (bubble-tight), disc movement verification, torque test.

Marking: Laser engraved with size, pressure, material, heat number, API 609, and ratings.

Pressure Testing: 100% hydrostatic shell test (1.5× rated pressure), seat test (1.1× rated pressure, zero leakage for soft seat).

Material Verification: PMI 100% for body, disc, stem – verification of Ni, Cr, Mo, Cu, Ti.

Intergranular Corrosion Test: ASTM G28 – validates resistance to intergranular corrosion (mandatory for stabilized grades).

Dimensional Inspection: Face-to-face, flange dimensions, disc seating alignment.

Disc Rotation Verification: 90° rotation smooth, no binding.

Seat Integrity: Bubble-tight test at low pressure.

NACE Compliance: Full documentation for sour service applications.

Third-Party Inspection: SGS, BV, DNV, TUV, LR on customer request.

Sulfuric Acid Plants: Sulfuric acid transfer isolation, acid cooler butterfly valves, storage tank inlet/outlet, dilution system control (NACE MR0175 compliant for sour service where applicable).

Phosphoric Acid Service: Phosphoric acid evaporator isolation, heat exchanger butterfly valves, fertilizer production equipment, wet-process phosphoric acid plant valves.

Chemical Processing (Acid Service): Chemical reactor isolation, process vessel butterfly valves, chlorinated hydrocarbon handling, organic acid processing (acetic, formic, citric).

Offshore Chemical Injection: Methanol injection isolation, glycol service butterfly valves, chemical injection skid valves (ABS/BV/DNV/LR certified).

Pickling Plants: Acid recovery system isolation, spent acid handling butterfly valves, pickling line circulation valves.

Oil & Gas Sour Service: Amine service butterfly valves, sour water stripper isolation (NACE MR0175 compliant).

Pharmaceutical: High-purity process line butterfly valves, sterile transfer isolation, clean steam systems.

Marine Engineering (Chemical Tankers): Cargo piping butterfly valves, acid handling line isolation (classification society certified).

1. How does Alloy 825 compare to 316L for butterfly valves in acid service?
Alloy 825 offers significantly better resistance to sulfuric acid (H₂SO₄), phosphoric acid (H₃PO₄), and chloride stress corrosion cracking. For concentrated acid service where 316L would fail rapidly, Alloy 825 is required.

2. What is the difference between concentric, double offset, and triple offset butterfly valves?
Concentric (zero offset) – resilient seat, low pressure, general chemical service. Double offset – higher pressure, higher temperature, PTFE seat. Triple offset – metal seated, highest performance, high temperature, abrasive service.

3. Are Alloy 825 butterfly valves suitable for vacuum service?
Yes, with proper design. Lug and flanged styles provide better vacuum service capability. Consult Womic Steel for specific vacuum ratings.

4. Can Alloy 825 butterfly valves be used for control (throttling) service?
Yes, butterfly valves are excellent for throttling. Double offset and triple offset designs provide better flow characteristics for modulating control.

5. What seat material is best for sulfuric acid service?
PTFE is standard for H₂SO₄ service up to 180°C. PFA is recommended for higher temperature (up to 260°C). For abrasive sulfuric acid slurries, RTFE provides better wear resistance.

6. Do Alloy 825 butterfly valves require post-weld heat treatment for installation?
No, for wafer and lug style valves, no welding required. For flanged ends, PWHT is not typically required for Alloy 825.

Complete Product Range: Concentric, double offset, triple offset – all types available for acid service.

Strict Quality Control: API 609, ISO 9001, PED certified.

NACE MR0175 / ISO 15156 Compliant: Full sour service documentation.

Titanium Stabilized: ASTM G28 intergranular corrosion tested.

100% Pressure Tested: Hydrostatic shell and seat tests on every valve.

Full Traceability: Heat number on body – traceable to raw material.Flexible Customization: Special liners, gear operators, actuation, extended neck.

Global Delivery: Exported to major chemical plants and acid handling facilities worldwide.

Tel / WhatsApp:
Victor: +86 15575100681
Jack: +86 18390957568

Website: www.womicstainless.com

E‑mail: info@womicstainless.com

Contact Womic Steel today for a competitive quote on Alloy 825 butterfly valves. We offer certified quality, NACE MR0175 compliance, ASTM G28 corrosion testing, fast production lead times, and reliable global delivery for your acid service and chemical processing projects.

Stock Examples (Concentric Wafer Alloy 825 Butterfly Valves – Class 150 – PTFE Lined – Sulfuric Acid Service):

Stock Examples (Lug Style Alloy 825 Butterfly Valves – Class 150 – Double Offset – Higher Pressure):

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