Alloy 825 Pressure Reducing Valves

Superior Corrosion Resistance: Nickel-chromium-molybdenum-copper alloy provides outstanding resistance to H₂SO₄, H₃PO₄, HCl, H₂S, and chloride SCC – premier material for corrosive service pressure reducing 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.

Precise Downstream Pressure Control: Maintains constant outlet pressure regardless of inlet pressure fluctuations, with accuracy up to ±2% of set point.

Self-Operated Design: No external power required – internal spring or dome pressure controls valve position.

Fail-Safe Operation: Spring-loaded design provides fail-open or fail-closed configuration for safety critical applications.

Multiple Control Types: Direct-operated (low flow), pilot-operated (high flow), dome-loaded (high accuracy), and pressure-reducing/back-pressure combinations.

Titanium Stabilization: Prevents sensitization and intergranular corrosion – no PWHT required for welded connections.

Wide Pressure Range: Inlet pressures up to 6000 psig, outlet pressures from 5 psig to 1500 psig.

Full Range of Sizes: 1/2″–12″ (DN15–DN300) with flanged, threaded, socket weld, and butt weld ends.

Pressure Ratings: Inlet Class 150-2500; outlet Class 150-600.

Temperature Range: Suitable for -46°C to 400°C (-50°F to 752°F) depending on trim materials.

International Certifications: Valves can be certified by ABS, BV, DNV, LR, and comply with ASME B16.34, NACE MR0175, and ISO 4126.

Raw Material Selection: High-quality Alloy 825 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.

Forging/Casting: Valve body and bonnet forged or cast with strict temperature control for high integrity.

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

Machining: Precision CNC machining of seat bore, stem bore, and spring chamber.

Trim Machining: Seat ring, disc (plug), and stem machined to exact specifications.

Spring Winding: Precision wound spring from Inconel 718 wire, stress relieved, and set.

Diaphragm/Piston Assembly: PTFE, Viton, or metal diaphragm/piston assembled.

Assembly: Body, trim, spring, diaphragm/piston, bonnet, and adjustment screw assembled.

Calibration: Pressure setting calibrated on test bench with pressure gauges.

Testing: Hydrostatic shell test, seat leakage test, set pressure verification lock-up test.

Marking: Laser engraved with size, pressure rating, set pressure, flow direction, material, heat number, and NACE/MR0175 markings.

Pressure Testing: Shell test (1.5× max inlet pressure), seat test (1.1× set pressure, zero leakage), lock-up test (no flow at set pressure).

Set Pressure Verification: Calibrated at specified set pressure with tolerance ±2% of set point.

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

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

Spring Testing: Spring rate verification, free length, solid height.

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

NACE Compliance: Full documentation for sour service applications.

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

Steam Systems (Chemical Plants): Boiler steam pressure reduction, process steam control, turbine bypass, heating system PRV.

Sour Gas Pipeline Pressure Reduction: Natural gas pressure letdown, wellhead gas regulation, pipeline pressure control (NACE MR0175 compliant).

Chemical Injection Systems: High pressure chemical injection skids, additive injection, catalyst feed.

Hydrogen Service: Hydrogen pipeline pressure reduction, fuel cell feed, refinery hydrogen handling.

Pharmaceutical Process Control: Sterile steam pressure reduction, clean gas regulation, WFI pressure control.

Instrument Air Systems: Plant air pressure reduction, control valve supply pressure regulation.

Laboratory and Pilot Plants: High pressure gas reduction, chemical feed control.

Water Treatment: Reverse osmosis feed pressure control, chemical dosing systems.

Oil and Gas (Sour Service): Wellhead pressure reduction, flow line pressure control (NACE MR0175).

Marine Systems: Shipboard steam pressure reduction, boiler feed water control (ABS/BV/DNV/LR certified).

Critical Note: Pressure reducing valves must be installed with proper orientation (flow direction arrow on body). A pressure relief valve (safety valve) is required downstream to protect against PRV failure. For dead-end shut-off services, a pressure relief valve is mandatory.

Small valves (≤2″): Individual poly bags in carton boxes with calibration certificate.
Medium valves (2.5″–6″): Plywood cases with foam padding, each valve separated, flange protectors.
Large valves (≥8″): Wooden crates with protective wrapping, flange protectors, lifting lugs, and pallets.

All shipments:

Individual calibration certificate included

Plastic end caps for threaded/socket weld ends

Flange protectors for flanged ends

Individual tagging: Size, set pressure, material, heat number

Complete documentation: MTR, PMI reports, ASTM G28 test reports, hydrostatic test reports, NACE compliance certificates, calibration reports

Womic Steel's Delivery Strengths:

Ready stock: 1/2″–6″ Alloy 825 pressure reducing valves for steam and gas service – dispatch within 48-72 hours.

Direct cooperation with global shipowners for competitive freight rates.

Professional loading by in-house teams.

Continuous cargo tracking and after-sales follow-up.

1. What is the difference between direct-operated and pilot-operated pressure reducing valves?
Direct-operated uses spring force directly on the disc – suitable for low flow, cost-effective. Pilot-operated uses a small pilot valve to control main valve – higher flow capacity, better accuracy (±1-2%). For large steam systems and gas pipelines, pilot-operated is recommended.

2. Why choose Alloy 825 over 316L for pressure reducing valves?
Alloy 825 offers superior resistance to sulfuric acid, phosphoric acid, HCl, and H₂S. For sour gas service (NACE MR0175) and chemical processes with aggressive media, Alloy 825 is required.

3. What is lock-up pressure?
Lock-up is the pressure at which the valve fully closes under no-flow condition. Standard lock-up is within 5-10% of set pressure. Alloy 825 pressure reducing valves are tested for lock-up on every unit.

4. Do I need a safety relief valve downstream?
Yes. A pressure relief valve (safety valve) is required downstream to protect against potential PRV failure or seat leakage. This is a code requirement (ASME B31.1, B31.3).

5. Can Alloy 825 pressure reducing valves be used in dead-end service?
Yes, but a downstream pressure relief valve is mandatory. The valve will hold dead-end pressure, but lock-up leakage must be zero for critical services.

6. What is the typical Cv range for Alloy 825 pressure reducing valves?
Cv varies by size: 1/2″ (Cv 0.5-2.0), 1″ (Cv 3.0-8.0), 2″ (Cv 10-25), 4″ (Cv 40-80), 6″ (Cv 100-150), 8″ (Cv 200-300).

Complete Pressure Range: 5 psig to 3000 psig outlet – all ranges available.

Multiple Control Types: Direct, pilot, dome, spring – all types available.

Strict Quality Control: ISO 9001, PED, NACE certified.

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

100% Calibrated: Every valve tested and calibrated with certificate.

Titanium Stabilized: ASTM G28 intergranular corrosion tested.

Fail-Safe Options: Spring-loaded fail-open or fail-closed.

Full Traceability: Heat number on body – traceable to raw material.

Flexible Customization: Special set pressures, end connections, materials.

Global Delivery: Exported to major chemical, gas, and pharmaceutical projects 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 pressure reducing valves. We offer certified quality, NACE MR0175 compliance, ASTM G28 corrosion testing, precise pressure control, fast production lead times, and reliable global delivery for your steam, gas, and corrosive service pressure control projects.

Stock Examples (Flanged Alloy 825 Pilot-Operated Pressure Reducing Valves – Steam Service):

Stock Examples (Threaded Alloy 825 Direct-Operated Pressure Reducing Valves – Chemical Injection):

Stock Examples (Flanged Alloy 825 Dome-Loaded Pressure Reducing Valves – High Pressure Gas – NACE MR0175):

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