Monel 400 Safety Relief Valves

Premier Hydrofluoric Acid (HF) Resistance: Standard material for HF alkylation unit safety relief valves, handling HF across all concentrations up to 150°C (302°F) with reliable set pressure accuracy.

Exceptional Seawater and Brine Resistance: Outstanding resistance to corrosion and biofouling in high-velocity seawater and brine service for marine boiler safety valves and heat exchanger thermal relief.

Excellent Chloride SCC Resistance: High nickel content (≥63%) provides outstanding resistance to chloride-induced SCC, outperforming all austenitic stainless steel grades in marine environments.

ASME Section VIII Certified: Certified for overpressure protection in pressure vessels and unfired steam boilers per ASME Section VIII, Div. 1.

ASME Section I Certified (upon request): For fired steam boiler service (power boilers) with ASME Section I stamp.

Precise Set Pressure Accuracy: Set pressure tolerance ±3% for spring-loaded designs, ±2% for pilot-operated designs.

Bubble-Tight Seat Leakage: API 527 seat tightness – zero detectable leakage for gas service.

Multiple Blowdown Options: Standard 7% blowdown, adjustable 5-15%, or custom blowdown for specific applications.

Balanced Bellows Design: Backpressure compensation for variable superimposed backpressure applications.

Full Range of Types: Spring-loaded conventional, balanced bellows, pilot-operated, thermal relief, and vacuum relief.

Size Range: Inlet sizes from 1/2″ to 12″ (DN15 to DN300) with orifice areas from D to T (0.110 to 26.0 sq in).

Pressure Ratings: Set pressures from 5 psig to 5000 psig (0.35 barg to 345 barg) depending on orifice and spring selection.

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

End Connections: Flanged (ASME B16.5), threaded (NPT), socket weld, and butt weld (BW).

Inlet/Outlet Configurations: Standard: inlet vertical, outlet horizontal; custom orientations available.

International Certifications: Valves can be certified by ASME, NBBI (National Board), ABS, BV, DNV, LR, and comply with API 520, API 526, API 527, ASME Section I, ASME Section VIII, and NACE MR0175.

Note: Capacities vary with set pressure and temperature. Consult Womic Steel engineering for specific sizing.

Critical Note: For sour service applications, spring material MUST be Inconel 718 or Elgiloy. Standard 17-7PH springs are NOT NACE compliant. Balanced bellows design is recommended for variable backpressure. Pilot-operated valves provide the best performance for high backpressure sour gas service.

Raw Material Selection: High-quality Monel 400 (UNS N04400) from certified premium mills (Special Metals, VDM Metals) with certified chemical composition (Ni ≥63%, Cu 28-34% verification) and traceability.

Forging/Casting: Valve body (nozzle) and bonnet forged or cast with strict temperature control.

Heat Treatment – Annealing: Annealing at 700–800°C followed by air cooling to relieve stresses.

Machining: Precision CNC machining of nozzle seat, disc guide, spring chamber, and flange faces.

Trim Machining: Seat ring, disc, and stem/spindle machined to exact tolerances for bubble-tight shut-off.

Spring Winding: Precision wound spring from Inconel 718 (for sour service) or 17-7PH (standard) wire, stress relieved, and set.

Lapping: Seat and disc faces lapped to achieve mirror finish (Ra ≤ 8 μinch) for zero leakage.

Assembly: Nozzle, disc, spring, bonnet, adjusting ring, blowdown ring, and cap assembled.

Calibration: Set pressure calibrated on ASME certified test bench with traceable pressure gauges.

Testing: Hydrostatic shell test, seat leakage test (air, bubble-tight), set pressure verification, blowdown verification.

Marking: Laser engraved with ASME/NB stamp, set pressure, capacity, orifice size, material, heat number, and serial number.

Set Pressure Testing: Calibrated at specified set pressure with tolerance ±3% (spring-loaded) or ±2% (pilot-operated), documented on test report.

Blowdown Verification: Blowdown verified to 7% standard (or per customer specification), documented.

Seat Leakage Testing: API 527 bubble test – zero detectable leakage for gas service, documented.

Hydrostatic Shell Test: 1.5× set pressure (minimum 1.5× MAWP), documented.

Backpressure Test (Balanced/Pilot): Verified at 50% backpressure for balanced bellows, documented.

Material Verification: PMI 100% for body, nozzle, disc, spring – verification of Ni, Cu.

Dimensional Inspection: Inlet/outlet dimensions, face-to-face, orifice size.

ASME Certification: ASME/NB stamp applied; National Board registration number provided.

NACE Compliance: Full documentation for sour service applications with spring material verification.

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

HF Alkylation Units (Refineries): HF acid reactor overpressure protection, acid storage tank relief, regenerator vessel safety valves, alkylate settler relief (NACE MR0175 limited, Monel 400 preferred).

Marine Steam Boilers: Main steam drum safety valves (ASME Section I upon request), superheater outlet relief, auxiliary boiler relief (ABS/BV/DNV/LR certified).

Chemical Tankers (Marine): Cargo tank pressure/vacuum relief valves (PV valves), chemical cargo vapor line relief, tank overfill protection (classification society certified).

Seawater Heat Exchangers (Thermal Relief): Thermal expansion protection for seawater-cooled heat exchangers, shell and tube exchanger relief, plate and frame exchanger thermal relief.

Chemical Processing (HF Service): Hydrofluoric acid storage tank relief, HF reactor overpressure protection, alkylation unit safety valves.

Pressure Vessels (ASME Section VIII): Unfired pressure vessel overpressure protection, process vessel relief, receiver tank safety valves (UV stamp).

Piping Systems: Dead-end line thermal relief, pressure regulator downstream protection, pump discharge overpressure protection.

Desalination Plants: Brine heater thermal relief, high-pressure reverse osmosis overpressure protection.

Shipbuilding: Marine boiler safety valves, cargo tank PV valves, ballast system thermal relief (ABS, DNV, LR, BV certified).

Oil and Gas (Limited Sour Service): Wellhead overpressure protection, flow line relief (with Inconel 718 springs).

Critical Note: Safety relief valves are critical safety devices. Installation requirements: 1) No block valves between vessel and SRV; 2) Discharge piping must be adequately sized and supported; 3) Discharge piping must drain away from operator area; 4) Valves must be tested periodically per jurisdictional requirements; 5) Never modify adjusting ring or spring without recertification.

Small valves (≤1-1/2″ inlet): Individual poly bags in carton boxes with calibration certificate and ASME data sheet.
Medium valves (2″–4″ inlet): Plywood cases with foam padding, each valve separated, flange protectors (if flanged), test report included.
Large valves (≥6″ inlet): Wooden crates with protective wrapping, inlet/outlet covers, lifting lugs, pallets, full documentation package.

All shipments:

Individual calibration report with set pressure and blowdown data

ASME data sheet (if ASME stamped)

Flange protectors for flanged ends

Plastic caps for threaded ends

Inlet/outlet covers for large valves

Individual tagging with set pressure, capacity, serial number

Complete documentation: MTR, PMI reports, hydrostatic test reports, set pressure test report, ASME/NB documentation, NACE compliance certificates (if required)

Womic Steel's Delivery Strengths:

ASME certified test bench with traceable pressure gauges

National Board registration numbers provided for ASME stamped valves

Professional loading by in-house teams using padded slings

Complete documentation package for regulatory compliance

Continuous cargo tracking and after-sales follow-up

1. What is the difference between safety valve, relief valve, and safety relief valve?
Safety valve – rapid opening, used for gas/steam (ASME Section I, VIII). Relief valve – gradual opening, used for liquid (thermal relief). Safety relief valve – can be used for both gas and liquid service. Monel 400 safety relief valves are suitable for both HF gas and liquid service.

2. Why choose Monel 400 over 316L for HF alkylation safety relief valves?
Monel 400 is the standard material for hydrofluoric acid service. 316L is NOT suitable for HF, especially at elevated temperatures. For HF alkylation unit safety valves, Monel 400 is mandatory.

3. What is blowdown?
Blowdown is the difference between set pressure and reseating pressure, expressed as percentage of set pressure. Standard blowdown is 7% for conventional safety relief valves. Monel 400 safety relief valves are calibrated and verified for blowdown.

4. Do Monel 400 safety relief valves come with ASME stamp?
Yes, safety relief valves are available with ASME Section VIII (UV stamp) for unfired pressure vessels and ASME Section I (V stamp) for fired steam boilers (upon request). National Board registration numbers provided.

5. Can Monel 400 safety relief valves be used in non-HF marine applications?
Yes, for marine boiler safety valves, seawater heat exchanger thermal relief, and cargo tank PV valves, Monel 400 provides excellent corrosion resistance. ABS, BV, DNV, LR certification available.

6. What spring material is required for sour service (H₂S) Safety Relief Valves?
For NACE MR0175 compliance, spring material MUST be Inconel 718 or Elgiloy. Standard 17-7PH springs are NOT NACE compliant. Womic Steel supplies NACE compliant Monel 400 safety relief valves with Inconel 718 springs.

7. How often should safety relief valves be tested?
Per ASME, power boilers: annually; unfired pressure vessels: every 5 years (or per jurisdictional requirements). Womic Steel provides test reports and calibration data for each valve.

8. Can I order safety relief valves with special set pressure not listed?
Yes, any set pressure between 5 psig and 5000 psig can be factory set. Spring may be custom manufactured for non-standard set pressures.

ASME Section VIII Certified: UV stamp for unfired pressure vessels – National Board registered.

ASME Section I Available: V stamp for fired steam boilers (marine and industrial).

HF Alkylation Industry Standard: Premier material for hydrofluoric acid service safety relief valves.

Marine Certified: ABS, BV, DNV, LR approvals available for marine boiler and cargo tank safety valves.

Full Range of Orifices: D through T – complete API 526 orifice coverage.

NACE MR0175 Compliant: For sour service with Inconel 718 springs (full documentation).

100% Set Pressure Tested: Every valve calibrated and tested before shipment – certificate included.

Blowdown Verified: 7% blowdown (or custom) – documented on test report.

Bubble-Tight Seat: API 527 zero detectable leakage for gas service.

Multiple Trim Options: Standard Monel, Stellite hardfaced, PEEK soft seat, PTFE lined.

Balanced Bellows Design: For variable backpressure applications – up to 50% backpressure capability.

Pilot-Operated Design: For high backpressure and low blowdown applications.

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

National Board Registration: Each ASME stamped valve is registered with National Board (NB number provided).

Global Delivery: Exported to major refineries, chemical plants, marine vessels, and boiler facilities worldwide.

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

E-mail: info@womicstainless.com

Website: www.womicsteel.com

Contact Womic Steel today for a competitive quote on Monel 400 safety relief valves. We offer ASME Section VIII certified valves, HF alkylation expertise, marine classification society approvals, NACE MR0175 compliance, precise set pressure calibration, fast production lead times, and reliable global delivery for your refineries, marine boilers, and chemical processing projects.

Stock Examples (Flanged Monel 400 Safety Relief Valves – Conventional Spring-Loaded – ASME Section VIII – HF Service):

Stock Examples (Flanged Monel 400 Safety Relief Valves – Balanced Bellows – Variable Backpressure):

Stock Examples (Threaded Monel 400 Thermal Relief Valves – Heat Exchanger Protection):

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