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Duplex & Super Duplex Flanges

Handling high chloride process lines or sour service often causes swelling or pitting in standard flanges. Our Duplex & Super Duplex flanges resist such failures with higher strength and superior crevice resistance. 

Standard Specification

ASTM A182 (F51/F53), NORSOK MDS D57, EN 10088-3 (1.4462/1.4501)

Pressure Rating

Class 150 to 2500 (PN10 to PN420) [Higher than austenitic at same thickness]

Material

F51 (UNS S31803), F53 (UNS S32750), F55 (UNS S32760) [PREN 35-45]

Nominal Size

½” to 48″ (DN15 to DN1200) [Limited by forging capabilities]

Flange Type

WN, SO, BL [No threaded types due to galling risk]
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Product Description

They retain shape and tightness even under cyclic thermal loads. This ensures long service life in offshore and aggressive chemical environments. 

Facing Type

RF, RTJ [Special groove finishes for sour service]

Dimensions

ASME B16.5 + 15% thickness reduction vs carbon steel [Per NACE MR0103]

Bolt Circle Diameter

Matches standard flanges [±0.04″ tolerance]

Number & Size of Bolt Holes

ASTM A320 L7M bolts [Anti-galling thread compounds]

Surface Finish

63-125 μin Ra (RTJ), 125-250 μin Ra (RF) [No shot peening]

Corrosion Resistance

PREN ≥35 (F51), ≥40 (F53) [Tested per ASTM G48 Method A]

Temperature Rating

-50°C to +300°C [275°C max for H₂S service]

Material Certification

EN 10204 3.2, NACE MR0175/MR0103, PED 2014/68/EU Annex I

Gasket Compatibility

Flexible Graphite, PTFE [Chloride-free]

Coating/Plating

Passivation only [No electroplating permitted]

Manufacturing Method

Forged + Solution Annealed (1025-1125°C WQ) [Ferrite 35-55% per ASTM A923]

Technical Advantages

We forge these flanges using F51, F53, or F55 grades with PREN from 35 to 45 for harsh fluid contact. The machined finish stays within RTJ or RF limits, using controlled surface roughness for better sealing. 

Each unit undergoes solution annealing and rapid quenching to meet A923 ferrite phase range. Our Duplex & Super Duplex Flanges faces are free of plating, galling, or cold work defects that shorten field life. 

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Industry Applications

Offshore Platforms

Resists seawater spray and H₂S gas exposure in topside and subsea lines. 

Chemical Process Plants

Handles acid or salt-rich flows without breakdown or stress corrosion cracking. 

Desalination Units

Works under warm brine and reverse osmosis pressure without flange face damage. 

FPSO Units

Maintains joint integrity through dynamic loads and multi-phase fluid transfer. 

Flue Gas Treatment Systems

Survives wet scrubbers and acidic condensates with no wall thinning. 

High-Pressure Vessels

Supports flange-to-shell joints in supercritical applications with stable ferrite balance. 

Duplex & Super Duplex Flanges

Built for High-Chloride and H₂S Service Without Shutdown Risks

Aggressive service media leads to sudden cracks or leaks in regular stainless steel joints. Our duplex & super duplex Flanges avoid this with higher yield strength and better localized corrosion resistance. 

They meet sour service specs under NACE MR0175 with temperature limits controlled for safe deployment. Purchasers use them to reduce field failure, limit replacement cost, and maintain line uptime. 

Having Doubts? Our FAQ

Check all our Frequently Asked Question

Can these flanges be used in seawater applications without coating?

Yes, F51 and F53 flanges offer pitting resistance equivalent to or better than coated carbon steel. PREN values above 35 ensure no coating is needed for seawater exposure. This reduces inspection frequency and eliminates coating maintenance.

Will duplex & super duplex flanges match our existing bolt pattern and gasket type?

Yes, the bolt circle and number match ASME B16.5 within ±0.04″ tolerance. Facing types include RF and RTJ, compatible with standard graphite or PTFE gaskets. This avoids site rework or alignment issues during line upgrades.

What makes these flanges suitable for sour gas service?

Material meets NACE MR0175 and MR0103, with no cold work or surface treatments that trigger sulfide stress cracking. Controlled ferrite content avoids phase imbalance during exposure. Sour compatibility testing is carried out per application standards.

Can these flanges be ordered in large sizes without delivery delays?

Yes, we supply up to 48-inch nominal sizes, depending on forging availability. Long-lead forgings are pre-blocked for F53 and F55 grades to reduce waiting time. Buyers can confirm lead time before locking the PO.

Do you provide flange marking and traceability as per global project specs?

Yes, each flanges comes with heat number, grade, size, and spec stamped per ASTM A182 requirements. We include full MTC with traceable forging route and solution annealing batch. This supports third-party audits and EPC project documentation.

Can Frigate support urgent project requirements with fast-track manufacturing?
  • Yes, Frigate maintains ready forging blocks for F51, F53, and F55 grades. 
  • Dedicated production slots are allocated for critical orders to reduce queue time. 
  • Expedited heat treatment and machining cycles are available on request. 
  • Typical lead time can be shortened based on size, grade, and quantity. 
How does Frigate ensure dimensional accuracy for EPC project fit-up?
  • CNC machining is performed with strict tolerance control per ASME B16.5. 
  • Each flange undergoes dimensional inspection before dispatch. 
  • Bolt hole alignment and face flatness are verified to prevent site mismatch. 
  • Inspection reports are shared to support pre-installation validation. 
Can Frigate customize flange specifications beyond standard ASTM requirements?
  • Yes, custom thickness, facing finish, and groove profiles can be manufactured. 
  • Project-specific standards like NORSOK, ADNOC, or Shell specs are supported. 
  • Additional testing or documentation can be included as per client requirements. 
  • Engineering team reviews drawings to ensure manufacturability before production. 
What quality checks does Frigate perform before dispatch?
  • Raw material is verified through PMI and chemical composition testing. 
  • Heat treatment records are validated for ferrite balance compliance. 
  • Corrosion resistance is tested as per ASTM G48 when required. 
  • Final inspection includes visual, dimensional, and surface finish checks. 
How does Frigate support procurement teams during project execution?
  • Dedicated coordination for order tracking and milestone updates. 
  • Complete documentation package including MTC, test reports, and compliance certificates. 
  • Assistance with technical queries during installation and commissioning. 
  • Reliable communication ensures no delays in project timelines. 
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LOCATIONS

Registered Office

10-A, First Floor, V.V Complex, Prakash Nagar, Thiruverumbur, Trichy-620013, Tamil Nadu, India.

Operations Office

9/1, Poonthottam Nagar, Ramanandha Nagar, Saravanampatti, Coimbatore-641035, Tamil Nadu, India. ㅤ

Other Locations

  • Bhilai
  • Chennai
  • India
  • Germany
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LOCATIONS

Registered Office

10-A, First Floor, V.V Complex, Prakash Nagar, Thiruverumbur, Trichy-620013, Tamil Nadu, India.

Other Locations

  • Bangalore
  • Chennai
  • India
  • Germany
Become a Frigatian
Become a Supplier

GENERAL ENQUIRIES

  • +91 96778 64606
  • manufacture@frigate.ai
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Duplex & Super Duplex Flanges

Need reliable wires and cables for your next project? Get in touch with us today, and we’ll help you find exactly what you need!

Get Latest Price

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Duplex & Super Duplex Flanges

Need reliable Machining for your next project? Get in touch with us today, and we’ll help you find exactly what you need!

Get Latest Price

Get Price Form