Duplex Steel Flanges

Duplex Steel Flanges Manufacturer, Supplier and Exporter in India

Solitaire Overseas is a reputable manufacturer, supplier and exporter of superior quality Duplex Steel Flanges in India. Our duplex flanges are designed to provide excellent performance in high-pressure and highly corrosive applications, and therefore they are popular in oil and gas, petrochemical, marine, pharmaceutical, and power generation industries.

Our Duplex Steel Flanges are made of high grade duplex stainless steel, a ferritin and austenitic microstructure to achieve high levels of strength, high pitting resistance and high resistance to stress corrosion cracking. Duplex steel flanges have almost twice the yield strength compared to conventional austenitic grades, which allows lighter and more cost-effective piping system designs.

Solitaire Overseas, as a manufacturer of duplex flanges in India, has adhered to the international quality standards such as ASME, ASTM, ANSI, DIN, EN and JIS. All our flanges are subjected to stringent quality tests before delivery and this means that our customers will get products that can match or even surpass those of the world.

Why Choose Solitaire Overseas for Duplex Steel Flanges?

• ISO-certified manufacturer with over two decades of industry experience
• Wide range of duplex flange types, grades and sizes available ex-stock
• Compliance with ASTM A182, ASME SA182, ANSI B16.5, B16.47 and other global standards
• Competitive pricing with fast delivery across India and international markets
• Complete material test certificates and third-party inspection reports available
• Custom sizes and special configurations available as per client drawings
• Exports to over 50 countries including the UAE, USA, UK, Saudi Arabia, Canada and Australia

Table of Contents

• What Are Duplex Steel Flanges?
• Duplex Steel Flanges Specifications
• Chemical Composition of Duplex Steel Flanges
• Duplex Steel Flange Equivalent Material Grades
• Types of Duplex Steel Flanges
• Manufacturing Standards for Duplex Steel Flanges
• Key Features and Properties of Duplex Steel Flanges
• Applications and Industries Served
• Testing and Quality Assurance
• Ordering and Commercial Information
• Related Products
• Frequently Asked Questions

What Are Duplex Steel Flanges?

Duplex Steel Flanges are mechanical components used to connect pipes, valves, pumps and other equipment in a piping system. They form a flanged joint when two flanges are bolted together, with a gasket placed between them to create a leak-proof seal. The term "duplex" refers to the dual-phase microstructure of the material, which consists of roughly equal proportions of austenite and ferrite.

This unique metallurgical composition gives duplex flanges a combination of properties not found in either purely austenitic or purely ferritic stainless steel, including high tensile strength, excellent resistance to chloride stress corrosion cracking, good weldability and reduced susceptibility to intergranular corrosion.

Duplex Steel Flanges are widely used when piping joints require periodic disassembly for maintenance or inspection. They are particularly suitable for applications involving seawater, acidic media, chloride environments and high-pressure process fluids.

Duplex Steel Flanges Specifications

Chemical Composition of Duplex Steel Flanges (Grade UNS S31803 / F51)

Duplex Flanges Equivalent Material Grades

Types of Duplex Steel Flanges We Manufacture

We manufacture and supply all standard and custom types of Duplex Steel Flanges. Below is a comprehensive list of the duplex flange types available from Solitaire Overseas:

1. Duplex Steel Weld Neck Flanges (WNRF)

Weld neck flanges feature a long tapered hub that is butt-welded to the pipe. The tapered hub provides an excellent stress distribution transition between the flange and the pipe, making this the preferred type for high-pressure, high-temperature and cyclic loading applications. Duplex Weld Neck Flanges are widely used in refineries, subsea pipelines and critical process systems.

2. Duplex Steel Slip-On Flanges (SORF)

Slip-on flanges slide over the pipe and are welded on both the inside and outside. They are easier to align during installation and are more economical than weld neck flanges. Duplex Slip-On Flanges are suitable for low-pressure and low-temperature applications where cost and ease of installation are priorities.

3. Duplex Steel Blind Flanges (BLRF)

Blind flanges are solid discs used to close the ends of pipes, valves or pressure vessel openings. They allow access to the piping system for inspection or cleaning while maintaining the integrity of the pressure boundary. Duplex Blind Flanges are frequently used in chemical processing and offshore oil platforms.

4. Duplex Steel Socket Weld Flanges (SWRF)

Socket weld flanges have a socket into which the pipe is inserted and then fillet welded. They are used primarily for smaller pipe sizes in high-pressure service. The socket weld design eliminates the need for precise pipe-end preparation and provides a stronger joint than threaded connections.

5. Duplex Steel Threaded Flanges

Threaded flanges feature internal threads that match the pipe's external threads, allowing the flange to be screwed onto the pipe without welding. This makes them ideal for applications where welding is not possible or practical, such as explosive or flammable environments. Duplex Threaded Flanges are suitable for low-pressure, non-critical applications.

6. Duplex Steel Lap Joint Flanges (LJRF)

Lap joint flanges are used in conjunction with a stub end. The flange slides freely over the pipe, and the stub end is butt-welded to the pipe. The lap joint flange face rests against the stub end flange face. This design is particularly advantageous when frequent dismantling is required or where pipe alignment is difficult to maintain.

7. Duplex Steel Ring Type Joint Flanges (RTJF)

RTJ flanges feature a grooved face that accepts a metallic ring gasket, which is compressed between the mating flanges to form a high-integrity seal. They are used in high-pressure, high-temperature applications such as oil and gas wellheads, subsea applications and refineries where a reliable seal is critical.

8. Duplex Steel Orifice Flanges

Orifice flanges are used with orifice plates to measure the flow rate of liquids and gases in pipelines. They are manufactured to ASME B16.36 and come with tapped holes for differential pressure measuring instruments. Duplex Steel Orifice Flanges are used extensively in gas metering and fiscal measurement applications.

9. Duplex Steel Long Weld Neck Flanges

Long weld neck flanges have an extended hub that acts as a nozzle on pressure vessels and heat exchangers. The extended length provides additional reinforcement and reduces stress concentrations at the vessel wall. They are ideal for connecting equipment nozzles to process piping.

10. Duplex Steel Spectacle Blind Flanges

Spectacle blind flanges consist of two circular discs joined by a small section of metal, resembling a pair of spectacles. One disc is solid (blind) and the other is open (spacer ring). By rotating the spectacle blind, the operator can isolate or open a section of pipeline without disturbing adjacent components.

11. Duplex Steel Reducing Flanges

Reducing flanges are used to connect pipes of different diameters. They are a cost-effective alternative to using a standard flange with a reducer fitting. Duplex Steel Reducing Flanges are available in various reducing configurations.

12. Duplex Steel Plate Flanges

Plate flanges, also known as flat flanges, are cut from plate material rather than forged. They are generally used for lower-pressure applications. Duplex Plate Flanges are available per DIN, ANSI, BS and other international standards.

Manufacturing Standards for Duplex Steel Flanges

Key Features and Properties of Duplex Steel Flanges

• High yield strength, approximately twice that of standard austenitic grades (316L, 304L)
• Excellent resistance to pitting and crevice corrosion in chloride-containing environments
• Outstanding resistance to stress corrosion cracking (SCC) under chloride exposure
• Good resistance to erosion corrosion and corrosion fatigue
• Lower thermal expansion coefficient than austenitic steels, closer to carbon steel
• Good weldability with proper procedures and qualified welders
• Excellent toughness down to moderate sub-zero temperatures
• Lower cost than super austenitic or nickel alloy alternatives in many corrosive applications
• Available with NACE MR0103 and NACE MR0175 certification for sour service applications
• High dimensional accuracy and smooth surface finishes

Applications and Industries of Duplex Stainless Steel Flanges

Duplex Steel Flanges from Solitaire Overseas are used across a wide spectrum of demanding industries where corrosion resistance, strength and reliability are paramount:

Oil and Gas Industry

Duplex flanges are extensively used in offshore and onshore oil and gas platforms, subsea pipelines, wellheads, Christmas trees and gas processing plants. Their resistance to hydrogen sulfide (H2S) in sour service conditions and to chloride-induced stress corrosion cracking makes them an excellent choice for upstream and downstream applications.

Petrochemical and Chemical Processing

In chemical plants and refineries, process fluids frequently contain aggressive acids, chlorides and other corrosive media. Duplex Steel Flanges provide reliable sealing and connection integrity in reactors, heat exchangers, distillation columns and chemical transfer piping.

Marine and Seawater Applications

The high pitting resistance equivalent number (PREN) of duplex steel makes it one of the best materials for seawater service. Duplex flanges are used in desalination plants, shipbuilding, offshore structures, cooling water systems and aquaculture equipment.

Power Generation

Nuclear, thermal and renewable energy plants use duplex steel flanges in cooling water systems, flue gas desulfurization (FGD) units, steam generation and feedwater piping. Their strength and corrosion resistance help extend service life and reduce maintenance intervals.

Pharmaceutical and Food Processing

The hygienic properties and corrosion resistance of duplex stainless steel make it suitable for pharmaceutical processing, food and beverage production and medical gas pipeline systems, where product purity and cleanability are critical requirements.

Pulp, Paper and Fertilizer Industries

Pulp and paper production involves exposure to bleaching agents and acidic effluents that aggressively attack standard stainless steel. Duplex flanges provide the necessary corrosion protection in digesters, bleach plants and chemical recovery systems. Similarly, in fertilizer plants, duplex steel resists the corrosive effects of ammonia, urea solutions and process acids.

Water and Wastewater Treatment

Duplex Steel Flanges are used in municipal and industrial water treatment plants, sewage treatment facilities, and water transmission pipelines. Their long service life and resistance to biological corrosion make them a cost-effective solution for infrastructure projects.

Testing and Quality Assurance of Duplex Flanges

At Solitaire Overseas, every batch of Duplex Steel Flanges is subjected to a comprehensive set of tests and inspections to verify that the product meets the specified material, dimensional and performance requirements. Our quality assurance process includes:

• Positive Material Identification (PMI) testing to verify alloy chemistry
• Intergranular Corrosion (IGC) tests per ASTM A262
• Hydrostatic pressure testing to verify structural integrity
• Ultrasonic Testing (UT) for internal defect detection
• Radiographic (X-ray) inspection for weld integrity
• Magnetic Particle Inspection (MPI) for surface crack detection
• Dye Penetrant Testing (DPT) for surface flaw detection
• Mechanical tests including tensile, yield, hardness and impact testing
• Macroscopic examination (macro test) and flattening test
• Dimensional inspection per applicable standards
• Third-party inspection available upon client request (TUV, Bureau Veritas, Lloyd's, SGS, etc.)

Ordering and Commercial Information

Port of Dispatch: Mumbai or Kalamboli ports, Maharashtra, India

Packaging: Flanges are packaged with proper protection to prevent damage during transit. Packaging charges extra.

Certifications Available: EN 10204 3.1 and EN 10204 3.2 Material Test Certificates, NACE MR0103, NACE MR0175

Lead Time: Ex-stock for standard sizes; custom sizes as per production schedule

Minimum Order: As per inquiry and specifications

Related Products

• Duplex Steel Products
• Duplex Steel Pipes & Tubes
• Duplex Steel Fittings
• Super Duplex Steel Flanges

Frequently Asked Questions - Duplex Steel Flanges