Expander Flange Manufacturer, Supplier & Exporter
An expander flange is a weld neck flange whose long, conical hub increases the bore from a smaller pipe size at the weld end to a larger size at the flange face. Raaj Fittings manufactures and exports expander flanges with flange dimensions and drilling to ASME B16.5, in stainless steel, duplex, carbon steel, alloy steel and nickel alloys.
An expander flange does the job of a weld neck flange and a concentric reducer in one forging. It is typically used to connect a pipe to a larger valve, pump, compressor or other equipment nozzle, and saves the space, cost and inspection of a separate reducer and its butt weld.
All expander flanges are supplied with EN 10204 3.1 mill test certificates, with 3.2 certification and third-party inspection on request.
We export expander flanges to EPC contractors, refineries and stockists across the Middle East and GCC, Europe and the Americas, made to the ASME, EN or DIN standard your project specifies, with PED-compliant supply for European projects on request.
Expander Flange Specifications
Increases the bore by one or two pipe sizes, e.g. 2" × 3", 4" × 6", 8" × 10"; combinations to order
ASME Class 150, 300, 600 and higher classes to order
Outside diameter, bolt circle and drilling of the larger size to ASME B16.5
Long conical hub, bevelled at the small end for butt welding to ASME B16.25
Forged in one piece and CNC machined; bore matched to the pipe schedule
EN 10204 3.1 mill test certificate as standard; EN 10204 3.2 on request
Materials & Grades
We supply expander flanges in the following materials and grades. All grades are supplied with EN 10204 3.1 / 3.2 Mill Test Certificates.
Stainless Steel Expander Flanges
Stainless steel flanges offer excellent corrosion resistance and are essential in chemical, pharmaceutical, food processing, and marine environments.
(ASTM A182 F304 / F304L) General corrosion resistance
(ASTM A182 F316 / F316L) Superior resistance to chlorides, acids; marine & pharmaceutical service
(ASTM A182 F316H) High-temperature elevated creep strength
(ASTM A182 F321) Titanium-stabilized; suitable for sustained elevated temperatures
(ASTM A182 F347) Columbium-stabilized; used in heat exchangers and high-temperature piping
High alloy; exceptional resistance to strong acids
Duplex & Super Duplex Stainless Steel Expander Flanges
Duplex and super duplex grades offer approximately twice the yield strength of standard austenitic stainless steel, combined with excellent resistance to stress corrosion cracking and pitting — making them ideal for offshore, subsea, and chemical processing.
(UNS S31803 / S32205) Used in offshore platforms and chemical processing plants
(UNS S32750) Ideal for seawater handling and desalination systems
(UNS S32760) Designed for high-chloride offshore service applications
Nickel Alloy Expander Flanges
For the most aggressive corrosive environments — including concentrated acids, caustic solutions, sour gas service, and extreme temperatures — we offer flanges in a full range of nickel alloys.
(UNS N06600) High-temperature oxidation resistance
(UNS N06625) Outstanding corrosion resistance for offshore and subsea service
(UNS N08825) Excellent resistance to phosphoric and sulfuric acids
(UNS N10276) Broad-spectrum corrosion resistance in acids and chlorides
(UNS N06022) Superior resistance to oxidizing acids
(UNS N04400) Suitable for seawater, hydrofluoric acid, and marine environments
(UNS N08020) Engineered for sulfuric acid service
Exceptional corrosion resistance with low weight
(C70600 / C71500) Preferred for marine and seawater piping systems
Carbon Steel Expander Flanges
Carbon steel is the standard choice for general-purpose, non-corrosive, and elevated-temperature services. The primary grade for forged carbon steel flanges is ASTM A105, and for low-temperature service, ASTM A350 LF2.
Primary grade for forged carbon steel fittings and flanges — covers ambient and elevated-temperature service in pressurised piping systems.
Low-temperature carbon steel, impact-tested for service down to -46°C (-50°F) — LNG, cold climate, and cryogenic piping applications.
Alloy Steel Expander Flanges
Alloy steel flanges are specified for high-temperature, high-pressure service in power generation, petrochemical, and refinery applications.
(5% Cr, ½% Mo) Designed for elevated temperature refinery service
(9% Cr, 1% Mo) Suitable for high-temperature steam and hydrogen service
(1¼% Cr, ½% Mo) Widely used in thermal power plant piping systems
(2¼% Cr, 1% Mo) Used in high-temperature pressure vessels and reactors
(9% Cr, 1% Mo, V, Nb) Engineered for ultra-high-temperature power plant steam lines
How an Expander Flange Works
The weld end of the hub matches the smaller pipe and is butt-welded to it. Along its length the hub opens out in a smooth cone until it reaches the larger bore at the flange face, which bolts to a standard flange of the larger size. The gradual taper gives a smoother transition than the sudden step of a reducing flange.
- Two parts in one — replaces a weld neck flange plus a concentric reducer.
- One less weld — saves fit-up, welding and radiography of the reducer joint.
- Shorter assembly — helpful where the space at an equipment nozzle is tight.
- Tapered transition — lower turbulence than an abrupt reduction.
Typical Uses
Valves, control valves and pumps are often a size larger or smaller than the pipe they serve. An expander flange lets the pipe connect directly to the larger flanged connection on the equipment. It is equally useful at the inlet of relief valves and on discharge lines that step up in size.
Ordering Information
State the pipe (small) size and the flange (large) size, the pressure class, facing, pipe schedule at the weld end and the material grade. Because expander flanges are not fully covered by a dimensional standard, we confirm the overall length and hub profile on our drawing before manufacture.
Applications & Industries
- Pump suction and discharge connections
- Control valve and relief valve installations
- Compressor and turbine piping
- Refinery, petrochemical and chemical process lines
- Power plant and water treatment piping
See all flange types we manufacture.
Testing, Inspection, Marking & Packing
Expander flanges are produced under our quality assurance process:
- Incoming material verification with PMI testing
- Chemical and mechanical testing to the applicable ASTM material specification
- Dimensional inspection of both bores, hub length, weld bevel, bolt circle and facing
- Marking with both sizes, class, grade and heat number
Supplied with EN 10204 3.1 mill test certificates; EN 10204 3.2 certificates and third-party inspection are available on request.
Flanges are packed for export with gasket faces protected by covers, rust-preventive coating on carbon and alloy steel, and seaworthy wooden cases; marking, tagging and packing to your specification are available on request.
Why Choose Raaj Fittings for Expander Flanges?
Raaj Sagar Steels has supplied piping components since 2003 and today manufactures flanges at two plants in India for buyers in the Middle East, Europe and the Americas.
- Manufactured in-house — Expander flanges are made in our own plants, so material, dimensions and delivery stay under our control.
- Ready stock, short lead times — common sizes and grades are held in stock for prompt dispatch; other sizes, grades and specials are manufactured to order.
- Certified quality — ISO 9001:2015, ISO 14001:2015 and ISO 45001:2018 certified; PED 2014/68/EU and IBR supply available, and NACE MR0175 / ISO 15156 material on request.
- 100% material verification — PMI testing on incoming material and EN 10204 3.1 mill test certificates with every order; 3.2 certificates on request.
- Third-party inspection ready — we regularly work with SGS, Bureau Veritas, TÜV and DNV.
- Export documentation — MTCs, certificates of origin, packing lists and inspection reports to suit projects in the GCC, Europe and the Americas.
- Export packing — seaworthy packing with end and face protection, and packing to your specification on request.
- Fast response — our team replies to enquiries within one business day.
Expander Flanges — FAQs
An expander flange is a weld neck flange with a long tapered hub that increases the bore from a smaller pipe size to a larger flange size. It combines a flange and a reducer in one forging.
A reducing flange has a larger flange with a small bore cut straight through it, giving an abrupt change in size. An expander flange widens the bore gradually along a conical hub, giving smoother flow.
Expander flanges normally increase the bore by one or two pipe sizes, such as 4" to 6". Other combinations can be made to order.
They are commonly used to connect pipe to larger pumps, valves, control valves and relief valves, saving a separate reducer and its weld.
The flange end follows ASME B16.5 dimensions and drilling. The hub length and profile are not fully standardised, so we confirm them on a drawing before manufacture.
Yes. We supply expander flanges for projects under the European Pressure Equipment Directive (PED 2014/68/EU), and with IBR certification for Indian boiler applications. NACE MR0175 / ISO 15156 compliant material is also available on request for sour service in the Middle East and the Americas.
