Reducing Flange Manufacturer, Supplier & Exporter
A reducing flange has the outside diameter, bolt circle and drilling of a larger pipe size but a bore sized for a smaller pipe. Raaj Fittings manufactures and exports reducing flanges to ASME B16.5 in weld neck, slip on and threaded types, in stainless steel, duplex, nickel alloys, carbon steel and alloy steel.
A reducing flange changes the line size at a flanged joint without a separate reducer fitting. For example, a 6" × 4" Class 300 reducing flange bolts to a 6" flange but is welded to 4" pipe. This saves space, weight and one weld, which is useful where a smaller pipe connects to a larger nozzle, pump or valve.
Every reducing flange is supplied with EN 10204 3.1 mill test certificates, with 3.2 certification and third-party inspection on request.
We export reducing 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.
Reducing Flange Specifications
Flange sizes ½" to 24" NPS; bore reduced to any smaller standard pipe size
ASME Class 150, 300, 600, 900, 1500 and 2500
ASME B16.5 (flange dimensions and drilling); EN 1092-1 on request
Reducing weld neck, reducing slip on and reducing threaded flanges
Larger (flange) size × smaller (pipe) size, e.g. 6" × 4" Class 300 RF
Forged and CNC machined; weld neck types bored to the smaller pipe schedule
EN 10204 3.1 mill test certificate as standard; EN 10204 3.2 on request
Materials & Grades
We supply reducing flanges in the following materials and grades. All grades are supplied with EN 10204 3.1 / 3.2 Mill Test Certificates.
Stainless Steel Reducing 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 Reducing 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 Reducing 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 Reducing 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 Reducing 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
When to Use a Reducing Flange
A reducing flange replaces two components — a standard flange and a concentric reducer — with one. The flange end is the larger size and bolts to its mating flange; the hub or bore is the smaller size and connects to the pipe.
- Compact — shortens the assembly where space is limited, such as at pump and equipment nozzles.
- Fewer welds — one less butt weld and one less fitting to buy, fit and inspect.
- Three types — weld neck for process service, slip on and threaded for lower pressures.
Reducing Weld Neck, Slip On and Threaded
A reducing weld neck flange has a hub sized for the smaller pipe and is bored to its schedule, making it suitable for higher pressures. Reducing slip on and threaded flanges have the smaller bore cut straight through the larger flange and are used on low-pressure and utility lines.
Limitations
The change in bore at a reducing flange is abrupt, so it creates more turbulence and pressure loss than a tapered reducer. Where flow conditions matter — at pump suctions, in high-velocity lines or where solids are present — a reducer is preferred. To increase the size at a flanged joint instead, use an expander flange.
Applications & Industries
- Connections between smaller piping and larger equipment nozzles
- Pump discharge and valve connections in process plants
- Skid packages and compact piping layouts
- Utility air, water and inert gas systems
- Refinery, petrochemical, chemical and power plants
Reducing flanges are a common choice in compact skid packages and at rotating equipment, where every metre of piping counts and fewer joints mean fewer potential leak paths. See all flange types we manufacture.
Testing, Inspection, Marking & Packing
Reducing 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 outside diameter, bolt circle, bore, hub and facing
- Marking with both sizes (e.g. 6 × 4), 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 Reducing 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 — Reducing 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.
Reducing Flanges — FAQs
A reducing flange has the outside diameter and drilling of a larger flange size but a bore for a smaller pipe. It changes the line size at a flanged joint without a separate reducer.
Give the larger (flange) size first and the smaller (pipe) size second, followed by type, class, facing, schedule and material — for example 6" × 4" weld neck, Class 300 RF, SCH 40, ASTM A105.
We supply reducing weld neck, reducing slip on and reducing threaded flanges. The weld neck type is used for process and higher-pressure service.
A reducing flange is shorter and needs fewer welds, but the sudden bore change causes more turbulence. Where smooth flow is important, a concentric or eccentric reducer is preferred.
An expander flange, which increases the bore from a smaller pipe to a larger flange size using a tapered hub.
Yes. We supply reducing 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.
