Amigo Impex is a duplex steel flanges manufacturer, stockist, supplier and exporter based in Mumbai, India, supplying since 2013. Forged flanges are manufactured to ASTM A182 / ASME SA-182, with F51 and F60 covering duplex 2205 and F68 covering lean duplex 2304 (UNS S32304). Cutting, machining, threading, fabrication, testing and packing are handled in-house.
Duplex stainless steel flanges are used to create bolted, gasketed connections between pipes, valves and equipment. Their dual-phase ferritic-austenitic structure combines high strength with good resistance to chloride-induced corrosion. The chromium, molybdenum and nitrogen content helps duplex stainless steel resist pitting, crevice corrosion and chloride stress corrosion cracking in seawater, brine and other demanding environments.
The standard size range covers 1/2" to 24" NB under ASME B16.5 and 26" to 60" under ASME B16.47. Pressure classes run from Class 150 to Class 1500 across the full 1/2" to 24" range, with Class 2500 available from 1/2" to 12" only. Eleven flange types and five facing options are available on order.
Around 60 to 70 tonnes of duplex steel stock is held in Mumbai for domestic and export requirements. A mill test certificate accompanies every order, with third-party inspection and EN 10204 3.2 certification available when specified. Supply covers pan-India, while export orders are shipped to the USA, the Gulf, Europe and Asia.
The following table summarises the principal specifications, grades, dimensions, pressure classes, flange types, facings and certification available for duplex steel flanges.
Material requirements and flange dimensions are covered by separate standards. ASTM A182 / ASME SA-182 governs the forged material, while ASME and other dimensional standards define the flange geometry, drilling and pressure classes.
| Standard | Scope |
|---|---|
| ASTM A182 / ASME SA-182 | Forged duplex flanges, including F51 and F60 |
| ASME B16.5 | Flange dimensions from 1/2" to 24" NB |
| ASTM B16.36 | Orifice flanges, Class 300 to 2500 |
| ASME B16.47 Series A & B | Large-diameter flanges from 26" to 60" |
| ASME B16.48 | Line blanks: spectacle blinds, paddle blanks and spacers, Class 150 to 2500 |
| EN 1092-1 | European flange dimensions and PN designations |
| DIN / BS 4504 / JIS B2220 | Export dimensional requirements |
| IS 6392 | Indian Standard flange dimensions |
| NACE MR0175 / ISO 15156 | Sour-service requirements where applicable |
The supplied range includes duplex 2205 and lean duplex 2304. Grade selection depends on the required corrosion resistance, strength and service conditions.
Duplex 2205 is supplied under the S31803 and S32205 designations and corresponds to ASTM A182 F51 and F60. Dual-certified material can satisfy specifications calling for either designation. S32205 has tighter composition requirements than the original S31803 grade.
Lean duplex S32304, commonly known as 2304, contains less nickel and molybdenum than duplex 2205. It is suitable for applications requiring good corrosion resistance and strength under moderate chloride conditions.
Duplex flanges are supplied across the standard ASME size ranges, with larger diameters manufactured against order and drawing requirements.
| Parameter | Range |
|---|---|
| Standard Range (ASME B16.5) | 1/2" to 24" NB |
| Large Diameter (ASME B16.47 Series A & B) | 26" to 60" |
| Frequent Enquiry Band | Up to 48" NB |
| Bore Preparation | Matched to the mating pipe schedule |
| Non-Standard Work | Made-to-drawing sizes and drilling |
Pressure class for duplex flanges is selected according to the piping design, operating conditions and applicable dimensional standard. The available ASME pressure classes vary between B16.5 and B16.47.
| Dimensional Standard | Pressure Classes |
|---|---|
| ASME B16.5 (1/2"–24") | Class 150, 300, 400, 600, 900, 1500 |
| ASME B16.5 (1/2"–12" only) | Class 2500 |
| ASME B16.47 Series A | Class 150 to 900 |
| ASME B16.47 Series B | Class 75 to 900 |
Eleven flange patterns are available for different piping connections, terminations, isolation and flow-measurement requirements.
The required facing is selected according to the gasket, mating flange and service conditions. The following five facing options are available:
Machined gasket faces are individually protected before packing. Flanges are then placed in timber cases, crates or strapped pallets according to the shipment size. Each piece is marked with the grade, heat number, size, class and specification.
Domestic orders are dispatched across pan-India, while export consignments are shipped from Mumbai to the USA, the Gulf, Europe and Asia. Ready material is generally dispatched within 1 to 2 days, while produced-to-order flanges require around 30 days, subject to the confirmed specification.
Testing and inspection are completed before dispatch. Dimensional inspection is performed against the applicable ASME requirements, while positive material identification verifies the material grade. Dye penetrant inspection and third-party inspection can also be arranged when required by the purchase order.
Every dispatch carries an EN 10204 3.1 mill test certificate, while 3.2 certification is available when specified. Our company holds AS 9120B, PED, ISO 9001:2015 and ISO 45001:2018 certifications.
Contact Amigo Impex for a dated quotation based on your confirmed specification.
Request a Quote60–70 tonnes held in Mumbai, with urgent requirements dispatched within one to two days.
AS 9120B, PED, ISO 9001:2015 and ISO 45001:2018, with an MTC on every order.
Cutting, machining, threading, fabrication and testing all handled at our own Mumbai facility.
Original mill certificates plus our own test reports, so every batch can be traced back.
Non-standard sizes and specifications made to order.
Dispatched from Mumbai to every major Indian city, and exported to USA, Gulf, Europe, Asia
A duplex steel flange is a forged piping component manufactured from dual-phase ferritic-austenitic stainless steel. It is used to create bolted connections between pipes, valves and equipment and is manufactured to ASTM A182 with dimensions governed by standards such as ASME B16.5 or B16.47.
Yes, duplex flanges generally provide higher yield strength and better resistance to chloride stress corrosion cracking than conventional 316 stainless steel. However, 316 stainless steel can offer better impact toughness in some applications. The correct choice depends on the service environment and design requirements.
Duplex 2205 flanges are supplied to ASTM A182 F51 (UNS S31803) and F60 (UNS S32205). Lean duplex flanges to ASTM A182 F68 (UNS S32304) are also available against the applicable specification and order requirements.
Duplex steel flanges are available from 1/2" to 24" NB under ASME B16.5 and from 26" to 60" under ASME B16.47. Under B16.5, Classes 150 through 1500 cover the full 1/2" to 24" range and Class 2500 is limited to 1/2" through 12". ASME B16.47 covers Class 150 to 900 in Series A and Class 75 to 900 in Series B.
Duplex and super duplex grades differ mainly in alloy composition and corrosion resistance. Duplex grades such as 2205 contain approximately 22% chromium, while super duplex grades typically contain around 25% chromium and have a PREN above 40.
The range includes weld neck, slip on, blind, socket weld, threaded, lap joint, plate, long welding neck, reducing, orifice and spectacle blind flanges.
Duplex stainless steel flanges are used in industries where high strength and resistance to chloride-containing environments are important.
