RFWN Flanges — short for Raised Face Weld Neck Flanges — are one of the most widely specified flange types in high-pressure and high-temperature piping systems. The term combines two defining features: a raised face gasket surface (elevated above the bolt circle) and a weld neck hub that is butt-welded directly to the connecting pipe. Together, these design elements deliver the highest integrity joint available in ASME B16.5 service.
On an RFWN flange, the raised seating surface concentrates bolt-load onto a smaller gasket contact area, dramatically increasing the unit seating stress — which translates to superior leak-tightness under cycling pressure and temperature. The long tapered hub transitions stress from flange body to pipe wall gradually, eliminating the abrupt cross-section change that causes fatigue failures in slip-on designs. Because the weld is a full-penetration butt weld made at the neck, it can be examined by radiography (RT) or ultrasonic testing (UT), meeting the strictest quality requirements of ASME Section VIII, API 6A, and offshore standards.
Tesco Steel & Engineering is an ISO-certified manufacturer and exporter of RFWN flanges from Mumbai, India, supplying to refineries, petrochemical plants, power stations, desalination facilities, and subsea projects across 90+ countries. All flanges are produced in compliance with ASME B16.5, ASME B16.47, MSS SP-44, API 605, DIN EN 1092-1, and BS 4504 as required.
An RFWN (Raised Face Weld Neck) Flange is a pipe flange that combines two distinct features:
The combination results in a flange that excels in high pressure, high temperature, cryogenic, and corrosive service — exactly the conditions where joint integrity cannot be compromised.
| Face Type | Gasket Surface | Typical Application |
|---|---|---|
| RFWN (Raised Face Weld Neck) | Raised above bolt circle; spiral-wound or RTJ-adjacent gasket | Refineries, upstream oil & gas, power generation — high pressure/temp |
| FFWN (Flat Face Weld Neck) | Flush with bolt circle; full-face soft gasket | Mating cast-iron or bronze equipment; low-pressure water/utility |
| RJWN (Ring Joint Weld Neck) | Machined groove for oval or octagonal metallic ring gasket | API wellheads, high-pressure subsea and sour-service piping |
| RFWN Flanges — Full Material & Dimensional Range | |
|---|---|
| Standards | ASME B16.5, ASME B16.47 (Series A & B), MSS SP-44, API 605, DIN EN 1092-1, BS 4504 |
| Size Range | ½″ NB to 60″ NB (DN 15 to DN 1500) |
| Pressure Classes | Class 150, 300, 400, 600, 900, 1500, 2500 (ASME) · PN 6, 10, 16, 25, 40, 64, 100, 160, 250, 320, 400 (DIN/EN) |
| Schedule / Wall Thickness | SCH 10, 20, 40, STD, 60, 80, XS, 100, 120, 140, 160, XXS |
| Face Finish | Raised Face (RF), Flat Face (FF), Ring Type Joint (RTJ), Tongue & Groove (T&G), Male & Female (M&F) |
| Stainless Steel RFWN Flanges | ASTM A182 F304, F304L, F304H, F316, F316L, F316H, F316Ti, F309, F310, F317L, F321, F347, F904L (UNS S30400–S90400) |
| Duplex & Super Duplex RFWN Flanges | ASTM A182 F51 (UNS S31803/S32205), F53 (UNS S32750), F55 (UNS S32760), F60 (UNS S32101) |
| Alloy Steel RFWN Flanges | ASTM A182 F5, F5a, F9, F11, F12, F21, F22, F91, F92 |
| Carbon Steel RFWN Flanges | ASTM A105, ASTM A694 F42–F70 |
| LTCS RFWN Flanges | ASTM A350 LF1, LF2, LF3 (low-temperature carbon steel, tested to −46 °C) |
| Nickel Alloy RFWN Flanges | UNS N02200 (Ni 200), UNS N02201 (Ni 201) |
| Monel RFWN Flanges | ASTM B564 — UNS N04400 (Monel 400), UNS N05500 (Monel K500), Alloy 20 (UNS N08020) |
| Inconel RFWN Flanges | ASTM B564 — UNS N06600 (Inconel 600), N06601 (601), N06625 (625), N08800 (Alloy 800), N08810 (Alloy 800H), N08825 (Incoloy 825) |
| Hastelloy RFWN Flanges | ASTM B564 — UNS N10276 (Hastelloy C276), N06022 (C22), N10665 (B2), N10675 (B3), N06455 (C4) |
| Titanium RFWN Flanges | ASTM B381 — Gr. 1, Gr. 2, Gr. 5 (Ti-6Al-4V), Gr. 7; DIN 3.7035, 3.7055 |
| Cupro-Nickel RFWN Flanges | ASTM B151 / B564 — UNS C70600 (90/10 Cu-Ni), UNS C71500 (70/30 Cu-Ni), UNS C71640 |
| Special Coatings & Surface Treatments | Hot-Dip Galvanizing (GI) · Sand Blasting (Sa 2.5) · Shot Peening · Epoxy Coating · FBE (Fusion Bonded Epoxy) · PTFE Coating · Electropolishing |
1. Bore Matching for Flow Efficiency
The bore of an RFWN flange is machined to match the inside diameter of the mating pipe schedule. This bore-matching eliminates the internal step that is present in slip-on flanges, preventing turbulence, erosion, and crevice corrosion at the joint. It is mandatory in high-velocity service — gas transmission, cryogenic piping, and pharmaceutical-grade stainless systems.
2. Radiographable Butt Weld
The weld between the RFWN neck and the pipe is a full-penetration groove weld (ASME Section IX) that lies in a straight section, making 100 % radiographic or ultrasonic examination straightforward. No other flange type offers this combination of weld-quality verification. This is why RFWN flanges are mandated in ASME Class 1 nuclear piping, API 6D pipeline valves, and NORSOK M-630 offshore specifications.
3. Raised Face Seating Advantage
By elevating the seating face, the RFWN flange focuses bolt load onto the gasket area rather than spreading it across the entire face. This higher unit gasket seating stress is critical for achieving a leak-tight seal with spiral-wound gaskets (ASME B16.20) at high pressures. A correctly torqued RFWN joint with a proper spiral-wound gasket will remain leak-free through hundreds of pressure and thermal cycles.
4. Tapered Hub Reduces Stress Concentration
The gradually tapering hub of a weld neck flange distributes the bending stress from internal pressure and piping loads over a greater length of metal, lowering peak stress at the weld toe. Published finite-element analyses show that the stress concentration factor (SCF) at the neck-to-pipe weld in an RFWN flange is significantly lower than at the weld toe of an equivalent slip-on flange — which is why RFWN is chosen for fatigue-critical piping, vibrating compressor discharge lines, and seismic zones.
| Industry | Service / Fluid | Typical Grade |
|---|---|---|
| Oil & Gas Upstream | Crude oil, sour gas (H₂S), produced water, wellhead Christmas trees | ASTM A182 F316L, F51 (Duplex), F53 (Super Duplex) |
| Refineries & Petrochemical | Hydrocarbons, hydrogen, HF acid, hot oil, amine treating | ASTM A182 F11, F22, F91, F316L, Alloy 20 |
| Power Generation | High-pressure steam, feedwater, supercritical boilers | ASTM A182 F91, F92, F22 |
| Chemical Processing | Chlorine, sulphuric acid, caustic soda, chlor-alkali | ASTM A182 F316L, Hastelloy C276 (N10276), Titanium Gr. 2 |
| LNG & Cryogenic | Liquefied natural gas, liquid nitrogen, liquid oxygen | ASTM A350 LF3, ASTM A182 F304L, F316L |
| Desalination & Marine | Seawater, brine, produced water, SWRO high-pressure piping | Super Duplex F53/F55, Cupro-Nickel C71500 |
| Offshore & Subsea | Risers, flowlines, manifolds, FPSO topside piping | Super Duplex F53, Inconel 625 (N06625) |
| Water & Wastewater | Potable water, effluent, sludge, irrigation | ASTM A105, A182 F304 |
| Food, Beverage & Pharma | Sanitary process lines, CIP/SIP, dairy, brewing | ASTM A182 F316L (electropolished), F304L |
Selecting the right material for an RFWN flange is as important as selecting the right class. Below is a quick reference guide for the most common service environments:
Click on the class below to access the complete RFWN flange dimension table including bolt-circle diameter, number of bolts, hub length, and bore dimensions for every NPS from ½ to 24 (ASME B16.5) and up to 60 inch (ASME B16.47):
| Standard | Dimension Table Link |
|---|---|
| ANSI / ASME Class 150 RFWN Flange | View Class 150 RFWN Dimensions → |
| ANSI / ASME Class 300 RFWN Flange | View Class 300 RFWN Dimensions → |
| ANSI / ASME Class 400 RFWN Flange | View Class 400 RFWN Dimensions → |
| ANSI / ASME Class 600 RFWN Flange | View Class 600 RFWN Dimensions → |
| ANSI / ASME Class 900 RFWN Flange | View Class 900 RFWN Dimensions → |
| ANSI / ASME Class 1500 RFWN Flange | View Class 1500 RFWN Dimensions → |
| ANSI / ASME Class 2500 RFWN Flange | View Class 2500 RFWN Dimensions → |
Every RFWN flange manufactured at Tesco Steel & Engineering undergoes a rigorous multi-stage quality programme:
Q: What does RFWN stand for in flanges?
RFWN stands for Raised Face Weld Neck. It describes a weld neck flange whose gasket contact surface is raised above the bolting circle face, per ASME B16.5 definitions.
Q: What is the difference between an RFWN flange and a plain weld neck flange?
A "plain" weld neck flange is simply the hub-and-bore design; the face type (RF, FF, RTJ, T&G) is a separate designation. RFWN specifies that the face type is Raised Face — the most commonly used face finish. A weld neck flange ordered without a face designation defaults to RF in most project specifications.
Q: What gasket should I use with an RFWN flange?
Spiral-wound metallic gaskets (SWG) with outer guide ring, conforming to ASME B16.20, are the standard choice for RFWN flanges in Class 150–2500. For Class 150 low-pressure utility service, compressed non-asbestos fibre (CNAF) gaskets are also used. Kammprofile (grooved metal core with soft layer) and ring joint gaskets are used in very high-pressure or high-temperature applications.
Q: Are RFWN flanges available in sour service (H₂S) compliance?
Yes. RFWN flanges for sour service are manufactured with hardness controlled to HRC ≤ 22 (HB ≤ 237) in compliance with ISO 15156-2 / NACE MR0175. ASTM A105 must meet NACE hardness limits; for higher alloys, SS 316L, Duplex, and Super Duplex materials are inherently NACE-compliant at typical service hardness levels.
Q: What is the maximum temperature for an RFWN flange?
Maximum service temperature depends on material: Carbon Steel A105 RFWN flanges are rated to 400 °C per ASME B16.5 temperature-pressure tables; F22 alloy steel to 593 °C; F91 alloy steel to 620 °C; SS 316H to 870 °C (with creep de-rating); Inconel 625 to over 1,000 °C in oxidising atmospheres. Always consult the ASME B16.5 temperature-pressure rating table for the exact material group and class.
Q: How do I identify the pressure class of an RFWN flange from its markings?
ASME B16.5 requires the following markings on every flange: Manufacturer's name or trademark · Material designation (e.g., A182 F316L) · Pressure class (150, 300, 600 etc.) · Size (NPS) · Heat number (for traceability) · ASME B16.5 designation. The class number is usually stamped on the OD face of the flange hub.
Q: Can RFWN flanges be supplied with NACE MR0175 / ISO 15156 certification?
Yes. Tesco Steel & Engineering routinely supplies RFWN flanges with NACE MR0175 / ISO 15156 compliance documentation including certified mill test reports, hardness test results, and third-party inspection reports from internationally accredited bodies.
Q: What is the lead time for RFWN flanges from Tesco Steel?
Standard items in Carbon Steel A105, SS 304L, and SS 316L for Class 150 to 600 in common NPS sizes are maintained in ready stock and can ship within 2–5 business days. Non-standard grades, large diameters (above 24"), and exotic alloy flanges typically carry a lead time of 3–8 weeks depending on quantity and material. Contact us for a precise delivery schedule.
RFWN flange prices are influenced by material grade, NPS, pressure class, quantity, and current metal market rates. Tesco Steel & Engineering offers competitive factory-direct pricing backed by ISO-certified quality and global logistics capability.
To receive an itemised, updated price list with current stock availability, please use the Inquiry Form or contact us via WhatsApp at +91 92233 66922. Our technical sales team responds within 24 hours.
Countries We Export RFWN Flanges To: UAE, Saudi Arabia, Kuwait, Qatar, Bahrain, Oman, Iraq, Iran, Jordan, Israel, Yemen, Afghanistan, Pakistan, Germany, Netherlands, UK, Italy, France, Spain, Russia, Turkey, Kazakhstan, Algeria, Libya, Egypt, Sudan, Nigeria, South Africa, Kenya, Tanzania, Zambia, Angola, Congo, Ghana, Ethiopia, Uganda, Mozambique, Zimbabwe, India (domestic), Singapore, Malaysia, Thailand, Vietnam, Indonesia, Philippines, China, Japan, South Korea, Australia, New Zealand, Canada, USA, Mexico, Venezuela, Colombia, Peru, Brazil, Chile, Argentina.
Domestic Supply — RFWN Flanges in India: Mumbai, Delhi, Bangalore, Hyderabad, Ahmedabad, Chennai, Kolkata, Surat, Pune, Jaipur, Lucknow, Kanpur, Nagpur, Visakhapatnam, Indore, Thane, Bhopal, Pimpri-Chinchwad, Patna, Vadodara, Ghaziabad, Ludhiana, Coimbatore, Agra, Andhra Pradesh, Arunachal Pradesh, Assam, Bihar, Chandigarh, Chhattisgarh, Goa, Gujarat, Haryana, Himachal Pradesh, Jammu & Kashmir, Jharkhand, Karnataka, Kerala, Madhya Pradesh, Maharashtra, Manipur, Meghalaya, Mizoram, Nagaland, Odisha, Punjab, Rajasthan, Sikkim, Tamil Nadu, Telangana, Tripura, Uttar Pradesh, Uttarakhand, West Bengal.