Weld Neck Flanges
What are Weld Neck Flanges?
Weld neck flanges (WN flanges) are designed with a long tapered hub that is butt-welded to the pipe, ensuring excellent stress distribution and high-strength joints. These flanges are ideal for severe service conditions involving high pressure, temperature, or cyclic loading.
Asiad Steel Industries manufactures precision-grade weld neck flanges in stainless steel, carbon steel, and special alloys for critical applications worldwide.
Key Features
Leak-Proof
Jointing
Durable
Construction
High Load
Capacity
Wide
Compatibility
Corrosion
Resistant
Specifications
| Specification Category | Parameter / Feature | Details / Options |
|---|---|---|
| Size Range | Nominal Pipe Size (NPS) | ½” to 48” (DN15 – DN1200) |
| Pressure Ratings | ANSI / ASME Class | Class 150, 300, 600, 900, 1500, 2500 |
| PN Ratings | PN6, PN10, PN16, PN25, PN40, PN64 | |
| Flange Types | Weld Neck Flanges | Standard Weld Neck, Long Weld Neck |
| Special Types | Reducing Weld Neck Flanges, Heavy-Duty Weld Necks | |
| Material Options | Stainless Steel | SS 304, SS 304L, SS 316, SS 316L, SS 321, SS 347 |
| Carbon Steel | ASTM A105, ASTM A350 LF2 | |
| Alloy / Superalloy | Alloy Steel (A182 F1, F5, F9, F11, F22, F91), Inconel 600/625/825 | |
| Duplex & Super Duplex | Duplex 2205, Super Duplex 2507 | |
| Other Materials | Monel 400/K500, Nickel 200/201, Titanium (Grade 2, Grade 5), Hastelloy C22/C276 | |
| Standards & Certifications | ASME / ANSI | ASME B16.5, ASME B16.47 Series A & B |
| ASTM | ASTM A182, ASTM A350 | |
| European Standards | EN 1092-1, DIN 2631, DIN 2632, DIN 2633, DIN 2634 | |
| Certifications | ISO 9001, PED 2014/68/EU, NACE MR0175, IBR Approved | |
| Design Features | Neck Design | Long tapered hub to reduce stress concentration |
| Bore Design | Machined to match pipe ID for smooth flow | |
| Face Type | Raised Face (RF), Flat Face (FF), Ring Type Joint (RTJ) | |
| Thickness | As per ASME B16.5 & EN 1092-1 | |
| Tolerance | As per ASME/ANSI standards | |
| Coating & Surface Finish | Anti-Corrosion Coating | Rust Preventive Oil, Black Oxide, Hot-Dip Galvanized |
| Optional Coatings | Epoxy, PTFE, Polyurethane | |
| Surface Finish | Smooth Finish, Serrated Finish, Polished | |
| Testing & Inspection | Pressure Testing | Hydrostatic, Pneumatic |
| Non-Destructive Testing | Ultrasonic (UT), Radiography (RT), Magnetic Particle (MPI), Dye Penetrant (DPT) | |
| Destructive Testing | Tensile, Hardness, Impact |
Dimensions of Weld Neck Flange ASME B16.5 Class 150
| NPS (in) | OD (mm) | Flange Thickness T (mm) | Bolt Circle Diameter BCD (mm) | No. of Bolts | Bolt Size | Hub Diameter HD (mm) | Raised Face Diameter RF (mm) |
|---|---|---|---|---|---|---|---|
| ½” | 89 | 9.7 | 60 | 4 | ½”-13 UNC | 30 | 35 |
| ¾” | 99 | 11.2 | 70 | 4 | ½”-13 UNC | 38 | 43 |
| 1″ | 108 | 12.7 | 79 | 4 | ½”-13 UNC | 49 | 51 |
| 1¼” | 117 | 14.2 | 89 | 4 | ½”-13 UNC | 59 | 64 |
| 1½” | 127 | 15.9 | 98 | 4 | ½”-13 UNC | 65 | 73 |
| 2″ | 152 | 17.5 | 121 | 4 | ⅝”-11 UNC | 78 | 92 |
| 2½” | 178 | 20.6 | 140 | 4 | ⅝”-11 UNC | 90 | 105 |
| 3″ | 190 | 22.4 | 152 | 4 | ⅝”-11 UNC | 108 | 127 |
| 4″ | 229 | 22.4 | 191 | 8 | ⅝”-11 UNC | 135 | 157 |
| 6″ | 279 | 23.9 | 241 | 8 | ¾”-10 UNC | 192 | 216 |
| 8″ | 343 | 26.9 | 298 | 8 | ¾”-10 UNC | 246 | 270 |
| 10″ | 406 | 28.4 | 362 | 12 | ⅞”-9 UNC | 305 | 324 |
| 12″ | 483 | 30.2 | 432 | 12 | ⅞”-9 UNC | 365 | 381 |
| 14″ | 553 | 33.3 | 476 | 12 | 1″-8 UNC | 400 | 413 |
| 16″ | 597 | 35.1 | 540 | 16 | 1″-8 UNC | 457 | 470 |
| 18″ | 635 | 38.1 | 578 | 16 | 1⅛”-7 UNC | 508 | 533 |
| 20″ | 698 | 41.1 | 635 | 20 | 1⅛”-7 UNC | 559 | 584 |
| 24″ | 813 | 46.0 | 749 | 20 | 1¼”-7 UNC | 663 | 692 |
Notes:
These dimensions are for ASME B16.5 Class 150 Raised Face Weld Neck Flanges.
T = Minimum flange thickness; it excludes the raised-face height.
OD = Outside Diameter of flange.
BCD = Bolt Circle Diameter, measured through the centres of bolt holes.
RF = Raised Face diameter.
HD = Weld Neck hub diameter at the flange back / large end of hub.
Raised-face height for Class 150 flanges is normally 1.5 mm (0.06 in.).
Weld neck bore and welding-end dimensions must be selected according to the applicable pipe schedule or wall thickness.
Higher pressure classes, such as Class 300, 600 and 900, have different flange thickness, bolting and hub dimensions.
These dimensions are for ASME B16.5 Class 150 Raised Face Weld Neck Flanges.
T = Minimum flange thickness; it excludes the raised-face height.
OD = Outside Diameter of flange.
BCD = Bolt Circle Diameter, measured through the centres of bolt holes.
RF = Raised Face diameter.
HD = Weld Neck hub diameter at the flange back / large end of hub.
Raised-face height for Class 150 flanges is normally 1.5 mm (0.06 in.).
Weld neck bore and welding-end dimensions must be selected according to the applicable pipe schedule or wall thickness.
Higher pressure classes, such as Class 300, 600 and 900, have different flange thickness, bolting and hub dimensions.
Mechanical Properties
| Property | Value | Unit / Standard |
|---|---|---|
| Tensile Strength | 485 – 750 | MPa (Carbon Steel, Stainless Steel, Alloy Steel) |
| Yield Strength | 170 – 450 | MPa |
| Hardness | 120 – 200 | HB (Brinell) |
| Elongation | ≥ 20 – 30 | % |
| Density | 7.8 – 8.0 | g/cm³ |
| Impact Toughness | ≥ 27 – 70 | J (Charpy, grade-dependent) |
| Modulus of Elasticity (E) | ~200 | GPa |
| Fatigue Strength | 250 – 450 | MPa |
| Corrosion Resistance | Good to Excellent (SS > CS > Alloy Steel) | – |
| Thermal Conductivity | 15 – 50 | W/m·K |
| Coefficient of Thermal Expansion | 11 – 17 ×10⁻⁶ | /°C |
| Yield Ratio (YS/UTS) | 0.40 – 0.65 | – |
| Poisson’s Ratio | 0.27 – 0.30 | – |
| Brinell Hardness Range | 120 – 200 | HB |
| Surface Finish | Serrated / Stock / Smooth finish per ASME B16.5 | – |
| Welding Type | Butt-welded to pipe (per ASME B16.25 bevel ends) | – |
| Operating Temperature Range | -46 to 600 | °C (material-dependent) |
| Pressure Rating | Class 150, 300, 600, 900, 1500, 2500 | ASME B16.5 Standards |
Chemical Composition
| Element | SS 304 (%) | SS 304L (%) | SS 316 (%) | SS 316L (%) |
|---|---|---|---|---|
| Carbon (C) | ≤ 0.08 | ≤ 0.03 | ≤ 0.08 | ≤ 0.03 |
| Manganese (Mn) | ≤ 2.00 | ≤ 2.00 | ≤ 2.00 | ≤ 2.00 |
| Silicon (Si) | ≤ 1.00 | ≤ 1.00 | ≤ 1.00 | ≤ 1.00 |
| Phosphorus (P) | ≤ 0.045 | ≤ 0.045 | ≤ 0.045 | ≤ 0.045 |
| Sulfur (S) | ≤ 0.030 | ≤ 0.030 | ≤ 0.030 | ≤ 0.030 |
| Chromium (Cr) | 18.0 – 20.0 | 18.0 – 20.0 | 16.0 – 18.0 | 16.0 – 18.0 |
| Nickel (Ni) | 8.0 – 10.5 | 8.0 – 12.0 | 10.0 – 14.0 | 10.0 – 14.0 |
| Molybdenum (Mo) | — | — | 2.0 – 3.0 | 2.0 – 3.0 |
| Iron (Fe) | Balance | Balance | Balance | Balance |
Applications of Weld Neck Flanges
Construction &
Infrastructure
Power Generation &
Energy Sector
Manufacturing &
Fabrication
Medical & Laboratory
Equipment
Electrical &
Electronics Assembly
Oil, Gas & Petrochemical
Installations
Do you have questions?
What makes weld neck flanges suitable for critical services?
Do weld neck flanges come in different face types?
What are the standard sizes available?
Are weld neck flanges resistant to thermal expansion?
