Weld Neck Flange

Weld Neck Flange Manufacturer in USA

Weld neck flanges are manufactured with a tapered hub that transitions into the pipe wall thickness, creating a smooth internal bore and reducing turbulence at the joint. The long tapered neck is butt welded directly to the pipe, distributing stress across a wider area and reducing stress concentration at the base of the hub. This design makes weld neck flanges fit for high pressure, high temperature, and cyclic loading piping systems, including subsea and cryogenic service lines.

Material Grades We Manufacture:

Carbon Steel

• ASTM A105 / A105N

• ASTM A350 LF2 / LF3 (Low temperature service)

Alloy Steel

• ASTM A182 F5 / F9 / F11 / F22 / F91

Stainless Steel

• ASTM A182 F304 / F304L / F316 / F316L / F321 / F347

Duplex & Super Duplex

• ASTM A182 F51 (UNS S31803)

• ASTM A182 F53 (UNS S32750)

• ASTM A182 F55 (UNS S32760)

Nickel Alloys

• Inconel 600 / 625 / 825

• Hastelloy C276

• Monel 400

Manufacturing Standards:

• Dimensions: ASME B16.5 (NPS 1/2" to 24"), ASME B16.47 Series A & B (NPS 26" to 60")

• Forging Grade: MSS SP44

• Bore: According to Pipe Schedule (SCH 10 to SCH XXS) or Custom bore

• Face Types: Raised Face (RF), Flat Face (FF), Ring Type Joint (RTJ)

• Marking: MSS SP-25

Pressure Temperature Classes:

• Class 150, 300, 400, 600, 900, 1500, 2500

• PN 6, PN 10, PN 16, PN 25, PN 40 (EN 1092-1, DIN standards)

• Pressure temperature ratings per ASME B16.5 Table 2

Dimensional Specifications:

Manufacturing Process:

1. Raw material billet cutting and heating

2. Open die or closed die forging

3. Rough machining of hub, bore, and face

4. Heat treatment (normalizing, annealing, or solution annealing depending on grade)

5. Final machining to ASME B16.5/B16.47 tolerances

6. Surface finish per RF/FF/RTJ requirement

7. Marking, inspection, and packing

Mechanical Properties (Reference - ASTM A105):

• Tensile Strength: 70,000 psi (485 MPa) minimum

• Yield Strength: 36,000 psi (250 MPa) minimum

• Elongation: 22% minimum

• Hardness: 187 HBW maximum

Testing and Inspection:

• Chemical Composition Analysis (Spectro Test)

• Mechanical Testing (Tensile, Yield, Elongation, Impact)

• Hardness Testing

• Ultrasonic Testing (UT) per ASTM A388

• Radiographic Testing (RT)

• Dye Penetrant Testing (DPT) / Magnetic Particle Testing (MPT)

• Positive Material Identification (PMI)

• Dimensional Inspection per ASME B16.5

Surface Finishes Available:

• Smooth Finish (125-250 AARH)

• Serrated Finish (Concentric or Spiral)

• Stock Finish (per ASME B16.5)

Weld Neck Flange Application:

Weld neck flanges manufactured to these specifications are:

• Oil and gas pipelines and refineries

• Petrochemical processing plants

• Marine and offshore piping systems

• Power generation plants

• Water treatment and desalination infrastructure

• Chemical and fertilizer processing units

• Cryogenic and LNG piping systems

Advantages of Weld Neck Flanges:

• Smooth Bore Alignment: There is perfect fit-up between the taper of the hub and the inner diameter of the pipe, which eliminates turbulence and erosion at the joint.

• Stress Distribution: There is a gradual increase in thickness from the flange to the pipe, reducing the stress concentration at the weld.

• Fatigue Resistance: Full penetration butt weld construction withstands repeated pressure and temperature cycling better than slip on or socket weld types.

• Suitability for Extreme Conditions: Performs under high pressure, sub zero, and elevated temperature service, including cryogenic and high pressure gas lines.

• Leak Tight Joint: The butt welded joint connection to the pipe decreases the chances of leakage from the joint as compared to the threaded or socket weld joints.

• Radiographic Inspection: Full penetration weld joints enable 100% radiography test on the joint.

• Long Service Life: Forged, single-piece joint with no internal joints minimizes the chances of fatigue crack.

Custom Manufacturing Capabilities:

• Non standard bore sizing (bore to match)

• Special hub lengths per client drawings

• Low temperature impact tested grades (LTCS)

• Sour service metallurgy per NACE MR0175 / MR0103

• Third party witnessed inspection and testing