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OEM manufacturerFlangesTG-TDS-001 · Rev. 0 · October 2026

Weld Neck Flange — Technical Data Sheet

Weld neck flanges have a long tapered hub that is butt welded to the pipe. The taper transfers stress smoothly from the flange into the pipe wall and the butt weld can be fully radiographed, making this the flange of choice for high-pressure, high-temperature and cyclic service.

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Specification

ProductWeld Neck Flange
SupplyOEM manufacturer — forged and machined by Teshi Group, India
Design standardASME B16.5
Size rangeNPS ½" to 24" (DN 15–600)
Pressure classesClass 150, 300, 600, 900, 1500, 2500
Weld endBevelled to ASME B16.25; bore to suit pipe schedule
FacingRaised face (RF), flat face (FF), ring type joint (RTJ)
Manufacturing methodForged; machined from forgings
Other standards on requestEN 1092-1, BS 4504, IS 6392, AWWA C207, or to drawing

Materials

Carbon steelASTM A105, ASTM A350 LF2 Cl.1
Stainless steelASTM A182 F304, ASTM A182 F304L, ASTM A182 F316, ASTM A182 F316L, ASTM A182 F321
Alloy steelASTM A182 F11 Cl.2, ASTM A182 F22 Cl.3, ASTM A182 F91
Duplex / specialASTM A182 F51, UNS N08904 (904L)

Typical applications

  • Process, steam and hydrocarbon lines at high pressure or temperature
  • Cyclic and fatigue service
  • Lines requiring full radiography of the flange weld
  • Low-temperature service in A350 LF2

Manufacturing

  • Raw material: forging-quality billets or bars from approved mills, verified by chemical analysis and PMI on alloy and stainless grades.
  • Forming: closed-die or open-die forging, followed by rough machining.
  • Heat treatment: normalising, normalising and tempering, quench and temper, or solution annealing as the material specification requires, with recorded furnace charts.
  • Machining: CNC turning and drilling to ASME B16.5 / B16.47 dimensions and tolerances.
  • Facing finish: serrated spiral or concentric finish of 3.2–6.3 µm Ra (125–250 µin) on raised and flat faces; 1.6 µm Ra (63 µin) maximum on ring-joint groove side walls.

Inspection and testing

  • Chemical analysis and mechanical tests (tensile, hardness; Charpy impact for low-temperature grades) per heat and heat-treatment lot.
  • 100% visual and dimensional inspection against ASME B16.5 / B16.47.
  • Ultrasonic, magnetic-particle or dye-penetrant examination when specified.
  • Positive material identification (PMI) on stainless and alloy steel.
  • Intergranular corrosion test to ASTM A262 Practice E for stainless grades when specified.
  • Third-party inspection at our works as required by the order.

Marking

Hard-stamped on the rim to ASME B16.5 / MSS SP-25: manufacturer's mark, size, class, facing, bore / schedule, material grade, heat number and standard.

Documentation

Mill test certificate to EN 10204 3.1 (3.2 with third-party inspection on request), dimensional inspection report, heat-treatment record where applicable, and NDT reports as specified. IBR certification on request.

Packing

Rust-preventive coating on machined surfaces, plastic end / face protectors, and seaworthy wooden cases or pallets marked with PO line, size, heat number and quantity.

Ordering information

Please state the following on your enquiry:

  • Type, nominal size (NPS) and pressure class
  • Facing: raised face (RF), flat face (FF) or ring type joint (RTJ)
  • Bore or pipe schedule (weld neck, socket weld and lap joint)
  • Material specification and grade
  • Standard: ASME B16.5 or ASME B16.47 Series A / B
  • Supplementary requirements: NDT, impact test temperature, NACE MR0175, IBR, third-party inspection
  • Quantity and delivery point

Reference information compiled from the published standard for convenience. It does not replace the current edition of the governing standard, which takes precedence. Verify critical dimensions and properties before design, purchase or fabrication. Teshi Engineers & Sales Promoters (P) Ltd accepts no liability for errors or omissions.

Dimensions

FAQ

Weld Neck Flange: common questions

When should a weld neck flange be used instead of a slip-on flange?

Use a weld neck flange for high pressure, high temperature, cyclic loading or wherever the joint must be fully radiographed. Slip-on flanges suit lower-pressure utility service.

What bore is a weld neck flange supplied with?

The bore is machined to match the inside diameter of the pipe, so the pipe schedule must be stated on the order.

Ready to build to spec?

Share your drawing, bill of materials or technical requirements with the Teshi team.