Weld Neck Flange 150 lb — ASME B16.5 (A105 / F304 / F316)

A weld neck flange in the 150 lb pressure class to ASME B16.5 is widely specified in utility-piping fabrication for cooling-water headers, fire-system mains, instrument-air manifolds, raw-water lines and other duties inside the selected material's Class 150 pressure-temperature envelope. RP Sales coordinates WNRF enquiries in A105 carbon steel, F304 / F316 stainless steel and F11 / F22 Cr-Mo alloy across the B16.5 dimensional range. This page helps a Kanpur buyer state size, facing, bore, material and the certificate or inspection scope required on the quotation.

Kanpur fabricators and project buyers can request these flanges on an ex-warehouse Kanpur basis, with GST, packing and destination freight shown separately. The quotation must confirm the selected forging shop, material lot, heat marking, certificate scope and release date. Availability and transport are order-specific; this page is not a live stock feed or a multi-state delivery schedule.

What ASME B16.5 covers and where 150# fits

ASME B16.5 is the standard for pipe flanges and flanged fittings from 1/2" through 24" NPS, in pressure classes 150, 300, 400, 600, 900, 1500 and 2500 lb. Larger sizes (26" and up) move to ASME B16.47 (Series A or B). The standard fixes the flange face dimensions, bolt-hole pattern, hub geometry, gasket-seat geometry, the pressure-temperature rating tables for every material group, and the test & tolerance requirements.

A weld neck flange has a tapered hub and butt-weld attachment. Its geometry can help distribute local stress, but that feature does not make it the automatic choice for cyclic loading, thermal movement or bending. The approved piping class and stress analysis must select flange type, class, facing, bore and material. Slip-on, socket-weld, threaded and lap-joint alternatives likewise require project-specific acceptance.

Dimensional reference — selected B16.5 150# WNRF sizes

Dimensions per ASME B16.5 Table 8 and Table 9. Full set of OD, hub length, raised-face Ø, bore (matched to schedule), and bolt-hole detail shared with the quotation.

Material grades — when to use what

• A105 (ASTM A105 / SA-105) — carbon-steel forging grade; use only where the approved piping class and service/material review specify it.
• F304 / F304L — austenitic 18Cr-8Ni stainless, for moderate corrosion, food, pharma, demineralised water.
• F316 / F316L — 18Cr-10Ni-2Mo for chloride / marine / chemical service.
• F11 (1.25Cr-0.5Mo) & F22 (2.25Cr-1Mo) — Cr-Mo alloy forgings for elevated-temperature steam, refinery and power.

Face type — RF vs FF vs RTJ

RF, FF and RTJ are different facing geometries, not automatic consequences of class or service name. Copy the mating equipment face, piping class, gasket type, finish and bolting from the approved joint design. Where a brittle or non-metallic counter-flange is involved, follow the equipment maker’s flange and gasket instructions; where RTJ is specified, verify that both mating faces and the ring designation match.

Documentation and inspection to specify

• EN 10204 type 3.1 MTC — chemistry, mechanicals, heat number, heat-treatment record.
• NDT report — UT for thicker flanges, PT/MT for surface inspection per material grade.
• Third-party inspection (BV, SGS, Lloyds) on request — coordinated through our quality team.
• Tax-compliant GST invoice, e-way bill, weighbridge slip.

Buying 150 lb weld neck flanges in Kanpur

A Kanpur enquiry should lock NPS, class, facing, bore or matching pipe schedule, material, quantity and certificates before asking for a date. A105, stainless and Cr-Mo lines can follow different forging and heat-treatment routes even at the same size. Require the quotation to state whether the selected lot is available or needs production, and obtain the inspection and release milestones before fixing a shutdown date.

For destination delivery, provide the PIN code, total mass, packing requirement, unloading window and needed date. Ask for the carrier estimate separately from the ex-warehouse Kanpur material value and GST. Flanges may share transport with compatible pipe and fittings only when release dates, packing and document segregation align. Quotation validity must be stated on the actual offer.

Start with the Kanpur steel market guide and the steel pipes Kanpur page, check the pipe schedule chart for bore matching, then send the BOQ through the RFQ form.

Who should use 150# weld neck flanges and who should not

Class 150 weld neck flanges appear in many utility and process systems, but the application name does not prove suitability. Check the exact material group and adopted B16.5 pressure-temperature table against the line’s design conditions, then reconcile the facing, gasket, bolting, bore and corrosion review with the approved line class. A105, F304, F316, F11 and F22 each require material-specific verification rather than a universal service assignment.

Do not pick a class from ambient pressure alone or move to another class from a broad pressure band. Use the design pressure and temperature, material group, governing-code table and project margins. Facing selection must come from the approved joint and mating equipment requirements; neither sour-service language nor a cast-iron or FRP label is enough by itself to prescribe RTJ, RF or FF.

Gasket selection by flange face

Facing practice per the RF / FF / RTJ notes on this page, reviewed 24 May 2026.

RFQ checklist for 150# weld neck flanges

A complete flange line reads: NPS and class (for example 6 inch 150# WNRF), bore schedule to match the pipe (Sch 40 or Sch 80), face (RF or FF), material grade (A105), and quantity in pieces. The bore must match the connecting pipe schedule or the weld step becomes a crevice and a radiography headache.

• Size, class, bore, face. State NPS, 150# class, bore schedule and RF or FF face on every line.
• Grade and service. Copy the approved material grade, corrosion basis, temperature range, impact-test or heat-treatment requirements and any applicable sour-service standard.
• Certificates and NDT. State the required EN 10204 certificate type, NDT reports and any buyer-appointed inspection hold points at RFQ stage; confirm the agreed package for the selected forging lot.
• Bolting, gaskets, delivery. State whether nuts, bolts and gaskets are included, piece counts plus spares, packing needs, delivery PIN code and ex-works Kanpur or delivered basis.

Worked example: bolting takeoff for five 6-inch joints

Take a cooling-water header with five 6 inch 150# WNRF joints. Each 6 inch joint in the dimension table uses 8 bolts of M20 size on a 241.3 mm bolt circle. Five joints need 10 flanges and 5 gaskets, and the bolt count is 5 times 8, which is 40 bolt-and-nut sets.

Add 10 percent spares for site losses: 40 times 1.1 is 44 bolt-and-nut sets. The final order is 10 flanges in A105 with bores matched to the header schedule, 5 spiral-wound gaskets and 44 bolt sets. Send this shape of takeoff with schedules filled in.

Common mistakes and inspection points

In practice, flange orders fail on four errors. First, class is selected from an ambient rule of thumb rather than the material-group table at design temperature. Second, the facing and gasket do not match the equipment connection or approved joint design. Third, bore is ordered without the pipe schedule, creating an internal step. Fourth, alloy grades are assumed available without confirming the forging lot, heat treatment and inspection route.

At receipt, verify the flange OD, bolt circle and hole count against the B16.5 table extract, check the heat number against the MTC, confirm RF faces are free of radial scratches, and count bolt sets against the packing list. For F11 and F22 flanges, confirm the heat-treatment record sits in the dossier.

Standards and compliance

ASME B16.5 governs flange dimensions, bolt-hole patterns, hub geometry, gasket-seat geometry and the pressure-temperature rating tables for classes 150 through 2500; Tables 8 and 9 carry the 150# weld neck dimensions quoted on this page. Sizes 26 inch and above move to ASME B16.47 Series A or B. Forging grades follow ASTM A105, ASTM A182 F304 / F304L / F316 / F316L and F11 / F22 practice, and mill certificates follow EN 10204 3.1 or 3.2.

Clause references sit in the Sources list below; the full dimension practice lives on the ASME B16.5 reference, and matching pipe grades on ASTM A106 and ASTM A312.

Key points

• Verify the offered NPS range and pressure-temperature rating against the exact B16.5 edition, material group and approved piping class.
• Facing and gasket must match the approved piping class, mating equipment face and joint design; there is no website default.
• Always state bore schedule with the flange; ratings drop with temperature per B16.5 tables.
• Availability and release timing are confirmed by size, facing, bore, grade, quantity and inspection scope.
• State the required 3.1 or 3.2 document and any TPI hold points on the RFQ; confirm them for the selected lot.

Sources and references

• ASME B16.5, Pipe Flanges and Flanged Fittings, classes 150 to 2500: Tables 8 and 9 for 150# weld neck dimensions (cited by code and clause; no catalogue URL).
• ASME B16.47, Large Diameter Steel Flanges, Series A and B for 26 inch and above (cited by code; no catalogue URL).
• ASTM A105 / A182 forging grades for carbon, stainless and Cr-Mo flanges (cited by code; no catalogue URL).
• EN 10204 3.1 vs 3.2 certification: see the EN 10204 reference.
• Dimension practice and matching pipe grades: see ASME B16.5, ASTM A106 and ASTM A312.

Related catalogue and reference pages: forged fittings (ASME B16.11), seamless pipes, ASTM A106 standard, ASTM A312 stainless, MTC & TPI documentation, sample MTC, Kanpur steel market, steel pipes Kanpur, steel pipes Lucknow, request a quote.

FAQ — 150# weld neck flange selection & procurement