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 the most-ordered flange in Indian utility-piping fabrication — the default for cooling water headers, fire-system mains, instrument-air manifolds, raw-water lines, low-pressure steam returns, and any process line operating below roughly 14 bar at ambient. RP Sales coordinates 150# WNRF supply from BIS-licensed Indian forging shops in A105 carbon steel, F304 / F316 stainless steel, and F11 / F22 Cr-Mo alloy, in the full B16.5 size range from 1/2" NPS to 24" NPS, with MTC and (on request) third-party inspection. This page is the buyer reference for sizing, facing, material selection, and the documentation we ship with the load.

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.

The 150# class is the lowest pressure class in B16.5 and the most common in non-process utility piping. A weld neck flange (WNF) — with its tapered hub butt-welded to the pipe — transfers stress smoothly from the pipe to the flange and is the preferred attachment for any line that sees cyclic loading, thermal expansion, or bending. The alternatives — slip-on (SO), socket-weld (SW), threaded (THD), and lap-joint (LJ) — each have their niche, but for new construction with butt-welded pipe, WNRF 150# is the workhorse.

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, the default for utility water, air, low-pressure steam, hydrocarbon at ambient.
• 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 (Raised Face) is the 150# default; FF (Flat Face) is required when bolting to a cast-iron pump, FRP equipment, glass-lined vessel, or any brittle counter-flange (a raised face will crack a cast-iron mating surface during bolt-up). RTJ (Ring-Type Joint) is rare at 150# class — it shows up almost exclusively in sour-service / chloride-bearing process loops where even a 150# joint needs the all-metal seal.

Documentation we ship with the flange

• 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.

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

FAQ — 150# weld neck flange selection & procurement