ANSI flanges for hydrogen — B16.5 and B16.47

ANSI/ASME Class 150–2500 flanges dedicated to hydrogen service. F316L, F22, Inconel 625/718 ISO 11114-1 compliant materials, H2-service dossier with MTR 3.1/3.2, material-gas compatibility declaration and heat traceability.

ANSI flanges for hydrogen service

ANSI/ASME flanges are the reference standard for pressure connections in hydrogen plants: B16.5 for diameters up to NPS 24 (DN 600), B16.47 series A or B for the large diameters of H2 transport and distribution lines. Flange geometry is universal and identical to any other fluid service — the difference for hydrogen lies in selected materials (316L austenitic steels, nickel-base alloys, F22 for refining services), reinforced quality controls (hardness, surface finish, composition) and complete documentation required by PED categories III/IV regulations for Group 1 fluids.

Roffia supplies ANSI flanges for H2 in the full range of constructive types: Welding Neck (WN) for high-pressure welded lines, Slip-On (SO) for standard applications, Blind for blind ends, Lap Joint for dissimilar couplings, Socket Weld (SW) for high-pressure small diameters, Threaded for threaded applications. RTJ ring-joint flanges are covered in the dedicated page RTJ Ring Type Joint flanges.

All flanges are supplied with complete H2-service dossier: material MTRs with heat traceability, ISO 11114-1 compatibility declaration, 100% dimensional inspection, certified surface finish, hardness tests with NACE MR0175 limits if required.

Technical specifications

Parameter Specification
Construction standardsASME B16.5 (NPS 1/2 – 24), ASME B16.47 series A (MSS SP-44) and series B (API 605) for NPS 26 – 60
TypesWelding Neck (WN), Slip-On (SO), Blind, Lap Joint, Socket Weld (SW), Threaded
Sealing facesRF (Raised Face) standard, RTJ (Ring Type Joint) for Class 600+, FF (Flat Face) for special couplings
DNDN 15 – DN 1500 (NPS 1/2 – 60)
Pressure classes150, 300, 600, 900, 1500, 2500 lb
Standard H2 materialsF316/F316L (forged), F304/F304L, F22, F11, F51 / F55 Duplex, Inconel 625/718, Monel 400
Temperature−196 °C ÷ +540 °C (material-dependent)
Surface finishStock finish (Ra 3.2–6.3 μm) or smooth finish (Ra 1.6 μm) — controllable on request
DocumentationMTR 3.1 standard, 3.2 on request, dimensional inspection, hardness, ISO 11114-1, NACE MR0175 on request

Hydrogen-compatible materials

Material (forged) ASTM standard H2 suitability Notes
F316LA182 F316LRecommendedIndustrial H2 standard up to ~100 bar and moderate T. Stable austenitic.
F304LA182 F304LAcceptablePrefer 316L for greater austenitic stability
F22 (2.25Cr-1Mo)A182 F22RecommendedFor H2/HC refining, high temperatures. Nelson curves.
F11 (1.25Cr-0.5Mo)A182 F11RecommendedLow alloy for medium-temperature service
Inconel 625B564 UNS N06625RecommendedHigh pressures (HRS), severe H2/H2S environments
Inconel 718B637 UNS N07718RecommendedHigh mechanical strength for HRS 700 bar
F51 / F55 (Duplex / Super-duplex)A182 F51 / F55Acceptable with limitsVerify HE in pure high-pressure H2. Excellent for H2 + chlorides/H2S.
A105 (carbon steel)A105 / A350 LF2Not recommended >40 barOnly for low-pressure H2 (network blending). Avoid in HRS.
Cu / Zn alloys—ForbiddenCatalyze unstable hydride formation — absolute ban on H2 lines

Reference standards

Construction and materials

  • ASME B16.5 — flanges and flanged fittings NPS 1/2 – 24
  • ASME B16.47 — large diameter flanges NPS 26 – 60
  • ASME B16.20 — RTJ gaskets (rings)
  • ASME B16.21 — non-metallic flat gaskets
  • ASTM A182 — stainless and alloy steel forgings
  • ASTM A105 / A350 — carbon steel forgings
  • EN 1092-1 — European flanges (ANSI alternative)

H2 compatibility and quality

  • ISO 11114-1 — material/gas compatibility (hydrogen)
  • ISO 11114-4 — hydrogen embrittlement testing
  • ANSI/CGA G-5.6 — hydrogen piping systems
  • NACE MR0175 / ISO 15156 — material hardness for H2/H2S
  • PED 2014/68/EU — pressure equipment directive
  • ISO 19880-1/-3 — hydrogen refueling stations (HRS)
  • API RP 941 — Nelson curves (T/P H2 in refining)

Related hydrogen components

RTJ ring-type-joint flanges →

Ring Type Joint R, RX, BX for Class 600–2500 with permanent metal sealing.

Klinger hydrogen gaskets →

Spiral wound, RTJ, pure PTFE and graphite — ISO 11114-qualified for H2 service.

Hydrogen safety valves →

PED category IV, Ribel brand, complete dossier.

Hydrogen ball valves ANSI →

Trunnion-mounted, fire-safe API 607, ANSI Class 150–1500, Ribel brand.

Go to the sector pillar

See a complete overview of Roffia components for hydrogen plants: applications, technical challenges, standards and all dedicated products.

Hydrogen sector — complete overview

Domande frequenti

Which flange standards are required for hydrogen service?
Hydrogen service primarily uses ANSI/ASME B16.5 (for NPS 1/2 – 24, Class 150–2500) and ASME B16.47 series A or B (for NPS 26 – 60, large diameters typical of transport/distribution lines). In Europe EN 1092-1 (PN 16/25/40/63/100/160/250/320/400) is also accepted if compatible with project specifications. Standard choice depends on project background: ANSI dominates in refining, oil & gas and US-derived chemical plants, EN in European industrial and HVAC engineering. For HRS (Hydrogen Refueling Stations) and 350/700 bar applications, dedicated codes like ISO 19880 are often used with Class 1500 or 2500 RTJ-faced flanges.
Which ANSI pressure class to choose for H2 operating pressure?
The pressure class is selected from pressure-temperature tables in ASME B16.5 based on flange body material: e.g. an F316L Class 600 flange has max PS of ~99 bar at 38 °C, decreasing with temperature. Practical guidelines for H2: Class 150 for H2-methane blending in network (max ~20 bar), biomethane upgrading on gas outlet side. Class 300 for medium-pressure chemical plants (~50 bar). Class 600 for industrial high-pressure H2 lines (~100 bar) — this is the transition zone where preferential RTJ flange use begins. Class 900–1500 for compressed storage, compressors, high-pressure H2 distribution. Class 2500 for HRS 700 bar, cryogenic storage, supply to vehicle dispensers. Always verify temperature derating: a Class 600 at 200 °C drops to ~85 bar.
Which materials for hydrogen-service flanges?
Recommended and to-be-avoided materials follow ISO 11114-1 and ANSI/CGA G-5.6: F316L (forged) — standard for H2 up to ~100 bar and ambient/moderate T, stable austenitic structure, excellent compatibility. F304/304L — acceptable but sensitive to cold martensitic transformation, prefer 316L. F22 (2.25 Cr–1Mo) — used in refining and H2/hydrocarbon environments, compliant with Nelson curves. F11 (1.25 Cr–0.5 Mo) — low alloy for medium service. F51 / F55 (Duplex / Super-duplex) — for corrosive services with H2S co-presence, verify high-pressure pure H2 compatibility. Inconel 625 / 718 — for HRS, high pressures and severe environments. Not recommended for high-pressure H2: A105 (carbon steel) above ~40 bar, martensitic alloys, high-hardness alloys >22 HRC (NACE MR0175 limit). Forbidden: copper and zinc alloys (catalyze formation of unstable hydrides).
Difference between B16.5 and B16.47 — when to use which?
ASME B16.5 covers flanges and flanged fittings for NPS 1/2 – 24 (DN 15 – 600), Class 150–2500. It is the universal standard for most process plants. ASME B16.47 extends the range to NPS 26 – 60 (DN 650 – 1500) and divides flanges into two series: Series A (MSS SP-44) — larger, robust and heavier flanges, typically for pipelines, steam generators, refinery transfer lines; Series B (API 605) — more compact flanges, derived from API 605, used in petrochemical plants where weight and bulk are critical. The two series are not interchangeable in the same dimensions: a B16.47 series A flange does not couple with a series B of the same NPS. For H2 transport and distribution lines (e.g. blending in methane network, hydrogen pipelines) the choice is typically B16.47 based on designer preferences.
Do flanges need to be specifically "H2 service" or are standard flanges OK?
The dimensions and geometry of ANSI/ASME B16.5 flanges are universal: an F316L Class 600 WN B16.5 RF flange is dimensionally identical to that used in any other service. The difference for H2 lies in quality control and documentation: (1) MTR 3.1 certificate with heat traceability, ideally 3.2 countersigned by Notified Body for PED categories III/IV; (2) chemical composition verification with specific limits (e.g. C max 0.03% for L-grade, S max 0.015%); (3) hardness testing with NACE MR0175 limits if H2S co-present; (4) ISO 11114 declaration of compatibility for hydrogen gas; (5) controlled groove (for RTJ) or raised face surface finish; (6) non-destructive testing on request (UT, RT, PT). Roffia supplies standard B16.5 flanges with complete H2-service dossier: same physical product, but with documentation needed to pass INAIL, HSE and end-customer audits.
Does Roffia supply ANSI flanges with full traceability for H2 plants?
Yes. All Roffia ANSI/ASME flanges for hydrogen service are supplied with: MTR 3.1 as standard (3.2 on request), heat certificate with lot traceability, ISO 11114-1 declaration of conformity for material-gas compatibility, 100% dimensional inspection with focus on raised face and RTJ groove (Ra ≤ 1.6 μm), hardness test with numeric report, PED certificate with CE marking for categories I-IV. On request we supply: ultrasonic test (UT) ASTM A578 level B/C, radiographic test, liquid penetrant test (PT) ASME V article 6, extended hardness test NACE MR0175 (with HRC verification on body, face, and heat-affected zone for forgings), Charpy impact test at cryogenic temperature for liquid H2. The complete dossier is formatted for INAIL, HSE and third-party inspector audits.

ANSI flange supply for hydrogen plants

Send us line specifications: DN, ANSI class, required material, face (RF or RTJ), type (WN/SO/Blind/LJ), quantity and applicable standards (PED, NACE, ISO 11114). We supply flanges with complete H2-service dossier and competitive lead times.

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