Alloy Steel Flanges to EN 1092-1 and EN 10222-2 Now Supplied for European Power, Petrochemical and LNG Projects
2026/09/16
A complete range of alloy steel flanges is now available for European and international projects, manufactured to EN 1092-1 dimensions in forged material grades to EN 10222-2 — including 16Mo3, 13CrMo4-5 (P11), 10CrMo9-10 (P22), 11CrMo9-10 and X10CrMoVNb9-1 (P91) — with equivalent ASTM A182 F1, F11, F22 and F91 options for buyers working to US specifications. All flanges are supplied with EN 10204 3.1 inspection certificates as standard, and are matched to the company's alloy steel seamless pipes, butt weld fittings and bolting programs so that an entire high-temperature piping joint can be sourced and documented from one supplier.
Alloy steel flanges are required wherever carbon steel reaches its limit: main steam and hot reheat lines, superheater headers, hydrogen and hydrotreating units, high-temperature process piping and low-temperature LNG systems. The grade selected determines not only strength but the temperature ceiling of the whole joint — and, critically, the welding, heat treatment and bolting procedures that must accompany it.
| Standard | Scope |
|---|---|
| EN 1092-1 | Circular steel flanges — dimensions, pressure classes PN 2.5 to PN 400, DN 10 to DN 4000, and type/face designations (Type 11 weld neck, Type 12 slip-on, Type 05 blind, Type 02 lap joint, Type 01 plate, Type 04/Type 13 threaded and other variants on request). Face executions Form A (flat) and Form B (raised). |
| EN 10222-2 | Forged steel flanges and flanged fittings for pressure purposes — the material standard governing 16Mo3, 13CrMo4-5, 10CrMo9-10, 11CrMo9-10, X10CrMoVNb9-1 and other alloy grades, including heat treatment and mechanical property requirements. |
| EN 10216-2 | Seamless steel tubes for pressure purposes with specified elevated-temperature properties — the pipe standard the flange grade is normally matched against. |
| EN 13480 | Metallic industrial piping — system-level requirements for flanged joints, bolting, gasket selection and assembly. |
| EN 10204 | Inspection documents — 3.1 certificates as standard, 3.2 with third-party endorsement on request. |
| PED 2014/68/EU | European Pressure Equipment Directive — material and documentation compliance route for flanges used in pressure equipment and piping. |
| EN ISO 10893 / EN 10228 | Non-destructive testing of seamless tubes and forgings — UT, MT/PT and dimensional verification. |
| NACE MR0175 / ISO 15156 | Materials for sour service — hardness limits and heat-treatment controls for wet H₂S environments. |
The following grades cover the majority of European high-temperature and cryogenic project specifications. Each is supplied with a matched pipe and fitting equivalent, so that the joint material is consistent from pipe to flange.
| Grade | Material No. / ASTM Equivalent | Typical Service | Application Scenarios |
|---|---|---|---|
| 16Mo3 | 1.5415 / A182 F1 | Up to ~500 °C | Boiler external piping, CHP and industrial power plants, steam drums and low-pressure superheater connections; the entry grade for molybdenum-alloyed carbon steel piping |
| 13CrMo4-5 (P11) | 1.7335 / A182 F11 Cl.2 | Up to ~540–560 °C | Superheater and reheater outlet lines, main steam piping in conventional thermal plants, hot process lines in refineries and chemical plants; the most widely used 1.25Cr grade |
| 10CrMo9-10 (P22) | 1.7380 / A182 F22 Cl.3 | Up to ~560–600 °C | Hydrotreating and hydrocracking reactor piping, high-temperature steam headers, hydrogen-rich process lines, hydrocracker and reformer circuits, coal-gasification piping |
| 11CrMo9-10 | 1.7383 / A182 F22 variant | Up to ~580 °C | Heavy-wall steam and hot reheat piping where improved elevated-temperature strength over 13CrMo4-5 is required at moderate cost |
| X11CrMo5 (P5) | 1.7362 / A182 F5 | Up to ~600 °C | Refinery process piping handling high-sulphur feedstocks, resistance to high-temperature sulphidic corrosion in crude and vacuum units |
| X11CrMo9-1 (P9) | 1.7386 / A182 F9 | Up to ~600 °C | Heater tubes and outlet manifolds, flare lines, high-temperature hydrogen service where 9Cr chemistry improves oxidation and sulphidation resistance |
| X10CrMoVNb9-1 (P91) | 1.4903 / A182 F91 | Up to ~620 °C | Main steam and hot reheat lines in supercritical and ultra-supercritical power plants, HRSG high-pressure circuits, waste-to-energy boilers, solar thermal steam lines; chosen for creep strength and thinner wall thickness at high pressure |
| Low-temperature alloy grades (e.g. 10Ni14, 12Ni19) | 1.5637 / 1.5680 | Down to ~ −100 °C | LNG and cryogenic piping, liquefied gas terminals, low-temperature storage tank connections where nickel-alloyed steel maintains impact toughness |
Alloy flanges fail — or pass inspection on the dock and fail in service — for a small number of predictable reasons. These are the precautions the company builds into every order.
1. Never substitute a lower grade for a higher one. Replacing P91 with P22 in a supercritical main steam line, or P22 with P11 in a hydrocracker circuit, is not a cost optimisation — it silently reduces the permissible temperature, forces thicker walls or reduces design life. Grade substitution must be approved by the piping designer and re-verified against the stress calculation.
2. Match the flange grade to the pipe and fitting grade. A P91 flange welded to a P22 pipe creates a dissimilar-metal joint requiring a qualified welding procedure, controlled PWHT and often a transition piece. Grade consistency from pipe to flange to fitting is the cheapest way to keep the weld procedure qualification valid.
3. Bolting must follow the flange material, not the flange size. A P91 main steam flange at ~600 °C needs EN 10269 X22CrMoV12-1 (or A193 B16) stud bolts to resist stress relaxation; ordinary 8.8 or B7 bolting relaxes, loses gasket seating stress and leaks within the first thermal cycles. Above approximately 450 °C, specify creep-resistant bolting grades.
4. Heat treatment and hardness are process requirements, not options. P91 flanges need normalizing plus tempering with controlled cooling, and a hardness normally limited to ≤ 250 HB for acceptable toughness and weldability. Hardness above the specified limit usually indicates a heat-treatment deviation and is a legitimate reason for rejection.
- Positive Material Identification (PMI): verify Cr, Mo and V content on 100% of alloy flange lots — mixing P22 into a P91 consignment is the single most expensive material error in high-temperature piping
- Post-weld heat treatment (PWHT): chromium-molybdenum and 9Cr grades require controlled PWHT with a documented temperature record; PWHT parameters must fall within the qualified welding procedure range
- Gasket selection: hard spiral-wound or metal-jacketed gaskets on high-temperature alloy joints need adequate bolt load — size the flange, gasket and bolting as one system to EN 13480 guidance
- Sour service: for wet H₂S duty, hardness and chemistry must comply with NACE MR0175 / ISO 15156; do not assume a standard EN 10222-2 delivery meets it without a specific statement on the certificate
- Type IV cracking awareness: in 9Cr steels, the fine-grained heat-affected zone is creep-weak; joint design, weld preparation and PWHT records should reflect this for P91 flanged connections
- Face protection and storage: raised faces and ring joint grooves must be protected in transit; alloy flanges should be stored segregated by grade to prevent mixing at the fabrication yard
Alloy flanges are supplied alongside the company's alloy steel seamless pipes to EN 10216-2/-3/-4, butt weld fittings to EN 10253-2, forged and plate flanges to EN 1092-1, pipe supports and hangers to EN 13480, and industrial fasteners to EN ISO 898, EN 15048, EN 14399 and EN 10269. Sourcing a complete joint from one supplier means the pipe, flange, fitting and bolting grades are cross-checked before shipment, welding procedure qualification stays valid, and third-party inspection receives one consistent documentation package rather than four incompatible sets of certificates.
- EN 10204 3.1 certificates as standard — chemical composition, mechanical properties and heat treatment records; 3.2 with third-party endorsement on request
- PMI verification on alloy material lots; hardness testing on 9Cr and Cr-Mo grades
- Non-destructive testing to EN 10228 for forgings; dimensional and face inspection per EN 1092-1
- Materials suitable for PED 2014/68/EU application; NACE MR0175 / ISO 15156 compliance statement available for sour service orders
- Export packaging with face and bore protection for ocean freight
Alloy flanges in 16Mo3, 13CrMo4-5, 10CrMo9-10, 11CrMo9-10, X11CrMo5, X11CrMo9-1 and X10CrMoVNb9-1 (P91) are available from stock or on short production cycles in EN 1092-1 types and pressure classes; low-temperature nickel grades and large-diameter or heavy-wall items are produced to order. Dimensional tables, pressure-temperature ratings and grade cross-reference sheets are available on request from the technical sales team.
OK Pipes is a manufacturer and exporter of steel piping products and components serving the European and global market. The product range covers alloy steel seamless pipes to EN 10216-2/-3/-4, alloy and forged steel flanges to EN 1092-1 and EN 10222-2, butt weld fittings to EN 10253-2, coated steel pipes, pipe supports and hangers to EN 13480, and industrial fasteners to EN ISO 898, EN 15048, EN 14399 and EN 10269. All products are supplied with EN 10204 inspection certificates and full material traceability.
Media Contact:
Amy — Sales Manager
Email: Amy@okpipes.com
Website: www.alloysteelseamlesspipe.com
