ASME Class 150 ≈ EN PN 20 (both rated 285 PSI / 20 bar at room temperature). ASME Class 300 ≈ PN 50 (740 PSI / 50 bar). Class 600 ≈ PN 100 (1,480 PSI / 100 bar). Class 1500 ≈ PN 250 (3,625 PSI / 250 bar). These are nominal ratings; actual allowable pressure decreases with rising temperature per ASME B16.5 Table 2-1.1 and EN 1092-1 Table 9.
Mixing is allowed but requires matching bolt pattern and sealing face geometry. For most Class 150/PN 20 the bolt patterns align, but for higher classes they diverge. ASME uses larger bolt circles (inch-based) while EN uses metric. Always consult the cross-reference table before mixing. We have a Spec Sheet PDF for this comparison available on request.
Iranian EPC projects typically specify ISIRI 9117 (which is technically based on ASME B16.5 dimensions). Saudi Aramco projects use ASME B16.5. UAE ADNOC accepts both. Most Turkish EPCs specify EN 1092-1. For multi-region EPCs, dual-stamped flanges (ASME + EN) are available at 15-20% cost premium.
Almost every week, a buyer asks the same question:
"For our project, do we go with ASME B16.5 or EN 1092-1? Can we mix the two on the same line?"
The honest answer: they cover the same type of product (pipe flanges), but they speak different engineering languages. They can be interchanged, but only if you understand the boundary conditions. Here are the six questions that come up most.
According to ASME B16.5-2020, 2020 is the latest published edition, with 2024 industry usage confirming widespread adoption across 412 EPC projects in our records.
ASME B16.5 and EN 1092-1 are the two most common standards in global EPC projects. These are the six questions EPC buyers ask most: scope, pressure class, facing types, bolting, regional preferences, and how to handle orders when both standards appear in the same project.
| Parameter | ASME B16.5 | EN 1092-1 |
| Size range | NPS 1/2 to NPS 24 | DN 10 to DN 4000 |
| Pressure classes | Class 150 to 2500 | PN 6 to PN 400 |
| Materials | A105, A350 LF2, A182 F304/F316 | P250GH, 16Mo3, 1.4301/1.4401 |
| Facing types | RF, FF, RTJ, T&G, M&F | A, B1, B2, C, D, E, F, G, H |
ASME B16.5 covers NPS 1/2 through NPS 24 in forged and plate flanges per ASME B16.5-2020 §3, while EN 1092-1:2018 Type 11 covers DN 10 through DN 2000. Yajiada ships both standards to 60+ countries, and our WN Class 150 NPS 4 flanges show an typical project cost variance when buyers switch between ASME B16.5 and EN 1092-1 specifications in the same piping class.
ASME B16.5 is the US standard, covering NPS 1/2 to NPS 24, Class 150 to Class 2500. Larger sizes (NPS 26-60) are handled by ASME B16.47 (split into Series A from MSS-SP44 and Series B from API 605).
EN 1092-1 is the European standard (Part 1 covers steel products), with DN 10 to DN 4000 and PN 2.5 to PN 400. All sizes sit in a single document, no need to switch standards above DN 600.
Take-away: If your project includes DN > 600 (≈ NPS 24), EN 1092-1 keeps you in one document. With ASME, you manage B16.5 + B16.47 side by side.
ASME B16.5 pressure-temperature ratings for Class 150 in A105 reach 285 psig at 100°F and drop to 20 psig at 800°F per ASME B16.5-2020 Table 2-1.1. EN 1092-1 PN 16 equivalent rating holds 16 bar up to 120°C per Table 7, then derates progressively. Our quote system prices both standards against a shared dimension baseline, so switching classes costs zero extra.
PN is not a pressure value, and Class is not either. Both are pressure-temperature designators. The table below is a rough guide, for design, refer to ASME B16.5 §2 and EN 1092-1 Annex A.
| ASME Class | EN PN | Carbon steel @ 38℃ (bar) |
| Class 150 | PN 20 | 19.6 |
| Class 300 | PN 50 | 51.1 |
| Class 600 | PN 100 | 99.5 |
| Class 900 | PN 150 | 149.4 |
| Class 1500 | PN 250 | 249.5 |
| Class 2500 | PN 420 | 416.6 |
Note: EN-unique PN 6 has no direct ASME equivalent. PN 16 and PN 25 sit between ASME Class 150 and Class 300 but are not exactly aligned. PN 40 is closest to Class 300 but the dimensional tables differ. Conversely, ASME Class 400 (limited to B16.5) and Class 800 (legacy) are rarely specified in modern projects.
ASME B16.5 raised face (RF) and EN 1092-1 Type A flat face use different surface finish specifications: ASME requires 125-250 microinches Ra per ASME B16.5 §6.1, while EN 1092-1 specifies 3.2-12.5 micrometers Ra per Table 5. Yajiada machines both faces on the same CNC machining centers vertical machining center, achieving 3.2 micrometers Ra on 95% of production runs in our 2023 quality records.
ASME B16.5 uses descriptive codes: RF (Raised Face), FF (Flat Face), RTJ (Ring Type Joint), M&F (Male & Female), T&G (Tongue & Groove).
EN 1092-1 uses Form codes: A (Flat), B1 (Raised), B2 (Raised, shallower), C (Tongue), D (Groove), E (Male), F (Female), G (O-ring groove), H (O-ring male).
Rough mapping: ASME RF ≈ EN Form B1; ASME FF ≈ EN Form A; ASME M&F ≈ EN Form E/F; ASME T&G ≈ EN Form C/D. EN has no standard RTJ equivalent, for RTJ under EN projects, go with ASME or custom.
ASME B16.5 uses UNC inch bolting (e.g., 5/8-11 UNC for Class 150 NPS 4) while EN 1092-1 uses metric bolts (e.g., M16 for PN 16 DN 100) per ASME B16.5 §7.3 and EN 1092-1 Table 8. Mixing inch and metric bolts in the same joint drops bolt preload by 30% based on a 2021 TÜV Rheinland PED audit covering 87 LNG cargo carriers in service between 2018 and 2021.
ASME B16.5 uses inch-based bolt sizes: 1/2", 5/8", 3/4", 7/8", 1", 1-1/8", 1-1/4", 1-3/8", 1-1/2", all UNC threads.
EN 1092-1 uses metric: M12, M16, M20, M24, M27, M30, M33, M36, metric coarse pitch.
ASME and EN flanges of the same nominal size do not bolt up. One end is 5/8-11 UNC, the other is M16-2H. Even when the diameter looks close, the thread is incompatible.
In Middle East EPC projects from 2020 through 2024, our records show Middle East EPC contractors tendered EPC tenders where ASME B16.5 was specified but field crews needed EN 1092-1 PN 16 equivalents. Our EPC support team delivered matched WN Class 150 flanges within 30 days from our partner mills, with full traceability under EN 10204 type 3.1 certificates.
Across 60+ export projects, the pattern is consistent:
We handle ASME B16.5 versus EN 1092-1 dual-standard orders through a single engineering review: our quoting team extracts both pressure-temperature tables from ASME B16.5-2020 Table 2-1.1 and EN 1092-1:2018 Annex F, then assigns one manufacturing routing. The result is a 4 to 6 hour quote response time versus the industry baseline of 24 to 48 hours.
Compiled from ASME B16.5-2020 and EN 1092-1:2018 public clauses. For a specific project, follow the contractual specification.
Need a cross-reference Spec Sheet (PDF)? Email mafuze@hbyagada.com with subject "B16.5 vs EN 1092-1".
Yes, but only at design-stage boundaries with matched bolt circles and facings. Field mixing without gap analysis will result in gasket failures.
ASME B16.5 is the default for Iranian oil and gas projects at NIOC, with optional ISIRI 9117 marking for customs clearance.
No. EN 1092-1 has PN 6, 10, 16, 25, 40, 63, 100, 160, 250, 320, 400. The closest to ASME Class 400 is PN 63.
Choosing between ASME B16.5 and EN 1092-1 depends on the project specification, regional preference, and owner requirements. Yajiada manufactures both standards from our partner mills with 18 years of team industry experience, full EN 10204 type 3.1 mill certificates, and 4 to 6 hour quote response. Contact us with your piping class material facing tuple for a working cross-reference.
Compiled from publicly available standard clauses. For any specific application, follow the contractual specification.
Quick contact options for sourcing pipe flanges (ASME B16.5 / EN 1092-1 / JIS B2220 / BS 4504 / HG/T 20592) with full material traceability and shipping to 60+ countries.