One or several, job by job. The regime is a layer on the same backbone — not a different product.
UNI EN ISO 3834 — Quality requirements for fusion welding of metallic materials
The common denominator. EN 1090-2 requires it at every execution class — the level rising with the class (EXC1 → ISO 3834-4, EXC2 → 3834-3, EXC3/4 → 3834-2) — the pressure world adopts it as the welding quality system, and ASME Section IX is its qualification counterpart outside Europe.
Read the UNI EN ISO 3834 pillar → EN 1090 — CE marking of structural steel and aluminium components
The route to placing a structural component on the European market. EN 1090-1 governs conformity assessment and factory production control; EN 1090-2 governs how the steel is actually executed, in four execution classes.
Read the EN 1090 pillar → PED 2014/68/EU — The Pressure Equipment Directive
The European route for pressure equipment above 0.5 bar. Risk categories drive the conformity assessment module, and from category II upward the welding personnel and procedures must be approved by a notified body or recognised third-party organisation.
Read the PED 2014/68/EU pillar → EN 15085 — Railway applications — welding of railway vehicles and components
The railway sector's own welding regime. Certification levels CL1 to CL3 track the highest weld performance class a manufacturer produces; CL4 covers organisations that do not weld but design, procure, maintain or operate. Welding coordination requirements are stricter than the general case.
Read the EN 15085 pillar → ASME BPVC Section IX — Welding, brazing and fusing qualifications
The American route, and the code most often specified on work outside the European Union — dominant in North America and the Gulf. Procedure and performance qualification through essential, supplementary essential and nonessential variables.
Read the ASME BPVC Section IX pillar →