ISO 3834 and EN 1090: What They Actually Mean When You Hire a Steel Fabricator

Almost every fabricator you shortlist will hold ISO 9001. Very few procurement packs ask the follow-up question that actually separates them: can you demonstrate welding quality requirements under ISO 3834, and to which execution class under EN 1090?

The distinction matters because ISO 9001 is a management system standard. It says the company controls its documents, tracks nonconformities and reviews its processes. It says nothing specific about whether a weld will hold.

ISO 3834: quality requirements for fusion welding

ISO 3834 is the welding-specific layer. It comes in three levels:

• ISO 3834-2 — comprehensive quality requirements. The full set, appropriate for structural and pressure-retaining work where failure has serious consequences.
• ISO 3834-3 — standard quality requirements. A middle tier.
• ISO 3834-4 — elementary quality requirements. The lightest tier, for low-consequence work.

A fabricator saying "we are ISO 3834 certified" without naming the part is telling you very little. Ask which part. For structural steel carrying gravity and wind load in an occupied or process facility, you want Part 2.

What Part 2 obliges a fabricator to have

Certification to ISO 3834-2 is not a certificate on a wall. It commits the fabricator to a specific set of controls, each of which leaves evidence you can ask to see:

• A responsible welding coordinator with defined technical knowledge — often an IWE, IWT or IWS qualification.
• Qualified welding procedure specifications (WPS) supported by procedure qualification records (PQR).
• Welders qualified for the processes, positions, materials and thickness ranges they actually work in.
• Control of consumables: storage, baking, issue and return of electrodes.
• Parent material identification and traceability.
• Calibrated inspection, measuring and test equipment.
• Documented treatment of nonconformities and repairs — including repair welding procedures.

EN 1090 and execution classes

Where ISO 3834 addresses the welding, EN 1090 addresses execution of the steel structure as a whole — fabrication and erection. Its central concept is the execution class, EXC1 through EXC4, selected according to the consequence of failure, the type of loading (static or fatigue) and the risk associated with the work.

• EXC1 — lowest consequence. Simple, statically loaded structures.
• EXC2 — the common default for general building steelwork.
• EXC3 — higher consequence structures, and structures with significant fatigue loading.
• EXC4 — highest consequence, where failure is catastrophic.

The execution class drives everything downstream: how much non-destructive testing is required, which weld imperfection acceptance levels apply, tolerance requirements, and how much documentation must be retained. Specifying EXC2 where EXC3 is needed does not save money. It defers the cost until an inspector finds the shortfall.

Who selects the execution class?

The designer does, and it belongs in the project specification. If it has not been specified, ask. A fabricator cannot price a package honestly without knowing it, and a tender return that quietly assumes EXC1 will always look cheaper than one that priced EXC3 correctly.

Reading a certificate properly

When you receive a certificate, check four things:

1. Scope. Certificates are issued against a defined scope of processes, materials and product forms. A certificate covering carbon steel does not cover stainless.
2. Execution class. Named explicitly, for EN 1090.
3. Expiry. Certificates lapse. Check the date, not just the logo.
4. Issuing body. It should be an accredited certification body, verifiable independently.

The practical prequalification pack

For a structural steel package of any consequence, ask every bidder for:

• ISO 9001, ISO 3834 (with part number) and EN 1090 or AISC certificates, in scope and in date.
• Welding coordinator's qualification and CV.
• A sample WPS with its supporting PQR.
• A current welder qualification register.
• A sample inspection and test plan from a comparable project.
• Their NDT arrangement — in-house or named agency, with technician certification levels.
• ICV certificate, if the end client is ADNOC or another participating entity. See our guide to ICV certification and bid scoring.

That pack takes a competent fabricator an afternoon to assemble. A fabricator who cannot produce it in a week is telling you something useful.

Al Saqr Al Ahmar operates an ISO 9001, ISO 14001 and ISO 45001 certified yard in Musaffah, Abu Dhabi, fabricating structural steel and pipeline components for onshore and offshore facilities. See our certifications or request a quote.