AWS D1.1, ISO 3834 and EN 1090 Explained for People Who Buy Weldments
Three names come up constantly in weldment enquiries and they are frequently used as if they were interchangeable. They are not. They sit at different levels and they answer different questions.
The three levels
ISO 3834 asks: is this organisation set up to weld? It is a quality requirement standard for the welding operation itself. Procedures, welder qualification, equipment calibration, material traceability, inspection, records and a welding coordinator. Three graded parts, with ISO 3834-2 comprehensive, 3834-3 standard and 3834-4 elementary.
AWS D1.1 asks: is this weld acceptable, and how do I qualify the people and procedures making it? It is a structural welding code for steel, widely used in North America. It covers design of welded connections, prequalification of joints, procedure and performance qualification, workmanship and inspection acceptance criteria. Sister codes cover other materials: D1.2 for aluminium, D1.6 for stainless steel.
EN 1090 asks: may this structural component be placed on the market in Europe? EN 1090-1 covers conformity assessment and factory production control for structural steel and aluminium components. EN 1090-2 covers the technical requirements for executing steel structures, with four execution classes EXC1 to EXC4 that scale the requirements with consequence of failure.
So: ISO 3834 is about the shop, AWS D1.1 is about the code the work is done to, EN 1090 is about market access in Europe and carries ISO 3834 inside it.
Which one applies to you
Start from the product and the market, not from the supplier’s brochure.
A machine frame sold as part of a machine. Usually governed by machinery legislation rather than construction products rules. The welding is done to a sensible code, typically AWS D1.1 or an ISO equivalent, with an ISO 5817 quality level for acceptance. Full EN 1090 conformity is often not required.
A structural component for a building, bridge or works in the EU or UK. EN 1090 territory. The fabricator needs factory production control and the right execution class, and this is not something a shop can produce on request for one order.
A pressure retaining part. A different world again, with its own codes. Outside the scope of this article and not something to hand to a general fabricator without being explicit.
Everything else. Most industrial weldments, frames, skids, chutes and bases sit here. Specify the code, the quality level and the inspection, and select a shop whose qualifications cover the material and the process.
What to ask a supplier to show you
For AWS D1.1 or equivalent:
- Welding procedure specifications covering your material, thickness range, joint type and position.
- The supporting qualification records for those procedures.
- Welder qualification records, current, in the relevant ranges.
For ISO 3834:
- The certificate, the part number 2, 3 or 4, the issuing body and the expiry date.
- Who the responsible welding coordinator is and what their qualification is.
For EN 1090:
- The certificate, the execution classes covered and the material grades covered.
- Whether it covers the specific product type you are ordering.
A shop that has these things produces them quickly. A shop that takes two weeks to find them is telling you how often they are used.
The trap to avoid
A certificate on a wall covers a scope. The scope has limits: materials, thickness ranges, processes, positions, execution classes.
An ISO 3834-2 certificate does not mean a shop can weld your duplex stainless. An EN 1090 certificate for EXC2 does not cover EXC3 work. A procedure qualified on 12 mm plate may not cover your 40 mm plate.
Ask what the scope covers, not whether the certificate exists. It is the single most useful question in this area and it is asked far too rarely.
What this site does and does not do
We are a matching service. We ask every shop what it holds, we record the certificate details and the scope, and we pass that to you with the match. We do not issue certificates, we do not audit shops to any of these standards and we hold none of them ourselves.
Verification before you release a purchase order stays with you, as it should, because it is your project and your risk.
A short specification line that works
For most industrial weldments this is enough:
Welding to AWS D1.1 (or EN ISO 15614 qualified procedures). Acceptance to ISO 5817 level C generally, level B on welds W1 to W6. Visual inspection 100 per cent. MT on W1 to W6, 100 per cent. Records to be supplied with the part.
One paragraph, and every shop quoting is pricing the same job.
Send your RFQ with the code named and we will match it with shops qualified for it.
Frequently asked questions
Do I need EN 1090 for a machine frame sold into the EU?
EN 1090 covers structural steel and aluminium components that fall under the construction products rules. A machine frame that is part of a machine is usually governed by machinery rules instead. If the part is structural, load bearing and part of a works, EN 1090 is likely to apply. Get it confirmed for your specific product rather than assumed.
Is ISO 3834 a product standard?
No. It sets quality requirements for the welding organisation, covering procedures, welder qualification, equipment, traceability and inspection. It says the shop is set up to weld properly. It says nothing about whether a particular weld is acceptable.
Can a shop weld to AWS D1.1 without being certified?
AWS D1.1 is a code a fabricator works to, and a lot of competent shops work to it without third party certification. What matters is whether they hold qualified procedures and qualified welders in the relevant ranges, and whether they can show you the records.
Need a quote for this part?
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