ISO 3834 parts 2, 3 and 4: which part fits your company

ISO 3834 sets quality requirements for the fusion welding of metallic materials. The standard recognises that weld quality cannot be fully verified after the fact: a weld can look sound and still contain internal imperfections. ISO 3834 therefore focuses on controlling the whole process, from contract review and work preparation to execution, testing and records.

The standard offers three certifiable levels: part 2 with comprehensive quality requirements, part 3 with standard quality requirements and part 4 with elementary quality requirements. Part 1 helps select the appropriate level and part 5 lists the referenced documents. This article explains what each part demands, which part suits which type of company and how the standard connects to EN 1090 and to your clients' requirements.

Why ISO 3834 exists: welding as a special process

Welding is a special process: the end result cannot be fully verified by inspecting the product. Radiographic or ultrasonic testing reveals many imperfections, but properties such as toughness, hardness and the condition of the heat-affected zone cannot be measured on the finished product. Quality must therefore be built into the process. ISO 3834 translates that into concrete elements: qualified welding procedures, qualified personnel, suitable and maintained equipment, control of welding consumables, and demonstrable checks before, during and after welding.

Part 2: comprehensive quality requirements

ISO 3834-2 is the most demanding level and covers all quality elements in full. It requires, among other things:

• Full contract and design review, including weldability assessment.
• Qualified welding procedure specifications, typically to EN ISO 15614-1, and welders qualified to ISO 9606-1.
• Welding coordination to ISO 14731 with documented tasks and responsibilities.
• Control of parent and filler materials, including storage and identification.
• Post-weld heat treatment where required, with records.
• Complete quality records and traceability where specified.

Part 2 suits companies working on safety-critical structures: EXC3 and EXC4 work, pressure equipment, rail, offshore and petrochemical fabrication.

Part 3: standard quality requirements

ISO 3834-3 contains the same type of elements as part 2, but with less depth. Welding coordination, qualified procedures and qualified personnel remain mandatory, but the requirements for documentation, traceability and subcontractor assessment are lighter. Part 3 is the natural level for the average fabrication shop delivering EXC2 work: halls, stairs, platforms and general structural steel. For many companies it is the most cost-effective choice, giving clients sufficient assurance without the full administrative depth of part 2.

Part 4: elementary quality requirements

ISO 3834-4 limits itself to the basics: work must be carried out to the contract requirements, with suitable equipment and personnel who demonstrably master the job. Qualified welding procedure specifications are not required and record-keeping obligations are minimal. This level suits simple welding without a structural safety function, comparable to EXC1. Note that many clients and most certification bodies consider part 4 too light to provide confidence on its own; in practice, Dutch companies almost always certify to part 2 or part 3.

The relationship with EN 1090

EN 1090-2 links the execution class to an ISO 3834 level: EXC1 corresponds to part 4, EXC2 to part 3, and EXC3 and EXC4 to part 2. A company seeking an FPC certificate under EN 1090-1 for a given class must demonstrably meet the welding-related requirements of the corresponding ISO 3834 part. A separate ISO 3834 certificate is not mandatory for that, but it simplifies the notified body's assessment and is often requested in its own right by clients outside construction, for example in machine building. Our article on the execution classes under EN 1090-2 explains which class applies to your work.

Client requirements and other standards

ISO 3834 also appears outside EN 1090. Pressure equipment manufacturers use it as the backbone for the welding-related requirements of the PED. Rail applications follow EN 15085, which builds on ISO 3834. And a growing number of buyers of welded products demand an ISO 3834 certificate contractually, even without a legal obligation, because it demonstrates a controlled welding process. ISO 3834 is complementary to ISO 9001: where ISO 9001 governs the management system, ISO 3834 governs the technical control of welding. Both systems can be integrated without duplication.

Choosing and implementing the right part

The choice follows from your products and your market: which execution classes or product categories you supply, what your clients demand and which standards apply in your sector. Do not automatically pick the heaviest part: certifying to part 2 when your work calls for part 3 means a permanent administrative cost without demonstrable benefit. During implementation, welding coordination to ISO 14731 and the qualification of procedures and welders are usually the biggest steps. Independent ISO 3834 support helps set up a system that fits your work without unnecessary ballast.