Engineers and welders must understand the various quality levels of welding, as outlined by EN 1090/EN ISO 5817. The four execution classes, EXC1 to EXC4, each have their own design parameters and requirements as listed in Table A3 of BS EN 1090-2.
This blog post will break down these four quality levels and help you understand which one is most appropriate for your project.
EXC1: - Quality Level D
Components with elementary quality requirements of average/low importance.
This is the most basic level of welding quality, and it is ideal for projects that require basic strength and stability with minimal aesthetic requirements. Execution class 1 comprises structural components made of steel up to strength class S275 and structural components made of aluminium alloys.
This includes:
- buildings with up to 2 floors (4 floors if detached);
- bending beams up to 5 metres in length;
- projection beams up to 2 metres in length;
- stair railings in residential buildings;
- agricultural buildings such as barns.
EXC2: - Quality Level C
Components with normal quality requirements of average importance.
This level requires more attention than EXC1 in terms of both strength and aesthetics. It should be used for components that need to be both strong and aesthetically pleasing. Execution class 2 comprises all supporting structures made of steel up to strength class S700 and structural components made of aluminium alloys.
This typically includes:
- buildings with between 2 and 15 floors;
- quality Level C components can include parts such as pressure vessels or heat exchangers that need to meet specific standards for safety reasons.
EXC3: - Quality Level B
Components with extended quality requirements of average/high importance.
This is a higher level than EXC2, but it does not require quite as much attention to detail as EXC4. It is ideal for components that need to be strong but do not necessarily have high aesthetic standards. Execution class 3 refers to supporting structures made of steel up to strength class S700 and structural components made of aluminium alloys.
Typical examples include:
- buildings with more than 15 floors;
- pedestrian, bicycle, road and railway bridges;
- crane tracks.
EXC4: - Quality Level B+ Components with extended quality requirements of high importance.
Particularly significant fatigue phenomenons.
This is the highest level of welding quality available, and it should only be used on components that demand both strength and beauty while also being able to withstand significant amounts of stress over time without failing or breaking down prematurely. Execution class 4 comprises all structural components with extreme consequences for people and/or the environment in the event of failure.
This is the highest level of Quality Classification where welded components must meet even greater strength, reliability, and appearance standards than before due to their critical nature within the project itself. These components may also need to be designed specifically for fatigue resistance since they will likely experience cyclic loading during their lifespan.
Examples include items like:
- turbine blades or marine propellers which require extremely high performance from the welds joining them together since failure could result in catastrophic consequences for both people and property alike.
- Also, to rail and road bridges over densely populated residential areas or industrial plants.
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