Guidance of welded joints on EN ISO 5817

To minimise these problems the following points should be considered:-

1. Design of the weld based on the loading condition(s) the joint will carry
2. Accessibility to enable ease of welding
3. Control of distortion
4. Careful consideration of the welding environment
5. Matching welding process with materials
6. A factor of safty applied to the design stress of the weld which should be based on the   consequance of weld failure and the level of non destructive testing that is to be carried out.

For example a pressure vessel made to PD5500 category 3, (no radiographic inspection), can be up to twice a thick as an equivalent vessel made to category 2, (10% Radiography). Fillet welds and Partial Penetration welds should be used with care as they contain lack of fusion, they are only suitable for relatively low stressed joints that are not subject to any form of fatigue loading and should be used with a suitable factor of safety, which for fillet welds is at least two.

Once the weld has been designed it is then necessary to decide upon the welding method, this is then documented in the form of a welding procedure specification. The European Welding Standard for welding procedures, EN ISO 15609-1 (formerly EN288 Part 2), gives guidance on the content and format of such a specification.

However this document on its own is not sufficient because we need to prove that this welding method will produce a weld of acceptable quality possessing the right mechanical properties. Therefore it is necessary to simulate the joint in all essential features and weld it under normal production conditions. The completed joint can then be subject to both non destructive and destructive examinations to determine if the joint is going to be suitable for the application.

For most stringent applications the European Standard EN ISO 15614 Part 1 (formerly EN 288 Part 3) is preferred for welding procedure tests in steel materials and part 2 for Aluminium and its alloys. There are other parts of EN 288 that deal with alternative routes for qualifying procedures, other than a procedure test, for less onerous applications. See Welding Procedure Section for details.

Once we have established that the proposed welding method is satisfactory we then have to ensure that the production welds will also be of the same quality. This involves making sure the welders posses the required skill and knowledge to deposit sound welds in accordance with the approved procedure. Whilst we can be confident that the welder who did the procedure will be able, any other welder used must also demonstrate his ability by successfully completing a welder approval test. The preferred standard for this is EN 287 Part 1 for steel and part 2 for aluminium and its alloys. This standard not only tests the performance of the welder but also requires it to be monitored and revalidated every 2 years to ensure that the welders skill can be relied upon.

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