Welding Fabrication Standards - EWF

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Welding Fabrication Standards Page 38 3 Comparison of ISO 3834 Requirements 3.1 Introduction ISO 3834 incorporates three quality levels that may be included in product standards, regulations and contracts or selected by a Manufacturer. The particular level selected will depend on the nature of the product to be manufactured, the conditions in which it will be used and the range of products manufactured. In this chapter some criteria for the choice of the appropriate level will be given, outlining the differences of every part (and level) of the standard. 3.2 Choice of the appropriate quality level Product standards that require compliance with ISO 3834 have emphasised two critical areas in the choice of quality level. On one hand has been the safety critical nature of the products whilst, on the other, there has been the inclusion of the type of loading (static, dynamic) in the product service environment. At first it should be noted that a Manufacturer compliant at a particular quality level is also compliant at a lower level. Thus, a Manufacturer demonstrating compliance to ISO 3834-2 is also compliant with ISO 3834-3 and ISO 3834-4. This may be relevant for a Manufacturer producing a range of products, some of which may require a comprehensive quality level while others only require a standard or elementary quality level. Such a Manufacture can apply the comprehensive quality level to all its products, or only apply the comprehensive quality level to those products where it is required, and apply the requirements at a lower level for the products for which this is more appropriate. Moreover, a Manufacturer applying ISO 3834 part 2 or part 3 can have some suppliers working on small assemblies or, in some cases, can need some extra welders properly qualified and controlled. In such situations the Manufacturer can require to his suppliers the application of a lower quality level. For example, this is the case of ISO 3834 part 4, that seems the easiest way to comply with the quality requirements for welders on loan. In general, the standard quality level should be suitable for the broad range of products that have a normal safety relevance and may experience dynamic loading. Such products would be Istituto Italiano della Saldatura Lungobisagno Istria, 15 - 16141 Genova (I) - Tel. 01083411 - Fax 0108367780
Welding Fabrication Standards Page 39 manufactured from conventional materials where the weldability is known and the precautions to be taken to ensure mechanical performance and defect avoidance are well documented. Products, which have a very limited safety component and are subjected to only moderate static loads with minor dynamic components, would normally only require the elementary quality level. Where the safety factors are significant and there are high static and dynamic loading and the materials are designed for high performance applications, the comprehensive quality level would be appropriate. Moreover, in some situations materials and loading seem to be pertinent to standard quality level, but the innovative nature of the design or the use of novel production processes can imply the choice of the comprehensive quality level in place of the standard level. It is not possible to allocate specific quality parts of ISO 3834, i.e., parts 2, 3 or 4, to particular types of products, because there can be different levels of complexity in the design, materials and fabrication processes in any product group. For example, in the case of bridges manufacturing, some bridges are highly complex in the design and are subject to significant dynamic loads. High strength steels may be employed and the product may be subjected to high levels of non destructive testing to meet tight fabrication defect acceptance levels. In contrast, foot bridges use conventional materials with little or no complexity in manufacture and are not subjected to high levels of dynamic loading. 3.3 Comparison chart In the following tables, a comparison chart of the quality requirement of the different parts of ISO 3834 is reported. Requirement ISO 3834 - 2 ISO 3834 - 3 ISO 3834 - 4 Requirements review Technical review Sub-contracting Necessary documentation is required Necessary -documentation may be required Necessary - documentation is not required Necessary - documentation is Necessary - documentation may be required required Treat like a Manufacturer for the specific subcontracted product, services and/or activities, however final responsibility for quality remains with the Manufacturer Table 9 – Comparison chart on ISO 3834 requirement (to be continued ) Istituto Italiano della Saldatura Lungobisagno Istria, 15 - 16141 Genova (I) - Tel. 01083411 - Fax 0108367780
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