Welding Fabrication Standards - EWF

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Welding Fabrication Standards Page 44 Unforeseen factors may arise that require design modifications and/or manufacturing concessions. These need to be handled with the same rigour as the original design. 4.3 EN 13445 – 2: Materials This Part deals with the general philosophy on materials, material grouping and low temperature behaviour in relation to Room Temperature performance range providing the general requirements for establishing technical delivery. It is limited to steel with sufficient ductility and excludes at present materials operating in the creep conditions. Furthermore it includes four annexes, which give further details as relate to: − material grouping system, (according to CR ISO 15608:2000) with a list of all acceptable material grades based upon European base material standards; − information on the requirements for the prevention of brittle fracture in the base material and the welds (two methods based upon a code of practice developed from fracture mechanics are included); − information on technical delivery conditions for clad products; − survey on European base material and component standards and their systematic nomenclature. 4.4 EN 13445 – 3: Design This Part of the standard gives the rules to be used for design and calculation under internal and/or external pressure (as applicable) of pressure bearing components of Pressure Vessels, such as shells of various shapes, flat walls, flanges, heat exchanger tubesheets, including the calculation of reinforcement of openings. Rules are also given for components subject to local loads and to actions other than pressure. For all these components three different design approaches are considered: − Design by Formulae (DBF), as appropriate formulae are given in order to find stresses, which have to be limited to safe values; these formulae are generally intended for predominantly non-cyclic loads, i.e. for a number of full pressure cycles not exceeding 500; − Design by Analysis (DBA), which can be used either to evaluate component designs or loading situations for which a DBF method is not provided, or, more generally, as an alternative to DBF. − Design by Formulae (DBF), based on limit analysis for certain components (such as flanges and tubesheets). Methods are also given where a fatigue evaluation is required, due to a number of load cycles being greater than 500. There are two alternative methods: Istituto Italiano della Saldatura Lungobisagno Istria, 15 - 16141 Genova (I) - Tel. 01083411 - Fax 0108367780
Welding Fabrication Standards Page 45 − a simplified method based on DBF (valid only in case of pressure variations); − a sophisticated method based on a detailed determination of total stresses using, for example, FEM or experimental methods, to be used also in the case of variable loads other than pressure. Figure 13 – Chart in EN 13445 – 3 (Correction factor fm to take account of mean stress in unwelded material for N > 2x106 cycles) As already stated, for the time being, the scope of Part 3 is limited to steel components working at temperatures lower than the creep range of the specific material concerned. 4.5 EN 13445 – 4: Fabrication The philosophy in Part 4 is based on existing good practice in current European Standards, as relates requirements for the manufacture of unfired pressure vessels and their parts, made of steels, including their connections to non-pressure parts. It specifies requirements for material traceability, manufacturing tolerances, welding requirements, production tests, forming requirements, heat treatment, repairs and finishing operations. Part 4 is not applicable for pressure vessels and parts made of spheroidal graphite cast iron for which separate and different requirements regarding manufacturing are given in EN 134445-6. 4.5.1 Specific requirements for the Manufacturer According to the standard the following requirements shall be fulfilled by the Manufacturer: − the organisation (and relevant responsibilities) for the control of manufacturing operations, which includes special processes such as welding, forming and heat treatment shall be clearly defined by the Manufacturer; Istituto Italiano della Saldatura Lungobisagno Istria, 15 - 16141 Genova (I) - Tel. 01083411 - Fax 0108367780
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Welding Fabrication Standards - EWF

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