Guide to methods for assessing the acceptability of flaws in metallic structures
What is this standard about?
This British Standard is a guide to assessing if flaws in metallic structures are acceptable. It’s particularly relevant wherever structural integrity is important e.g. pipelines, shipbuilding, turbines, engines, vehicle manufacturing and pressure vessels and equipment.
Who is this standard for?
It’s for industries where any two pieces of metal are welded together. Users will be:
- Risk assessors
- Engineering consultancies
- Oil and gas companies
- Steels manufacturers
- Manufacturers of products using welded steel
- Automotive and aerospace manufacturers
Why should you use this standard?
It gives guidance and recommendations for assessing the acceptability of flaws in all types of structures and components.
Although the standard emphasizes welded fabrications in ferritic and austenitic steels and aluminium alloys, the procedures can be used for analysing flaws in structures made from other metallic materials and in non-welded components or structures. The methods described apply at the design, fabrication and operational phases of the life of a structure.
The standard allows metallic structures to be assessed for fitness of purpose rather than adherence to design and fabrication codes, in order to demonstrate margins for continued operation of the welded structure.
BS 7910 is used to perform an assessment of an existing flaw and support continued operation/repair/replacement decisions, and/or to determine a limiting flaw size for a component subject to a given operating environment and to determine the time to reach the limiting state.
It’s used for sentencing unexpected flaws found in welded joints, failure analysis, setting inspection acceptance criteria, justifying waiver of post-weld heat-treatment, extending the life of structures and justifying deviations from a design code. Specific applications include:
- Assessing a known flaw to determine the fitness-for-service of a flawed structure
- Calculating the defect-tolerance of a structure to inform materials selection, load capacity or inspection requirements
- Justifying waiver of post-weld heat-treatment in thick-walled steel structures
The standard applies to a wide range of different types of materials and structures and to different stages in the lifecycle (design, manufacture, operation, repair, life extension, failure investigation).
What’s changed since the last update?
There are two main changes. The document has been broken down into self-contained clauses and annexes, each with its own bibliography, tables, equations, figures and symbols. This will improve the flexibility and agility of the document in years to come. Also a new Annex V has been added, on strain-based assessment and design.