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Are there any codified procedures to evaluate the significance of weld flaws in metallic structures and components?


Frequently asked questions

Fracture mechanics based procedures were developed in the UK in the 1960s and 1970s leading to the publication of PD6493:1980 and the so-called R6 procedure, originally developed by the Central Electricity Generating Board (CEGB). R6 has continued to be developed by British Energy, whilst development of the BSI procedure led to the publication of BSI PD6493:1991 and subsequently to the British Standards Guide BS 7910: 1999, revised in 2000, 2005, 2013 and 2015.

There is also a published code in Japan (WES 2805). In the USA, there are guidelines based on linear elastic fracture mechanics in ASME III and XI, plus the joint API/ASME fitness-for-service procedure [3]

A European fitness-for-service procedure, FITNET, has also been published, covering all major failure/damage modes intended and for use by a range of industry sectors.


  1. BS 7910: 'Guidance on methods for assessing the acceptability of flaws in metallic structures'. British Standards Institution, London.
  2. WES 2805: 'Method of assessment for flaws in fusion welded joints with respect to brittle fracture and fatigue growth'. Japanese Welding Engineering Society.
  3. API 579-1/ASME FFS-1 Fitness-for-Service. American Petroleum Institute.
  4. ASME: 'Boiler and Pressure Vessel Code', American Society of Mechanical Engineers, New York.
  5. FITNET Fitness-for-Service, fracture-fatigue-creep-corrosion, Revision MK8 Vol.1 - Procedure. ISBN 978-3-940923-00-4 January 2008.
    Vol.2 - Annexes ISBN 978-3-940923_01-1, January 2008.

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