The History of BS 7910 Flaw Interaction Criteria

Abstract

Assessment of flaws and flaw-like indications in engineering components is commonly performed using fitness for service procedures such as the BS 7910 to demonstrate margins for continued operation or to find a limiting state. An individual or multiple flaw indications may be found in a component as a result of fabrication or degradation during operation. Most fitness for service codes provide guidance for assessment of multiple flaws. This consists of simplifying the actual indications into flaws more amenable to analysis using engineering criteria. The subject of this paper is the flaw interaction criteria used by the BS 7910 procedure. The criteria have been refined several times since the 1980 version of the BS 7910 predecessor document PD 6493. This paper will summarise the changes and provide plausible explanations to the changes supported by the experimental data and numerical analysis. A proposed way forward for the 2012 edition of BS 7910 flaw interaction and characterisation will conclude the paper.