Fracture mechanics assessment procedures, such as BSI PD6493:1991, R6 and ASME XI, have become well established in industry. These published procedures provide methods for assessing the acceptability of flaws in fusion welded structures. For such procedures to be used with confidence, it is essential that their application be validated by comparison with large scale fracture mechanics tests, and actual structural failures. This paper describes eight industrial pressure vessel failures, for which PD6493 fracture assessments have been performed. It has been demonstrated that the assessment procedures are safe to use, provided that input data are reliable.