A SURVEY OF EXPERT OPINIONS ON THE EFFECTIVENESS OF NONDESTRUCTIVE EXAMINATION OF PRESSURE-VESSELS

There is an increasing awareness of the fact that our knowledge about the risk of not detecting defects in heavy section, welded pressure vessels is unsatisfactory. There is only limited understanding of what confidence can and should be given to non-destructive examination. In order to improve the basis for further development as well as for probabilistic assessments, an inquiry into the efficiency of non-destructive examination of pressure vessels was made. Six qualified and experienced specialists on non-destructive examination were interviewed in order to determine their opinion about the efficiency of defect detection. The observations showed that such specialists do not posses the knowledge of statistics that is desirable for a trustworthy assessment of probabilities. They proved to be very uncertain about the efficiency in question, often referring to the assumed high quality of the manufacture of the vessels as a guarantee of safety. In the light of these observations, the current views on the efficiency of defect detection therefore, appear less trustworthy than commonly believed.