Cumulative Detection Probability as a Basis for Pressure Vessel Inspection Intervals

Abstract

This work discusses use of the cumulative flaw detection probability as the basis for establishing pressure vessel inspection intervals. The method is based on the accumulated probability of detecting a flaw over several inspections. It explicitly incorporates a user decision as to the acceptable level of failure risk. A four-step approach is outlined including fracture mechanics flaw growth calculations with probabilistic treatment of detection probability. It is concluded that (a ) inspection intervals based on the cumulative probability of detection provide significant advantages over traditional cycle-based methods, (b ) pressure vessel recertification inspections should rely on high percentage inspections conducted on a relatively infrequent basis.