A risk-based approach to inservice inspection

Relates in-service inspection (ISI) reliability and frequency directly to risk so as to balance the risk associated with ISI over a set of components. This approach is based on the fundamental assumption that the purpose of ISI is to detect and correct a degraded condition, which, until it is corrected, leads to an increase in risk. The increased risk is a function of the consequences of failure and the time to detect the degraded condition. The ISI strategy for a set of components is said to be risk balanced if the increased risk is constant over the set of components. For a balanced strategy, the product of inspection frequency and detection probability is proportional to the increase in component failure rate which can be detected and corrected by ISI. This result implies a tradeoff between inspection frequency and detection probability