Fatigue reliability assessment and updating with on-line nondestructive inspection for pressure vessels

Fatigue reliability assessment of pressure vessels is an important challenge to the engineering profession. The challenge is present during the whole life of pressure vessels. The problem is comprehensively studied and is reported in this paper. A fatigue reliability assessment technique is presented first. Nondestructive Inspections are routinely used to maintain the reliability to an acceptable level during the lifetime of a pressure vessel. At present, information from the nondestructive inspections (NDIs) is rarely used for safety evaluation. Even if no crack is detected during an inspection, it provides valuable information that is often overlooked. A reliability updating method is presented to address this weakness in the fatigue reliability evaluation of pressure vessels. The basic reliability method is extended to estimate the updated reliability. Nondestructive inspections are generally conducted at a specified time interval. To facilitate the continuous fatigue reliability evaluation, an on-line intelligent NDI technology is incorporated. The methodology is explained with the aid of an example. It is expected that the fatigue reliability evaluation of pressure vessels will be significantly improved if the proposed method is used.