Plant-life extension-remanent-life assessment of high-temperature components

To pursue a policy of plant-life extension in the most cost-effective manner it is necessary to avoid component replacements where possible or to plan replacements well in advance. This requires the development of nondestructive techniques and procedures for the prediction of the remaining life of components operating at high temperatures where time-dependent failure mechanisms are operative. These fall into three categories: reduction of the conservatism built into the design codes by the assumptions concerning materials properties and operating conditions, direct measurement of remaining life by the accelerated testing of samples removed from components or by strain measurements on plant, and indirect methods involving metallographic determination of the degree of degradation of the component material. The author briefly describes the development of these techniques and their application to operating plant