Creep fatigue interactions in power plant components

The increasing need for flexible electricity generation means that most components must perform under cyclic operating conditions. The multiplicity of generating options also means that defining a 'typical' cycle is difficult. Thus, in addition to the traditional hot and cold starts and stops, there are requirements for rapid load changes on many occasions followed by operation at generation levels of 30% of rated capacity. These transients and operation at low loads result in complex changes in local pressure, temperature and flow at different parts of a boiler system. Indeed, these differences, in combination with the use of metallurgically complex steels, are such that the range of potential damage mechanisms has increased. Understanding these mechanisms is not straightforward as less post service investigations and root cause analyses are being carried out. EPRI seeks to facilitate expert evaluation of service experience and collaborates on establishing lessons learned to establish best practice. Annual creep fatigue discussions have identified key issues and areas for development related to component design and performance under transient operation. Summary documents have helped guide this international effort in the field of creep fatigue. It is apparent that a coordinated effort is important to ensuring that outcomes are meaningful and impactful. Excellence in science and engineering is necessary to underpin technology which is used by the electricity supply industry to meet current challenges associated with safe and reliable operation of plant. The present paper summarizes achievements on creep fatigue behaviour arising from the EPRI collaborative work and describes on-going commitment to knowledge creation and technology transfer.