Creep Monitoring in High Energy Piping

High energy piping in power plants and industrial installations have a limited life due to creep and fatigue. Creep in steam pipes and headers are a collection of diffusion processes, driven by temperature and mechanical stress, which cause permanent strain. The surface strain is an objective measure for creep and these can be measured using nondestructive examinations. KEMA developed an inspection technique SPICA (Speckle Pattern Image Correlation Analysis) which makes it possible to measure on stream deformation due to creep in critical areas like the heat-affected zone (HAZ) in welds. This paper discusses the measurement method and results of tests on different scales. Also, a procedure for the application of strain measurements in power plants and creep strain criteria for end of life are discussed.