Impact of inspection on intergranular stress corrosion cracking for stainless steel piping

The objectives of the work presented in this paper are to perform probabilistic calculations simulating 304 stainless steel piping under conditions of intergranular stress corrosion cracking (IGSCC), and to evaluate alternate inspection strategies and the associated reductions in failure probabilities. The stress corrosion cracking model that is part of the PRAISE code is applied, and the PRAISE predictions are compared with service experience. Because the data from the constant extension rate test (CERT) as implemented in the PRAISE code was judged to overestimate the IGSCC damage, the model was calibrated to match service experience by reducing the CERT contribution to IGSCC damage. A simplified parametric approach has been adopted to characterize IGSCC by a single damage parameter, which depends on the service-related and residual stresses, environment, and degree of sensitization. A matrix of calculations that addresses a wide range of pipe sizes, materials, and service conditions has been developed and executed. Sensitivity studies were performed to gain insight into the critical inputs to the model. Probability of detection curves for IGSCC were established for the pipe wall thickness range of 2.54 cm (1.0 in.) and greater, and the effects of inservice inspection strategies were evaluated.