Allowable Cracks Related to Penetration for Part-Through Cracks in Pipes Subjected to Bending Stresses

Abstract

Fully plastic collapse stresses for circumferentially part-through cracked pipes subjected to bending stresses are estimated by limit load criteria provided by the ASME Code Section XI. Allowable crack depths were determined by using the limit load criteria and that are tabulated in the ASME Code Section XI for different plant service-level conditions. On the other hand, crack penetration bending stresses for part-through cracked pipes were estimated by using the local approach of limit load criteria. By using these criteria, the study presented in this paper obtained allowable crack depths at penetration for circumferentially part-through cracked pipes. Comparing the allowable crack depths obtained by both methods for each service level, it is evident that the allowable crack depths at penetration calculated by the local approach of limit load criteria are almost always smaller than those at fully plastic collapse stresses calculated by the limit load criteria. It was found that the allowable crack depths provided by the ASME Code Section XI are less conservative for crack penetrations.