Life Assessment Based on API579-1/ASME FFS-1 Fitness-For-Service for Cr–Mo Ferritic Steel

Life assessment is necessary for pressured equipment because high temperatures might lead to creep damage. A product or service’s performance and functionality can be seriously affected by creep damage over a prolonged period. Various assessment methods can be used to estimate a material’s service life. Nonetheless, there can be significant differences in the outcomes of every assessment technique. Evaluating microstructure and measuring current thickness without damaging the specimen are two common methods for identifying creep damage. API579-1/ASME FFS-1 provides the fitness-for-service (FFS) approach, which can be performed via microstructure analysis or by measuring the materials’ current thickness. In the first method, the thickness was utilized for calculating stress, which does not consider material degradation and can be used to anticipate how long materials will remain useable using the Larson-Miller parameter (LMP). The second method assesses microstructures by analyzing structural changes in the material that occur in them, including damage conditions, microstructure evolution, and cavity density. This paper presents a comparative analysis of those methods used for the creep assessment that uses the replica method for microstructure characterization and thickness calculation based on operating conditions. The results of the two life evaluation methods vary by approximately 20–40% of the assessed life. The selection of assessments affects replacement, maintenance, and inspection; nevertheless, it remains unclear which option is most appropriate, depending on the assessment method used.