Maintenance and Reliability FIG. 16. API-579 (C.19). FIG. 14. Equivalent stress range (P + Q). FIG. 17. API-579 (C.20). as these equations are valid for materials with yield strengths less than or equal to 600 MPa (87 ksi), shown in Eq. 2: (da/dN) = 8.61(10-10 =1.8 ksi√in )(∆K)3.0 tensity value (Eq. 3) was used: ∆Kth (2) Where the below threshold stress in(3) FIG. 19 provides the graphical illustration of the years required by each recorded crack to reach its respective critical sizes while the concerned PSA continued to operate in the H2 plant. Following this FIG. 15. Equivalent stress range (P + Q + F). crack ratio a/d1 . It is taken as the critical crack size when it touches this limit. A crack growth model and associated constants were utilized to estimate the remaining life of the adsorber shell locations with the crack-like flaws based on a 88 AUGUST 2022 | HydrocarbonProcessing.com fracture mechanics approach. The Paris model was chosen for the assessment, as it accounted for environmental effects and was related to cyclic behavior da/dN. The fatigue crack growth equation was used with the Paris Equation (F-1.23) in FFS assessments completed in this analysis, assessment, the NDE-based inspection of the embedded flaws was completed after a 5-yr gap by entering the PSA vessels in an emptied state during the scheduled catalyst change-out activity. The UTbased TOFD technique was employed to establish the data of any growth of these previously detected flaws during this period. The results confirmed that there was no observable crack growth based on the prior baselined NDE results for characterized geometries of the flaws. Takeaway. Based on the stress-fatigue analysis in accordance with the requirements of API-5791 , all SCL locations inhttp://www.HydrocarbonProcessing.com