Analysis of Hydrogen-Induced Cracking and Lamination in a Pipeline Steel Based on Fitness-For-Service Assessment

Abstract

Abstract Introduction: Fitness-for-service (FFS) assessment is one of the standard methods used in oil and gas structures. This method is for assessment the defects of pipes and equipments, which can be operated without repair or replacement if the existing defects are within the accepted range of this standard. Methods: During inspection of an 7-km-long pipeline made of API X52 steel carrying hydrocarbons containing wet H2S, hydrogen-induced cracking (HIC) and Lamination was found at different locations along the pipeline length. Microstructural investigations by scanning electron microscopy (SEM) showed stepwise cracking (SWC) as the result of the presence of MnS inclusions. Fitness-for-service (FFS) assessment based on API579-1/ASME FFS-1 was performed to decide on the pipeline serviceability. Findings: The finite element analysis (FEA) results showed that the HIC-damaged pipeline was acceptable per level-3 FFS requirements and the pipeline understudy was fit for service. The remaining life of the damaged pipeline should also be periodically monitored using failure assessment diagram (FAD).

Keywords

• hydrogen-induced cracking (hic)
• failure assessment diagram(fad)
• lamination
• fitness-for-service (ffs)assessment