Fitness-for-Service Assessment of Local Thin Area in a Line Pipe

Fitness-for-service (FFS) assessment of a line pipe that contained a metal loss was performed in this investigation. The initial inspection found that a leaking hole in the pipe caused shut down of the whole line. FFS assessment in level 3 based on API579-1/ASME FFS-1 was carried out by considering different damage morphologies including general corrosion, local thin area (LTA) and pitting corrosion. The type of damage was determined as LTA due to corrosion under deposition. To evaluate FFS in level 3, finite element method analysis was utilized, and the results showed that the pipe under containing the damage had remaining strength factor of 0.91 which means that the pipe should return to service until next schedule inspection (around 3 years) based on future corrosion allowance.