Fitness for Service of Corroded Pressure Vessel

Fitness for service assessment is performed to ensure that damaged process plant equipment, such as corroded pressure vessels are fit to operate safely and reliably. API RP 579 provides a general procedure for assessing fitness for service of corroded and damaged pressure vessel. The assessment procedure evaluates the remaining strength of the equipment in its current condition and recommends necessary action for repair or replacement. This project will analyze the accuracy of API 579 Fitness for Service (FFS) analysis on corroded pressure vessel. There are three levels of assessment covered in API 579 which are Level 1, 2 and 3. Typically, FFS Assessment is done by using Level 1 and Level 2 since they utilize minimum amount of inspection and known to be conservative. Level 3 Assessment requires most detailed inspection and uses Finite Element Analysis method to give in-depth analysis of the stress involved and projects the remaining life of the corroded pressure vessel. The objective of the project is to conduct and compare Level 3 analysis of the corroded pressure vessel with Level 1 and 2 analyses. Results from these assessments shows that FEA method can verify the calculation done in Level 1 and 2 Assessments. Level 1 and 2 assessments produce conservative results while Level 3 is more accurate. Level 3 Assessment with added capability to visualize stresses involved proven to be useful for critical engineering decision. This capability will assist engineer to confidently decide critical cases in engineering problems. The utilization of Level 3 of FFS provides an accurate assessment of the corroded pressure vessel compared to Level 1 and 2 and also provide added advantage to simulate the operating condition for future planning.