Engineering Critical Assessment Applied to Pressure Vessel Following Over-Pressurisation

A 316L Austenitic Stainless Steel pressure vessel developed an internal damage due to a sudden over-pressurised event during a processing operation. The vessel was deemed unsafe by Insurance Underwriters. For reinstatement, it was requested that an Engineering Critical Assessment to API 579 Level 3 or BS7910 Level 3 was conducted.

Various NDT tests showed no cracking due to incident. Digital Scanning of the damage was carried out for Finite Element Analysis modelling. Stress analysis of the vessel was conducted to determine stress hot spots. Full Level 3 was conducted to BS7910 using different material properties & semi-elliptical crack inputs & showed different scenarios for the FAD (Failure Assessment Diagram). Following this analysis, fatigue crack assessment was conducted using the Paris Law which yielded various fatigue life for the different crack dimensions & material properties. The analyses showed an operational life would range from 100 to 25 months due to crack growth.