Fitness For Service Assessment (FFSA) of a corroded Pressure Vessel

Our main focus was to:

1. Review the attached pipework and using the ROHR2 Pipe Stress Analysis software, determine nozzle and pipe support loads applied to the vessel.
2. Verify the construction of the vessel within the PVElite pressure vessel assessment software to confirm missing technical information.
3. Use MSC APEX software to build a comprehensive FEA model of the vessel, including modelling of the corroded areas close to the pipe support.
4. Perform the L3 FFSA using MSC MARC software.

In order to gather the information required to estimate the stresses over the corroded areas, our team performed numerous sensitivity studies with the information that was available.

ROHR2 was used to conduct pipe stress analysis to accurately estimate the loads transferred on to the vessel shell due to sustained and thermal expansion effects of the pipework.

Then, PV Elite was used to model the vessel and its major attachments, to provide information such as the minimum design code thickness and shell stresses under various load cases, such as deadweight, internal pressure and wind loads calculated from BS6399.

Sensitivity studies were then performed in MSC APEX to quickly assess which key features should be considered in the full FEA assessment model. The assessment itself was performed in MSC MARC, which allowed for both linear and non-linear methods to be employed to calculate the stresses on and around the defect areas. We also investigated the levels of future corrosion which may be permissible before remedial action was required.