Development of an FFS Study for a Nitrogenated Water Storage Tank

Fitness for Service study for a 22.5 m diameter, 13 m nominal height storage tank used for nitrogenated water, prompted by severe corrosion related deterioration found in the tank bottom during a May 2024 inspection. The assessment focused on the perimeter bottom plates supported on the concrete ring wall, the area with the highest corrosion and therefore the lowest remaining life. Using FEA with API 653 and API 650 Appendix P criteria, linearized Von Mises stresses were evaluated at the most critical corroded locations. Results confirmed that the tank’s mechanical integrity would not be significantly compromised over an additional 1.5 year operating period without immediate repairs, allowing the client to safely defer maintenance while maintaining full confidence in the structural integrity of the equipment.