• Conducted Level 3 Fitness for Service Assessment for tank due to metal loss and shell distortions from inspections.

• Performed wall thickness measurements and 3D scan, revealing shell courses below required design thickness and potential further reduction due to corrosion.

• 3D scan also showed geometric out-of-roundness from fabrication tolerances.

• Used API 579-1 / ASME FFS-1 2021 Part 4 Level 3 General Metal Loss assessment to evaluate minimum required thickness for continued operation.

• Applied minimum measured thickness per shell strake orientation (North, East, South, West) to scanned geometry for integrity assessment.

The remaining life could not be determined due to some shell sections being below the minimum design thickness. To prevent future corrosion, mitigation options such as protective coatings should be applied to all wetted surfaces of the shell and the roof. The tank is deemed fit for service with an operating liquid level of 8290 mm, provided the recommendations are implemented. Regular inspections must be conducted to ensure that the thickness remains above the minimum allowed values in both the general and local regions of the tank shell. Additionally, operation under vacuum conditions should be avoided; if it occurs, the pressures on the shell should not exceed 250 Pa.

• Performed mechanical design calculations for three surge tank sizes (120 m³, 260 m³, and 500 m³) according to API 650 and API 620.

• Managed engineering drawings as discipline manager, ensuring all weld details complied with relevant codes.

• Verified structural integrity of tanks during transport and lifting using linear static Finite Element Analysis (FEA).

• Utilized 3D shell finite element model with mesh refinement applied to critical areas for accurate stress results.

• Evaluated stress results in accordance with ASME BPVC Sec. VIII Div. 2 Part 5 for primary and secondary stresses.

• Applied Sound Engineering Practice (SEP) to evaluate static stress results for saddles during transportation.

The analysis confirms that all stress levels for the saddles and tank are acceptable. All the Surge Tanks can be safely transported and lifted if the outlined measures are followed. Lining the saddles with a non-slip material is essential, and both saddles should be securely tied to the truck bed, with the tank firmly attached.