A large-diameter seawater dump caisson, constructed from Glass Reinforced Epoxy (GRE), required a comprehensive strength assessment. This caisson featured five nozzles, with one positioned in the blind flange at its top, all subject to external piping loads. The primary objective was to determine the necessary reinforcement for the intersection of the caisson and the nozzles. Additionally, it was essential to evaluate potential modifications to the laminations between the spools due to the bending loads applied to the caisson body.
Analysis
The assessment was performed using the Finite Element Package FE/Pipe to evaluate the individual nozzle/caisson intersections. Two-dimensional shell models were utilized to determine the required wall thickness and laminates to accommodate the applied loads. The proposed lamination geometries adhered to the manufacturer’s design guidelines to ensure field implementation. For a global assessment of the entire caisson, the pipe modeling package CAESAR II was employed to determine the loading on the laminate joints between the spools and the restraint points. The caisson stresses were evaluated against a long-term allowable stress envelope, ensuring compliance with the ISO 14692 standard.
Results
The study identified the necessary modifications to conform to the ISO 14692 standard. DRG coordinated with the manufacturer to confirm the feasibility of the proposed geometries and thicknesses in the field. The laminate joint geometries between the spools were also verified to ensure they were of sufficient length and thickness.
“Joint lamination thicknesses were determined for this bespoke product to ensure compliance with the design code.”
During transportation, the caisson was designed to lie in a horizontal position, with support locations differing from those used in operation. An additional check confirmed that the caisson conformed to the design code during transportation.
This thorough finite element analysis ensured the strength and durability of the GRE dump caisson, meeting all necessary standards and operational requirements.
