Objective With increasingly stringent emission requirements for environmental protection, more floating roof tanks are being equipped with full-contact floating roofs and sealing structures with high compensation capacity. However, these floating roofs are subjected to complex stress conditions due to the combined effects of factors such as rim sealing and tank wall deformation. This situation leads to increasing incidents such as damage and deck jamming. To address these issues, studying the mechanical characteristics of floating roofs under the influence of elastic sealing systems with high compensation capacity is crucial for ensuring their safe operation.
Methods An experimental platform for evaluating the sealing efficiency of storage tanks was designed and constructed. This platform was subsequently used to assess forces exerted by elastic sealing structures with high compensation capacity on floating roofs with various annular gaps. Utilizing finite element methodology, a finite element analysis model was established to simulate double-deck floating roofs for 5×104 m3 storage tanks. This model was employed to study the stress and deformation distribution characteristics of floating roofs under normal operation, tank wall deformation, and extreme deck jamming conditions. Further analysis focused on identifying weak areas within these roofs due to stress concentration under various conditions.
Results As the annular gaps narrowed, the sealing structure with high compensation capacity became increasingly compressed, resulting in progressively upward-moving contact areas with the tank wall and a significant increase in the friction force acting on the floating roof. During normal operation, the maximum Mises stress was identified within the truss structure, with stress concentration occurring near the connection between the side beam and the stiffener of the bottom plate. Elliptical or localized deformation in the tank wall led to expanded deformation in the floating roof area, where localized jamming occurred. Under similar average friction forces acting on the floating roof, localized deformation in the storage tank was more likely to cause deck jamming and instability of the floating roof than elliptical deformation. Under deck jamming conditions, the maximum Mises stress experienced by the floating roof increased significantly, and under extreme deck jamming conditions, the stress exceeded the allowable limit, resulting in localized strength failure.
Conclusion For tanks with wall deformation, mechanical performance evaluation should be carried out on their floating roofs to ensure safe tank operation before installing additional high-efficiency seals or undertaking sealing renovations.
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