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Lightning exposure of oil tanks with changing roof position
Published in Vladimir Litvinenko, Advances in Raw Material Industries for Sustainable Development Goals, 2020
A number of lightning-induced floating roof tank and facility fire incidents, and equipment damage have occurred across the globe resulting in equipment and facility destruction, expensive repair cost, loss of production time, and man-hours expended on incident reviews. An external floating roof tank has a floating roof that moves with the level of the liquid within the tank in order to limit the vapor space above the liquid crude oil. This helps to reduce the evaporation of light oil fractions and petroleum products by 90-98% (Kulikov & Chekardovskiy, 2018). The roofs are made of pontoons which aid the buoyancy of the roof. The gap between the floating roof and the tank shell is covered by rim seals which prevent crude oil from leaking onto the roof. Also, it limits vapor escape from the shell-roof gap. The rim seal region of a floating roof tank is the most likely starting point for a lightning-induced tank fire during a thunderstorm (Chang & Lin, 2006, Adekitan & Rock, 2019a).
Large eddy simulations of wind loads on an external floating-roof tank
Published in Engineering Applications of Computational Fluid Mechanics, 2020
Xu Sun, Wenxin Li, Qiyu Huang, Jing Zhang, Chaochao Sun
For the purpose of energy security, a great number of state oil strategic reserves have been built worldwide. In aboveground oil storage reserves, external floating-roof tanks with capacities above 105m3 are usually used to store the crude oil. As the name implies, an external floating-roof tank is mainly constructed by a metal cylindrical shell and a steel floating roof. Compared with the fixed roof tanks used widely in stations of oil fields and oil pipelines, the cylindrical shell of external floating-roof tanks has much larger radius to thickness ratio, which is usually in an order of 1000∼2000. As a typical thin-walled structure, the external floating-roof tanks, especially for those located in the coastal area, usually experience the buckling problem under wind load. In strong winds such as typhoon and tornado, buckling-induced deflection of the cylindrical shell might incline significantly the floating roof or even destroy the whole tank (Godoy, 2007; Portela, Virella, & Godoy, 2006). To reveal the buckling characteristics of an external floating-roof oil storage tank, investigating first the features of wind load, as well as the unsteady flow around it, is of vital importance.