Safety Analysis Of Interacting Defects For Large Storage Oil Tanks On The Offshore Platform

The crude oil storage tank on marine platform is the typical pressure vessel equipment in marine oil production process,the safety condition of crude oil storage tank can affect the production and economic benefits of the platform.Crude oil storage tank can be corroded easily under the combined effects of corrosion defects in the production environment and the complexity of the marine environment loads.If the defects were not discovered and treated in time, it may cause defects in the structure of crude oil storage tank or even perforation, result in oil leakage. Once the storage structure is damaged, it will do great harm to the surrounding marine atmosphere, even cause tragic accident and threatens the security of the staff working on the platform.Therefore, in order to make the crude oil storage tanks on the marine platform safe and reliable, it is very necessary to make safety assessment on storage tank defects in the study of its damage behaviors.This paper studies the defect assessment of pressure equipment in service for crude oil storage tank with defects on marine platform, and mainly finish the following tasks:(1) Laid in bad production conditions and exposed in the marine atmospheric environment of high humidity and high salinity all the year, it is easy to get corrosive defects.The existing complicated atmosphere load such as sea wind, current and earth quake all accelerate the expansion of defects. So in this thesis, we identify various loads and corrosion factors on the platform first, through studying we analysis the influence of environmental factors on the offshore platform.(2) The characterization methods during the safety assessment for various defects(such as cracks, pits,etc.)of crude oil storage tanks on the marine platform have been analyzed, the combined characterization methods and the influences among defects have been mainly studied.(3)Different combinations of environmental loads on the platform have been analyzed,by using finite element software the conventional condition, extreme wind condition and seismic condition of crude oil tanks on offshore platform have been simulated,and the simulation results of stress have been linearizated for defect assessment calculations.The combined characterization methods in Safety Assessment for In-Service Pressure Vessels Containing Defects have been referenced,the variation of stress intensity factors under different combinations of multi-defectcharacterization approach in the conventional condition have been analyzed,a characterization method for three or more than three cracks has been proposed.(4)Taking crude oil storage tanks with defects on the marine platform for instance and adopting the regular assessment methods in GB/T19624-2004 Safety Assessment for In-Service Pressure Vessels Containing Defects, safety assessments for crude oil storage tanks with different defects in conditions of extreme winds and earthquakes have been carried out and the safety assessment conclusions have been got.