Stress And Reliability Analysis Of Corrosion Defects Of Crude Oil Storage Tank At 36-1 Terminal In Suizhong

Tank's structure is thin wall and variable wall thickness. The tank is an essential facility in Petrochemical industry and plays an important role in the development of the national economy. Corrosion defects of tank will lead to change stress state. Once the tank fail, it will lead to catastrophic accidents such as fire and explosion.SZ36-1 terminal crude oil tanks have varying degrees of corrosion, it will affect the safe operation of the tank with its development. For the characteristics of corrosion defects of tank, the finite element model of tank which contain the corrosion defects and the reliability calculation model is established to calculate the reliability and failure probability of tank which contains the different depth of corrosion defects. Reasonable safety management measures are put forward.Specific research contents and main results are as follows:(1) Collected tank's information of design, construction, operation and maintenance. Corrosion defects are semi-cylindrical recess.(2) Based on the Von-Mises stress grid-independent analysis, a dimensional finite element model with single and multiple groove corrosion defects is established. Its results compare with the results of tank wall radial displacement theory. The model's correctness is verified.(3) According to the current and development depth, arc length, width and position of corrosion defects, the stress distribution law and critical depth of corrosion defects are analyzed. Considering the interaction of defects in axially adjacent, the critical impact spacing by different arc and depth of corrosion defects are determined. And the basis of single corrosion defects processing is proposed. Aiming at the size characteristics of corrosion defects, it determin the impact spacing of the ring adjacent defects.(4) Considering the tank hydrostatic pressure loads, corrosion thinning reliability calculation model of tank to characterize by the yield strength of steel, the corrosion thinning of tank wall, hoop stress and axial stress is established. The distribution of parameters, coefficient of variation and standard deviation are determined reasonably. Then reliability computer procedure is programed.(5) Using the reliability calculation model and procedure to comprehensive analysis the reliability size of SZ36-1 tank wall under different corrosion thinning. Based on API579,10-3 is determined the tank corrosion failure probability criterion.Under current corrosion defect, the reliability index of tank is 5.89,and the critical failure probability corresponding corrosion depth is 13mm.(6) Based on the tank corrosion thinning failure risk matrix, failure probability of corrosion and security impact area, the risk rating of the tank are determined'(M)'and'(MH)' with different wind speeds. Appropriate security compensation measures and corrosion testing policy are proposed.