Application of extreme value theory in the corrosion depth statistics of storage tank bottom

To get the corrosion condition of tank bottom accurately,master the statistical rule of maximal corrosion depth of the tank bottom in long-term service,and evaluate the residual service life of storage tank more effectively,the generalized extreme value(GEV) distribution was adopted as statistical model for the corrosion depth of the tank bottom,and the statistical law of the corrosion depth was analyzed.L-moments method was used for calculating the values of the parameters.The method was used to three tank bottoms in one unite plants from Shengli Oilfield,and the results showed that the maximum corrosion depth accorded with the GEV distribution Ⅲ(Weibull distribution),which got though the Kolmogorov inspection.The GEV distribution Ⅲ can fit the statistical rule of maximum corrosion depth better than that of the GEV distributionⅠ.