Abstract
This paper presents a statistical extreme value analysis (EVA) method for assessment of the minimum remaining thickness of tubes in industrial heat exchangers, including air-cooled heat exchangers and shell-and-tube heat exchangers. Five test cases are used to evaluate the effectiveness of the EVA method developed in this work. In each case, real inspection data from heat exchangers in petroleum refinery and petrochemical plant are analyzed, and the results discussed. The effectiveness of the EVA method is then evaluated per the Inspection Effectiveness definition used by American Petroleum Institute (API) for Risk-Based Inspection (RBI), so that the EVA method and results can be easily incorporated in API RBI assessment. It is found through these test cases that the most ideal sample size seems to be 20–30 tubes, regardless of the number of tubes in the heat exchanger. At that sample size, A, B, C and D levels of API RBI inspection effectiveness can be achieved by using the lower bound value of the 99%, 95%, 90%, and 80% confidence intervals, respectively.
Published Version
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