Corrosion Depth Measurement for Bottom Plate of Fuel Storage Tanks and Results of Ultrasonic Thickness Inspection

Abstract

A corrosion inspection for bottom plate of fuel storage tanks using ultrasonic thickness gauge (UT) must be performed regularly as provided by law. In order to investigate reliability of UT, corrosion depth of samples cut from bottom plates measured by laser displacement meter (LDM) was compared with results of UT. As a result, it was indicated that UT was enough to know mean corrosion depth, however maximum corrosion depth estimated statistically from corrosion depth measured by LDM was 1-1.5times larger than that from UT. It became clear that the estimated maximum corrosion depth would be smaller than the actual value when UT is used in its estimation.