Method proposed for calibrating MFL, UT ILI tools

A new statistical method has been developed and successfully tested for calibrating magnetic-flux-leakage and ultrasonic in-line inspection (ILI tools from field verifications. In contrast to the methods so far available in the literature, the method proposed here can estimate the measurement errors of the ILI and field tools for both constant and nonconstant bias error-in-variables (EIV) models. Following the results obtained in this work, the optimum number of field verifications to be conducted is about 30. For this two-tools-one-measurement-each case, the most accurate results are obtained when both tools show similar precision.