Technical ILI System – Verification Versus Validation Based on Sound Engineering Practice Solely on Industry Recognized and Standardized Methodology

Abstract For the qualification of technical In-Line Inspection (ILI) systems for pipeline inspections, API 1163 standard allows two different approaches to demonstrate the system’s performance; verification or validation, based on tests or simulations and validation using historical data, i.e. verified field measurements from excavations. Verification ensures evidence of the entire performance specification in terms of Probability of Detection (POD), Probability of Identification (POI) and sizing capability, while validation defends the performance specification on a sample basis respectively derives individual aspects of the as-run performance. Successful verification of the ILI system should be a prerequisite for carrying out the validation. Usually, verification takes place on test fields or in laboratories under controlled conditions in order to test the essential variables and thus to prove every aspect of the performance specification in regards to POD, POI and sizing capability. API 1163 provides statistical methods for the practical implementation of measurement performance qualification, but these methods are described solely for the validation approach. This paper closes the gap by adapting industry recognized and standardized statistical methodologies to the problem of verifying technical ILI systems in terms of detection and sizing and comparing these methods to the ones, described in API 1163, proposed for the system’s validation. Specifically, these methods for verifying ILI performance are the 29/29 method with Clopper-Pearson for POD and the Expanded Measurement Uncertainty method for sizing in accordance with GUM.