Investigate Performance of Current In-Line Inspection Technologies for Dents and Dent Associated With Metal Loss Damage Detection

Integrity management of dent and dent associated with metal loss requires knowledge of in-line inspection (ILI) technologies, government regulations and industry codes, prescriptive requirements, and most importantly assessment models to estimate severity of the mechanical damage. The assessment models have greatly relied on the assumed capabilities of current ILI technologies to detect, discriminate and size the mechanical damage. Therefore, an investigation of the current ILI technologies and validation of their capabilities are practically important. In this paper, the current status of ILI technologies for dent and dent with metal loss is reviewed. Validation data provided by ILI inspection vendors and pipeline operators are analyzed in terms of probability of detection (POD), probability of identification (POI), probability of false call (POFC), and sizing accuracy using binomial probability distribution and confidence interval methods. Linear regression analysis is also performed to determine sizing error bands. High resolution pull test data validated with LaserScan 3-D mapping technology is used to demonstrate a better evaluation of ILI performance with minimized in-ditch measurement errors and the effect of change in dent geometry and dimension due to re-bounding and re-rounding. Issues associated with field measurement and improvement are discussed.