I was speaking with a pipeline operator a while back who had just completed an anomaly dig that cost upwards of 1 million dollars. The reason for the dig was to investigate a metal loss anomaly reported by a recent In-Line Inspection (ILI). The pipeline company’s business rules, in the form of their Integrity Management Program (IMP), dictate that metal loss anomalies meeting certain depth or safe pressure calculations must be dug up and repaired. With that kind of money at stake for a dig, or any dig for that matter, the focus quickly turns to how accurate the ILI vendor made the call. Here we’ll look a little more under the hood to understand the genesis and inherent variability of ILI reported features.
In my previous blog Boxes: The Origin of Your Pipe Listing, I covered some of the basics of where features reported by ILI come from. To recap, the ILI tool does not detect anomalies. It records data which is processed and interpreted by software and human beings. Pipeline features and anomalies are then annotated with boxes which contain attributes describing the feature. Each box becomes a reported item in the resultant pipe tally or report.
In a perfect world, these ILI-generated features will match exactly the features expected on the pipe. Of course, we don’t live in a perfect world and real money is at stake adding to the pressure on ILI vendors and operators to get it right.