Perfecting Data Inputs for Accurate Crack Assessment and Better Integrity Management

Project Overview

• Performed an engineering critical assessment with materials testing and fracture mechanics analysis to address defects identified by an ILI run.

Project Impact

• Reduced the scope of required repairs using engineering analysis.
• Saved costs while effectively maintaining the integrity of the pipeline system.
• Improved materials testing data on assets for future integrity analyses.

Data is only as meaningful as the analysis behind it. When a major pipeline operator in the Midwest received data from its ILI vendor identifying approximately 1,400 different features, the operator needed additional analyses to discern the best path forward after the inspection. In the end, the operator greatly reduced the number of required digs, acquired more materials testing data on the pipeline than it previously had, and implemented an optimized fitness-for-service analysis methodology with improved data inputs.

Large Number of Features Identified from ILI

The operator received a UTCD (ultrasonic crack detection tool) ILI report from a vendor identifying a large number of features, but the vendor was unable to differentiate between blunt, non-injurious features, and sharp, crack-like features that posed a real threat. Because of the lack of differentiation, a conservative assumption was made initially to consider all identified features as potentially injurious. However, the resulting dig plan to address all 1,400 features was economically infeasible and we were confident based on our experience with the pipeline’s condition that many of those proposed digs were unnecessary.

Engineering Critical Analysis Required to Determine Path Forward

Our first step in supporting the operator was to analyze the maximum allowable operating pressure and determine if the criteria used to identify features were accurate for the pipeline in question. After confirming MOP, we updated the methodology for the fitness-for-service analysis to determine the threat of the ILI features more accurately. Previously, the analysis had used a deterministic model dependent on Charpy V-notch tests to measure toughness. The model was updated to use fracture toughness inputs. In order to facilitate the change in measurement inputs, we performed materials testing on existing specimens from the line and planned additional materials testing and feature analysis. Finally, a hydrotest was performed to validate the analysis. The test confirmed that the original criteria for feature identification were conservative, resulting in the large scope of identified features for inspection and repair.

Better Integrity Management Outcomes and Improved Data Inputs

After the project, the operator not only had a better understanding of the features identified by the ILI, but the materials testing data and the deterministic crack analysis provided further insight into the integrity and safety of the pipeline. Several of the client’s integrity management analyses were improved and optimized to better serve the system’s integrity using the data confirmation and validation made possible by the field and lab testing. And that 1,400-feature repair plan? It was reduced to include only the features that were an active and imminent threat to the pipeline, allowing the operator’s investment in digs and repairs to provide an optimal integrity return.