Challenges to Manage Short But Deep Crack-Like Features
Authors: Yu Mengshan , Aulin Axel , Vorontsov Vitaly , Lamborn Lyndon , Aymerich Jordi , Guajardo Rogelio 
Published: December 2024

A near through-wall axial crack flaw was identified in the 1950s vintage flash welded 24-inch liquid pipeline in the ditch. This feature was further assessed using Magnetic Particle Inspection (MPI), encoded Phased Array Ultrasonic Testing (PAUT) and Time of Flight Diffraction (TOFD). It was identified to be a stacked flaw with a total axial length of 23 mm, including external crack-like with 5.7 mm depth and internal lack of fusion (LOF) with 2.5 mm depth making it 88% deep based on local wall thickness of the weld. Because of its significant depth, this feature was extracted by coupon cutout for further examination. Some other operators have also discovered short but deep crack features (penetrators in vintage pipes) in operating pipelines. These features can be either through-wall or near through-wall and are challenging to detect and size with in-line inspection (ILI) and non-destructive examination (NDE) technologies. These short but deep penetrators are typically a leak threat but the consequences of a leak in High Consequences Area (HCA) can be significant depending on the location.

Before proceeding with destructive testing, Enbridge took proactive steps to integrate additional NDE advanced inspection methods for the purpose of validating sizing accuracy and overall performance. This comprehensive initiative included inviting four additional NDE vendors to participate in sizing activities. Additional advanced techniques such as Eddy Current Array (ECA) technology and Full Matrix Capture (FMC) utilizing Phase Coherence Imaging (PCI) were incorporated. The primary objective was to ensure sizing accuracy between ILI tools, currently adopted in-ditch NDE methods, and lesser-known advanced NDE methods. All additional NDE vendors, apart from the field inspection, were invited to perform sizing activities in their facilities.

This paper will show a detailed comparison in feature sizing across all NDE vendors and their results. The paper will include screen captures of the data acquisition, sizing methodologies utilized, and a comparison between TOFD and PAUT amplitude sizing and the true macro data taken from the cross-sectioning.

In a collaborative project with NDT Global, a new Phase Array ILI crack tool was developed to detect and characterize the cracking anomalies in 24/26″ diameter 1950 vintage flash weld pipe in the 2017–2022 timeframe. Though the development did not specifically target short but deep crack-like features, the multi-angle and multi-measurement ultrasonic technology may have the additional advantage/capability to detect and size these short and deep features as they are below the detection and sizing thresholds of many conventional crack ILIs.

This study provides a guideline on how to work with ILI vendors to leverage the acquired data from both ILI and field results to implement non-standard analysis procedures to address these outside-specification features. The main goal is to use the ILI and NDE data to improve the detection and sizing of short and deep crack-like features which may threaten pipelines.