Axially stress corrosion cracking (SCC) has been a known threat for many years and has been found in pipelines that are susceptible based on material, stress and environment and especially prevalent in high pressure gas lines. For axial SCC, the primary stress results from internal pressure. In more recent years, circumferential SCC (CSCC) has been found in both gas and liquid pipelines where other stresses - axial, bending and combined - are primary. CSCC is a collective term to describe SCC that is not classically axially orientated. CSCC was previously thought to be as a result of geohazards, such as land movement, where the pipeline is subject to adverse bending strains. However, in more recent years, CSCC has been found in pipelines with little to no apparent bending strain. Moreover, the cause has been attributed to axial strains resulting from construction/installation. In-line inspection (ILI) tools such as ultrasonic crack detection (UTCD) and electromagnetic acoustic transducer (EMAT) are designed to detect and size crack anomalies inclusive of SCC. However, this technology has been focused on axial SCC and thus CSCC has not, historically, been a primary mission for ILI. To manage this threat, several operators have turned to magnetic based combination tools incorporating inertial mapping units (IMUs) to combine data sets to assess different signals including axial magnetic flux leakage (MFL), spiral MFL, low field MFL (LFM), high resolution caliper and internal/external diameter (IDOD) sensors which when combined can identify and characterize CSCC and, on the flip side, identify when it is not CSCC. This paper highlights the use of an existing commercially available ILI tool without any modifications to look for CSCC by using the multiple data streams. The paper will also present the development of the CSCC model, its application to real pipeline data and some field data feedback.
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