Development of Non-Destructive In-Service Detection of Damage Severity for Pipeline Steel Inspection

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January 27, 2012
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Advanced Residual Stress Sensors To Determine Severity Of Steel Pipeline Mechanical Damage
It is well known that mechanical damage is the leading cause of steel pipeline failures. It is less well known, but equally true, that residual stress plays a critical role in the cracking and failure of pipelines. With DOT SBIR funding G2MT has developed an advanced sensor for measuring the residual stress (strain) levels in 3-D on mechanically damaged steel pipelines. The residual stress assessment technology provides a long-awaited replacement for caliper testing of pipeline mechanical damage to improve fitness-for-service assessments and pipeline integrity through in-situ nondestructive analysis.
Residual Stress Dents are among the most common forms of pipeline mechanical damage, yet under current regulations every dent found must be analyzed using antiquated caliper-based measurements to determine if the dent should be repaired or removed. The regulations result in heavy costs to pipeline operators but are ineffective at reducing pipeline failures because they miss the root cause of the problem. Similarly, wrinkle bends, are an intentional mechanical deformation commonly used in pipeline construction practice for many decades. Wrinkle bends that were thought to be safe are now increasingly susceptible to fatigue and aging especially since the aging U.S. pipeline infrastructure has operated beyond its original designed life.  A method to measure the residual stress in these mechanically damaged regions has long been sought after by the pipeline industry.
SBIR Success Electromagnetic sensors were developed to measure 3-D quantified residual stress levels in mechanically damaged steel pipelines. The residual stress levels associated with damage vary as a function of depth into the steel. To determine the mechanical integrity of the steel pipeline, it is most beneficial to know the residual stress levels associated with the mechanical damage at specific depths beneath the surface including the internal surface of the pipe (measured from the outside). When different types of mechanical damage are inspected on a pipeline, the damaged locations with residual stress levels above the threshold stress level and therefore highest priority can be pinpointed and repaired to maintain the integrity of the steel pipeline. G2MT demonstrated the portable scanning 3-D residual stress measurement capability and confirmed its accuracy in pipeline dents by comparing with neutron diffraction.  G2MT characterized 8 ‘identical’ wrinkle bends on a section of steel pipeline showing dramatic variations in through-thickness residual stress levels and therefore damage severity, while advanced caliper results on the same 8 ‘identical’ wrinkle bends show no measurable differences between the wrinkle bends and therefore no difference in damage severity.  Advanced three-dimensional residual stress sensors are the new paradigm for non-destructive assessment of pipelines (and other components) to improve and monitor pipeline integrity.  
Commercialization Path Future activities include: (1) Further refinement of residual stress calibration procedures to increase accuracy and (2) ruggedize equipment through collaborations with equipment makers, and (3) partner with service companies to begin in-field testing with new ruggedized equipment and begin assessment practices.
About G2MT G2MT was founded in 2009 to provide the next-generation of advanced non-destructive materials characterization technologies that will change the way materials are made, used, and maintained. 

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