Nondestructive Pipeline Stress Analysis


G2MT is meeting the challenges of our aging pipeline infrastructure head-on with advanced tools for rapidly determining the real integrity of pipelines. Many years of metallurgical research have shown that stress is the most important influence on the potential for failure of a damaged area. By mapping the stresses, it is possible to track stress changes over time and even mitigate future problems.
The first of these tools, the eStress residual stress analysis system, provides real-time analysis of stresses in mechanical damage regions to dramatically improved pipeline integrity management.
The eStress Residual Stress Assessment System
G2MT’s revolutionary new eStresssystem is the first commercial system for residual stress assessment of pipeline damage. eStress was developed through an SBIR award from the US Department of Transportation. This next-generation pipeline inspection tool quantitatively measures residual stresses around pipeline damage areas to determine the susceptibility to failure. The eStress system provides deep insight into the nature and severity of the stresses near dents and damage regions.
The eStress nondestructive testing technologies are coupled with advanced modeling techniques to dramatically improve the capability to not just determine the difference between good and bad amounts of stress but to quantitatively measure the local stress and map the stress around the entire area.
Our Aging Infrastructure
Preliminary NDT of Pipelines before shipping from a pipe storage facility as part of a materials condition monitoring system by G2MTThe domestic and global pipeline infrastructures are aging, and in many cases well beyond the original design life. As these pipeline systems age, the steel they are built from ages and accumulates fatigue damage, hydrogen, and strains that can ultimately lead to failures. The largest single cause of pipeline failures is mechanical damage, usually from something impacting or pushing into the pipe. Often this results in  immediate and catastrophic failures, but when the damage is not severe enough for this to happen, it can take many years of accumulated strains and aging before the damaged region becomes dangerous. Finding and removing these danger areas is a critical focus of pipeline inspection programs, but current technologies are unable to evaluate stresses in pipelines.
In fact, dents and damaged regions in pipelines form one of the primary areas of concern for pipeline failures. Mechanical damage by third-parties, seismic activity, damage during installation, errors during welding, and many other sources can put residual stresses into pipelines and increase their susceptibility to failure. In fact, Residual stress is the silent killer of many pipelines. It can be introduced in so many ways but may not result in a failure for many years down the road. The reason for the danger is that regions of high residual stress actively draw soluble hydrogen atoms into themselves, ultimately resulting in extremely high levels of hydrogen that then contribute to hydrogen embrittlement. When assisted by the everyday fatigue that pipelines regularly experience, the results can be catastrophic.
The best existing technology for pipeline inspection combines both interior (in-line inspection via a “smart pig) and exterior pipeline inspection methods that are used following the pigging run. The exterior inspections usually require the pipeline to be uncovered and the coating removed for inspection of each pigging indication above a specified size; anything larger than a selected percentage of the pipeline diameter may be chosen for inspection. Magnetic particle inspection, ultrasound, and automated ultrasound testing (AUT) are typically used to assess the severity of the damage, and damage regions exceeding the contractor’s selected specification or the national codes and standards are required to be removed or repaired. The most common specification for dent removal is determined using a caliper gauge, and dents above six degrees, for example, are all removed or repaired. This rather arbitrary number is intended to be conservative but ultimately pipeline operators regularly report that the cracks and failures simply move to other regions that passed the existing dent testing standards.
The Future of Pipeline Testing
The eStress residual stress system is being demonstrated to evaluate the damage severity through the coating on coated steels as regulated by Pipeline Safety Regulations 49 CFR Parts 190-195. This eStress system dramatically improves pipeline integrity assessment and reduce the number of unnecessary pipeline replacement and removal actives.

 

Other Nondestructive Residual Stress Assessment Tools
Residual stress assessment is of interest to many industries and applications. Is yours one?