Pipeline operators use different approaches, often in combination to ensure the safe operation of an asset. Historically, hydrotesting is the most accepted methodology for assessing critical flaws in a pipeline system, basically by stressing the pipeline above the standard operating limits. By design, a release during this test removes a critical flaw from the system. There are significant draw backs to this type of assessment. Such drawbacks include high costs of implementation, feature growth, previously blunt defects sharpening and system downtime.
Driven by the operator to investigate alternative approaches, a consortium of 4 parties formed to develop and validate an alternative and enhanced solution.
The research and execution of the project was structured in four (4) different phases.
- Phase I – Determine which crack morphologies are challenging to ILI technology in terms of detection and depth determination and test initial improvements to ILI technology. This included loop testing improved crack detection ILI robots and destructive assessment with pipe samples to identify gaps in ILI technology and analysis techniques.
- Phase II – Assess vendor improved ILI technology on the operating pipelines using advanced in the ditch non-destructive evaluation (NDE) methods and destructive testing of pipe samples from the pipelines. Identify the additional improvements if necessary.
- Phase III – Implement specific improvements to ILI technology that are completed based on Step I and II results. Validate the new ILI platform on the specific pipeline.
- Phase IV – Determination whether the new ILI platform can provide equivalent pipe seam system reliability to hydrostatic testing. A probabilistic approach will be used that would account for the expected statistical distribution of pipe properties, fatigue crack growth rates, position along the pipeline, and flaw sizes.
This paper is a summary of the research and work for this ILI In Lieu of Hydrotest initiative.