Maximum allowable operating pressure (MAOP) verification alternatives to a hydrotest
GTI’s hydrotesting alternatives program identified and ultimately validated technologies that can provide an inspection that is equivalent to—or superior than—a hydrotest to obtain regulatory acceptance.
With Operations Technology Development (OTD) funding, GTI developed and deployed a critical flaw and critical wall loss calculator that can help ensure pipeline safety and provide operators with significant cost savings in complying with new regulations. The model allows operators to determine if an inspection technology could detect a crack-like flaw and/or wall loss that would fail a pressure/hydrotest at a particular pressure. It helps enable operators to use Engineering Critical Assessment (ECA) in lieu of a hydrotest which requires shutdown and water injection.
An analytical tool has been developed and is available for industry use. It will help pipeline operators use inspection techniques as alternatives to hydrostatic testing when looking to address Integrity Verification Process (IVP) and ECA regulations and requirements.
A new effort will develop an integrated software solution combining leak rupture boundary, advanced crack propagation, alternatives to a hydrotest, and other tools to assist operators with pending MAOP and materials verification requirements. The project will provide a basis/process to justify use of in line inspection (ILI) and other inspection technology as an alternative to hydrotest, and support use of pipe surface-based non-destructive measurements and system sampling to establish materials verification.
A pilot project conducting IVP and ECA efforts on actual transmission pipelines using electro-magnetic acoustic technology (EMAT), circumferential magnetic flux leakage (CMFL), an ILI pipe grade sensor, and in-the-ditch non-destructive evaluation (NDE) for material properties will facilitate development of a technically rigorous process and provide important data for the software framework.
In a separate project, GTI researchers will provide a technically justifiable, augmented method to retain Direct Assessment (DA) as an acceptable integrity assessment process for pipeline segments. Looking at External Corrosion Direct Assessment (ECDA) as a first step, it will focus on challenging situations like vintage pipe and others that cannot be assessed by pressure or ILI testing.
A pre-prototype electromagnetic acoustic transducer (EMAT) sensor to assess small-diameter and unpiggable distribution and transmission pipelines was successfully developed with OTD and the U.S. Department of Transportation (DOT) Transportation’s Pipeline Hazardous Materials and Safety Administration (PHMSA) funding. This will enable pipeline operators to identify defects including cracks that are traditionally difficult to find and assess, improving system integrity and public safety.
The field-ready prototype has completed tests of various defects and conditions in controlled, unpressurized field environments. The next step is field testing and validation with operators leading to a field demonstration on a live gas line and moving the technology toward commercialization. A license has been signed with a platform provider.
Validating models to characterize material properties of in-service pipelines
As part of validating non-destructive tools for surface to bulk correlations of yield strength, toughness, and chemistry, GTI and partners MMT, Frontics, and ASU will assess accuracy, efficiency, and cost-effectiveness of alternative tools for material property confirmation. Pipeline safety, compliance, and integrity assessment programs will benefit from material and MAOP validation techniques that do not require a line to be taken out of service or have sections cut out for analysis.
With funding from DOT PHMSA and OTD, the project team will develop and validate models that account for pipe material thermo-mechanical process variations and through-wall variability of material, mechanical, and chemical properties. Test results and associated analysis will be used to develop correlations between surface properties and bulk material properties. The results will directly support the choice of non-destructive surface testing as part of the DOT PHMSA pending Integrity Verification Process (IVP) and assist operators in meeting requirements to backfill their material property records for grandfathered pipeline segments.
A comprehensive database of existing and related surface and bulk mechanical, physical, and chemical properties on a robust pipe set, and summary documentation of the pipeline samples will be created. A testing matrix will be developed, and tests will be executed and correlated with full-wall and bulk tests of the same pipeline specimens. Results will be inputted into the project database.
Data will be analyzed, and a model developed and optimized. A final report will include the final database, technology metrics summary, implementation guidance for models to determine bulk properties from non-destructive surface testing, and a Bayesian network model to allow continued model updating without additional regression analysis.
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