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PRCI Completes Full-scale Testing Milestone for Mechanical Damage Program
In 2008, PRCI initiated a significant program to establish a detailed experimental database to support the development and validation of improved burst and fatigue strength models for assessing the interaction of mechanical damage with secondary features (gouges, corrosion, and welds). The use of this data to develop and validate mechanistic models will produce reliable tools to assess a wide range of mechanical damage forms, thereby increasing safety, targeting areas that require maintenance, and supporting the improvement of pipeline standards and codes of practice. Many of the parameters related to the failure modes and mechanisms from the historical database are unknown and the models developed based on those data can be improved. Development of the experimental database is accomplished through the completion of full-scale testing using highly instrumented tests to evaluate conditions that lead to immediate failure via burst/rupture, and delayed failure due pressure cycling and fatigue. The full-scale testing work includes two projects that are dedicated to studying dent+gouge features in pipelines:
- MD-4-1: Full-Scale Experimental Validation of Mechanical Damage Assessment Models; testing in modern steels
- MD-4-6: Full-scale Experimental Validation of Mechanical Damage Assessment Models - Extension of MD-4-1; testing in vintage steels
PRCI has recently completed the full-scale testing for the MD-4-1 project, which has provided additional industry data for burst and fatigue failure for five (5) separate dent+gouge defects. The same 5 defects were created for testing of both failure modes, with the defect characteristics being defined based on available industry records of the types of mechanical damage failures that operators have experienced in the past and input from mechanical damage subject matter experts. The dent+gouge defects were created using controlled conditions and the GDF Suez Pipe Aggression Rig (PAR), which simulates heavy construction equipment (e.g., backhoe) impacting a pipeline. The initial tests were completed using X 52 and X 70 pipeline to create the test samples as a representation of more modern steels (defined as post 1970 construction).
Completing this work is a significant milestone for the PRCI Mechanical Damage Program, as the testing results provide the data needed for developed improved models for assessing the impacts of mechanical damage and making repair and rehabilitation decisions. The data from the full-scale testing program have been compiled and delivered to the SMEs that are developing the improved mechanical damage models for burst and delayed failure (being addressed separately under PRCI projects MD-4-3, burst failure model, and MD-4-4, fatigue failure model), and work on the models has started.
With the completion of the full-scale testing program for dent+gouge damage in modern steels, PRCI is preparing for testing in pipes that represent vintage steels, targeting lower grade, low-toughness materials that are consistent with pre-1970s era pipeline construction (MD 4-6 project). The defects will include a subset of the same 5 features used for modern steels for comparative evaluation and analysis of the effects of material properties on the behavior of dent+gouge damage. Test with these samples will follow the same procedures, instrumentation plans, and reporting as the modern steels samples. The data will be used for further development and validation of the mechanical damage models, and to provide important insights on the behavior of pipe steel affected by damage under a range of material types.
The results from the full-scale testing program will be discussed and presented at the PRCI 2012 Research Exchange Meeting along with the preliminary results of mechanical damage models for burst and fatigue failure. Please contact Mark Piazza, PRCI Program Manager, with any questions related to the Mechanical Damage program and full-scale testing.
This full-scale testing program is being implemented in coordination with PHMSA.