Development, Design and Testing of Optimized Soft Crack Arrestors
The purpose of the Phase II Small Business Innovative Research project was to evaluate the design and ability of a “Soft Crack Arrestor” (SCA) device to stop unstable ductile crack propagation in large-diameter gas pipelines. If the crack-driving force is high enough, mechanical crack arrestors are a viable alternative to crack arrest by toughness of the pipe body and are allowed by ASME B31.8 code. The unique nature of the SCA device lies in its design which utilizes both strength and ductility of the composite arrestor material to stop unstable ductile axial crack growth and also prevent a pipe ring-off failure mode. The research during this Phase II project included development of a fiber that possessed the requisite strength and ductility properties to perform as needed for the SCA application and also be low enough in cost to be competitive and attractive for industry use. Additionally due to the high costs associated with performing full-scale burst testing needed to prove concept and design of the SCA, industry pipeline members were petitioned to contribute materials and other resources to complement government funding available to carry out the project but in particular to help pay the costs of the testing activities. The authors were able to secure donated pipe materials from a member of the pipeline community but other contributions (welding, end caps, transportation of test items, wrap SCA onto test pipes, etc.) were not achieved. Therefore, the funds to cover these items were extracted from project funds which resulted in a major change in full-scale testing. Pretest analyses were performed to aid in the design and location of the SCA array along the test pipe. Wrapping of the fiber onto the pipe to form the SCA array was performed by a selected composite wrap contractor. Finally, full-scale testing was performed at a Mojave, CA site by a cadre of subcontractors (most of whom had been used in previous testing) to aid in the significantly difficult tasks involved in performing full-scale testing. The first full-scale burst test was conducted in mid-April 2012 at the Mojave site. A “Soft Crack Arrest” was achieved, i.e., there was no ring-off fracture of the pipe material at the edge of the arrestor as occurs with steel or fiberglass arrestors. The test temperatures were higher than desired, which affected the fiber strength so that only the longest SCA worked. Nevertheless, even this arrestor was shorter than steel or fiberglass-based arrestors used in past full-scale validation tests. The efficiency of the “Soft Crack Arrestor” comes from the fact that the ductile fiber used and developed for this application allows the crack to propagate under the arrestor and more of the crack-driving force is taken up by the entire arrestor rather than just the front edge of the arrestor. Subsequent full-scale testing is highly recommended to further validate the SCA design process and provide encouragement for use in construction projects by the pipeline industry.
- Record URL:
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Corporate Authors:
Engineering Mechanics Corporation of Columbus
3518 Riverside Drive, Suite 202
Columbus, OH United States 43221Pipeline and Hazardous Materials Safety Administration
Department of Transportation
East Building, 2nd Floor, 1200 New Jersey Avenue, SE
Washington, DC United States 20590 -
Authors:
- Wilkowski, G
- Hioe, Y
- Kennedy, J
- Hattery, G
- Mincer, P
- Wall, G
- Krishnaswamy, P
- Publication Date: 2012-12
Language
- English
Media Info
- Media Type: Digital/other
- Edition: Draft Report
- Features: Figures; Photos; References; Tables;
- Pagination: 27p
Subject/Index Terms
- TRT Terms: Composite materials; Gas pipelines; Prototype tests
- Uncontrolled Terms: Composite wraps; Soft crack arrestors
- Subject Areas: Design; Pipelines;
Filing Info
- Accession Number: 01640839
- Record Type: Publication
- Report/Paper Numbers: Project No. 09-G78-01
- Contract Numbers: DTRT57-09-C-10031
- Files: TRIS, ATRI, USDOT
- Created Date: Jul 10 2017 10:58AM