Outline
- Abstract
- Introduction
- Test Specimen and Test Setup
- Instrumentation
- Test Procedure
- Test Results
- Conclusions
- Acknowledgements
- Nomenclature
- References
رئوس مطالب
- 1.مقدمه
- کلیدواژه ها
- 2. نمونه تست و آماده سازی تست
- 3 تجهیزات
- 4 راه کار تست
- 5 نتایج تست
- 6. نتیجه گیری ها
Abstract
Buried pipelines may be subjected to various complicated combinations of forces and deformations. This may result in localized curvature, strains, and associated deformations in the pipe wall. As a result, wrinkle may form. The wrinkled pipeline may then develop a rupture in the pipe wall and lose its structural integrity if it is subjected to further sustained loads or deformations. Recently, laboratory tests on NPS6 steel pipes were undertaken at the University of Windsor to study the wrinkling and post-wrinkling behaviors of this NPS6 pipe when subjected to lateral load in addition to internal pressure and axial load. Four full-scale laboratory tests were conducted, and it was found that the application of lateral load on wrinkled pipe produces a wrinkle shape similar to that occurred in a field NPS10 line pipe. Complex test setup was designed and built for successful loading and completion of these tests. This paper makes a detailed discussion on the test setup, test method, loading and boundary conditions, instruments used, and test results obtained from this study.
Keywords: axial load - internal pressure - lateral load - line pipe - rupture - wrinkleConclusions
The following conclusions are made based on the experimental results obtained from this study. The conclusions made are specific to the pipe specimen and load history used in this study.
1. The line pipe used in this study is very ductile and does not rupture under application of large axisymmetric axial deformation.
2. The maximum local compressive strain values obtained after the end of load step 1 was 15%.
3. The combination of the axial and lateral loads applied to the wrinkled specimens is able to produce the wrinkle shape that looks similar to the one developed in the field NPS10 line pipe.
4. It seems that the levels of internal pressure (0.15py and 0.30py) chosen in this study did not influence the wrinkle shape and the location of the rupture much.
5. The unloading of internal pressure in load step 3, which is during application of the second axial deformation, however, produced the wrinkle shape and rupture, which correlate better with the field NPS 10 line pipe.
6. All four specimens ruptured in the wrinkle region during the pressure test and when the internal pressure was only in the range of 0.14–0.17py and as a result, all the test specimens lost their structural integrity. In fact, specimen 3 split into two pieces through the crest. This study, therefore, states that the NPS 10 field line pipe may have ruptured when the line pressure was being brought back to its normal level after its regular shutdown.