Full-Scale Stress Corrosion Crack Growth Testing of an X70 Spiral-Welded Pipe in Near-Neutral pH Soil Environment
Bibliographic record
Abstract
Stress corrosion cracking (SCC) in near-neutral pH environment remains a major concern for high pressure pipelines transporting oil and gas in Canada since its first discovery in 1980s. A variety of laboratory experiments and models have been developed to address different aspects of this complex problem. Full-scale pipe SCC testing using soil box that mimics the condition in the field can directly assess crack growth in terms of pressure level, range of pressure fluctuation, soil conditions, etc. This type of test also offers the most direct validation of SCC models. A state-of-the-art full-scale SCC pipe testing facility has been established at CanmetMATERIALS Hamilton Laboratory. The facility includes a new hydraulic power unit (HPU), an upgraded 500 kN fatigue frame, and a new 2000 psi (14MPa) pressurization system. In addition, a 24-channel direct current potential drop (DCPD) unit has been refurnished for in-situ monitoring of crack growth. The full-scale pipe SCC testing facility has been successfully used to measure crack growth in an X-70 (Grade 483) large diameter (914 mm or 36” OD) spiral seam-welded pipe. Six axial cracks were made using saw cutting and fatigue pre-cracking in the base metal and across the spiral-weld metal. All cracks were buried under two types of soil boxes with soil obtained from a near-neutral pH SCC pipeline failure site mixed with distilled water or NS4 solution. The pH of the solution was maintained between 6.9 and 7.2 throughout the testing. Several loading conditions were tested and DCPD was used to monitor SCC growth rate during all the tests. No detectable growth was observed in the cracks of weld area during all the tests mainly due to over-matching strength. Crack growth was also not detected for the base metal until the maximum pressure was raised up to 95% SMYS with R = 0.7. The threshold of the range of stress intensity factor, (ΔK)th for SCC is thus estimated to be between 11.53 to 13.52 MPa m1/2. The measured average crack growth rate was 5.98×10−7 mm/s.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".