Implication of Fractographic Analysis of the Crack in an above Ground Pipeline - Potential Role of Hydrogen
Bibliographic record
Abstract
Abstract A crack was found in 2020 on a 324 mm (12-inch) OD above ground pipeline externally uncoated but insulated with mineral wool with aluminum cladding. The steel grade of the pipeline is CSA Z245.1 Gr 414 Category II with wall thickness of 7.9 mm (0.310-inch) operating since 2013. The product that the pipeline transports is casing gas and the pipeline is operated at a temperature of 150-200 °C. The circumferential crack initiated on the outer diameter (OD) and grew through-wall. Detailed fractographic analysis showed a mixed mode of fracture: predominantly intergranular separation with a small amount of cleavage corresponding to {001} lattice plane, which is confirmed by mated fracture surfaces and the presence of {001} etching pits. Striation-like features were found on the fracture surface; however, these striation-like features are not due to fatigue. Metallographic cross section analysis also showed the crack paths are mainly intergranular with some transgranular that is consistent with micro-fractographic analysis. Classic high-pH stress corrosion cracking (SCC) mechanism cannot explain the presence of transgranular cracking, and other evidence observed such as the lack of corrosion products at the crack tip, lack of corrosion damage on the grain boundary and the lack of SCC colony on the OD surface of the pipe. These findings led to the potential role of hydrogen in the cracking mechanism observed in the above ground insulated pipeline.
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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 | 0.001 | 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) | 0.002 | 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".