External Corrosion Behavior of Oil Pipelines with Polyethylene Coating under Pressure Fluctuations
Bibliographic record
Abstract
Abstract External corrosion on buried pipe steels has been demonstrated to be a major threat to pipeline integrity. Although it has been extensively investigated and well understood electrochemically, there is no particular corrosion rate model that is widely accepted by industry due to the complexities associated with coating performance, and heterogeneity of the soil environment (including bacteria, drainage, bulk resistivity, CP level, etc.). This paper demonstrates that the severity of external corrosion on Polyethylene (PE) tape coated oil pipe is exacerbated by the proximity to upstream (U/S) pump stations, and suggests mechanistic explanations related to pressure fluctuations. External corrosion features reported by the most recent In-Line Inspection (ILI) Ultrasonic Wall Measurement (UTWM) tools for three oil pipelines were correlated with the distance to U/S pump stations. UTWM ILI data is used as it includes features that are located under repair sleeves. These three oil pipelines with PE coating were investigated for a total length of approximately 3100 km. The pipelines have been in service for more than 40 years. One of the pipelines has experienced reversed flow operation. Analysis of the results shows that external corrosion features with depths < 20% Wall Thickness (WT) reported by UTWM tools are distributed uniformly along the pipelines. However, a clear increase in the frequency of corrosion features with depths >= 20%WT is seen within 10 km from the U/S pump station. There is a pronounced increase in the density of deeper feature classes in the same region. This phenomenon was also observed on the third oil pipeline with reversed flow directions. In addition, this trend is further validated by the distribution of field excavations triggered by external corrosion. Based on these data, it is evident that the frequency and severity of external corrosion on these tape coated pipelines is positively correlated to U/S pump station proximity. Possible mechanisms may include mechano-electrochemistry, and pressure fluctuations that facilitate electrochemical processes and/or PE tape coating damage: 1) Pressure fluctuations increase dislocation density and thus electrochemical potential ahead of the corrosion tip due to stress concentration. 2) Pressure fluctuations may refresh the electrochemical environments against the pipe surface and thus exacerbate corrosion. 3) The PE coating damage is accelerated (mechanically) by pressure fluctuations. The findings in this paper could help External Corrosion Direct Assessment (ECDA) locate severe corrosion features, especially for lines that are non-piggable. Also, these discoveries can provide guidance for future research and pipeline integrity management with external corrosion.
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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".