Optimization of NDE Reexamination Locations and Intervals for Grade 91 Piping System Girth Welds
Bibliographic record
Abstract
It has become apparent with the development of creep strength enhanced ferritic steels, the mandatory ASME B31.1 Chapter VII and the non-mandatory ASME B31.1 Appendix V guidelines require a more rigorous method to manage the Grade 91 piping integrity at Genesee Unit 3. Given the relatively young age of Genesee Unit 3, three questions have been asked: 1) when do the examinations start, 2) what locations should be examined first, and 3) how often should the same location be reexamined? To ensure that the best value is obtained from the reexamination budget, a five-step process can be effectively used to define and categorize the scope of each set of reexaminations in the girth weld integrity management program. The five processes are performing the following analyses: 1) an evaluation of the historical information, 2) piping system hot and cold walkdowns, 3) as-designed and as-found piping stress analyses, 4) creep life consumption evaluations, including elastic and inelastic axial and radial stress redistributions, and 5) creep crack growth curve analyses. Reexaminations of the few critical lead-the-fleet weldments are performed with lower examination costs and higher confidence. Evaluations of the Genesee Unit 3 main steam (MS) piping system revealed that the applicable weldment stress is probably the most significant parameter in determining the Grade 91 girth weld critical reexamination locations and intervals. ASME B31.1 piping stress analyses of the MS piping system have sustained load stress variations of more than 100% among the girth welds. The lower bound American Petroleum Institute (API) 579 creep rupture equation for Grade 91 operating at 1,060°F (571°C) indicates that the creep life is a function of stress to the power of 8.9; consequently, a 15% stress increase results in about 2/3 reduction of creep rupture life. Creep crack growth analyses of several of the MS piping system weldments revealed that the creep crack growth time to grow from 1/8 inch to through-wall is a function of stress to the power of 8.8; consequently, a 15% stress increase results in about 2/3 reduction of time for a 1/8-inch crack to grow through-wall. This evaluation reveals that a few critical lead-the-fleet locations should be reexamined most frequently and justification can be provided for much longer reexamination intervals of the remaining girth welds with much lower applied stresses.
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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 | 0.002 | 0.005 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.002 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
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".