Observations from Several Condition Assessments of Prestressed Concrete Cylinder Pipe Used at Energy Generation Facilities
Notice bibliographique
Résumé
Golder Associates Inc. has conducted several condition assessments of prestressed concrete cylinder pipe (PCCP) used in the cooling water systems of energy generation facilities. This paper presents observations from these condition assessment projects. A vital component to the operation of energy generation facilities is the cooling water system. The cooling water system conveys cool water from a river or basin through the plant's condensers to condense steam produced in the process of power generation. The heated water is then returned to the river or basin, or sent through cooling towers to dissipate the gained heat. To work effectively, these systems typically operate with high flows (greater than 200,000 gpm) and low pressures (less than 60 psi) in large diameter pipelines (typically 54 to 120 in). These systems may provide cooling water to one or more units, and redundancy is not typical. Thus, the isolation of these systems for evaluation or repair may require the temporary shutdown of one or several units, resulting in significant costs associated with purchasing replacement power. Many utilities operating energy generation facilities constructed in the 1970s and 1980s have not included these cooling water systems in their general plant evaluation and maintenance schedule, and these systems have often operated continuously for over 30 years. Due to the increased awareness of plant personnel, and the age of their buried infrastructure, these systems are now being evaluated. Condition assessment of these systems is similar to other pipelines with tasks such as document review, physical evaluation and condition summary, but also requires detailed planning to coincide with planned unit outages, and in some cases requires significant coordination with other facilities to allow for several unit outages at the same time. Pipeline condition assessments conducted have identified a wide range of conditions for the 30- to 40-year-old PCCP used in cooling water systems, ranging from pristine pipe, to pipe that has technically failed. Factors contributing to the distress observed in the pipelines include the manufacturing practices (particularly the use of class IV prestressing wire), installation practices, nearby stray electric currents, groundwater quality and interaction, and operational stresses. Recommendations from these condition assessments have also varied greatly, from continued evaluation, instituting operational controls, or even complete replacement of distressed portions of the line.
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Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,001 | 0,003 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,002 | 0,001 |
| Études des sciences et des technologies | 0,001 | 0,000 |
| Communication savante | 0,000 | 0,001 |
| Science ouverte | 0,000 | 0,001 |
| Intégrité de la recherche | 0,001 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».