| Titre : |
Contradictory information in a project specification : coating failure on the interior of a wastewater digester |
| Type de document : |
texte imprimé |
| Auteurs : |
Chrissy Stewart, Auteur |
| Année de publication : |
2016 |
| Article en page(s) : |
p. 20-25 |
| Langues : |
Américain (ame) |
| Catégories : |
Analyse des défaillances (fiabilité)
Eaux usées -- Stations de traitements
Expertises
Revêtements -- Défauts:Peinture -- Défauts
Revêtements protecteurs -- Détérioration
|
| Index. décimale : |
667.9 Revêtements et enduits |
| Résumé : |
The wastewater industry poses some of the most significant corrosion protection challenges for industrial protective coatings. In this case study, coating failure in the form of peeling and delamination (on concrete) and blistering (on steel) was observed on the interior of a digester at a wastewater treatment facility after only five years of service. Removal of sludge from the digester revealed disbonded pieces of coating, which alerted the facility owner to the failure. Due to the relatively short period of coating performance and the importance of a properly protected substrate, an investigation into the cause of the premature coating failure was undertaken.
The digester consisted of a concrete shell with a steel skirt plate situated at the top of the shell. A steel dome was attached to the skirt plate. The specification indicated that the operating temperature of the digester ranges from 95-to-131 F, and that a single coat was to be applied at a dry film thickness (DFT) of 125 mils on the concrete and 60 mils on the steel substrates. The specification listed several polyurethane coating materials that were deemed suitable for this environment. The coating selected for installation was one of the materials listed in the specification. The manufacturer’s product data sheet (PDS) listed a maximum service temperature of 120 F for immersion service and 180 F for dry conditions.
Because the contents in the digester were composed of sludge from a wastewater treatment plant, the environment would be considered immersion. The sludge included a mixture of organic and inorganic solids, grit, grease, scum and industrial solvents. Reportedly, small quantities of hydrogen sulfide, hydrogen and nitrogen gases were likely to be present as well. The design engineer for the digester reported that the contents were uniformly mixed to maintain consistent pH and temperature throughout the digester. Since the time that the selected coating material had been applied, the pH readings were reasonably close to 8 and the temperature ranged from 122-to-126 F. |
| Note de contenu : |
- Site investigation
- Laboratory investigation
- Summary of the site investigation and forensic evidence
- FIGURES : 1. Cross section of sample removed below operating level - 2. Cross-section of sample removed above operating level |
| En ligne : |
http://www.paintsquare.com/archive/?fuseaction=view&articleid=5923 |
| Format de la ressource électronique : |
Web |
| Permalink : |
https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=28391 |
in JOURNAL OF PROTECTIVE COATINGS & LININGS (JPCL) > Vol. 33, N° 9 (09/2016) . - p. 20-25
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Contradictory information in a project specification in JOURNAL OF PROTECTIVE COATINGS & LININGS (JPCL), Vol. 33, N° 9 (09/2016)
