ing for smoke escaping. However, the thickness of the tanks prevented smoke from penetrating any remaining cracks. The engineers then tried a soap test on the tank’s exterior, ultimately discovering an area where the soap was bubbling to indicate where gas was escaping. After draining the tank and conducting further inspections, the team ultimately located the hard-to-find trouble spot, which was about 10 feet from where the soap had bubbled on the exterior. The air leak trav- eled along a joint before escaping outside. The source of trouble was a difficult-to-access cold joint that had been improperly filled since the time of the digester’s original construction. The coatings team care- fully repaired the joint with SherFlex, refilled the tank with water, and were elated when the tank held pressure. “Restoring a digester tank typically wouldn’t be this difficult, but the age and construction of the vessels certainly contributed to the challenge of stopping all the leaks, as did the weather,” Johnson said. “Collaboration was vital to solving the leak issue and restoring the digester. Everyone worked together to give the owner the best possible outcome.” Maintaining poise under pressure Due to the cold weather delays and repeated testing, troubleshooting, and repair processes, it took nearly six months to finalize the first tank and return it to service. With the lessons learned from that tank, the team
made some adjustments and was able to repair the second tank much faster and without issues, completing it in November 2015. Both digester restorations will enable long-term service for the City of Austin. “The coating and lining selection was a key to the success of the proj- ect,” said Joe Cesarak, senior coatings specialist, SEH. “Because the team was able to completely seal the decades-old covers with these products, the city didn’t need to build new digesters. Instead, it can expect the restored vessels to continue operating for years to come.” With its anaerobic digesters fully rehabilitated and operating at full capacity, the City of Austin can now better manage its industrial waste processing demands. Satisfied with the project, the city awarded Champion Coatings a tank lining project at the same plant. In addition, the full team’s successful troubleshooting efforts earned the three com- panies the 2016 Sherwin-Williams Impact Award, which honors water and wastewater projects that deliver a lasting impact on the industry. GREG LARSON is senior protective and marine coatings representative for Sherwin-Williams Protective & Marine Coatings (https://protective.sherwin- williams.com). He works with owners, engineers, contractors, and inspectors related to coating specifications, applications, and troubleshooting in all protec- tive coating markets. He has more than 24 years of experience and is a SSPC Level 1 and NACE Level III Certified Coatings Inspector. He can be reached at greg.j.larson@sherwin.com.
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