Tank Restoration at TransCanada

This photo shows the 2 one million gallon aboveground storage tanks at the time of the tank inspection.

CommTank crew are performing a survey as part of the tank inspection. The survey results will determine if the tank has settled or shifted since it was installed.

A close-up view of one corroded area. The pitting is marked, measured and documented for the tank inspection report.

Because the tanks are tall and access is limited to a 36 inch manway opening, scaffolding was used to work on the AST.

CommTank crew are coating a portion of the roof that had been prepared by power washing and sanding.

This picture shows both completed tanks. They have been sandblasted, repaired, primed and painted.

Previous



Next

CommTank was hired to perform the tank inspections using a Magnetic Flux Leakage (MFL) scanner and Ultrasonic Test (UT) equipment. The MFL can scan large areas of steel quickly and provide an audio alarm when corrosion is encountered. The UT equipment measures the thickness of steel through coatings. When the MFL flagged a questionable area the UT equipment was used to measure each corroded area to determine how much steel was still present. The tanks were found to have pitting in the steel floor and on the tank walls. The UT thickness measurements showed a significant metal loss in the flagged areas with a remaining thickness of 0.225 inches. The nominal bottom plate thickness was .375 so the steel had lost .15 inches due to corrosion over the 25-year life span of the tank. The tank was also checked for level and deflection using a rotating laser and found to be within the maximum permitted by API 653.

Polyamide Epoxy Tank Coating Applied

The new coating for TransCanada's storage tanks, polyamide epoxy, was chosen for its chemical resistance to fuel oil. Polyamide epoxy is designed to protect steel and concrete in industrial exposures. CommTank was also contracted to repair and coat the tanks to meet the ASTM and SSPC standards for coating applications. New steel plates were welded to areas that had shown thinning and vacuum box testing was used to test the welds for leaks. The aboveground storage tanks and secondary containment enclosures were prepped by sandblasting to a near white metal and coated with an immersion grade epoxy primer. Each tank offered limited access in the form of manways so all staging and equipment had to fit through 36" round openings. Exterior coatings were applied in four applications with the final two being acrylic polyurethanes. After all coatings have cured CommTank will perform holiday testing using a high-voltage detector in accordance with NACE RP-01-88. A properly applied lining should provide a service life of 10-to-20 years so it is critical to confirm that there are no thin or uncoated areas.

About the Author: Dan Hoag

Dan Hoag has worked in the environmental and tank storage industry for 16 years. Dan’s range of expertise includes designing systems for oil spill clean-ups, treating soil contamination through "in situ" oxidation and testing, and inspecting underground storage tank systems. As head of Marketing and Information Technologies at CommTank, Dan draws from field experience to write about fuel, water and chemical storage technologies, and the regulations that affect them. He has developed training courses in home inspection, underground storage tank operator, ultrasonic thickness and tank tightness testing. Over the past decade, Dan has published over 60 articles about industry trends and has documented commercial, residential, and environmental projects through illustration, videos, and photography. When Dan unplugs from technology, he spends his time backyard farming, hiking, and kayaking, while masquerading as a hockey player during the wee hours of the morning.