Case Study : Relining of Floor Section on Sizeable Outlet Duct

One of Corrocoat USA’s longest-standing clients; a 1.2 Giggawatt coal fired power plant in North Florida, required relining of a large section of the floor of a 35-year-old outlet duct* with a total surface area of 2,200 ft². The outlet duct at the plant was of a considerable size, and sitting 120 feet (36.6 meters) off the ground. The 450 feet (137 meter) long structure graduated from 12.5 feet (3.8 meters) diameter on one end out to 14 feet (4.3 meter) x 25 foot tall (7.6 meter) on the end, feeding into the stack. Corrocoat had 18 consecutive days to complete the project during the plant’s 28-day unit outage, coordinating with other contractors and outage related scopes of work, during the short span of time.

As soon as the unit went down and adequate time was allowed for cool down and certification for confined space entry, plant personnel utilized fire hoses to clean out the duct. Next, Corrocoat USA inspectors accompanied the owner’s 3rd party NACE Certified inspector to identify areas of the existing outlet duct lining that needed replacing. In addition to +/- 300 square feet (28 square meters) of spot repairs, the owner’s inspector decided to task Corrocoat USA with blasting and relining 100 lineal feet (32 meters) of the floor, plus 4 feet (1.2 meters) up the side walls, including the portion of the floor that includes a 45-degree slope.

The logistical requirements were not insignificant and both companies relished the challenges this caused. Product supplied from the UK needed to travel by airfreight, at a time where securing cargo space was at a premium. In order to safely access the incline for blasting, Corrocoat’s ite application team utilized their skills to build a mobile ladder, allowing for blasters to gain a solid foothold while blasting. 

After the blasting process, the team removed the grit from the surface to conduct a weld inspection. The blasting uncovered several areas in need of weld repairs. Following the welding repairs, the weld areas underwent re-blasting before the grit was thoroughly cleaned out of the duct. The surface was then primed with a holding primer – Polyglass PPA. Finally, the surface was laminated with 1.5 oz chopped strand fiberglass mat using Corroglass L600 series, followed by application of Polyglass VEF at 40 mils (1,000 microns) dft. Based on previous experience in this service environment, Corrocoat expects the new liner to last more than 30 years. The team completed the project 2 days ahead of schedule.

*A wet flue gas desulfurization (FGD) outlet duct in a power plant is a crucial component of the flue gas desulfurization system. It’s responsible for carrying treated flue gas from the wet FGD system to the atmosphere. Flue gas desulfurization is a process used to eliminate sulfur dioxide (SO2) from exhaust gases, primarily in coal-fired power plants. In a wet FGD system, the outlet duct directs flue gas, treated through absorption or chemical processes, out of the system. The term “wet” indicates the use of a liquid, typically an alkaline slurry, to absorb and react with sulfur dioxide in the flue gas. The wet FGD outlet duct must be designed to handle specific conditions, including temperature, pressure, moisture, and corrosive elements present in the treated flue gas. Its material and construction must withstand these conditions to ensure the reliable and efficient operation of the FGD system.

Overall, the wet FGD outlet duct is a critical component in the emission control system of a power plant, helping to reduce the environmental impact of the plant by removing harmful pollutants from the flue gas before it is released into the atmosphere.

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