RECOVERY BOILER REPAIR & CARBON FIBER REINFORCEMENT

Industrial Access performed rehabilitation repairs on a reinforced concrete recovery boiler chimney exhibiting widespread concrete deterioration, steel corrosion and cracking, and defective lightning protection system. Scope included concrete repairs, installation of a carbon fiber reinforcement wrap at the upper chimney section, rehabilitation of the breeching ducts and refractory liner, replacement of LPS, and restoration of steel appurtenances. Protective coating systems were applied to the chimney exterior and all associated steel components to mitigate future deterioration and extend the long-term service life of the structure.

A paper manufacturing facility in the southeastern United States retained Industrial Access (IA) to perform a condition assessment inspection and rehabilitation program for an aging reinforced concrete chimney serving a recovery boiler system. The approximately 300’-tall chimney featured a reinforced concrete exterior shell with a gunite-lined brick liner and had been exposed to years of harsh operating conditions, acidic flue gas attack, weather exposure, and general age-related deterioration. The client requested a comprehensive inspection of the structure and its appurtenances to evaluate its current condition, identify active deterioration mechanisms, and develop a repair program to extend the service life of the asset.

During the inspection, IA identified extensive cracking, crazing, spalling, and previous repair failures throughout the concrete shell, with the most severe deterioration concentrated near the upper elevations below the chimney cap. Additional deficiencies included defective and disconnected lightning protection components, cracked welds and oxidation on elevated platforms and support systems, deteriorated breeching duct components, and failed protective coatings throughout the structure. IA developed a phased repair program focused on restoring structural integrity, addressing active deterioration, and implementing long-term protective measures.

To complete the inspection and rehabilitation work, IA technicians utilized rope access techniques, suspended man-baskets, temporary scaffolding, and the structure’s existing platforms, ladders, and adjacent access systems to safely reach all work areas throughout the chimney. Rope access methods allowed the crew to efficiently perform detailed inspections, concrete repairs, coating applications, lightning protection installation, and refractory repairs across the full height of the structure while minimizing the need for extensive conventional access systems. Temporary scaffolding was erected at select upper elevations to support critical repair activities, including platform rehabilitation and carbon fiber reinforcement installation. IA’s highly trained technicians combined multiple access methods to safely execute the repairs while maintaining efficient access to difficult-to-reach areas of the operating facility.

IA began the project by performing a complete washdown and repair mobilization of the reinforced concrete chimney structure. Initial work included removing deteriorated and ungrounded LPS components and replacing them with a new lightning protection system, including new air terminals, downlead sections, and a full-circumference grounded loop system. IA also addressed the breeching duct system, where deformation, corrosion, and insulation exposure had compromised performance and durability. The ductwork was mechanically realigned and reinforced with a steel pipe bracing, insulation voids were sealed, and refractory repairs were completed around duct penetrations using high-temperature resistant materials to restore both thermal protection and structural continuity.

IA then proceeded with structural and protective repairs throughout the chimney exterior and appurtenances. Cracked and spalling concrete areas were repaired from the top of the structure to the base using specialized repair epoxy systems, followed by the installation of a full-circumference carbon fiber reinforcement wrap around the top 12’ section of the chimney to strengthen the degraded concrete shell and help protect it against further deterioration. Additional repairs included restoring cracked welds on the top platform knee-braces, replacing deteriorated or missing hardware on ladders, platforms, stair systems, and catwalks, and refurbishing the chimney cap with new hardware and protective coatings.

To complete the rehabilitation program, IA applied protective coating systems to the repaired concrete surfaces and all exposed steel access components. A UV-resistant coating system was installed over the carbon fiber reinforced section and upper concrete elevations, while a conditioning protective coating was applied to the remainder of the chimney exterior to improve long-term durability against weathering and flue gas exposure. All platforms, ladders, spiral stairs, support beams, and knee-braces received surface preparation and a multi-coat protective paint system to mitigate corrosion and extend the service life of the structure.

All repairs were completed safely and on time. The completed work addressed critical areas of concrete deterioration, steel corrosion, coating failure, and lightning protection deficiencies throughout the chimney structure and its associated access systems. Structural reinforcement of the upper chimney section through the installation of a full-circumference carbon fiber wrap restored strength to the degraded concrete shell and helped mitigate the risk of future spalling and deterioration.

Additional repairs to the breeching ducts, refractory liner, elevated platforms, ladders, and structural steel support components improved the overall integrity, safety, and reliability of the structure. These corrective measures extended the operational service life of the chimney while reducing ongoing maintenance concerns and improving the overall condition of the facility’s critical emissions infrastructure.