KILN STACK REINFORCEMENT TO MITIGATE STRUCTURAL RISK

Industrial Access performed inspection and reinforcement of a 371’ steel kiln stack at a cement manufacturing facility. The stack and its associated ductwork exhibited significant corrosion, weld failures, thinning steel, and structural weakening. The project focused on stabilizing the failing TMD system, reinforcing high-risk interior areas with steel support rings, and installing vertical stiffeners along the stack exterior. This comprehensive package of structural reinforcements repairs was designed to improve operational integrity of the stack while enabling continued use until the long-term replacement solutions are scheduled.

A cement production facility on the West Coast of the US contracted Industrial Access (IA) to assess and address ongoing structural deterioration of their 371’-tall cement kiln stack and ductwork. The stack was exhibiting significant signs of aging, including corrosion, weld failures, and material loss, putting the structure at imminent risk of failure. Of particular concern was the Tuned Mass Damper (TMD) assembly and top platform knee bracing, which were showing signs of instability and deterioration at its connection points.

IA initially conducted an inspection of the stack, the downcomer duct, and the gooseneck duct utilizing UAV technology and ultrasonic thickness (UT) testing. The inspection revealed extensive oxidation, compromised welds, and thinning, buckling steel shell with severe cracks and deformations around platform knee bracing and joints. In the ductwork, material loss due to corrosion was severe in localized areas, signs of thermal stress and heat sink damage, insulation failure, and aging of prior patchwork repairs.

Given the critical function of these systems in emissions control and plant operation, an emergency repair strategy was required. The priority was to mitigate safety risks and prolong the operational lifespan of the stack until a full system replacement could be scheduled during a future outage.

To complete the inspections and repairs, IA technicians utilized a combination of rope access techniques, UAV drone technology, crane-assisted man-basket systems, and suspended work platforms. Rope access allowed crews to navigate tight or elevated areas safely, while UAVs were used to assess the condition of exterior duct surfaces from safe distance. For the interior reinforcement phase, IA deployed suspended scaffolding platforms rigged from the top of the stack. These swing stages provided stable, hands-on access for installing reinforcement rings and performing welding at various elevations inside the stack. Together, these access methods enabled safe, efficient work execution across all critical areas of the structure.

To mitigate risk and extend the life of the stack, IA implemented a reinforcement strategy, prioritizing the most deteriorated areas. Once the structure was decommissioned for the outage, IA crew accessed the interior to install a total of four horizontal full-circumference 2’ steel reinforcement rings. Two rings were installed below the top platform, and two rings were installed at the CEMS platform elevation, targeting known structural weak points near knee bracing connections.

For the exterior repairs, IA first performed demolition of the failing top stiffener ring as well as the TMD assembly. A set of vertical stiffeners were installed near the top of the stack to counteract material loss and provided added rigidity. Any broken, cracked welds around the expansion joint were repaired, and areas with severe steel degradation were patched.

All structural repairs were completed safely and efficiently, addressing key areas of degradation across the cement kiln stack. Installation of interior steel rings and exterior vertical stiffeners significantly improved the overall structural integrity of the stack. Repairs to cracked and failed welds, along with targeted patch plating, have stabilized the most at-risk components and reduced the likelihood of progressive failure. These corrective actions have extended the service life of the structure, allowing the facility to maintain uninterrupted operations while planning for future system replacement. Continued monitoring and phased maintenance will be essential to preserving the long-term reliability of these critical emissions structures.