EMERGENCY REINFORCEMENT OF DEFLECTED & CORRODED BOILER STACKS

Industrial Access performed inspection and reinforcement of four steel recovery boiler precipitator stacks exhibiting heavy steel shell corrosion and deterioration. One of the stacks was notably leaning and required an emergency intervention to prevent any further degradation and risk of collapse. The bottom sections of all four stacks received repairs that included patching and welding of the damaged steel shell, replacement of corroded stiffener rings, and circumferential plating reinforcement.

A pulp and paper mill in the southeastern USA first contracted Industrial Access (IA) to inspect and perform structural support repairs on a 116’-tall recovery boiler precipitator stack that was evidently leaning off-axis. A severe case of corrosion under insulation (CUI) was identified during the inspection. The client requested a look at the remaining three stacks of the same design, and a similar level of steel wall degradation was confirmed. CUI occurs when moisture from weather, condensation, and acidic flue gases becomes trapped underneath the insulation, and if left unaddressed, this environment dramatically accelerates the rate of steel deterioration over time.

During this mobilization, IA completed exterior inspections of all four stacks utilizing a drone, visual assessment, and UT readings, and proceeded to perform emergency structural repairs to address the existing stack deflection, the significant corrosion, oxidation, thinning shell walls with numerous holes, and compromised stiffener rings.

To complete the structural repairs, IA technicians used scaffolding to safely reach all work zones along the bottom elevations of the stacks. Scaffolding is a great solution when working on compromised structures that require a full, hands-on, 360-degree access. IA crew are highly trained and equipped to offer unique solutions for inspections, repairs, and maintenance on tall or hard-to-reach structures.

IA began the project by performing a detailed exterior inspection of all four stacks to evaluate the extent of corrosion and structural damage. Once the inspection findings were reviewed and the mitigation plan was confirmed, the exterior surfaces of each stack were prepped for repair. The outer cladding and insulation were removed to access the corroded carbon steel shell, and the surfaces were cleaned and prepped.

To stabilize the leaning stack, IA installed an emergency system of vertical support beams and guy wires to counteract deflection and restore structural alignment. The vertical stiffeners were connected to the stack via HSS and steel plates. Stabilizing this stack was a critical safety measure to reduce the risk of progressive failure and ensure continued safe operation of the surrounding equipment.

IA continued onto the steel repair work on areas identified as high-risk. This included replacing deteriorated stiffener rings, installing reinforcement plates, and applying seal welds to ensure structural integrity and prevent further corrosion. Temporary shoring systems were set up prior to stiffener ring installations to ensure safety and structural support during repairs. Any failed or missing anchor bolts were replaced.

All structural repairs were completed safely and responsibly, addressing critical areas of corrosion and instability across the stacks. These measures were part of a targeted response to restore safety and functionality in the near term, allowing the facility to maintain operations while planning for future, long-term solutions. The installation of the vertical support system, along with the replacement of degraded stiffener rings and steel plating, has improved the structural stability, load distribution, and structure alignment of the boiler stacks. These corrective measures have extended the operational lifespan of the stacks and mitigated potential safety hazards. Ongoing inspection and timely repair remain key to maintaining the reliability and performance of aging steel stack infrastructure.