Power Generation

Industrial Access recently completed Liner Repairs and Duct Cleanout Services on a Boiler Stack. A swing stage was assembled at grade, then lifted to the top of the stack with a helicopter. This solution provided Industrial Access with a reliable access from the top in order to efficiently remove material buildup while avoiding overhead hazards and restoring the stack to good operational condition.

Industrial Access (IA) was contracted to perform an extensive condition assessment inspection of two liners and the breeching duct of a Boiler Stack at an electric generating station in the U.S. The structure consisted of a concrete chimney with two brick liners, each 600’ tall and 34’ in diameter. During the inspection, the team examined the interior of the liners and the breeching duct. An evaluation was performed of the significance of any detected degradation, deterioration, malfunction or damage to the stack and any associated equipment systems.

One of the liners was assessed to be in fair to poor condition based on the Class II inspection guidelines provided by ASCE. The interior of the liner was covered in material buildup of hardened flyash residue that increased progressively from top to bottom till it was several inches thick at the bottom. Buildup that is allowed to continue accumulating puts the structural integrity of the liner at risk by overloading stack walls and foundation, entrapping acid and moisture, and consequently compromising the durability of the brickwork.

In addition, the breeching duct of this liner was determined to be in very poor condition with a large amount of buildup and deterioration occurring on the walls. It had been subjected to continuous thinning and corrosion, which resulted in damage and holes on the steel plate, causing leakage of flue gases. IA provided prioritized repair recommendations based on the immediacy of concern and the severity of structural deficiencies.

In order to survey and clean the interior of the liner, a “hashtag” style cross-beam structure supported by full-circumference scaffolding was assembled on land. IA used a helicopter to lift the assembly and place it over the liner, which was the most efficient and cost-effective solution based on the structure’s height and remote location. A double-deck motorized suspended work platform was hung from the support beams to provide full-height interior liner wall access with overhead protection for the chimney technicians.

IA’s highly trained team utilized rope access techniques to perform the cleanout by dislodging pieces of accumulated material using pneumatic hammers. The team made sure to repair any cracks in the brickwork that were caused by the excessive buildup. A floor opening was also created to remove the fallen material, then repaired in accordance with the original stack design drawings provided by the client.

IA removed the duct expansion joint at the stack, built in a temporary closure isolating the stack from the duct, and installed access solutions in order to enable complicated duct cleanout operations to take place. Additionally, IA provided confined space watch and standby rescue to ensure safety during the operation. Holes on the steel exterior of the duct were patched and a flash coat of gunite was applied on the interior to protect it from excessive heat.

The repair and cleanout services were successfully completed, improving the overall condition of the stack and the breeching duct. The liner’s operation is now restored to its full efficiency while the duct is better insulated with gunite and steel plating patches preventing non-process air infiltration. Industrial Access has taken necessary preventive measures which will ensure the structure’s longevity and avoid extensive future repairs.