Condition assessment of chimneys and other structures using nondestructive testing

Smokestacks and storage silos are by nature difficult to inspect. The problems of access to a sheer-sided structure that may be more than 1,300 feet in height mean that close visual observation of the surface is rarely performed. Typically little or no physical testing is done, until there is evidence of severe distress, such as falling debris or large open cracks that are visible from the ground. Some owners schedule inspection and maintenance by specialist contractors, but such inspections rarely go beyond visual surveys, and intervals between inspections are determined arbitrarily. Additional drawbacks are that visual surveys tend to be subjective, and are hampered by surface coatings, when present. This paper describes the application of these techniques to tall smokestacks, silos, and other thin-walled concrete structures such as natural draft cooling towers, and the establishment of databases to aid in long term deterioration monitoring.