Abstract
Since September 1982, Radian Corporation has been investigating the causes of failure of flue gas desulfurization (FGD) system components as part of an EPRI-sponsored program. This paper summarizes three case histories related to uncoated metallic components: stainless steel sprayer nozzles, a limestone slurry storage tank, and components of retrofitted forced-air oxidation systems. None of these components have received much consideration in the corrosion literature, but each represented a significant actual or potential maintenance liability, both in dollars and in downtime for repairs. This program has also demonstrated the value of including corrosion/failure analysis specialists in routine inspections during plant outages.
The use of an extremely coarse-ground limestone with a high flint or quartz content was found to be the probable cause of rapid erosion of the CF-8M stainless steel sprayer nozzles.
Erosion-corrosion was found to be the cause of failure, in less than three years, of an unlined carbon steel limestone slurry reagent storage tank. Corrosion was low except in areas where slurry agitation caused rapid changes in direction of flow of the slurry.
Break up, after a few months of operation, of forced-air oxidation sparger arrays was found to follow stress corrosion cracking failure of Type 317 U-bolts used to anchor the arrays. This failure, not previously recognized as a materials problem, was investigated incidentally to an unrelated problem. This demonstrates the value of including corrosion/failure analysis specialists on the plant inspection team during routine outage inspections.
