Development of a Sensor for Real-Time Detection of In-plant Crevice Contaminants

Most forms of corrosion damage in electric power plants are believed to involve the concentration of corrosive species in critical crevice locations such as between disc keyways and keys. The development of an on-line, real-time sensor capable of detecting the concentration of corrosives in crevices is presented in this paper. The sensor measures the temperature and conductance of fluid films entrapped within the crevice of the sensor. The sensor crevice was designed to entrap contaminants similar to those found in actual crevices and to contain the contaminants for future analysis.

Several sensors were laboratory-tested in aqueous solutions within autoclaves and steam lines. Three sensors were evaluated at an electric power plant. These sensors were hard-wired to a steam extaction line and an autoclave in which stress corrosion cracking tests were being conducted. Although problems were experienced with the materials used in sensor construction, the field evaluation demonstrated real-time collection of conductivity and local temperature data and accumulation of crevice contaminants with subsequent laboratory analysis.