Title: Advances in Nondestructive Evaluation Methods for Inspection of Refractory Concretes
Author(s): William A. Ellingson
Publication: Symposium Paper
Appears on pages(s): 33-56
Keywords: acoustic measurement; blast furnaces; coal gasification; corrosion; cracking (fracturing); erosion; gamma rays; high temperature; inspection; interferometers; lasers; linings; nondestructive tests; penetrameters (radiation); radiography.
Refractory concrete linings are essential to protect steel pressure boundaries from high-temperature aggressive erosive/corrosive environments in many energy-intensive commercial processes such as blast furnaces and petrochemical plants, and in new industries such as synthetic fuel production. Advanced nondestructive evaluation methods are being developed for assessing the integrity of refractory linings. Radiographic techniques, thermography, acoustic-emission detection, and optical laser interferometry have been shown to yield information on the structural status of refractory concrete. Methods using 60Co radiation sources can yield measurements of refractory wear rate and images of cracks and/or voids in pre- and post-fired refractory linings up to 60 cm thick. Thermographic (infrared) images serve as a qualitative indicator of refractory spalling, although quantitative measurements are difficult to obtain from surface-temperature mapping. Acoustic emission has been shown to be a qualitative indicator of thermomechanical degradation of thick refractory panels during initial heating and cooling. Laser interferometry methods have been shown to be capable of completely mapping refractory lining thicknesses. This paper presents recent results obtained from laboratory and field applications of these nondestructive evaluation methods in petrochemical, steel, and coal-conversion plants.