Evaluation of Pipe Wall Thickness based on Contrast Measurement Using Computed Radiography (CR)

Abstract

Specific properties of imaging plates, like wide dynamic range and greater sensitivity to radiation dose compared to radiographic film, as well as possibility of computer assisted analysis of digital radiographic image make computed radiography (CR) excellent non destructive method for pipe corrosion/erosion monitoring, especially insulated pipes in processing industry. Paper presents methodology for evaluation of pipe wall thickness based on the measurement of achieved radiographic contrast between areas of wall thinning and surrounding material. This technique could be used as complementary technique to usual tangential radiographic technique. Dependence of pixel intensities of digital radiographic image and radiation intensity that reaches imaging plate at three different X-ray energy levels was established. Based on that, optimatization of exposure parameters and selection of X-ray radiation energy (tube voltage) is discussed and the technique based on measurement of radiographic contrast for evaluation of the wall pipe thinning was proposed. This technique was validated by experimental measurement of wall thickness on pipe sample with artificial wall thinning areas. Measurement error was less than 5% for given sample.