Corrosion Evaluation of Pipes by Radiography

N. Rastkhah, K. Edalati, A. Kermani, M. Seiedi, A. Movafeghi Safety and Radiation Protection Technological Center, Iranian Nuclear Regulatory Authority, Atomic Energy Organization of Iran, Northern Kargar Ave., Tehran, Iran Abstract: This study is a new attempt followed the research project conducted by IAEA in a Contract Research Project (CRP). In this new challenge, the reference blocks designed to minimize the deficiencies occurred in previous project, which also covers higher diameters. Different artificial defects were made in the reference blocks consisting step reduction in thickness to represent the general corrosion, flat bottom holes with different depth in each step and a groove for pitting and local corrosion. Diminutions of defects are related to the thickness of the portion to give better density evaluation and respectively more precision. Density evaluation of Double Wall Radiography of prepared reference blocks as well as Tangential Radiography showed that these methods can be implemented with acceptable reliability for pipe wall corrosion evaluation which could lead to draft a standard procedure. Introduction: Corrosion in the pipes and remaining wall thickness measurements are major concern in the piping service life. This problem is vital when pipe carries hazardous substance. Lifetime estimation depends highly on the operating and environmental condition. So routine inspection is quite necessary which usually requires removing the insulation and applying the required method. This inspection takes time and is more costly due to repair of insulation. Evaluation of corrosion by radiography has been studied before but quantitative evaluation and standardization have not achieved yet. Industries would prefer to apply this method with more reliability. Two techniques can be implemented in this respect: Tangential Radiographic Technique (TRT) (shown in Fig. 1a) [1,2,3,4,5] Double Wall Radiographic Technique (DWT) (shown in Fig. 1b) [6,7] The aim of present study is to investigation of the accuracy of radiographic method for evaluation of internal and external corrosion in 6 and 10 inch pipes.