Final report of a coordinated research project on development of protocols for corrosion and deposit evaluation in large diameter pipes by radiography

The International Atomic Energy Agency promotes Non-Destructive Testing (NDT) methodology and technology under its technical cooperation and research programs. Many developing Member States (MS) have established NDT groups which are active in training and certification of NDT specialists and in provision of services to industries. The reliability and safety of industrial equipment especially in petroleum, petrochemical and chemical industries, in power stations, desalination plants and urban gas installations are substantially influenced by degradation processes such as corrosion, erosion, deposits and blocking of pipes which might cause fire, leaks, reduced production or unpredictable and costly shutdowns due to repair and replacement. The condition of critical components in these industries can be monitored by the proper use of non destructive inspection methods even while the plant is in operation, thus making possible the planning of component replacements, repairs, deposit removal and shutdowns. Preventive and corrective maintenance averts the environment and the public from excessive risk of industrial disasters. One of the most important parameters in piping or pipelines to be monitored and measured is the loss of wall thickness due to corrosion. Radiography is an effective method of determining this loss. Radiography is also the method of choice to determine the amount of accumulated deposits and offers the advantage of being able to inspect the pipe without costly removal of insulation material often in harsh plant environment conditions (high temperature, elevated pressure, for example). Tangential radiography and Double Wall (density measurement) techniques are used. The principle of corrosion measurement or monitoring using tangential, film-based radiography is already known. Much of past experience, however, is limited to qualitative determination of internal defects; there are no standardized and universally recognized protocols, recommended practices or standards for those particular radiographic tests aimed at quantitatively measuring the remaining wall thickness of corroded pipes, especially in situations of insulated pipes or those operating at high temperatures. Many important decisions are related to this remaining pipe wall thickness. A CRP on validation of protocols for corrosion and deposit determination in small diameter pipes by radiography (CORDEP) was completed in 2000. These results showed that for insulated pipes, only tangential radiography was feasible, since the density measurement method requires complicated simulations. Ir-192 isotope is preferred instead of X-rays to get a better definition in tangential technique. For determining the depth of pits and local corrosion area, the density measurement method was found satisfactory. It was recommended that the research be continued on corrosion and deposit evaluation in large diameter pipes by radiography (> 150 mm). This is a new challenge for many NDT laboratories in developing MS. The CRP on Validation of Protocols for Corrosion and Deposit Evaluation in Large Diameter Pipes by Radiography was implemented from 2002 to 2005, with the participation of twelve countries: Algeria, Canada, Germany, Hungary, India, Iran, Malaysia, Pakistan, Romania, Syrian Arab Republic, Turkey and Uruguay. The CRP aimed to provide practical guidelines and a recommended practice for the monitoring of remaining wall thickness and accumulated deposits in large diameter pipes, a vital need for many industrial installations. Large pipes with a diameter greater than 150 mm with or without insulation are abundantly used in almost all industrial sectors; corrosion in pipes of this diameter is a major industrial problem to which a solution must be found both for financial and safety reasons. The practical guidelines of this CPR will be submitted for approval by the International Organization for Standardization (ISO) as a Protocol for Corrosion and Deposit Evaluation in Large Diameter Pipes. It will assist many NDT practitioners and users in Member States in the as sessment of remaining operating life, and to ensure the safe and efficient operation of industrial facilities. This report is intended for NDT specialists and managers of industry