Abstract
As a part of the Direct Assessment goals the knowledge of the problems allows a better decision process. In this way, the use of these methodologies for the evaluation of metal corrosion phenomena increases the possibilities of pipeline integrity analysis; one of these new techniques is the guided waves application. Certain maritime terminals for oil distribution in Mexico have been making efforts in order to get more information about the pipeline integrity of its network, and several cases have been studied with this methodology. Our group has participated as corrosion evaluation specialist and the experiences have shown the necessity of extra information about the technique and the involved variables, so we have improved laboratory exercises to get that kind of data. The evaluation of pipeline integrity with the guided waves technology has become in a very useful tool for non ILI susceptible pipelines. The success of this technique is based on the capability of a continuous surface evaluation. This technique is based in the induction of mechanical vibration on the pipeline, and the evaluation of the reflections generated by the defects in both internal and external surfaces. Because the guided waves are mechanical vibrations propagated through the pipeline, there are many factors involved in its attenuation, such as the pipeline geometry, coatings, the product inside the pipeline and the physical characteristics of the soil or the water if the pipeline is buried or submerged.
Field experiences and laboratory tests performed using the Magnetostrictive technology, have been analyzed to determinate the effect of attenuation caused by some specific conditions of the pipeline, the environment and the operation parameters of the guided waves equipment. The application of the guided waves in operation docks in Northwest Pacific coast (Mazatlan), south Pacific coast (Acapulco) and southeast Gulf of Mexico (Lerma) where cases as generalized corrosion in external surfaces and pitting or certain coating types have represented a difficult for the technique application. These conditions have been reproduced in the laboratory to characterize the effect of this condition in the attenuation of the guided waves signal. In this work, we present evidence of the mentioned corrosion cases, which are determined by using the guided waves methodology; however we are focused to determine the effect of the different involved variables in the laboratory analysis, it means the consideration of parameters associated to the pipeline and to operational conditions. This combined analysis of both laboratory studies and site evaluations allow a complete reference about the capabilities of guided waves methodology and the perspectives for application in the pipeline network.
