Comparação entre os ensaios não destrutivos RFT e IRIS em feixes tubulares de aço carbono de trocadores de calor do tipo casco & tubos

Abstract

Refineries constitute an industry sector that transforms crude oil into essential products for daily use by the population. Among the essential equipment that make up a refinery and that act directly in oil refining are the heat exchangers, intended for thermal exchange and/or reuse of energy. When it comes to crucial equipment for refining, has some technique to inspection them, including the use of NonDestructive Testing (NDT). Such tests allow carrying out the inspection without compromising the integrity of the equipment. Heat exchangers are generally composed of tube bundles, which are the components that exchange heat with the operating environment, and they can suffer various damages throughout the operation, including erosion and corrosion. There are some non-destructive inspection methods for tube bundles, and currently the most used is IRIS (Internal Rotary Inspection System), which is based on the use of ultrasound, allowing good visibility of the discontinuities occurring in the tubes, but with low speed and high cost of procedure. Therefore, with the purpose of seeking better options for the inspection of tube bundles, this work aims to study the RFT (Remote Field Testing) test, an electromagnetic technique based on eddy currents, with higher inspection speed and lower procedure cost, however less employed. Thus, after a bibliographical survey and training in the RFT technique, a study was carried out on the parameters of this test that most influence the inspection results and, finally, its results were compared with the IRIS using tubes with discontinuities produced in laboratory and carbon steel tubes from Hull & Tubes heat exchangers provided by a refinery. In this comparison, the results of the RFT technique were confronted with those of the IRIS technique (considered the standard test) in order to measure the degree of equivalence between the two techniques. At the end, destructive measurements were also made with the aid of a 3D scanner as a complement to the equivalence analysis between the non-destructive techniques. As a main conclusion, it can be said that the RFT technique is equivalent to the IRIS technique in terms of the ability to detect and characterize thickness losses of tubes in Hull & Tube heat exchangers, despite requiring greater effort from the inspector to analyze the results.