Study of Probability of the Detection of Defects in Welded Joints of the Techniques of Magnetic Particle and Penetrant Testing. 1.

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1 More Info at Open Access Database Study of Probability of the Detection of Defects in Welded Joints of the Techniques of Magnetic Particle and Penetrant Testing. Ramon Fonseca Ferreira¹, Ricardo da Costa Teixeira 2, Lincoln Silva Gomes 3, Maurício Ogawa 4, Suzana Peripolli Botega 5, Agildo Badaró Moreira 6, Ricardo de Oliveira Carneval 7. 1, 2, 3, 4, 5 - SENAI Welding Technology Centre. São Francisco Xavier Street, 601, Maracanã, Rio de Janeiro, Brazil. ramonffrj@firjan.org.br. Phone number: / , 7 Search and Development Centre Leopoldo Américo Miguez de Mello CENPES/TMEC/PETROBRAS -. Horácio Macedo Avenue, 950, Ilha Do Fundão. Cidade Universitária - Rio de Janeiro Brazil. agildobm@petrobras.com.br, rocarneval@petrobras.com.br Abstract For many years, the non-destructive tests have been applied in the inspection of the most varied types of equipment such as an efficient way to evaluate the structural integrity. Actually, the highest levels of quality and operational safety are required in the modern industry. For this reason, new inspection technologies are being developed, but in many cases, don t have much information about reliability studies of the conventional techniques. The objective of the project was to develop a detection probability study of conventional non-destructive testing such as: magnetic particle inspection and penetrating liquid. In this study were made 25 welded samples with surface welding defects such as cracks. The inspection results were used to develop the curves of the POD (probability of detection). The project showed the detection capability of these two non-destructive testing for use in industry. 1. Introduction The industry of non-destructive tests is bringing in fast changes. Traditional technologies are evolving in important ways, offering new benefits and adding value to their end users. Applications in which the non-destructive testing is used are also evolving. Many industries, such as electronics, which used non-destructive testing techniques sparingly in the past, are showing increasing interest in using new and more advanced techniques, while some of the traditional non-destructive testing end users, such as the oil industry, gas and derivatives, and the automotive sector, are skeptical about adopting new advanced technologies, preferring the traditional techniques, which are more consolidated. The list of enterprises is great, and the expectation of Brazilian industry growth for years to come is as well. There are two sectors that are growing together, the welding and inspection sectors. The reliability studies are important to give for industries, procedures more adjusted to the application. The large application of the methods, penetrant testing and magnetic particles in many welded equipments, motivates the CTS Solda and PETROBRAS to develop a study of probability of detection, mapping the efficiency of same in locate and sizing the defects in welded samples.

2 2. Bibliography Review 2.1 Development of POD Curves (Probability of Detection) Any kind of techniques of detection of discontinuities, the non-destructive tests have their limitations and errors inherent in the implementation of each method, which come from factors of equipment and inspection parameters, or by human factors (fatigue, emotional state, training, experience, skill, etc). In this way, a few years ago that the pet studies of the reliability of nondestructive testing jobs in inspection equipment have been growing significantly [8]. The curves CAN formalize a methodology for estimating detection capability of an inspection method according to the size of the discontinuity, i.e. the curve POD shows the probability of detection of a defect as a function of its size for an inspection technique specifies. For an ideal technique, the POD for defects smaller than a critical size is zero, while the POD for some defects larger than this size is one (100%). In the ideal case, there will be no or false rejection of good parts (false positive), or false acceptance of defective parts (false negative). However, curves, POD for real testing techniques, are never so discriminatory as the ideal curve, and as a result there will be regions of uncertainty with false rejection and false acceptance. POD curve lifting the set of samples must have defects with dimensions, type and known locations and must be large enough to reproduce as close as possible to the real conditions of operation. Second Ch [8], the POD-of-a-kind feature dimension "a" is defined by the average detection probability of all broken dimension "a". This definition reflects the fact that the discoverability of cracks varies with a number of factors. Figure 2 illustrates an example of a PoD estimated curve for detection of lack of penetration in welding defect inspected by ultrasound. Figure 2.1: Example of PoD for curve detection of lack of penetration by ultrasonic method [4]. 3. Methodology 3.1 Materials The first part of the study involved the making of 25 specimens of top junta structural steel 36 [7], thickness of 3/8 "(~ 10 mm), with dimensions of 500 mm x 320 mm (Figure 1). Inserted in the weld were 5 defects, such as: cracks opened to the surface. Figure 3.1 Schematic Sketch of the specimens.

3.2 Inspection of specimens The specimens were inspected by Dye penetrant methods (colored and fluorescent) and magnetic particles (employing

In the inspection we had 10 qualified inspectors, with level II of the SNQC/ABENDI in both methods, where they were separated into two tracks of

We considered five inspectors on every track of experience for equalization of statistical distribution. (a) (b) (c) 3.

In the study were estimated curves for each method (LP and PM), including the results for the analysis of variables: white light and ultraviolet

For best pet of the curves with the margins of error, the Bootstrap technique [9] with sample replication, which works with the random drawing

3 3.2 Inspection of specimens The specimens were inspected by Dye penetrant methods (colored and fluorescent) and magnetic particles (employing Ioke, wet color techniques and fluorescent). In the inspection we had 10 qualified inspectors, with level II of the SNQC/ABENDI in both methods, where they were separated into two tracks of experience: - Experience after qualification 5 years. - Experience after qualification > 5 years. We considered five inspectors on every track of experience for equalization of statistical distribution. (a) (b) (c) 3.3 Preparation of Curves Figure 3.2 Inspection Step. In the study were estimated curves for each method (LP and PM), including the results for the analysis of variables: white light and ultraviolet light. The method employed in the development of the curves was (detects/does not detect), hit/miss [8]. For best pet of the curves with the margins of error, the Bootstrap technique [9] with sample replication, which works with the random drawing mechanism with spare, as describes CARVALHO [8]. After the inspections of penetrant testing and magnetic particles testing, the samples were inspected by computed radiograph to elaborate the template to use in the criteria of evaluation (figure 3.3). (d) Figure 3.3 Computed radiograph to elaborate the template. The hit miss analysis used a criteria extracted in the API RP 2X Standard, which describes the tolerance of detection and sizing of the defects.

4 The first step analyzed for each defect mapped by the inspectors was the capacity of detection. The API RP 2X Standard describes that the centerline location of indication is inside boundary of La, or within 1/2" of the actual centerpoint of La (whichever is greater), credit is awarded for proper positioning. Otherwise, no credit is awarded regardless of dimensional accuracy of the call (figure 3.3a). The second step analyzed for each defect describes that the W1 and L1 dimensions are indicated between one half and twice Wa and La, credit is awarded for L1 to a maximum length equal to La (figure 3.4b). Figure 3.4 Available conditions for detection and sizing. (a) First step criteria, (b) second step criteria. 4. Results and Discussions 4.1 POD curve of Liquid Fluorescent Penetrant Technique The result of the Fluorescent LP POD curve presented indications found 654 (hit) and 316 not found (miss), in this way, a POD of 90% for a length of mm. Figure POD Fluorescent Penetrant Test. 4.2 POD curve of Liquid Penetrant Colored technique The result of the curve presented Colored LP 731 POD found indications (hit) and 239 not found (miss), in this way, a POD of 90% for a mm length.

5 Figure 4.2 Colored Penetrant Test POD. 4.3 POD curve of Fluorescent magnetic particle technique The result of the Fluorescent PM POD curve presented 867 indications detected (hit) and 103 not detected (miss), in this way, a POD of 90% for a length of mm. Figure 4.3 POD Fluorescent Magnetic Particle. 4.4 POD curve of magnetic particle colored technique The result of the curve Color PM POD presented indications found 894 (hit) and 76 not found (miss), in this way, a POD of 90% to mm length.

5. Conclusions Figure 4.4 - POD colored magnetic particle.

6 5. Conclusions Figure POD colored magnetic particle. At the conclusion of the analysis of the curves it was observed that the colored magnetic particle technique had better behavior toward fluorescent magnetic particle technique. To be a more sensitive technique, the fluorescent technique needs some care at the time of your application, because these particles are smaller than the colored particle proportions, which causes false indications at contours of the welds, causing problems at the Inspector's report. However, both of the two techniques achieved good results for the POD curve. In all results, the best conditions were obtained by the inspectors with experience. 6. Acknowledgements To SENAI Welding Technology Centre internal incentive to research and develop projects. PETROBRAS/CENPES on trust and encouragement in the development of this study. 7. References 1. Silk, M G. The Reliability of Non-destructive Inspection. Assessing the Assessment of Structures under Stress. Adam Hilger, Bristol Wall, M. Wedgwood, F. A. Burch, S. Modeling of NDT Reliability (POD) and Applying Corrections for Human Factors. 7th ECNDT European Conference on Nondestructive Testing. Copenhagen, May, Forsyth, D. S. Fahr A. Leemans, D. V. et al. Development of POD from In-Service NDI Data. Quantitative Nondestructive Evaluation. Iowa, July, Topp, D. A. Dover, W. D. Reliability of Non-Destructive Inspection Test. Análisis de Riesgo y confiabilidad Estructural de Instalaciones Marinas. México, diciembre, Carvalho, A. A. Confiabilidade de Técnicas de Ensaios Não Destrutivos na Inspeção de Dutos Utilizados na Indústria do Petróleo. Tese de Doutorado. COPPE. Rio de Janeiro Nockemann, C. Heidt, H. H. Thomsen, N. Reliability in NDT: ROC Study of Radiographic Weld Inspections. C. Nockemann, H. Heidt and N. Thomsen. NDT&E International, vol. 24, n.5, October 1991.

7 7. Carvalho, A.A. Rebello, J.M.A. Silva, R.R. Sagrilo, L.V.S. Reliability of the Manual and Automatic Ultrasonic Technique in the Detection of Pipe Weld Defects. Insight, vol. 48, n.11, November Fücsök, F. Muller, C. Reliability of Routine Radiographic Film Evaluation An Extended ROC Study of the Human Factor. 8 th ECNDT, Barcelona Olin, B.D, Meeku, Willian Q. Application of Statistical Methods to Nondestructive Evaluation. Technometrics, vol. 38, n.2, 1996, p Carvalho, A. A., Sagrilo, L. V. S., Silva, I. C., et al. The POD Curve for the Detection of Planar Defects Using a Multi-Channel Ultrasonic System. Insight, Vol. 44, N. 10, p , Wall, M. Burch, S. Lilley, J. Human Factors in POD Modelling and Use of Trial Data. Insight, Vol. 51, N. 10, October Generazio, E.R. Directed Design of Experiments for Validating Probability of Detection Capability of NDE Systems. Review of Quantitative Nondestructive Evaluation. Vol.27, p , Burch, S.F., Stow, B.A., Wall, M. Computer Modelling for the Prediction of the Probability of Detection of Ultrasonic Corrosion Mapping. Vol. 4, n.12, Insight, pp , December Georgiou, G.A. PoD Curves, their Derivation, Application and Limitations. Vol. 49, n.7. Insight, p , Gandossi, L., Simola, K. Derivation and Use of Probability of Detection Curves in the Nuclear Industry. Insight, Vol. 52, n. 12, December, Schoefs, F., Clément, A., Nouy, A. Assessment of ROC curves for inspection of random fields. Structural Safety. Vol. 31, p , Sweeting, Trevor. Statistical Models for Nondestructive Evaluation. International Statistical Review. Vol. 63, n.2, p , Wall, M., Burch, S.F., Lilley, J. Review of Models and Simulators for NDT. Vol. 51, n.11, Insight, November 2009.

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