1、Validation of Procedures for Welding Inspection Using Computed Radiography Davi F.OLIVEIRA1,2,Joseilson R.NASCIMENTO2,Alessandra S.MACHADO2,Carla A.MARINHO3,Marcos AIUB4,Joo M.HOHEMBERGER4,Eduardo IGUCHI4,Ricardo T.LOPES2 1Physics Institute,State University of Rio de Janeiro.E-mail:davi.oliveirauerj
2、.br 2 Nuclear Instrumentation Laboratory,Federal University of Rio de Janeiro.E-mail:davilin.ufrj.br,joseilsonlin.ufrj.br,ricardolin.ufrj.br 3Leopoldo A.Miguez de Melo Research Center,CENPES/PETROBRAS 4SEQUI/PETROBRAS Abstract The introduction of digital radiography replacing conventional film radio
3、graphy is becoming a reality in the inspection of materials and equipment.For this to happen in the oil and natural gas industry with quality,it is necessary to qualify and validate Radiographic Inspection Procedures,in particular for welding.This work is part of a project that aims at producing a c
4、omparative study between the techniques of film and computed radiography(CR)applied to weld inspection.For this purpose,images using five CR systems available on the market were obtained with their respective phosphor plates.Radiographic tests were performed with film and computed radiography for SW
5、SI,DWSI and DWDI techniques.Test samples that consist of plates and steel pipes of different diameters and thickness were used.Radiographs were taken with X-ray and rays sources.The evaluation criteria for approval of the images were,namely,detectability(in comparison with film radiography)and the c
6、ompliance with specific image quality parameters(contrast,basic spatial resolution and signal to noise ratio normalized).As a result of this study,the equipments that were able to reach positive results for specific ranges of thickness had their procedures duly validated,and are therefore apt to car
7、ry out reliable inspections for defect detection.Keywords:Computed Radiography,Inspection Procedure Validation,Weld Inspection.1.Introduction In past few years,the use of digital radiography in replacing conventional film radiography is becoming a reality in the inspection of materials and equipment
8、.Computed Radiography(CR)is proving itself to be an efficient technique and has been gaining relevance as a method of inspection which has several advantages over film radiography,especially for applications in the Oil&Gas industry.However,the test procedures are based in experimentations of trial a
9、nd error due to the lack of an established methodology for choosing the parameters,as is the case with film radiography.Due to such lack of methodology,it is impossible to ensure that the CR technique is indeed able to detect the same types of defects as film radiography.In order for that to happen,
10、it is necessary to validate inspection procedures,especially for welds,so as to establish an equivalence of detectability when compared to the conventional technique 1.Computed Radiography equipment are currently being manufactured by several companies who aim at working with NDTs.Each manufacturer
11、produces its own phosphor plates,also known as imaging plates and IPs,according to their own specifications.All systems follow the same working principle,even though certain features may vary depending on the manufacturer,and that is the reason why it is of utmost importance to assess all responses
12、with regard to the sensitivity of detection of discontinuities,such as the ones which are often found on welded joints 2,3.11th European Conference on Non-Destructive Testing(ECNDT 2014),October 6-10,2014,Prague,Czech RepublicThus,the main purpose of this study was to develop and validate procedures
13、 using CR on welding inspections in real field situations by using three radiography techniques and comparing them with the same techniques applied in film radiography.2.Materials and methodology 2.1 Radiographic Testing Radiographic tests were performed with film and computed radiography for SWSI,D
14、WSI and DWDI techniques.Test samples that consist of plates and steel pipes of different diameters and thickness were used.The images were considered approved once they achieved the required values for the following image quality parameters 4-10:Basic Spatial Resolution(BSR),Signal to Noise Ratio No
15、rmalized(SNRN)and contrast,besides defect detectability equivalent to the conventional film technique.Figure 1 portraits the test samples employed in the experiment and figures 2 to 4 show an illustration of the setup for each technique.Figure 1 Test Samples Figure 2 SWSI Setup Figure 3 DWSI Setup F
16、igure 4 DWDI Setup Tables 1 to 3 show the test samples specifications,the exposure values and the image quality requirements for the three radiographic techniques.Table 1 Samples Specifications(SWSI).X-Rays -Rays Group Nominal Thickness(mm)Total Thickness(mm)High Voltage(kV)Isotope Wire IQI(ISO 19232-1)BSR(m)(N 2821-B)SNRN(N 2821-B)I 5.33 6.93 140 12 II 6.35 7.95 150 12 III 7.11 10.31 150 11 IV 9.53 12.73 160 10 V 12.70 15.90 190 Se-75 10 VI 18.26 22.26 225 9 VII 25.40 29.40 270 8 VIII 35.71 40.
