ISO 17636-2:2022
Non-destructive testing of welds — Radiographic testing — Part 2: X- and gamma-ray techniques with digital detectors
This document specifies techniques of digital radiography with the object of enabling satisfactory and repeatable results. The techniques are based on generally recognized practice and fundamental theory of the subject.
This document applies to the digital radiographic testing of fusion welded joints in metallic materials. It applies to the joints of plates and pipes. Besides its conventional meaning, “pipe”, as used in this document, covers other cylindrical bodies such as tubes, penstocks, boiler drums and pressure vessels.
This document specifies the requirements for digital radiographic X- and gamma-ray testing by either computed radiography (CR) or radiography with digital detector arrays (DDAs) of the welded joints of metallic plates and tubes for the detection of imperfections. It includes manual and automated inspection with DDAs.
Digital detectors provide a digital grey value image which can be viewed and evaluated using a computer (Annex E). This document specifies the recommended procedure for detector selection and radiographic practice. Selection of computer, software, monitor, printer and viewing conditions are important, but are not the main focus of this document. The procedure specified in this document provides the minimum requirements for radiographic practice which permits exposure and acquisition of digital radiographs with equivalent sensitivity for the detection of imperfections as film radiography (specified in ISO 17636-1).
This document does not specify acceptance levels for any of the indications found on the digital radiographs. ISO 10675 provides information on acceptance levels for weld inspection.
If contracting parties apply lower test criteria, it is possible that the quality achieved will be significantly lower than when this document is strictly applied.
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Foreword
1 Scope
2 Normative references
3 Terms and definitions
4 Symbols and abbreviated terms
5 Classification of radiographic techniques and compensation principles
5.1 Classification
5.2 Compensation principles, CP I, CP II or CP III
5.2.1 General
5.2.2 Compensation principle I (CP I)
5.2.3 Compensation principle II (CP II)
5.2.4 Compensation principle III (CP III)
5.2.5 Theoretical background
6 General preparations and requirements
6.1 Protection against ionizing radiation
6.2 Surface preparation and stage of manufacture
6.3 Location of the weld in the radiograph
6.4 Identification of radiographs
6.5 Marking
6.6 Overlap of digital images
6.7 Types and positions of image quality indicators (IQIs)
6.7.1 General
6.7.2 Duplex wire IQIs
6.7.3 Single wire or step-hole IQIs
6.8 Evaluation of image quality
6.9 Minimum image quality values
6.10 Personnel qualification
7 Recommended techniques
7.1 Test arrangements
7.1.1 General
7.1.2 Single-wall penetration of plane objects (see Figure 1)
7.1.3 Single-wall penetration of curved objects with the source outside the object (see Figures 2 to 4)
7.1.4 Single-wall penetration of curved objects with the source inside the object for panoramic exposure (see Figures 5 to 7)
7.1.5 Single-wall penetration of curved objects with the source located off-centre and inside the object (see Figures 8 to 10)
7.1.6 Double-wall penetration and double-image evaluation (DWDI) of pipes with the elliptic technique and the source and the detector outside the object (see Figure 11)
7.1.7 Double-wall penetration and double-image evaluation (DWDI) with the perpendicular technique and source and detector outside the object (see Figure 12)
7.1.8 Double-wall penetration and single-image evaluation (DWSI) of curved objects for evaluation of the wall next to the detector (see Figures 13 to 16)
7.1.9 Penetration of objects with different material thicknesses (see Figure 17 to 19)
7.2 Choice of tube voltage and radiation source
7.2.1 X-ray devices up to 1 000 kV
7.2.2 Other radiation sources
7.3 Detector systems and metal screens
7.3.1 Minimum normalized signal-to-noise ratio (SNRN)
7.3.2 Compensation principle II
7.3.3 Metal screens for IPs and shielding
7.4 Alignment of beam
7.5 Reduction of scattered radiation
7.5.1 Metal filters and collimators
7.5.2 Interception of backscattered radiation
7.6 Source-to-object distance
7.7 Geometric magnification technique
7.8 Maximum area for a single exposure
7.9 Processing
7.9.1 Scan and read-out of images
7.9.2 Correction of acquired DDA images
7.9.3 Bad pixel interpolation
7.9.4 Image processing
7.10 Monitor viewing conditions and storage of digital radiographs
8 Test report
Annex A (normative) Number of exposures for acceptable testing of a circumferential butt weld
Annex B (normative) Minimum image quality values
Annex C (normative) Determination of basic spatial resolution
Annex D (informative) Determination of minimum grey values for CR practice
Annex E (informative) Grey values — General remarks
Annex F (informative) Considering the detector unsharpness for fmin
Annex G (informative) Calculation of recommended X-ray tube voltages from Figure 20
Bibliography
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Foreword
1 Scope
2 Normative references
3 Terms and definitions
4 Symbols and abbreviated terms
5 Classification of radiographic techniques and compensation principles
5.1 Classification
5.2 Compensation principles, CP I, CP II or CP III
5.2.1 General
5.2.2 Compensation principle I (CP I)
5.2.3 Compensation principle II (CP II)
5.2.4 Compensation principle III (CP III)
5.2.5 Theoretical background
6 General preparations and requirements
6.1 Protection against ionizing radiation
6.2 Surface preparation and stage of manufacture
6.3 Location of the weld in the radiograph
6.4 Identification of radiographs
6.5 Marking
6.6 Overlap of digital images
6.7 Types and positions of image quality indicators (IQIs)
6.7.1 General
6.7.2 Duplex wire IQIs
6.7.3 Single wire or step-hole IQIs
6.8 Evaluation of image quality
6.9 Minimum image quality values
6.10 Personnel qualification
7 Recommended techniques
7.1 Test arrangements
7.1.1 General
7.1.2 Single-wall penetration of plane objects (see Figure 1)
7.1.3 Single-wall penetration of curved objects with the source outside the object (see Figures 2 to 4)
7.1.4 Single-wall penetration of curved objects with the source inside the object for panoramic exposure (see Figures 5 to 7)
7.1.5 Single-wall penetration of curved objects with the source located off-centre and inside the object (see Figures 8 to 10)
7.1.6 Double-wall penetration and double-image evaluation (DWDI) of pipes with the elliptic technique and the source and the detector outside the object (see Figure 11)
7.1.7 Double-wall penetration and double-image evaluation (DWDI) with the perpendicular technique and source and detector outside the object (see Figure 12)
7.1.8 Double-wall penetration and single-image evaluation (DWSI) of curved objects for evaluation of the wall next to the detector (see Figures 13 to 16)
7.1.9 Penetration of objects with different material thicknesses (see Figure 17 to 19)
7.2 Choice of tube voltage and radiation source
7.2.1 X-ray devices up to 1 000 kV
7.2.2 Other radiation sources
7.3 Detector systems and metal screens
7.3.1 Minimum normalized signal-to-noise ratio (SNRN)
7.3.2 Compensation principle II
7.3.3 Metal screens for IPs and shielding
7.4 Alignment of beam
7.5 Reduction of scattered radiation
7.5.1 Metal filters and collimators
7.5.2 Interception of backscattered radiation
7.6 Source-to-object distance
7.7 Geometric magnification technique
7.8 Maximum area for a single exposure
7.9 Processing
7.9.1 Scan and read-out of images
7.9.2 Correction of acquired DDA images
7.9.3 Bad pixel interpolation
7.9.4 Image processing
7.10 Monitor viewing conditions and storage of digital radiographs
8 Test report
Annex A (normative) Number of exposures for acceptable testing of a circumferential butt weld
Annex B (normative) Minimum image quality values
Annex C (normative) Determination of basic spatial resolution
Annex D (informative) Determination of minimum grey values for CR practice
Annex E (informative) Grey values — General remarks
Annex F (informative) Considering the detector unsharpness for fmin
Annex G (informative) Calculation of recommended X-ray tube voltages from Figure 20
Bibliography