NB/T 47013.14-2023 English PDF (NB/T47013.14-2023)

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NB/T 47013.14-2023: Nondestructive testing of pressure equipments - Part 14: X-ray computed radiographic testing
NB/T 47013.14-2023
NB
ENERGY INDUSTRY STANDARD OF
THE PEOPLE’S REPUBLIC OF CHINA
ICS 77.040.20
CCS H 26
Replacing NB/T 47013.14-2016
Nondestructive Testing of Pressure Equipment – Part 14:
Computed Radiographic Testing
ISSUED ON: OCTOBER 11, 2023
IMPLEMENTED ON: APRIL 11, 2024
Issued by: National Energy Administration
Table of Contents
Foreword ... 4
Introduction ... 7
1 Scope ... 8
2 Normative References ... 8
3 Terms and Definitions ... 9
4 General Requirements ... 12
5 Testing Process and Its Selection ... 18
6 Image Quality Requirements ... 30
7 Defect Identification and Measurement ... 36
8 Image Storage and Preservation ... 36
9 Evaluation of Inspection Results and Quality Grading ... 37
10 Testing Records and Reports ... 37
Appendix A (Informative) Test Method of Min. Grey Value ... 39
Appendix B (Normative) Determination of Resolution (Ratio) ... 41
Appendix C (Normative) Determination of Normalized Signal-to-Noise Ratio ... 44
Bibliography ... 45
Nondestructive Testing of Pressure Equipment – Part 14:
Computed Radiographic Testing
1 Scope
1.1 This Document specifies the radiographic computer-aided imaging inspection technology
and quality grading requirements for fusion welding joints of metal material pressure
components of pressure-bearing equipment. Metal materials used to make welding joints
include steel, copper and copper alloys, aluminum and aluminum alloys, titanium and titanium
alloys, nickel and nickel alloys.
1.2 This Document is applicable to the radiographic computer-aided imaging inspection of butt
welds of plates and tubes (hereinafter referred to as "butt welds") during the manufacture,
installation and in-service inspection of pressure components of pressure-bearing equipment.
1.3 The imaging device applicable to this Document is the imaging plate.
1.4 The radioactive source applicable to this Document is the X-ray source and the Ir192 and
Se75γ radioactive source, where the maximum tube voltage of the X-ray machine does not
exceed 600kV.
1.5 The radiographic computer-aided imaging inspection of welding joints of pressure-bearing
equipment supports and structural parts and plug-in and placement tubes can be used as a
reference.
2 Normative References
The provisions in following documents become the essential provisions of this Document
through reference in this Document. For the dated documents, only the versions with the dates
indicated are applicable to this Document; for the undated documents, only the latest version
(including all the amendments) is applicable to this Document.
GB/T 14058 Apparatus for gamma radiography
GB/T 21356 Non-destructive testing - Qualification and long-term stability of computed
radiology systems
GB/T 23901.1 Non-destructive testing - Image quality of radiographs - Part 1:
Determination of the image quality value using wire-type image quality indicators
spacing of the laser scanner scanning the imaging plate, and the ratio of the laser point scanning
speed to the operating frequency of the analog-to-digital converter.
3.16 Signal-to-noise ratio (SNR)
In a digital image, the ratio of the linearized grey mean to the standard deviation of a selected
area.
3.17 Normalized signal-to-noise ratio (SNRn)
Signal-to-noise ratio that is normalized based on resolution ratio.
3.18 Penetrated thickness (W)
The nominal thickness of the material in the direction of the ray penetration. In case of multi-
layer penetration, the penetrated thickness is the sum of the nominal thickness of each layer of
material.
3.19 Effective length of a single exposure
The maximum effective testing length of a single exposure is in accordance with the standard.
3.20 Ratio between max. and min. penetrated thicknesses (K)
The ratio of the maximum thickness and the minimum thickness of the parent material that the
radiation beam penetrates within an effective length of a single exposure is also called the ratio
between max. and min. penetrated thicknesses.
3.21 Digital image processing
Methods and techniques for processing digital images by computers.
3.22 Standard sample
A specimen of known size that is used to calibrate the size of features in an image.
3.23 Raw image
The image that is formed by the latent image on the imaging plate is scanned by a scanner.
3.24 Round flaw
Volume defects such as pores, slag inclusions and tungsten inclusions with an aspect ratio of
no more than 3.
3.25 Stripy flaw
Volume defects such as pores, slag inclusions and tungsten inclusions with an aspect ratio of
requirements. The system performance testing conditions and testing methods shall be
implemented in accordance with the provisions of GB/T 21356. The system shall at least meet
the following performance indicators:
a) The image geometric distortion rate shall be less than ±2%;
b) There shall be no jitter or sliding between the scanner and the imaging plate, or the jitter
shall be lower than the system noise level;
c) On the same horizontal line of the image, the grey change rate between the center area
and the edge background shall not exceed ±10%;
d) Other performance indicators include signal-to-noise ratio, laser beam function, shadow,
image erasure, artifacts, etc.
4.2.3.1 Imaging plate
The supplier shall provide the quality certification documents of the imaging plate, which shall
at least include the type and specifications, excitation response time, chemical composition and
other main performance parameters of the imaging plate. Users shall use and store it according
to the temperature and humidity conditions recommended by the manufacturer, and avoid
unnecessary exposure.
4.2.3.2 Scanner
The supplier shall provide the quality certification documents of the scanner, which shall at
least include the specifications, scanning size, photomultiplier tube voltage or gain, scanning
resolution ratio, laser beam focus size and other main performance parameters; and its functions
and performance shall at least meet the following requirements:
a) The scanner shall have the scanning and erasing functions, and the residual latent image
grey value after erasing shall not exceed 5% of the maximum greyscale of the system;
b) The scanning laser power shall meet the requirements of signal acquisition;
c) The photomultiplier tube voltage or gain and scanning resolution ratio of the scanner shall
be adjustable;
d) The laser beam shall be free of vibration, and there shall be no artifacts or scanning line
loss.
4.2.4 Computer system
The basic configuration of the computer system is determined according to the performance
and scanning speed requirements of the adopted CR system. It should be equipped with a
memory of no less than 512MB, a hard disk of no less than 40GB, a high-brightness and high-
resolution ratio display, a CD writer, a network card, etc.
The display shall meet the following minimum requirements:
a) Minimum brightness of 250 cd/m2;
b) The display has at least 256 grey levels;
c) The minimum displayable light intensity ratio is 1:250;
d) The display has at least 1M pixels and the pixel size is less than 0.3 mm.
4.2.5 System-specific software
4.2.5.1 The system software is the core unit of the computed radiographic testing system, which
controls the scanner to complete the conversion of the imaging plate acquisition information to
the digital image, as well as the functions of latent image erasure, image storage, auxiliary
evaluation, and annotation, etc.
4.2.5.2 It should have the function of converting multiple image formats.
4.2.5.3 It shall have the measurement functions of greyscale, resolution ratio, signal-to-noise
ratio, geometric dimensions, etc.
4.2.5.4 It shall have functions such as greyscale conversion, contrast and brightness adjustment,
and image zoom, etc.
4.2.5.5 It shall have the functions of browsing and searching for information related to the
collected image.
4.2.5.6 The test report can be automatically generated.
4.2.6 Image quality indictor
4.2.6.1 The image quality indicators used in this Document include wire type image quality
indictors and duplex wire type image quality indicators. The supplier of the image quality
indicator shall provide corresponding quality certification documents.
4.2.6.2 Wire type image quality indicator
a) The wire type image quality indicator is used to measure image sensitivity, including
general wire type image quality indicator and equal-diameter wire type image quality
indicator. Its model and specification shall comply with the provisions of GB/T 23901.1
and JB/T 7902, respectively;
b) The material code, material of the wire type image quality indicator, and material range
of inspected object applicable to the wire type image quality indicators made of different
materials shall be as specified in Table 1. The absorption coefficient of the wire type
image quality indicator shall be the same as or similar to that of the tested material, and
4.3 Testing technology level
4.3.1 The computed radiographic testing technology level specified in this Document is divided
into three levels from low to high: A, AB and B.
4.3.2 The selection of the testing technology level shall meet the requirements of relevant laws,
regulations, standards and design technical documents, and shall also meet other technical
requirements agreed upon by the contracting parties. For the butt welds of pressure-bearing
equipment, it is generally recommended to use Level-AB testing technology for testing. For
important equipment and structures, as well as butt welds made of special materials and special
welding processes, Level-B testing technology should be used for testing.
4.3.3 When certain testing conditions cannot meet the requirements of Level-AB (or Level-B)
testing technology, the contract parties agree that, on the premise of effective compensation
measures (such as increasing exposure or selecting a CR system with a higher signal-to-noise
ratio, etc.) is taken, if the image quality reaches the requirements of Level-AB (or Level-B)
testing technology, it can be considered that the testing is carried out according to Level-AB
(or Level-B) testing technology.
4.3.4 If the source-to-object distance f does not meet the requirements of 5.6 during the testing,
the provisions of 4.3.3 are not applicable.
4.3.5 When certain conditions for the testing of pressure-bearing equipment cannot meet the
requirements of Level-AB testing technology, the contract parties agree that, on the premise of
effective compensation measures (such as increasing exposure or selecting a system with a
higher signal-to-noise ratio, etc.) is taken, Level-A testing technology can be used for testing;
and other non-destructive testing methods should be used for supplementary testing at the same
time.
4.4 Testing process documents
4.4.1 Testing process documents include process procedures and operating instructions.
4.4.2 In addition to meeting the requirements of NB/T 47013.1, the process procedures shall
also specify the specific scope or requirements of the following related factors. If the changes
in related factors exceed the provisions, the process procedures shall be re-compiled or revised.
a) Applicable structure, material type and thickness;
b) Radioactive source energy range and focal size;
c) Testing technology level;
d) Testing process (transillumination method, transillumination parameters, geometric
parameters);
e) Testing equipment (type, specification, main technical parameters);
f) Image quality requirements.
4.4.3 The operation instructions shall be prepared according to the contents of the process
specification and the testing requirements of the inspected object. In addition to meeting the
requirements of NB/T 47013.1, the contents shall at least include:
a) Testing equipment: radioactive source (type, specification, focus or source size), imaging
plate and scanner (type, specification), testing software, metal screen (type and
thickness), image quality indicator (type and model), backscatter shielding lead plate,
marking, standard sample, etc.
b) Testing technology level.
c) Testing process: transillumination method, transillumination parameters (including tube
voltage, exposure), geometric parameters, scanner parameters.
d) Testing mark.
e) Image quality requirements: grayscale range, image resolution ratio, image sensitivity,
normalized signal-to-noise ratio.
f) Acceptance standard.
g) Process verification image No.
4.4.4 Process verification
4.4.4.1 The operating instructions for the first use shall be subject to process verification to
verify whether the image quality can meet the specified requirements in the standard.
4.4.4.2 Process verification can be carried out by using a comparison specimen through a
special transillumination test, or by using the first batch of images of the product as the basis
for verification. In both cases, the verification images used as the basis shall be marked.
4.4.4.3 The placement of the radioactive source shall be ensured to be consistent with the actual
test.
4.4.4.4 wire type and duplex wire type image quality indicators shall be placed; and the
placement of the wire type image quality indicator shall be consistent with the actual test.
4.4.4.5 The duplex wire type image quality indicator shall be placed on the parent material of
the inspected object close to the weld, with the angle between the length direction and the row
or column of the detector being 2°~5°; and the Value-b being larger. When the material types
of the weld are different, it shall be placed on the surface of the inspected object of the material
with the largest attenuation coefficient. The placement orientation is shown in the example of
Figure 1 (positive film); and the image resolution ratio in the four directions of the top, bottom,
left and right of the imaging center area shall meet the requirements. When using the center
transillumination is performed for 2 times at 90° intervals; when T/D0 > 0.12, transillumination...