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NB/T 47013.11-2015

Chinese Standard: 'NB/T 47013.11-2015'
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Detail Information of NB/T 47013.11-2015; NB/T47013.11-2015
Description (Translated English): Nondestructive testing of pressure equipments - Part 11: Standard practice for X-ray digital radiography
Sector / Industry: Energy Industry Standard (Recommended)
Classification of Chinese Standard: H26
Word Count Estimation: 26,217
Date of Issue: 2015-04-02
Date of Implementation: 2015-09-01
Regulation (derived from): ?Energy Bureau Announcement 2015 No. 3

NB/T 47013.11-2015
ENERGY INDUSTRY STANDARD OF
THE PEOPLE’S REPUBLIC OF CHINA
ICS 77.040.20
H 26
Nondestructive testing of pressure equipment -
Part 11: Standard practice for X-ray digital radiography
承压设备无损检测
第 11部分: X射线数字成像检测
[Including Modification 2018XG1]
ISSUED ON: APRIL 2, 2015
IMPLEMENTED ON: SEPTEMBER 1, 2015
Issued by: National Energy Administration
Table of Contents
Foreword ... 3 
1 Scope ... 5 
2 Normative references ... 5 
3 Terms and definitions ... 6 
4 General requirements ... 8 
5 Testing methods ... 12 
6 Image quality and evaluation ... 18 
7 Testing result assessment and quality grading (acceptance) ... 27 
8 Image preservation and storage ... 27 
9 Testing records and reports ... 27 
Annex A (Normative) Verification method of the system resolution ratio ... 29 
Annex B (Informative) Typical trans-illumination modes ... 31 
Annex C (Normative) Recognition of the image quality indicator (duplex wire
type) ... 34 
Annex D (Normative) Normalized SNR test method ... 36 
Annex E (Informative) Format of the testing report ... 37 
Modification Notification of Industry Standard NB/T 47013.11-2015 (2018XG1)
... 39 
Foreword
This Standard NB/T 47013 Nondestructive testing of pressure equipment is
divided into the following 13 parts:
— Part 1: General requirements;
— Part 2: Radiographic testing;
— Part 3: Ultrasonic testing;
— Part 4: Magnetic particle testing;
— Part 5: Penetrant testing;
— Part 6: Eddy current testing;
— Part 7: Visual examination;
— Part 8: Leak testing;
— Part 9: Acoustic emission testing;
— Part 10: Ultrasonic time of flight diffraction technique;
— Part 11: Standard practice for X-ray digital radiography;
— Part 12: Magnetic flux leakage testing;
— Part 13: Pulsed eddy current testing.
This Part is Part 11 of NB/T 47013: Standard practice for X-ray digital
radiography.
This Part was drafted in accordance with the provisions given in GB/T 1.1-2009
Directives for standardization - Part 1: Structure and drafting of standards.
This Standard was proposed by and shall be under the jurisdiction of the
National Technical Committee for Standardization of Boiler and Pressure
Vessels (SAC/TC 262).
Drafting organizations of this Part: China Special Equipment Inspection and
Research Institute, Guangdong Yingquan Steel Products Co., Ltd, Special
Equipment Safety Supervision Inspection Institute of Jiangsu Province, Special
Equipment Safety Supervision Bureau of General Administration of Quality
Supervision Inspection and Quarantine of the People’s Republic of China, North
University of China, Beihang University, Sichuan Ruidi X-ray Digital Imaging
Technology Co., Ltd, National X-ray Digital Imaging Instrument Center, Sichuan
Chuanguo Boiler Co., Ltd, Beijing Jiasheng Guoan Technology Co., Ltd, and
Chengdu Huayu Inspection Technology Co., Ltd.
Main drafters of this Part: Liang Lihong, Lin Shuqing, Ding Keqin, Zeng
Xiangzhao, Qiang Tianpeng, Zheng Hui, Chen Guang, Wang Xiaomei, Xiu
Changzheng, Han Yan, Fu Jian, Xiang Qian, Chen Hao, Yan Chunsong, Shuai
Jiasheng, and Tang Liangming.
This Part is first formulated.
Nondestructive testing of pressure equipment - Part
11: Standard practice for X-ray digital radiography
1 Scope
1.1 This Part of NB/T 47013 specifies the X-ray digital radiographic testing
technology and quality grading requirements of fusion welded joints for metal
pressure parts of pressure equipment.
1.2 This Part is applicable to the manufacturing and installation of pressure
parts of pressure equipment as well as the X-ray digital radiographic testing of
welded joints in testing. For the metal materials used to make welded joints,
including steel, copper and its alloys, aluminum and its alloys, iron and its alloys,
nickel and its alloys, this Part shall also apply.
1.3 A digital detector shall be used as the imaging device in this Part. The
applicable X-ray machine shall have a maximum tube voltage of not exceeding
600kV.
1.4 For the X-ray digital radiographic testing of welded joints for relevant
supporting members and structural members of pressure equipment, this Part
may be used for reference.
2 Normative references
The following documents are essential to the application of this document. For
dated references, only the editions with the dates indicated are applicable to
this document. For undated references, only the latest editions (including all the
amendments) are applicable to this document.
GB 18871 Basic standards for protection against ionizing radiation and for
the safety of radiation sources
GB/T 23901.1 Non-destructive testing - Image quality of radiographs - Part
1: Image quality indicators (wire type) - Determination of image quality value
GB/T 23901.5 Non-destructive testing - Image quality of radiographs - Part
5: Image quality indicators (duplex wire type) - Determination of image
unsharpness value
GB/T 23903 Resolution indicators for ray image
GBZ 117 Radiological protection standards for industrial X-ray detection
NB/T 47013.1 Nondestructive testing of pressure equipment - Part 1:
General requirements
NB/T 47013.2 Nondestructive testing of pressure equipment - Part 2:
Radiographic testing
3 Terms and definitions
For the purposes of this Part, the terms and definitions defined in NB/T 47013.1
and the following ones apply.
3.1 Pixel
Basic components of X-ray digital images. X-ray digital images are made up of
dots. Each dot that makes up an image is called a pixel.
3.2 Image sensitivity
The ability of the testing system to discover the smallest details in the image of
the tested object.
3.3 Resolution ratio
The ability of distinguishing the minimum distance between two adjacent details
per unit length, expressed in 1p/mm.
3.4 Resolution
Resolution capability of the minimum distance between two adjacent details.
3.5 System resolution ratio
The ability of the testing system to distinguish the minimum distance between
two adjacent details per unit length, when the geometric magnification of trans-
illumination is close to 1, in the absence of a tested object, reflecting the
characteristics of the testing system itself, also known as the system’s basic
spatial resolution ratio.
3.6 Image resolution ratio
The ability of the testing system to distinguish the minimum distance between
two adjacent details per unit length in the image of the tested object, also known
as the image’s spatial resolution ratio.
3.7 Digital detector
An electronic device that converts X-ray photons into digital signals, hereinafter
referred to as the detector.
3.8 Gray level
A quantitative description of the brightness of a black-and-white image obtained
by an X-ray digital radiography system, which is determined by the number of
bits in the system’s A/D converter (analog-to-digital converter). The higher the
bits of the A/D converter, the higher the gray level. For instance, in the case of
a 12-bit A/D converter, the gray level acquired is 212 = 4 096.
3.9 Dark image
An image that is output in the absence of X-ray trans-illumination, also known
as the dark current image.
3.10 Dynamic range
The ratio of the maximum gray level of the X-ray digital radiography system to
the standard deviation of the dark image within the linear output range.
3.11 Non-uniform responsivity
The inherent characteristics of the detector. The output image brightness is
presented with non-uniform fringe due to the inconsistent response of the
detector to the X-rays, under the condition of uniform trans-illumination of
homogeneous objects or blank screen.
3.12 Bad pixel
The occurrence of white or black dots in a dark image that are either much
higher or much lower than the gray level of an adjacent pixel, also referred to
the situation that the output value of the corrected image is far away from the
outlier of the image mean. Bad pixels exist in the form of a single point, two
adjacent points and multiple adjacent points, a few rows or a few columns.
3.13 Signal noise ratio (SNR)
The ratio of the mean value of the signal to the standard deviation of the signal
in the ROI image.
3.14 Static imaging
X-ray digital radiography when there is no relative continuous motion between
the testing system and the tested object. The imaging results are presented in
a single image.
3.15 Dynamic imaging
X-ray digital radiography when there is relative continuous motion between the
testing system and the tested object. The imaging results are presented in a
sequential image.
3.16 Limiting resolution
The maximum resolution of the testing system, in the absence of physical
(geometric) amplification.
3.17 Digital image processing
Digital transformation method for improving the contrast, resolution ratio and
detail recognition capability of X-ray digital radiography.
3.18 Non-planar object
Other objects described in this Part except for the planar object.
4 General requirements
4.1 Testing personnel
4.1.1 Personnel engaged in X-ray digital radiographic testing shall receive the
training on radiation safety knowledge prior to work, and obtain the Radiologic
Worker Certificate.
4.1.2 Personnel engaged in X-ray digital radiographic testing shall obtain the
special qualification for X-ray digital radiography in nondestructive testing of
special equipment, before testing the corresponding items.
4.1.3 Testing personnel shall understand the computer and digital image
processing knowledge related to the X-ray digital radiography, and shall master
basic computer operation methods accordingly.
4.2 Testing system
4.2.1 X-ray machine
4.2.1.1 The energy range of the X-ray machine shall be selected based on
the thickness and material of the tested object as well as the focal length.
4.2.1.2 The selected focus shall match the detector in use.
4.2.2 Detector system
4.2.2.1 It includes the planar array detector, linear array detector and their
accessories.
4.2.2.2 The dynamic range shall not be less than 2 000: 1.
4.2.2.3 The bits of the A/D converter shall not be less than 12bit.
4.2.2.4 The detector supplier shall provide the bad pixel table and bad pixel
correction method along with the detectors.
4.2.2.5 The detectors shall be corrected in accordance with the specific image
correction method specified by the detector system.
4.2.3 Computer system
The basic configurations of the computer system shall be determined according
to the performance and speed requirements of the X-ray digital radiographic
components. The computer system should be equipped with a RAM of not less
than 512MB, a hard drive of not less than 40GB, a high-brightness high-
resolution display, a recorder, a network card, etc.
The display shall meet the following minimum requirements:
a) Brightness shall not be less than 250cd/m2;
b) Gray level shall not be less than 8bit;
c) Image display resolution shall not be less than 1 024 × 768;
d) The display’s pixel pitch shall not be greater than 0.3mm.
4.2.4 System software requirements
4.2.4.1 The system software is the core unit of the X-ray digital radiography
system, with the functions such as image acquisition, image processing, defect
geometric dimension measurement, defect marking, image storage, auxiliary
evaluation, testing report printing and other auxiliary functions, which is an
important factor to ensure the testing accuracy and safety.
4.2.4.2 It shall include basic digital image processing functions such as
superimposed noise reduction, adjustment of window width and window level,
contrast enhancement, etc.
4.2.4.3 It shall include such functions as SNR measurement, defect marking,
size measurement and size calibration.
4.2.4.4 It should have a magnification of not less than 4 times.
4.2.4.5 It shall be able to browse and search the relevant information of the
acquired images.
4.2.4.6 The test report may be generated according to the evaluation results.
4.2.4.7 The original images shall be stored. It is allowed to process
accordingly during observation and evaluation.
4.2.4.8 Smoothing and other means of image processing of the original
images shall be agreed upon by both parties and recorded in the relevant
documents.
4.2.4.9 Other special requirements shall be determined through consultation
by both parties.
4.2.5 Testing tooling
4.2.5.1 It shall be designed according to the tested object and meet the testing
requirements.
4.2.5.2 The carrying capacity of the testing tooling shall be selected according
to the weight of the tested object.
4.2.5.3 It should have such functions as translation, rotation, continuous
adjustable speed, etc., and shall ensure high operating accuracy and stability.
4.2.5.4 The motion of the testing tooling shall be synchronized with the data
acquisition of the detector.
4.2.5.5 For the testing of in-service equipment, the testing instruments and
equipment shall be fixed in a reasonable manner according to the site
environment and testing conditions.
4.2.6 Acceptance and verification of the testing system
4.2.6.1 The performance test certificates of the testing system shall be
provided. Prior to the first use, the testing system shall be conducted with
performance acceptance. It may be used only after acceptance.
4.2.6.2 Verification shall be carried out in the following cases. Verification
mainly refers to the testing of system resolution ratio. The verification method
shall be in accordance with Annex A.
a) when there is a change in the testing system;
b) under normal operating conditions, it shall be verified at least once every
three months;
c) when the system is reused one month after it is out of use.
4.3 Testing technology levels
The levels of X-ray testing technology specified in this Part are divided as
follows: Level AB - medium-sensitivity technology; Level B - high-sensitivity
technology.
4.4 Testing process documents
4.4.1 The testing process documents include the process procedures and
operating instructions.
4.4.2 The contents of the process procedures shall meet not only the
requirements of NB/T 47013.1, but also the specific range or requirements of
relevant factors listed in Table 1. In the event of changes in relevant factors
beyond the requirements, the process procedures shall be re-prepared or
revised.
Table 1 -- Relevant factors involved in the process procedures
Serial No. Relevant factors
1 Type and specifications (shape, size, wall thickness and material) of the tested object
2 Pursuant regulations and standards
3 Testing equipment and calibration, verification, operational verification or inspection requirements
4 Testing process (trans-illumination modes, trans-illumination parameters, geometric parameters, motion parameters, etc.)
5 Testing technologies
6 Process test report
7 Defect evaluation and quality grading
4.4.3 The operating instructions shall be prepared according to the contents
of the process procedures and the testing requirements of the tested object.
The contents shall not only meet the requirements of NB/T 47013.1, but also
include:
a) testing technology levels;
b) testing equipment [including the X-ray machine (specifications), detector
(specifications), filter board, image quality indicator, marks, testing tooling,
computer, display, system software, etc.];
c) testing process parameters (including the tube voltage, exposure,
geometric parameters of trans-illumination, material and thickness of the
filter board, relative position of the testing equipment and the testing area,
motion form and speed of the tested object, trans-illumination modes, etc.);
d) requirements for the testing identification;
e) operating procedures of testing;
f) testing records;
g) image evaluation (including the gray level, signal noise ratio, image
resolution ratio, image sensitivity, marks, etc.);
h) testing quality rating.
4.4.4 Process verification of the operating instructions
4.4.4.1 The operating instructions shall be conducted with process verification
prior to the first application.
4.4.4.2 The verification modes may be carried out by using an image quality
indicator, simulation test block or actual testing object.
4.4.4.3 Verification may be carried out through a special trans-illumination test,
or may use the first batch of images of the product as a basis for verification. In
both cases, the verification images to be based shall be identified.
4.5 Safety requirements
4.5.1 The testing environment shall meet the requirements of system
operation for the environment (temperature, humidity, grounding,
electromagnetic radiation, vibration, etc.).
4.5.2 The X-ray radiation protection conditions shall meet the relevant
requirements of GB 18871 and GBZ 117.
4.5.3 In the case of X-ray digital radiographic testing on the site, the control
area and the management area shall be delineated in accordance with the
requirements of GBZ 117. The warning signs shall be set as well. The testing
personnel shall wear a personal dosimeter and carry a dose alarm device.
5 Testing methods
5.1 Trans-illumination modes
5.1.1 Appropriate trans-illumination modes shall be selected according to the
structural characteristics of the tested object and the requirements for technical
conditions. GIVE priority to the single-wall trans-illumination mode. Double-wall
trans-illumination mode is allowed only when the single-wall trans-illumination
cannot be carried out. REFER to Annex B for typical trans-illumination modes.
5.1.2 When dynamic imaging mode is used for image acquisition, the motion
speed of the tested object shall be matched with the frame frequency of image
acquisition. Meanwhile, it is necessary to ensure that the X-ray main beam
trans-illuminates the tested object vertically (or in alignment) and reaches the
effective imaging area of the detector.
5.1.3 In the case of image acquisition by static imaging, the length of
overlapped area of image acquisition shall not be less than 10mm.
5.1.4 Small-diameter tubes shall be arranged in double-wall double-shadow
trans-illumination mode. When the following conditions are met at the same
time, the oblique trans-illumination mode shall be used for elliptical imaging:
a) T (wall thickness) ≤ 8mm;
b) g (weld width) ≤ Do / 4.
Where: Do - Outer diameter of the tube.
The opening width (the maximum distance between the upper and lower weld
projections) of the images shall be controlled at about 1 times the weld width.
In the case of failing to meet the above conditions or elliptical imaging difficulties,
vertical trans-illumination mode may be used for overlapping imaging.
5.2 Selection of imaging geometric parameters
5.2.1 The distance from the selected X-ray machine to the surface of the
tested object, f, shall meet the following requirements:
a) Level AB X-ray digital radiographic testing technology: f ≥ 10d•b2/3;
b) Level B X-ray digital radiographic testing technology: f ≥ 15d•b2/3.
The diagram of imaging geometric trans-illumination is described in Figure 1.
The effective focus size, d, shall be calculated in accordance with the relevant
requirements of NB/T 47013.2. b represents the distance from the surface of
the tested object to the detector.
Explanation:
1 - Detector;
2 - Tested object.
Figure 1 -- Diagram of imaging geometric trans-illumination
5.2.2 In the event that the X-ray machine adopts inner central trans-
illumination mode, when the image quality meets the requirements of 6.1.4.1
and 6.1.4.2, the value of f may be reduced, but the reduction shall not exceed
50% of the specified value.
5.2.3 In the event that the X-ray machine adopts inner single-wall trans-
illumination mode, when the image quality meets the requirements of 6.1.4.1
and 6.1.4.2, the value of f may be reduced, but the reduction shall not exceed
20% of the specified value.
5.2.4 Estimation of the geometric parameters of trans-illumination
In theory, the optimal magnification of the given testing system may be
calculated according to the Formula (1).
Where:
M0 - Optimal magnification;
d - Focus size;
Uc - Inherent unsharpness of the detector (approximately equal to twice the
detector pixel size).
The relationship between the image resolution ratio and the geometric
parameters of trans-illumination is given in Formula (2). For the given testing
system and the tested object, the geometric parameters of trans-illumination
suitable for the system may be selected based on Formula (2), in combination
with the actual testing conditions.
Where:
M - Magnification [REFER to Formula (3) for calculation];
Ug - Geometric unsharpness;
Ur - Image resolution that shall be achieved (approximately equal to twice the
duplex wire diameter that shall be resolved).
Where:
F - Distance from the X-ray machine to the detector;
f - Distance from the X-ray machine to the surface of the tested object.
5.3 Trans-illumination direction
During trans-illumination, the center of the X-ray beam shall point
perpendicularly to the center of the trans-illumination zone. The directions
conducive to discovering the defects may be selected for trans-illumination, if
necessary.
5.4 Determination of the number of trans-illuminations of non-planar
objects
5.4.1 Number of trans-illuminations for 100% static imaging of the girth-
welded joints on the small-diameter tube.
5.4.1.1 In the case of elliptical imaging for oblique trans-illumination:
a) In the case of T / Do ≤ 0.12, PERFORM trans-illumination twice separated
by 90°;
b) In the case of T / Do > 0.12, PERFORM trans-illumination three times
separated by 120° or 60°.
5.4.1.2 In the case of overlapping imaging for vertical trans-illumination, trans-
illumination shall be normally performed three times separated by 120° or 60°.
5.4.2 In the event that multiple trans-illumination cannot be carried out due to
structural reasons, elliptical imaging or overlapping imaging may be used for
trans-illumination once. In view of the failure to achieve 100% full-length weld
inspection after trans-illumination once, effective measures shall be taken at
this time to expand the detectable range of defects. Meanwhile, it is necessary
to ensure that the gray level, signal noise ratio, sensitivity and resolution meet
the requirements within the range of image evaluation.
5.4.3 For the tested object whose outer surface diameter is greater than
100mm and less than the effective imaging size of the detector, under the
premise of meeting the requirements of trans-illumination thickness ratio, value
of K, in Table 2, the effective length of a trans-illumination shall not be greater
than the inner diameter of the tested object, and the gray level of the images
shall meet the requirements of 6.2.3.
Table 2 -- Allowable trans-illumination thickness ratios at different
testing technology levels
Testing technology level Trans-illumination thickness ratio, K
Level AB 1.2
Level B 1.1
5.5 Selection of trans-illumination parameters
During actual testing, appropriate X-ray energy, exposure and other parameters
shall be selected according to the characteristics of the X-ray digital
radiography system in use and the tested object, so as to meet the testing
requirements.
5.5.1 X-ray energy
Tube voltage shall be as low as possible. During the use of higher tube voltage,
it is necessary to ensure appropriate exposure. The highest tube voltage
allowed for different materials and different trans-illumination thicknesses is
specified in Table 2, respectively. For the object with non-uniform thickness,
under the premise of ensuring the image quality in line with the requirements of
this Part, the tube voltage may be appropriately higher than the limit value in
Figure 2.
Explanation:
1 - Copper and its alloys, nickel and its alloys;
2 - Steel;
3 - Titanium and its alloys;
4 - Aluminum and its alloys.
Figure 2 – The allowable highest X-ray trans-illumination tube voltage for
different trans-illumination thicknesses
5.5.2 Exposure
5.5.2.1 The exposure is equal to the product of the effective exposure time
and the tube current, expressed in mA • s.
All
ow
ab
le
hig
he
st
tub
e v
olt
ag
e /
kV
Thickness / mm
5.5.2.2 It is allowed to increase the signal noise ratio and improve the image
quality by increasing the exposure.
5.5.2.3 Under the premise of meeting the requirements for image quality,
testing speed and efficiency, a lower exposure may be selected.
5.5.2.4 During actual testing, appropriate exposure shall be selected by
coordinating the parameters affecting the exposure, according to the
requirements for testing speed, testing equipment and testing quality.
a) The planar array detector may control the exposure by reasonably selecting
the frame frequency for acquisition, number of superimposed images and
tube current;
b) The linear array detector may control the exposure by reasonably selecting
the exposure time and tube current.
5.6 Marks
5.6.1 The marks of the trans-illumination parts are composed of identification
and positioning marks.
5.6.2 The identification marks generally include the product number, welded
joint number, part number and trans-illumination date. After repair, trans-
illumination shall also have a repair mark. The trans-illumination with expanded
testing ratio shall also have an expanded testing mark. The identification marks
may be written in by a computer.
5.6.3 The positioning marks generally include the center mark “ ” and the
overlapping mark “↑”. The center mark indicates the central position in the
section of trans-illumination parts and the direction of the section number. The
overlapping mark is the mark of trans-illumination section, which is generally
composed of proper size figures, phonetic alphabets and symbols made of lead
or other appropriate heavy metals. When the lead overlapping mark is
expressed in figures or letters, the center mark may be omitted.
5.6.4 For dynamic imaging testing, a positioning mark “ ” shall be made at
the starting position of testing, among which “→” points to the testing direction.
The segment mark can be expressed in figures or alphabets. During the testing
of girth welds, a marker may be used for marking in a clockwise direction. The
fillet welds may be marked from left to right, and the mark shall be matched with
the image tag.
5.6.5 The marks shall normally be placed at least 5mm away from the weld
edges, and shall meet the relevant marking requirements of NB/T 47013.2. All
marked images shall not overlap. There shall be no image interfering with the
effective evaluation range.
5.7 Shielding of useless X-rays and scattered rays
Appropriate measures, such as filter board, collimator (aperture), lead foil, lead
plate, etc., shall be taken to reduce scattered rays and useless X-rays.
6 Image quality and evaluation
6.1 Image quality
6.1.1 General requirements
6.1.1.1 It is necessary to ensure the requirements for image sensitivity and
image resolution.
6.1.1.2 The image quality indicators for determining the image quality are
divided into the image quality indicators (wire type) and the image quality
indicators (duplex wire type).
6.1.1.3 The image sensitivity shall be determined by using an image quality
indicator (wire type). The model and specifications of the image quality indicator
(wire type) shall meet the requirements of GB/T 23901.1.
6.1.1.4 The image resolution ratio shall be determined by using an image
quality indicator (duplex wire type). The model and specifications of the image
quality indicator (duplex wire type) shall meet the requirements of GB/T 23901.5.
6.1.1.5 Image quality verification shall be carried out at the time of first trans-
illumination of each welded joint. Or CARRY out special process verification
prior to the first trans-illumination of each welded joint. The image quality
indicators (wire type) and the image quality indicators (duplex wire type) shall
be placed during trans-illumination layout, so as to verify the image quality.
6.1.2 Image quality indicator (wire type)
6.1.2.1 Placement principle of the image quality indicator (wire type)
6.1.2.1.1 During single-wall single-shadow or double-wall double-shadow
trans-illumination, the image quality indicator (wire type) shall be placed on the
side of the X-ray machine.
6.1.2.1.2 During double-wall single-shadow trans-illumination, the image
quality indicator (wire type) shall be placed on the side of the detector.
6.1.2.1.3 When the image quality indicator (wire type) is placed on the side of
the detector, a lead letter “F” shall be placed in an appropriate position as the
mark. “F”-marked image shall appear on the image simultaneously with the
mark of the image quality indicator, and shall be indicated in the testing report.
6.1.2.2 Use of the image quality indicator (wire type)
6.1.2.2.1 Metal wire materials of the image quality indicator (wire type) shall
be the same as or similar to the tested object. Under the premise of meeting
the requirements for image sensitivity, a low-density image quality indicator
(wire type) may be used for testing high-density materials.
6.1.2.2.2 The materials, material codes of the image quality indicator (wire
type) and the applicable range of the image quality indicators made of different
materials shall meet the requirements of Table 3.
Table 3 -- Applicable range of the image quality indicators made of
different materials
Material codes of the
image quality indicator
(wire type)
Fe
(steel)
Ni
(nickel)
Ti
(titanium)
Al
(aluminum)
Cu
(copper)
Materials of the image
quality indicator
(wire type)
Carbon
steel
Nickel-
chromium
alloy
Commercial
pure
titanium
Commercial
pure
aluminum
3# pure
copper
Applicable material range Steel Nickel and its alloys
Titanium
and its
alloys
Aluminum
and its
alloys
Copper and
its alloys
6.1.2.2.3 The image quality indicator (wire type) shall be normally placed at
one end of the welded joint, in the position of about 1/4 of the length of the
tested area. The metal wires shall cross the welds. The filaments shall be
placed on the outside. When multiple welded joints of the same specifications
and the same type are trans-illuminated simultaneously on an image, the image
quality indicator (wire type) shall be placed at the weld on the utmost edge of
the trans-illumination zone.
6.1.2.2.4 In principle, each image shall have the image of the image quality
indicator (wire type). In the case where the trans-illumination parameters and
the tested object are not changed (such as dynamic imaging of a weld), the
image quality indicator (wire type) may be placed in the first image only.
6.1.2.2.5 Either general image quality indicator (wire type) or special image
quality indicator (wire type) is optional for small-diameter tubes. Metal wires
shall cross the welds.
6.1.2.3 Identification of the image quality indicator (wire type)
When dynamic imaging of the image quality indicator’s wire with a length of not
less than 10mm is clearly visible in the image with uniform gray level (typically
the parent metal zone adjacent to the welds), this wire is considered to be
recognizable. A special image quality indicator (wire type) shall be able to
recognize at least two metal wires.
6.1.3 Image quality indicator (duplex wire type)
6.1.3.1 The image quality indicator (duplex wire type) shall be placed on the
side of the detector.
6.1.3.2 Use of the image quality indicator (duplex wire type)
6.1.3.2.1 The image quality indicator (duplex wire type) shall be placed on the
parent metal at about 1/4 of the length of the tested area. Metal wires shall be
placed at a small angle (such as 2° to 5°) with the row or column of the image
(or detector). The filaments shall be placed on the outside.
6.1.3.2.2 In principle, each image shall have the image of the image quality
indicator (duplex wire type). In the case where the trans-illumination parameters
and the tested object are not changed (such as dynamic imaging of a weld), the
image quality indicator (duplex wire type) may be placed in the first image only.
The filaments shall be placed on the outside.
6.1.3.2.3 If the image quality indicator (duplex wire type) cannot be placed in
the specified position, the contrast specimen with the minimum thickness
shown in Table 4 and Table 5 shall be used to replace the tested object.
However, its image resolution ratio shall not be lower than the values in the
tables.
Table 4 -- Image resolution ratio required for Level AB image quality
Range of the nominal thickness (T) or trans-illumination thickness (W) / mm Image resolution ratio / (lp/mm) Wire No. Wire diameter / mm
Note: For double-wall single-shadow trans-illumination mode, nominal thickness, T, shall be taken.
Table 5 -- Image resolution ratio required for Level B image quality
6.1.3.3 Identification of the image quality indicator (duplex wire type)
The identification method of the image quality indicator (duplex wire type) is
described in Annex C.
6.1.4 Requirements for image quality
6.1.4.1 Image sensitivity
According to the requirements for testing technology levels and the adopted
trans-illumination mode, the image sensitivity shall meet the requirements of
Table 6 to Table 8, respectively. The requirements for image sensitivity of tube-
tube plate seal fillet welds shall be implemented according to the relevant
contents of NB/T 47013.2. Under the premise of using appropriate process
parameters and taking effective compensation measures, the image sensitivity
of the strength fillet welds may be implemented by reference to the
requirements for seal welding.
6.1.4.2 Image resolution ratio
According to the requirements for testing technology levels, the image
resolution ratio shall meet the requirements of Table 4 and Table 5, respectively.
6.1.4.3 Compensation principle
If the image resolution ratio does not meet the requirements of Table 4 or Table
5, the image sensitivity may be improved by increasing the signal noise ratio,
so as to compensate the contrast sensitivity reduction due to substandard
sharpness. The signal noise ratio shall be higher than the requirements of 6.2.4.
For instance, for a testing system, an object with a testing thickness of 10mm
is required to achieve the Level B image quality, if the image quality cannot
reach W14 and D11 at the same time, the equivalent testing sensitivity may be
Range of the nominal thickness (T) or trans-illumination thickness (W) / mm
Note: For double-wall single-shadow trans-illumination mode, nominal thickness, T, shall be taken.
Image resolution ratio / (lp/mm) Wire No. Wire diameter / mm
provided after reaching W15 and D10. The compensation shall be up to no
more than 2 wire numbers.
6.1.4.4 For a given testing system, if geometric conditions and tube voltage
are given, the signal noise ratio may be increased by increasing the exposure.
Table 6 -- Image sensitivity value - Single-wall trans-illumination, image
quality indicator is placed on the side of the X-ray machine
Nominal thickness T/mm Wire No. that shall be recognized
(wire diameter / mm) Level AB Level B
Note: When outer diameter of the tube or branch tube is less than or equal to 120mm, the image sensitivity of the tube seat fillet welds may be reduced by one level.
Table 7 -- Image sensitivity value - Double-wall double-shadow trans-
illumination, image quality indicator is placed on the side of the X-ray
machine
Table 8 -- Image sensitivity value - Double-wall single-shadow or double-
wall double-shadow trans-illumination, image quality indicator is placed
on the side of the detector
Wire No. that shall be recognized
(wire diameter / mm)
Trans-illumination thickness W/mm
Level AB Level B
Trans-illumination thickness W/mm Wire No. that shall be recognized
(wire diameter / mm) Level AB Level B
Table 8 (Continued)
6.2 Image evaluation
6.2.1 General requirements
6.2.1.1 The quality grade of the tested object may be evaluated only after the
image quality meets the specified requirements.
6.2.1.2 It can be displayed by positive or negative images.
6.2.1.3 The images shall be observed in a soft light environment. The display
screen shall be clean, with no obvious light reflection.
6.2.1.4 There shall be no artifact interfering with the recognition of defect
images in the effective evaluation area of images.
6.2.2 System software requirements
The system software shall meet the requirements of 4.2.4.
6.2.3 Requirements for the gray level range of images
6.2.3.1 The gray level in the effective evaluation area of images shall be
controlled according to the corresponding technology level. The specific
requirements are as follows:
a) The gray level of Level AB images shall be controlled between 20% and 80%
of the full range;
b) The gray level of Level B images shall be controlled between 40% and 80%
of the full range.
6.2.3.2 The gray level distribution range may be determined by measuring the
image gray level histogram.
6.2.4 Requirements for signal noise ratio
Trans-illumination thickness W/mm Wire No. that shall be recognized
(wire diameter / mm) Level AB Level B
6.2.4.1 The minimum requirements for normalized SNR in Table 9 and Table
10 shall be met.
6.2.4.2 The normalized SNR test method is described in Annex D.
Table 9 -- Minimum requirements of normalized SNR (steel, copper,
nickel, titanium and their alloys)
Table 10 -- Minimum requirements of normalized SNR (copper and its
alloys)
6.2.5 Image storage
6.2.5.1 The storage format shall be executed according to DICONDE format.
6.2.5.2 Information such as organization code, object number, weld number,
trans-illumination specifications, testing personnel code, identification mark, etc.
shall be written in the description field of the image file, which shall be
unchangeable.
6.2.5.3 The weld number shall correspond to the image number.
6.2.6 Defect recognition and evaluation
6.2.6.1 The defects may be recognized by artificial recognition or computer-
aided recognition.
Level AB
Level AB Level B
Level B
Normalized SNR
Normalized SNR
Tube voltage range / kV
Tube voltage range / kV
Trans-illumination
thickness / mm
6.2.6.2 The defects may be evaluated by artificial evaluation or computer-
aided evaluation.
6.2.6.3 Artificial recognition may change the gray level range of image display
through linear stretching of images using system software tools.
6.2.7 Geometric dimension measurement of defects
The geometric dimensions of the defects shall be measured by using system
software. The measurement formula may refer to Formula (4):
S = δ × NS …………………………………(4)
Where:
S - Geometric dimensions;
δ - Geometric dimension factor;
NS - Number of pixels obtained by measuring the dimensions of the defect
image using a computer.
Before defect measurement, it is allowed to combine with the actual testing
requirements. Under actual testing conditions, the X-ray digital images of the
specimen with known dimensions shall be acquired to calibrate its geometric
dimensions. The geometric dimension factor shall be calculated by reference
to Formula (5):
δ = L / Ni ………………………………….(5)
Where:
δ - Geometric dimension factor (mm/pixel);
L - Specimen dimensions (mm) for calibration;
Ni - Number of pixels obtained by measuring the specimen image dimensions
for calibration using a computer.
6.2.8 Defect depth measurement
Simulated specimens may be used for defect depth measurement, so as to
obtain the change rules of different depths (thicknesses) and image gray levels,
calculated by the system software.
7 Testing result assessment and quality grading
(acceptance)
7.1 The testing result assessment and quality grading of X-ray digital
radiography for the welded joint seams of pressure equipment shall be carried
out in accordance with the requirements of NB/T 47013.2.
7.2 The defect assessment and quality acceptance of tube-tube plate fillet
welds shall be carried out according to NB/T 47013.2.
8 Image preservation and storage
8.1 Image preservation
8.1.1 Images shall be stored in the digital storage media such as hard disks,
and be archived on the CD-ROMs.
8.1.2 The testing images shall be backed up not less than two copies.
Corresponding original records and testing reports shall also be preserved over
the same period.
8.1.3 Images shall be kept for not less than 8 years. The image data must not
be lost or altered during the valid retention period.
8.2 Storage environment
The digital storage media for testing image storage, such as optical disks or
hard disks, etc., shall be anti-magnetic, moisture-proof, dustproof and be
protected against backlogs and scratches.
9 Testing records and reports
9.1 The relevant information and data of the testing process shall be recorded
in detail according to the actual situation of site operation. The X-ray digital
radiographic testing records shall not only meet the requirements of NB/T
47013.1, but also include the following contents:
a) manufacturing organization, testing organization or commissioning
organization;
b) tested objects: bevel type, welding method;
c) number(s) of the testing process document(s) in use;
d) testing equipment: effective focus size of the X-ray machine;
e) testing codes: testing technology level, trans-illumination layout, image
quality indicator, filter board, ray energy, exposure or trans-illumination time,
relative relationship between the X-ray machine and the detector, geometric
parameters of trans-illumination, software processing modes and
conditions, etc.;
f) image evaluation: gray level, signal noise ratio, image sensitivity, image
resolution ratio, defect position and nature;
g) verification of testing process documents;
h) testing results and quality grading;
i) auditors and their technical qualifications; and
j) other events that need to be explained or recorded.
9.2 The testing report shall be issued according to the testing records. The
report format is given in Annex E. The X-ray digital radiographic testing report
shall not only meet the requirements of NB/T 47013.1, but also include the
following contents:
a) manufacturing organization, testing organization or commissioning
organization;
b) tested objects: bevel type, welding method;
c) number(s) of the testing process document(s) in use;
d) testing equipment: effective focus size of the X-ray machine;
e) testing codes: testing technology level, trans-illumination layout, filter board
(type, quantity and thickness), image quality indicator, ray energy, exposure
or trans-illumination time, relative relationship between the X-ray machine
and the detector, geometric parameters of trans-illumination, software
processing modes and conditions, etc.;
f) image evaluation: gray level, signal noise ratio, image sensitivity, image
resolution ratio, defect position and nature.
Annex A
(Normative)
Verification method of the system resolution ratio
A.1 A resolution indicator (parallel arrangement or fan-shaped arrangement
type) or an image quality indicator (duplex wire type) shall be used for verifying
the system resolution ratio. During the selection of resolution indicator, the
maximum number of wire pairs for the indicator shall be greater than the
performance index specified by the system.
A.2 The patterns of the resolution indicator are described in GB/T 23903.
A.3 The patterns of the image quality indicator (duplex wire type) are
described in GB/T 23901.5.
A.4 Either resolution indicator or image quality indicator (duplex wire type)
shall have a test or appraisal certificate.
A.5 Verification methods
A.5.1 A resolution indicator or an image quality indicator (duplex wire type)
shall be close to the central zone on the surface of the detector’s input screen.
Metal wires shall be placed at an angle of 2° to 5° with the row or column of the
detector. Trans-illumination shall be performed according to the following
process conditions. Images shall be presented on a computer.
a) The X-ray tube focus shall be at a distance of 1 000 ± 50mm from the
surface of the detector’s input screen.
b) Exposure parameters of different materials:
1) For light alloy materials: The tube voltage is 90kV; the aluminum filter
board is 1mm thick;
2) For materials made of steel, copper and its alloys, nickel and its alloys:
In the case of thickness less than or equal to 20mm, the tube voltage is
160kV; the copper filter board is 1mm thick;
3) For materials made of steel, copper and its alloys, nickel and its alloys:
In the case of thickness greater than 20mm, the tube voltage is 220kV;
the copper filter board is 2mm thick.
c) The gray level shall not be less than 50% of the maximum gray level.
d) Signal noise ratio: In the case of pixel value greater than or equal to 80μm,
SNRn ≥ 140; in the case of pixel value less than 80μm, SNRn ≥ 100.
A.5.2 For the recognition method of the system resolution ratio, REFER to
Annex C.
Annex B
(Informative)
Typical trans-illumination modes
B.1 Typical trans-illumination modes of butt welds
The diagrams for typical trans-illumination modes of common butt welds are
given in Figure B.1 to Figure B.6, which may be used for reference during trans-
illumination layout. In the figures, d represents the effective focus size of the X-
ray machine; F represents the distance from the X-ray machine to the detector;
b represents the distance from the tested object to the detector; f represents
the distance from the X-ray machine to the tested object; T represents the
nominal thickness; Do represents the outer diameter of the tube; 1 represents
the detector; 2 represents the tested object.
Figure B.1 -- Outer double-wall single-shadow trans-illumination mode
(1) of the X-ray machine for girth welds
Figure B.2 -- Outer double-wall single-shadow trans-illumination mode
(2) of the X-ray machine for girth welds
Figure B.3 -- Oblique trans-illumination mode (elliptical imaging) of the
girth welds on the small-diameter tube
Figure B.4 -- Vertical trans-illumination mode of the girth welds on the
small-diameter tube
Figure B.5 -- Outer single-wall trans-illumination mode of the X-ray
machine for longitudinal and girth welds
Figure B.6 -- Inner single-wall trans-illumination mode of the X-ray
machine for longitudinal and girth welds
B.2 Typical trans-illumination modes of tube seat fillet welds
The diagrams for typical trans-illumination modes of common tube seat fillet
welds are given in Figure B.7 to Figure B.9, among which d represents the
effective focus size of the X-ray machine; T represents the nominal thickness;
b represents the distance from the tested object to the detector; 1 represents
the detector; 2 represents the tested object, which may be used for reference
during trans-illumination layout.
Figure B.7 -- Inner single-wall central trans-illumination mode of the X-
ray machine for the fillet welds on the insertion nozzle
Figure B.8 -- Outer single-wall trans-illumination mode of the X-ray
machine for the fillet welds on the insertion nozzle
Figure B.9 -- Outer single-wall trans-illumination mode of the X-ray
machine for the fillet welds on the abutting nozzle
Source
Annex C
(Normative)
Recognition of the image quality indicator (duplex wire type)
C.1 Layout of the image quality indicator (duplex wire type)
The image quality indicator (duplex wire type) shall be placed at a small angle
(such as 2° to 5°) with the row or column of the image (or detector).
C.2 Method for measuring the recognition rate of the image quality
indicator (duplex wire type)
C.2.1 The image quality indicator (duplex wire type) shall be recognized and
measured in an area with uniform gray level on the image. Not less than 21
rows of pixels shall be used for superimposed averaging.
C.2.2 As shown in Figure C.1, CALCULATE the recognition rate, R, of the
wire at the image where the thinnest wire pair is able to be recognized clearly.
R = (∆GV / BGV) × 100% …………………….(C.1)
Where:
∆GV - Recognizable gray level difference of the thinnest wire pair;
BGV - Background gray level.
C.2.3 In case of meeting the requirement of R > 20% in this Part, that is,
meeting the requirement of edge separation greater than 20%, this wire pair
may be recognizable.
C.2.4 The first set of wire pair of not greater than 20% in the image of the
image quality indicator (duplex wire type) refers to the minimum resolution ratio
required in Table 4 and Table 5.
Figure C.1 -- Diagram for recognition rate of the image quality indicator
(duplex wire type)
Distance between two wires
Sig
na
l va
lue
Annex D
(Normative)
Normalized SNR test method
D.1 Normalized SNR calculation
Normalized SNR, SNRn, shall be calculated according to the Formula (D.1):
Where:
P - Pixel size (μm) of the detector;
SNRm - Measured SNR.
D.2 Measured SNR
TAKE a rectangular region of interest (ROI) of not less than 50 pixels by 50
pixels in area in the heat-affected zone or in the parent metal zone near the
heat-affected zone. CALCULATE the mean value and standard deviation of this
region. The measured SNR, SNRm, is then obtained in accordance with the
definition of SNR.
Annex E
(Informative)
Format of the testing report
X-ray digital radiographic testing report
Report No.:
Product name Product category
Serial No. Specifications
Executive standard Material
Testing ratio Testing time
Quality grading Acceptance level
Welding method Weld length
Weld No.
Imaging
conditions
X-ray machine model: Detector type:
Focus size: mm Pixel size: mm
Focal length: mm Detector specifications:
Tube voltage: kV Filter board:
Tube current: mA Model of image quality indicator (wire type):
Exposure time: s Model of image quality indicator (duplex wire type):
Trans-illumination mode: Image quality index: W / D
Magnification: Gray level:
Image storage format: Signal noise ratio:
Software
processing
methods and
conditions
Number of images Total: pcs Where: / pcs for 1st repair; / pcs for 2nd repair; / pcs for 3rd repair
Evaluation results pcs at Level I; pcs at Level II; / pcs at Level III; / pcs at Level IV
Trans-illumination
date Defect type Defect size / mm Evaluation result Mark No.
Remark Testing diagram
Tested by: dd mm yy Evaluated by: dd mm yy (special seal for inspection)
____________________
Modification Notification of Industry Standard
(2018XG1)
This modification notification was approved by the National Energy Administration
through No.7 announcement on May 14, 2018. The date of implementation is July 1,
2018.
1. Supplement of new clause after Chapter 2 “GB/T 23903 Resolution indicators
for ray image”
“GB/T 26592 Non-destructive Testing Instruments - Properties Test Methods of
Industrial X-ray Apparatus
GB/T 26594 Non-destructive Testing Instruments - Properties Test Methods of
Industrial X-ray Tube”
Supplement of new clause after Chapter 2 “NB/T 47013.2 Nondestructive testing
of pressure equipment - Part 2: Radiographic testing”
“JB/T 11608 Non-destructive Testing Instruments - Industrial X-ray Apparatus for
Radiographic Testing”
2. Modification of choices of words in 4.1.1
“obtain the Radiologic Worker Certificate” is modified into “obtain corresponding
certificates in accordance with the requirements of relevant laws and regulations”.
3. Modification of choices of words in 4.2
“detector system” is modified into “detector system and apparatus”.
4. Supplement of new clause 4.2.1.3 after 4.2.1.2
“The performance indexes of the adopted X-ray machine shall comply with the
stipulations in JB/T 11608; test conditions and test methods for the functional
performance shall refer to the stipulations in GB/T 26594 and GB/T 26592.”
5. Modification of new clause 4.2.2.4
4.2.2.4 “Bad pixel requirements: in planar array detector 3  3 pixel region, the number
of adjacent bad pixels shall not exceed 3; the number of bad pixels in lines (or in
columns) shall not exceed 3, and shall not be within 200 pixels away from the central
position; in imaging area, bad pixels shall not exceed 1% of the total pixels. In linear
array detector, the number of adjacent bad pixels is not allowed to exceed 2. The
detector system supplier shall provide correction methods for the exit-factory bad pixel
tables and bad pixels.”
6. Supplement of new clauses 4.2.2.6 and 4.2.2.7 after 4.2.2.5
“4.2.2.6 The test conditions and test methods for detector system performance indexes,
such as: bad pixel, contrast sensitivity, resolution ratio, signal-to-noise ratio, linear
range, thickness tolerance and afterimage, shall comply with the stipulations in
corresponding national or industrial standards.”
“4.2.2.7 In the quality certificate of the detector system, at least the following technical
parameters shall be provided: detector type, conversion screen parameters (if there
are any), pixel size, imaging area, scope of application of ray energy, quantum
conversion efficiency, fill factor and acquisiti......
Related standard:   NB/T 47013.14-2016  NB/T 47013.10-2015
   
 
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