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This Standard "Nondestructive Testing of Pressure Equipments" (NB/T 47013) comprises 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 Testing;
- 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 according to the rules given in "Directives for Standardization - Part 1: Structure and Drafting of Standards" (GB/T 1.1-2009).
This Part is proposed by and under the jurisdiction of National Technical Committee on Boilers and Pressure Vessels of Standardization Administration of China (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, State Administration for Quality Supervision and Inspection and Quarantine (Bureau of Safety Supervision of Special Equipment), North University of China, Beijing University of Aeronautics and Astronautics, Sichuan Ruidi ray digital image Technology Co., Ltd., National X-ray Digital Imaging Instrument Center, Sichuan Chuanguo Boiler Co., Ltd., Beijing Jadeshine Engineering and Chengdu Huayu Science and Technology for inspection Co., Ltd.
Chief 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 formulated for the first time.
Nondestructive Testing of Pressure Equipments - 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
1 Scope
1.1 This Part of NB/T 47013 specifies the testing technique and quality classification requirements of X-ray digital radiography of fusion welding joints of metal pressure components of pressure equipments.
1.2 This Part is applicable to the manufacturing and installation of pressure components of pressure equipments as well as the testing for X-ray digital radiography of welded joint under in-service inspection. Metal materials used for welded joint manufacturing include steel, copper and copper alloy, aluminum and aluminum alloy, titanium and titanium alloy as well as nickel and nickel alloy.
1.3 For this Part, the applicable image device is digital detector; the maximum tube voltage of applicable X-ray machine is not greater than 600kV.
1.4 Testing for X-ray digital radiography of welded joints of supporting members and structural members related to pressure equipments may also be applied by reference.
2 Normative References
The following documents for the application of this document are essential. Any dated reference, just dated edition applies to this document. For undated references, the latest edition (including any amendments) applies 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 Equipments - Part 1: General Requirements
NB/T 47013.2 Nondestructive Testing of Pressure Equipments - Part 2: Radiographic Testing
3 Terms and Definitions
For purpose of this Part, the terms and definitions specified in NB/T 47013.1 and those listed below apply.
3.1
Pixel
Basic composition unit of X-ray digital image. X-ray digital image is composed of points, and each point is referred to as pixel.
3.2
Image sensitivity
The capability of the minimum detail find by the testing system in the image of the tested workpiece.
3.3
Resolution ratio
The capacity of resolving the minimum distance between two adjacent details in unit length, which is expressed in 1p/mm.
3.4
Resolution
The resolving power of the minimum distance between two adjacent details.
3.5
System resolution ratio
The capacity of the minimum distance between two adjacent details in unit length which is resoluble by the testing system where the tested workpiece is unavailable and the geometrical magnification factor of radiography is close to 1. It reflects the characteristics of the testing system, and is also known as the basic spatial resolution ratio of the system.
3.6
Image resolution ratio
The capacity of the minimum distance between two adjacent details in unit length in the tested workpiece image which is resoluble by the testing system, also known as image spatial resolution ratio.
3.7
Digital detector
The electronic device converting X-ray photon to digital signal, hereinafter referred to as detector.
3.8
Gray level
The quantitative description for the brightness degree of black and white images obtained by X-ray digital radiography, which is determined according to the number of bits of the system A/D converter (analog-to-digital converter). The higher of the number of bits of A/D converter is, the higher of the grey level will become. For example, where the A/D converter is 12 bits, the acquired grey level is 212=4096.
3.9
Dark image
The image output without X-ray radiography, which is also known as dark current image.
3.10
Dynamic range
The ratio of the maximum grey level of the X-ray digital radiography system to the standard deviation of dark image within the linear output range.
3.11
Non-uniform responsivity
The inherent characteristic of the detector; the output image brightness takes on non-uniform streak due to the inconsistent response of detector to the X-ray under the uniform radiography of homogeneous workpieces or empty screen.
3.12
Bad pixel
The white point or black point with over-high or over-low grey level compared with adjacent pixel in dark image. It also refers to the calibrated image with output value far away from the abnormal point of image average. Existence form of bad pixel is: single point, two or more adjacent points, several lines or several columns.
3.13
Signal noise ratio
The ratio of average value to standard deviation of the signal within the interest region of the image.
3.14
Static imaging
The X-ray digital radiography where there is no relative continuous movement between the testing system and tested workpiece; the imaging result is single image.
3.15
Dynamic imaging
The X-ray digital radiography where the testing system and tested workpiece are under relative continuous movement; the imaging result is sequential images.
3.16
Limiting resolution
The maximum resolution ratio of the testing system where there is no physical (geometrical) amplification.
3.17
Digital image processing
The digital conversion method improving the contrast ratio, resolution ratio and detail recognition capability of the X-ray digital image.
3.18
Non planar object
Other objects except the planar objects described in this Part.
4 General Requirements
4.1 Testing personnel
4.1.1 The personnel engaged in testing for X-ray digital radiography shall receive radiological safety knowledge training and obtain "radiation staff card" before taking up their posts.
4.1.2 The personnel engaged in testing for X-ray digital radiography can only carry out testing on corresponding items after obtaining the special qualification of testing for X-ray digital radiography of non-destructive testing of special equipment.
4.1.3 The testing personnel shall understand the computer knowledge and digital image processing knowledge related to the X-ray digital radiography technique and master corresponding basic computer operation method.
4.2 Testing system
4.2.1 X-ray machine
4.2.1.1 The energy range of X-ray machine shall be selected according to the thickness, material and focal length of the tested workpiece.
4.2.1.2 The selection of focal point shall be matched with the adopted detector.
4.2.2 Detector system
4.2.2.1 It is composed of area array detector, linear diode array and their accessories.
4.2.2.2 The dynamic range shall not be less than 2000:1.
4.2.2.3 The number of bits for A/D conversion is not less than 12 bits.
4.2.2.4 The detector supplier shall provide the bad pixel list and bad pixel calibration method of the detector.
4.2.2.5 The detector shall be calibrated according to specific image calibration method specified for the detector system.
4.2.3 Computer system
The basic configuration of computer system is determined according to the performance and speed requirements of the adopted X-ray digital radiography component. Memory not less than 512MB, hard disk not less than 40, high-brightness high-resolution display, CD writer, network card and etc. should be equipped.
The display shall meet the following minimum requirements:
a) The brightness is not less than 250cd/m2;
b) The grey level is not less than 8 bits;
c) The image display resolution ratio is not less than 1 024×768;
d) The pixel point spacing of display is not higher than 0.3mm.
4.2.4 System software requirements
4.2.4.1 System software, as the core unit of X-ray digital radiography system, can complete image acquisition, image processing, geometric size measurement of flaw, flaw marking, image storage, auxiliary assessment, testing report printing and other auxiliary functions, and is an important factor to ensure testing accuracy and safety.
4.2.4.2 Basic digital image processing functions like superposition noise reduction, window width/position change and contrast enhancement shall be included.
4.2.4.3 Signal noise ratio measurement, flaw marking, size measurement and size calibration functions shall be included.
4.2.4.4 Amplification function not less than 4 times should be provided.
4.2.4.5 Scan and lookup functions for relevant information of acquired image shall be provided.
4.2.4.6 Testing report may be generated according to assessment result.
4.2.4.7 Original image shall be stored, and relevant processing is permissible during observation and assessment.
4.2.4.8 The processing of original image with filtering (where applied) shall be agreed by the contracting parties through negotiation, and shall be kept with relevant documents.
4.2.4.9 Other special requirements shall be determined by the contracting parties through negotiation.
4.2.5 Testing tooling
4.2.5.1 It shall be designed according to the tested workpiece and shall meet the testing requirements.
4.2.5.2 The load bearing capacity of the tested tooling shall be selected according to the weight of tested workpiece.
4.2.5.3 Translation, rotation, continuous speed adjustment functions should be provided, and high operation precision and stability are ensured.
4.2.5.4 The testing for tooling movement shall be carried out synchronously with the data acquisition of detector.
4.2.5.5 For testing of equipment in-service, the testing instrument and equipment shall be reasonably fixed according to the site environment and testing condition.
4.2.6 Acceptance and of testing system
4.2.6.1 Certification documents for the performance testing of testing system shall be provided. Performance acceptance for the testing system shall be carried out prior to the first use, and such system may only be used after passing this acceptance.
4.2.6.2 Checking shall be carried out under the following conditions; the checking mainly refers to the resolution ratio of the testing system, and the checking method is implemented according to Appendix A:
a) Where the testing system is changed;
b) Under normal service conditions, checking shall be carried out at least every 3 months;
c) Where the system is reused after shutdown for 1 month.
4.3 Technical level of testing
The technical level of X-ray testing specified in this Part is classified into: Level AB - intermediate sensitivity technique; Level B: high sensitivity technique.
4.4 Testing process documents
4.4.1 Testing process documents includes process specification and operating instructions.
4.4.2 Contents of the process specification shall not only meet the requirements of NB/T 47013.1, but also specify the specific range or requirements of the relevant factors listed in Table 1; where the variation of relevant factors exceeds the specified range or requirements, the process specification shall be prepared again.
Foreword I
1 Scope
2 Normative References
3 Terms and Definitions
4 General Requirements
5 Testing Method
6 Image Quality and Assessment
7 Testing Result Assessment and Quality Grading (Acceptance)
8 Image Preservation and Storage
9 Testing Record and Report
Appendix A (Normative) Checking Method of System Resolution Ratio
Appendix B (Informative) Typical Radiography Mode
Appendix C (Normative) Identification of Duplex Wire Type Image Quality Indicators
Appendix D (Normative) Test Method for Normalized Signal to Noise Ratio
Appendix E (Informative) Testing Report Format
