NB/T 47013.14-2023 Nondestructive testing of pressure equipments - Part 14: Computed radiographic testing
1 Scope
1.1 This document specifies the CR testing technology and quality classification requirements for fusion welded joints of pressure elements made of metallic materials in pressure equipment. The metallic materials used to produce welded 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 CR testing of butt welds of butt joints for plates and pipes (hereinafter referred to as "butt welds") in the manufacture, installation, and in-service testing of pressure elements of pressure equipment.
1.3 The imaging devices applicable to this document are imaging plates.
1.4 The ray sources applicable to this document are X-ray sources and Ir192 and Se75 γ ray sources, where the maximum tube voltage of the X-ray machine does not exceed 600 kV.
1.5 This part may also serve as a reference for CR testing of welded joints of supporting members, structural members, plug-in nozzles and mounted nozzles of the pressure equipment.
2 Normative references
The following documents contain provisions which, through reference in this text, constitute provisions of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
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
GB/T 23901.5 Non-destructive testing - Image quality of radiographs - Part 5: Determination of the image quality unsharpness and basic spatial resolution value using duplex wire-type image quality indicators
GB/T 23910 Non-destructive testing - Metal intensifying screens for radiographic testing
JB/T 7902 Non-destructive testing - Specification for wire-type image quality indicators
JB/T 11608 Non-destructive testing instruments - Industrial X-ray apparatus for radiographic testing
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 the purposes of this document, the terms and definitions given in NB/T 47013.1 and the following apply.
3.1
imaging plate, IP
flexible plate coated with rare earth elements of europium, barium and fluorine and capable of storing information in the form of latent image after exposure
3.2
computed radiographic system
system consisting of IP, special laser scanner (hereinafter referred to as "scanner"), computer hardware and special software, etc. and capable of converting the information on IP into digital images, which is referred to as "CR system"
3.3
object-to-IP distance, b
distance between the surface of the tested object (at the side of the radiation source) and the IP measured in the direction of the radiation beam
3.4
source-to-IP distance, F
distance between the radiation source and the IP measured in the direction of the radiation beam, i.e. the focal length
3.5
source-to-object distance, f
distance between the radiation source and the surface of the object (at the side of radiation source) measured along the centerline of the radiation beam
3.6
structure noise of IP
intrinsic noise of digital image caused by uneven structure of IP photosensitive layer and surface
3.7
pixel
basic component units of digital radiographic image, i.e., the dots composing a digital radiographic image
3.8
grey value
value representing the brightness degree of pixels in a digital image
3.9
linearized grey value
grey value directly proportional to the exposure of IP
3.10
image sensitivity
capability of the testing system to detect the minimum details in the image of the object
3.11
resolution ratio
capacity of distinguishing the minimum distance between two adjacent details in unit length, which is expressed in lp/mm
3.12
resolution
capacity of distinguishing the minimum distance between two adjacent details, which is expressed in mm
3.13
system resolution ratio
capacity of CR system to distinguish the minimum distance between two adjacent details
In unit length, system resolution ratio is also known as the basic spatial resolution ratio of the system, which is expressed in lp/mm
3.14
image resolution ratio
capacity of the testing system to distinguish the minimum distance between two adjacent details in unit length in the image of the object, also known as image spacial resolution ratio, which is expressed in lp/mm
3.15
scanning resolution ratio
pixel geometry size of digital image determined by scanning, which depends on the line spacing of IP scanned by laser scanner and the ratio of the laser point scanning travel speed to the working frequency of analog-to-digital converter
3.16
signal-to-noise ratio, SNR
ratio of the average linear grey value to the standard deviation of the selected area in a digital image
3.17
normalized signal-to-noise ratio, SNRn
signal-to-noise ratio after normalization based on the resolution ratio
3.18
penetrated thickness, W
nominal thickness of material in the direction of radiography in multilayer radiography, penetrated thickness is the sum of nominal thickness of penetrated layers of materials
3.19
effective length of a single exposure
maximum effective testing length of a single exposure in conformity with the standard
3.20
ratio between max. and min. penetrated thicknesses, K
ratio of the maximum thickness to the minimum thickness of parent material that radiation beam penetrates within the effective length of a single exposure
3.21
digital image processing
methods and techniques of processing digital images by computer
3.22
standard sample
sample with a known size for calibrating the feature size in images
3.23
raw image
image of the latent image formed by IP after being scanned by a scanner
3.24
round flaw
volume flaws such as porosity, slag inclusion and tungsten inclusion with length-width ratio not greater than 3
3.25
stripy flaw
volume flaws such as porosity, slag inclusion and tungsten inclusion with length-width ratio greater than 3
3.26
small diameter tube
tube with an outer diameter D0 less than or equal to 100 mm
4 General requirements
4.1 Testing personnel
4.1.1 The general requirements for CR testing personnel (hereinafter referred to as "testing personnel") shall comply with those specified in NB/T 47013.1.
4.1.2 Testing personnel shall have knowledge on computer and digital image processing related to CR testing technology, and master the corresponding basic operation methods of computers and testing software.
4.1.3 Testing personnel shall receive training on radiation safety and protection before taking their posts, and obtain the assessment certificate of corresponding radiation sources.
4.2 Testing systems and apparatus
Foreword i
Introduction iv
1 Scope
2 Normative references
3 Terms and definitions
4 General requirements
5 Testing process and its selection
6 Image quality requirements
7 Flaw identification and measurement
8 Image storage and preservation
9 Evaluation of testing results and quality grade
10 Testing records and report
Annex A (Informative) Test method of minimum grey value
Annex B (Normative) Determination of resolution ratio (resolution)
Annex C (Normative) Determination of normalized signal-to-noise ratio
Bibliography
