NB/T 47013.11-2023Nondestructive testing of pressure equipments - Part 11: X-ray digital radiographic testing (English PDF)

3.1 Pixel

The basic unit of digital radiographic images. Digital radiographic images are composed of points, which are called pixels.

3.2 Digital detector array (DDA)

An electronic device that converts radiographic photons into digital signals, referred to as a detector.

3.3 Image sensitivity

The ability of a detection system to detect the smallest details in the image of the inspected workpiece.

3.4 Digital radiographic system

A system composed of a detector and its processing unit, that can convert radiographic photons into digital images, referred to as a DR system.

3.5 Resolution ratio

The ability to distinguish the minimum distance between two adjacent details per unit length, in units of line pairs per millimeter (lp/mm).

3.6 Resolution

The ability to distinguish the minimum distance between two adjacent details, in units of millimeters (mm).

Resolution ratio and resolution are numerically the reciprocal of 2 times each other.

4.1 Testers

4.2 Testing system and equipment

4.2.2 "-ray machine

4.2.2.1 The type and activity of the "-ray source shall be selected according to the thickness, material, focal length of the workpiece to be inspected.

4.2.2.2 The selection of source size shall match the detector and penetration arrangement used.

4.2.2.3 The performance indicators of the "-ray machine used shall comply with the provisions of GB/T 14058.

4.2.8 Use performance of testing system

The appropriate testing equipment and instruments shall be selected, according to the performance indicators of each part of the testing system, in combination with the inspected workpiece and the requirements of this document; test certification documents that meet the performance indicators of the above equipment and instrument and the system software functions shall be provided. The use performance of the testing system shall meet the image quality requirements specified in this document.

4.2.1 X-ray machine

4.2.3 Detector

4.2.3.1 The detector matching the size of the radiation source focal point (or source) shall be selected, according to the specifications of the workpiece to be inspected, the detection technology class, the acceptance criteria.

4.2.3.2 It includes area array detectors, line array detectors and their accessories.

4.2.3.3 The dynamic range shall be no less than 2000.1.

4.2.3.4 The number of A/D conversion bits shall be no less than 12 bit.

4.2.3.5 Bad pixel requirements

4.2.5 System software requirements

4.2.5.1 The system software is the core unit of the digital imaging detection system for radiographic detection, which has the functions such as image acquisition, image processing, defect geometry measurement, defect marking, image storage, auxiliary evaluation.

4.2.6 Test fixture

4.2.6.1 It shall be designed according to the workpiece to be inspected and meet the inspection requirements.

4.2.6.2 It should have functions such as translation, rotation, continuously adjustable speed; ensure high operating accuracy and stability.

4.2.6.3 The stepping motion of the test fixture shall match the data acquisition of the detector.

4.2.6.4 For the testing of in-service equipment, the testing instruments and equipment shall be reasonably fixed, according to the on-site environment and testing conditions.

4.2.7 Image quality meter

4.2.9 Calibration or operation verification

4.3 Testing technology class

4.3.1 The digital radiographic detection technology class specified in this document is divided into three levels from low to high. Level A, Level AB, Level B.

4.4 Testing process documents

4.4.3 The operation instructions shall be prepared, according to the content of the process specification and the testing requirements of the workpiece to be inspected. In addition to meeting the requirements of NB/T 47013.1, the contents shall at least include.

4.4.4 Process verification

4.4.4.1 The operating instructions shall be fully verified before the first application.

4.5 Safety requirements

4.5.1 The testing environment shall meet the requirements of the environment (temperature, humidity, grounding, electromagnetic radiation, vibration, etc.) for the operation of the testing system.

4.5.2 Radiation protection conditions shall comply with the relevant provisions of GB 18871 and GBZ 117.

4.5.3 When conducting digital radiographic testing on site, the control area and supervision area shall be demarcated in accordance with the provisions of GBZ 117; warning signs shall be set up; the testing personnel shall wear personal dosimeters and carry dose alarms.

5.1 Timing of testing

5.1.1 The timing of testing shall meet the requirements of relevant laws, regulations, standards, design technical documents, and other technical requirements agreed upon by both parties to the contract.

5.1.2 Unless otherwise specified, the testing shall be carried out after welding is completed. For materials with delayed cracking tendency, the testing shall be carried out at least 24 hours after welding is completed.

5.2 Testing area

The width of the testing area shall meet the requirements of relevant laws, regulations, standards and design technical documents, and other technical requirements agreed upon by both parties to the contract.

5.3 Penetration method

5.8 Marking

5.8.1 The marking of the penetration part consists of identification and positioning marks.

5.8.2 The identification mark generally includes the product number, welding joint number, part number, penetration date. The penetration after repair shall also have a repair mark. The penetration with an expanded detection ratio shall have an expanded detection mark. The identification mark can be written by a computer.

5.8.3 The positioning mark generally includes the center mark " " and the overlap mark " ". The center mark indicates the center position of the penetration part segment and the direction of the segment number. The overlap mark is a penetration segment mark, which is generally composed of appropriate size lead or other suitable heavy metal numbers, pinyin letters, symbols. When the lead overlap mark is represented by numbers or letters, the center mark can be omitted.

5.9 Standard sample

5.9.1 The standard sample is used as a dimension calibration sample when measuring features in the image. The detailed steps of dimension calibration are as shown in 7.2.1.

5.9.2 The standard sample shall be placed on the workpiece surface on the detector side, imaged within the effective evaluation range, not interfere with the image within the effective evaluation range.

5.9.3 The length of the standard sample shall not be less than 15 mm.

5.10 Shielding of useless rays and scattered rays

Appropriate measures such as filter plates, collimators (aperture), lead foils, lead plates, etc. shall be adopted, to reduce scattered rays and useless rays.

6.1 Image quality

6.1.1 General requirements

6.1.1.1 The requirements of grayscale, image sensitivity, image resolution, normalized signal-to-noise ratio shall be guaranteed at the same time.

6.1.1.2 Image quality meters for measuring image quality are divided into linear image quality meters and dual-linear image quality meters.

6.1.1.3 Image sensitivity is measured by linear image quality meters.

6.1.1.4 Image resolution ratio is measured by dual-linear image quality meters.

6.1.2 Linear image quality meters

6.2 Image evaluation

6.2.1 General requirements

6.2.1.1 Image quality evaluation shall be carried out in the original image; image processing methods that change the gray value (such as filtering technology) shall not be used.

6.2.1.2 It can be displayed in the form of positive image (film) or negative image (film).

6.2.2 System software requirements

The system software shall meet the requirements of 4.2.5.

6.2.3 Image grayscale range requirements

The grayscale range in the effective evaluation area of the image shall be controlled within 10% ~ 80% of the full scale (positive film).

6.2.4 Signal-to-noise ratio requirements

6.2.5 Image sensitivity requirements

6.2.6 Image resolution requirements

6.2.6.1 According to the requirements of the detection technology class, the image resolution shall comply with the provisions of Table 10 ~ Table 12.

6.2.6.2 For single-wall single-shadow or double-wall single-shadow penetration, the penetrated thickness shall be the nominal thickness; for double-wall double-shadow penetration of small-diameter tubes, the penetrated thickness shall be the tube diameter.

6.2.7 Compensation principle

If the image resolution does not meet the requirements of Table 10 to Table 12, the image sensitivity can be improved by increasing the signal-to-noise ratio to compensate for the lack of image resolution.

7.1 Defect identification

7.1.1 Defect identification can be achieved by manual identification or computer-assisted identification methods.

7.2 Defect measurement

7.2.1 Defect geometry measurement

The geometry of the defect to be detected shall be measured by the system software.

The measurement results can be calculated by referring to formula (2).

7.2.2 Defect depth measurement

The defect depth can be measured by simulating the test piece, to obtain the change law of different depths (thicknesses) and image grayscale, which can be calculated by the system software.

9.1 Image storage

9.1.1 The storage format shall be implemented in DICONDE format.

9.1.2 Information such as unit code, workpiece number, weld number, penetration parameters, testing personnel code, identification mark, etc. can be written into the description field of the image file; the above information shall be unchangeable.

9.2 Image preservation

9.2.1 Images shall be stored in digital storage media and archived.

9.2.2 Images shall be backed up for at least 2 copies. The corresponding original records and inspection reports shall also be kept at the same time. […]