NB/T 47013.15-2021Nondestructive testing of pressure equipments - Part 15: Phased-array ultrasonic testing (English PDF)

Foreword

This document was issued on 26 April 2021 by the National Energy Administration of the PRC and takes effect on 26 August 2021.

It is a NB/T standard: recommended rather than compulsory, but it is the text a Chinese reviewer applies when assessing a submission.

It is classified under ICS 77.040.20, Chinese classification H 26.

NB/T 47013 Nondestructive testing of pressure equipments is divided into the following 15 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: Time of flight diffraction ultrasonic testing.

Part 11: X-ray digital imaging testing.

Part 12: Magnetic flux leakage testing.

Part 13: Pulsed eddy current testing.

Part 14: X-ray computed radiography testing.

Part 15: Phased-array ultrasonic testing.

This document is Part 15 of NB/T 47013: Phased-array ultrasonic testing.

This document was drafted in accordance with the rules given in GB/T 1.1-2020, Directives for standardization - Part 1: Rules for the structure and drafting of standardizing documents.

This document was proposed by and is under the jurisdiction of the National Technical Committee on Boilers and Pressure Vessels of Standardization Administration of China (SAC/TC 262).

Drafting organizations of this document: China Special Equipment Inspection and Research Institute, Hefei General Machinery Research Institute Co., Ltd., Morimatsu (Jiangsu) Heavy Industry Co., Ltd., Institute of Acoustics of the Chinese Academy of Sciences, China Energy Engineering Group Anhui Electric Power Construction First Engineering Co., Ltd., Zhejiang Provincial Special Equipment Science Research Institute, CFHI Dalian Nuclear Petrochemical Co., Ltd., Huludao Beijian Technology Co., Ltd., Jiangsu Zhongte Testing Co., Ltd., North China Nuclear and Radiation Safety Supervision Station of the Ministry of Ecology and Environment, Tianjin Da'ante Engineering Testing Co., Ltd., Guangzhou Doppler Electronic Technology Co., Ltd., and Beijing Zouzhan Lucheng Technology Co., Ltd.

Main drafters of this document: Zheng Hui, Yan Changzhou, Hou Jingang, Jiang Yanshan, Lian Guoxuan, Sun Lei, Guo Weican, Pan Qianghua, Yang Qi, Zhou Fengge, Wang Xiaomei, Tian Guoliang, Jin Nanhui, Qiang Tianpeng, Duan Minjie, Chen Yimin, Ji Xuanrong and Li Jianfeng.

This document is issued for the first time.

1 Scope

NB/T 47013.15-2021 is Part 15 of the Chinese standard for non-destructive testing of pressure equipment, and it covers phased-array ultrasonic testing. A phased-array probe holds many small elements that are fired with controlled delays, so the beam can be steered and focused electronically instead of by moving the probe or changing the wedge: one probe sweeps a range of angles, and the result can be displayed as a sectorial image of the weld rather than a single trace. That capability is what this part regulates. It fixes the qualification of the personnel who perform and interpret the examination, the equipment and its verification - array probes, wedges, instruments and reference blocks - and the checks made on the system before and during the work. It then sets out the technique: the focal law and its validation, the angular range and focusing depth, the scan plan that proves the weld volume is covered, the sensitivity setting and the time-corrected gain, the encoder and scanning speed, and the recording of the data. Interpretation follows, with the characterisation, sizing and location of indications from the sectorial and linear images, and the acceptance levels by quality class. The examination report and the retention of the raw data close the document, since with phased array the data file is itself the record. It applies to welds and components in pressure vessels, boilers and pressure piping in China.

1.1 This document specifies the methods and the quality grading requirements for phased-array ultrasonic testing of pressure equipment. Phased-array ultrasonic testing carried out in accordance with the relevant technical requirements of this document is recordable pulse-echo ultrasonic testing.

1.2 This document applies to the phased-array ultrasonic testing of metallic raw materials, component parts and welded joints during the manufacture and the service of pressure equipment.

1.3 For the phased-array ultrasonic testing of electrofusion joints of polyethylene piping, reference may be made to Annex A (informative).

1.4 For the phased-array ultrasonic testing of materials and structures used in pressure equipment, and of their welded joints, that are not expressly specified in this document, this document may be applied by reference where process validation shows that the testing requirements can be met; the phased-array ultrasonic testing of supports and structural parts related to pressure equipment may also be carried out by reference to this document.

2 Normative references

The contents of the following documents constitute indispensable provisions of this document through the normative references made to them in the text. For dated references, only the edition corresponding to that date applies to this document; for undated references, the latest edition (including all amendments) applies to this document.

GB/T 699 Quality carbon structural steels.

GB/T 11259 Non-destructive testing - Practice for fabrication and control of steel reference blocks used in ultrasonic testing.

GB/T 12604.1 Non-destructive testing - Terminology - Ultrasonic testing.

GB/T 29302 Non-destructive testing instruments - Performance and verification of phased-array ultrasonic testing systems.

GB/T 29460 Safety assessment of polyethylene piping electrofusion joints containing defects.

DL/T 694-2012 Technical guide for ultrasonic testing of high-temperature fastening bolts.

JB/T 8428 Non-destructive testing - General specification for ultrasonic test blocks.

JB/T 9214 Non-destructive testing - Test method for the operating performance of A-mode pulse-echo ultrasonic testing systems.

JB/T 10062 Test methods for the performance of probes used in ultrasonic flaw detection.

JB/T 11731 Non-destructive testing - General technical requirements for ultrasonic phased-array probes.

JB/T 11779 Non-destructive testing instruments - Technical requirements for phased-array ultrasonic testing instruments.

NB/T 47013.1 Nondestructive testing of pressure equipments - Part 1: General requirements.

NB/T 47013.3 Nondestructive testing of pressure equipments - Part 3: Ultrasonic testing.

NB/T 47013.10 Nondestructive testing of pressure equipments - Part 10: Time of flight diffraction ultrasonic testing.

JJF 1338 Calibration specification for phased-array ultrasonic flaw detectors.

ASTM E-317 Standard practice for evaluating performance characteristics of ultrasonic pulse-echo testing instruments and systems without the use of electronic measurement instruments.

3 Terms and definitions

For the purposes of this document, the terms and definitions given in GB/T 12604.1, GB/T 29460 and NB/T 47013.1 and the following apply.

3.1 coordinate definition. The definition specifying the testing origin reference point O and the meaning of the X, Y and Z coordinates. For a welded joint, the coordinate definition is as shown in Figure 1, where O is the established testing origin reference point, X is the coordinate along the direction of the weld length, Y is the coordinate along the direction of the weld width, and Z is the coordinate along the direction of the weld thickness.

3.2 phased-array ultrasonic testing. An ultrasonic testing method in which the individual piezoelectric elements of an array probe are excited according to a set delay law so as to synthesize a sound beam and to achieve functions such as beam movement, beam steering and beam focusing, and in which the ultrasonic signals received by each element are then processed according to a given delay law and the internal condition of the object under test is displayed in the form of an image.

3.3 delay law. The control law used for beam forming and for the reception and synthesis of ultrasonic signals; it generally refers to the sequence and the time intervals of the circuits of the individual elements of the array probe that take part in the transmission and the reception of the ultrasonic waves.

3.4 active aperture. The size of the group of elements excited at one time in an array probe. For a one-dimensional linear array probe, where the size of the group of elements excited at one time is as shown in Figure 2, the length of the active aperture is the dimension A in the active direction (also called the active aperture), and the width of the active aperture is the element length w. The value of A is calculated by formula (1): A equals n times e plus g times the quantity n minus one, which equals n times p minus g. In the formula, A is the length of the active aperture, g is the gap between adjacent elements, e is the element width, n is the number of excited elements, p is the centre-to-centre distance between two adjacent elements (the pitch), and w is the element length.

3.5 probe effluence point. The point at which the centre of the sound beam formed by the excited group of probe elements leaves the wedge.

3.6 electronic scanning. The use of a specific delay law to control the individual elements in an array probe so that the sound beam they produce can also be moved within the region of the workpiece under test while the probe itself remains stationary; it includes linear scanning, sectorial scanning and dynamic focusing.

3.7 linear electronic scanning (L-scan). The successive application of the same delay law to different element groups of the same array probe, so as to move the sound beam along the direction of the length of the phased-array probe, an effect similar to the scanning movement of a probe in A-mode pulse-echo ultrasonic testing.

3.8 sectorial electronic scanning (S-scan). The successive application of different steering delay laws to the same element group, so as to move the sound beam by steering it within a given angular range.

3.9 scan. The relative movement between the probe and the workpiece; it may be performed manually by the testing personnel or by mechanical scanning.

3.10 mechanical scan. A way of moving the probe by means of a mechanical device. For welded joints, according to the relationship between the direction of probe movement and the direction of the weld length, it may be divided into longitudinal scan, transverse scan, oblique scan and other modes.

3.11 longitudinal scan. A mode of mechanical scanning in which the probe moves along the direction of the weld length (that is, along the X-axis direction in Figure 1) at a position a given distance S from the weld centre line. According to the relative relationship between the direction of the probe sound beam and the direction of probe movement, it is divided into longitudinal scan with perpendicular beam, longitudinal scan with oblique beam and longitudinal scan with parallel beam.

3.12 longitudinal scan with perpendicular beam. A mode of longitudinal scanning in which the probe moves along the direction of the weld length and the direction of the incident sound beam of the probe is perpendicular to the direction of movement, as shown in Figure 3.

3.13 longitudinal scan with oblique beam. A mode of longitudinal scanning in which the probe moves along the direction of the weld length and the direction of the incident sound beam of the probe forms a given included angle with the direction of movement, as shown in Figure 4.

3.14 longitudinal scan with parallel beam. A mode of longitudinal scanning in which the probe moves along the direction of the weld length and the direction of the incident sound beam of the probe is parallel to the direction of movement, as shown in Figure 5.

3.15 transverse scan. A mode of mechanical scanning in which the probe moves along the direction of the weld width (that is, along the Y-axis direction in Figure 1). It generally refers to the transverse parallel scanning mode, in which the direction of the probe sound beam is parallel to the direction of probe movement, as shown in Figure 6.

3.16 probe frontier position. When testing a welded joint, the distance S between the front end of the probe wedge and the weld centre line, as shown in Figure 3.

3.17 angle corrected gain (ACG). A mode of gain correction by which sound beams at different angles within the sectorial scanning angular range that detect a reflector of the same sound path and the same size give echo amplitudes that are equalized.

3.18 time corrected gain (TCG). A mode of gain correction by which sound beams at the same angle that detect reflectors of the same size at different sound paths give echo amplitudes that are equalized.

3.19 B-display. The sound field image formed in the section that is parallel to the longitudinal section of the sound beam and perpendicular to the scanning surface of the workpiece. For a welded joint it is a projection image in the YOZ plane, as shown in Figure 7, in which the abscissa represents the weld width and the ordinate represents the depth or the sound path, the signal amplitude being displayed in different colours.

3.20 C-display. The sound field image formed in the section parallel to the scanning surface of the workpiece. For a welded joint it is a projection image in the XOY plane, as shown in Figure 7, in which the abscissa represents the weld length or the scanning distance and the ordinate represents the size of the region covered by the sound beam, the signal amplitude being displayed in different colours.

3.21 D-display. The sound field image formed in the section that is perpendicular both to the longitudinal section of the sound beam and to the scanning surface of the workpiece. For a welded joint it is a projection image in the XOZ plane, as shown in Figure 7, in which the abscissa represents the weld length or the scanning distance and the ordinate represents the depth or the sound path, the signal amplitude being displayed in different colours.

3.22 S-display. The fan-shaped image display formed by the sound beam of a sectorial scan, as shown in Figure 8, in which the abscissa of the image represents the position away from the probe effluence point, the ordinate represents the depth, and the coordinate along the direction of the fan-shaped arc represents the angle, the signal amplitude being displayed in different colours. When testing a welded joint, the S-display shows the internal condition of the longitudinal section of the region in front of the probe.

3.23 V-scan presentation. An imaging display mode in which the testing results are displayed in three-dimensional (spatial) form within the volume of the region under test, the signal amplitude being represented by different colours.

3.24 total focusing method (TFM). A special phased-array ultrasonic testing technique implemented by exciting one element (or several elements) at a time within the active aperture of the array probe while all elements (or a set group of elements) receive, so that, after all the elements (or element groups) have been excited in turn, each point of the gridded target region is computed and imaged according to the delay law. Its usual forms of implementation include FMC (full matrix capture), AFM (adaptive total focusing) and PWI (plane wave imaging).

3.25 relevant indication. An indication caused by a defect.

3.26 non-relevant indication. An indication caused by the structure of the workpiece (such as the weld reinforcement or the weld root, or a change in the geometrical structure of the workpiece) or by a deviation in the metallurgical structure of the material (for example the interface between the base metal and the cladding layer); it includes indications caused by misalignment, by the root and cap weld passes, and by changes in the shape of the groove.

4 General requirements

4.1 Testing personnel.

4.1.1 The requirements for phased-array ultrasonic testing personnel shall comply with the relevant provisions of NB/T 47013.1.

4.1.2 Personnel engaged in the phased-array ultrasonic testing of raw materials of simple geometrical shape, of pressure-retaining parts and of ferritic steel butt-welded joints shall possess basic knowledge of metallic materials, welding, heat treatment and the manufacture and installation of pressure equipment; personnel engaged in the phased-array ultrasonic testing of other objects shall in addition master knowledge of the relevant materials, structures, manufacturing processes and sound field modelling, shall have undergone dedicated training, and shall possess the required technical ability and the corresponding testing experience.

4.2 Testing equipment and accessories.

4.2.1 Testing equipment. The testing equipment comprises the testing instrument together with all the items connected to it, such as the probe, the scanning device and the cables; accessories are the other devices and materials that are needed to realize the testing function but are not connected to the instrument, including test blocks and couplant. The performance of the testing equipment and accessories shall meet the requirements of this document, and their functions shall satisfy the process requirements of the object being tested.

4.2.2 Testing instrument and probe.

4.2.2.1 The testing instrument shall at least provide multi-channel ultrasonic transmission, reception, amplification, automatic data acquisition, recording, display and analysis functions; the instrument shall comply with the corresponding product standard and shall have a product quality conformity certificate, and that certificate shall at least include the main parameters of warm-up time, low-voltage alarm or low-voltage automatic shutdown voltage, transmission pulse repetition frequency, effective output impedance, transmission pulse voltage, transmission pulse rise time, transmission pulse width (when a square-wave pulse is used as the transmission pulse), transmission delay accuracy, amplifier frequency response, attenuator accuracy, dynamic range and crosstalk; the electrical performance and the basic functions of the instrument shall satisfy the requirements of Annex C (normative), and a certification document issued by a third-party laboratory accredited to ISO/IEC 17025 shall be supplied for each specification and model; the data recording and transmission format of the testing instrument should adopt the format specified in Annex B (informative).

4.2.2.2 The probe shall comply with the corresponding product standard and shall have a product quality conformity certificate, and that certificate shall at least include the main parameters of probe dimensions, centre frequency, bandwidth, electrical impedance or static capacitance, number of elements, position of the first element and position of the last element, element pitch, crosstalk between elements and pulse-echo sensitivity; the performance indices of the probe shall satisfy the requirements of Annex D (normative), and a certification document issued by a third-party laboratory accredited to ISO/IEC 17025 shall be supplied for each specification and model.

4.2.2.3 Requirements for the testing instrument, the probe and their combined performance.

4.2.2.3.1 The combined performance of the testing instrument and the probe includes vertical linearity, horizontal linearity, attenuator accuracy, combined frequency, and the transverse resolution, the longitudinal resolution and the sectorial angular resolution of sectorial imaging; the test methods and the acceptance requirements for the combined performance are given in Table 1.

Table 1, item 1: vertical linearity, test method standard JB/T 9214, requirement: deviation not greater than 5%.

Table 1, item 2: horizontal linearity, test method standard GB/T 29302, requirement: deviation not greater than 1%.

Table 1, item 3: attenuator accuracy, test method standard JJF 1338, requirement: for any continuous 20 dB, the cumulative error of the attenuator shall be not greater than 1 dB; for any continuous 60 dB, the cumulative error of the attenuator shall be not greater than 2 dB.

Table 1, item 4: combined frequency, test method standard JB/T 10062, requirement: when a phased-array ultrasonic probe with a frequency of 5 MHz is used, the deviation between the combined frequency of the instrument and the probe and the nominal frequency marked on the probe shall be not greater than plus or minus 10%.

Table 1, item 5: transverse and longitudinal resolution of sectorial imaging, test method standard JJF 1338, requirement: when a phased-array ultrasonic probe with a frequency of 5 MHz is used, both shall be not greater than 2 mm.

Table 1, item 6: deviation in the measurement of the sectorial angular range, test method standard JJF 1338, requirement: when a phased-array ultrasonic probe with a frequency of 5 MHz is used, it shall not exceed plus or minus 3 degrees.

Table 1, item 7: sectorial angular resolution, test method standard JJF 1338, requirement: when a phased-array ultrasonic probe with a frequency of 5 MHz is used, it shall be not greater than 5 degrees.

4.2.2.3.2 The combined performance of the instrument and the probe shall be measured when any of the following occurs: a) a newly purchased phased-array ultrasonic instrument and (or) probe; b) after repair or replacement of major components of the instrument, the probe or the connecting cables; c) the testing personnel have doubts.

4.2.2.4 Scanning device.

4.2.2.4.1 In order to carry out mechanical scanning and to ensure that the movement path of the probe stays consistent with the reference line, a scanning device should be used.

4.2.2.4.2 A scanning device generally comprises a probe holding part, a driving part, a guiding part and a position sensor.

4.2.2.4.3 The probe holding part shall be able to adjust and set the position of the probe and to keep the relative distance and the relative angle of the probe unchanged during scanning.

4.2.2.4.4 The guiding part shall be able to keep the direction of movement of the probe consistent with the set direction during scanning.

4.2.2.4.5 The driving part may be driven by a motor or by hand.

4.2.2.4.6 The positional resolution of the position sensor in the scanning device shall comply with the process requirements of the relevant contents of this document.

4.2.2.5 Requirements for specific functions of the testing equipment.

4.2.2.5.1 When various objects are tested, the testing equipment shall possess the functions required by the relevant process contents of this document.

4.2.2.5.2 When phased-array ultrasonic testing is carried out on welded joints of nozzle corner shape or of other complex structural form and on pressure-retaining parts, the testing equipment shall possess an object modelling function, and shall at least be able to perform structural simulation of the contour line of the workpiece and the corresponding analysis of the testing data.

4.2.3 Test blocks.

4.2.3.1 Standard test blocks.

4.2.3.1.1 A standard test block is a material block having a specified chemical composition, surface roughness, heat treatment and geometrical shape, used to evaluate and calibrate phased-array ultrasonic testing equipment, that is, a test block used for the performance calibration of the instrument-probe system. The standard test blocks adopted in this document are CSK-IA, DB PZ20-2, the type A phased-array test block and the type B phased-array test block.

4.2.3.1.2 The specific shape and dimensions of the CSK-IA test block are as specified in NB/T 47013.3, the specific shape and dimensions of DB PZ20-2 are as specified in JB/T 9214, the type A phased-array test block is shown in Figure 9 and the type B phased-array test block is shown in Figure 10.

Figure 9, type A phased-array test block, dimensions in millimetres: the groove width is 0.5 mm and the groove depths are, from left to right, 0.1 mm, 0.2 mm, 0.3 mm and 0.4 mm; the block is 300 mm long, 100 mm and 91 mm in the plan dimensions indicated, 25 mm and 20 mm in thickness at the steps, and carries radii R50, R100 and R10, angles of 5 degrees, 10 degrees, 20 degrees and 45 degrees, side-drilled holes of 1 mm and 2 mm diameter and flat-bottomed holes of 2 mm diameter, together with an enlarged view of zone I showing 45-degree reflectors.

Figure 10, type B phased-array test block, dimensions in millimetres: overall 150 mm by 100 mm by 25 mm, with engraved grooves of 0.5 mm depth, radii R25 and R50, eighteen through holes of 2 mm diameter, eighteen through holes of 1 mm diameter, sixteen through holes of 1 mm diameter, twelve through holes of 15 mm, angular steps of 2.5 degrees, 3 degrees and 5 degrees, and hole spacings of eleven times 5 equals 55 mm and eleven times 2.5 equals 27.5 mm.

4.2.3.1.3 The manufacture and the dimensional accuracy of standard test blocks shall satisfy the requirements of JB/T 8428; the manufacturer shall provide a product quality conformity certificate and shall ensure that, when each standard test block it manufactures is compared under the same test conditions with a national standard sample or a similar standard test block having a traceable quantity value, the maximum difference in reflected amplitude from the same reflector (surface) is less than or equal to 2 dB.

4.2.3.2 Reference test blocks.

4.2.3.2.1 Reference test blocks are mainly used for testing calibration; according to the way they are made and to their use they may be divided into general-purpose reference blocks and dedicated reference blocks; a reference block shall contain reference reflectors of clear significance produced by machining.

4.2.3.2.2 General-purpose reference blocks: a) the geometrical shape, the dimensions and the arrangement of the reference reflectors of a general-purpose reference block shall be as specified in the drawings of the corresponding contents of this document, and its dimensional accuracy shall satisfy the requirements of JB/T 8428; b) the material used to make a general-purpose reference block shall be No. 20 quality carbon structural steel melted in an electric furnace or an open-hearth furnace, whose chemical composition complies with the requirements of GB/T 699, and which after forging and forming is normalized in order to ensure that the material is uniform in structure and free from acoustic anisotropy, with a grain size of grade 7 to grade 8; when tested with a straight probe it shall contain no defect whose equivalent diameter is greater than or equal to that of a flat-bottomed hole of 2 mm diameter.

4.2.3.2.3 Dedicated reference blocks: a) the material, the external dimensions and the manufacturing process of a dedicated reference block shall be the same as, or similar to, those of the workpiece under test; b) when tested with a straight probe it shall contain no defect whose equivalent diameter is greater than or equal to that of a flat-bottomed hole of 2 mm diameter; c) the arrangement of the reference reflectors may follow the drawings of the corresponding contents of this document and shall satisfy the requirements of testing calibration and of equipment setting up; d) if it is used for the purpose of the process validation required by 4.3.3, consideration shall also be given to the type, size, position and orientation of the defects that may exist in the workpiece under test, and the corresponding reference reflectors shall be provided.

4.2.3.3 Simulation test blocks.

4.2.3.3.1 A simulation test block is a test block containing simulated defects, mainly used for the validation of the testing process.

4.2.3.3.2 The material and the acoustic properties of a simulation test block shall be the same as, or close to, those of the workpiece under test, and it shall contain no other defect that would affect the testing.

4.2.3.3.3 The external structure, the thickness and the surface condition of a simulation test block shall all be the same as, or close to, those of the workpiece under test.

4.2.3.3.4 For welded joints, the simulated defects shall be prepared by welding methods or shall be real defects found in previous testing; for a workpiece under test other than a welded joint, the simulated defects shall have the morphology and the acoustic characteristics of real defects.

4.2.3.3.5 The type, position, size and number of the simulated defects shall be set with consideration of the defect conditions that may exist in the workpiece under test. For welded joints they shall at least include longitudinal and transverse defects, volumetric and planar defects, and surface and buried defects, and their size shall generally be not greater than the maximum permissible defect size specified for grade II for a workpiece of the same thickness; they may be made up of one block or of several blocks covering a range of thicknesses.

4.2.4 Couplant.

4.2.4.1 The couplant shall have good sound transmission properties and shall not damage the surface of the workpiece under test; examples are machine oil, chemical paste, glycerine and water.

4.2.4.2 The couplant shall be stable and reliable within the temperature range specified in the process documents.

4.2.5 Calibration, checking, operational checking and inspection of the testing equipment.

4.2.5.1 General requirements. Calibration, checking, operational checking and inspection should generally be carried out using standard test blocks and reference test blocks; during the operation the main sound beam of the probe shall be aimed perpendicularly at the reflecting surface of the reflector in order to obtain a stable and maximum reflected signal; controls that affect the linearity of the instrument (such as the suppression or filter switches) shall all be set to the off position or to the lowest level.

4.2.5.2 Calibration or checking. At least once a year the vertical linearity, the horizontal linearity, the attenuator accuracy, the combined frequency, the transverse and longitudinal resolution of sectorial imaging, the sectorial angular range and the sectorial angular resolution among the combined performance characteristics of the testing instrument and the probe shall be calibrated and recorded once, and the test requirements shall satisfy the provisions of 4.2.2.3.1.

4.2.5.3 Operational checking.

4.2.5.3.1 At intervals of not more than 6 months, the vertical linearity and the horizontal linearity among the combined performance characteristics of the instrument and the probe shall be operationally checked and recorded once, and the test requirements shall satisfy the provisions of 4.2.2.1.

4.2.5.3.2 At intervals of not more than 1 month, the effectiveness of the elements shall be operationally checked once; a phased-array probe is allowed to have dead elements, but the number of dead elements shall not exceed one quarter of the total number of elements of the probe, and consecutive dead elements among adjacent elements are not permitted.

4.2.5.4 Inspection.

4.2.5.4.1 Before each test, the appearance of the instrument, equipment and accessories, the cable connections and the start-up signal display shall be inspected to check whether they are normal.

4.2.5.4.2 Before each test the position sensor shall be inspected and the inspection recorded; the method of inspection is to move the scanning device carrying the position sensor by at least 300 mm and to compare the displacement shown by the testing instrument with the actual displacement, the error of which shall be less than 1%.

4.3 Testing process.

4.3.1 Testing process documents.

4.3.1.1 The testing process documents comprise the process specification and the operating instruction.

4.3.1.2 In addition to satisfying the requirements of NB/T 47013.1, the process specification shall also specify the particular ranges or requirements of the relevant factors listed in Table 2 and in the related contents. When a change in a relevant factor exceeds the specified range, the process specification shall be re-issued or revised.

Table 2, relevant factors involved in the phased-array ultrasonic testing process specification, item 1: the type and geometrical shape of the workpiece under test, including its specification, thickness, dimensions and product form.

Table 2, item 2: the requirements for the testing surface.

Table 2, item 3: the testing technique (linear scanning, sectorial scanning, direct contact method, immersion method, waveform and so on).

Table 2, item 4: the type of testing instrument.

Table 2, item 5: the type and parameters of the phased-array probe (element height and width, gap, number of elements).

Table 2, item 6: the dimensions and the angle of the wedge.

Table 2, item 7: the focusing range (depth or sound path).

Table 2, item 8: the size of the active aperture (number of excited elements, length and width of the active aperture).

Table 2, item 9: the scanning type (linear scanning, sectorial scanning).

Table 2, item 10: the type of couplant.

Table 2, item 11: calibration (test block and calibration method).

Table 2, item 12: the scanning direction and the scanning range.

Table 2, item 13: the scanning mode (longitudinal scan with perpendicular beam, longitudinal scan with parallel beam, longitudinal scan with oblique beam and so on).

Table 2, item 14: additional testing (where required) and its requirements.

Table 2, item 15: automatic alarm and/or recording devices (when used).

Table 2, item 16: the qualification requirements for personnel and the requirements for the testing report.

Table 2, item 17: the analysis and interpretation of the testing data.

Table 2, item 18: the acceptance level (quality grade).

4.3.1.3 The operating instruction shall be drawn up according to the requirements of the workpiece under test and of the process specification. In addition to satisfying the requirements of NB/T 47013.1, its contents shall also include: a) technical requirements for testing: the timing of testing, the proportion to be tested, the acceptance level and so on; b) testing equipment and accessories: the testing instrument, the probe, the wedge, the couplant, the scanning device, the name and specification and model of the test blocks, and the items, timing and acceptance requirements for the performance inspection of the equipment; c) testing process parameters: including the region to be covered by the testing, the coupling method, the scanning surface and its preparation requirements, the probe position, the scanning and the scanning mode, as well as the setting up and calibration of the testing system (active aperture, incidence angle, scanning range and step, focusing mode and depth, sensitivity, gates and display mode and so on), and the method of testing for transverse defects (where necessary).

4.3.1.4 Before it is applied for the first time, the operating instruction shall undergo process validation in accordance with the requirements of 4.3.3.

4.3.2 Technical requirements of the testing process.

4.3.2.1 Timing of testing. During the manufacture and the service of pressure equipment, the timing of testing shall comply with the provisions of the relevant laws, regulations, rules, product standards and related technical documents. Materials that have a tendency to delayed cracking shall be tested at least 24 h after the completion of welding.

4.3.2.2 Technical grades of testing.

4.3.2.2.1 The phased-array ultrasonic testing of raw materials and component parts used in steel pressure equipment is not divided into technical grades.

4.3.2.2.2 The phased-array ultrasonic testing of welded joints of steel pressure equipment is divided into the three technical grades A, B and C; where, for structural or other reasons, the requirements of a technical grade of testing cannot be fully satisfied, effective technical measures shall be adopted and a dedicated operating instruction shall be drawn up, and process validation shall be carried out in accordance with 4.3.3.

4.3.2.3 General testing methods for the different categories of objects under test.

4.3.2.3.1 For the testing of raw material tubes, oblique incidence of shear waves is generally used, with normal incidence of longitudinal waves added where necessary; for the testing of other raw materials and of the base metal of component parts, normal incidence of longitudinal waves is generally used, with oblique incidence of shear waves or of longitudinal waves added where necessary.

5 Phased-array ultrasonic testing methods and quality grading for raw materials or component parts used in pressure equipment

This clause begins on page 15 of the standard and specifies the phased-array ultrasonic testing methods and the quality grading for raw materials and component parts used in pressure equipment. The full text of the clause is not reproduced in this preview.

6 Phased-array ultrasonic testing methods and quality grading for welded joints of pressure equipment

This clause begins on page 29 of the standard and specifies the phased-array ultrasonic testing methods and the quality grading for welded joints of pressure equipment. The full text of the clause is not reproduced in this preview.

7 Testing records and report

This clause begins on page 51 of the standard and specifies the requirements for testing records and for the testing report. The full text of the clause is not reproduced in this preview.