NB/T 47013.3-2023Nondestructive testing of pressure equipments - Part 3: Ultrasonic testing (English PDF)

Foreword

This document was issued on 28 December 2023 by the National Energy Administration of the PRC and takes effect on 28 June 2024.

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.

It replaces NB/T 47013.3-2015, which is superseded.

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 is Part 3 of NB/T 47013, Nondestructive testing of pressure equipments. The following parts of NB/T 47013 have already been issued:

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: Digital radiographic imaging testing;

Part 12: Magnetic flux leakage testing;

Part 13: Pulsed eddy current testing;

Part 14: Computed radiographic testing;

Part 15: Phased array ultrasonic testing.

This document replaces NB/T 47013.3-2015, Nondestructive testing of pressure equipments - Part 3: Ultrasonic testing. In addition to structural adjustments and editorial changes, the following main technical changes have been made with respect to NB/T 47013.3-2015:

a) it has been made clear that reference blocks comprise general-purpose reference blocks and special reference blocks, and the applicable scope of each has been specified;

b) the requirements for process validation and the methods of process validation have been further clarified;

c) the applicable range of the ultrasonic testing of plates for pressure equipment has been adjusted, being extended from the range 6 mm to 250 mm to any thickness greater than or equal to 6 mm;

d) the applicable range for longitudinal butt joints of pressure equipment has been enlarged, changing from an inside-to-outside diameter ratio greater than or equal to 65 percent to an inside-to-outside diameter ratio greater than or equal to 60 percent;

e) a method for measuring the wall thickness of clad steel plates for pressure equipment has been added;

f) Annex E, Ultrasonic angle-probe testing method and quality grading for ring-shaped and cylindrical forgings of carbon steel and low alloy steel used in pressure equipment, has been revised as a whole: its applicable range has been enlarged, the reference blocks and the reference reflectors have been modified, and the testing method has been modified;

g) Annex F, Ultrasonic angle-probe testing method for austenitic stainless steel ring-shaped and cylindrical forgings used in pressure equipment, has been revised as a whole: its applicable range has been enlarged and the testing method has been modified;

h) Annex I, Ultrasonic testing method and quality grading for welded butt joints of austenitic stainless steel and nickel-based alloy in pressure equipment, has been revised as a whole: its applicable range has been enlarged, the reference blocks have been modified, testing technique levels have been added, and testing methods for longitudinal flaws and for transverse flaws have been specified;

i) a new informative Annex U, Ultrasonic testing methods for pressure equipment using imaging techniques, has been added, providing testing methods for recordable ultrasonic testing.

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: Hefei General Machinery Research Institute Co., Ltd.; China Special Equipment Inspection and Research Institute; Shanghai Electric Nuclear Power Equipment Co., Ltd.; China First Heavy Industries Group Dalian Hydrogenation Reactor Manufacturing Co., Ltd.; Morimatsu (Jiangsu) Heavy Industry Co., Ltd.; Institute of Acoustics of the Chinese Academy of Sciences; Zhejiang Academy of Special Equipment Science; Lanzhou LS Heavy Equipment Co., Ltd.; Sichuan Jiacheng Oil and Gas Pipeline Quality Testing Co., Ltd.; China Energy Engineering Group Zhejiang Thermal Power Construction Co., Ltd.; Wuhan Zhongke Innovation Technology Co., Ltd.; Shantou Institute of Ultrasonic Instruments Co., Ltd.; Zhejiang Youerte Testing Technology Co., Ltd.; Shandong Ruixiang Mould Co., Ltd.

Main drafters of this document: Yan Changzhou, Zheng Hui, Xu Zunyan, Zhou Fengge, Zhou Yufeng, Jiang Yanshan, Lian Guoxuan, Chen Xiantao, Jin Nanhui, Su Zaichun, Yuan Keyi, Cheng Jingwei, Wu Yong, Xu Yunwei, Lin Guanghui, Chen Honglong, Liu Zhanglong, Wei Zhongrui.

The successive editions of this document and of the documents it replaces are as follows:

JB 4730-1994;

JB/T 4730.3-2005;

NB/T 47013.3-2015.

1 Scope

NB/T 47013.3-2023 is Part 3 of the Chinese standard for non-destructive testing of pressure equipment, and it governs ultrasonic testing. The NB/T 47013 series is the reference an inspector applies to pressure vessels, boilers and pressure piping in China, and this part is the one that decides whether a weld or a forging is accepted on the evidence of an ultrasonic examination. It replaces the 2015 edition. The document fixes the qualification of the personnel who perform and evaluate the test, the equipment and its verification - flaw detectors, probes, cables and reference blocks - and the calibration performed before and during the examination. It then sets out the techniques themselves: contact pulse-echo testing of butt and corner welds in plate, pipe and nozzle geometries, testing of forgings, castings and bolting, thickness measurement, and the specialised methods including tandem, creeping wave and time-of-flight diffraction. For each it gives the surface preparation, the coupling, the scanning pattern and coverage, the sensitivity setting and the distance-amplitude correction, and the way an indication is characterised, sized and located. Acceptance levels are stated by quality class, together with the treatment of repairs and re-examination. The report content and the retention of records close the document. Anyone building, inspecting or certifying pressure equipment in China works to this text, and a Chinese reviewer checks a submitted ultrasonic report against it.

1.1 This document specifies the methods and the quality grading requirements for the ultrasonic testing of pressure equipment by means of the A-scan pulse-echo technique.

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

1.3 The ultrasonic testing of metallic support components and structural components associated with pressure equipment, including their welded joints, may be carried out with reference to the provisions of this document.

1.4 Where ultrasonic imaging techniques combining A-scan display with other display modes are used for testing, the provisions of this document may likewise be applied by reference.

2 Normative references

The contents of the following documents constitute indispensable provisions of this document through normative reference 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 - Manufacture and control of steel reference blocks used in ultrasonic testing.

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

GB/T 27664.1, Non-destructive testing - Characterization and verification of ultrasonic examination equipment - Part 1: Instruments.

GB/T 27664.2, Non-destructive testing - Characterization and verification of ultrasonic examination equipment - Part 2: Probes.

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

GB/T 30579, Damage modes identification of pressure equipment.

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-scan pulse-echo ultrasonic testing systems.

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

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

NB/T 47013.15, Nondestructive testing of pressure equipments - Part 15: Phased array ultrasonic testing.

ISO/IEC 17025, Testing and calibration laboratories.

3 Terms and definitions

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

3.1 reduction of backwall echo BG over BF. In the testing of forgings, the ratio between the amplitude BG of the first backwall echo obtained in a sound area close to the flaw and the amplitude BF of the first backwall echo obtained in the flaw area, expressed by the relative gain value in decibels of the two.

3.2 clustered indications. In the testing of forgings, five or more flaw reflection signals present at the same time within a cubic region of 50 mm edge length, the reflected amplitude of each of which is greater than or equal to the equivalent of a given flat-bottom hole.

3.3 reference sensitivity. The sensitivity obtained when the echo height of a reference reflector in a reference block, or the backwall echo height of the workpiece under test, is adjusted to a given datum.

3.4 evaluation sensitivity. The sensitivity obtained by adjusting the reference sensitivity to take account of factors such as the different surface roughness, the different curvature and the difference of material between the reference block and the workpiece under test. Evaluation sensitivity is used mainly for the testing of the workpiece and for the assessment of flaws.

3.5 scanning sensitivity. The sensitivity used for the actual scanning, obtained by suitably increasing the gain of the instrument, in decibels, above the evaluation sensitivity.

3.6 flaw height. The distance between the upper and lower extremities of a flaw measured in the direction of the workpiece thickness.

3.7 echodynamic patterns. The envelope of the variation of the echo amplitude of a reflector when the probe and the reflector are moved relative to each other.

3.8 base material thickness t. The thickness of the workpiece, defined as follows for raw materials and parts and for welded joints.

3.8 a) Raw materials and parts. 1) For plates and for tubes, the base material thickness t is their nominal thickness.

3.8 a) 2) For clad steel plates, the base material thickness t is the nominal thickness of the backing material.

3.8 a) 3) For ring-shaped or cylindrical forgings, the base material thickness t is the thickness of the shell; for disc-shaped or similar forgings, the base material thickness t is their minimum thickness; for other types of forging, the base material thickness t generally refers to the dimension in the testing direction, or to the dimension along the radial or the axial direction.

3.8 b) Welded joints. 1) For flat-plate butt joints, when the base material on the two sides of the weld has the same thickness, the base material thickness t is the nominal thickness of the base material; when the thickness of the base material on the two sides differs, the base material thickness t is the nominal thickness of the thinner base material.

3.8 b) 2) For set-in nozzle corner joints, the base material thickness t is the nominal thickness of the shell, of the head or of the header; for nozzle corner joints set on a shell, head or header, the base material thickness t is the nominal thickness of the nozzle.

3.8 b) 3) For T-shaped welded joints, the base material thickness t is the nominal thickness of the web plate.

4 General requirements

4.1 Testing personnel.

4.1.1 The general requirements for ultrasonic testing personnel shall comply with the provisions of NB/T 47013.1.

4.1.2 In addition to understanding and mastering the basic theory of ultrasonics and possessing the necessary practical experience, ultrasonic testing personnel shall also possess a certain basic knowledge of metallic materials, of equipment manufacture and installation, of welding and of heat treatment, shall be familiar with the material, the manufacturing process and the acoustic characteristics of the workpiece under test, and shall be able to analyse, judge and deal with the problems arising during testing.

4.2 Testing equipment and accessories.

4.2.1 Quality conformity certificates of the ultrasonic testing instrument, hereinafter referred to as the instrument, and of the probes. The quality conformity certificate of the instrument shall state at least the following main performance parameters: warm-up time; low-voltage alarm voltage or low-voltage automatic shut-down voltage; transmitting pulse repetition frequency; effective output impedance; transmitting pulse voltage; transmitting pulse rise time; transmitting pulse width, where a square-wave pulse is used as the transmitting pulse; and the frequency band of the receiving circuit. The quality conformity certificate of the probe shall state the following main parameters: centre frequency; bandwidth; electrical impedance and static capacitance; relative pulse-echo sensitivity; and the sound-beam performance of angle probes, including the incidence point or front edge of the probe and the refraction angle beta of the probe or its K value.

4.2.2 Instrument, probes and combined performance.

4.2.2.1 Instrument. An A-scan pulse-echo ultrasonic testing instrument shall be used; its working frequency, measured at minus 3 dB, shall cover at least the frequency range from 0.5 MHz to 10 MHz. The performance indexes of the instrument shall satisfy the requirements of Annex A, and for each specification and model a certificate issued by a third-party laboratory accredited in accordance with ISO/IEC 17025 shall be provided.

4.2.2.2 Probes. The diameter of a circular crystal shall generally be less than or equal to 40 mm, and any side of a square crystal shall generally be not greater than 40 mm. The performance indexes of the probe shall satisfy the requirements of Annex B, and for each specification and model a certificate issued by a third-party laboratory accredited in accordance with ISO/IEC 17025 shall be provided.

4.2.2.3 Combined performance of instrument and probe.

4.2.2.3.1 The combined performance of the instrument and the probe comprises horizontal linearity, vertical linearity, combined frequency, sensitivity margin, dead zone, for straight probes only, and far-field resolution.

4.2.2.3.2 The combined performance of the instrument and the probe shall be determined in any one of the following circumstances: a) a newly purchased ultrasonic testing instrument and, or, probe; b) after the instrument or the probe has been repaired or has had a main component replaced; c) when the testing personnel have doubts.

4.2.2.3.3 The horizontal linearity deviation shall be not greater than 1 percent and the vertical linearity deviation shall be not greater than 5 percent.

4.2.2.3.4 The deviation between the combined frequency of the instrument and the probe and the nominal frequency of the probe shall be not greater than 10 percent.

4.2.2.3.5 The combined performance of the instrument and a straight probe shall further satisfy the following requirements: a) the sensitivity margin shall be not less than 32 dB; b) at the evaluation sensitivity, the dead zone shall be not greater than 10 mm for a probe of 5 MHz nominal frequency and not greater than 15 mm for a probe of 2.5 MHz nominal frequency; c) the far-field resolution of the straight probe shall be not less than 20 dB.

4.2.2.3.6 The combined performance of the instrument and an angle probe shall further satisfy the following requirements: a) the sensitivity margin shall be not less than 42 dB; b) the far-field resolution of the angle probe shall be not less than 12 dB.

4.2.2.3.7 At the maximum sound path to be examined in the workpiece, the effective sensitivity margin shall be not less than 10 dB.

4.2.2.3.8 The test method for the combined frequency of the instrument and the probe shall comply with the provisions of JB/T 10062, and the test methods for the other combined performance characteristics shall comply with the provisions of JB/T 9214.

4.2.3 Test blocks.

4.2.3.1 Standard blocks.

4.2.3.1.1 A standard block shall be a block of material having a specified chemical composition, surface roughness, heat treatment condition and geometrical shape, used to evaluate and calibrate the performance of the instrument-probe system. The standard blocks adopted in this document are CSK-IA, DZ-I and DB-P Z20-2.

4.2.3.1.2 The specific geometrical shape, dimensions and surface roughness of the CSK-IA block shall comply with the provisions of this document; the specific geometrical shape, dimensions and surface roughness of the DZ-I block and of the DB-P Z20-2 block shall comply with the provisions of JB/T 9214.

4.2.3.1.3 The manufacture and the dimensional accuracy of standard blocks shall comply with the provisions of JB/T 8428. The manufacturer shall provide a product quality conformity certificate and shall ensure that, when each standard block it manufactures is compared under identical measuring conditions with a national reference sample or with a similar standard block having value-transfer traceability, the difference of maximum reflected amplitude for the same reflector, or reflecting surface, is less than or equal to 2 dB.

4.2.3.2 Reference blocks.

4.2.3.2.1 A reference block shall be a block whose acoustic characteristics are similar to those of the test piece or of the material under test, containing reference reflectors of defined significance, used to adjust the amplitude and, or, the time base of the ultrasonic testing instrument, so that the discontinuity signals detected, that is the flaw signals, can be compared with the signals produced by the reference reflectors.

4.2.3.2.2 Where testing is carried out with a straight probe, the raw material used for the reference block shall not contain flaws with an equivalent greater than or equal to that of a flat-bottom hole of 2 mm diameter.

4.2.3.2.3 The shape, the dimensions and the number of the reference reflectors of the reference blocks used for the ultrasonic testing of different workpieces shall comply with the provisions of the relevant clauses and annexes of this document.

4.2.3.2.4 The dimensional tolerances of reference blocks shall be as manufactured in accordance with this document where explicit requirements are given in this document; where no explicit requirement is given, they shall be as manufactured in accordance with the provisions of JB/T 8428.

4.2.3.2.5 Reference blocks are divided into general-purpose reference blocks and special reference blocks.

4.2.3.2.5.1 General-purpose reference blocks. a) The geometrical shape, the dimensions and the arrangement of the reference reflectors of general-purpose reference blocks shall be as specified in the figures of the relevant clauses of this document, and their dimensional accuracy shall satisfy the requirements of JB/T 8428. b) General-purpose reference blocks shall be manufactured from grade 20 quality carbon structural steel produced in an electric furnace or by open-hearth smelting, whose chemical composition complies with GB/T 699; after forging and forming they shall be normalized so as to ensure that the material quality is uniform and free of acoustic anisotropy, with a grain size of grade 7 to grade 8; when tested with a straight probe they shall not contain flaws with an equivalent greater than or equal to that of a flat-bottom hole of 2 mm diameter.

4.2.3.2.5.2 Special reference blocks. a) The acoustic properties of the material of a special reference block and of the workpiece under test shall be such that the sound-velocity deviation between them does not exceed plus or minus 1 percent and the difference of the attenuation coefficient measured with a 5 MHz probe does not exceed plus or minus 2 dB per metre, and the manufacturing process shall be the same as, or similar to, that of the workpiece. b) The external geometrical dimensions of a special reference block shall be able, to a certain extent, to represent the features of the workpiece under test, and the block thickness shall correspond to the thickness of the workpiece under test; where the testing of butt joints between workpieces of different thickness is involved, the block thickness shall be selected on the basis of the greater workpiece thickness. c) Where the block is also used for the purposes of the process validation specified in 4.3.3, consideration shall further be given to the type, size, position and orientation of the flaws that may be present in the workpiece under test, and corresponding reference reflectors shall be provided.

4.2.3.2.5.3 General principles for the selection of reference blocks: a) for raw materials, parts or welded joints made of carbon steel or low alloy steel, general-purpose reference blocks may be used; b) for raw materials, parts or welded joints made of medium alloy steel or high alloy steel, special reference blocks shall be used; c) where a difference in the testing result arises from the different type of block selected, the result obtained with the special reference block shall prevail.

4.2.3.3 Simulation blocks.

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

4.2.3.3.2 The material and the acoustic characteristics of the simulation block shall be the same as, or similar to, those of the workpiece under test: the sound-velocity deviation shall be not greater than 1 percent and the difference of the attenuation coefficient measured with a 5 MHz probe shall be not greater than 2 dB per metre. Where the block is tested with a straight probe, the raw material used for it shall not contain flaws with an equivalent greater than or equal to that of a flat-bottom hole of 2 mm diameter.

4.2.3.3.3 The geometrical shape, the thickness and the surface condition of the simulation block shall all be the same as, or similar to, those of the workpiece under test.

4.2.3.3.4 For welded joints, the simulated flaws shall be produced by the same welding method as that used for the workpiece under test, or use shall be made of real flaws found in previous testing; for workpieces other than welded joints, the simulated flaws shall have a morphology and acoustic characteristics similar to those of real flaws.

4.2.3.3.5 The type, the position, the size and the number of the simulated flaws shall be arranged taking account of the flaw conditions that may be present in the workpiece under test. For welded joints, they shall include at least longitudinal and transverse flaws, volumetric and planar flaws, and surface and buried flaws; the flaw length shall generally be not greater than the maximum allowable flaw dimension specified, for the same workpiece thickness, by the corresponding acceptance quality grade of the pressure equipment. The simulated flaws may be distributed over one block or over several blocks within the same thickness range.

4.2.4 Couplant.

4.2.4.1 The couplant shall have good sound transmission and shall not damage the testing surface; engine oil, chemical paste, glycerine and water may be used.

4.2.4.2 Control of the content of contaminants in the couplant.

4.2.4.2.1 The sulfur content of the couplant used on nickel-based alloys shall be not greater than 250 mg per litre.

4.2.4.2.2 The total halogen content, that is chlorine and fluorine, of the couplant used on austenitic stainless steel or on titanium material shall be not greater than 250 mg per litre.

4.2.5 Requirements for the calibration, verification, in-service verification and inspection of ultrasonic testing equipment and accessories.

4.2.5.1 Calibration, verification and in-service verification shall be carried out on standard blocks and on reference blocks, with the main sound beam of the probe aligned perpendicularly to the reflecting surface of the reflector, so as to obtain a stable and maximum reflected signal.

4.2.5.2 Calibration or verification.

4.2.5.2.1 At least once a year the horizontal linearity and the vertical linearity, the combined frequency, the dead zone, for straight probes only, the sensitivity margin and the resolution among the combined performance characteristics of the ultrasonic testing instrument and the probe, together with the accuracy of the attenuator of the instrument, shall be calibrated once and recorded; the test requirements shall comply with the provisions of 4.2.2.3.

4.2.5.2.2 At least once a year the standard blocks and the reference blocks shall be verified once for surface corrosion and mechanical damage.

4.2.5.2.3 At least once every 5 years it is advisable to verify once the echo amplitude of the same reflector, or reflecting surface, of the standard block against a national reference sample or against a similar standard block having value-transfer traceability; the difference of the values shall be less than or equal to 2 dB.

4.2.5.3 In-service verification.

4.2.5.3.1 For analogue ultrasonic testing instruments every 3 months, and for digital ultrasonic testing instruments every 6 months, the horizontal linearity and the vertical linearity among the combined performance characteristics of the instrument and the probe shall be verified in service at least once and recorded; the test requirements shall comply with the provisions of 4.2.2.3.

4.2.5.3.2 At least once every 3 months the dead zone, for straight probes only, the sensitivity margin and the resolution shall be verified in service once and recorded; the test requirements shall comply with the provisions of 4.2.2.3.

4.2.5.4 Inspection.

4.2.5.4.1 Before each test the ultrasonic testing equipment and accessories shall be inspected to establish whether the external appearance, the cable connections and the signal display at power-on are normal.

4.2.5.4.2 Where angle probes are used, the incidence point of the probe, that is the front edge, and the refraction angle of the probe, that is the K value, shall be determined before testing.

4.2.5.5 Precautions during calibration, in-service verification and inspection. During calibration, in-service verification and inspection, the controls that affect the linearity of the instrument, such as the reject or suppression control and the filter switches, shall all be set to the off position or shall be kept at the lowest level.

4.3 Testing process.

4.3.1 Testing process documents.

4.3.1.1 The testing process documents consist of the testing procedure and the operating instruction.

4.3.1.2 Testing procedure.

4.3.1.2.1 The testing procedure shall comply with the provisions of NB/T 47013.1.

4.3.1.2.2 The testing procedure shall be prepared by the testing organization on the basis of the relevant laws and regulations, the product standards, the relevant technical documents and the provisions of this document.

4.3.1.2.3 The testing organization shall also prepare the testing procedure on the basis of its own characteristics, technical capability and resource conditions.

4.3.1.2.4 Where the relevant laws and regulations, product standards, relevant technical documents or provisions of this document on which the testing procedure is based are modified, or where the characteristics, the technical capability or the resource conditions of the testing organization on which it is based change, the testing organization shall re-prepare or revise the testing procedure.

4.3.1.2.5 The testing procedure shall specify the applicable range or the requirements for the relevant factors listed in Table 1 and in the relevant clauses and annexes. Where the variation of a relevant factor exceeds the specified range or requirement, with the exception of items 13 to 16 of Table 1, the testing organization shall revise the testing procedure.

Table 1, relevant factors to be covered by the ultrasonic testing procedure, item 1: shape of the workpiece, including specification, material and the like.

Table 1, item 2: selection of the testing surface, or side.

Table 1, item 3: testing technique, such as straight-probe testing, angle-probe testing, direct contact technique, immersion technique and the like.

Table 1, item 4: refraction angle, that is K value, of the angle probe and the wave mode inside the workpiece, transverse wave or longitudinal wave; nominal frequency of the straight probe or of the angle probe; crystal size, crystal shape and number of crystals.

Table 1, item 5: type of testing instrument.

Table 1, item 6: calibration, that is blocks and calibration method.

Table 1, item 7: scanning direction and scanning range.

Table 1, item 8: scanning mode, manual or automatic.

Table 1, item 9: method of discrimination between structural echoes and flaw signals.

Table 1, item 10: methods of flaw sizing and of flaw assessment.

Table 1, item 11: scanning coverage requirements.

Table 1, item 12: personnel qualification requirements.

Table 1, item 13: requirements for the surface condition of the testing surface or of the block.

Table 1, item 14: type or brand of the couplant.

Table 1, item 15: method of computer data acquisition, when used; whether automatic alarm and, or, automatic recording devices are required, when used.

Table 1, item 16: requirements for testing records and reports.

4.3.1.3 Operating instruction.

4.3.1.3.1 The testing organization shall prepare the operating instruction on the basis of the specific applicable ranges or requirements of the relevant factors laid down in the testing procedure, combined with the specific testing requirements of the workpiece under test.

4.3.1.3.2 Where the testing procedure is re-prepared or revised, the testing organization shall prepare a new operating instruction.

4.3.1.3.3 Where the relevant factors listed in Table 1 and in the relevant clauses and annexes change, even if such variation, with the exception of items 12 to 16 of Table 1, does not exceed the specific applicable range or requirement laid down for those relevant factors in the testing procedure, the testing organization shall likewise prepare a new operating instruction.

4.3.1.3.4 While complying with the provisions of NB/T 47013.1, the content of the operating instruction shall at least include the following: a) testing technique requirements: testing technique, such as straight-probe testing, angle-probe testing, direct contact technique or immersion technique, and the wave mode used; b) test object: category of pressure equipment, name, specification, material and heat treatment condition of the object to be tested, timing of testing, area to be tested and surface temperature of the workpiece; c) testing equipment and accessories: instrument model, probe specification, couplant, type of block, items, timing and performance indexes of the performance checks of instrument and probe; d) technical parameters relating to the testing process: scanning direction and scanning range, method of flaw sizing and assessment requirements.

4.3.1.3.5 The operating instruction shall be subjected to process validation before it is applied for the first time.

4.3.2 Technical requirements for 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 and regulations, rules, product standards and relevant technical documents.

4.3.2.2 Testing technique levels.

4.3.2.2.1 The ultrasonic testing of raw materials and parts used in steel pressure equipment is not divided into technique levels.

4.3.2.2.2 The ultrasonic testing of welded joints of steel pressure equipment is divided into three technique levels, level A, level B and level C. Where, for structural or other reasons, the requirements of a testing technique level cannot be fully satisfied, the testing organization shall adopt effective technical measures, prepare a special operating instruction, and carry out process validation in accordance with 4.3.3.

4.3.2.3 General testing modes for different categories of test object.

4.3.2.3.1 For the testing of raw material tubes, transverse-wave angle-beam testing is generally used; for the testing of other raw materials and parts, longitudinal-wave normal-beam testing is generally used, supplemented where necessary by transverse-wave or longitudinal-wave angle-beam testing.

4.3.2.3.2 For welded joints of pressure equipment, transverse-wave angle-beam testing is generally used; where the testing technique level is level C, longitudinal-wave normal-beam testing shall also be added.

4.3.2.4 Selection of the testing surface, or side.

4.3.2.4.1 The selection of the testing surface, or side, shall take comprehensive account of factors such as the structure of the workpiece under test, its manufacturing process, the possible locations and orientations of flaws, and the practicability of carrying out the testing.

4.3.2.4.2 For the testing of welded joints, the selection of the testing surface shall further take account of the testing technique level adopted.

4.3.2.5 Selection of the couplant and requirements for the surface temperature of the workpiece. The couplant used in the actual testing shall be the same as that used when the testing system was set up and calibrated. Where conventional probes and couplants are used, the surface temperature of the workpiece under test shall be controlled between 0 degrees Celsius and 50 degrees Celsius; where the temperature exceeds 50 degrees Celsius or is lower than 0 degrees Celsius, special probes or couplants may be used, and the difference between the temperature at which the testing system was set up and calibrated and the actual testing temperature shall be kept within 15 degrees Celsius.

4.3.3 Process validation.

4.3.3.1 In the following cases, general-purpose reference blocks or special reference blocks are generally used to carry out process validation: a) testing of raw materials or parts made of carbon steel or low alloy steel; b) testing of welded joints made of carbon steel or low alloy steel, with the exception of the cases specified in 4.3.3.2.

4.3.3.2 In the following cases special reference blocks shall be used, in which case the blocks shall be manufactured in accordance with 4.2.3.2.5.2 c), or simulation blocks shall be used, to carry out process validation, it being understood that for item d) only simulation blocks may be used for process validation. The blocks shall cover the range of the object category concerned in the testing procedure, shall include at least the minimum and the maximum values of the workpiece specification, and the corresponding blocks shall be selected for process validation. The cases are: a) testing of raw materials or parts made of medium alloy steel or high alloy steel; b) testing of welded joints made of ferritic medium alloy steel or of ferritic high alloy steel, and ultrasonic testing of welded joints of pressure equipment made of other fine-grained isotropic and low-acoustic-attenuation metallic materials; c) testing of welded joints of ferritic-austenitic type or of austenitic type steels, testing of dissimilar-steel welded joints, testing of austenitic welded joints and testing of nickel-based alloy welded joints; d) testing of welded joints which, for structural or other reasons, cannot fully satisfy the requirements of the testing technique level; e) where explicitly required by the relevant clauses and annexes of this document; f) where the contract technical requirements or the parties concerned consider it necessary.

4.3.3.3 Where general-purpose reference blocks are used for process validation, the content of the validation shall include verifying that the sensitivity and the sensitivity margin over the sound-path range to be examined and the signal-to-noise ratio satisfy the testing requirements.

4.3.3.4 Where special reference blocks or simulation blocks are used for process validation: a) the content of the validation shall include verifying that the sensitivity over the sound-path range to be examined, the signal-to-noise ratio, the sound-beam coverage and the echoes or the indications of the reference reflectors or of the flaws satisfy the testing requirements; b) it shall be possible to detect all the flaws provided in the block; c) the measured flaw dimensions, such as indicated length and height, shall be not less than the actual flaw dimensions; d) for simulation blocks, it shall be possible to determine the flaw type, volumetric, planar and so on.

4.3.3.5 Process validation carried out with special reference blocks or with simulation blocks may also be replaced by ultrasonic simulation; however, the simulation technique adopted shall have been technically validated and shall have been shown by field tests to satisfy the actual testing requirements, and the relevant supporting documents shall be provided.

4.4 Safety requirements. The testing site, the environment and the safety protection shall comply with the provisions of NB/T 47013.1.

4.5 Implementation of testing.

4.5.1 Preparation for testing.

4.5.1.1 During the manufacture, the installation and the in-service inspection of pressure equipment, the selection of the timing of ultrasonic testing and of the testing proportion shall comply with the provisions of the relevant laws and regulations, standards and relevant technical documents.

4.5.1.2 The testing surface, or side, that is determined shall ensure that the area of the workpiece to be examined can be adequately tested and that 100 percent coverage is obtained.

4.5.1.3 The surface quality of the weld shall be qualified by visual inspection; all paint, rust, spatter and dirt affecting the testing that are present on the testing surface, that is on the area over which the probe passes, shall be removed, and the surface roughness of that area shall comply with the testing requirements; irregularities of the surface shall not affect the validity of the testing result.

4.5.2 Scanning coverage. In order to ensure that during testing the ultrasonic beam is able to scan the entire area of the workpiece to be examined, the overlap of adjacent scans of the probe shall be greater than 10 percent of the diameter or of the width of the probe crystal, and shall comply with the testing coverage provisions of the corresponding clauses and annexes of this document.

4.5.3 Scanning speed. The manual scanning speed shall not exceed 150 mm per second; where ultrasonic imaging techniques are used for testing, or where fully automatic scanning is used, the scanning speed shall be determined by tests on reference blocks.

4.5.4 Adjustment of the evaluation sensitivity, relative to the reference sensitivity: a) coupling compensation: during testing and flaw sizing, compensation shall be made for the coupling loss caused by the different surface roughness of the reference block and of the workpiece under test.

4.5.4 b) attenuation compensation: during testing and flaw sizing, compensation shall be made for the loss of sensitivity and for the error of flaw sizing caused by the different material attenuation of the reference block and of the workpiece under test.

4.5.4 c) curvature compensation: during testing and flaw sizing, for workpieces whose testing surface is curved, compensation shall be made for the difference of coupling loss caused by the different curvature radii of the workpiece and of the reference block.

4.5.5 Scanning sensitivity. The setting of the scanning sensitivity shall comply with the provisions of the corresponding clauses and annexes of this document.

4.5.6 Flaw sizing: a) flaw sizing shall be carried out in accordance with the provisions of the corresponding clauses and annexes of this document; b) when sizing flaws, the influence on the flaw length of the curvature of the testing surface, of the flaw depth and of the sound-beam width shall be taken into account and appropriate corrections shall be made.

4.5.7 Re-checking of the instrument and probe system.

4.5.7.1 The system shall be re-checked in any one of the following circumstances: a) the probe, the couplant or the parameter settings of the instrument have been changed; b) the scanning range or the scanning sensitivity is suspected of having changed; c) work has continued for 4 h; d) the work has been completed.

4.5.7.2 Re-checking of the scanning range. If, at any point on the scanning line, the offset exceeds 10 percent of the reading at that point on the scanning line or 5 percent of the full scanning range, whichever is the greater, the scanning range shall be readjusted and all the areas tested since the previous re-check shall be re-examined.

4.5.7.3 Re-checking of the reference sensitivity, that is re-checking of the evaluation sensitivity. During the re-check, if within the testing range it is found that on the reference sensitivity or on the distance-amplitude curve the echo amplitude of the reference reflector at any depth has fallen by more than 2 dB with respect to the value at calibration, all the areas tested since the previous re-check shall be re-examined; if the echo amplitude has risen by more than or equal to 2 dB with respect to the value at calibration, all the signals recorded since the previous re-check shall be re-evaluated.

5 Ultrasonic testing methods and quality grading for raw materials or parts used in pressure equipment

5.1 Scope. This clause specifies the ultrasonic testing methods and the quality grading for raw materials or parts used in pressure equipment.

5.2 Testing process documents for the ultrasonic testing of raw materials or parts used in pressure equipment. In addition to complying with the provisions of 4.3, the testing process documents for the ultrasonic testing of raw materials or parts shall also include the relevant factors listed in Table 2.

Table 2, relevant factors to be covered by the ultrasonic testing procedure for raw materials or parts, item 1: product type, that is plate, tube, forging and the like.

Table 2, item 2: timing of testing, for instance before or after heat treatment.

Table 2, item 3: testing range.

Table 2, item 4: quality acceptance grade.

5.3 Ultrasonic testing method and quality grading for plates used in pressure equipment.

5.3.1 Scope.

5.3.1.1 This clause applies to the ultrasonic testing of plates for pressure equipment made of carbon steel or low alloy steel with a base material thickness greater than or equal to 6 mm.