Basic knowledge of non-destructive testing, suitable for those who are not familiar with it

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I. Basic Knowledge of Non-Destructive Testing 1.1 Overview of Non-Destructive Testing 1.1.1 Definition and Classification of Non-Destructive Testing What is non-destructive testing? Literally speaking, it refers to methods for inspecting and testing specimens without causing any damage to them. However, this is not the definition of non-destructive testing in a strict sense. The definition of modern non-destructive testing is: a method that uses physical or chemical means, along with advanced technologies and equipment, to examine and test the structure, properties, and condition of the interior and surface of a specimen, without causing damage to it. Three terms have emerged in the development of non-destructive testing technology, namely: Non-destructive Inspection, Non-destructive Testing, and Non-destructive Evaluation. It is generally believed that these three terms represent three stages in the development of non-destructive testing technology. Non-destructive flaw detection is the term for the early stage, and its meaning lies in detecting and identifying defects ； Non-destructive testing is the name used at this stage; its scope goes beyond merely detecting defects to also including the detection of other information related to the test specimen. Non-destructive evaluation, on the other hand, refers to the development stage that is about to be entered or has already been entered. It encompasses a broader and more profound range of aspects; it requires not only the detection of defects and the investigation of the structure, properties, and condition of the test specimen, but also the acquisition of comprehensive, more accurate, and integrated information. Radiographyic Testing (abbreviated as RT), Ultrasonic Testing (abbreviated as UT), Magnetic Testing (abbreviated as MT), and Penetrant Testing (abbreviated as PT) are methods for detecting defects that were developed early on and are widely used. They are known as the four conventional testing methods. To this day, these four methods remain the most commonly used non-destructive testing techniques for quality inspection and reinspection of boilers and pressure vessels. Among them, RT and UT are primarily used to detect internal defects in test specimens. PT is mainly used to detect surface defects in test pieces, while MT is primarily used to detect surface and near-surface defects in test pieces. Other non-destructive testing methods used for boiler and pressure vessels include Eddy current Testing (abbreviated as ET) and Acoustic Emission testing (abbreviated as AE). 1.1.2 Purpose of non-destructive testing Non-destructive testing techniques are generally employed to achieve the following purposes: 1. Ensuring product quality ； 2. Ensure safe use ； 3. Improve manufacturing processes ； 4. Reduce production costs. 1.1.3 Characteristics of NDT applications When applying non-destructive testing, it is necessary to be aware of the following characteristics: 1. Non-destructive testing should be used in conjunction with destructive testing ； 2. Select the appropriate timing for conducting non-destructive testing ； 3. Select the most appropriate non-destructive testing method correctly ； 4. Comprehensive application of various non-destructive testing methods. 1.2 Radiographic Testing (RT) and Its Characteristics 1.2.1 Principle of Radiographic Testing (RT): The principle of radiographic testing relies on the property of rays to penetrate materials. Through the absorption and attenuation effects of materials on radiation, as well as the photographic properties of film, what is achieved is the reproduction of the intensity distribution of the radiation after it passes through the material on the negative. By observing and analyzing the film, the integrity and uniformity of the object under inspection are determined, thereby achieving the purpose of non-destructive testing. 1.2.2 Characteristics of radiographic inspection (limitations and advantages): 1. It enables the acquisition of intuitive images of defects, with accurate qualitative assessment; quantitative measurements of length and width are also fairly precise ； 2. The results can be recorded directly, and the recording medium can be preserved for a long time ； 3. The detection rate for volumetric defects is very high; for area-based defects, improper detection angles can lead to missed detections ； 4. It is suitable for inspecting workpieces with thin thicknesses but not those with thick thicknesses, as inspecting thick workpieces requires high-energy inspection equipment. Radiographic inspection of workpieces larger than 100 mm is generally quite difficult. Therefore, as the plate thickness increases, the absolute sensitivity of radiographic inspection decreases; in other words, when inspecting thick plates using radiography, there is a greater likelihood of missing small-sized defects as well as certain area-based defects. 5. It is suitable for inspecting weld seams, but not suitable for inspecting fillet welds, as well as plates, bars, forgings, etc. 6. It is difficult to determine the position and size (height) of defects in the thickness direction of the workpiece. 7. High detection costs and slow speed. 8. Radiation is harmful to the human body. 1.3 Ultrasonic Testing (UT) and Its Characteristics 1.3.1 Principle of Ultrasonic Testing (UT): Ultrasonic testing makes use of the fact that ultrasonic waves can penetrate materials, and that they reflect, refract, and transmit at interfaces where there are differences in acoustic impedance. Various waveforms are displayed on a fluorescent screen through transducers; by observing and analyzing the waveforms and their positions on the screen, non-destructive testing is achieved. 1.3.2 Characteristics of ultrasonic testing (advantages and limitations): 1. It has a high detection rate for surface defects, but a lower detection rate for volume defects ； 2. It is suitable for inspecting workpieces with greater thickness, such as forgings with diameters of several meters and welds with thicknesses of several hundred millimeters; it is not suitable for inspecting workpieces with thinner thicknesses, as it is difficult to inspect welds with a thickness of less than 8 mm and sheets with a thickness of 6 mm ； 3. Suitable for various test pieces, including butt welds, fillet welds, plates, pipes, bars, forgings, as well as composite materials ； 4. Low inspection costs and fast speed; the inspection instruments are small and lightweight, making them convenient for use on-site ； 5. It is not possible to obtain intuitive images of defects, making qualitative analysis difficult and reducing quantitative accuracy ； 6. There are no direct witness records for the inspection results ； 7. The defects can be located with high accuracy in the thickness direction of the workpiece ； 8. The material and grain size have an impact on flaw detection; for example, cast steel materials and austenitic stainless steel welds are not suitable for ultrasonic flaw detection due to their large grain size. 1.4 Magnetic Particle Testing (MT) and Its Characteristics 1.4.1 Principle of Magnetic Particle Testing (MT): When ferromagnetic components are magnetized, if there are defects on or near their surface that are perpendicular to the direction of the magnetic field or at an angle to it, the magnetic permeability of the material within these defects – which is air or non-metallic inclusions – is much lower than that of the component itself. This results in higher magnetic resistance. As a consequence, the magnetic flux lines bend as they pass through these defects; some of these flux lines follow the law of refraction and emerge on the surface of the component, forming N and S poles and creating a detectable leakage magnetic field. When a magnetic suspension or magnetic particles are applied to the surface of the component, the magnetic particles at the defect sites become magnetized by this leakage magnetic field, also forming N and S poles. They then arrange themselves along the direction of the magnetic flux lines, forming magnetic traces that indicate the location, shape, and size of the defects. 1.4.2 Characteristics of magnetic particle testing (advantages and limitations): 1. It is suitable for testing ferromagnetic materials, but cannot be used for testing non-ferromagnetic materials ； 2. It is suitable for detecting surface and near-surface defects; it cannot be used to examine internal defects. The depth to which defects can be detected depends on the condition of the workpiece, the state of the defects, and the processing conditions, generally ranging from 1–2 mm, with deeper defects reaching 3–5 mm ； 3. It has a very high detection sensitivity, enabling the detection of extremely small cracks and other defects ； 4. The detection cost is very low, and the speed is fast ； 5. The shape and size of the workpiece can sometimes affect detection, as it may be difficult to magnetize and thus cannot be detected. 1.5 Penetrant Testing (PT) and Its Characteristics 1.5.1 Principle of Penetrant Testing (PT): After applying a penetrant containing fluorescent or colored dyes to the surface of the workpiece, under the effect of capillary action, the penetrant penetrates into defects that are open on the surface after a certain period of time. After removing the excess penetrant from the surface of the part, a developer is applied to the surface; again, due to capillary action, the developer attracts the penetrant remaining in the defects. The penetrant then returns to the developer, and under a specific light source (ultraviolet or white light), the traces of penetrant in the defects become visible (as yellow-green fluorescence or bright red), thereby allowing the appearance and distribution of these defects to be detected. 1.5.2 Characteristics of penetrant testing methods (advantages and limitations): 1. Penetrant testing can be used to detect surface open defects in any type of material, except for loose and porous materials; this includes materials such as steel, non-ferrous metals, ceramics, and plastics ； 2. Complex components can also be inspected using penetrant testing, allowing for a nearly comprehensive inspection in just one procedure ； 3. When defects exist in multiple directions at the same time, all inspections can be completed with a single testing operation; even defects with complex shapes leave visible traces that are easy to observe ； 4. No large equipment is required; it’s a portable spray can for coloring inspection, needing neither water nor electricity, making it very convenient for use on-site ； 5. The surface finish of the test specimen has a significant impact, and the test results are often influenced by the skill level of the operator ； 6. It can detect surface-opening defects, but it cannot detect buried defects or closed-type surface defects ； 7. The detection sensitivity is lower than that of magnetic particle testing ； 8. The materials are expensive, resulting in high costs ； 9. Many detection procedures, slow speed ； 10. Some materials are flammable and toxic. 1.6 Introduction to Other Non-Destructive Testing Methods 1.6.1 Eddy Current Testing (ET): This is a non-destructive testing method based on the principle of electromagnetic induction; conductive materials generate eddy currents when exposed to an alternating magnetic field. Eddy current testing can be applied to any conductive material, by examining the magnitude of these eddy currents as well as certain physical properties of the material. 1.6.2 Acoustic Emission Testing (AE): Acoustic emission technology is a dynamic non-destructive testing method. The phenomenon in which a material or structure deforms or fractures under external or internal forces, resulting in the release of strain energy in the form of elastic waves, is known as acoustic emission; it is also referred to as stress wave emission. Acoustic emission testing is a new non-destructive testing method that determines the degree of structural damage inside a container by detecting the stress waves generated within the material when it is under stress. II. Provisions on non-destructive testing in the \"Regulations on Pressure Vessels\", GB150, and GB151 1.1 Provisions on non-destructive testing in the \"Regulations on Safety Supervision of Pressure Vessels\" (1999) 2.1.1 Provisions on non-destructive testing in the material section Article 14 Carbon steel and low-alloy steel plates used for manufacturing pressure vessel shells shall be subjected to ultrasonic testing one by one if they meet either of the following conditions: 1. Pressure vessels that contain media with an extremely high level of toxicity and pose a high risk. 2. Pressure vessels whose filling medium is liquefied petroleum gas and which have a hydrogen sulfide content of more than 100 mg/l. 3. Pressure vessels with a maximum operating pressure of 10 Mpa or higher. 4. Chapter 4 and Appendix C of GB150, GB151 \"Shell and Tube Heat Exchangers\", GB12337 \"Steel Spherical Storage Tanks\", and other **national standards and industry standards stipulate that ultrasonic testing shall be carried out on each individual piece. 5. Mobile pressure vessels: The ultrasonic testing of steel plates shall be carried out in accordance with the provisions of JB4730-94 \"Non-destructive Testing of Pressure Vessels\". The grade of the steel plates used for the containers referred to in paragraphs 1, 2, and 5 of this article shall be no lower than Grade II ； The grade of steel plates used for the containers referred to in paragraph 3 of this article shall be no lower than Grade III; for the containers referred to in paragraph 4 of this article, the grade of such steel plates shall comply with the provisions of GB150, GB151, or GB12337. Article 20 Titanium materials (referring to titanium alloys and industrially pure titanium. Non-destructive testing of (and their composite materials): 1. Ultrasonic testing should be performed on the molded titanium-steel composite plate heads. 2. The following welds in titanium material pressure vessels shall be subject to penetrant testing: (1) the fillet welds connecting the nozzles, flanges, reinforcement rings to the vessel shell or head ； (2) Welds connecting the heat exchanger tube sheet to the tubes ； (3) The lap welds of the cladding welds on the titanium-steel composite plate, as well as the lap welds between the trim plates and the cladding of the composite plate. Article 21 Non-destructive testing of nickel materials (referring to nickel and nickel-based alloys as well as their composite materials): 1. Ultrasonic testing shall be conducted on the formed nickel-steel composite plate heads. 2. The following welds in nickel material pressure heaters shall be subjected to magnetic particle or penetrant testing ； (1) Fillet welds connecting the Takeover, flange, reinforcement ring to the shell or head ； (2) Welds connecting the heat exchanger tube sheet to the tubes ； (3) Laminated weld joint of nickel-steel composite plate. Article 25 Requirements for Non-Destructive Testing of Re-inspected Primary Pressure Components 1. Steel plates used in the manufacture of Class III pressure vessels must be re-inspected. When the steel plant does not provide a certificate of ultrasonic testing for the steel plates, re-ultrasonic testing shall be carried out in accordance with the requirements of Article 14 of these regulations. 2.1.2 Requirements for non-destructive testing in design – Article 30: Non-destructive testing shall be specified on the general design drawing of pressure vessels. Article 43 For pressure vessels manufactured by welding, the welding joint coefficient shall be selected according to Table 3-5. When designed in accordance with the JB4732 standard, the welding joint coefficient is set at 1.0. file:///C:\Users\005066\AppData\Local\Temp\ksohtml6716\wps1.png Table 3-5 Welding joint coefficients for pressure vessels Note: 1. The non-destructive testing referred to in this table involves X-ray or ultrasonic testing for steel pressure vessels, while for non-ferrous metal pressure vessels, X-ray testing is generally used. 2. The upper limit values for the welding joint coefficients of pressure vessels made of non-ferrous metals listed in the table refer to gas metal arc welding, while the lower limit values refer to shielded metal arc welding. 3. A butt weld that is equivalent to full penetration welding on both sides refers to a weld in which welding is performed on one side but the shape of the weld is achieved on both sides; it is evaluated as if it were a double-sided weld (including evaluation of the welding test piece), such as welds with TIG welding for root pass or welds using ceramic or steel liners. Article 47: For pressure vessels that do not meet the conditions specified in Article 46 and for which inspection holes cannot be created due to special circumstances, 100% non-destructive testing (using X-rays or ultrasound) shall be conducted on each longitudinal and circumferential weld. 2.1.3 Requirements for non-destructive testing in manufacturing – Article 69: The weld marks remaining after the removal of the shims used for temporary lifting lugs during the welding of pressure vessels must be polished smooth, and penetrant testing or magnetic particle testing must be carried out in accordance with the specifications in the drawings to ensure that there are no defects such as cracks on the surface. Article 71: In the event that repair is required after a pressure test, the repaired area must pass non-destructive testing in accordance with the original requirements. Article 76, 4) Requirements for weld undercutting: (1) For pressure vessels manufactured from steel with a minimum specified tensile strength of 540 MPa or higher, as well as chromium-molybdenum low-alloy steel; pressure vessels made of austenitic stainless steel, titanium, or nickel; low-temperature pressure vessels; spherical pressure vessels; and pressure vessels for which the weld coefficient is set at 1.0, there shall be no undercutting on the surface of the welds. (2) For the weld surfaces of pressure vessels other than those mentioned in item (1) above, the depth of undercutting shall not exceed 0.5 mm, the continuous length of undercutting shall not exceed 100 mm, and the total length of undercutting on both sides of the weld shall not exceed 10% of the length of that weld. 2.1.4 Requirements for the non-destructive testing section – Article 81: Non-destructive testing personnel must pass the examinations specified in the \"Regulations on the Qualification Assessment for Non-Destructive Testing Personnel of Boilers and Pressure Vessels\" in order to obtain a qualification certificate; only then can they undertake non-destructive testing tasks corresponding to the type and technical level of their qualification certificate. Article 82: For the welded joints of pressure vessels, inspections for shape, dimensions, and visual quality must be carried out first; only after passing these checks can non-destructive testing be performed. Materials prone to delayed cracking should undergo non-destructive testing 24 hours after welding is completed ； Materials prone to reheat cracking should undergo additional non-destructive testing after heat treatment. Article 83: The non-destructive testing methods for pressure vessels include radiographic testing, ultrasonic testing, magnetic particle testing, penetrant testing, and eddy current testing. Pressure vessel manufacturers shall select the testing methods and testing lengths in accordance with the specifications in the drawings and relevant standards. Article 84: The proportion of non-destructive testing for welded joints in pressure vessels is generally divided into two types: full (100%) and partial (20% or more). For ferritic steel cryogenic vessels, the proportion of localized non-destructive testing shall be greater than or equal to 50%. Article 85: In cases meeting one of the following conditions, all butt joints of pressure vessels must undergo either radiographic or ultrasonic testing. 1. Pressure vessels that are required to undergo full radiographic or ultrasonic testing as specified in standards such as GB150 and GB151. 2. Third-class pressure vessels. 3. Reaction pressure vessels and storage pressure vessels for flammable media in Category II pressure vessels. 4. Pressure vessels with a design pressure greater than 5.0 Mpa. 5. Shell-and-tube waste heat boilers with a design pressure of 6.0 Mpa or higher. 6. Pressure vessels for which a weld coefficient of 1.0 is adopted in the design (except for seamless tube shells). 7. Pressure vessels designed through fatigue analysis. 8. Pressure vessels using electroslag welding. 9. Pressure vessels that cannot be subjected to internal or external inspections or pressure tests after use. 10. Pressure vessels made of aluminum, copper, nickel, titanium, or their alloys that meet one of the following conditions: (1) The medium is flammable or has an extremely high, high, or moderate level of toxicity ； (2) Those using pneumatic testing ； (3) Those with a design pressure of 1.6 Mpa or higher ； Article 86 The selection requirements for inspection methods of welded joints in pressure vessels are as follows: 1. When the wall thickness of a pressure vessel is 38 mm or less, radiographic testing shall be employed for its butt joints; if radiographic testing cannot be used due to structural reasons or other factors, recorded ultrasonic testing is permitted. 2. When the wall thickness of the pressure vessel is greater than 38 mm (or less than or equal to 38 mm but greater than 20 mm, and the lower limit of the specified tensile strength of the material is greater than or equal to 540 MPa), if radiographic testing is used for the butt joints, local ultrasonic testing shall be carried out in addition for each weld; if ultrasonic testing is used, local radiographic testing shall be carried out in addition for each weld. When neither radiographic testing nor ultrasonic testing is possible, other testing methods shall be employed for additional local non-destructive testing. The additional local testing shall cover all weld intersections, and the proportion of such additional testing shall be 20% of the proportion of original non-destructive testing specified in Article 84 of these regulations. 3. For fillet joints and T-joints that require non-destructive testing, and for which radiographic or ultrasonic testing is not possible, 100% surface inspection shall be carried out. 4. For surface inspection of ferromagnetic material pressure vessels, magnetic particle testing should be given priority. 5. Radiographic testing should be preferably used for the butt joints of pressure vessels made of non-ferrous metals. Article 87: For other pressure vessels other than those specified in Article 85 of these regulations, their butt joints shall undergo partial non-destructive testing and must comply with the requirements of Articles 84 and 86. The areas to be subject to partial non-destructive testing shall be designated by the inspection department of the manufacturing unit based on actual conditions; however, all weld intersections as well as those weld sections covered by other components in the opening areas must be inspected using radiographic testing. Butt joints of welded patches (excluding those where the patch is formed first and then welded) and welded pipe sheets must undergo 100% non-destructive testing (the method of testing shall be determined in accordance with Article 86). Butt joints of welded reinforcement rings must undergo 100% ultrasonic or radiographic testing, and the acceptance standard for these shall be the same as that applicable to the corresponding butt joints of the pressure vessel shell. The welded head shall undergo non-destructive testing after forming; if non-destructive testing is carried out before forming, it shall be performed again in the arc transition area after forming. For the welding joints of the upper and lower connection rings and jackets on glass-lined equipment, as well as those of the nozzles of glass-lined equipment with a nominal diameter of less than 250 mm, non-destructive testing is not required; however, a welding procedure qualification must be carried out in accordance with JB4708, and a practical welding procedure specification must be prepared. This specification must be approved by the technical director or chief engineer of the manufacturing unit before it can be implemented. Penetrant testing shall be conducted on the welding joints that connect the upper and lower connection rings to the cylinder. For welded joints that have been subjected to local radiographic testing or ultrasonic testing, if any defects exceeding the specified limits are found in the areas that were tested, additional local testing covering at least 10% of the length of that welded joint is required. If those tests still do not yield satisfactory results, then the entire welded joint must be tested. Article 88 stipulates that the non-destructive testing of pressure vessels shall be carried out in accordance with JB4730 \"Non-Destructive Testing of Pressure Vessels\". Full (100%) or partial (20%) non-destructive testing of the butt joints of pressure vessels is required; when radiographic testing is used, the quality of the inspections must be at least grade AB, with a satisfactory result level of grade III, and no underpenetration is allowed. When ultrasonic testing is used, the satisfactory result level is grade II. For pressure vessels that are required to undergo 100% non-destructive testing as specified in standards such as GB150 and GB151, Class III pressure vessels, pressure vessels for which a welding factor of 1.0 is applicable, and pressure vessels for which internal and external inspections or pressure tests cannot be carried out, 100% non-destructive testing must be conducted on their butt joints: when radiographic testing is used, the quality of the inspection shall not be lower than grade AB, and the acceptable grade is II. When ultrasonic testing is used, the acceptable grade is Grade I. The proportion of non-destructive testing and the acceptance criteria for the butt joints of pressure vessel nozzles with a nominal diameter of 250 mm or more (or with a nominal diameter of less than 250 mm but a wall thickness of more than 28 mm) shall be the same as those required for the welds of the pressure vessel shell itself ； For those with a nominal diameter of less than 250 mm and a wall thickness of 28 mm or less, only surface non-destructive testing is performed, and the acceptable quality level is Grade I as specified in JB4730. The non-destructive testing level for the welded joints of pressure vessels made of non-ferrous metals, as well as the quality requirements for radiographic inspection, are specified according to relevant standards or in the design drawings. Article 89: When full or partial non-destructive testing is carried out on the butt joints of pressure vessels, both radiographic and ultrasonic methods shall be used, and both must yield satisfactory results. The quality requirements and acceptance criteria shall be in accordance with the respective standards. Article 90 For pressure vessels subjected to partial non-destructive testing, the manufacturer shall also be responsible for the quality of the areas that have not been tested. Article 90 The requirements for non-destructive testing of the surface of pressure vessels are as follows: 1. For the grooved surfaces, butt joints, corner joints, and T-joints of steel pressure vessels that meet the conditions specified in Paragraph 2 of Article 69 of these regulations, and for which the minimum specified tensile strength of the material is 540 Mpa or higher, magnetic particle testing or penetrant testing shall be carried out in accordance with the relevant provisions of standards such as GB150, GB151, and GB12337. The inspection results must show no cracks, pores, or delamination, and must meet the Grade I requirements specified in JB4730 for defect indications detected by magnetic particle or radiographic testing. 2. Pressure vessels made of non-ferrous metals shall be manufactured in accordance with the corresponding standards or design drawings. Article 92: For pressure vessels assembled and welded on-site, surface non-destructive testing of the weld joints made on-site shall be carried out in accordance with standard requirements prior to the pressure test. After the pressure test, partial surface non-destructive testing shall be conducted in accordance with relevant standard provisions. If defects such as cracks are detected that exceed the specified limits, supplementary testing shall be carried out as per the standards; if the vessel still does not meet the requirements, then full surface non-destructive testing of that weld joint shall be performed. Article 93: The manufacturing unit must maintain accurate original records of non-destructive testing. The diagrams showing the locations to be inspected must clearly and precisely indicate the actual inspection positions (such as the location, numbering, and direction of radiographic inspections). Reports must be issued correctly, and non-destructive testing archives and negatives (including those of existing defects) or ultrasonic testing records must be kept properly. The retention period for these documents shall be no less than seven years; after that period, they may be handed over to the user if requested. 2.2 Provisions on non-destructive testing in GB150—1998 \"Steel Pressure Vessels\": 2.2.1 Provisions on non-destructive testing in the General Principles (3.7) Weld joint factor: The weld joint factor is determined based on the type of weld joint in the pressure-bearing component and the proportion of length subject to non-destructive testing. Double-sided welded joints and fully penetrative butt joints equivalent to double-sided welding: 100% non-destructive testing, ф=1.00; partial non-destructive testing, ф=0.85. Single-sided welded butt joints (with gussets in close contact with the base metal along the entire length of the weld root): 100% non-destructive testing, ф=0.9; partial non-destructive testing, ф=0.82. 2.3 Requirements for non-destructive testing in materials (4.2.9): The following carbon steel and low-alloy steel plates used for shells shall be subjected to ultrasonic testing on a piece-by-piece basis; the methods and quality standards for ultrasonic testing of steel plates are specified in JB4730. a) 20R and 16MnR with a thickness greater than 30 mm, of a quality grade not lower than Grade III. b) 15MnNbR, 18MnMoNbR, 13MnNiMoNbR, and Cr-Mo steel plates with a thickness greater than 25 mm, of a quality grade not lower than Grade III. c) For 16MnDR, 15MnNiDR, and 09MnNiDR with a thickness of less than 20 mm, the quality grade shall be no lower than Grade III. d) The quality grade of the inner cylinder steel plates for multi-layer wrapped pressure vessels shall not be lower than Grade II. e) Steel plates supplied in quenched and tempered condition shall have a quality grade of not lower than Grade II. (4.2.12) Stainless steel composite steel plates shall comply with the following requirements: b) The bonding ratio criteria for the stainless steel as well as the range of ultrasonic testing shall be specified in the drawings or corresponding technical documents. 2.2.3 Requirements for flanges regarding non-destructive testing: (9.1.4) When manufacturing necked flanges from steel plates when necessary, a) the steel plates shall be subjected to ultrasonic testing to ensure there are no delamination defects ； b) Ring butt joints shall undergo post-heat treatment and 100% radiographic or ultrasonic inspection, with the acceptance criteria specified in JB4700. 2.2.4 Provisions for manufacturing, inspection, and acceptance regarding non-destructive testing: (10.1.5) The non-destructive testing of containers shall be carried out by personnel holding a \"Qualification Certificate for Non-Destructive Testing of Boilers and Pressure Vessels\" for the relevant methods. (10.2.2) Groove surface requirements: b) For steel materials with a minimum standard tensile strength of ab > 540 Mpa, as well as Cr-Mo low-alloy steel, the groove surfaces resulting from flame cutting must be subjected to magnetic particle or penetrant testing. When such testing is not possible, the cutting process must ensure the quality of the grooves. (10.2.6) Bolts, studs, and nuts (10.2.6.3) c) Studs and nuts with a nominal diameter greater than M48 shall be subjected to magnetic particle testing; no cracks are allowed. (10.6.3.4) Laminated plate wrapping: For laminated plates with a minimum standard tensile strength of ab > 540 Mpa, Class C joints shall be subjected to magnetic particle or penetrant testing after grinding; no cracks, undercutting, or dense pores are allowed. 2.2.5 Provisions for non-destructive testing (10.8.1) The welded joints of containers shall undergo non-destructive testing in accordance with these regulations after passing inspections for shape, dimensions, and appearance. (10.8.2) Detection range of radiography and ultrasonic testing (10.8.2.1) Containers and pressure components that meet one of the following conditions must have their Class A and Class B weld joints subjected to 100% radiography and ultrasonic testing using the methods specified in the drawings: a) Carbon steel and 16MnR with a plate thickness δs > 30 mm ； b) 15MnV, 20MnMo, and austenitic stainless steels with a steel plate thickness δs > 25 mm ； c) Steel with a minimum standard tensile strength value of σb > 540 Mpa (except for 15MnVR with σ6-8 mm). d) 12CrMo, 15CrMoR, and 15CrMo with a steel plate thickness of δs > 16 mm ； Other Cr-Mo low-alloy steels of any thickness. e) Containers subjected to pressure testing ； f) The diagram indicates containers designed to hold substances with extremely hazardous or highly hazardous toxicity ； g) Containers specified in the drawing to be inspected 100% ； h) Class A welded joints for the inner cylinder of multi-layer wrapped pressure vessels ； i) Class A welded joints of each single-layer cylinder in the heat-shielded pressure vessel ； j) For the welded joints that have undergone 100% radiographic or ultrasonic testing as mentioned above, whether further ultrasonic or radiographic testing is required for reinspection, and the length to be inspected for such reinspection, shall be specified by the designer in the drawings ； (10.8.2.2) For containers other than those specified in 10.8.2.1 and 10.8.2.3, partial radiographic or ultrasonic testing of their Class A and Class B weld joints is permitted. The testing method shall be as specified in the drawings; the testing length shall be not less than 20% of the length of each weld joint and not less than 250 mm. All areas at the intersections of welds and areas below them shall be tested, and such areas can be included in the partial testing length. a) First, assemble the plates and then test all the joints on the convex heads ； b) Welded joints that are covered by reinforcing rings, supports, gaskets, internal components, etc ； c) Weld joints contained within a circle with the opening diameter as its center and 1.5 times the opening diameter as its radius ； d) Welded joint of embedded spigot connected to cylinder or head ； e) Welded joints of nozzles with a nominal diameter of not less than 250 mm connected to long-neck flanges, and nozzles connected to each other. (Note: According to this provision, even after testing, the manufacturing department remains responsible for the quality that has not been inspected. However, if further testing reveals defects such as pores that do not pose a threat to the safety of the container, and such inspections are also not permitted, then 100% radiographic or ultrasonic testing should be carried out.) (10.8.2.3) For the final circumferential sealing weld of cylinders and heads with a diameter not exceeding 800 mm, when a single-sided butt weld without gaskets is used and radiographic or ultrasonic testing is not possible, testing may be omitted; however, gas shielded welding must be used for the root pass. (10.8.2.4) For Class B weld joints between pipes with a nominal diameter of less than 250 mm and long-neck flanges, or between pipes themselves, radiographic or ultrasonic testing may be omitted. (10.8.3) Welded joints that meet one of the following conditions shall have their surfaces subjected to magnetic particle or penetrant testing in accordance with the methods specified in the drawings. a) Class C and Class D welded joints on containers as specified in items c) and d) of 10.8.2.1 ； b) Class C welded joints of the laminates in multi-layer wrapped pressure vessels, where the minimum standard tensile strength value of the laminate material σb is greater than 540 Mpa ； c) Clad surface ； d) Welded joint of the composite layer in the composite steel plate ； e) Surfaces of the grooved areas on steel materials and Cr-Mo low-alloy steel materials with a minimum standard tensile strength of σb > 540 Mpa that have been treated with flame, as well as the surfaces of areas where defects in such containers have been repaired or welded, and the weld seams from areas where clamps and tie rods have been removed ； f) Welded joints of nozzles and long-neck flanges, as well as nozzles connected to each other, on containers specified in 10.8.2.1, where the nominal diameter is less than 250 mm. (10.8.4) The non-destructive testing standards require radiographic, ultrasonic, magnetic particle, and penetrant testing of welded joints in accordance with JB4730; the acceptance criteria are as follows: (10.8.4.1) Radiographic testing: a) If the containers and pressure components meet the requirements of 10.8.2.1, a grade of not lower than II is considered acceptable ； b) If the container meets the requirements of 10.8.2.2, a rating of not lower than Class III is considered satisfactory ； (10.8.4.2) Ultrasonic testing: a) If the container and pressure-bearing components meet the requirements of 10.8.2.1, grade I is considered acceptable ； b) If the container meets the requirements of 10.8.2.2, a grade of not lower than II is considered satisfactory ； (10.8.4.3) Magnetic particle and penetrant testing: Grade I is considered acceptable ； (10.8.5) Re-inspection (10.8.5.1) For welded joints that have been inspected using X-rays or ultrasound, if any unacceptable defects are found, re-welding should be carried out after those defects are completely removed, and that area should be inspected again using the original inspection method until it meets the requirements. For welded joints that are subject to local inspection, if any unacceptable defects are found, the inspection length shall be increased at both ends of such defects by 10% of the length of that weld seam, with this increased length being no less than 250 mm. If unacceptable defects still exist, then 100% inspection of that welded joint shall be carried out. (10.8.5.2) When unacceptable defects are detected by magnetic particle or penetrant testing, grinding and necessary welding repairs shall be carried out, and the area in question shall be rechecked using the original testing method until it meets the requirements. 2.3 Provisions on non-destructive testing in GB151-1999 \"Shell and Tube Heat Exchangers\" 2.3.1 General provisions on non-destructive testing (3.1) The design, manufacture, inspection, and acceptance of heat exchangers must not only comply with the provisions of this standard but also adhere to the relevant regulations, rules, and guidelines issued by GB150 and **. 2.3.2 Requirements for steel plates in non-destructive testing (4.3.2.2) When long-neck flanges are manufactured from steel plates, a) the plates shall be free from delamination defects, and shall undergo ultrasonic testing in accordance with JB4730, with a quality grade of not lower than Grade III ； b) Ring butt joints shall undergo post-weld heat treatment as well as 100% radiographic or ultrasonic inspection; they must meet the requirements of Grade II for radiographic inspection and Grade I for ultrasonic inspection as specified in JB4730. 2.3.3 Requirements for non-destructive testing of heat exchange tubes (6.3.3) When joining heat exchange tubes, f) the butt joints shall be subjected to radiographic testing; the number of samples inspected shall be no less than 10% of the total number of joints, and at least one sample per joint, with grade III according to JB4730 considered acceptable ； If one item is found to be non-compliant, random inspections should be doubled ； If non-conformities occur again, a 100% inspection should be carried out. 2.3.4 Requirements for non-destructive testing of tube sheets (6.4.1) The butt joints of welded tube sheets shall be subject to 100% radiographic or ultrasonic testing; according to JB4730, the radiographic testing shall meet grade II or above, or the ultrasonic testing shall meet grade I. (6.4.3) For cladded composite tube sheets b), the surface of the base material to be clad and the surface of the cladding material after processing (but before drilling) shall be subject to surface inspection in accordance with JB4730; the inspection results must show no cracks or pores, and the defect levels shall be at grade II. 2.3.5 Requirements for non-destructive testing: The inspection and evaluation criteria for non-destructive testing of welded joints shall be implemented in accordance with the provisions of 10.8 in GB150-1999 and the requirements specified in the drawings, taking into account the different design conditions of the heat exchanger tubes and shell. 2.3.6 The provisions on non-destructive testing in Appendix A of GB151, \"Low-temperature shell and tube heat exchangers\" (≤20°C) (A2.1.3): When the thickness of the steel plates forming the heat exchanger shell is greater than 20 mm, ultrasonic testing shall be carried out on each plate individually, and compliance with Grade III as specified in JB4730 is considered acceptable. (A4.8) Welded joint inspection (A4.8.1) For butted joints of heat exchangers (Types A and B), 100% radiographic or ultrasonic testing shall be carried out if either of the following conditions is met: a) The design temperature of the heat exchanger is below –40°C ； b) Although the design temperature of the heat exchanger is greater than or equal to –40°C, the thickness of the joints is greater than 25 mm ； c) Those that meet the requirements of 10.8.2.1 and 10.8.2.2 in GB150-1998 ； (A4.8.2) Except as specified in A4.8.1, local non-destructive testing is permitted; the inspection length shall be not less than 50% of the length of each welded joint, and not less than 250 mm. (A4.8.3) For heat exchangers that are subject to 100% radiographic or ultrasonic testing in accordance with the requirements of A4.8.1, all welded joints of the pressure-bearing components must undergo 100% magnetic particle or penetrant testing; welded joints connecting pressure-bearing components with non-pressure-bearing components shall also be inspected in accordance with the requirements of this clause. 2.3.7 For the austenitic stainless steel welded steel pipes specified in Appendix C of GB151, “Heat Exchanger Tubes” (C1.8), eddy current testing shall be carried out on each pipe in accordance with GB71277. 2.3.8 Appendix D of GB151, “Design Data for Non-ferrous Metals” (D1): Weld joint coefficients. The weld joint coefficients ф for aluminum, steel, titanium, and their alloys shall be selected from Table D1 according to the type of welded joint in the pressure-bearing components and the length proportion table for radiographic inspection. Table D1: Joint types – Full non-destructive testing; Partial non-destructive testing. Aluminum, Copper, Titanium, Aluminum-Copper-Titanium. Double-sided welding or fully penetrative butt joints equivalent to double-sided welding: Gas tungsten arc welding – 0.90, 0.85, 0.90, 0.85, 0.85, 0.85. Metal inert gas welding – 0.85, 0.85, 0.80, 0.80. Single-sided welded butt joints with non-ferrous metal gaskets: Gas tungsten arc welding – 0.85, 0.85, 0.85, 0.80, 0.80, 0.80. Metal inert gas welding – 0.80, 0.85, 0.70, 0.70. Note: 1. The non-destructive testing referred to in this table is radiographic inspection. 2. For single-sided butt joints with metal gaskets where non-destructive testing is not possible, ф = 0.65 shall be used. III. Introduction to JB/T4730-2005, “Non-destructive Testing of Pressure Equipment”. 3.1 Subject matter and scope of application of JB/T4730-2005: This standard specifies five non-destructive testing methods—radiographic inspection, ultrasonic testing, magnetic particle testing, penetrant testing, and eddy current testing—as well as criteria for assessing defect levels. The various non-destructive testing methods specified in this standard are applicable to the non-destructive testing of pressure-bearing equipment made of metallic materials that are under fabrication or in service. 3.2 Range of radiographic inspection (objects) 3.2.1 Radiographic inspection is applicable to the radiographic testing of welds in pressure vessels and butt joints of steel pipes made of carbon steel, low-alloy steel, stainless steel, copper and copper alloys, aluminum and aluminum alloys, titanium and titanium alloys, and nickel and nickel alloys. Radiographic testing is not suitable for inspecting forgings, pipes, and bars. Radiographic testing is generally not used either for the inspection of T-joints, fillet welds, and surfacing layers. 3.2.2 Radiographic testing of welds in steel pressure vessels is applicable to the X-ray and gamma-ray radiography and quality grading of butt welds in pressure vessels made of carbon steel, low-alloy steel, stainless steel, nickel and nickel alloys with plate thicknesses of 2–400 mm, as well as those made of copper and copper alloys with plate thicknesses of 2–80 mm. 3.2.3 Radiographic testing of circumferential welds in steel pipes is applicable to the radiographic inspection and quality grading of circumferential welds in carbon steel, low-alloy steel, stainless steel, copper and copper alloys, as well as nickel and nickel alloys, when the wall thickness is 2 mm or greater. Welded tees, crosses, pipe caps, reducers, and elbows can be used; the longitudinal and spiral seams of welded pipes can also be referenced, but they are not suitable for welding pipe rings using mechanical welding methods such as friction welding or flash welding. 3.2.4 Radiographic inspection of welds in aluminum pressure vessels is applicable to the X-ray and gamma-ray inspection as well as defect grading of butt welds in aluminum and aluminum alloy pressure vessels with wall thicknesses of less than 2–80 mm. 3.2.5 Radiographic inspection of welds in titanium pressure vessels is applicable to the X-ray and gamma-ray inspection and quality grading of butt welds in titanium and titanium alloy pressure vessels with wall thicknesses of less than 2–50 mm. 3.3 Ultrasound inspection range (objects) 3.3.1 Ultrasound inspection is applicable to the inspection of raw materials, components, and welds of pressure vessels. 3.3.2 Ultrasonic testing of pressure vessel steel plates is applicable to the ultrasonic testing and defect grading of steel plates made of carbon steel or low-alloy steel used in pressure vessels with plate thicknesses ranging from 6 to 250 mm. Ultrasonic testing of austenitic steel plates, nickel and nickel alloy plates, as well as double-direction stainless steel plates can be carried out with reference to these guidelines. 3.3.3 Ultrasonic testing of pressure vessel forgings is applicable to the ultrasonic testing and defect grading of carbon steel and low-alloy steel forgings. (The grades of pressure vessel forgings are divided into four levels: I, II, III, and IV.) Forges of grades I and II do not require ultrasonic testing, while forgings of grades III and IV must undergo ultrasonic testing on a piece-by-piece basis. The qualified levels are as specified in the table below. Ultrasonic testing acceptance levels for forging classification: Reduction in the base wave amplitude per defect; defects in dense areas. For cylindrical forgings, the levels are II, I, II; for flanges at the ends of cylindrical components, the levels are III, III, II. For ring-shaped forgings, the levels are II, II, III. For shaped forgings with a nominal thickness of ≤200 mm, the levels are III, III, III; for those with a nominal thickness greater than 200 mm, the levels are IV, IV, IV. For bowl-shaped forgings, the level is III, III, II. For long-neck flange forgings, the level is III, III, II. For strip-shaped forgings, the levels are III, II, III. Note: Upon the requirement of the customer, the acceptance level for critical areas of the forgings can be increased. However, it is not suitable for ultrasonic testing of coarse-grained materials such as austenitic steel, nor for the detection of circumferential shear waves in ring and cylindrical forgings with an inner-to-outer radius ratio of less than 80%. 3.3.4 Ultrasonic testing of composite plates for pressure vessels is applicable to the ultrasonic testing and defect grading of composite plates made of stainless steel, copper and copper alloys, aluminum and aluminum alloys, titanium and titanium alloys, nickel and nickel alloys used in pressure vessels, when the thickness of the base material is 6 mm or more. 3.3.5 Ultrasonic testing of high-pressure seamless steel pipes is applicable to the ultrasonic testing and defect grading of carbon steel and low-alloy steel seamless pipes used in pressure vessels, with an outer diameter of 12–660 mm and a wall thickness of 2 mm or more, or of stainless steel pipes with an outer diameter of 12–400 mm and a wall thickness of 2–35 mm. It is not suitable for ultrasonic testing of layered defects, nor for the detection of circumferential shear waves in steel pipes with an inner-to-outer diameter ratio of less than 80%. 3.3.6 Ultrasonic testing of high-pressure bolt components is applicable to the ultrasonic testing and defect grading of carbon steel and low-alloy steel bolt blanks with a diameter greater than M36. 3.3.7 is not applicable to ultrasonic testing of austenitic steel bolt blanks. 3.3.8 Ultrasonic testing of welds in steel pressure vessels is applicable to the ultrasonic inspection and defect grading of fully penetrated fusion welded butt welds with a base metal thickness of 8–400 mm. It is not applicable to the butt welds of steel pipes with an outer diameter of less than 158 mm, nor to the fillet welds at pipe supports with an inner diameter of 200 mm or less. It is also not suitable for the inspection of longitudinal welds with an outer diameter of less than 250 mm or a ratio of inner diameter to outer diameter of less than 80%. 3.3.9 Suitable for ultrasonic testing and quality grading of defects resulting from a lack of bonding between the surfacing layer and the base material, as well as reheat cracks in the base material beneath the surfacing layer, in surfacing layers made of stainless steel, nickel alloys, etc. 3.3.10 Ultrasonic testing of welds in aluminum pressure vessels is suitable for the ultrasonic inspection of butt welds in aluminum and aluminum alloy pressure vessels with a thickness of 8 mm or more, as well as for the assessment of defect grades. It is not applicable to butt welds of aluminum and aluminum alloys with an outer diameter of less than 158 mm, nor to fillet welds of pipe fittings with an inner diameter of 200 mm or less. It is also not suitable for the inspection of longitudinal welds with an outer diameter of less than 250 mm or an inner diameter-to-outer diameter ratio of less than 80%. 3.4 Magnetic particle inspection scope (objects): Penetrant testing for pressure vessels is suitable for detecting surface opening defects in pressure vessels and their components made of metal materials, as well as for assessing the severity of those defects. 3.5 Penetrant testing scope (objects) Penetrant testing of pressure vessels is suitable for detecting surface and near-surface defects in pressure vessels made of metal materials, as well as for assessing the severity of these defects.