NB/T Translated English of Chinese Standard: NB/T

Transcription

1 Translated English of Chinese Standard: NB/T NB ENERGY INDUSTRY STANDARD OF THE PEOPLE S REPUBLIC OF CHINA ICS H 26 NB/T Replacing JB/T Nondestructive testing of pressure equipment - Part 2: Radiographic testing 承压设备无损检测第 2 部分 : 射线检测 Issued on: April 2, 2015 Implemented on: September 1, 2015 Issued by: National Energy Administration Page 1 of 91

2 Table of Contents Foreword Scope Normative references Terms and definitions General requirements Inspection process and its selection Evaluation of radiographic testing results and quality grading for melting welding joints of pressure equipment Radiographic testing result evaluation and quality grading for melting welding joints of pressure equipment s pipes and pressure pipelines made of steel, nickel and copper Inspection records and reports Annex A (Informative) Radiography requirements for tube-fillet welds Annex B (Normative) Industrial radiographic film system s characteristic indexes Annex C (Informative) Regular inspection methods of the nigrometer (optical densimeter) Annex D (Informative) Determination of darkroom s safety irradiation time Annex E (Informative) Diagram of typical penetrating methods Annex F (Informative) Determination methods of penetrating times for circular butt welds Annex G (Normative) Calculation methods of focal size Annex H (Normative) Calculation methods of geometric sharpness (Ug) Page 2 of 91

3 Annex I (Informative) Light filters Annex J (Normative) Placement principle of positioning marks Annex K (Informative) Measuring methods for ionic concentration of thiosulfate on films Annex L (Normative) Reference blocks type and specification Page 3 of 91

4 Foreword This Standard, NB/T Nondestructive testing of pressure equipment, consists of the following 13 parts: - Part 1: General requirements; - Part 2: Radiographic testing; - Part 3: Ultrasonic testing; - Part 4: Magnetic particle testing; - Part 5: Penetrant testing; - Part 6: Eddy current testing; - Part 7: Visual testing; - Part 8: Leak testing; - Part 9: Acoustic emission testing; - Part 10: Ultrasonic time of flight diffraction technique testing; - Part 11: X-ray digital radioscopic examination; - Part 12: Magnetic flux leakage testing; - Part 13: Pulsed eddy current testing. This Part is Part 2: Radiographic testing of NB/T This Part is drafted according to the rules provided in GB/T Directives for standardization - Part 1: Structure and drafting of standards. This Part replaces JB/T Nondestructive testing of pressure equipment - Part 2: Radiographic testing, compared with JB/T , main technical changes are as follows: - ENLARGE the application scope of the standard; ADD plug-in fillet joint butt welds, put-type fillet joint butt welds, as well as the detection technology and quality grading requirements for X-ray and γ-ray on tube-plate board welds; CANCEL the classification of steel; - MODIFY and ADD parts of normative references; Page 4 of 91

5 weld, the welds of ellipsoidal head and butterfly head in small γ zone, as well as the welds with continuously changed curvature; - ADD the technical requirements for overlapping in effective evaluation zone; - MODIFY the transmission principle of small-diameter pipe in the case that the structure is limited; - ADD the broadening principle of f when the put-type and plug-in pipe-seat fillet weld source is in inner transmission method; - ADD the placement principle of the distance between the film and the workpiece inspected; - ADD the limit of exposure time for γ-ray source, and the provisions of limiting application of multi-source exposure, as well as the placement requirements of IQI for exposure of the whole sphere; - ADD the recommended technical requirements for application of filter plates; - MODIFY the placement principle of positioning marks and identification marks; - ADD the selection principle for darkroom handling reagent of films, and the contents about delayed time for film handling, as well as quality inspection for film handling; - MODIFY the contents of film s quality requirements; ADD the contents of storage of films; - MODIFY the IQI s sensitivity that different transmission thickness shall meet; ENLARGE the corresponding scope of material thickness; ADD the sensitivity requirements of hole IQI; - ADD the applicable welding structures IN the parts of radiographic testing results at welding joints and quality grading; - ADD and MODIFY the contents of radiographic testing records and reports. - CANCEL the contents of Types and specifications of special IQI ; - MODIFY special reference block for small-diameter tube. This Part is proposed by and shall be under the jurisdiction of National Technical Committee on Boiler Pressure Vessel of the Standardization Administration of China (SAC/TC 262). Drafting organizations of this Part: China Special Equipment Detection Research Page 6 of 91

6 Nondestructive testing for pressure equipment Part 2: Radiographic testing 1 Scope 1.1 This Part of NB/T specifies detection technology and quality grading requirements for X-ray and γ-ray used for welding joints on metal melting of pressure equipment. 1.2 In this Part, the metals used for welding joints of metal melting include steel, copper and copper alloy, aluminum and aluminum alloy, titanium and titanium alloy, nickel and nickel alloy. The types of welding joints include butt welds of plate and tube butt joints (hereinafter referred to as butt welds ), butt welds of plug-in and put-type connecting pipe s fillet joint (hereinafter referred to as fillet welds ) and welds of pipe-pipe sheet welds (refer to Annex A). 1.3 The radiographic testing for other metal materials, welding joints of supporting parts and structural parts of pressure equipment can also refer to this Part. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. GB Standard logarithmic visual acuity charts GB/T Non-destructive testing - Terminology - Terms used in radiographic testing GB Basic standards for protection against ionizing radiation and for the safety of radiation sources GB/T Non-destructive testing - Industrial radiographic films - Part 1: Classification of film systems for industrial radiography GB/T Non-destructive testing - Industrial radiographic films - Part 2: Control of film processing by means of reference values GB/T Non-destructive testing - Industrial radiographic illuminators - Minimum requirements Page 8 of 91

7 GB/T Non-destructive testing - Image quality of radiographs - Part 2: Image quality indicators (step/hole type) - Determination of image quality value GBZ 117 Radiological protection standards for industrial X-ray detection GBZ 132 Radiological protection standards for industrial gamma-radiography NB/T Nondestructive testing of pressure equipment - Part 1: General requirements JB/T 5075 Non-destructive testing - Metal intensifying screens for radiographic testing JB/T 7902 Image quality indicators (wire type) for radiographic testing 3 Terms and definitions For the purpose of this Part, the following terms and definitions and those defined in GB/T and NB/T apply. 3.1 penetrated thickness; W Nominal thickness in radial irradiation direction. In multi-layer penetrating, the penetrated thickness shall be equal to the sum of nominal thickness of each layer of material passed. 3.2 object-to-film distance; b The distance between side surface of radiation source at object s inspected position measured along the central axis of the ray bundle. 3.3 source-to-object distance; f The distance between sides surfaces of radiation source at object s inspected position measured along the central axis of ray bundle. 3.4 focal distance; F The distance between radiation source inspected along the central axis of ray bundle Page 9 of 91

8 feature indications of the film system, see Annex B The film manufacturer shall conduct system performance test to the films produced, provide types and parameters. The handling methods, equipment and chemical agents shall meet GB/T , using the pre-exposure films provided by the film manufacturer to test and control. The film exceeding using period specified by the film manufacturer can t be used. And the film shall be stored according to the temperature and humidity conditions recommended by the manufacturer, avoid any ionizing radiation Film viewer Main performance of the film viewer shall meet relevant provisions of GB/T 19802, and the maximum brightness shall meet the requirements of film evaluation Nigrometer (optical densimeter) The maximum blackness that can be tested by the nigrometer shall be not less than 4.5, and the measuring error shall not exceed ± Before being used for the first time, the nigrometer shall be checked, and then it shall be checked every 6 months at least. The inspection method shall meet the provisions of Annex C, and the records shall be made for inspection each time. When the work begins or after continuous work for 8 h, two points shall be selected at least for inspection within the blackness scope to be measured Film with standard density The standard density film shall include 8 blackness criteria with certain intervals, which can cover the scope of 0.3 ~ 4.5 and the films shall be calibrated every two years at least. The storage and using conditions of standard density films must be specially paid attention to Intensifying screen In general, for radiographic testing, the metal intensifying screen can be used or no intensifying screen can be used, the metal intensifying screen shall meet the requirements of JB/T 5075, and the intensifying screen shall be completely cleaned, polished, without track When the intensifying screen is used, the film shall well touch intensifying screen. And selection of intensifying screen shall meet the provisions of Table 1. Table 1 Materials and thickness of the intensifying screen Radiation source Material Front screen Rear screen Medium screen c Page 12 of 91

9 4.3.2 Selection of the radiographic testing technique s levels shall meet the requirements of relevant laws, regulations, standards and design documents, at the same time; it shall meet other technical requirements agreed by the both parties. For radiographic testing of the pressure equipment s welding joints, in general, level AB radiographic testing technique is used. For the welding joints on important equipment, structures, and special materials, as well as the welding joints made with special process, level-b technique shall be used for inspection When some conditions in the test can t meet the requirements of level-ab (or level B) radiographic testing technique, through the negotiation of the both parties, under the premise of adopting effective compensation measures (For example: Select the films of higher class), if the IQI s sensitivity can meet the requirements of radiographic testing technique for level-ab (or level B), the test can be considered as being detected with level-ab (level B) radiographic testing technique When the pressure equipment is used in the inspection, if some inspection conditions can t meet the requirements of level AB radiographic testing technique, through negotiations between the both parties, effective compensation measures shall be taken (For example: Select the films of higher class), and then level-a technique can be used for radiographic testing, while, at the same time, other NDT methods shall also be used for compensation. 4.4 Process documents for inspection The process documents for inspection include process rules and operation instructions The process rules shall meet the requirements of NB/T , in addition, specific scope or requirements of the following relevant factors shall also be specified; if changes of relevant factors exceed the requirements, the process rules shall be reprepared or revised: a) Structure, material types and thickness in the applicable scope; b) Types, energy and focal size of the radiation sources; c) Levels of the inspection technique; d) Penetrating technique; e) Penetrating methods; f) Type and levels of the films; g) Type of the IQI; h) Types of the intensifying screen and filter plate (If any); Page 15 of 91

10 4.5.2 When X-ray inspection is conducted on site, the control zone and management zone shall be designated, and warning signs shall also be set according to the requirements of GBZ 117, the inspector shall carry personal dosimeter and dosage alarm apparatus When γ-ray inspection is conducted on site, the control zone and supervision zone shall be designated according to requirements of GBZ 132, and warning signs shall also be set, in the period of inspection operation, the radiation level shall be measured at boundary of the control zone. The inspector shall carry personal dosimeter and dosage alarm apparatus. 5 Inspection process and its selection 5.1 Inspection opportunity The inspection opportunity shall relevant provisions, specifications, standards and design documents, at the same time; it shall meet other technical requirements agreed by the both parties Unless otherwise specified, radiographic testing shall be conducted after production of the welding joints being completed, for the materials with delayed cracks; the welding joints shall be made 24 h after the welding being completed. 5.2 Inspection zone The inspection zone s width shall meet relevant laws and regulations, specifications, standards and design technical documents, at the same time, it shall meet other technical requirements agreed by the both parties, for the welding joints of non-electroslag welding, in general, the width shall meet the following requirements: a) For the butt welds, the inspected zone shall include the welds metal, as well as adjacent base metal zone with the relative distance of 5 mm at least to edge of the welds. b) For the fillet welds, the inspection zone shall include welds metal and adjacent base metal zone, or adjacent base metal zone of plug-in main pipe (or cylinder, end socket and panel etc.) with the relative distance of 5mm at least to the welds edge For the electroslag welding joints, the width of inspection zone can be determined with the measured HAZ, or through the negotiations between the both parties. 5.3 Surface requirements Before radiographic testing, surface of the welding joints shall be qualified by visual Page 17 of 91

11 T (wall thickness) 8 mm; g (width of the welds) D o /4 In elliptic imaging, the image s open width (maximum interval of the upper-lower welds projections) shall be controlled to be one time of about the weld s width. If the conditions above can t be met, or elliptic imaging is difficult to achieve, the overlapping imaging with vertical penetrating can be used Penetrating times of small-diameter tube s circular welding joints The penetrating times for 100% inspection of small-diameter tube s circular welding joints: When the elliptic imaging adopts tilt penetrating, if T/D o is 0.12, the interval is 90, and the penetrating times are twice. If T/D o is > 0.12, the interval is 120 or 60, the penetrating times are three times. If vertical penetrating overlapping imaging is used, in general, the interval is 120 or 60, and the penetrating times shall be 3; When multi-penetrating is conducted according to the provisions above, the zone where the blackness in inspected zone on the film meet is effective evaluation zone, the overlapping of effective evaluation zones of adjacent films shall be able to ensure to cover whole volume scope of the inspected zone, If the minimum exposure times can t meet the requirements of 100% coverage, the exposure times shall be increased Special situations If multi-penetrating can t be conducted at the interval angle specified in because of the structure, through negotiation between the both parties, the interval angle specified in can be not mandatorily limited anymore,but effective measures shall be taken to enlarge inspectable scope of flaws as far as possible, at the same time, to ensure that the blackness and sensitivity in the evaluation scope of films can meet the requirements, and relevant situations can be explained in the inspection reports. 5.6 Ray energy Under the premise of ensuring penetrating power, X-ray imaging shall adopt low tube voltage. If the high tube voltage is used, the proper exposure shall be ensured. Figure 1 indicates the maximum X-ray tube voltage allowed for different materials and penetrating thicknesses For the pressure equipment that the section thickness is not changed greatly, under the premise of ensuring sensitivity, the X-ray tube voltage exceeding to the specified value in Figure 1 can be used. But for steel, copper and copper alloy, as nickel and nickel alloy materials, the tube voltage increment shall not exceed 50 KV; For tantalum and tantalum alloy materials, the tube voltage increment shall not exceed 40 KV; For aluminum and aluminum alloy materials, the tube voltage increment shall Page 20 of 91

12 center penetrating method is used (Figure E.9 and E.13 in Annex E), if quality of the film meets requirements of and , the value of f can be reduced, but the reduced value can t exceed 50% of specified value When the put-type and plug-in fillet welds adopt source included single-wall center penetrating method is used (Figure E.9 and E.13 in Annex E), if quality of the film meets requirements of and , the value of f can be reduced, but the reduced value can t exceed 50% of specified value When the put-type and plug-in fillet welds adopt source included single-wall eccentricity penetrating method is used (Figure E.10 and E.14 in Annex E), if quality of the film meets requirements of and , the value of f can be reduced, but the reduced value can t exceed 20% of specified value If the allowable maximum geometric sharpness (U g ) has been specified by relevant laws and regulations, specifications, standards, design technical documents or through negotiations between the both parties, in actual penetrating, the geometric sharpness (U g ) shall be calculated according to Annex H. 5.8 The distance between the film and object inspected In the period of exposure, the film shall be close to the object, unless special provisions or the penetrating arrangement can ensure to get better penetrating images of the inspected zone. When the source included penetrating of fillet welds is used, the film shall be close to welds on the inspected object as far as possible. 5.9 Exposure quantity X-ray radiography, when the focus is 700 mm, recommended value of the exposure quantity is: For level A and level AB radiographic testing techniques, the value shall be not less than 15 ma min; for level B radiographic testing, the value shall be not less than 20 ma min. When the focus is changed, recommended value of the exposure quantity can be calculated according to inverse square law When γ-ray is used for penetrating, the total exposure time shall be not less than 10 times that the time needed for back and forth of transmission source When Co60 γ-ray is used for penetrating, the exposure time shall not exceed 12 h; When Ir192 γ-ray is used for penetrating, the exposure time shall not exceed 8 h, multiply radiation sources can t be bundled for penetrating Exposure curve For each set of ray equipment being used, the exposure curve of frequent inspection material shall be made, to determine exposure parameters according to the exposure curve. Page 25 of 91

13 Placement of the IQI shall also meet the following requirements: a) For single-wall penetrating, the IQI shall be placed on side of the radiation source. According to the requirements, for double-wall single-image penetrating, the IQI shall be placed on side of the film. For double-wall and double-image penetrating, the IQI can be placed on side of the radiation source, and it can also be placed on side of the film; b) For single-wall penetrating, if the IQI can t be placed on side of the radiation source, it can be placed on side of the film (except for exposure of sphere s full view); c) For single-wall penetrating, when the IQI is placed on side of the film, the contrast test can be conducted. Method of the contrast test is to respectively place an IQI on side of the radiation source and the side of film, and the penetrating can be conducted under the conditions same with those of the object, to measure difference of sensitivity that the IQI is placed on side of the radiation source and side of the film, to correct sensitivity provisions of the IQI, so that the sensitivity of film actually penetrated meets the requirements; d) When the IQI is placed on side of the film, the letter F shall be placed at proper position on the IQI as the mark, image of F mark shall appear on the film with mark of the IQI at the same time, and which shall be indicated in the inspection report Quantity of the IQI In principle, there shall be image of the IQI on each film. When multiply film photos are completed with one exposure, the IQI s quantity used can be reduced, but which shall meet the following requirements: a) When the source of circular welding joints is placed at the center for circular exposure, 3 IQIs at least shall be placed on the circular at equal interval; b) When the source of sphere welding joints is placed at the center for full-view exposure, the IQI shall be placed on each film of upper-pole and lower-pole welds, and 3 IQI at least shall be placed at equal interval on longitudinal welds and circular welds of each zone; c) For multiply films continuously arrayed in one-time exposure, the IQI shall be respectively placed on the first, medium and the last film Small-diameter tube butt welds When the small-diameter adopts universal line-type and special isometric line-type IQIs, the metal line shall be vertical to the welds, and placed cross the welds. Page 27 of 91

14 When residual height inside and outside of the welds is removed, the inspection zone s position and width can t be determined from the film, proper positioning marks shall be used (such as lead strip) for identifying The pre-exposure method can be used to get relevant identification marks, but effective measures must be taken to ensure that corresponding inspected zone on the object can be traced according to pre-exposure marks on the film, and some measures shall be taken to ensure that the zone without identification marks can t be exposed The positioning marks shall be placed on the object, and its placement shall meet the requirements of Annex J. Images of all marks can t overlap. And the image within effective evaluation can t be interfered. When the positioning marks on side of the radiation source needs to place on side of the film because of the structure, the inspection records and report shall be remarked with actual evaluation scope The identification marks can be placed on side of the radiation source or the side of the film, all images of the marks shall not overlap, and which can interfere the images within effective evaluation scope In order to identify position of the film accurately, permanent identifications or position features on the object shall be treated as the reference points; if permanent identifications can t be made because of the material s nature and using conditions, other methods shall be used (film arrangement chart) to determine position of the film Film processing and quality inspection Film processing In general, film processing is conducted according to instructions of the film. Which can be processed with automatic washing or manual washing, the automatic method is recommended. In general, the washing formula or drugs produced or recommended by the film manufacturer, and the requirements of GB/T shall be met, the formula or drugs produced by other manufacturers can also be used through comparison and tests. Manual processing and automatic processing of films shall be completed within 8h after exposure; it shall not exceed 24 h Quality inspection of the films In general, after darkroom processing, the concentration of thiosulfate ions shall be less than g/m 2. The concentration measurement can be conducted according to requirements of Annex K, and the measurement results shall be recorded. The inspection frequency shall be determined by the inspection party, but, in this period, the darkroom processing conditions shall be not changed. Page 29 of 91

15 Level A: 1.5 D 4.5; Level AB: 2.0 D 4.5; Level B: 2.3 D For penetrating technique of double-film, observation evaluation of doublefilm overlapping, the blackness D within the evaluation scope shall meet requirements of 2.7 D 4.5. Note 1: In overlapping evaluation of double-film, for the local zone where the blackness exceeds 4.5, if single-film blackness scope meets the requirements of , this zone can be conducted with single-film evaluation. Note 2: When similar films are used, the blackness difference measured at same points on each film in effective evaluation zone shall not exceed 0.5. Note 3: Any blackness of single-film used for overlapping evaluation of double-films shall be not less than 1.3. Note 4: Each film shall be observed, analyzed and stored at the same time Using X-ray to penetrate small-diameter tube or other objects with large changes in thickness of section thickness, when the single-film is observed and evaluated, the minimum blackness of level AB can be reduced to 1.5; for level B, the minimum blackness can be reduced to When the inspection zone is evaluated, the blackness scopes corresponding to the zones of different film penetrating technique or different film observation technique shall be respectively identified in the report The maximum blackness limit in evaluation zone can be improved, but the film viewer shall be verified, brightness of the film viewer shall be able to ensure that the brightness within the scope of film s highest evaluation can meet the requirements of IQI sensitivity of the film For single-wall penetrating, when the IQI is placed on side of the radiation source, the sensitivity shall meet requirements of Table 5 and Table 6; for double-wall doubleimage penetrating, when the IQI is placed on side of the radiation source, the sensitivity shall meet requirements of Table 7 and Table 8; for double-wall single-image or doublewall double-image penetrating, when the IQI is placed on side of the film, the sensitivity shall meet the requirements of Table 9 and Table Other requirements Page 31 of 91

16 6.1.4 General provisions of quality grading There shall be no crack, incomplete fusion, lack of penetration and stripy flaw in level I welding joints There shall be no crack, incomplete fusion, and lack of penetration in level II and level III welding joints When there are round flaw and stripy flaw in round evaluation zone of flaw, the flaw shall be comprehensively ranked, that is, the quality levels of round flaw and stripy flaw in flaw evaluation zone shall be respectively evaluated, sum of the two levels subtracts one as quality level of the comprehensive grading In addition to comprehensive grading, when quality levels of various flaw evaluations are different, the lowest quality level shall be treated as quality level of the welding joints When quality levels in flaw evaluation of the welding joints exceed level III, they shall be determined as level IV Quality grading of round flaws The round flaws adopt round flaw evaluation zone for quality grading evaluation, the round flaw evaluation zone is a rectangle parallel to the welds, for the size, see Table 12. The evaluation zone of round flaw shall be the zone with the most serious flaws The flaws in found flaw evaluation zone or those intercrossing with boundary of round flaw evaluation zone shall be included into the evaluation zone. To convert the flaws in evaluation zone into counts according to requirements in Table 12, while quality levels of the welding joints shall be evaluated according to requirements of Table 13. Table 11 Flaw evaluation zone of melting welding joints of the pressure ~ bearing equipment made of steel, nickel and copper In mm Nominal thickness of the base metal T 25 > 25 ~ 100 > 100 Size of the evaluation zone Table 12 Conversion table of flaw counts for melting welding joints of pressure equipment made of steel, nickel and copper Flaw length/mm 1 > 1 ~ 2 > 2 ~ 3 > 3 ~ 4 > 4 ~ 6 > 6 ~ 8 > 8 Flaw counts Table 13 Allowable counts of round flaws for melting welding joints of Page 36 of 91

17 Cracks, incomplete fusion, incomplete penetration, copper inclusion, stripy flaws and round flaws Division of quality levels According to nature, quantity and density of flaws in welding joints, the quality levels can be divided into level I, II, III and IV General provisions for quality grading There shall be no crack, incomplete fusion, incomplete penetration, copper inclusion and stripy flaws in level I welding joints There shall be no crack, incomplete fusion, incomplete penetration, and copper inclusion flaws in level II and III welding joints If there are round flaws and stripy flaws in evaluation zone of round flaws, comprehensive grading shall be conducted, that is, the quality levels of round flaws and stripy flaws in evaluation zone of round flaws shall be respectively evaluated, sum of the two levels subtracts one as quality level of the overall rating In addition to overall rating, when quality levels in evaluation of various flaws are different, the lowest quality level shall be treated as quality level of the welding joints When the quality levels in flaw evaluation of welding joints exceed level III, all of them shall be treated as level IV Grading evaluation of round flaws The round flaws shall adopt the evaluation zone of round flaws for evaluation of quality grading, the evaluation zone of round flaws is a rectangle parallel to the welds, for its size, see Table 16. The evaluation zone of round flaws shall be the zone with the most serious flaws The flaws in found flaw evaluation zone or those intercrossing with boundary of round flaw evaluation zone shall be included into the evaluation zone. To convert the flaws in evaluation zone into counts according to requirements in Table 17, while quality levels of the welding joints shall be evaluated according to requirements of Table 18. Table 16 Flaw evaluation zone of melting welding joints of the pressure ~ bearing equipment made of aluminum In mm Nominal thickness of the base metal T 20 > 20 ~ 80 Page 39 of 91

18 Nominal thickness of the base metal T Flaw length T < T T > % T In mm Grading evaluation of stripy flaws The stripy flaws shall be evaluated in grading according to the requirements of Radiographic testing result evaluation and quality grading for melting welding joints of pressure equipment made of tantalum and tantalum alloy Scope This clause is suitable for the radiographic testing result evaluation and quality grading of the welding joints for pressure ~ bearing equipment made of tantalum and tantalum alloy with the thickness of 2 mm ~ 50 mm, types of the welding joints applied include the butt welds of two-side melting welding, the butt welds of full penetration equivalent to two-side welding, as well as single-side welding butt welds with sub-plate close to the base metal along whole length of the root welds Types of flaws According to nature and forms, flaws in welding joints can be divided into 5 classes: Cracks, incomplete fusion, incomplete penetration, stripy flaws and round flaws Basis of quality levels According to nature, quantity and density of flaws in welding joints, the quality levels can be divided into level I, II, III and IV General provisions for quality grading There shall be no crack, incomplete fusion, incomplete penetration, stripy flaws in level I welding joints There shall be no crack, incomplete fusion, incomplete penetration, and copper inclusion flaw in level II and III welding joints If there are round flaws and stripy flaws in evaluation zone of round flaws at the same time, comprehensive grading shall be conducted, that is, the quality levels of round flaws and stripy flaws in evaluation zone of round flaws shall be respectively evaluated, sum of the two levels subtracts one as quality level of the overall rating In addition to overall rating, when quality levels in evaluation of various flaws are different, the lowest quality level shall be treated as quality level of the welding Page 41 of 91

19 This clause is suitable for the radiographic testing result evaluation and quality grading of the butt circular welding joints for pressure equipment s pipes and pressure pipelines made of steel, nickel and nickel alloy; copper and copper alloy with the thickness of T 2 mm, types of the welding joints applied include the butt welds of single-side welding added with sub-plate close to the base metal along whole length of the root welds, and the single-side butt welds without sub-plate Types of flaws According to nature and forms, flaws in welding joints can be divided into 7 classes: Cracks, incomplete fusion, incomplete penetration, stripy flaws, round flaws, indent at roots, and undercut at roots etc Division of quality grades According to nature, size, quantity and density of flaws in welding joints, the quality levels can be divided into level I, II, III, and IV General provisions of quality grading There shall be no crack, incomplete fusion, lack of penetration, stripy flaw, indent at roots, and undercut at roots etc. in level I welding joints There shall be no crack, incomplete fusion, and incomplete penetration of single-side welding with sub-plate in level II and level III welding joints If there are multiply flaws at the same time in evaluation zone of stripy flaw, the flaw shall be comprehensively graded, that is, the quality levels of various flaws in stripy flaw evaluation zone shall be respectively evaluated, the level with lowest quality level shall be treated as the level of overall rating; when levels of various flaws are the same, the level of overall rating shall be degraded for one level In addition to overall rating, when quality levels of various flaw evaluations are different, the lowest quality level shall be treated as quality level of the welding joints When quality levels in flaw evaluation of the welding joints exceed level III, they shall be determined as level IV Grading evaluation of round flaws The quality grading evaluation shall be conducted according to 6.1.5, but value of flaw evaluation zone of small-diameter tube shall be taken as 10 mm 10 mm Quality grading evaluation of stripy flaws The quality grading evaluation shall be conducted according to Page 44 of 91

20 when levels of various flaws are the same, they shall be reduced for one level as level of the overall rating In addition to overall rating, when quality levels in evaluation of various flaws are different, the lowest quality level shall be treated as quality level of the welding joints When the quality levels in flaw evaluation of welding joints exceed level III, all of them shall be treated as level IV Grading evaluation of round flaws The quality grading evaluation shall be conducted according to Grading evaluation of stripy flaws The quality grading evaluation shall be conducted according to Grading evaluation for incomplete penetration flaws of single side without sub-plate The quality grading evaluation shall be conducted according to Grading evaluation of root indent and undercut The quality grading evaluation shall be conducted according to Radiographic testing result evaluation and quality grading for melting welding circular joints of pressure equipment s pipes and pressure pipes made of tantalum and tantalum alloy Scope This clause is suitable for the radiographic testing result evaluation and quality grading of melting welding circular joints for pressure equipment s pipes and pressure pipe made of tantalum and tantalum alloy with the wall thickness T of 2 mm, types of the welding joints applied include the butt welds of single-side melting welding the subplate closed to basic metal along whole length of the welds root, and the single-side butt welds without sub-plate Types of flaws The flaws shall be classified according to Division of quality levels According to nature, quantity and density of flaws in welding joints, the quality levels can be divided into level I, II, III and IV. Page 48 of 91

21 b) Inspected object: Name, inspection location, type of weld groove, and welding methods; c) Inspection equipment and apparatus: Radiation source (kind, type and focal size); film (brand and grade); intensifying screen (type, quantity and thickness), IQI (kind and type), filter plate, back-scattering shielding lead plate; d) Process parameters for inspection: Technical grade for inspection, penetration technique (single film or double-film), penetrating method, penetrating parameters, F, f and b, tube voltage, tube current, exposure time (or source strength and exposure time), methods and conditions for darkroom processing; e) Film evaluation: Film s blackness, sensitivity of the film IQI, position and nature of flaws; f) Film arrangement chart; g) Process verification of the operation instructions (if necessary); h) Inspection results and quality grading; i) Preparation and review personnel as well as their technical qualifications; j) Other matters need to explain or record. 8.2 The inspection report shall be issued according to the inspection records. The radiographic testing report shall also include the following contents at least, in addition to meeting the provisions of NB/T : a) Entrusting party or manufacturer; b) Inspected object: Name, inspection location, type of weld groove, and welding methods; c) Inspection equipment and apparatus: Radiation source (kind, type and focal size); film (brand and grade); intensifying screen (type, quantity and thickness), IQI (kind and type), filter plate, back-scattering shielding lead plate; d) Process parameters for inspection: Technical grade for inspection, penetration technique (single film or double-film), penetrating method, penetrating parameters, F, f and b, tube voltage, tube current, exposure time (or source strength and exposure time), methods and conditions for darkroom processing; e) Film evaluation: Film s blackness, sensitivity of the film IQI, position and nature of flaws; f) Inspection results and quality grading; Page 50 of 91

22 Annex A (Informative) Radiography requirements for tube-fillet welds A.1 Scope The annex specifies X-ray and γ-ray radiographic testing technique and quality grading requirements for the tube-fillet welds. The annex is suitable for radiographic testing of tube and fillet welds of the tube-shell tabulation heat exchanger and tube-shell reactor, the welding type is seal weld. Scope of inner diameter of the tubes inspected: 12.5 ~ 80 mm; thickness scope: 1.0 mm ~ 5.0 mm, the metal materials used for fabricating welding joints include: Steel, tantalum and tantalum alloy, nickel and nickel alloy, zirconium and zirconium. The radiographic testing technique specified by the annex is divided into 3 levels: Level A - Low-sensitivity technique; Level AB - Medium sensitivity technique; Level B - High sensitivity technique. The radiographic testing for smaller inner diameter tubes-fillet welds can also refer to the annex, but smaller source rod size and proper process parameters shall be needed; radiographic testing of strength fillet welds can also refer to this annex, but the sensitivity and flaw evaluation shall be specified otherwise. A.2 Terms and definitions A.2.1 film after source The penetrating method that the film is placed in the rear of radiation source (figure A.1). When such method is used for inspection, the radiation source can be led to the tube from the side-tube plate with a stiffness pipe, the radiation source can be easily aligned, and the distance from radiation to films can be accurately controlled, easy to take photos, but special radiation source and tooling shall be needed, center of the film used must have a pore. A.2.2 film before source The penetrating method that the film is placed in the front of radiation source (figure A.2). When such method is used for inspection, the radiation source can be led to the tube from the side-tube plate with a flexibility or stiffness pipe, and through whole Page 52 of 91

23 A In general, the radiographic testing of tube-fillet welds adopts lead intensifying screen. If γ-ray penetration and vacuum package of lead intensifying screen with the thickness of 0.03 mm are used, a latten shall be placed between the cassette and object as the filter plate. A For different object materials, the intensifying screen and filter plates used for films shall meet the requirements of Table A.2. Table A.2 Intensifying screen and filter plates used for different object materials, sources and films Object material Steel, nickel and nickel alloy, Tantalum and tantalum zirconium and zirconium alloy alloy Packing types of films Bulk films Films in vacuum package Bulk films Films in vacuum package X-ray Intensifying screen and thickness/mm Lead screen: < lead Intensifying screen Lead screen: screen and thickness/mm 0.03 γ-ray 0.20 N/A Thickness of the filter plates/mm Tin 0.50 A.3.5 Film viewer A Main performance of the film viewer shall meet relevant requirements of GB/T A The film viewer for evaluating and observing shall be equipped with a visor for tube-fillet welds. A.3.6 Welding samples for qualification test of the sensitivity Prepare a special welding sample for testing the sensitivity of tube-tube plate fillet welding joints, tube materials, specification of the sample shall be the same with those of actual products. 4 pores at least shall be processed with the interval of 90 on central line of the welds with punching or drilling method, size of the pore shall meet the technical levels specified in the contract. The image in the film can be used to verify suitability of the image quality. A.3.7 Compensator A In general, outer diameter of the compensator shall be not less than inner diameter of the tube D i - 1 mm. Page 55 of 91

24 A.4 Specific requirements A.4.1 Arrangement of the penetrating For radiographic testing of tube-fillet welds, the penetrating-backward method shall be used in priority, when such method can t be used, the penetrating-forward method can be used, but only for level A. A.4.2 The distance between the focus and films A The distance from the focus to film shall be selected according to tube s inner diameter, when the distance is selected, the projection distortion factor shall be considered to reduce, at the same, photographic sensitivity factor shall also be considered. A When inner diameter of the tube is D i 20 mm, the recommended distance is 30 mm; For D i > 20 mm ~ 38 mm, the recommended distance is 40 mm; for D i > 38 mm, the distance shall be determined through process tests. A.4.3 Exposure time The exposure time of γ shall be not less than 20 s. A.4.4 Identification of the object Before radiographic testing, the tube ~ tube plate joint on the object to be inspected shall be marked. And the mark s contents shall include tube ~ plate number, line number and tube number. Identification of the tube can be made with a marking pen or chalk, while, in general, the tube-plate identification adopts steel seals. A.4.5 Identification of films A The film identification shall include product number, tube plate number, line number and tube number at least. After being re-worked, the film shall also be made with R, the film for enlarging inspection penetrating shall be equipped with the enlarging mark of K. A In general, the film identification of radiography for tube-fillet welding joints doesn t adopt lead letter, which can be identified with the marking pen or printing method. When the printing is used, the film shall be made with steel seal before exposure. A.5 Film s evaluation scope and quality requirements A.5.1 Evaluation scope of films The evaluation scope of films not only includes the tube-fillet welds inspected, it also Page 57 of 91

25 Annex C (Informative) Regular inspection methods of the nigrometer (optical densimeter) C.1 General provisions for regular inspection of the nigrometer The nigrometer can be inspected according to the methods recommended by the manufacturer or provisions of C.2. C.2 Verification steps for the nigrometer. C.2.1 Connect the nigrometer s power supply and measuring switch, to preheat it for about 10min. C.2.2 Using zero blackness point (zone) of standard density sheet to adjust zero point of the nigrometer, and then measure the blackness at various points and record the measured values. C.2.3 The measurement shall be conducted for three times repeatedly according to the requirements of C.2.2. C.2.4 Calculate mean of the measured values at various points, the difference between the mean and the blackness value at this point shall be treated as measuring error of the nigrometer. C.2.5 For various points whose blackness is not larger than 4.5, their measuring error shall not exceed ± 0.05, or the nigrometer shall be adjusted, repaired and abandoned. Page 61 of 91

26 Annex D (Informative) Determination of darkroom s safety irradiation time D.1 Scope The annex is suitable for determination of film darkroom s safety irradiation time for industrial radiographic testing. D.2 Definition D.2.1 Changes of inspectable blackness The slight difference of the film s blackness that can be measured with visual inspection or with the nigrometer. D.2.2 Irradiation test before the exposure For safe light irradiation test before the film being exposed by rays, the longest irradiation time of safety-light in which no blackness change is inspected on the test strip determined by the test shall be safety irradiation time t 1 before exposure. D.2.3 Irradiation test after exposure It refers to the irradiation test of safety light before beginning of the developing process after the film being exposed in keeping dry state, the longest irradiation time of safetylight in which no blackness change is inspected on the test strip determined by this test shall be safety irradiation time after exposure t 2. D.2.4 Post ~ exposure irradiation test of damp films after exposure It refers to the irradiation test of safety light from beginning of the developing process to end of it (or beginning of fixing) in humidity state; the longest irradiation time of safety-light in which no blackness change is inspected on the test strip determined by this test shall be safety irradiation time after exposure of the humid films t 3. D.2.5 Safety irradiation time of darkroom It refers to the time t that can be obtained by the test and be able to ensure that irradiation of safety-light doesn t affect the film s blackness, it shall be one half of the minimum in t 1, t 2 and t 3. D.3 Test apparatus Page 62 of 91

27 D.5.1 Measurement opportunity The test strips that have undergone darkroom processing shall be conducted blackness measurement after being dried. D.5.2 Measurement and comparison of the nigrometer The measurement method of blackness shall be consistent with that of the films in actual production. Using the nigrometer to measure each level of the test strip one by one, record the blackness with/without undergoing irradiation of safety light and compare them, to find the level where the blackness change can be found. In general, if the blackness change exceeds ± 0.05, it shall be considered as that the change of blackness can be inspected. D.5.3 Visual measurement and comparison The visual observation conditions shall be consistent with the observation conditions of films in actual production. Observe the blackness with/without undergoing irradiation of safety light and compare them, to find the strip which has undergone the longest irradiation of safety light, but no blackness change can be inspected. D.6 Determination for darkroom s safety irradiation time D.6.1 Treat one half of the minimum in t 1, t 2 and t 3 obtained from the test as the irradiation time of safety light allowable in the process of darkroom processing, that is, safety irradiation time of the darkroom. D.6.2 If the safety irradiation time determined by the test is insufficient for completing the whole darkroom processing, the safety light shall be considered to replace, and the safety irradiation time shall be re-determined by tests. D.6.3 In actual production, darkroom processing of the films shall be conducted under the safety irradiation time, safety distance and other parameters determined by the test. D.7 Test report The report shall include the following contents at least: a) Type and relevant parameters of the safety light, such as voltage, power of the bulb, as well as name and size of the filtering piece; b) The relevant position and distance between the safety light and films shall include the distances of pre-exposure operation, post-exposure operation and developing operation; c) Films (brand and classification levels) and darkroom processing parameters Page 65 of 91