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 3: Ultrasonic testing 承压设备无损检测第 3 部分 : 超声检测 Issued on: April 02, 2015 Implemented on: September 01, 2015 Issued by: National Energy Administration Page 1 of 180

2 Table of Contents Foreword Scope Normative references Terms and definitions General requirements Ultrasonic testing methods and quality grading for standby raw material or components of pressure equipment Ultrasonic testing method and quality grading of welded joint for pressure equipment Ultrasonic measuring methods for thickness of pressure equipment Ultrasonic testing methods of in-service pressure equipment Ultrasonic testing records and reports Annex A (Normative) Requirements for electrical performance indicators of ultrasonic testing instruments Annex B (Normative) Requirements for performance indicators of probe used for ultrasonic testing Annex C (Normative) Requirements for performance of double-crystal straight probe Annex D (Normative) Ultrasonic testing methods and acceptance standard for plates used for pressure equipment by using an angle probe Annex E (Normative) Ultrasonic testing methods (by using an angle probe) and quality classification of steel forgings used for pressure equipment Annex F (Normative) Ultrasonic testing methods (by using an angle probe) for austenitic steel forgings used for pressure equipment Page 2 of 180

3 Annex G (Normative) Ultrasonic testing method and quality classification of the welding overlay of pressure equipment Annex H (Normative) Ultrasonic testing method and quality classification of the butt joints of pressure equipment made by aluminum & aluminum alloy and titanium Annex I (Informative) Ultrasonic testing method and quality classification of the butt joints of austenitic stainless steel Annex J (Normative) Ultrasonic testing method of the curved longitudinal butt joints of pressure equipment Annex K (Normative) Ultrasonic testing method of the curved circumferential butt joints of pressure equipment Annex L (Normative) Ultrasonic testing method of fillet joints for nozzles and shells (or heads) of pressure equipment Annex M (Normative) Ultrasonic testing method of T-type welding joints Annex N (Normative) Specific requirements for the ultrasonic testing for welding joints of different types Annex O (Normative) CSK-III A Test specimen Annex P (Normative) Determination of the loss difference during sound energy transmission Annex Q (Normative) Echo dynamic patterns Annex R (Normative) Defect Height Measurement Method (I) Measure defect height by the endpoint wave diffraction method Annex S (Normative) Defect Height Measurement Method (II) The End Echoes Diffraction Method to Measure the Defect Height Annex T (Normative) Defect Height Measurement Method (III) Using -6 db method for measuring defect heights Page 3 of 180

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 3: Ultrasonic 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 3: Ultrasonic testing. The main technical changes are as follows, compared with JB/T : - ADD terms and definitions, including terms and definitions related to ultrasonic testing in the former JB/T ; - REPLACE JB/T Shape A Pulse Reflection Ultrasonic Flaw Detector - General Technology Condition WITH GB/T Nondestructive Testing Performance and Inspection of Ultrasonic Testing Equipment - Part 1: Instrument. Put forward more scientific requirements for performance of ultrasonic testing Page 4 of 180

5 - REDESIGN the position and the number of the artificial reflector on CSK-IIA and CSK - IVA blocks. In this way, it not only guarantees the coverage of the detection area coverage, but also is suitable for adjustment of the straight probe benchmark sensitivity. New CSK-IIA block is applicable for work piece with thickness scope of 6 mm ~ 200 mm, mainly referring to the European Union (EN) and Japanese standard (JIS). New CSK-IVA block is applicable for work piece with thickness scope greater than 200 mm ~ 500 mm, and makes improvement on basis of mainly referring to the ASME codes. The block diameter of artificial reflector shall be 6 mm; - REFINE the weld ultrasonic testing requirements for different types. It involves flat butt joint, T-shaped welded joint, plug-in Angle joint, L-shaped welded joint, placement type pipe and cylinder (or seal-end socket) angle joint, cross welding joint, embedded type pipe and cylinder (or end socket) butt joint etc. - REDESIGN the GS test block. Increase the circular arc surfaces etc. It is mainly beneficial to adjusting time base of arc probe; - LIMIT the length of non-crack defect in Zone I in quality grade of weld joint; - ADJUST overall formulation structure involved in weld joint ultrasonic testing. The ultrasonic testing method of connecting pipe and cylinder (head) angle joint, ultrasonic testing method of T-shaped weld joint, ultrasonic testing method and quality grading of surfacing welding layer are included into the annex; - ADD ultrasonic thickness measurement method for the pressure equipment in accordance with actual testing requirements, including measurement method for stainless steel surfacing layer thickness; - When pressure equipment is used to conduct ultrasonic detection, ADD failure mode of host materials, components or welded joint which may be caused in use process or analysis results of risk evaluation to select ultrasonic testing method, detection parts and detection proportion. 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: Hefei General Machinery Research Institute, China Special Equipment Inspection Institute, Shanghai Electric and Nuclear Power Equipment Co., Ltd., China First Heavy Machinery Group Dalian Hydrogenation Reactor Manufacturing Co., Ltd., Jiangsu Special Equipment Safety Supervision and Inspection Research Institute, and Lanzhou Lanshi Heavy Equipment Co., Ltd. Main drafters of this Part: Yan Changzhou, Zheng Hui, Xu Zunyan, Zhou Fengge, Zhou Yufeng, Tao Yuanhong, Zheng Kai, Gu Jie, Zhang Baozhong and Pan Qianghua. Page 6 of 180

6 Nondestructive testing of the pressure equipment - Part 3: Ultrasonic testing 1 Scope 1.1 This Part of NB/T specifies the pressure equipment shall adopt ultrasonic testing method and quality grading requirements in which shape A pulse reflection ultrasonic detector is used to test work piece defect. 1.2 This Part is applicable to ultrasonic detection for metal material system pressure equipment with raw materials or components and welded joint, and be applied to ultrasonic detection of metal materials used in the pressure equipment. 1.3 This Part specifies ultrasonic measuring method for thickness of the pressure equipment. 1.4 Ultrasonic detection of supporting parts and structural piece related to the pressure equipment can also refer to this part. 2 Normative references The following documents are necessary to the application of this document. For all dated references, only the dated edition applies to this document. for all undated references, the latest edition (including all amendments) applies. GB/T Non-destructive testing - Practice for fabrication and control of steel reference blocks used in ultrasonic testing GB/T Non-destructive testing - Terminology - Terms used in ultrasonic testing GB/T Non-destructive testing - Characterization and verification of ultrasonic test equipment - Part 1: Instruments GB/T Non-destructive testing - Characterization and verification of ultrasonic test equipment - Part 2: Probes JB/T 8428 Non-destructive testing - Blocks for ultrasonic testing JB/T 9214 Non-destructive testing - Practice for evaluating performance characteristics of A scope ultrasonic pulse - Echo testing systems Page 8 of 180

7 JB/T Testing methods for performance of probes used in ultrasonic flaw detection NB/T Nondestructive testing of pressure equipment 3 Terms and definitions The following terms and definitions in GB/T and NB/T are applicable to this Part. 3.1 Reduction of backwall echo caused by the presence of discontinuities BG/BF In time of forging test, ratio of the initial backwall echo BG in the intact area close to defect place and the initial backwall echo BF within the defect place, expressed as db value. 3.2 Grouped discontinuities In time of forging test, there are five or more defect reflection signals within 50 mm acoustic distance at the same time on the display screening line, or five or more defect reflection signals within the same depth scope were found on the inspection surface of 50 mm 50 mm, and the reflection amplitude are greater than or equal to defect of an equivalent flat bottom hole diameter. 3.3 Reference sensitivity It refers to sensitivity when height of reference block artificial reflection echo or height of inspected work piece bottom are adjusted to a certain reference. 3.4 Scanning sensitivity Based on reference sensitivity, db value (increment) shall be properly improved in accordance with surface condition, testing defect requirements and probe types to conduct sensitivity of actual detection. 3.5 Through thickness dimension of the flaw Page 9 of 180

8 pulse voltage, pulse rise time and firing pulse width (using square wave pulse impact as firing pulse), receiving circuit band and other main performance parameters in product quality certification of ultrasonic testing instrument the probe shall provide center frequency, bandwidth, impedance or static capacitance, relative pulse echo sensitivity and Angle probe beam performance (including probe frontier distance (shot point), Value K (refraction Angle β) and other major parameters Test instrument, probe and combined performance Testing instruments Use A type pulse reflection ultrasonic detector, and the working frequency shall include at least frequency range of 0.5 MHz ~ 10 MHz based on -3 db measurement, test conditions and parameters of each performance in the ultrasonic instrument shall meet the requirements of annex A and provide certification documents. The test method shall be based on provisions in GB/T Probe Circular wafer shall not be greater than 40 mm in diameter, and either side length of square chip shall not be more than 40 mm in general. The performance indicators shall meet the requirements of annex B and provide certification documents. The test method shall be based on provisions in GB/T Combined performance of instrument and probe Combined performance of instrument and probe includes horizontal linear, vertical linear, combined frequency, margin sensitivity, blind area (only limited to straight probe) and far field resolution It shall measure combined performance of instrument and probe in the following cases: a) Newly purchased ultrasonic testing instrument and (or) probe; b) After instrument and probe are repaired or have major components replaced; c) When inspectors doubted The horizontal linear deviation is not more than 1 %, and vertical linear deviation is not more than 5 % The deviation between combined frequency of instrument and probe and nominal frequency of probe shall not be more than plus or minus 10 % Combined performance of instrument and straight probe shall meet the following requirements: Page 11 of 180

9 signals produced by the known reflector, namely test block used for inspection Overall dimensions of reference block shall be able to represent features of inspected work piece, and thickness of test block shall be corresponding to thickness of inspected work piece. If it involved inspection of butt joint with different thickness, the selection of the test block thickness shall be determined by thickness of the larger one The reference block shall be made by materials with same or similar acoustic performance as the inspected materials. When straight probe is used for detection, it is not allowed having defects with flat bottom quantity diameter greater than or equal to Φ2 mm The shape, size and quantity of reference block artificial reflector used for different inspected work piece ultrasonic inspection shall comply with the provisions in relevant sections of this Part When it clearly requires size accuracy of reference block in this part, it shall provide related evidence document, and it shall refer to provisions in JB/T 8428 without clear requirements Coupling agent Sound permeability of coupling agent shall be better and not damage detection surface detection, such as machine oil, chemical paste, glycerin and water etc Control on content of coupling agent contaminants Adding content of coupling agent shall not be greater than 250 mg/l if used on nickel-based alloy The total halogen (chlorine and fluorine) of coupling agent shall not be greater than 250 mg/l if used on austenite stainless steel or titanium Calibration, verification, operation review and check requirements for ultrasonic testing equipment and instrument Calibration, verification and operation review shall be conducted on reference test block. The main beam of the probe shall vertically align to reflector s reflective surface to obtain stable and the largest reflected signal Calibration or verification It shall at least calibrate horizontal linear, vertical linear, combined frequency, blind area (only limited to straight probe), margin sensitivity and resolution in combined performance of the ultrasonic instrument and probe as well as attenuator precision of the instrument once a year, and record. Test is required to meet provisions in Page 13 of 180

10 fully tested Surface quality of weld shall be qualified through appearance check. It shall remove all paint, dirt and rust, splash and contaminants to influence test on test surface (area passing probe), and its surface roughness shall conform to the requirements of the test. The irregular state on the surface shall not affect the validity of test results Scanning coverage In order to ensure ultrasonic sound beam can scan the overall tested area of work piece while testing, every scanning coverage of the probe shall be greater than probe diameter or 15 % of the width or it shall give priority to satisfy the demands of test coverage requirements in related chapters Movement speed of the probe Probe scanning speed shall not exceed 150 mm per second commonly. When automatic alarm device is used for scanning, the scanning speed shall be based on the reference test to determine Scanning sensitivity Setting of scanning sensitivity shall comply with the provisions in the relevant chapter Sensitivity compensation a) Coupling compensation: in time of testing and defect quantitative, compensation shall be made to coupling loss caused by difference between reference block and surface roughness of tested work piece; b) Attenuation compensation: in time of testing and defect quantitative, compensation shall be made to sensitivity decline and defect quantitative error caused by difference between reference block and material attenuation of tested work piece; c) Hook face compensation: in time of testing and defect quantitative, for work piece with hook tested face, compensation shall be made to coupling loss caused by difference between work piece and radius of reference block curvature Review of instrument and probe system Review shall be carried out to the system in the following cases: a) When there are changes in probe, coupling agent and instrument regulation; b) When it is suspected that scanning range or scanning sensitivity have changes; Page 16 of 180

11 sensitivity, and the center point of the probe is the boundary point of the defect; c) When plate thickness is greater than 20 mm to 60 mm, move the probe to make defect wave decline to distance - wave amplitude, and the center point of the probe is the boundary point of the defect; d) When boundary range of defect is determined in b), move the probe to make the first bottom face reflection wave lift to 50 % of full scale of fluorescent screen under standard sensitivity or lift to distance - wave amplitude. For this case, the center point of the probe is the boundary point of the defect Defect quantitative when single wafer straight probe is used for testing: Single wafer straight probe shall be used to make defect quantitative based on method in c), d) and e), and it shall also record the defect reflection amplitude or equivalent flat bottom hole diameter Evaluation method of defect size Evaluation rules on defect indicated length Rectangular frame parallel to plate rolling direction shall surround the defects, and its side length shall be taken as indicated length of this defect Evaluation rules on indicated area of single defect a) A defect shall accord with its indicated rectangular area as single indicated area of this defect; b) When adjacent spacing among many defects are lower than indicated length of small defect nearby, it shall deal with in accordance with single defect, and the defect indicated area is the sum of each defect area Plate quality grading See table 6 and table 7 for plate quality grading, and table 6 and table 7 shall be applied separately when quality grading is carried out specifically In the process of testing, testing personnel shall evaluate Grade V if there are white spots, crack and other defects are found in the plate In the central testing area of the plate, the quality grading shall be determined in accordance with the maximum allowed single defect indicated area and the maximum allowed defect quantity within any testing area of 1 m 1 m. If the testing area is lower than 1 m 1 m within the center of the whole plate, the maximum allowed defect quantity can be converted based on proportion. Page 23 of 180

12 The probe shall be placed to full combined position of the composite plate, and the first regulated bottom echo height is 80 % of full scale of fluorescent screen. This shall be taken as standard sensitivity The scanning sensitivity is generally 6 db higher than standard sensitivity Testing Coupling method can use direct contact method or immersion method Scanning way a) It shall perform 100 % scanning on the edge of the composite plate or groove reserved line on both sides, and scanning width is shown in table 5. b) It shall perform scanning in the region of the central composite plate, probe along the direction perpendicular to the plate rolling, and parallel line with distance not more than 50 mm, or the probe along the vertical and parallel plate rolling direction and grid line with distance not more than 100 mm. Scanning diagram is shown in figure 3; c) According to the requirements of contract, technical agreement or drawing pattern, it also can use other forms for scanning; d) When scanning is performed with double wafer straight probe, the moving direction of the probe shall be vertical to its sound insulation layer Measurement of uncombined area When the first bottom echo height is 5 % less than full scale of fluorescent screen, and there are obvious uncombined defect echoes existed (echo height 5 %), this position shall be viewed as uncombined defect area. Move the probe to make the first bottom echo lift to 40 % of full scale of fluorescent screen, at this moment, the probe center point shall be taken as boundary point of uncombined defect area Uncombined evaluation method Evaluation rules on uncombined indicated length When uncombined boundary scope is determined, rectangular frame parallel to plate rolling direction shall surround the uncombined defects, and its side length shall be taken as indicated length of this defect. If single uncombined indicated length is less than 25 mm, it is not required to record Evaluation rules on single uncombined area a) An uncombined shall accord with its indicated rectangular area as this single Page 26 of 180

13 with double wafer straight probe. When testing thickness is more than 45 mm, it is usually performed with single wafer straight probe When thickness of forgings testing direction exceeds 400mm, it shall be tested from both relative end face Probe selection Straight probe Probe nominal frequency shall be in the range of 1 MHz to 5 MHz Wafer area of double wafer straight probe shall not be less than 150 mm 2 ; effective diameter of single wafer straight probe shall be within the rage of Φ10 mm to 40 mm Angle probe The probe shall keep good contact with tested work piece. In the following cases, curve test blocks shall be applied to regulate testing scope and standard sensitivity: a) When scanning is carried out on convex surface vertically (axially), the probe wedge width shall one fifth greater than curvature radius of the tested surface; b) When scanning is carried out on convex surface horizontally (circumferential), the probe wedge length shall one fifth greater than curvature radius of the tested surface; The probe nominal frequency is 2 MHz to 5 MHz mostly, and the probe wafer area is 80 mm 2 to 625 mm Reference block Reference block shall conform to the provisions in Reference block can be made of by one of the following materials: a) Excessive part of tested material (when the size is sufficient); b) Material with same steel type and heat treatment status as the tested material; c) Material with same or similar acoustic features as the tested material Reference block of single wafer straight probe Single wafer straight probe shall use CS-2 test block to regulate standard sensitivity, and its shape and size shall conform to provisions in figure 4 and table 9. It can also Page 28 of 180

14 Coupling way can generally adopt direct contact method Sensitivity compensation Coupling compensation, attenuation compensation and surface compensation shall be conducted in accordance with actual situation in time of testing The determination of work piece material attenuation coefficient a) In the area where the work piece are in good condition without defect, choose three representative where tested surfaces is parallel to the bottom surface, adjust the instrument to make the first bottom echo amplitude (B 1 ) or the Nth time bottom echo amplitude (B n ) to be 50 % of full scale, record instrument gain or attenuator readings at this time, readjust the instrument gain or attenuator to make the second bottom echo amplitude or the mth time bottom echo amplitude (B 2 or B m ) to be 50 % of full scale, and the reading difference between the two gains or attenuator readings is (B 1 - B 2 ) or (B n - B m ) (not considering bottom reflection loss). b) When base material nominal thickness is 3 times less than near-field zone of probe (t < 3N), the attenuation coefficient (meeting t < 3N/t, m < n) shall be calculated based on formula (1): where: α = [(B n - B m ) - 201g(m/n)]/2 (m - n)t (1) α - attenuation coefficient, db/m (single travel); (B n - B m ) - reading difference between the two gains or attenuator readings, db; t - tested thickness of the work piece, m; N - near-field zone length of single wafer straight probe, m; m, n - times of bottom reflection. c) When base material nominal thickness is greater than or equal to 3 times of nearfield zone of probe (t 3N), the attenuation coefficient shall be calculated based on formula (2): where: α = [(B 1 - B 2 ) - 6]/2t..... (2) (B 1 - B 2 ) - reading difference between the two gains or attenuator readings, db; And other symbols have the same meaning as b). Page 32 of 180

15 d) The average value of three attenuation coefficients on the work piece is attenuation coefficient of this work piece Scanning method Testing with straight probe a) It shall perform 100 % scanning by moving probe from two mutual vertical direction on the tested surface. The main testing direction is shown in figure 7; b) When scanning is made by double wafer straight probe, the moving direction of the probe shall be perpendicular to its sound isolation layer. c) According to the requirements of contract, technical agreement or drawing pattern, it also can use other forms for scanning, such as parallel line or grid line scanning with certain intervals Testing with angle probe Testing with angle probe shall be according to requirements of Annex E Determination of defect equivalent When depth of tested defect is greater than or equal to 3 times of near-field zone of probe, it can use AVG curve calculation method to determine the defect equivalent. For defect with 3 times of near-field zone, it can apply distance - amplitude curve to determine the defect equivalent. It can also adopt other equivalent method to determine. Page 33 of 180

16 ~ ~ ~ ~ ~ ~ ~ Determination of standard sensitivity of double wafer straight probe When axial testing, use CS-2 test block to test a group of flat bottom hole of Φ2 mm with different testing depth in order (at least three) based on testing range, draw distance - amplitude curve of double wafer straight probe, and take it as standard sensitivity. When radial testing, use CS-3 test block or test block as shown in figure 8 to test a group of flat bottom hole of Φ2 mm with different testing depth in order (at least three) based on testing range or curve radius, draw distance - amplitude curve of double wafer straight probe, and take it as standard sensitivity The scanning sensitivity is generally 6 db higher than standard sensitivity Testing Coupling method Coupling way can generally adopt direct contact method Sensitivity compensation Coupling compensation, attenuation compensation and surface compensation shall be conducted in accordance with actual situation in time of testing Scanning method Radial testing shall be performed with scanning according to the spiral line or along the circumference, the travel shall be overlapping, and scanning surface shall include the whole cylindrical surface Axial testing be performed with scanning from both ends of bolt billet, to avoid edge effect influencing testing result as much as possible Determination of defect equivalent Distance-amplitude curve is generally adopted to determine defect equivalent Quality grading See table 13 for quality grading of single defect. Page 37 of 180

17 All tested areas of the forgings shall be performed with testing from two vertical direction mutually as much as possible, and the tested distance shall be half of the thickness When disk-shaped or pie-shaped forgings are tested, straight probe shall be used to conduct testing from at least one flat surface, and scanning shall be carried out from circumference surface if possible When cylinder forgings are tested, for cylinder forgings or annular forgings, testing can be conducted from the whole external surface (side face or circumference surface) with straight probe. When the ratio of length and diameter exceeds 6 or the axial length is more than 600 mm, straight probe shall be used to conduct axial testing from both end surface on the largest scope as possible. If testing on both ends fails to exceed half of the length due to attenuation and other causes, the straight probe can be replaced by angle probe to conduct axial testing Testing with angle probe Testing for austenite steel forgings with angle probe shall be conducted in accordance with requirements of Annex F Defect record Because there are defects, the bottom wave under standard sensitivity will be decreased to a position below 25 % of full scale Defect amplitude is at a position above distance-amplitude curve Quality grading Please see table 16 for quality grading for single wafer straight probe or double wafer straight probe Please see table 17 for quality grading for testing with angle probe When quality is graded specifically, table 16 and table 17 shall be used separately. Table Quality grading of testing with straight probe Unit: mm Base material nominal thickness 80 > 80 ~ 200 > 200 ~ 300 > 300 > 600 Quality grade I II I II I II I II I II Defect equivalent flat bottom hole diameter or > > Φ3 > Φ3 Φ6 > Φ6 amplitude after bottom Φ10 Φ10 Φ13 Φ13 5 % < 5 % wave decline caused by Page 41 of 180

18 Detection device shall be equipped with high-precision adjusting mechanism for relative steel pipe position of the probe, and can be reliably locked up or can achieve good mechanical trace, to ensure that the beam keep unchanged incidence condition for steel pipe under dynamic situation Transmission device Transmission device shall make the steel tube passing through the detection device with uniform speed and can guarantee the steel pipe and the detection device has good concentricity during detection Separation device Separation device shall reliably detect qualified and unqualified steel pipes separately Reference blocks Reference blocks shall be manufactured by choosing steel pipes with same specification as the tested steel pipe, and same or similar material, heat treatment process and surface status as the tested pipe. The length of the reference block shall meet requirements of testing method and detection equipment Artificial reflector The shape of artificial reflector Artificial reflector used for testing longitudinal and transverse defects shall be longitudinal groove parallel to the pipe axis and transverse groove vertical to the pipe axis respectively. Both cross section shape can be rectangular or V-shaped. See figure 10 for diagram of artificial reflector. Two side faces in the rectangular groove shall be parallel to and vertical to the groove bottom mutually. When the electric erosion method is used for processing, it is allowed the bottom and the bottom corner of the groove to be circular slightly. Angle of V-shaped groove shall be 60 degree. Both parties of supply and demand shall negotiate to select shape of artificial reflector during testing Position of artificial reflector A longitudinal groove shall be processed to the external surface in the center of reference block or internal and external surface of end region. Nominal size of three grooves are the same. When the inner diameter of the steel pipe is less than 25 mm, inner wall longitudinal groove cannot be processed. A transverse groove shall be processed to the external surface in the center of sample or internal and external surface of end region. Nominal size of three grooves are the same. When the inner diameter of the steel pipe is less than 50mm, inner wall transverse groove cannot be processed. Page 43 of 180

19 b) In time of adjustment, rotate the pipe with proper speed on one side, and slowly tilt the probe s center on other side to make echo amplitude generated from inner and outer surface artificial reflector of the reference block up to 50 % of full scale of fluorescent screen, and take it as standard sensitivity; c) When the internal and external wall artificial reflector signal use the same alarm gate, the alarm sensitivity of the detector shall be set up in accordance with the lower amplitude signal between signals of the internal and external wall and circumferential signals at different locations. When the internal and external wall artificial reflector signal use different alarm gates, the alarm sensitivity of the detector shall be set up in accordance with the lower amplitude signal of circumferential signals at different locations. At the same time, the width of both gates shall meet alarm requirements for defect signals at each position inside the pipe wall The scanning sensitivity is generally 6 db higher than standard sensitivity Testing Testing of steel pipe can be conducted with immersion method or direct contact method in accordance with specification of the steel pipe When test block is used to regulate testing, coupling difference between test block and tested surface of steel pipe shall be considered Angle probe is used for testing under status when the probe and steel probe is moving relatively. In time of automatic or manual testing, it shall ensure sound beam can scan all surface of the steel pipe. In time of automatic testing, it cannot conduct effective testing for both ends of the steel pipe, and this area is viewed as blink area of automatic testing. It shall adopt effective method to test this area, such as manual method When longitudinal defect is tested, the sound beam shall be spread along with circumferential direction (see figure 11); when transverse defect is tested, the sound beam shall be spread along with axial direction (see figure 12). Testing of longitudinal and transverse defect shall be conducted on opposite direction of the steel pipe. Page 46 of 180

20 Ultrasonic testing when welded joint for pressure equipment is manufactured and installed, shall generally adopt Grade B ultrasonic testing technology to conduct testing. Welded joint for important equipment can adopt Grade C ultrasonic testing technology to conduct testing General requirements of different testing technology grade See Annex N for specific requirements for ultrasonic testing with different types of welded joint Grade A testing Grade A is applicable to testing welded joint with base material nominal thickness of 6 mm to 40 mm. A kind of refraction angle (value K) probe can use direct wave method and primary reflection wave method to make testing on single and double side of welded joint. If condition limited, it can choose to test single side of double face or single side of single face. It does not require for testing of transverse defect in general Grade B testing a) Grade B is applicable to testing welded joint with base material nominal thickness of 6 mm to 200 mm; b) The welded joint would conduct testing for transverse defect in general; c) For welded joint which shall conduct testing for double side of double face in accordance with requirements in Annex N, it shall add angle probe to conduct testing for near-surface defect if geometry condition limited or testing for double side of single face is selected due to existence of weld cladding layer (or composite layer) Grade C testing a) Grade C is applicable to testing welded joint with base material nominal thickness of 6 mm to 500 mm; b) The excess weld metal of welded joint shall be rubbed down when Grade C is used for testing. For parent material area scanning by angle probe of welded joint, straight probe shall be used for testing, and the testing method shall be performed in accordance with provisions in c) Welded joint with base material nominal thickness greater than 15mm shall conduct testing for double sides of double face, and t shall add angle probe to conduct testing for near-surface defect if geometry condition limited or testing for double side of single face is selected due to existence of weld cladding layer (or composite layer); Page 52 of 180

21 d) For weld seam with narrow clearance whose groove angle is lower than 5 degree, if shall add effective method to testing and groove surface parallel defect if possible; e) For butt joint with base material nominal thickness greater than 40 mm, it shall add testing made by straight probe; f) Welded joint shall conduct testing for transverse defect When two or more kinds of different refraction (value K) angle probe are used for testing, the refraction angle difference between probes shall not be smaller than 10 degree Test block Standard test block Preparation of standard test block shall comply with provisions in The standard test block used in this article is CSK-IA. And its shape and size shall comply with the provisions in figure 13 respectively Reference blocks Preparation of reference block shall comply with provisions in The reference block used in this article is CSK-IIA, CSK-IIIA and CSK-IVA: a) The shape and size of CSK-IIA test block shall comply with the provisions in table 23 and figure 14; b) See Annex O for the shape and size of CSK-IIIA; c) The shape and size of CSK-IVA test block shall comply with the provisions in table 24 and figure 15; d) When requirements for standard sensitivity is met, artificial reflector on the test block can adopt other arrangement form or add in accordance with testing demands, and can use equivalent test blocks in other forms Use principle of test block CSK-IA, CSK-IIA, CSK-IIIA and CSK-IVA test blocks are applicable to ultrasonic testing for welded joint with tested surface curvature radius greater than or equal to 250 mm CSK-IA, CSK-IIA, CSK-IIIA and CSK-IVA test blocks are applicable to ultrasonic testing for welded joint with work piece wall thickness of 6 mm to 500 mm, Page 53 of 180

22 or P = 2t tan β (4) where: P - crossing distance, mm; t - base material nominal thickness, mm; K - tangent value of probe refraction angle; β - probe refraction angle, ( ) When direct method is used for testing, probe moving zone width shall be greater than or equal to 0.75P The tested surfaces shall be removed from paint, welding spatter, iron, oil dirt and other foreign matters, lest affect acoustic coupling and defect judgment. The tested surface shall be smooth. The clearance between tested surface and probe wedge bottom or protective film shall not be greater than 0.5 mm, and its surface roughness (value R a ) shall be smaller or equal to 25 μm. The tested surface shall be polished. The excess weld metal shall be polished parallel to the parent material. Reserve weld seam with excess weld metal, if the surface of weld seam has bite edge, larger uplift and depression, it shall be properly ground, and rounded off so as not to affect the test results evaluation Probe refraction angle (value K), nominal frequency Refraction of angle probe (value K), and nominal frequency can be selected in accordance with provisions in table 25. When condition allowed, it shall try to use probe with larger refraction angle (value K) When first reflection method is used for testing, the selection of refraction of angle probe (value K) shall make the interaction angle of main sound beam and bottom normal opposite to the tested surface between 35 to 70 degree. When two or more refraction of angle probe (value K) are used for testing, one refraction of angle probe (value K) shall meet this requirement at least. Table Refraction of angle probe (value K) and nominal frequency recommended for use Base material nominal Refraction angle (value K) Nominal frequency/mhz thickness t/mm 6 ~ o ~ 75 o (2.0 ~ 3.0) 4 ~ 5 > 25 ~ o ~ 68 o (1.5 ~ 2.5) 2 ~ 5 > o ~ 63 o (1.0 ~ 2.0) 2 ~ Page 62 of 180

23 where: b - test block width, mm; λ - length of ultrasonic wave, mm; S - sound travel, mm; D o - effective diameter of sound source, mm Testing of curvature surface longitudinal butt joint Curvature radius of work piece tested surface shall be within the range of 0.9 to 1.1 times of curvature radius of reference block Refraction angle (value K) of the probe shall be selected based on curvature of work piece and base material nominal thickness and the limitation of geometric critical angle shall be considered to ensure sound beam can scan the whole welded joint After the probe contact surface is polished, attention shall be paid to changes in incidence point and refraction angle (value K) of the probe, and actual measurement shall be made with curvature reference block Note defect depth indicated on the display screen or actual radial buried distance between horizontal distance and defects or difference of horizontal distance arc length, and modify See Annex J for ultrasonic testing method for curvature longitudinal butt joint Testing for curvature circular butt joint Curvature radius of work piece tested surface shall be within the range of 0.9 to 1.1 times of curvature radius of reference block See Annex K for ultrasonic testing method for curvature circular butt joint See Annex L for ultrasonic testing method for connecting pipe and cylinder (or end socket) fillet joint See Annex for ultrasonic testing method for T-shaped welded joint Defect quantitative Page 67 of 180

24 For defect whose amplitude reaches or exceeds assessment curve, it shall determine its location, amplitude and indicated length etc Defect amplitude Move the probe to obtain the maximum reflection amplitude of defect, and this is the defect amplitude When probe with different refraction angle (value K) are used to test the same defect from different tested surface (side), the maximum amplitude obtained is the defect amplitude Defect position Defect position shall be subject to location where the maximum amplitude obtained Indicated defect length When defect reflection wave only has one high point, and is located at Zone II or above Zone II, -6 db method shall be used to measure its length When the defect reflection wave peaks are fluctuated with changes, have more than one high points, and are located at Zone II or above Zone II, the endpoint - 6 db method shall be used to measure its length When the maximum defect reflection amplitude is located at the Zone I, move the probe from right to left to make the amplitude dropped to assessment curve, so that the assessment curve with absolute sensitivity method can be used to measure the indicated length of defects Defect assessment For signals exceeding the assessment curve, attention shall be paid whether there are crack, incomplete fusion, incomplete penetration and other defects. If there is any doubt, judgment shall be made by changing the probe refraction angle (value K), adding tested surface, observing dynamic waveform and in combination of the structure technology. If it is unable to judge waveform, comprehensive judgment shall be conducted with help of other testing method Two adjacent defects along the length direction, when the space between length directions is shorter than the smaller defect length, and the space between two defects and vertical direction of defect length is lower than 5 mm, it shall be dealt with as one defect, and the sum of the length of two defect shall be taken as the indicated length (the space shall be included into). If the projection of two defects are overlapped in the length direction, the left and right end space of two defects at the length direction shall be taken as its indicated length on the projection. Page 68 of 180

25 Scanning sensitivity shall not be lower than sensitivity of assessment curve Scanning method Scanning shall be conducted to make both sides of butt joint of the probe vertical to the welded joint. The probe moving distance back and forth shall meet requirement. The probe movement from right to left shall make scanning coverage greater than 15 % of probe width In order to observe defect dynamic waveform and distinguish defect signal from pseudo-defect signal, it shall confirm the location, direction and shape of the defect, and it can adopt scanning method as back and forth and from right to left etc Defect quantitative For defects with reflection amplitude locating at Zone I or above Zone I, measurement shall be conducted to defect position, the maximum reflection amplitude of the defect and defect indicated length etc Defect position shall be subject to location where the maximum amplitude obtained The measurement method of the maximum reflection amplitude of the defect is to move the probe to location where the defects appear the maximum reflection wave signals, so as to measure the wave amplitude, and determine its regions in the distance - amplitude curve Measurement of defect indicated length shall be carried out based on the following method: When defect reflection wave only has one high point, and is located at Zone II or above Zone II, 6dB method shall be used to measure its length When the defect reflection wave peaks are fluctuated with changes, have more than one high points, and are located at Zone II or above Zone II, then, the endpoint -6 db method shall be used to measure its length When the maximum defect reflection amplitude is located at the Zone I, move the probe from right to left to make the amplitude dropped to assessment curve, so that the assessment curve with absolute sensitivity method can be used to measure the indicated length of defects The actual indicated length of the defect (l) shall be calculated in accordance with formula (6) (it is applicable to smaller pipe diameter but larger wall thickness): l = L (R - H)/R (6) Page 72 of 180

26 where: L - measured defect indicated length, mm; R - outer diameter of the pipe, mm; H - defect depth, mm Defect assessment For signals exceeding the assessment curve, attention shall be paid whether there are crack, incomplete fusion, incomplete penetration and other defects. If there is any doubt, comprehensive judgment shall be made by changing the probe refraction angle (value K), observing dynamic waveform and combining the welding technology etc When two adjacent defects are on a same straight line, when the space is shorter than the smaller defect length, it shall be dealt with as one defect, and the sum of the length of two defect shall be taken as the indicated length of a single defect (the space shall be included into defect length). 6.5 Quality grading Quality grading for welded joint of boiler and pressure container Welded joint of boiler and pressure container includes cylinder (or end socket) butt joint, connecting pipe and cylinder (or end socket) fillet joint and T-shaped welded joint Welded joint of boiler and pressure container is not allowed to have crack, incomplete fusion and incomplete penetration etc Defect below the assessment curve shall be rated as Grade I Quality grading for welded joint of boiler and pressure container shall be carried out in accordance with table 33. Table Quality grading for welded joint of boiler and pressure container Grade I Unit: mm Base The maximum material Located area allowable value of Allowed indicated length of a nominal of reflection several defect single defect thickness amplitude accumulated length t /L 6 ~ I > Page 73 of 180

27 display changes of measurement situation, such as defects or discontinuities inside the work piece Digital thickness meter is to transfer the sound velocity or time between the initial pulse and the first bottom echo or several bottom echoes into figures and display on the instrument. 7.4 Probe Ultrasonic thickness meter usually adopts direct contact type of single wafer straight probe, and it can also use single wafer straight probe or double single wafer straight probe with deferred block Wall thickness measurement for sample with high temperature (greater than or equal to 60 centigrade degree) or low temperature (below 20 centigrade degree) shall use special probe. 7.5 Calibration block The basic requirement and size of calibration block are shown in figure 25, and it can also use other test blocks to calibrate the instrument under condition of meeting measurement accuracy. 7.6 Coupling agent Coupling agent shall comply with provisions When it is used in high temperature circumstance, it should choose proper hightemperature coupling agent. 7.7 Instrument calibration Instrument calibration shall generally be conducted on a test block which has same or similar sound velocity with the tested material Calibration of digital thickness meter a) Use the ladder block, calibration shall be conducted on test block with thickness close to the maximum value of tested thickness and the minimum value of tested thickness (or 1/2 of the maximum value of tested thickness); b) Place the probe on the thicker test block, and adjust the knob of sound velocity calibration to make the thickness meter displayed reading close to the known value; c) Place the probe on the thinner test block, and adjust the knob of zero position calibration to make the thickness meter displayed reading close to the known Page 77 of 180