JB 4730-1994 Nondestructive Testing of Pressure Vessels
Part 1 General Provisions
1 Subject and Aspects Covered
The standard specifies five nondestructive testing methods and defects classification methods covering ray detection, ultrasonic detection, magnetic particle testing, penetration detection and eddy current testing.
All sorts of nondestructive testing methods specified in the standard are applicable to raw material, spare parts and welding seam of metallic pressure vessel.
2 Normative References
GB 150 Steel Pressure Vessels
GB 3721 Magnetic Particle Inspection Machine
GB 5097 Non-destructive Testing-Guidelines for Application
GB 5618 Wire Type Image Quality Indicator
GB 9445 Non-destructive Testing-Qualification and Certification of Personnel
GB/T 12604.1-6 Terminology for Nondestructive Testing
JB 4126 Manufacturing and Control and Steel Test Block for Ultrasonic Testing
ZB J04 001 Working Performance Test method for a type Impulse Reflection Supersonic Flaw Detecting System
ZB Y230 General Technical Specifications for a Type Impulse Reflection Ultrasonic Flaw Detector
ZB Y231 Performance Testing Method for Ultrasonic Inspection Probe
ZB Y232 Technical Conditions for No. 1 Reference Block for Ultrasonic Inspection
ZB Y344 Designation Method for Ultrasonic Inspection Probe Type
3. Terms
Besides GB/T 12604.1-6, terms used in the standard should correspond with following specifications:
3.1 A cluster of Defects
Five or more defect reflection signals exist within the scope that fluorescent scanning lines are equivalent to 50 mm sound path; or five or more defect reflection signals are found within same depth range on 50 mm x 50 mm detecting surface. All reflected wave amplitudes are greater than certain specified amplitude of equivalent defect reference reflected wave.
3.2 Loss of Back Reflection Caused by Defects BG/BF (dB)
The ratio of first bottom echo amplitude BG within flawless area near by defect and first bottom echo amplitude BF within defects area, indicated through sound pressure level (dB).
3.3 Detection Cross Chapter
The cross Chapter is adopted as detected object during tandem scanning detection, and usually the welding seam longitudinal Chapter is adopted as the detection cross Chapter. The detection cross Chapter is detailed in Figure 3-1.
3.4 Tandem Reference Line
The reference line adopted for launching and receiving probes moving at equal interval during tandem scanning detection, and the reference line is usually located at the position that is 0.5 times of span away from the detection cross Chapter. The reference line is detailed in Figure 3-1.
Figure 3-1: Detection Cross Chapter and Tandem Reference Line
3.5 Reference Line
The marked line, drawn preliminarily on the base metal detecting surface, certain distance away from welding seam groove. And the base line is adopted to identify the tandem reference line, and it is detailed in Figure 3-2.
3.6 Horizontal Rectangle Tandem Scanning Detection
The mobile scanning detection method that probe incident points of launching and receiving probes group are kept equidistance from the tandem reference line and are parallel to welding seam. This method is detailed in Figure 3-3.
3.7 Longitudinal Rectangle Tandem Scanning Detection
The mobile scanning detection method that probe incident points of launching and receiving probes group are kept equidistance from the tandem reference line and are perpendicular to welding seam. This method is detailed in Figure 3-3.
4 General Requirements
4.1 Selection Principle
4.1.1 The selection, detection time and sampling rate of radiation, ultrasonic, magnetic particle, penetration eddy current testing for pressure vessel should be executed in accordance with requirements and principles of Supervising Rules of Safety Technique for Pressure Vessels, GB 150, GB 5616 and relative technological documents.
4.1.2 For pressure vessels and spare parts made form ferromagnetic material, magnetic particle testing should be adopted to detect surface defect. in case the magnetic particle testing could not be carried out because of reasons such as structural shape, penetration inspection could be adopted.
4.2 Detection Responsibility of Manufacturer
4.2.1 When pressure vessel and spares need detecting in accordance with the standard, manufacturer and assembly department should establish nondestructive testing regulations that meet relative specifications in accordance with specifications of this standard. Each detection regulation should be copied at least one copy for reference and using of all non-destructive testing personnel.
4.2.2 Testing routine and result should be correct and sound, and approved and signed by corresponding responsible personality. Storage time of detection record and report should not be less than 7 years. Seven years later, these testing record and report could be delivered to users and stored by users if users require.
4.2.3 Corresponding qualification level and validity period of detection personnel who take detection project should be recorded in detecting files.
4.2.4 Detecting instrument and instrument performance should be inspected periodically, and recorded after qualified inspection.
Figure: 3-2 Reference Line
Figure 3-3: Horizontal Rectangle Scanning and Longitudinal Rectangle Scanning
4.3 Detection Personnel
4.3.1 Personnel who embarks on pressure vessel and spares inspection shall receive technical training, and should be qualified in accordance with labor department document "Rules for Boiler & Pressure Vessel NDT Qualification Examination" and GB 9445.
4.3.2 Nondestructive testing personnel are graded as senior, junior and primary according to technical grade. Personnel at several technical grades who receive deferent nondestructive testing qualifications should only embark on nondestructive testing work corresponding with the grade, and bear corresponding technical responsibility.
4.3.3 Personnel embarking on pressure vessel and spares nondestructive testing shall satisfy following requirements on sight, besides favorable physical quality.
4.3.3.1 Corrected vision shall not be less than 1.0 and inspected yearly.
4.3.3.2 Personnel embarking on magnetic particle and penetration detection shall not have color blindness and partial tritanopia.
4.3.3.3 Personnel embarking on radiographic film should distinguish a group of printed characters which heights are 0.5 mm, spacing interval is 0.5 mm, and are 400 mm away.
4.4 Responsibility of Nondestructive Testing Responsible Personality
4.4.1 Nondestructive testing responsible engineers who participate in pressure vessel and spare manufacturing is responsible to ensure that the standard is implemented correctly in service, and entitled to refuse to handle any detection contents that cannot be carried out in accordance with this standard specifications.
4.4.2 Nondestructive testing responsible engineer should be occupied by personnel who bold boiler and pressure container nondestructive testing advanced or intermediate certificate.
4.5 Acceptance Stamp
If detected contents are pressure vessel product acceptance items, all qualified work-pieces should be marked permanently or semi-permanently, and marks should strike the eye. If products are not suitable to be marked, detailed detection sketch or others effective markings enable detection personnel at next procedure or last detection to distinguish marks.
Part 2 Welding Seam Radiation Trans-illumination Detection
5 General Requirements
5.1 Detection Range
This Chapter specifies procedure and requirement that shall be abided by in welding seam trans-illumination detection procedure to obtain eligible trans-illumination film.
This Chapter is applicable to radiation trans-illumination detection for welding seam of carbon steel, low alloy steel, stainless steel, aluminum and aluminum alloy, iron and iron alloy pressure vessel, and steel pipe mating ring seam.
5.2 Safety Protection
5.2.1 X-ray and y ray are harmful to body health, so detection staff should avoid direct radiation and scattered ray radiation as much as possible.
5.2.2 Personnel embarking on radiation detection should be equipped with radiation instruments or radiation detecting instruments to detect the radiation exposure volume of work environment and the accumulated radiation exposure volume of individual. During y ray detection operation, the ray dose near by working space and y ray source container each time to locate the radiation source position, and avoid accident radiation.
5.2.3 The safety line should be emplaced in site radiation detection. Warning signs should be available on the safety line, and red light should be emplaced at night.
5.2.4 The max allowable radiation exposure volume that detection personnel receive annually is 5x10-2 Sv, and for non-detection staff, the max allowable radiation exposure volume is 5x10-3 Sv.
5.3 Detection Personnel
Detection Personnel should correspond with relative regulations of 4.3.
Part 1 General Provisions 1 Subject and Aspects Covered 2 Normative References 3 Terms 3.1 A cluster of Defects 3.2 Loss of Back Reflection Caused by Defects BG/BF (dB) 3.3 Detection Cross Chapter 3.4 Tandem Reference Line 3.5 Reference Line 3.6 Horizontal Rectangle Tandem Scanning Detection 3.7 Longitudinal Rectangle Tandem Scanning Detection 4 General Requirements 4.1 Selection Principle 4.2 Detection Responsibility of Manufacturer 4.3 Detection Personnel 4.4 Responsibility of Nondestructive Testing Responsible Personality 4.5 Acceptance Stamp Part 2 Welding Seam Radiation Trans-illumination Detection 5 General Requirements 5.1 Detection Range 5.2 Safety Protection 5.3 Detection Personnel 5.4 Radiation Trans-illumination Equivalent Coefficient 5.5 Trans-illumination Mode 5.6 Surface Requirement 5.7 Location Marking and Identification Marking 5.8 Image Quality Indicator 5.9 Radiation Transillumination Quality Grade 5.10 Film and Intensifying Screen 5.11 Geometrical Condition 5.12 Selection of Ray Energy 5.13 Shielding of Useless Radiation and Scattered Ray 5.14 Exposure 5.15 Film Treatment 5.16 Film Quality 5.17 Film Observation 5.18 Report and Acceptance Stamp 6 Welding Seam Radiation Transillumination Defect Grade Estimation 6.1 Transillumination Defect Grade Estimation for Steel Pressure Vessel Butt-jointed Seam 6.2 Steel Pipe Circumferential Seam Transillumination Defect Grade Estimation 6.3 Grade Estimation for Aluminium Pressure Tight Seam Transillumination Defect 6.4 Grade Estimation for Titanium Pressure Tight Seam Transillumination Defect Part 3 Ultrasonic Detection 7 General Requirements 7.1 Detection Range 7.2 Detection Personnel 7.3 Defectoscope, Probe and System Performance 7.4 General Method of Ultrasonic Detection 7.5 Calibration 7.6 Test Block 7.7 Report and Acceptance Stamp 8 Ultrasonic Detection for Pressure Vessel Raw Material and Spare 8.1 Pressure Vessel Steel Plate Ultrasonic Detection 8.2 Ultrasonic Detection for Pressure Vessel Forgings 8.3 Ultrasonic Detection for Pressure Vessel Clad Steel Plate 8.4 Ultrasonic Detection for Steel High Pressure Seamless Pipe 8.5 Ultrasonic Detection for High-voltage Screw Bolt 8.6 Ultrasonic Detection for Pressure Vessel Austenitic Steel Forging 9 Ultrasonic Detection for Pressure Vessel Welding Seam 9.1 Ultrasonic Detection for Steel Pressure Vessel Welding Seam 9.2 Ultrasonic Detection for Stainless Steel Overlay 9.3 Ultrasonic Detection for Aluminum Pressure Vessel Welding Seam 10 Ultrasonic Measurements for Pressure Vessel Thickness 10.1 Measurement Range 10.2 Acoustic Speed Scope of Primary Materials 10.3 Instrument and Probe 10.4 Adjustment Test Block 10.5 Couplant 10.6 Instrumental Correction 10.7 Measurement Preparation 10.8 Measuring Method 10.9 Disposal to Abnormity of Measured Value 10.10 Report Part 4 Surface Detection 11 Magnetic Particle Testing 11.1 Detection Scope and General Requirement 11.2 Testing Personnel 11.3 Equipment and Magnetic Particle 11.4 Magnetization Method 11.5 Electric Current Mode and Selection 11.6 Surface Preparation 11.7 Measuring Occasion 11.8 Magnetization Specifications 11.9 Magnetic Particle Application 11.10 Demagnetization 11.11 Magnetic Mark Evaluation and Record 11.12 Rechecking 11.13 Defect Grade Estimation 11.14 Report 12 Penetrance Testing 12.1 Testing Scope and General Requirements 12.2 Detection Personnel 12.3 General Requirements 12.4 Classification and Selection of Penetrance Testing 12.5 Operating 12.6 Classification for Defect Displaying Marks 12.7 Defect Displaying Mark Grade Estimation 12.8 Report 13 Eddy Current Testing for Pipe workpiece 13.1 Detection Range and General Requirements 13.2 Testing Personnel 13.3 Testing Equipment 13.4 Standard Sample 13.5 Testing Condition and Procedure 13.6 Defect Grade Estimation 13.7 Report Appendix A Appendix B Appendix C Appendix D Appendix E Appendix F Appendix G Appendix H Appendix I Appendix J Appendix K Appendix L Appendix M Appendix N Appendix O Appendix P Appendix Q Appendix R Additional Explanation
