Welding Processes, Inspection, and Metallurgy

API RECOMMENDED PRACTICE 577 THIRD EDITION, OCTOBER 2020

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Foreword

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Contents

Page

1. Scope 1

2. Normative References 1

3. Terms, Definitions, and Acronyms 3

   1. Terms and Definitions 3

   2. Acronyms 12

4. Welding Processes 12

   1. General 12

   2. Shielded Metal Arc Welding (SMAW) 12

   3. Gas Tungsten Arc Welding (GTAW) 15

   4. Gas Metal Arc Welding (GMAW) 18

   5. Flux-Cored Arc Welding (FCAW) 21

   6. Submerged Arc Welding (SAW) 24

   7. Stud Arc Welding (SW) 26

   8. Plasma Arc Welding (PAW) 26

   9. Electrogas Welding (EGW) 28

5. Welding Materials 30

   1. General 30

   2. P-Number Assignment to Base Metals 30

   3. F-Number Assignment to Filler Metals 31

   4. AWS Classification of Filler Metals 31

   5. A-Number 31

   6. Filler Metal Selection 31

   7. Consumable Storage and Handling. 32

6. Welding Procedure 32

   1. General 32

   2. Welding Procedure Specification (WPS). 33

   3. Procedure Qualification Record (PQR) 45

   4. Reviewing the WPS and PQR 45

   5. Tube-to-Tubesheet Welding Procedures 45

7. Welder Qualification 47

   1. General 47

   2. Welders and Welding Operators 47

   3. Examination Failure of a Production Weld 47

   4. Retest for qualification 47

   5. Expiration, Revocation, and Renewal of Welder or Welding Operator Qualification 47

   6. Welder Performance Qualification 47

   7. Reviewing a WPQ 48

   8. Limitations for Welder Qualifications 49

8. Nondestructive Examination 50

   1. Discontinuities/imperfections 50

   2. Materials Identification 54

   3. Visual Examination (VT) 55

   4. Magnetic Particle Examination (MT) 62

   5. Alternating Current Field Measurement 66

   6. Liquid Penetrant Examination (PT) 67

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      Contents

      Page

   7. Eddy Current Examination (ET) 69

   8. Radiographic Examination (RT) 69

   9. Ultrasonic Examination (UT) 83

   10. Hardness Testing 95

   11. Pressure and Leak Testing/Examination (LT) 96

9. Welding Inspection 97

   1. General 97

   2. Tasks Prior to Welding 97

   3. Tasks During Welding Operations. 101

   4. Tasks Upon Completion of Welding 103

   5. Nonconformances and Defects 105

   6. NDE Examiner Certification 105

   7. Weld Inspection Data Recording 106

10. Metallurgy 109

    1. General 109

    2. Structure of Metals and Alloys 109

    3. Physical Properties 111

    4. Mechanical Properties 113

    5. Preheating 116

    6. Heat Treatment 116

    7. Material Test Reports 119

    8. Weldability of Metals 120

    9. Weldability of High Alloys 122

11. Refinery and Petrochemical Plant Welding Issues 124

    1. General 124

    2. Hot Tapping and In-Service Welding 124

    3. Lack of Fusion With GMAW-S Welding Process 127

    4. Caustic Service 128

    5. Controlled Deposition Welding 128

12. Safety Precautions 130

Annex A (normative) Technology and Symbols 131

Annex B (normative) Actions to Address Improperly Made Production Welds 137

Annex C (informative) WPS/PQR Review 139

Annex D (normative) Guide to Common Filler Metal Selection 174

Annex E (informative) Example Report of RT Results 178

Annex F (informative) Inspection Considerations 179

Annex G (informative) Welding Safety 181

Bibliography 182

Figures

1. SMAW Welding Process 13

2. SMAW Welding Electrode Deposition 14

3. GTAW Welding Equipment 16

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   Contents

   Page

4. GTAW Welding Process 17

5. GMAW Equipment 18

6. GMAW Welding Process 19

7. FCAW Equipment 22

8. FCAW Welding Process 23

9. FCAW Welding Process, Self-shielded 23

10. SAW Welding Process 25

11. Comparison of the Gas Tungsten Arc and Plasma Arc Welding Processes 27

12. Electrogas Welding With a Solid Electrode 29

13. Typical Discontinuities Present in a Single Bevel Groove Weld in a Butt Joint 52

14. Direct Visual Examination Requirements 55

15. Inspector’s Kit 58

16. Bridge Cam Gauge 58

17. Adjustable Fillet Weld Gauge 59

18. Skew-T Fillet Weld Gauge 59

19. Weld Fillet Gauge 60

20. Weld Fillet Gauge 60

21. Weld Size Gauge 61

22. Hi-Lo Gauge 61

23. Surface-Breaking Discontinuity 62

24. Subsurface Discontinuity 62

25. Weld Discontinuity 64

26. Flux Lines 64

27. Detecting Discontinuities Transverse to Weld 65

28. Detecting Discontinuities Parallel to the Weld 65

29. Pie Gauge 66

30. Fluorescent Penetrant Technique 68

31. IQI Common Hole Diameters 71

32. IQI 72

33. Single-Wall Techniques 74

34. Double-Wall Techniques 74

35. Incomplete or Lack of Penetration (LOP) 77

36. Interpass Slag Inclusions 77

37. Cluster Porosity 78

38. Lack of Side Wall Fusion 78

39. Elongated Slag (Wagon Tracks) 79

40. Burn-Through 79

41. Offset or Mismatch With Lack of Penetration (LOP) 80

42. Excessive Penetration (Icicles, Drop-Through) 80

43. Internal (Root) Undercut 81

44. Transverse Crack 81

45. Tungsten Inclusions 82

46. Root Pass Aligned Porosity 82

47. A-Scan 84

48. B-Scan 84

49. C-Scan 85

50. D-Scan 86

51. S-Scan 87

52. TOFD D-Scan Display 88

    Contents

    Page

53. TOFD B-Scan 89

54. TOFD Transducer Arrangement and Ultrasonic Energy Beam Propagation 89

55. DAC Curve for a Specified Reference Reflector 92

56. DAC Curve for an Unknown Reflector. 92

57. Location of Hardness Measurements 96

1. Joint Types and Applicable Welds 132

2. Symbols for Various Weld Joints 133

3. Supplementary Symbols for Welds 133

4. Standard Weld Symbols 134

5. Groove Weld Nomenclature 135

6. SMAW Welding Electrode Identification System 135

7. GMAW/GTAW/PAW Welding Electrode Identification System 135

8. FCAW Welding Electrode Identification System 136

9. SAW Welding Electrode Identification System 136

10. EGW Welding Electrode Identification System 136

1. Suggested Actions for Welds Made by an Incorrect Welder 137

2. Steps to Address Production Welds Made by an Improper Welding Procedure 138

Tables

1. P-Number Assignments 31

2. Common Types of Discontinuities 51

3. Commonly Used NDE Methods 52

4. Capability of the Applicable Examination Method for Weld-Type Joints 53

5. Capability of the Applicable Method vs. Discontinuity 53

6. Discontinuities Commonly Encountered with Welding Processes 54

7. ASTM E94 IQIs 71

8. Conditions That May Exist in a Material or Product 108

9. Results of Nondestructive Examination 108

10. Results of Application of Acceptance/Rejection Criteria 108

11. Brinell Hardness Limits for Steels in Refining Services 118

12. Weld Crack Tests 122

13. Hot Tapping/In-Service Welding Hazards Associated With Some Particular Substances 126

1. Common Welding Consumables for SMAW of Carbon and Low-Alloy Steel 174

2. Common Welding Consumables for SMAW of Carbon and Low-Alloy Steel 175

3. Copper-Nickel and Nickel-Based Alloys 176

4. Classification Changes in Low-Alloy Filler Metal Designations 177

Welding Processes, Inspection, and Metallurgy

1. Scope

   
   

   This recommended practice (RP) provides guidance to the API authorized inspector on welding inspection as encountered with fabrication and repair of refinery and chemical plant equipment and piping, pipelines, and other related industries. This RP includes descriptions of common welding processes, welding procedures, welder qualifications, metallurgical effects from welding, and inspection techniques to aid the inspector in fulfilling their role implementing API 510, API 570, API 653, and API 582. The level of learning and training obtained from this document is not a replacement for the training and experience required to be a certified welding inspector under one of the established welding certification programs, such as the American Welding Society (AWS) Certified Welding Inspector (CWI), or Canadian and European equivalent schemes such as CWB, CSWIP, PCN, or EFW.

   
   

   This RP does not require all welds to be inspected, nor does it require welds to be inspected to specific techniques and extent. Welds selected for inspection, and the appropriate inspection techniques, should be determined by the welding inspectors, engineers, or other responsible personnel using the applicable code or standard. The importance, difficulty, and problems that could be encountered during welding should be considered by all involved. A welding engineer should be consulted on any critical, specialized, or complex welding issues.

   
   

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.

API 510, Pressure Vessel Inspection Code: Maintenance, Inspection, Rating, Repair, and Alteration

API 570, Piping Inspection Code: Inspection, Repair, Alteration, and Rerating of In-Service Piping Systems API Recommended Practice 571, Damage Mechanisms Affecting Fixed Equipment in the Refining Industry API Recommended Practice 574, Inspection Practices for Piping System Components

API Recommended Practice 578, Material Verification Program for New and Existing Alloy Piping Systems

API Recommended Practice 582, Recommended Practice and Supplementary Welding Guidelines for the Chemical, Oil, and Gas Industries

API Recommended Practice 2201, Procedures for Welding or Hot Tapping on Equipment in Service

ASME Boiler and Pressure Vessel Code 1

Section VIII, Rules for Construction of Pressure Vessels

1 ASME International, 3 Park Avenue, New York, New York 10016-5990, www.asme.org.