Inspection Practices for Pressure Vessels

API RECOMMENDED PRACTICE 572 FOURTH EDITION, DECEMBER 2016

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Copyright © 2016 American Petroleum Institute

Foreword

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1. Scope 1

2. Normative References 1

3. Terms and Definitions 1

   1. Definitions 1

   2. Acronyms and Abbreviations 6

4. Introduction to Pressure Vessels 6

   1. General 6

   2. Methods of Construction 6

   3. Materials of Construction 7

   4. Internal Components and Equipment 8

   5. Uses of Pressure Vessels 11

   6. Design and Construction Standards 12

5. Reasons for Inspection 15

   1. General 15

   2. Safety 15

   3. Reliability and Efficient Operation 16

   4. Regulatory Requirements 16

6. Inspection Plans 17

   1. General 17

   2. Inspection for Specific Types of Damage 17

   3. Developing Inspection Plans 18

   4. Reviewing and Updating Inspection Plans 18

   5. RBI 19

7. Frequency and Extent of Inspection 19

   1. General 19

   2. Opportunities for Inspection 20

8. Safety Precautions and Preparatory Work 21

   1. Safety Precautions 21

   2. Preparatory Work 21

9. Inspection Methods and Limitations 24

   1. General 24

   2. Thickness Measurements 24

   3. External Inspection 27

   4. Internal Inspection 36

   5. Special Methods of Detecting Mechanical Damage 48

   6. Metallurgical Changes and In-situ Analysis of Metals 49

   7. Testing 49

10. Condition Assessment and Repair 53

    1. General 53

    2. Visual Inspection 53

    3. Thickness Measurements 54

    4. Remaining Life 54

    5. Methods of Repair 54

    6. Repair of Supporting Vessel Equipment 55

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11. Records and Reports 56

    1. Records 56

    2. Reports 56

Annex A (informative) Exchangers 57

Annex B (informative) Towers 74

Annex C (informative) Sample Record Forms 131

Bibliography 144

Figures

1. Type 3016 Stainless-clad Vessel 8

2. Weld Metal Surfacing 9

3. Strip-lined Vessel 9

4. Principal Strip-lining Methods 10

5. Hex Mesh Installation for Refractory Lining 10

6. Reinforced Refractory 11

7. Vertical Heat Exchanger 12

8. Horizontal Vessel 13

9. Spheres 14

10. Horton Spheroid (Noded) 14

11. Process Tower 15

12. Exchangers 16

13. Exchanger Installation and Foundation 28

14. Severe Deterioration of Anchor Bolts 29

15. Method of Obtaining Vessel Profile Measurements 35

16. Corrosion in Channel 38

17. Crack in Weld Seen by PT 39

18. Hydrogen Blistering 41

19. Self-vented Hydrogen Blisters 41

20. Radiograph of Self-vented Hydrogen Blisters in Carbon Steel 42

21. Catalytic Reactor Internals—Cyclones 43

22. Corrosion Tab Method of Determining Metal Loss on Vessel Linings 45

23. Strip-liner Damage 46

24. Deteriorated Refractory-tile Lining 48

25. Steps in Using Special Equipment to Test Individual Tubes 52

1. Properly Rolled Tube 58

2. Tube-bundle Type of Tank Heater 60

3. Air-cooled Exchangers 61

4. Clean-service Double-pipe Coils 62

5. Tank Suction Heater with Everything but Forward End Enclosed; Shell Suction Nozzle Enclosed in Far End 63

6. Fin-type Tubes in Double-pipe Coil 64

7. Plate-type Exchanger 64

8. Tubes Thinned at Baffles 66

9. Tubes Fretting at Baffles 67

10. Erosion–Corrosion Attack at Tube Ends 67

11. Heat Exchanger Parts 70

12. Heat Exchanger Types 73

1. Typical Trays in a Tower 74

2. Random Packing in a Tower 74

   
   

3. Trays with Downcomers 75

4. Bubble Cap Flow Path 75

5. Tower Stripping and Rectification Section 76

6. Disk/Donut Tray 77

7. Baffle Tray Arrangement 78

8. Figure Tray 79

9. Sieve Tray Distortion 79

10. Typical Trayed Tower 82

11. Float Valves with Two Weights 83

12. Fixed Valves 83

13. Bubble Cap Valves 84

14. Extruded Valves 84

15. New Floating Valve Tray 85

16. Caged Valves 85

17. Typical Packed Tower Drawing 86

18. Random Packing, Pall Rings 87

19. Structured Packing 87

20. Grid-style Packing 88

21. Diagram of Required Scaffolding 90

22. Hexagonal Manways 91

23. Standing Oil and Water 91

24. Trays Collapsed 92

25. Corroded Anchor Bolting 92

26. Corroded Anchor Bolting 93

27. Cracked and Bulged Fireproofing 93

28. Debris in Skirt 94

29. Preliminary Inspection 94

30. Bed Damage at Preliminary Inspection 95

31. Manway Corrosion 95

32. Manway Liner Damage 96

33. Corrosion on Gasket Seating Surface 96

34. Corrosion on Gasket Seating Surface 97

35. Surface Corrosion of Shell 97

36. Inspection from the Bottom Head 98

37. Inspection of Packing via Riser 98

38. Demister Bypass Deposits 99

39. Fouled Demister Pads 99

40. Faulty Demister Installation 100

41. Preferential Corrosion of the Head-to-Shell Weld 100

42. Head Seam Preferential Corrosion 101

43. Preferential Corrosion of the Shell 101

44. Perforation Degradation 102

45. Chimney Tray Deformation at Draw Sump 102

46. Fouled Troughs on Box and Trough Distributor 103

47. Obstructed Pipe Distributor Perforations 103

48. Box and Troughs 104

49. Hit the Washers, Not the Bolts 104

50. Random Packing on Valve Tray 105

51. Bed Limiter Above Random Packing 105

    
    

52. Dislodged Packing 106

53. Damaged Packing Support Grid 106

54. Support Grid from Below 107

55. Corrosion Inside Sightglass Nozzle 107

56. Bottom Head, Vortex Breaker, and Debris 108

57. Fouled Grid-type Packing 109

58. Cracked Plug Weld 109

59. Stainless Steel Donut Cladding Breech 110

60. Cladding Breech at Gouges in Bottom Head 110

61. 410 Stainless Steel Clad to Carbon Steel Interface Weld 111

62. Supplemental UT Markings 111

63. Cracking at Tray Support Ring Weld 112

64. WFMPT Discovered Cracking 113

65. Supplemental NDE May Be Needed 113

66. Areas of Chemical Activity 114

67. Areas of Activity 114

68. Hardware Corrosion 115

69. Stuck Valves Always Open 115

70. Clean Square-edged Perforation 116

71. Valve Fretting 116

72. Slotting from Below 117

73. Valve Leg and Perforation Inspection 117

74. Indentation of Valves 118

75. New Caged Valves with Dimples 118

76. New Caged Valve Cage Tabs 119

77. Small Fixed Valves 120

78. Fixed Valved Lateral Vapor Directional Flow 120

79. Removable Fixed Valves Reduce Fouling 121

80. Removable Fixed Valves Tray Damage 121

81. Bubble Caps on Stepped Trays 122

82. Fibrous Deposits and Fouling Under Bubble Caps 122

83. Tray Deck Should Be Scraped Clean 123

84. Tray Fatigue Cracking 124

85. Light-to-moderate Weir Corrosion 124

86. Loose and Missing Hardware Failure 125

87. Downcomer and Seal Pan Clamps Loose 125

88. Downcomer Clamp Loose 126

89. Tray Support Ring Corroded to Failure 126

90. Shell Corroded to Half Wall Adjacent Top Three Rings 127

91. Support Ring Grooving 127

92. Deposits Adjacent to Shell Are on Ring 128

93. Cracking of Ring Attachment Weld 128

94. Tray Support Ring Butt Weld Cracking 129

95. Breeching of the Seal Weld 129

96. Shadowing Inside the Downcomer 130

97. Shadow the Downcomer Shell Every Tray 130

Inspection Practices for Pressure Vessels

1. Scope

   This recommended practice (RP) supplements API 510 by providing pressure vessel inspectors with information that can improve skills and increase basic knowledge of inspection practices. This RP describes inspection practices for the various types of pressure vessels (e.g. drums, heat exchangers, columns, reactors, air coolers, spheres) used in petroleum refineries and chemical plants. This RP addresses vessel components, inspection planning processes, inspection intervals, methods of inspection and assessment, methods of repair, records and reports. API 510 has requirements and expectations for inspection of pressure vessels.

   
   

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: In-service Inspection, Rating, Repair, and Alteration

   
   

   API Recommended Practice 571, Damage Mechanisms Affecting Fixed Equipment in the Refining Industry

   
   

   API Recommended Practice 574, Inspection Practices for Piping System Components

   
   

   API 579-1/ASME FFS 1 1, Fitness-For-Service

   
   

   API Recommended Practice 580, Risk-Based Inspection

   
   

   API Publication 2217A, Guidelines for Safe Work in Inert Confined Spaces in the Petroleum and Petrochemical Industries

   
   

   ASME Boiler and Pressure Vessel Code (BPVC), Section VIII: Pressure Vessels

   
   

3. Terms and Definitions

3.1 Definitions

For the purposes of this document, the following definitions apply.

3.1.1

alteration

A physical change in any component that has design implications that affect the pressure-containing capability of a pressure vessel beyond the scope described in existing data reports. The following should not be considered alterations: any comparable or duplicate replacement, the addition of any reinforced nozzle less than or equal to the size of existing reinforced nozzles, and the addition of nozzles not requiring reinforcement.

3.1.2

cladding

A metal integrally bonded onto another metal under high pressure and temperature whose properties are better suited to resist damage from the process than the substrate material.

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