Corrosion Under Insulation and Fireproofing

API RECOMMENDED PRACTICE 583 SECOND EDITION, MARCH 2021

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Foreword

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Contents

1. Scope 1

2. Normative References 1

3. Terms, Definitions, Acronyms, and Abbreviations 2

   1. Terms and Definitions 2

   2. Acronyms and Abbreviations 7

4. Introduction to the Causes of Damage 8

   1. General. 8

   2. CUI in Carbon and Low Alloy Steels 9

   3. CUI in Austenitic and Duplex Stainless Steels 10

   4. CUF in Carbon and Low Alloy Steels 11

   5. CUI on Aluminum Piping 12

5. Areas Susceptible to Damage 12

   1. General. 12

   2. General Areas of Damage 13

   3. Pressure Vessels 14

   4. Piping 14

   5. Tankage and Spheres 18

   6. Heat-traced Systems 18

   7. Shutdown/Mothballing 19

6. Insulation and Fireproofing Systems 20

   1. Insulation Materials and Thermal Insulative Coatings 20

   2. Insulation Jacketing/Cladding 28

   3. Caulking 30

   4. Fireproofing Materials 30

   5. Coatings Under Insulation and Fireproofing Systems 35

7. Inspection for CUI and CUF Damage 37

   1. General. 37

   2. Inspection of Piping Operating Below 32 °F (0 °C) 38

   3. Inspection Tools and Methods 38

8. Risk-Based Inspection 62

9. Design Practices to Minimize CUI 63

   1. General. 63

   2. Coatings for Hot and Cold Services 63

   3. Insulation Materials 63

   4. Jacketing 65

   5. General Design Aspects 67

   6. Insulation 70

   7. Heat-traced Systems 70

   8. Protective Coatings and Caulk 70

   9. Shutdown/Mothballing 71

   10. Quality Control/Quality Assurance 71

10. Design Practices to Minimize CUF 72

    1. General. 72

    2. Dense and Lightweight Concrete 73

    3. Lightweight Cementitious Products 73

    4. Intumescent Coatings and Subliming Compounds 73

    5. Protective Coatings 73

    6. Quality Control/Quality Assurance 73

11. Maintenance to Mitigate CUI/CUF Issues 73

    1. General. 73

    2. Programmed/Condition-based Maintenance 74

    3. Execution 74

    4. Deluge System Issues 75

    5. Mitigation of CUI/CUF Damage 75

    6. Mitigation of CUF Damage 83

12. Repair Techniques/Strategies 84

    1. General. 84

    2. Surface Coatings 84

    3. Weld Repairs 84

    4. Safety Issues 85

Annex A (informative) Examples of a Qualitative Likelihood Assessment System 87

Annex B (informative) Examples of Insulation Techniques for Various Applications 90

Bibliography 96

Figures

1. SCC Tendency of Austenitic and Duplex Alloys 11

2. Jacketed Piping with Missing Insulation Plug (top photo) Allowing Water Ingress and Subsequently Corrosion on Piping Elbow (bottom photo) 16

3. CUI Failure of 4 in. Gas Compressor Recycle Line 17

4. CUI at an Insulation Support Ring 19

5. Failure of Sphere Legs Due to CUF 19

6. Principle of Guided Wave UT Compared with Conventional Manual UT 40

7. Guided Wave Transducer Arrays, Signal Representation, and Results 41

8. Performance Summary 41

9. Permanently Installed Monitoring Array of Transducers 43

10. Schematic of Profile Radiography Setup 44

11. Examples of Profile Radiograph Showing CUI Damage on an Insulated Pipe 45

12. Pit Depth Measurement Techniques 45

13. Application Limits for Tangential and Film Density Radiography 46

14. Photo of a Flash Radiography System for Pipe Profiling to Detect Wall Thinning Due to Corrosion 49

15. Radiometric Profiling Display and System 50

16. RTR Display and System 51

17. A Pulsed Eddy Current Instrument with Probe 52

18. A Pulsed Eddy Current Array System 53

19. Principle of Operation the Pulsed Eddy Current Technique 54

20. A PEC Display Showing the Decay of the Eddy Currents (top), Wall Thickness and Compensated Wall Thickness (middle), and a Log-Log Representation of the Inspection (bottom) 55

21. Difference Between Average and Minimum Wall Thickness Within the Footprint 56

22. A Photo of a Neutron Backscatter System 58

23. Thermographs Showing Areas with Wet Insulation (in red) 60

24. Examples of Inspectors Working with the Tool (top image); for the bottom images, the Left- hand Side Shows a System and the Right-hand Side Shows the Corresponding MDI Response 61

25. Areas of Concern for CUI in a Vertical Vessel 65

26. Example of a Design/Layout That Is Difficult to Insulate 67

27. Vertical Piping Should Be Wrapped from Bottom-to-Top with an Overlap 76

28. Schematic of Two-wire Electric Spray Processes and Deposit Microstructure 77

29. Schematic of Oxy-fuel Wire Spray Processes 77

30. Example of a Petroleum-based Tape Wrap System 79

31. Photograph of a Personnel Protective Cage on a Vertical and Elbow Section of Piping (left) and a Removable Personnel Protective Cage on a Valve (right) 80

32. Photo Showing Piping with and without Damage to the Insulation System 81

33. Example of Jacketing Joint with Missing Caulking 82

34. Example of Poor Jacketing Fit-up 82

35. Examples of Joints with Poor Ability to Shed Water 83

36. Example of Missing End Cap. 83

1. Method of Insulating Nozzles and Manways 90

2. Method for In Situ Polyurethane Foaming of Straight Pipe and Valve/Flange Boxes 90

3. Method for Insulating Pipe Support with and without Continuous Vapor Barrier 91

4. Method for Insulating Miscellaneous Attachments 92

5. Method for Insulating Vertical Vessel Bottom Support Ring 92

6. Method of Diverting Water Away from Critical Locations 93

7. Method of Avoiding Water Buildup at Insulation Supports 93

8. Method of Avoiding Water Buildup for Vessel Nozzles and Attachments 94

9. Method of Avoiding Water Buildup for Piping 95

10. Method of Avoiding Water Buildup for Horizontal and Vertical Gussets 95

Tables

1. Locations for CUI Throughout Process Facilities 13

2. Locations for CUI/CUF on Vessels 14

3. Susceptible Locations for CUI and CUF in Piping 15

4. Susceptible Locations for CUI/CUF in Piping Operating Below the Dew Point 17

5. Locations for CUI/CUF in Tanks and Spheres 18

6. Various Types of Insulation in Refining and Chemical Plants 20

7. Comparison of Surface Preparation Standards 36

1. Example of Points-based Parameter Rating for Likelihood of CUI 87

2. Likelihood Rating 88

3. Example of Points-based Parameter Rating for Likelihood of CUI 88

4. Likelihood Rating 88

5. Example of Points-based Parameter Rating for Likelihood of CUF 89

6. Likelihood Rating 89

Corrosion Under Insulation and Fireproofing

1. Scope

   
   

   This recommended practice covers the design, maintenance, inspection, and mitigation practices to address external corrosion under insulation (CUI) and corrosion under fireproofing (CUF). The document discusses the external corrosion of carbon and low alloy steels under insulation and fireproofing and the external chloride stress corrosion cracking (ECSCC) of austenitic and duplex stainless steels under insulation. The document does not cover atmospheric corrosion or corrosion at uninsulated pipe supports but does discuss corrosion at insulated pipe supports.

   
   

   The purpose of this recommended practice is to:

   
   

   • help owner/users understand the complexity of the many CUI/CUF issues;

     
     

   • provide owner/users with understanding on the advantages and limitations of the various nondestructive examination methods used to identify CUI and CUF damage;

     
     

   • provide owner/users with an approach to risk assessment (i.e. likelihood of failure and consequence of failure) for CUI and CUF damage; and

     
     

   • provide owner/users guidance on how to design, install, and maintain insulation systems to avoid CUI and CUF damage.

   
   

   The practices described in this document apply to pressure vessels, piping, and storage tanks and spheres. The document discusses the factors impacting the damage mechanisms, the guidelines to prevent external corrosion/cracking under insulation, the maintenance practices to avoid damage, the inspection practices to detect/assess damage, and the guidelines for risk assessment of equipment or structural steel subject to CUI and CUF damage.

   
   

2. Normative References

The following documents are referred to in the text in such a way that some or all of their content constitutes requirements and/or recommendations of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any addenda) applies.

API 510, Pressure Vessel Inspection Code: In-service Inspection, Rating, Repair, and Alteration

API 570, Piping Inspection Code: In-service Inspection, Rating, Repair, and Alteration of Piping Systems

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

API Recommended Practice 580, Risk-Based Inspection

API Recommended Practice 581, Risk-Based Inspection Methodology

API Standard 653, Tank Inspection, Repair, Alteration, and Reconstruction, Fifth Edition