Corrosion Under Insulation and Fireproofing

API RECOMMENDED PRACTICE 583 FIRST EDITION, MAY 2014

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Foreword

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Contents

Page

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 7

   1. General 7

   2. CUI in Carbon and Low Alloy Steels 8

   3. CUI in Austenitic and Duplex Stainless Steels 9

   4. CUF in Carbon and Low Alloy Steels 11

   5. CUI on Aluminum Piping 11

5. Areas Susceptible to Damage 11

   1. General 11

   2. General Areas of Damage 12

   3. Pressure Vessels 13

   4. Piping 13

   5. Tankage and Spheres 16

   6. Heat-traced Systems 16

   7. Shutdown/Mothballing 17

6. Insulation and Fireproofing Systems 18

   1. Insulation Materials 18

   2. Insulation Jacketing 24

   3. Caulking 26

   4. Fireproofing Materials 27

   5. Coatings Under Insulation and Fireproofing Systems 32

7. Inspection for CUI and CUF Damage 34

   1. General 34

   2. Inspection of Piping Operating Below 32 °F (0 °C) 35

   3. Inspection Tools and Methods 35

8. Risk-Based Inspection (RBI) 51

   1. General 51

9. Design Practices to Minimize CUI 52

   1. General 52

   2. Coatings for Hot and Cold Services 53

   3. Insulation Materials 53

   4. Jacketing 54

   5. General Design Aspects 56

   6. Insulation 59

   7. Heat-traced Systems 60

   8. Protective Coatings and Caulk 60

   9. Shutdown/Mothballing 61

   10. Quality Control/Quality Assurance 61

       Contents

       Page

10. Design Practices to Minimize CUF 61

    1. General 61

    2. Dense and Lightweight Concrete 62

    3. Lightweight Cementitious Products 62

    4. Intumescent Coatings and Subliming Compounds 62

    5. Protective Coatings 62

    6. Quality Control/Quality Assurance 62

11. Maintenance and Mitigation of CUI/CUF Issues 63

    1. General 63

    2. Programmed/Condition-based Maintenance 63

    3. Execution 64

    4. Deluge System Issues 64

    5. Mitigation of CUI Damage 64

    6. Mitigation of CUF Damage 72

    7. Repair Techniques/Strategies 73

    8. Safety Issues 76

Annex A (informative) Examples of a Qualitative Likelihood Assessment System 78

Annex B (informative) Examples of Insulation Techniques for Various Applications 81

Figure

1. SCC Tendency of Austenitic and Duplex Alloys 10

2. Jacketed Piping with Area for Water Ingress 13

3. CUI Failure of 4-in. Gas Compressor Recycle Line 15

4. CUI at an Insulation Support Ring 17

5. Failure of Sphere Legs Due to CUF 17

6. Guided Wave Transducer Arrays, Signal Representation, and Results 37

7. Schematic of Profile Radiography Setup 38

8. Profile Radiograph of CUI Damage on an Insulated Small Diameter Pipe 39

9. Pit Depth Measurement Techniques 40

10. Application Limits for Tangential and Film Density Radiography 40

11. Photo of a Flash Radiography System for Pipe Profiling to Detect Wall Thinning Due to Corrosion. . . 42 12 Radiometric Profiling Display and System 43

1. RTR Display and System 44

2. A Pulsed Eddy Current Instrument with Probe 46

3. Principle of Operation the Pulsed Eddy Current Technique 47

4. A PEC Display Showing AWT Reading (top left), Logged Inspection Grid (bottom left),

   and the Decay of the Eddy Currents (bottom right) 47

5. Difference Between Average and Minimum Wall Thickness Within the Footprint 47

6. A Photo of a Neutron Backscatter System 50

7. Thermographs Showing Areas with Wet Insulation (in Red) 51

8. Areas of Concern for CUI in a Vertical Vessel 55

9. Example of a Design/Layout That is Difficult to Insulate 57

10. Vertical Piping Should Be Wrapped from Bottom-to-top with an Overlap 65

11. Schematic of Two-wire Electric Spray Processes and Deposit Microstructure 66

    Contents

    Page

12. Schematic of Oxy-fuel Wire Spray Processes 66

13. Example of a Petroleum-based Tape Wrap System 68

14. 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) 69

15. Photo Showing Piping with and Without Damage to the Insulation System 70

16. Example of Jacketing Joint with Missing Caulking 71

17. Example of Poor Jacketing Fit-up 71

18. Examples of Joints with Poor Ability to Shed Water 72

19. Example of Missing End Cap 72

1. Method of Insulating Nozzles and Manways 81

2. Method for In Situ Polyurethane Foaming of Straight Pipe and Valve/Flange Boxes 82

3. Method for Insulating Pipe Support with and Without Continuous Vapor Barrier 83

B.5 Method for Insulating Vertical Vessel Bottom Support Ring 84

B.4 Method for Insulating Miscellaneous Attachments 84

1. Method of Diverting Water Away from Critical Locations 85

2. Method of Avoiding Water Buildup at Insulation Supports 85

3. Method of Avoiding Water Buildup for Vessel Nozzles and Attachments 86

4. Method of Avoiding Water Buildup for Piping 87

5. Method of Avoiding Water Buildup for Horizontal and Vertical Gussets 88

Tables

1. Locations for CUI Throughout Process Facilities 12

2. Locations for CUI/CUF on Vessels 12

3. Susceptible Locations for CUI/CUF in Piping 15

4. Susceptible Locations for CUI/CUF in Piping Operating Below the Dew Point 16

5. Locations for CUI/CUF in Tanks and Spheres 16

6. Commonly Used Insulation Materials 18

7. NIA Guidelines for Sidewalls on Vertical Vessels 26

8. NIA Guidelines for Heads on Vertical Vessels 26

9. Comparison of Surface Preparation Standards 33

Corrosion Under Insulation and Fireproofing

1. Scope

   This recommended practice (RP) 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 RP 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 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 570, Piping Inspection Code

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

API Recommended Practice 572, Inspection Practices for Pressure Vessels

API Recommended Practice 574, Inspection Practices for Piping System Components

API Recommended Practice 575, Guidelines and Methods for Inspection of Existing Atmospheric and Low-pressure Storage Tanks

API Recommended Practice 580, Risk-Based Inspection

API Recommended Practice 581, Risk-Based Inspection Technology

API Recommended Practice 653, Tank Inspection, Repair, Alteration, and Reconstruction

API Technical Report 938-C, Use of Duplex Stainless Steels in the Oil Refining Industry