Inspection, Assessment, and Repair of Coke Drums and Peripheral Components in Delayed Coking Units

API TECHNICAL REPORT 934-J

(COMPLEMENTS API TECHNICAL REPORT 934-G) FIRST EDITION, SEPTEMBER 2021

Special Notes

API publications necessarily address problems of a general nature. With respect to particular circumstances, local, state, and federal laws and regulations should be reviewed. The use of API publications is voluntary. In some cases, third parties or authorities having jurisdiction may choose to incorporate API standards by reference and may mandate compliance.

Neither API nor any of API’s employees, subcontractors, consultants, committees, or other assignees make any warranty or representation, either express or implied, with respect to the accuracy, completeness, or usefulness of the information contained herein, or assume any liability or responsibility for any use, or the results of such use, of any information or process disclosed in this publication. Neither API nor any of API's employees, subcontractors, consultants, or other assignees represent that use of this publication would not infringe upon privately owned rights.

API publications may be used by anyone desiring to do so. Every effort has been made by the Institute to assure the accuracy and reliability of the data contained in them; however, the Institute makes no representation, warranty, or guarantee in connection with this publication and hereby expressly disclaims any liability or responsibility for loss or damage resulting from its use or for the violation of any authorities having jurisdiction with which this publication may conflict.

API publications are published to facilitate the broad availability of proven, sound engineering and operating practices. These publications are not intended to obviate the need for applying sound engineering judgment regarding when and where these publications should be utilized. The formulation and publication of API publications is not intended in any way to inhibit anyone from using any other practices.

Any manufacturer marking equipment or materials in conformance with the marking requirements of an API standard is solely responsible for complying with all the applicable requirements of that standard. API does not represent, warrant, or guarantee that such products do in fact conform to the applicable API standard.

All rights reserved. No part of this work may be reproduced, translated, stored in a retrieval system, or transmitted by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission from the publisher. Contact the Publisher, API Publishing Services, 200 Massachusetts Avenue NW, Suite 1100, Washington, DC 20001.

Copyright © 2021 American Petroleum Institute

Foreword

Nothing contained in any API publication is to be construed as granting any right, by implication or otherwise, for the manufacture, sale, or use of any method, apparatus, or product covered by letters patent. Neither should anything contained in the publication be construed as insuring anyone against liability for infringement of letters patent.

This document was produced under API standardization procedures that ensure appropriate notification and participation in the developmental process and is designated as an API standard. Questions concerning the interpretation of the content of this publication or comments and questions concerning the procedures under which this publication was developed should be directed in writing to the Director of Standards, American Petroleum Institute, 200 Massachusetts Avenue NW, Suite 1100, Washington, DC 20001. Requests for permission to reproduce or translate all or any part of the material published herein should also be addressed to the director.

Suggested revisions are invited and should be submitted to the Standards Department, API, 200 Massachusetts Avenue NW, Suite 1100, Washington, DC 20001, standards@api.org.

iii

Contents

Page

1. Scope 1

2. Background 1

   1. References 1

   2. Terms and Definitions 4

   3. Acronyms and Abbreviations 6

3. Inspection and Monitoring of Coke Drums 7

   1. General 7

   2. Inspection for Cracks 7

   3. Inspecting for Bulges 23

   4. Inspecting for Metal Loss and Cladding Damage 28

   5. Monitoring for Drum Bowing, Tilting, and Lift at the Base 29

   6. Use of Strain Gauges and Shell Temperature Measurements to Monitor Drum Damage 32

   7. Frequency of Inspection 32

4. Damage Assessment 36

   1. Thermal-mechanical Loading of Coke Drums 36

   2. Shell Cracking 36

   3. Shell Bulging 37

   4. Corrosion and Erosion 38

   5. Skirt Cracking and Distortion 39

   6. Overheating Damage (Fire Damage) 39

   7. Fatigue Life 39

5. Welding Associated with Repairs 39

   1. General 39

   2. Filler Metal Selection 40

   3. Electrode Baking 42

   4. Preheating 43

   5. Controlled Deposition Welding/Temper Bead Welding 43

   6. Postweld Heat Treatment 46

6. Types of Repairs Associated with Coke Drums 48

   1. General 48

   2. Weld Repairs Made from Inside Surface 48

   3. Weld Repairs Made from Outside Surface 50

   4. Weld Repairs Made from Both Sides 51

   5. Replacing Large Sections of Cylindrical Shell Plates 52

   6. Skirt Repairs, Retrofits, and Replacement 53

   7. Repairs and Modifications to Unheading Devices 59

   8. Repairs to Feed Nozzles 60

   9. Inspection Insulation Windows 62

   10. Foundation Repairs 63

7. Life Extension Techniques 73

   1. General 73

   2. Temporary Repairs of Cracks 73

   3. Repairs Designed to Last an Extended Period of Time 74

   4. Use of Structural Weld Overlay to Extend Life 75

v

Contents

Annex A (informative) Controlled Deposition Welding/Temper Bead Welding

Page

Using a SMAW Process and a GMAW Process 81

Annex B (informative) Relevant References on Coke Drunms But Not Imbedded in Document 85

Bibliography 90

Figures

1. VT Examination of a Coke Drum Surface That Displays “Elephant Skin” Cracking 8

2. PT from the Outside Surface Highlighted Cracks in the Vicinity of the Skirt Attachment Weld 9

3. PT from the Outside Surface Displays an Area with “Elephant Skin” Cracking 9

4. Cracking On the External Surface at an Insulation Clip Displayed by Wet Fluorescent MT 10

5. SWUT Can Be Used from the Outside Surface to Find and Size Cracks Typically in the

   Vicinity of the Skirt Attachment (Shown as Types “A,” “B,” and “C” Cracks) 10

6. Typical Transducer Arrangement for TOFD Inspection of Welds 11

7. B-scan Image Obtained by the Application of the TOFD UT Technique

   Showing the Presence of an Embedded Flaw 12

8. Typical Output for TOFD Inspection of Crack Initiating in the Cladding

   on the Inside Surface and Propagating Through-wall 12

9. TOFD Output for Through-wall Crack in Coke Drum Shell 13

10. TOFD Image from Crack Propagating from the ID Surface 13

11. Beam Forming, Time Delay, and Focusing and Steering Principle Involved with a PAUT Probe 14

12. PAUT Crystal Arrangement Provides an Improved Ability to Detect Crack-like

    Flaws Compared with Single Crystal UT 15

13. PAUT for a Type B Crack at a Shell-to-Skirt Attachment. PAUT Transducers Are

    Placed Both on the Inside and Outside Surface of the Coke Drum 15

14. PAUT of Cracking (Type A) from the Outside Surface on the Coke Drum at the Skirt Attachment 16

15. ACFM Currents Flowing Around a Surface Crack 17

16. ACFM Tool Determined the Depth and Length of a Crack That Initiated on the Coke Drum Internal Surface. A Crack Was Found During the Internal Visual

    Examination of the Coke Drum Using a Remotely Controlled Video Camera 18

17. Illustration Showing Optimal Times to Record AE Data in a Typical Operating Cycle

    Involving a Two-coke Drum Unit 20

18. Example of Energy vs Time and Temperature Graphs for Quench Half Cycle 21

19. Example of AET Data Displaying Characteristics of Active Flaws (Red Data) 21

20. Example of AET Results Depicting AE Sensor and Skin Thermocouple (TC)

    Locations Along with Follow-up Areas Provided to the Equipment Owner 22

21. Bulges on the Inside Surface of a Coke Drum Found by Internal VT Examination

    Are Highlighted Using Oblique Lighting 24

22. Use of a Straight Edge from the ID and OD to Measure Bulging 25

23. Laser Profiling Measurements Show the Growth of Bulging over a 5-year Period 26

24. Laser Profile Data Are Shown for Five Sets of Measurements in a Vertical Section

    Comparison and a Polar Plot Comparison 26

25. Laser Profiling Detected a Sharp Deep Distortion at Middle Course of Two Different Drums 27

26. Photos from a Video Camera Show Internal Damage in Coke Drum 28

27. Monitoring of Tilting Progression in Two Coke Drums andnComparison

    with Site-defined Acceptable Limits 29

28. Comparison of Tilting and Shortening in a Coke Drum 30

29. Measurements Taken on Two Coke Drums Show Ovalization and the

    Resulting Lift at the Base Ring 31

    vi

    Contents

30. The Dimensions for the Soak Band, Heated Bands, and Thermal Gradient Bands

    Page

    for PWHT of a Drum As Provided in the Guidelines in WRC 452 47

31. Removal of the Cladding as Required for Weld Repairs Made from Inside Surface 48

32. After Welding, the Weld Reinforcement Is Ground Flush with the Inside Side

    Surface of the Base Metal 49

33. The Cladding Restoration Weld Involves Depositing a Butter Layer on the Cladding Bevel, Followed by Depositing Two Layers of Weld Metal over the Entire Area

    Where the Cladding Has Been Removed 49

34. The Cladding Restoration Weld Is Ground Flush with the Cladding Surface 50

35. Typical Geometry for a Weld Repair Made from Both Sides of Coke Drum Wall 51

36. Typical Skirt Attachment Details and Dimensions 54

37. Most Common Locations for Cracking of a Welded Vessel-to-Skirt Attachment 55

38. Skirt Attachment Repair Sequence 56

39. Typical Coke Drum Skirt Keyhole System 57

40. Cracking Initiated at the Slot Keyhole and Propagating Through the Skirt Attachment Weld 57

41. A Tongue-and-Groove Skirt Design 58

42. A Welded Skirt Retrofitted to a Bracketed Sliding Skirt 59

43. Typical Insulated Feed Entry into a Drum Bottom Cover 61

44. Typical Insulated Feed Entry into the Side of the Drum Bottom Cover 61

45. Nozzle with Retractable Feed Device in the Retracted Position 62

46. Typical Inspection Insulation Windows Used on Coke Drums 63

47. Internal View and External View of the Drum Cylindrical Section Generated with Laser Mappings 64

48. Base Ring Modifications and Concrete Excavation 64

49. Setting the Jacks and Lifting the Drum 65

50. Grouting Process After Lifting 65

51. Modifications of Base Ring, Including New Gusset Plates and Positioning

    and Installation of Multiple Flat Jacks 66

52. Grouted to Match Tabletop Surface 66

53. Final Grout Stage 67

54. Completed Installation 67

55. Drawing of Non-bolted Anchor Blocks 70

56. Inspection and Crack Excavation Performed Prior to Weld Overlay Repairs 76

57. Through-wall Crack Repaired 77

58. Finished Structural Overlay Deposit 77

1. The Excavation for a CDW/TBW Repair Should Have an Opening That Is 2.5 Times the Depth 81

2. Application of First Layer Using CDW/TBW 82

3. Application of Second and Third Layer Using CDW/TBW 82

4. The Remaining Fill Passes Are Made Using Normal Bead Sequencing 82

5. Completed Weld with Crown Ground Off 83

Tables

1. Primary Source of Information or Control Document for General Categories

   of Information on Coke Drums and Peripheral Components 1

2. Typical Onstream (Non-turnaround) Inspection Techniques and

   Suggested Frequencies for Coke Drums 33

3. Typical Off-stream (e.g. Turnaround) Inspection Techniques and

   Suggested Frequencies for Coke Drums 35

4. Typical Filler Metal Choices for Coke Drum Repairs 40

   
   

   Contents

   
   

   Page

5. Typical Minimum Preheat Temperatures for Coke Drum Repairs 43

6. Requirements for CDW as Stated in API 510, TBW as Stated in NB-23, and TBW

   as Stated in ASME Code Section IX 44

7. Typical Welding Parameters Using a Nickel-based Consumable 51

1. Typical Welding Parameters for the First Three Passes of a CDW/TBW Procedure

   Using a SMAW Process 81

2. Typical Welding Parameters for the First Three Passes of a CDW/TBW Procedure

Using a GMAW Process 84

Inspection, Assessment, and Repair of Coke Drums and Peripheral Components in Delayed Coking Units

1. Scope

   
   

   This document includes information and guidance on the practices used by industry practitioners on the inspection, assessment, and repair of coke drums and peripheral components in delayed coking units. The guidance is general and does not reflect specific details associated with a design offered by licensors of delayed coking technology or inspection tools, repair techniques, and/or engineering assessments offered by contractors. For details associated with the design offered by a licensor or services provided by contractors, the licensor or contractor should be consulted for guidance and recommendations for their specific design details, inspection techniques, assessment procedures, and repair practices. This document is a technical report and as such provides generally used practices in industry and is not an API Recommended Practice.

   
   

   This document complements information contained in API 934-G, which also contains information and guidance on the practices used by industry practitioners on coke drums and peripheral components. There is some overlap in the information and guidance provided in this document and in API 934-G; however, one of these documents will be considered the primary source of information or control document for this information. Table 1 shows which technical report will serve as the primary source of information or the control document for each of the general categories of information.

   
   

   Table 1—Primary Source of Information or Control Document for General Categories of Information on Coke Drums and Peripheral Components

   
   

   Information Category	Control Document
   General Information on Delayed Coking	API 934-G
   Results on Past Industry Surveys of Coke Drums	API 934-G
   Description of Damage Mechanisms for Coke Drums	API 934-G
   Design	API 934-G
   Materials Selection	API 934-G
   Fabrication	API 934-G
   Operating Practices	API 934-G
   Inspection Associated with Finding and Characterizing Damage	API 934-G
   Inspection Associated with Repairs	API 934-J
   Damage Assessment	API 934-J
   Repairs	API 934-J
   Welding Considerations	API 934-J
   Life Extension	API 934-J

   
   

2. Background

2.1 References

The following referenced documents are employed as guidance in the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the reference document (including any amendments) applies.

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

1