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API TR 934-J Inspection, Assessment, and Repair of Coke Drums and Peripheral Components in Delayed Coking Units
standard by American Petroleum Institute, 09/01/2021
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.
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API TECHNICAL REPORT 934-J
(COMPLEMENTS API TECHNICAL REPORT 934-G) FIRST EDITION, SEPTEMBER 2021
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Page
Scope 1
Background 1
References 1
Terms and Definitions 4
Acronyms and Abbreviations 6
Inspection and Monitoring of Coke Drums 7
General 7
Inspection for Cracks 7
Inspecting for Bulges 23
Inspecting for Metal Loss and Cladding Damage 28
Monitoring for Drum Bowing, Tilting, and Lift at the Base 29
Use of Strain Gauges and Shell Temperature Measurements to Monitor Drum Damage 32
Frequency of Inspection 32
Damage Assessment 36
Thermal-mechanical Loading of Coke Drums 36
Shell Cracking 36
Shell Bulging 37
Corrosion and Erosion 38
Skirt Cracking and Distortion 39
Overheating Damage (Fire Damage) 39
Fatigue Life 39
Welding Associated with Repairs 39
General 39
Filler Metal Selection 40
Electrode Baking 42
Preheating 43
Controlled Deposition Welding/Temper Bead Welding 43
Postweld Heat Treatment 46
Types of Repairs Associated with Coke Drums 48
General 48
Weld Repairs Made from Inside Surface 48
Weld Repairs Made from Outside Surface 50
Weld Repairs Made from Both Sides 51
Replacing Large Sections of Cylindrical Shell Plates 52
Skirt Repairs, Retrofits, and Replacement 53
Repairs and Modifications to Unheading Devices 59
Repairs to Feed Nozzles 60
Inspection Insulation Windows 62
Foundation Repairs 63
Life Extension Techniques 73
General 73
Temporary Repairs of Cracks 73
Repairs Designed to Last an Extended Period of Time 74
Use of Structural Weld Overlay to Extend Life 75
v
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
VT Examination of a Coke Drum Surface That Displays “Elephant Skin” Cracking 8
PT from the Outside Surface Highlighted Cracks in the Vicinity of the Skirt Attachment Weld 9
PT from the Outside Surface Displays an Area with “Elephant Skin” Cracking 9
Cracking On the External Surface at an Insulation Clip Displayed by Wet Fluorescent MT 10
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
Typical Transducer Arrangement for TOFD Inspection of Welds 11
B-scan Image Obtained by the Application of the TOFD UT Technique
Showing the Presence of an Embedded Flaw 12
Typical Output for TOFD Inspection of Crack Initiating in the Cladding
on the Inside Surface and Propagating Through-wall 12
TOFD Output for Through-wall Crack in Coke Drum Shell 13
TOFD Image from Crack Propagating from the ID Surface 13
Beam Forming, Time Delay, and Focusing and Steering Principle Involved with a PAUT Probe 14
PAUT Crystal Arrangement Provides an Improved Ability to Detect Crack-like
Flaws Compared with Single Crystal UT 15
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
PAUT of Cracking (Type A) from the Outside Surface on the Coke Drum at the Skirt Attachment 16
ACFM Currents Flowing Around a Surface Crack 17
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
Illustration Showing Optimal Times to Record AE Data in a Typical Operating Cycle
Involving a Two-coke Drum Unit 20
Example of Energy vs Time and Temperature Graphs for Quench Half Cycle 21
Example of AET Data Displaying Characteristics of Active Flaws (Red Data) 21
Example of AET Results Depicting AE Sensor and Skin Thermocouple (TC)
Locations Along with Follow-up Areas Provided to the Equipment Owner 22
Bulges on the Inside Surface of a Coke Drum Found by Internal VT Examination
Are Highlighted Using Oblique Lighting 24
Use of a Straight Edge from the ID and OD to Measure Bulging 25
Laser Profiling Measurements Show the Growth of Bulging over a 5-year Period 26
Laser Profile Data Are Shown for Five Sets of Measurements in a Vertical Section
Comparison and a Polar Plot Comparison 26
Laser Profiling Detected a Sharp Deep Distortion at Middle Course of Two Different Drums 27
Photos from a Video Camera Show Internal Damage in Coke Drum 28
Monitoring of Tilting Progression in Two Coke Drums andnComparison
with Site-defined Acceptable Limits 29
Comparison of Tilting and Shortening in a Coke Drum 30
Measurements Taken on Two Coke Drums Show Ovalization and the
Resulting Lift at the Base Ring 31
vi
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
Removal of the Cladding as Required for Weld Repairs Made from Inside Surface 48
After Welding, the Weld Reinforcement Is Ground Flush with the Inside Side
Surface of the Base Metal 49
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
The Cladding Restoration Weld Is Ground Flush with the Cladding Surface 50
Typical Geometry for a Weld Repair Made from Both Sides of Coke Drum Wall 51
Typical Skirt Attachment Details and Dimensions 54
Most Common Locations for Cracking of a Welded Vessel-to-Skirt Attachment 55
Skirt Attachment Repair Sequence 56
Typical Coke Drum Skirt Keyhole System 57
Cracking Initiated at the Slot Keyhole and Propagating Through the Skirt Attachment Weld 57
A Tongue-and-Groove Skirt Design 58
A Welded Skirt Retrofitted to a Bracketed Sliding Skirt 59
Typical Insulated Feed Entry into a Drum Bottom Cover 61
Typical Insulated Feed Entry into the Side of the Drum Bottom Cover 61
Nozzle with Retractable Feed Device in the Retracted Position 62
Typical Inspection Insulation Windows Used on Coke Drums 63
Internal View and External View of the Drum Cylindrical Section Generated with Laser Mappings 64
Base Ring Modifications and Concrete Excavation 64
Setting the Jacks and Lifting the Drum 65
Grouting Process After Lifting 65
Modifications of Base Ring, Including New Gusset Plates and Positioning
and Installation of Multiple Flat Jacks 66
Grouted to Match Tabletop Surface 66
Final Grout Stage 67
Completed Installation 67
Drawing of Non-bolted Anchor Blocks 70
Inspection and Crack Excavation Performed Prior to Weld Overlay Repairs 76
Through-wall Crack Repaired 77
Finished Structural Overlay Deposit 77
The Excavation for a CDW/TBW Repair Should Have an Opening That Is 2.5 Times the Depth 81
Application of First Layer Using CDW/TBW 82
Application of Second and Third Layer Using CDW/TBW 82
The Remaining Fill Passes Are Made Using Normal Bead Sequencing 82
Completed Weld with Crown Ground Off 83
Tables
Primary Source of Information or Control Document for General Categories
of Information on Coke Drums and Peripheral Components 1
Typical Onstream (Non-turnaround) Inspection Techniques and
Suggested Frequencies for Coke Drums 33
Typical Off-stream (e.g. Turnaround) Inspection Techniques and
Suggested Frequencies for Coke Drums 35
Typical Filler Metal Choices for Coke Drum Repairs 40
Page
Typical Minimum Preheat Temperatures for Coke Drum Repairs 43
Requirements for CDW as Stated in API 510, TBW as Stated in NB-23, and TBW
as Stated in ASME Code Section IX 44
Typical Welding Parameters Using a Nickel-based Consumable 51
Typical Welding Parameters for the First Three Passes of a CDW/TBW Procedure
Using a SMAW Process 81
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
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 |
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
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