Table Of ContentFatigue Behaviour of Coke Drum Materials and Its Application to Extend the Service
Lives of Coke Drums
by
Jie Chen
A thesis submitted in partial fulfillment of the requirements for the degree of
Doctor of Philosophy
Department of Mechanical Engineering
University of Alberta
© Jie Chen, 2014
Abstract
Coke drums are vertical pressure vessels used in the delayed coking process in
petroleum refineries. They are normally constructed of carbon or low carbon alloy steels
internally clad with stainless steel to protect the coke drums from corrosion during
operations. Significant temperature variation during the delayed coking process causes
damage in coke drums in the form of bulging and cracking. Hundred thousands of dollars
are spent to repair the units and the loss from the disruption of the production could be
even much higher. There are studies on the fatigue life estimation for coke drums, but
these are based on uniaxial strain-fatigue life curves at various constant temperatures,
which do not consider cyclic temperature conditions. There are relatively few
investigations involving experiments to simulate and predict the damage and fatigue life
of coke drums. To more accurately analyze the fatigue damage mechanism of coke drums,
a systemic-experimental investigation on fatigue behaviours of coke drum materials has
been carried out in this study. A thermal-mechanical fatigue (TMF) testing system has
been successfully designed and developed to perform the complex TMF tests. The
developed system can successfully simulate cyclic thermal-mechanical loading
conditions experienced by coke drums. In addition, an alternative strain control and
measurement technique is developed for strain-controlled fatigue tests at elevated
temperature. The fatigue lives of the candidate materials are first investigated under
isothermal condition. More complex TMF tests are then performed on these candidate
materials. Two coke drum base materials (C-½Mo and 2¼Cr-1Mo) are investigated and
compared under isothermal and thermal-mechanical cyclic loadings. Based on the current
experimental study and, in combination with the API survey data, it is concluded that C-
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½Mo is a better base material than 2¼Cr-Mo from the standpoints of fatigue resistance.
Since the coke drums are constructed by welding a number of shell plates, the fatigue
behaviours of weld and heat affected zone (HAZ) material are also studied. A modified
four-point correlation (FPC) method has been developed to predict the fatigue lives of
weld and HAZ material based on their tensile properties. Finally, based on the TMF data
of the coke drum materials obtained through this study, along with a new statistical
fatigue life prediction method developed in our group, the fatigue lives of coke drums can
be more reasonably predicted.
This study leads to better understanding of damage mechanisms occurring in coke
drums. The comprehensive coke drum material data obtained through this study are
valuable for designers and operators of coke drums. More important, a number of useful
guidelines including optimal selection of materials, more accurate analysis method and
reliable life prediction method for coke drums are summarized. Application of these
guidelines will be beneficial for designing and manufacturing of more robust new coke
drums, as well as for extending service lives of the existing coke drums from the
operational and maintenance point of view.
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Preface
This thesis is an original work by Jie Chen. Some of the research conducted for
this thesis forms part of an Collaborative Research Projects with Suncor Energy, Husky
Energy, and Sumitomo Heavy Industries, Ltd., Japan, and it is also funded by Natural
Sciences and Engineering Research Council of Canada.
The technical apparatus referred to in chapter 2 was designed and developed by
myself, with the assistance of B. Faulkner. The new developed strain control technique
for high temperature fatigue tests in chapter 3, a comparative study on fatigue lives of
2¼Cr-1Mo and C-½Mo base materials used for the construction of delayed coke drums
in chapter 4, a proposed fatigue life prediction method for coke drum base, weld, and
HAZ materials from tensile properties in chapter 5, a temperature dependent fatigue life
prediction model for coke drum materials in chapter 6, as well as an experimental
evaluation of fatigue life of coke drum materials with weld and clad materials in chapter
7 and 8 are my original work. Statistical method for the fatigue life estimation of coke
drums in chapter 9 is the work collaborated in our research group with Dr. Z. Yan and Y.
Zhang.
Part of chapter 2 of this thesis has been published as J. Chen and Z. Xia, "Fatigue
behaviour of coke drum materials under thermal mechanical cyclic loading," Theoretical
Applied Mechanical Letters 2014, 4(4):6-041006. Chapter 5 of this thesis has been
published as J. Chen and Z. Xia, "A fatigue life prediction method for coke drum base,
weld, and HAZ materials from tensile properties," Materials & Design Vol. 63, 575-583,
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2014. I was responsible for the development of the technical apparatus, experimental
investigation and analysis as well as the manuscript composition. Dr. Z. Xia assisted with
the manuscript edits and was the corresponding author. Chapter 7 of this thesis has been
published as J. Chen, T. Yamamoto, Z. Xia and K. Esaki, "Experimental Evaluation of
Fatigue Life of Coke Drum Materials with Weld Sections," in the proceeding of ASME
2013 Pressure Vessels and Piping Conference, Vol. 3: Design and Analysis, Paris, France,
July 14-18, 2013. I was responsible for the experimental investigation and analysis as
well as the manuscript composition. T. Yamamoto and K. Esaki were involved with
project initiation and manuscript revision. Dr. Z. Xia assisted with the manuscript edit
and was the supervisory author. The permission for inclusion of this conference paper in
this dissertation is granted by ASME.
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Acknowledgements
The author wishes to express his sincere appreciation to Dr. Zihui Xia for his
guidance and patience throughout this endeavour. Without his guidance and persistent
help this dissertation would not have been possible.
My deepest gratitude is extended to Mr. Bernie Faulkner, who gives me great help
and invaluable suggestion on developing the experimental facility and manufacturing the
test specimens. It would not be possible to successfully develop the unique testing system
without him.
I also would like to take this opportunity to express my thanks to Mr. John
Aumuller and other members of coke drum research team and ACME group, for offering
great support and discussions. It was a great pleasure to be among them. Furthermore, I
would like to thank Mr. Li Liu and Mr. Edward Wang, who provides me enormous help
during their summer research.
I am especially grateful to my wife, Shuo Tong, for being so patient and
supportive throughout my PhD study. I would like to express my deep gratitude to her for
standing right behind me with all her warmth, sensitivity, and understanding.
And last of all, I would like to thank both of our parents for their spiritual care and
amazing love and support.
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Table of Contents
CHAPTER 1 Overall Introduction ......................................................... 1
1.1 Background of Coke Drums and Its Operation ......................................................... 1
1.2 Problems and Studies Related with Coke Drum ........................................................ 2
1.3 Objectives of the Study .............................................................................................. 7
1.4 Outline of the Thesis .................................................................................................. 9
References ......................................................................................................................... 10
CHAPTER 2 Development of Biaxial Thermal-Mechanical Fatigue
Testing System and Its Application ................................................... 14
2.1 Introduction .............................................................................................................. 15
2.2 Design Strategy for the Biaxial TMF Test System .................................................. 16
2.2.1 High Temperature Extensometer ...................................................................... 18
2.2.2 Heating Device . 21
2.2.3 Temperature Measurement . 24
2.2.4 Control System. 25
2.2.4.1 Time-dependent strain-controlled mode ........................................................... 26
2.2.4.2 Temperature-dependent strain-controlled mode ............................................... 27
2.2.5 High Temperature Gripping Fixtures ................................................................ 28
2.2.6 Internal Presure . 30
2.2.7 Design of TMF Specimens ............................................................................... 32
2.2.8 Overview of the Completed System ................................................................. 33
2.3 Application of the TMF System on SA204 TP410S ............................................... 37
2.3.1 Test Program . 37
2.3.2 Test Results and Comparison of ILCF and TMF of 410S ................................ 38
2.3.3 Comparison of Time and Temperature Based TMF Tests ................................ 43
2.3.4 Biaxial TMF test with Internal Pressure ........................................................... 44
2.4 Conclusions .............................................................................................................. 48
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References ......................................................................................................................... 49
CHAPTER 3 An Alternative Approach for Strain Measurement and
Control in Fatigue Tests at Elevated Temperature ......................... 52
3.1 Introduction .............................................................................................................. 53
3.2 Material and Specimen Geometry ........................................................................... 56
3.3 Experimental Setup and Extensometer .................................................................... 58
3.4 Establishment and Verification of Strain Correlation.............................................. 59
3.4.1 Analytical Analysis . 59
3.4.2 Finite Element Method ..................................................................................... 62
3.4.3 Experimental Verification . 64
3.5 Results and Discussion ............................................................................................ 65
3.5.1 Characterization of CSSC of SA387 Gr 22 CL 2 at Constant Temperatures ... 65
3.5.2 Analytical Analysis . 66
3.5.3 Finite Element Method ..................................................................................... 68
3.5.4 Experimental Verification . 73
3.5.5 Comparison of Fatigue Data ............................................................................. 75
3.6 Strain Correlation for Thermal-Mechanical Fatigue (TMF) .................................... 77
3.7 Conclusions .............................................................................................................. 83
References ......................................................................................................................... 84
CHAPTER 4 A Comparative Study on Fatigue Lives of 2¼Cr-1Mo
and C-½Mo Base Materials Used for the Construction of Delayed
Coke Drums ......................................................................................... 88
4.1 Introduction .............................................................................................................. 89
4.2 Specimen Geometry and Materials .......................................................................... 90
4.3 Experimental Equipment and Test Procedures ........................................................ 91
4.4 Mechanical Properties of Tested Materials ............................................................. 92
4.5 Fatigue Test Results and Discussion ....................................................................... 94
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4.5.1 Isothermal low Cycle Fatigue Tests .................................................................. 94
4.5.1.1 Universal Slopes Method (USM) for ILCF ...................................................... 97
4.5.2 Thermal-Mechanical Fatigue Tests ................................................................. 100
4.5.2.1 Universal Slopes Method (USM) for TMF ..................................................... 102
4.5.3 Comparison of ILCF and TMF lives .............................................................. 103
4.5.4 Comparison to API Survey Data..................................................................... 104
4.6 Conclusions ............................................................................................................ 106
References ....................................................................................................................... 108
CHAPTER 5 A Fatigue Life Prediction Method for Coke Drum Base,
Weld, and HAZ Materials from Tensile Properties ...................... 110
5.1 Introduction ............................................................................................................ 111
5.2 Specimen Geometry and Materials ........................................................................ 112
5.3 Experimental Setup and Procedures ...................................................................... 114
5.4 Mechanical Properties and Microstructures .......................................................... 114
5.5 Fatigue Test Results and Discussion ..................................................................... 120
5.5.1 Proposed Fatigue Life Method ........................................................................ 126
5.6 Conclusions ............................................................................................................ 134
References ....................................................................................................................... 135
CHAPTER 6 Temperature-Dependent Fatigue Life Prediction
Method for Coke Drum Materials .................................................. 139
6.1 Introduction ............................................................................................................ 140
6.2 Specimen and Materials ......................................................................................... 142
6.3 Experimental Equipment and Procedures .............................................................. 143
6.4 Mechanical Properties............................................................................................ 144
6.5 Fatigue Life Results ............................................................................................... 145
6.6 Review of Fatigue Life Prediction Methods .......................................................... 146
6.6.1 Four-Point Correlation Method (FPCM) ........................................................ 146
6.6.2 Universal Slope Method (USM) ..................................................................... 147
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6.6.3 Modified Universal Slope Method (MUSM) .................................................. 147
6.6.4 Method Proposed by Socie et al (MPS) .......................................................... 148
6.6.5 Uniform Material Law Method (UMLM) ....................................................... 148
6.6.6 Modified Four-Point Correlation Method (MFPCM) ..................................... 149
6.6.7 Median Method (MM) .................................................................................... 150
6.7 Evaluation of the Reviewed Methods .................................................................... 150
6.8 Development of Temperature Dependent Four Point Correlation Method
(TDFPCM) ...................................................................................................................... 154
6.9 Conclusions ............................................................................................................ 159
References ....................................................................................................................... 160
CHAPTER 7 Experimental Evaluation of Fatigue Life of Coke Drum
Materials with Weld Sections .......................................................... 164
7.1 Introduction ............................................................................................................ 165
7.2 Specimen Preparation and Materials ..................................................................... 166
7.3 Experimental Setup and Procedures ...................................................................... 168
7.4 Test Results and Discussion .................................................................................. 168
7.5 FEA and Comparison with Experiments ............................................................... 172
7.5.1 FEA Model Setup ........................................................................................... 172
7.5.2 FEA Results . 173
7.6 Conclusions ............................................................................................................ 176
References ....................................................................................................................... 177
CHAPTER 8 Investigation on the Effect of Weld Yield Strength on
the Fatigue Life of Clad Shell Structure of Coke Drums .............. 179
8.1 Introduction ............................................................................................................ 180
8.2 Structural Specimen Design and Materials ............................................................ 181
8.3 Experimental Setup and Procedures ...................................................................... 184
8.4 Test Results and Discussion .................................................................................. 185
8.5 Finite Element Analysis and Discussion ............................................................... 189
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