Experimental Investigation of Coke Drum Material Behavior Under Complex Thermal-Mechanical Loading

2011 ◽  
Author(s):  
Jie Chen ◽  
Zihui Xia
Keyword(s):  
Experimental Investigation ◽  
Mechanical Stress ◽  
Mechanical Loading ◽  
Axial Stress ◽  
Circumferential Stress ◽  
Pressure Vessels ◽  
Material Behavior ◽  
Damage Mechanisms ◽  
Delayed Coking ◽  
Stress Cycling

Coke drums are vertical pressure vessels used in the delayed coking process in petroleum refineries and oil sands plants. Significant temperature variation during the delayed coking process causes damage in coke drums in the form of bulging and cracking. In order to better understand the damage mechanisms, an experimental investigation of coke drum material behavior under various thermal-mechanical loading conditions was performed. A thermal-mechanical material testing system is successfully designed and implemented. Six types of various thermal-mechanical cyclic tests were performed: 1. cyclic thermal loading under constant uniaxial stress; 2. in-phase thermal and mechanical stress cycling; 3. out-of-phase thermal and mechanical stress cycling; 4. fully-reversed uniaxial cyclic loading with in-phase thermal cycling; 5. in-phase thermal-axial stress cycling with constant circumferential stress; 6. in-phase thermal-axial stress cycling with mean stress. Some of theses tests are similar to the actual loading scenario experienced by the coke drums. The experimental findings lead to better understanding of the damage mechanisms occurring in coke drums such as bulging.

Experimental Evaluation of Fatigue Life of Coke Drum Materials With Weld Sections

2013 ◽  
Author(s):  
Jie Chen ◽  
Toshiya Yamamoto ◽  
Zihui Xia ◽  
Keiji Esaki
Keyword(s):  
Fatigue Life ◽  
Yield Strength ◽  
Experimental Evaluation ◽  
Low Cycle Fatigue ◽  
Base Material ◽  
Pressure Vessels ◽  
Damage Mechanisms ◽  
Delayed Coking ◽  
Different Types ◽  
Petroleum Refineries

Coke drums are vertical pressure vessels used in the delayed coking process in petroleum refineries. Significant temperature variation during the delayed coking process causes damage in coke drums in the form of bulging and cracking. It was also observed that most cracks were near or within the weld seams. In order to better understand fatigue damage mechanisms of the coke drum materials with their weld sections, an experimental investigation of fatigue lives of these materials are carried out. It is a common consideration that the yield strength of the weld should be within a close percentage to that of base material in order to keep strength uniformity throughout the drum shell sections. However, this effect of the yield strength matching on the shell durability has not yet clarified quantitatively. From this point of view, two different types of specimens have been designed and manufactured: base material only, base with base weld. In addition, three groups of base with weld materials with different ratios of weld to base yield strengths are prepared. Low cycle fatigue tests at elevated temperature of 250°C are carried out on the above specimens. Through study on the recorded stress-strain hysteresis loops and observation on the fracture surfaces, damage mechanisms of different types of specimens are analyzed. Their strain range–fatigue life curves are also compared. Furthermore, finite element analyses based on the actual specimens’ geometries and properties are conducted to help in understanding the experimental observations. This experimental evaluation of fatigue life of coke drum materials with welds may provide a good reference for better design of coke drums in the future.

scholarly journals Thermoelastic analysis of FGM hollow cylinder for variable parameters and temperature distributions using FEM

2020 ◽  
Vol 9 (1) ◽  
pp. 256-264
Author(s):  
Dinkar Sharma ◽  
Ramandeep Kaur
Keyword(s):  
Stress Field ◽  
Hollow Cylinder ◽  
Numerical Study ◽  
Axial Stress ◽  
Circumferential Stress ◽  
Functionally Graded ◽  
Gradient Index ◽  
Variable Parameters ◽  
Graded Material ◽  
Governing Differential Equation

AbstractThis paper presents, numerical study of stress field in functionally graded material (FGM) hollow cylinder by using finite element method (FEM). The FGM cylinder is subjected to internal pressure and uniform heat generation. Thermoelastic material properties of FGM cylinder are assumed to vary along radius of cylinder as an exponential function of radius. The governing differential equation is solved numerically by FEM for isotropic and anistropic hollow cylinder. Additionally, the effect of material gradient index (β) on normalized radial stresses, normalized circumferential stress and normalized axial stress are evaluated and shown graphically. The behaviour of stress versus normalized radius of cylinder is plotted for different values of Poisson’s ratio and temperature. The graphical results shown that stress field in FGM cylinder is influenced by some of above mentioned parameters.

Thermo-Elasto-Plastic Analysis of Thick-Walled Spherical Pressure Vessels Made of Functionally Graded Materials

2016 ◽  
Vol 08 (04) ◽  
pp. 1650054 ◽  
Author(s):  
Zeinab Mazarei ◽  
Mohammad Zamani Nejad ◽  
Amin Hadi
Keyword(s):  
Heat Flux ◽  
Functionally Graded Materials ◽  
Poisson’S Ratio ◽  
Pressure Vessels ◽  
Functionally Graded ◽  
Material Behavior ◽  
Poisson's Ratio ◽  
Uniform Heat Flux ◽  
Plastic Behavior ◽  
Graded Materials

An exact closed-form analytical solution is presented to solve the thermo-elasto-plastic problem of thick-walled spherical vessels made of functionally graded materials (FGMs). Assuming that the inner surface is exposed to a uniform heat flux, and that the outer surface is exposed to an airstream. The heat conduction equation for the one-dimensional problem in spherical coordinates is used to obtain temperature distribution in the sphere. Material properties are graded in the thickness direction according to a power law distribution, whereas the Poisson’s ratio is kept constant. The Poisson’s ratio due to slight variations in engineering materials is assumed constant. The plastic model is based on von Mises yield criterion and its associated flow rules under the assumption of perfectly plastic material behavior. For various values of inhomogeneity constant, the so-obtained solution is then used to study the distribution of limit heat flux, displacement and stresses versus the radial direction. Moreover, the effect of increasing the heat flux and pressure on the propagation of the plastic zone are investigated. Furthermore, the effect of change in Poisson’s ratio on the value of the critical material parameter is demonstrated. The present study is also validated by comparing the numerical results for thick elasto-plastic spherical shells available in the literature. To the best of the authors’ knowledge, in previous studies, exact thermo-elasto-plastic behavior of FGM thick-walled sphrical pressure vessels has not investigated.

Influence of Cyclic Loading on Mechanical Loosening of Hinged Knee Prostheses

1978 ◽  
Vol 7 (4) ◽  
pp. 235-239 ◽  
Author(s):  
D. H. van Campen ◽  
H. W. Croon ◽  
J. Lindwer
Keyword(s):  
Experimental Investigation ◽  
Cyclic Loading ◽  
Mechanical Loading ◽  
Knee Prosthesis ◽  
In Vitro Experiments ◽  
Knee Prostheses ◽  
Normal Walking ◽  
Fresh Cadaver ◽  
Unfavourable Effect

A combined theoretical and experimental investigation is reported with respect to the influence of mechanical loading on loosening at the cement bone interface of knee prostheses with intermedullary stems. The in vitro experiments have been performed under cyclic loading conditions with the tibial part of a Shiers knee prosthesis implanted in fresh cadaver tibiae. The experimental results indicate an unfavourable effect of peak loading (as occurring in walking up stairs) on loosening as compared with loading due to normal walking conditions.

Investigation of Fracture in Transparent Glass Fiber Reinforced Polymer Composites Using Photoelasticity

2002 ◽  
Author(s):  
Sanjeev K. Khanna ◽  
Marius D. Ellingsen ◽  
Robb M. Winter
Keyword(s):  
Composite Materials ◽  
Fatigue Cracks ◽  
Large Body ◽  
Mechanical Analysis ◽  
Pressure Vessels ◽  
High Ratio ◽  
Material Behavior ◽  
Engineering Structures ◽  
Glass Fiber Reinforced ◽  
Fiber Reinforced Polymer Composites

Composite materials are widely used in mechanical structures where a high ratio of strength or stiffness to weight is desired. Not only are composite materials widely used in building recreational equipment such as skis, snowboards or even sports cars, but also multiple types of military aircraft are built from composite materials. Airplane bodies are in principle cyclically loaded pressure vessels and are susceptible to the formation of fatigue cracks, and it is necessary to possess knowledge of how the material behaves with a crack present. In fact, all engineering structures have to be designed with the presence of crack like defects in mind. For traditional engineering materials such as steel and aluminum there exists a large body of knowledge regarding material behavior in the presence of a crack. Furthermore, their isotropic nature eases the process of mechanical analysis. Photoelasticity, an optical method, has been widely used to study fracture in isotropic transparent materials (Irwin, 1962, 1980; Dally, 1979; Daniel, 1984; Kobayashi, et al, 1973; Chona, 1987).

X-ray residual stress analysis of cylindrically curved surfaces—estimation of circumferential distributions of residual stresses

2003 ◽  
Vol 38 (5) ◽  
pp. 459-468 ◽  
Author(s):  
T Oguri ◽  
K Murata ◽  
Y Sato
Keyword(s):  
Residual Stresses ◽  
Least Squares Method ◽  
Stress Measurement ◽  
Incident Angle ◽  
Axial Stress ◽  
Circumferential Stress ◽  
Distribution Functions ◽  
Scanning Method ◽  
X Ray ◽  
Reference Axis

A new measuring technique utilizing X-ray diffraction is proposed in order to estimate the circumferential distributions of residual stresses on convex/concave cylindrical surfaces. This technique requires neither tilting X-ray beams in the circumferential direction in which the X-ray incident angle tends to be limited nor adjusting the normal of the irradiation area to the reference axis of the ψ angle. The circumferential distributions of the circumferential stress and of the axial stress are estimated from the diffraction angles at ψ = 0° and the axial stresses obtained by the stress measurement on multiple inclined areas on the cylindrical surfaces under the configuration of the axial stress measurement using the iso-inclination scanning method. This estimate technique was applied to two round bars of steel, one with circumferential distributions of the residual stresses and the other with almost uniform stresses. The distribution functions of the residual stresses were expanded to a couple of Fourier series, and the coefficients of them were determined by the least-squares method. The estimated distributions of the residual stresses were in good agreement with the actual ones.

Failures of Pressure Vessels and Process Piping

2021 ◽  
pp. 565-637
Author(s):  
Luis A. Ganhao ◽  
Jorge J. Perdomo ◽  
James McVay ◽  
Antonio Seijas
Keyword(s):  
Failure Analysis ◽  
Power Plants ◽  
Pressure Vessels ◽  
Chemical Processing ◽  
Damage Mechanisms ◽  
Process Piping ◽  
Processing Plants

Abstract This article discusses pressure vessels, piping, and associated pressure-boundary items of the types used in nuclear and conventional power plants, refineries, and chemical-processing plants. It begins by explaining the necessity of conducting a failure analysis, followed by the objectives of a failure analysis. Then, the article discusses the processes involved in failure analysis, including codes and standards. Next, fabrication flaws that can develop into failures of in-service pressure vessels and piping are covered. This is followed by sections discussing in-service mechanical and metallurgical failures, environment-assisted cracking failures, and other damage mechanisms that induce cracking failures. Finally, the article provides information on inspection practices.

TOFD Automatic Ultrasonic Testing for Condition Monitoring of Coke Drums

2003 ◽  
Author(s):  
Jorge A. Penso ◽  
Robert Owen ◽  
Masaaki Oka
Keyword(s):  
Condition Monitoring ◽  
Ultrasonic Testing ◽  
Phased Array ◽  
Service Evaluation ◽  
Pressure Vessels ◽  
Inspection System ◽  
Delayed Coking ◽  
Advantages And Disadvantages ◽  
Mechanical Cycling ◽  
History Of

Cracking and bulging in welded and internally lined pressure vessels that work in thermal-mechanical cycling service have been well known problems in the petrochemical, power and nuclear industries. In spite of this problem has been studied during the last fifty years, published literature and industry surveys show that similar problems still occur nowadays. Typical examples of this problem are the coke drums in the delayed coking units refinery process. Delayed coking units are among the refinery units that have higher economical yields. To shut down these units represents a high negative economical impact in refinery operations. Also, the maintenance costs associated with repairs are commonly very high. Cracking and bulging occurrences in the coke drums, most often at the weld areas, characterize the history of the operation of delayed coking units. To anticipate through wall cracking in these coke drums, AUT (automatic ultrasonic testing); Dual TOFD (time of flight diffraction) and the Phased Array technique simultaneous inspection system was selected among other inspection techniques as a condition monitoring tool during an unit turnaround. The inspection methodology in combination with fracture mechanics was used to classify discontinuities as acceptable and non-acceptable. This indicated approach helped to optimize the workscope during the turnaround and establish guidelines for inspection and repair of the delayed coker unit. This work presents the different steps followed during the inspection and fitness for service evaluation. Also, this study shows advantages and disadvantages of the AUT-Phased Array technique.

Investigation of Residual Stress Development During Swage Autofrettage, Using Finite Element Analysis

2009 ◽  
Author(s):  
Michael C. Gibson ◽  
Amer Hameed ◽  
John G. Hetherington
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Axial Stress ◽  
Slope Angle ◽  
Subsequent Development ◽  
Element Model ◽  
Pressure Vessels ◽  
Element Analysis ◽  
Reverse Yielding

Swaging is one method of autofrettage, a means of pre-stressing high-pressure vessels to increase their fatigue lives and load bearing capacity. Swaging achieves the required deformation through physical interference between an oversized mandrel and the bore diameter of the tube, as it is pushed through the tube. A Finite Element model of the swaging process was developed, in ANSYS, and systematically refined, to investigate the mechanism of deformation and subsequent development of residual stresses. A parametric study was undertaken, of various properties such as mandrel slope angle, parallel section length and friction coefficient. It is observed that the axial stress plays a crucial role in the determination of the residual hoop stress and reverse yielding. The model, and results obtained from it, provides a means of understanding the swaging process and how it responds to different parameters. This understanding, coupled with future improvements to the model, potentially allows the swaging process to be refined, in terms of residual stresses development and mandrel driving force.

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