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.

Fatigue and Burst Analysis of Hy-140(T) Steel Pressure Vessels

1970 ◽  
Vol 92 (1) ◽  
pp. 11-16 ◽  
Author(s):  
J. M. Barsom ◽  
S. T. Rolfe
Keyword(s):  
Yield Strength ◽  
Pressure Vessel ◽  
Low Cycle Fatigue ◽  
High Strength Steels ◽  
High Strength ◽  
Fatigue Tests ◽  
Pressure Vessels ◽  
High Yield ◽  
Corrosion Properties ◽  
Burst Analysis

Increasing use of high-strength steels in pressure-vessel design has resulted from emphasis on decreasing the weight of pressure vessels for certain applications. To demonstrate the suitability of a 140-ksi yield strength steel for use in unwelded pressure vessels, HY-140(T)—a quenched and tempered 5Ni-Cr-Mo-V steel—was fabricated and subjected to various burst and fatigue tests, as well as to various laboratory tests. In general, results of the investigation indicated very good tensile, Charpy, Nil Ductility Transition Temperature (NDT), low-cycle fatigue, and stress-corrosion properties of HY-140(T) steels, as well as very good burst tests results, in comparison with existing high-yield strength pressure-vessel steels. The results also indicate that the HY-140(T) steel should be an excellent material for its originally designed purpose, Naval hull applications.

Stress and Fatigue Life Modeling of Cannon Breech Closures Including Effects of Material Strength and Residual Stress

2000 ◽  
Vol 123 (1) ◽  
pp. 150-154
Author(s):  
John H. Underwood ◽  
Michael J. Glennon
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Fatigue Life ◽  
Yield Strength ◽  
Residual Stresses ◽  
Solid Mechanics ◽  
Element Model ◽  
Pressure Vessels ◽  
Material Strength ◽  
Element Analysis

Laboratory fatigue life results are summarized from several test series of high-strength steel cannon breech closure assemblies pressurized by rapid application of hydraulic oil. The tests were performed to determine safe fatigue lives of high-pressure components at the breech end of the cannon and breech assembly. Careful reanalysis of the fatigue life tests provides data for stress and fatigue life models for breech components, over the following ranges of key parameters: 380–745 MPa cyclic internal pressure; 100–160 mm bore diameter cannon pressure vessels; 1040–1170 MPa yield strength A723 steel; no residual stress, shot peen residual stress, overload residual stress. Modeling of applied and residual stresses at the location of the fatigue failure site is performed by elastic-plastic finite element analysis using ABAQUS and by solid mechanics analysis. Shot peen and overload residual stresses are modeled by superposing typical or calculated residual stress distributions on the applied stresses. Overload residual stresses are obtained directly from the finite element model of the breech, with the breech overload applied to the model in the same way as with actual components. Modeling of the fatigue life of the components is based on the fatigue intensity factor concept of Underwood and Parker, a fracture mechanics description of life that accounts for residual stresses, material yield strength and initial defect size. The fatigue life model describes six test conditions in a stress versus life plot with an R2 correlation of 0.94, and shows significantly lower correlation when known variations in yield strength, stress concentration factor, or residual stress are not included in the model input, thus demonstrating the model sensitivity to these variables.

Kendall Analysis of Cannon Pressure Vessels

2012 ◽  
Author(s):  
John H. Underwood
Keyword(s):  
Fatigue Life ◽  
Yield Strength ◽  
Pressure Vessel ◽  
Structural Integrity ◽  
Pressure Vessels ◽  
Full Scale ◽  
Compressive Yield Strength ◽  
Us Army ◽  
Post Test ◽  
Engineering Mechanics

Engineering mechanics analysis of cannon pressure vessels is described with special emphasis on the work of the late US Army Benet Laboratories engineer David P. Kendall. His work encompassed a broad range of design and analysis of high pressure vessels for use as cannons, including analysis of the limiting yield pressure for vessels, the autofrettage process applied to thick vessels, and the fatigue life of autofrettaged cannon vessels. Mr. Kendall’s work has become the standard approach used to analyze the structural integrity of cannon pressure vessels at the US Army Benet Laboratories. The methods used by Kendall in analysis of pressure vessels were simple and direct. He used classic results from research in engineering mechanics to develop descriptive expressions for limiting pressure, autofrettage residual stresses and fatigue life of cannon pressure vessels. Then he checked the expressions against the results of full-scale cannon pressure vessel tests in the proving grounds and the laboratory. Three types of analysis are described: [i] Yield pressure tests of cannon sections compared with a yield pressure expression, including in the comparison post-test yield strength measurements from appropriate locations of the cannon sections; [ii] Autofrettage hoop residual stress measurements by neutron diffraction in cannon sections compared with expressions, including Bauschinger corrections in the expressions to account for the reduction in compressive yield strength near the bore of an autofrettaged vessel; [iii] Fatigue life tests of cannons following proving ground firing and subsequent laboratory simulated firing compared with Paris-based fatigue life expressions that include post-test metallographic determination of the initial crack size due to firing. Procedures are proposed for Paris life calculations for bore-initiated fatigue affected by crack-face pressure and notch-initiated cracking in which notch tip stresses are significantly above the material yield strength. The expressions developed by Kendall and compared with full-scale cannon pressure vessel tests provide useful first-order design and safety checks for pressure vessels, to be followed by further engineering analysis and service simulation testing as appropriate for the application. Expressions are summarized that are intended for initial design calculations of yield pressure, autofrettage stresses and fatigue life for pressure vessels. Example calculations with these expressions are described for a hypothetical pressure vessel.

Low Cycle Fatigue Properties of 316LN Stainless Steel Welded by GTAW in Nitrogen Added Environment

2007 ◽  
Vol 345-346 ◽  
pp. 275-278
Author(s):  
Dae Whan Kim ◽  
Chang Hee Han ◽  
Woo Seog Ryu
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Yield Strength ◽  
Base Metal ◽  
Weld Joint ◽  
Low Cycle Fatigue ◽  
Ferrite Content ◽  
Fatigue Properties ◽  
316Ln Stainless Steel ◽  
Type 316Ln Stainless Steel

Tensile and fatigue properties were evaluated for base and welded type 316LN stainless steel. Welding methods were GTAW (308L, Ar environment) and GTAWN (316L, Ar + N2 environment). Yield strength of weld joint was higher than that of base metal but elongation of weld joint was lower than that of base metal. UTS of weld joint was slightly lower than that of base metal. Yield strength and elongation with welding method were almost same. Fatigue life of weld joint was lower than that of base metal but fatigue strength of weld joint was higher than that of base metal. Ferrite content was increased with welding. Fatigue life welded by GTAWN was better than that of GTAW at RT and 600°C. This fatigue life behavior was consistent with the behavior of ferrite content.

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.

Microstructural Characterization of Base Material and Welded Joints of Serviced and Non-Serviced Coke Drums

2018 ◽  
Author(s):  
S. A. Romo ◽  
D. Barborak ◽  
J. Bedoya ◽  
J. Penso ◽  
A. J. Ramirez
Keyword(s):  
Oil And Gas ◽  
Elevated Temperatures ◽  
Prolonged Exposure ◽  
Low Cycle Fatigue ◽  
Base Material ◽  
Microstructural Characterization ◽  
Oil And Gas Industry ◽  
Pressure Vessels ◽  
Carbide Formation ◽  
Circumferential Welds

Coke drums are massive pressure vessels used in the oil and gas industry, which are subjected to demanding cyclic thermomechanical loading. Such conditions generate severe plastic deformation that leads to bulging and cracking during service due to low-cycle fatigue. The cracks are often repaired in programed maintenance shutdowns, and the repair procedures can be significantly different depending on the organization and failure characteristics. In this work, two types of weld repairs are evaluated after six months of service: (1) a full-excavation crack weld repair, and (2) a partial-excavation crack weld overlay repair. The repair welds were executed on a 1.25Cr-0.5Mo steel coke drum after 20 years of service. This work evaluates the microstructure of the base material, the fabrication circumferential welds, and the weld repairs. The results show that, after prolonged exposure to elevated temperatures, the originally normalized and tempered heat-treated steel microstructure has undergone severe aging. Thermodynamic equilibrium and para-equilibrium calculations were used to determine the carbide formation sequence, and SEM analysis was used to characterize the carbides present on the as-fabricated and aged microstructures. Analysis of the repaired regions did not reveal new cracks.

Prediction of the Low Cycle Fatigue Life of Pressure Vessels

1967 ◽  
Vol 89 (4) ◽  
pp. 858-868 ◽  
Author(s):  
A. G. Pickett ◽  
S. C. Grigory
Keyword(s):  
Fatigue Life ◽  
Stress Analysis ◽  
Pressure Vessel ◽  
Low Cycle Fatigue ◽  
Design Procedure ◽  
Pressure Vessels ◽  
Analysis Method ◽  
Notch Stress ◽  
Fatigue Life Analysis ◽  
Fatigue Evaluation

The bases for ASME Boiler and Pressure Vessel Code, Section III, fatigue evaluation procedures, the fracture mechanics approach to fatigue life analysis, and the notch stress analysis method are reviewed. Fatigue life predictions are compared with the results of materials, model, and full size pressure vessel tests performed for PVRC and AEC. These tests were made in response to the research objectives established by ASME Special Committee to Review Code Stress Basis in 1958. A proposed design procedure based on the notch stress analysis method and experimental results is presented.

scholarly journals Influence of Friction Stir Processing on Mechanical Behavior of 2507 SDSS

Metals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 369 ◽  
Author(s):  
Hafiz M. Abubaker ◽  
Necar Merah ◽  
Fadi A. Al-Badour ◽  
Jafar Albinmousa ◽  
Ahmad A. Sorour
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Stainless Steel ◽  
Corrosion Resistance ◽  
Fatigue Life ◽  
Duplex Stainless Steel ◽  
Friction Stir Processing ◽  
Base Material ◽  
Pressure Vessels ◽  
Friction Stir

Duplex stainless steel (DSS) is used for desalination equipment, pressure vessels, marine applications, offshore applications, and in oil/gas plants where a highly corrosive environment is present. Super duplex stainless steel (SDSS) 2507 has excellent mechanical properties, such as high strength, high toughness, high fatigue life, and high corrosion resistance. Friction stir processing (FSP) is used to refine the grain structure of the processed region such that properties like strength, hardness, fracture toughness, fatigue life, and corrosion resistance are enhanced. In this paper, an optimized friction stir process of 2507 SDSS is carried out to refine the microstructure of the material in order to improve its mechanical properties. Microstructure analysis revealed that grains were refined from a size of around 160 µm in the base material to 2–30 µm in the processed zone. This grain size reduction resulted in improved strength, hardness, and fracture toughness of the material by up to 14%, 11%, and 12%, respectively. However, FSP has reduced the fracture strain by about 30%.

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