Analysis of the Influence of the Cooling Patterns and the Shape of the Bulges on the Levels of Stress in the Cylindrical Section of Delayed Coke Drums

2018 ◽  
Author(s):  
Gabriel A. Vivas ◽  
Armando J. Moret ◽  
Roberto E. Bello ◽  
Luis M. Melian ◽  
Julian J. Bedoya
Keyword(s):  
Laser Scanning ◽  
Thermal Loading ◽  
Low Cycle Fatigue ◽  
Pressure Vessels ◽  
Transient Temperature ◽  
Thermal Gradients ◽  
Cooling Rates ◽  
Area Of Interest ◽  
Stress Levels ◽  
Cyclic Changes

Coke drums are thin-walled pressure vessels that experience low cycle fatigue due to thermal loadings. The delayed coking process is comprised by three major stages: heating, coking and cooling, which repeat at intervals between 20 and 48 hours. The cyclic changes of temperature increase the growth of bulges and cracks which with the passing of time, propagate and eventually cause failures due to the loss of containment. A better understanding of the phenomena of the thermal gradients and their influence on the generated stresses would reduce the effects of the damage mechanisms afflicting coke drums, for example; a continuous monitoring system could be implemented in order to control the cooling ramp to obtain a more homogeneous quenching around the cylinder of the coke drum and consequently increase its lifetime. It is been widely accepted that there is a relationship between high cooling rates in isolated zones and high axial stresses. However, this relationship has not been fully validated, since there are also been reported events of low cooling rates and high stresses. This study shows a predictable behavior (trend) that relates the spatial thermal gradients and the axial and circumferential stresses generated. A coke drum in an upgrader facility was instrumented with two arrays or grids, each of them having 24 thermocouples and 2 strain gauges in zones with distinct bulges. One arrangement was located at an inward bulge while the other was located at an outward bulge. Computational models were carried out to reproduce the behavior of the instrumented zones with their actual deformations obtained from laser scanning. Finite element models were developed using a sequentially coupled thermo-mechanical analysis to determine the transient temperature and stress distributions. The effect of the circumferential thermal gradients on the stress levels in the instrumented cylindrical sections were analyzed, considering two cases; the first of them a perfect cylinder (without deformation) and the second one considering the presence of bulges in the area of interest. The results indicate that there is a relationship between the circumferential thermal gradients [°C/m] or [°F/ft] and the axial stress levels, i.e., cold zones generate axial tensile stresses, and hot zones produce compressive axial stresses. This relationship is affected — exacerbated or counteracted — by the presence of the bulges. Additionally, the results obtained in this paper confirm those of previous investigations showing that outward bulges subject to pressure and thermal loading generate high stresses on its internal surface and low stresses on its external face whereas inward bulges produce the opposite effect.

Random impact FEM simulation of irregularly-shaped media for parametric study of vibratory surface enhancement

2021 ◽  
pp. 095440542199012
Author(s):  
Jing Zhang ◽  
Joselito Yam Alcaraz ◽  
Swee-Hock Yeo ◽  
Arun Prasanth Nagalingam ◽  
Abhay Gopinath
Keyword(s):  
Residual Stress ◽  
Fatigue Life ◽  
Parametric Study ◽  
Thermal Loading ◽  
Low Cycle Fatigue ◽  
Fem Simulation ◽  
Surface Finishing ◽  
Aerospace Materials ◽  
Surface Enhancement ◽  
Steel Balls

Aerospace materials experience high levels of mechanical and thermal loading, high/low cycle fatigue, and damage from foreign objects during service, which can lead to premature retirement. Mechanical surface treatments of metallic components, for example, fan blades and blisks, are proven to improve fatigue life, improve wear resistance and avoid stress corrosion by introducing work hardening, compressive residual stresses of sub-surface, and surface finishing. Vibropeening can enhance aerospace materials’ fatigue life involving the kinetic agitation of hardened steel media in a vibratory finishing machine that induces compressive stresses into the component sub-layers while keeping a finished surface. Spherical steel balls are the most widely used shape among steel-based media and have been explored for decades. However, they are not always versatile, which cannot access deep grooves, sharp corners, and intricate profiles. Steel ballcones or satellites, when mixed with round steel balls and other steel media (diagonals, pins, eclipses, cones), works very well in such areas that ball-shaped media are unable to reach. However, a methodology of study the effect of irregularly-shaped media in surface enhancement processes has not been established. This paper proposes a finite element-based model to present a methodology for the parametric study of vibratory surface enhancement with irregularly-shaped media and investigates residual stress profiles within a treated area of an Inconel component. The methodology is discussed in detail, which involves a stochastic simulation of orientation, impact force, and impact location. The contrasting effects of a high aspect ratio, or an edge contact, as opposed to rounded and oblique contacts are demonstrated, with further analysis on the superposition of these effects. Finally, the simulation results are compared with actual residual stress measurements and was found to have a max percent difference of 34% up to 20 [Formula: see text]m below the media surface.

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.

An alternative way to support horizontal pressure vessels subject to thermal loading

1998 ◽  
Vol 75 (8) ◽  
pp. 617-623 ◽  
Author(s):  
Alwyn S. Tooth ◽  
John S.T. Cheung ◽  
Heong W. Ng ◽  
Lin S. Ong ◽  
Chithranjan Nadarajah
Keyword(s):  
Thermal Loading ◽  
Pressure Vessels ◽  
Horizontal Pressure

Thermomechanical Fatigue Behavior of Bare and Coated CMSX-4

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
T. Coppola ◽  
S. Riscifuli ◽  
O. Tassa ◽  
G. Pasquero
Keyword(s):  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Turbine Blades ◽  
Thermomechanical Fatigue ◽  
Tensile Creep ◽  
Thermal Gradients ◽  
Test Program ◽  
Complete Set ◽  
Comparison Of The Results ◽  
Very High

Highly cooled turbine blades undergo very high thermal gradients during rapid engine idle-max-idle cycling. Traditional isothermal fatigue data are often insufficient for predicting service lives. A complete set of high temperature tests, in the range of 750–1050°C, was performed on single crystal alloy CMSX-4. The test program comprised tensile, creep, low cycle fatigue, and thermomechanical fatigue (TMF) tests. In particular the cycle time for TMF was 3 min, aiming to simulate the real high-power transient conditions in aircraft engines. Clockwise and counterclockwise diamond cycle types were applied on bare and coated specimens to investigate their influence on the fatigue limit. The comparison of the results obtained with the available ones from open literature is discussed.

Design of Pressure Vessels for Low-Cycle Fatigue

1962 ◽  
Vol 84 (3) ◽  
pp. 389-399 ◽  
Author(s):  
B. F. Langer
Keyword(s):  
Fatigue Strength ◽  
Pressure Vessel ◽  
Low Cycle Fatigue ◽  
Fatigue Curve ◽  
Pressure Vessels ◽  
Reduction Factor ◽  
Strength Reduction ◽  
Strength Reduction Factor ◽  
The Mean ◽  
Fatigue Evaluation

Methods are described for constructing a fatigue curve based on strain-fatigue data for use in pressure vessel design. When this curve is used, the same fatigue strength-reduction factor should be used for low-cycle as for high-cycle conditions. When evaluating the effects of combined mean and alternating stress, the fatigue strength-reduction factor should be applied to both the mean and the alternating component, but then account must be taken of the reduction in mean stress which can be produced by yielding. The complete fatigue evaluation of a pressure vessel can be a major task for the designer, but it can be omitted, or at least drastically reduced, if certain requirements can be met regarding design details, inspection, and magnitude of transients. Although the emphasis in this paper is on pressure vessel design, the same principles could be applied to any structure made of ductile metal and subjected to limited numbers of load cycles.

Optimizing Probe Active Aperture for Phased Array Weld Inspections

2021 ◽  
Vol 79 (8) ◽  
pp. 797-804
Author(s):  
Anmol Birring
Keyword(s):  
Fracture Mechanics ◽  
Ultrasonic Testing ◽  
Phased Array ◽  
Pressure Vessels ◽  
Acceptance Criteria ◽  
Nondestructive Technique ◽  
Cross Sectional ◽  
Area Of Interest ◽  
Array Technology ◽  
Selection Of

Phased array ultrasonic testing (PAUT) has become a popular nondestructive technique for weld inspections in piping, pressure vessels, and other components such as turbines. This technique can be used both in manual and automated modes. PAUT is more attractive than conventional angle-beam ultrasonic testing (UT), as it sweeps the beam through a range of angles and presents a cross-sectional image of the area of interest. Other displays are also available depending on the software. Unlike traditional A-scan instruments, which require the reconstruction of B- and C-scan images from raster scanning, a phased array image is much simpler to produce from line scans and easier to interpret. Engineering codes have incorporated phased array technology and provide steps for standardization, scanning, and alternate acceptance criteria based on fracture mechanics. The basis of fracture mechanics is accurate defect sizing. There is, however, no guidance in codes and standards on the selection and setup of phased array probes for accurate sizing. Just like conventional probes, phased array probes have a beam spread that depends on the probe’s active aperture and frequency. Smaller phased array probes, when used for thicker sections, result in poor focusing, large beam spread, and poor discontinuity definition. This means low resolution and oversizing. Accurate sizing for fracture mechanics acceptance criteria requires probes with high resolution. In this paper, guidance is provided for the selection of phased array probes and setup parameters to improve resolution, definition, and sizing of discontinuities.

Modeling, Simulation and Experimental Validation of Heat Transfer During Selective Laser Melting

2015 ◽  
Author(s):  
Mohammad Masoomi ◽  
Xiang Gao ◽  
Scott M. Thompson ◽  
Nima Shamsaei ◽  
Linkan Bian ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Mechanical Properties ◽  
Selective Laser Melting ◽  
Heat Fluxes ◽  
Transient Temperature ◽  
Thermal Gradients ◽  
Layer By Layer ◽  
Metal Powders ◽  
Laser Melting ◽  
Powder Bed

Selective Laser Melting (SLM), a laser powder-bed fusion (PBF-L) additive manufacturing method, utilizes a laser to selectively fuse adjacent metal powders. The powders are aligned in a bed that moves vertically to allow for layer-by-layer part construction-Process-related heat transfer and thermal gradients have a strong influence on the microstructural features, and subsequent mechanical properties, of the parts fabricated via SLM. In order to understand and control the heat transfer inherent to SLM, and to ensure high quality parts with targeted microstructures and mechanical properties, comprehensive knowledge of the related energy and mass transport during manufacturing is required. In this study, the transient temperature distribution within and around parts being fabricated via SLM is numerically simulated and the results are provided to aid in quantify the SLM heat transfer. In order to verify simulation output, and to estimate actual thermal gradients and heat transfer, experiments were separately conducted within a SLM machine using a substrate with embedded thermocouples. The experiments focused on characterizing heat fluxes during initial deposition on an initially-cold substrate and during the fabrication of a thin-walled structure built via stainless steel 17-4 powders. Results indicate that it is important to model heat transfer thorough powder bed as well as substrate.

Finite Element Analysis of Local Inelastic Strain Based on Stress Redistribution Locus

2008 ◽  
Author(s):  
Shunji Kataoka ◽  
Takuya Sato
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Thermal Loading ◽  
Failure Modes ◽  
Elevated Temperatures ◽  
Pressure Vessels ◽  
Stress Redistribution ◽  
Strain Diagram ◽  
Element Analysis ◽  
Inelastic Analysis

Creep-fatigue damage is one of the dominant failure modes for pressure vessels and piping used at elevated temperatures. In the design of these components the inelastic behavior should be estimated accurately. An inelastic finite element analysis is sometimes employed to predict the creep behavior. However, this analysis needs complicated procedures and many data that depend on the material. Therefore the design is often based on a simplified inelastic analysis based on the elastic analysis result, as described in current design codes. A new, simplified method, named, Stress Redistribution Locus (SRL) method, was proposed in order to simplify the analysis procedure and obtain reasonable results. This method utilizes a unique estimation curve in a normalized stress-strain diagram which can be drawn regardless of the magnitude of thermal loading and constitutive equations of the materials. However, the mechanism of SRL has not been fully investigated. This paper presents results of the parametric inelastic finite element analyses performed in order to investigate the mechanism of SRL around a structural discontinuity, like a shell-skirt intersection, subjected to combined secondary bending stress and peak stress. This investigation showed that SRL comprises a redistribution of the peak and secondary stress components and that although these two components exhibit independent redistribution behavior, they are related to each other.

Influence of Chromium Content and Prior Deformation on the Continuous Cooling Transformation Diagram of Low-Carbon Bainitic Steels

2020 ◽  
Vol 835 ◽  
pp. 58-67
Author(s):  
Mohammed Ali ◽  
Antti J. Kaijalainen ◽  
Jaakko Hannula ◽  
David Porter ◽  
Jukka I. Kömi
Keyword(s):  
Cooling Rate ◽  
Hot Deformation ◽  
Laser Scanning ◽  
Chromium Content ◽  
Bainitic Ferrite ◽  
Granular Bainite ◽  
Low Carbon ◽  
Cooling Rates ◽  
Continuous Cooling Transformation ◽  
Continuous Cooling

The effect of chromium content and prior hot deformation of the austenite on the continuous cooling transformation (CCT) diagram of a newly developed low-carbon bainitic steel has been studied using dilatometer measurements conducted on a Gleeble 3800 simulator with cooling rates ranging from 2-80 °C/s. After austenitization at 1100 °C, specimens were either cooled without strain or given 0.6 strain at 880 °C prior to dilatometer measurements. The resultant microstructures have been studied using laser scanning confocal microscopy, scanning electron microscopy and macrohardness measurements. CCT and deformation continuous cooling transformation (DCCT) diagrams were constructed based on the dilatation curves, final microstructures and hardness values. Depending on the cooling rate, the microstructures of the investigated steels after cooling from the austenite region consist of one or more of the following microstructural components: lath-like upper bainite, i.e. bainitic ferrite (BF), granular bainite (GB), polygonal ferrite (PF) and pearlite (P). The proportion of BF to GB as well as the hardness of the transformation products decreased with decreasing cooling rate. The cooling rate at which PF starts to appear depends on the steel composition. With both undeformed and deformed austenite, increasing the chromium content led to higher hardenability and refinement of the microstructure, promoting the formation of BF and shifting the ferrite start curve to lower cooling rates. Prior hot deformation shifted the transformation curves to shorter times and higher temperatures and led to a reduction in hardness at the low cooling rates through the promotion of ferrite formation.

Use of a CFD-Tool for Assessment of the Reactor Pressure Vessel Integrity in Pressurised Thermal Shock Conditions: Thermal-Hydraulic Studies of a Safety Injection in a PWR Plant — Methodology and Present Limitation

2007 ◽  
Author(s):  
A. Martin ◽  
S. Bosse ◽  
F. Lestang
Keyword(s):  
Heat Transfer ◽  
Thermal Shock ◽  
Thermal Loading ◽  
Development Program ◽  
Pressure Vessels ◽  
Surveillance Program ◽  
Fluid Temperature ◽  
Two Phase ◽  
Safety Margins ◽  
Reactor Pressure

Integrity evaluation methods for nuclear Reactor Pressure Vessels (RPVs) under Pressurised Thermal Shock (PTS) loading are applied by French Utility. They are based on the analysis of the behaviour of cracks under PTS loading conditions due to the emergency cooling during PTS transient like SBLOCA. This paper explains the Research and Development program started at Electricite´ De France about the cooling phenomena of a PWR vessel after a Pressurised Thermal Shock. The numerical results are obtained with the E.D.F ThermalHydraulic code (Code_Saturne) coupled with the thermal-solid code SYRTHES to take into account the conjugate heat transfer on the cooling of the vessel. We first explain the global methodology with a progress report on the state of the art of the tools available to simulate the different scenari displayed within the frame of the plant life project in order to reassess the integrity of the RPV, taking into account the evolution of some input data, such as the new value of end of life (EOL) fluence, the feedback results of surveillance program and the evolution of the functional requirements. The main results are presented and are related to the evaluation of the RPV integrity during a Small Break Loss Of Coolant Accident transient for 900 and 1300 MWe nuclear plant. On the whole, the main purpose of the numerical CFD studies is to accurately estimate the distribution of fluid temperature in the down comer and the heat transfer coefficients on the inner RPV surface for a fracture mechanics computation which will subsequently assess the associated RPV safety margins. In a second time, a new analysis is performed to assess an accurate temperature distribution in the RPV. Indeed, from a physical phenomena point of view, the EDF thermalhydraulic tool Code_Saturne is now qualified in order to assess single phase transient but in the case where the cold legs are partially filled with steam, it becomes a two-phase problem and new important effects occur, such as condensation due to the emergency core cooling injections of sub-cooled water. Thus, an advanced prediction of RPV thermal loading during these transients requires sophisticated two-phase, local scale, 3D codes. In that purpose, a program has been set up to extend the capabilities of the Neptune_CFD two-phase solver which is the tool able to solve two phase flow configuration. In a same time, A simplified approach has showed that for a type of transient weakly uncovered, a free surface calculation was sufficient to respect the necessary criteria of safety. A Qualification study was carried out on the Hybiscus experimental E.D.F facility, representing a cold leg with ECC injection and a third down comer. Temperature profiles have been compared and are presented and analysed here, showing encouraging results.

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