Assessing the Condition and Estimating the Remaining Lives of Pressure Components in a Methanol Plant Reformer: Part 2 — Engineering Evaluation

2016 ◽  
Author(s):  
Carl E. Jaske ◽  
Brian E. Shannon ◽  
Gustavo Miranda ◽  
Thomas J. Prewitt
Keyword(s):  
Finite Element ◽  
Creep Damage ◽  
General Purpose ◽  
Operating Conditions ◽  
Remaining Life ◽  
Creep Life ◽  
Service Failures ◽  
Finite Element Software ◽  
Creep Stress ◽  
Non Destructive

Statoil Tjelbergodden operates a 2,400 ton/day methanol plant in Norway. Part 1 of this paper described the advanced non-destructive examination (NDE) technologies that were applied to obtain data for engineering evaluation of radiant catalyst tubes, outlet pigtails, and outlet collection headers. The inspection results were compiled along with data on materials properties and plant operating conditions for use in a series of life prediction studies. This paper describes the assessment methodologies that were applied in evaluating the remaining life of the in-service components. The special purpose WinTUBE™ finite element software was applied to predict remaining catalyst tube creep life based on the computed creep stress-strain response and creep damage accumulation under simulated future operating conditions. Outlet headers and pigtails were modeled using general purpose finite element software to compute stresses and strains during operation. Following the methodology of API 579-1/ASME FFS-1 the computed stresses and strains were used to predict remaining creep life. Using the remaining life estimates to decrease the potential of in-service failures and increase the reliability of future reformer operations is discussed.

An Investigation on the Effect of Creep Shakedown on the Creep Behavior of an Industrial Gas Turbine Blade

2015 ◽  
Author(s):  
Jun Zhao ◽  
Ashok K. Koul ◽  
Avisekh Banerjee
Keyword(s):  
Finite Element ◽  
Gas Turbine ◽  
Damage Accumulation ◽  
Creep Damage ◽  
Local Stress ◽  
Operating Conditions ◽  
Time Dependent ◽  
Strain Accumulation ◽  
Accumulation Process ◽  
Creep Life

The creep life computation of gas turbine hot section components using any damage modeling technique requires typical inputs of stress and temperature under actual engine operating conditions. The magnitude of these inputs is governed by the static or dynamic transient loading conditions that a component may be subjected to during service. The long term creep damage accumulation process in a hot section component leads to strain accumulation in the component with time. The rate of change of this strain accumulation in different regions of a component is controlled by the magnitude of the local stress, stress gradient and temperature. In some regions, the creep damage accumulation process may lead to a substantial change in the local stress distribution, also called the “Creep Shakedown”, and this time-dependent stress redistribution can have a substantial impact on the component creep life. The creep shakedown based creep life analysis of a GE Frame 7EA first stage turbine blade under off-design base-load engine operating conditions is studied. The evolution of the stress and strain in different regions of the blade with service time was analyzed using the finite element method. A user defined Garofalo model with hyperbolic sine creep rule was incorporated in the finite element analysis (FEA). The creep shakedown in the component is demonstrated to cause a local time-dependent stress redistribution effect in the FEA simulation. The significant stress variation and creep strain accumulation was observed in the creep critical regions where local stress raisers were present and/or a high temperature gradient due to internal cooling design existed. These effects are discussed in detail from a materials engineering perspective.

Optimal Design of the Large-Diameter Spinning Torispherical Head

2012 ◽  
Vol 544 ◽  
pp. 194-199
Author(s):  
Di Zhang ◽  
Shui Ping Sheng ◽  
Zeng Liang Gao
Keyword(s):  
Finite Element ◽  
Optimal Design ◽  
Large Diameter ◽  
General Purpose ◽  
Design Tool ◽  
Crown Area ◽  
Finite Element Software ◽  
The Stability

Two important parameters of torispherical head that are (interior radius of spherical crown area) and r (interior radius of transition corner) have been optimized by the module of the large general-purpose finite-element software ANSYS, targeting the strength and stability of the head. This paper provides an optimized torispherical head, which improves the stability of the edge of the head with acceptable strength of the head. The procedure is generally applicable as a design tool for optimal design.

Numerical Simulation of Inner Support for Excavation Based on FEM Software ABAQUS

2012 ◽  
Vol 236-237 ◽  
pp. 632-635
Author(s):  
Yue Sun ◽  
Yue Nan Chen ◽  
Zhi Yun Wang
Keyword(s):  
Numerical Simulation ◽  
Finite Element ◽  
Computational Model ◽  
Dimensional Space ◽  
General Purpose ◽  
Two Dimensional ◽  
Clay Layer ◽  
Finite Element Software ◽  
Spring Element

In two-dimensional space, an elasto-plastic finite element computational model was established to simulate inner support for excavation on the basis of the general-purpose finite element software ABAQUS. The soil was assumed to be a uniform and normally consolidated clay layer and strut was discreted by spring element. Compared with published case study, it can be concluded that FEM software AQAQUS can present one reliable simulation progress of inner support for excavation.

Creep Life Simulation and Assessment of High Temperature Piping Systems and Components

2012 ◽  
Author(s):  
Brian Rose ◽  
James Widrig
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
High Temperature ◽  
Creep Behavior ◽  
Material Behavior ◽  
Piping System ◽  
Remaining Life ◽  
Creep Life ◽  
Element Analysis ◽  
Piping Systems

High temperature piping systems and associated components, elbows and bellows in particular, are vulnerable to damage from creep. The creep behavior of the system is simulated using finite element analysis (FEA). Material behavior and damage is characterized using the MPC Omega law, which captures creep embrittlement. Elbow elements provide rapid yet accurate modeling of pinching of piping, which consumes a major portion of the creep life. The simulation is used to estimate the remaining life of the piping system, evaluate the adequacy of existing bellows and spring can supports and explore remediation options.

Steel Cofferdam Design and Calculation for High Pile Cap Construction

2011 ◽  
Vol 255-260 ◽  
pp. 1879-1884
Author(s):  
Gui Yun Xia ◽  
Mei Liang Yang ◽  
Chuan Xi Li ◽  
Shang Wu Lu
Keyword(s):  
Finite Element ◽  
Boundary Conditions ◽  
Structural Strength ◽  
General Purpose ◽  
Structural Safety ◽  
Pearl River ◽  
Guangzhou City ◽  
Finite Element Software ◽  
Pile Cap ◽  
Calculating Model

Using the steel cofferdam of Xinzhao Pearl River Bridge in Guangzhou City as the engineering background, structural designing and size proposing of steel cofferdam are introduced briefly. To ensure structural safety, general purpose finite element software Ansys was used to analyze structural strength and stability. Load styles and boundary conditions were also discussed. 6 load cases with calculating model were presented.

Enhanced Creep Life Evaluations for Grade 91 Circumferential Weldments

2017 ◽  
Author(s):  
Marvin J. Cohn
Keyword(s):  
Applied Stress ◽  
Hoop Stress ◽  
Axial Stress ◽  
Creep Damage ◽  
Creep Rupture ◽  
Piping System ◽  
Remaining Life ◽  
Creep Life ◽  
Rupture Properties ◽  
Applied Stresses

The basic power piping creep life calculations consider the important variables of time, temperature and stress for the creep rupture properties of the unique material. Some engineering evaluations of remaining life estimate the applied stress as the design stress obtained from a conventional piping stress analysis. Other remaining life evaluations may assume that a conservative estimate of the applied stress is no greater than the hoop stress due to pressure. The creep rupture properties of the unique material are usually obtained from the base material creep rupture properties. The typical methodologies to estimate remaining life do not consider the actual applied stress due to malfunctioning supports, multiaxial stress effects, axial and through-wall creep redistribution, time-dependent material-specific weldment creep rupture properties, residual welding stresses, and actual operating temperatures and pressures. It has been determined that the initiation and propagation of Grade 91 creep damage is a function of stress to about the power of 9 at higher applied stresses. There have been many examples of malfunctioning piping supports creating unintended high stresses. When the axial stress is nearly as high as the hoop stress, the applicable corresponding uniaxial stress for creep rupture life is increased about 30%. Multiaxial stress effects in circumferential weldments (e.g., when the axial stress is nearly as high as the hoop stress) can reduce the weldment creep life to less than 1/6th of the predicted life assuming a uniaxial stress or hoop stress due to pressure only. Since 2012, the ASME B31.1 Code has required that significant piping displacement variations from the expected design displacements shall be considered to assess the piping system’s integrity [1]. This paper discusses a strategy for an enhanced creep life evaluation of power piping circumferential weldments. Piping stresses can vary by a factor greater than 2.0. Consequently, the range of circumferential weldment creep rupture lives for a single piping system may vary by a factor as high as 40. Although there is uncertainty in the operating times at temperatures and pressures, all of the weldments within the piping system have the same time, temperatures, and pressures, so the corresponding uncertainties for these three attributes are normalized within the same piping system. Since the applied stresses are the most important weld-to-weld variable within a piping system, it is necessary to have an accurate evaluation of the applied stresses to properly rank the creep rupture lives of the circumferential weldments. This methodology has been successfully used to select the lead-the-fleet creep damage in circumferential weldments over the past 15 years.

scholarly journals Finite Element Analysis of RC Beams by the Discrete Model and CBIS Model Using LS-DYNA

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Seung H. Yang ◽  
Kwang S. Woo ◽  
Jeong J. Kim ◽  
Jae S. Ahn
Keyword(s):  
Finite Element ◽  
Discrete Model ◽  
Kinematic Hardening ◽  
Material Model ◽  
General Purpose ◽  
Solid Model ◽  
Element Analysis ◽  
Explicit Finite Element ◽  
Finite Element Software ◽  
Concrete Elements

There are several techniques to simulate rebar reinforced concrete, such as smeared model, discrete model, embedded model, CLIS (constrained Lagrange in solid) model, and CBIS (constrained beam in solid) model. In this study, however, the interaction between the concrete elements and the reinforcement beam elements is only simulated by the discrete model and CBIS (constrained beam in solid) model. The efficiency and accuracy comparisons are investigated with reference to the analysis results by both models provided by LS-DYNA explicit finite element software. The geometric models are created using LS-PrePost, general purpose preprocessing software for meshing. The meshed models are imported to LS-DYNA where the input files are then analyzed. Winfrith and CSCM concrete material options are employed to describe the concrete damage behavior. The reinforcement material model is capable of isotropic and kinematic hardening plasticity. The load versus midspan deflection curves of the finite element models correlate with those of the experiment. Under the conditions of the same level of accuracy, the CBIS model is evaluated to have the following advantages over the discrete model. First, it has the advantage of reducing the time required for FE modeling; second, saving computer CPU time due to a reduction in total number of nodes; and third, securing a good aspect ratio of concrete elements.

Prediction of Creep Life on Notched Bar Specimens of Grade 92 Steel

2016 ◽  
Author(s):  
Haruhisa Shigeyama ◽  
Yukio Takahashi ◽  
Jonathan Parker
Keyword(s):  
Finite Element ◽  
Creep Damage ◽  
Creep Data ◽  
Creep Failure ◽  
Creep Tests ◽  
Energy Fraction ◽  
Damage Models ◽  
Finite Element Software ◽  
Notched Specimens ◽  
Life Fraction

Creep tests on two kinds of circumferentially notched round bar specimens as well as plain bar specimen were performed to obtain the multiaxial and uniaxial creep data. Creep damage models of strain fraction and energy fraction rule were developed using these creep data. Then creep damage analyses using a finite element software, MSC Marc, were carried out on notched specimens of both types and creep failure lives were predicted using the creep damage models of classical life fraction rule and developed strain or energy fraction rule. Experimental failure lives of all the conditions of notched specimens were compared with analytical results. As a result, creep failure lives obtained by life fraction rule were underestimated in the short term region and overestimated in the long term region. On the other hands, it is apparent that the majority of creep failure lives obtained by strain and energy fraction rule were predicted with an accuracy within a factor of two. Furthermore, some interrupted creep tests and creep void observations were conducted on the notched specimens of both types. The distributions of creep void number density were in good agreement with the distributions of creep damage calculated by finite element analyses.

Prediction of Welding Residual Stresses, Crack Initiation and Creep Crack Driving Forces C(t) Within a Continuous Finite Element Solution

2010 ◽  
Author(s):  
D. P. Bray ◽  
R. J. Dennis ◽  
M. C. Smith
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Driving Forces ◽  
Welding Process ◽  
Creep Damage ◽  
Operating Conditions ◽  
Finite Element Solution ◽  
Element Solution ◽  
Element Analysis ◽  
Creep Crack

The work reported in this paper investigates the manufacture, through-life operation and cracked behaviour of an attachment weld in a UK AGR boiler. A structural assessment of the attachment weld was performed to demonstrate its integrity. This assessment made use of complex finite element analysis of both the welding process and postulated defects. A simulation of the welding process was performed in order to predict the residual stresses and hardened material state throughout the attachment weld. The welding simulation was performed in two stages since a butter weld was deposited prior to the attachment weld itself. The accumulation of creep damage was predicted during steady normal operating conditions for the lifetime of the component. A contour map of creep damage was used to postulate the location and size of hypothetical single and double edge surface cracks within the weld. These postulated cracks were then explicitly introduced into the finite element model. The crack tip stress parameter C(t) was evaluated in order to predict the creep crack driving forces. The results from a cracked body simulation suggested that the creep crack driving force C(t) reduces as the crack grows, due to relief of the dominant welding residual stresses. The residual stress, creep damage and cracked body simulations have been brought together into a novel continuous finite element solution. The results can be used to support a safety case for continued operation of existing plant.

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