Design and Life Prediction of Fired Heater Tubes in the Creep Range

1988 ◽  
Vol 110 (3) ◽  
pp. 322-328 ◽  
Author(s):  
R. Seshadri
Keyword(s):  
Life Prediction ◽  
Operating Experience ◽  
Creep Damage ◽  
Economical Design ◽  
Inspection Strategy ◽  
The Mean ◽  
Life Predictions ◽  
Tube Life ◽  
Creep Deformations ◽  
Heater Tube

Realistic fired heater tube-life predictions are essential to safe and economical design, proactive inspection strategy and meaningful tube retirement evaluations. The traditional method of heater tube design (API RP 530), that is based on the “mean-diameter equation,” sometimes implies tube-life in excess of actual operating experience. The main reason for this discrepancy is the interaction of cyclic radial thermal gradient, that exists across the tube wall, with the pressure-induced stresses resulting in enhanced creep damage. Upper-bound estimates for creep deformations and creep damage are obtained in this paper using a simple analytical procedure. Some broad guidelines relating to the assessment of remaining tube-life, tube retirement and inspection frequencies are presented.

Investigation of Cyclic Creep Behavior and Life Prediction Method of Notch Specimen During High Temperature Fatigue

2008 ◽  
Author(s):  
Zhichao Fan ◽  
Xuedong Chen ◽  
Heng Jiang ◽  
Jie Dong
Keyword(s):  
High Temperature ◽  
Fatigue Life ◽  
Creep Behavior ◽  
Life Prediction ◽  
Low Cycle Fatigue ◽  
Prediction Method ◽  
Creep Damage ◽  
Cyclic Creep ◽  
High Temperature Stress ◽  
The Mean

Cyclic creeps can bring to additional damage, resulting in shorter fatigue lives, so the effects of fatigue damage and cyclic creep damage should be taken into account in the life prediction. In this case, the mean strain rate model based on ductility exhaustion theory can be adopted. An engineering structure inevitably has some stress concentration area. As to this situation, by high temperature low cycle fatigue tests with different notch sizes, cyclic creep behavior is investigated and compared with that of smooth specimens in this paper. The results indicate that, due to existence of notch, the cyclic creep deformation is restricted within a little range around notch and cannot spread widely, so the fatigue strength of notch specimens increases. Based on the ductility dissipation theory and effective stress concept of continuum damage mechanism (CDM), the mean displacement rate at half life is acted as control parameter, and a high temperature multi-axial fatigue life prediction method is proposed in this paper. The prediction results show that all test data are within ±2.0 error factor, which is better than that of axial maximum stress method. This method has simple form and fewer constants, can be used to predict high temperature stress-controlled fatigue life whatever smooth or notch specimens.

Use of life and strain fraction rules for creep life prediction of pressurized pipe components undergoing geometry change

2005 ◽  
Vol 40 (4) ◽  
pp. 385-394 ◽  
Author(s):  
T H Hyde ◽  
W Sun ◽  
A. A Becker
Keyword(s):  
Life Prediction ◽  
Small Deformation ◽  
Creep Damage ◽  
Deformation Analysis ◽  
Stress And Strain ◽  
Creep Failure ◽  
Creep Life Prediction ◽  
Failure Life ◽  
Life Predictions ◽  
Life Fraction

The results of creep failure life predictions of pressurized plain pipes, pipe bends, and a thick-walled pipe with a circumferential weld are used to demonstrate the applicability of a stress-based life fraction rule (LFR) and a strain-based strain fraction rule (SFR), under conditions of geometric non-linearity (GNL). The material properties used are related to a CrMoV pipe, at 640°C. Both the LFR and the SFR predictions are based on the stress and strain solutions obtained from the finite element calculations using a Norton creep law. The results obtained were compared with those obtained from corresponding creep damage analyses. For the cases investigated, it has been shown that, compared with damage results, conservative failure lives with consistent failure positions were obtained for the pipe weld, using both the LFR and the SFR methods. For plain pipes and pipe bends, the SFR prediction produces conservative results. However, the LFR prediction overestimates the failure life for the range of pipe diameter ratios investigated. The results obtained indicate that the LFR and SFR methods have potential for predicting creep failure lives in cases when the effect of geometry change is significant and hence the method based on the steady state peak stresses obtained from small deformation analysis is not applicable.

Assessing Creep Damage in Cast Materials for High Temperature Reformer Tube Applications

2007 ◽  
Author(s):  
Brian Shannon
Keyword(s):  
Life Prediction ◽  
Creep Damage ◽  
Nondestructive Inspection ◽  
Life Assessment ◽  
Centrifugally Cast ◽  
Steam Reformer ◽  
Dimensional Measurements ◽  
Exact Degree ◽  
Tube Life ◽  
Reformer Tube

Centrifugally cast materials, namely HK-40, HP Modified and Micro-Alloy materials are used in Steam Reformer tube applications. These materials, operating in the creep range, are subject to time/temperature related degradation which can manifest in several ways. The quantification of damage is of vital importance if tube life is to be predicted accurately. A comprehensive nondestructive inspection approach has been developed to assess the exact degree of damage. The approach utilizes several NDE techniques including ultrasonic, eddy current and dimensional measurements. The combination of the techniques provides valuable data for establishing condition assessment and remaining tube life prediction. Experiences and findings are discussed in the paper. Discussion of destructive methodologies for tube life assessment are beyond the scope of this paper.

Life Prediction of Power Turbine Components for High Exhaust Back Pressure Applications: Part I — Disks

2015 ◽  
Author(s):  
Dipankar Dua ◽  
Brahmaji Vasantharao
Keyword(s):  
Steady State ◽  
Secondary Flow ◽  
Gas Turbines ◽  
Life Prediction ◽  
Creep Damage ◽  
Back Pressure ◽  
System Level ◽  
Cyclic Life ◽  
Power Turbine ◽  
The Impact

Industrial and aeroderivative gas turbines when used in CHP and CCPP applications typically experience an increased exhaust back pressure due to pressure losses from the downstream balance-of-plant systems. This increased back pressure on the power turbine results not only in decreased thermodynamic performance but also changes power turbine secondary flow characteristics thus impacting lives of rotating and stationary components of the power turbine. This Paper discusses the Impact to Fatigue and Creep life of free power turbine disks subjected to high back pressure applications using Siemens Energy approach. Steady State and Transient stress fields have been calculated using finite element method. New Lifing Correlation [1] Criteria has been used to estimate Predicted Safe Cyclic Life (PSCL) of the disks. Walker Strain Initiation model [1] is utilized to predict cycles to crack initiation and a fracture mechanics based approach is used to estimate propagation life. Hyperbolic Tangent Model [2] has been used to estimate creep damage of the disks. Steady state and transient temperature fields in the disks are highly dependent on the secondary air flows and cavity dynamics thus directly impacting the Predicted Safe Cyclic Life and Overall Creep Damage. A System-level power turbine secondary flow analyses was carried out with and without high back pressure. In addition, numerical simulations were performed to understand the cavity flow dynamics. These results have been used to perform a sensitivity study on disk temperature distribution and understand the impact of various back pressure levels on turbine disk lives. The Steady Sate and Transient Thermal predictions were validated using full-scale engine test and have been found to correlate well with the test results. The Life Prediction Study shows that the impact on PSCL and Overall Creep damage for high back pressure applications meets the product design standards.

The Effects of Cooling Holes on the Creep Life in a Modeling Specimen of Single Crystal Air-Cooled Turbine Blade

2011 ◽  
Vol 284-286 ◽  
pp. 1678-1683 ◽  
Author(s):  
Da Shun Liu ◽  
Bai Zhi Wang ◽  
Zhi Xun Wen ◽  
Zhu Feng Yue
Keyword(s):  
Single Crystal ◽  
Turbine Blade ◽  
Damage Model ◽  
Creep Damage ◽  
Creep Life ◽  
Damage Development ◽  
User Subroutine ◽  
Initial Rupture ◽  
Creep Deformations ◽  
Sem Analyses

This paper presents the study of the influences of cooling holes on the creep life behavior in the modeling specimen of single crystal cooling turbine blade at high temperature. Thin-walled cylindrical specimens with holes are tested to model the air-cooled turbine blade. Specimens without holes are also studied to make comparisons. Experimental results show that at 900°C, the creep lives of specimens with holes are longer than those of specimens without holes. Scanning Electron Microscopy (SEM) analyses reveal that creep deformations occur firstly around the cooling holes and finally rupture at the region with low stress and strain. Finite element analyses are used to study the creep damage development by a K-R damage model which has been implemented into the Abaqus user subroutine (UMAT). Simulation results show that stress concentration and redistribution occur around the cooling holes during the creep development. It is also shown that the maximum strain and stress are around the cooling holes which are the initial rupture region in the experiments.

scholarly journals Predicting residual service life of concrete infrastructure: a considerably controversial subject

2019 ◽  
Vol 289 ◽  
pp. 08002
Author(s):  
Joost Gulikers
Keyword(s):  
Service Life ◽  
Life Prediction ◽  
Wide Spectrum ◽  
Probabilistic Approach ◽  
Service Life Prediction ◽  
Model Parameters ◽  
Residual Service Life ◽  
Site Investigations ◽  
Increasing Demand ◽  
Life Predictions

There is an increasing demand from asset owners for service life prediction of existing reinforced concrete structures. This requires assessment of the current condition and modelling to allow for a prediction. This paper critically discusses a number of subjects relevant for service life prediction with respect to durability related to chloride-induced reinforcement corrosion. The subjects include the physical meaning and variability of the end-of-service-life criterion, the validity of the deterioration models, the availability, variability and reality level of input values for some model parameters, as well as some practical issues concerning site investigations. The findings are exemplified by calculation examples using both a deterministic as well as a full probabilistic approach. It is anticipated that in the future a full probabilistic approach will be adopted which makes service life predictions more prone to manipulation of input values, as literature provides a wide spectrum of values to choose from. Although a probabilistic approach seems very impressive to most asset owners it usually disguises the lack of knowledge, responsibility and liability of the consultant involved. It is concluded that asset owners will be easy prey for consultants to play a lucrative numbers game eventually providing a desirable and realistic outcome, mostly already known beforehand.

Ultrasonic Nondestructive Evaluation of the Creep Damaged IN738LC Superalloy

2004 ◽  
Vol 449-452 ◽  
pp. 569-572 ◽  
Author(s):  
Jai Won Byeon ◽  
J.H. Song ◽  
S.I. Kwun
Keyword(s):  
Nondestructive Evaluation ◽  
Ultrasonic Wave ◽  
Linear Correlation ◽  
Ultrasonic Attenuation ◽  
Creep Damage ◽  
Ultrasonic Nondestructive Evaluation ◽  
Microstructural Parameters ◽  
Creep Time ◽  
The Mean ◽  
The Relationship

It was attempted to evaluate nondestructively the creep damaged IN738LC Ni based superalloys with different degree of rafting using ultrasonic wave. Microstructural parameters (length and width of γ' precipitates) and ultrasonic attenuation were measured in order to clarify the relationship between them. Both the mean length of γ' precipitates and the ultrasonic attenuation increased with creep time. Ultrasonic attenuation was found to have a linear correlation with the mean length of γ' precipitates. It is suggested that the ultrasonic attenuation can be used as a potential nondestructive parameter for assessing the degree of creep damage of IN738LC superalloy.

Life Prediction of SnPb and SnAg Solder Joints in PBGA Packages Using a Severity Metric

2003 ◽  
Author(s):  
Donghyun Kim ◽  
Andrew Mawer ◽  
Tess J. Moon ◽  
Glenn Y. Masada
Keyword(s):  
Life Prediction ◽  
Solder Joints ◽  
Mean Value ◽  
Printed Wiring Board ◽  
Geometric Configurations ◽  
Design And Manufacturing ◽  
Creep Time ◽  
Snag Solder ◽  
Wiring Board ◽  
Life Predictions

A severity metric is developed to predict the life of SnPb and SnAg solder joints in PBGA packages by quantitatively estimating the changes in damage arising from different board configurations and accelerated thermal cycle tests (ATC). Damage measures include time-dependent creep, time-independent plastic deformation, and an effective stress that is computed from the ATC parameters of temperatures, dwell-time, and ramp rates and from package geometries on the printed wiring board. Life prediction using this severity metric has been applied to 24 sets of test data on SnPb and SnAg solder joints in 357-PBGA packages and include three post-processing conditions (aged at 150/160°C, quenched at 0°C, and air-cooled), three ATC test conditions (0–100°C, −40–125°C, and −55–125°C), and four package-on-board geometric configurations. Statistical analysis is provided to compare the life predictions based upon the severity metric and from ATC testing—predicted joint life is well within one standard deviation of the experimental mean value of life for most of the 24 cases. The severity metric can be used to quantify the effects of design and manufacturing choices on joint life.

Damage Evolution and Life Prediction of a P91 Longitudinal Welded Tube Under Internal Pressure Creep

2008 ◽  
Author(s):  
Takashi Ogata ◽  
Takayuki Sakai ◽  
Masatsugu Yaguchi
Keyword(s):  
Internal Pressure ◽  
Heat Affected Zone ◽  
Void Growth ◽  
Damage Evolution ◽  
Life Prediction ◽  
Prediction Method ◽  
Creep Damage ◽  
Creep Tests ◽  
Creep Analysis ◽  
Welded Tube

Clarification of creep damage mechanism and establishment of remaining life prediction methods of longitudinal welded piping of P91 steel are important subjects to maintain reliable operation of boilers in thermal power plants. Internal pressure creep tests were conducted on P91 steel longitudinal welded tubes to characterize the evolution of creep damage with time and to evaluate a life prediction method. Interrupted creep tests were utilized for damage observation in addition to rupture tests. Three dimensional FE creep analysis of the creep tested specimens were conducted to identify stress and creep strain distribution within the specimen during creep. Failure occurred at a heat affected zone without significant macroscopic deformation. It was found that initiation of creep voids had concentrated at mid-thickness region rather than surface. The creep analysis results indicated that triaxial tensile stress yielded at the mid-thickness region of the heat affected zone due to difference of creep deformation property between the base metal, heat affected zone and weld metal. It was suggested that the triaxial stress state caused acceleration of the creep damage evolution in the heat affected zone resulting in internal failure of the tube specimens. A rupture time prediction method of the welded tube is proposed based on the maximum principal stress and the triaxial stress factor. Void growth behavior in the heat affected zone was well predicted by the previously proposed void growth simulation method by introducing void initiation function to the method.

scholarly journals Service Life Prediction of Reinforced Concrete in a Sea-Crossing Railway Bridge in Jiaozhou Bay: A Case Study

2019 ◽  
Vol 9 (17) ◽  
pp. 3570 ◽  
Author(s):  
Zhe Li ◽  
Zuquan Jin ◽  
Tiejun Zhao ◽  
Penggang Wang ◽  
Lixiao Zhao ◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Service Life ◽  
Reliability Index ◽  
Life Prediction ◽  
Jiaozhou Bay ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Railway Bridge ◽  
Box Girder ◽  
The Mean

Reinforced bar corrosion induced by chloride ingression is one of the most significant threats to the durability of concrete structures in marine environments. The concrete cover thickness, compressive strength, chloride diffusion coefficient, and surface defects of reinforced concrete in the Jiaozhou Bay sea-crossing railway bridge were measured. The temperature and relative humidity in the concrete and the loading applied onto the reinforced concrete were monitored. Based on the DuraCrete model, a revised model for the service life prediction of concrete structures was established, considering the effects of temperature and loading on the chloride diffusion coefficient. Further, the reliability indexes of the reinforced concrete box girder, pier, and platform, located in the marine and land sections, in relation to service lives lasting various numbers of years, were calculated. The measured and calculated results show that the mean cover thicknesses of concrete piers in the marine and land sections are 52 mm and 36 mm, respectively, and the corresponding standard deviations are 5.21 mm and 3.18 mm, respectively. The mean compressive strengths of concrete in the marine and land sections are 56 MPa and 46 MPa, respectively. The corresponding standard deviations are 2.45 MPa and 2.67 MPa, respectively. The reliability indexes of the reinforced concrete box girder and platform in the marine section, under the condition of a service life of 100 years, are 1.81 and 1.76, respectively. When the corrosion-resistant reinforced bar was used in the pier structure in the marine section, its reliability index increased to 2.01. Furthermore, the reliability index of the reinforced concrete damaged by salt fog in the land section was 1.71.

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