A Probabilistic Gas Touched Length Analysis

2011 ◽  
Author(s):  
Carl D. Skelonis ◽  
M. Brett Shelton ◽  
Glenn T. Burney
Keyword(s):  
High Temperature ◽  
Creep Damage ◽  
Oxide Thickness ◽  
Thickness Measurement ◽  
Operating Conditions ◽  
Life Assessment ◽  
Remaining Life ◽  
Analysis Model ◽  
Specific Test ◽  
Length Analysis

Field measurements of the steamside oxide thickness for high temperature (> 850F) boiler tubing subject to the accumulation of creep damage often are made to support deterministic assessments of the remaining life. Most often, these inspections are undertaken to understand the condition of the tubing at some particular location along a circuit, often as a result of a tube failure. The life assessment is based on relationships that have been developed between oxide growth kinetics and temperature. Unfortunately, because of variability in the oxide-temperature relationships reflecting different original data sets, and because of the inherent uncertainty in materials properties where heat-specific test data is not available, there typically exists a broad range of uncertainty in the deterministic assessment results. Large utility-type boilers typically contain a number of high temperature sections, including various stages of superheat and reheat, each of which will contain miles of tubing. Since the temperature derived from an oxide thickness measurement is relevant only to the specific location where the measurement was made, the deterministically derived life calculation is also specific to that location. As a result, the attempt to draw conclusions regarding the condition of an entire superheater or reheater section from measurements made at only one or two locations in those sections is fraught with difficulties. It is for this reason that the Probabilistic Gas Touched Length Analysis model has been developed. This model makes it possible to calculate creep damage accumulation/remaining life at any point along the steam path. Oxide thickness data and operating data are the primary operating inputs into the model, which performs heat transfer calculations at user-defined locations along the length of the tube circuit. The model applies statistical methods to evaluate variations in operating conditions as well as in physical and mechanical properties using a Monte Carlo simulation to generate values for the probability of failure at selected locations. This paper will discuss the limitations of the existing approach to estimating the remaining life of high temperature boiler tubing and present the underpinning theory of the gas touched length analysis model. A case study showing the analysis results is included.

A Damage Evaluation Model of Turbine Blade for Gas Turbine

2016 ◽  
Author(s):  
Dengji Zhou ◽  
Meishan Chen ◽  
Huisheng Zhang ◽  
Shilie Weng
Keyword(s):  
High Temperature ◽  
Real Time ◽  
Gas Turbine ◽  
Evaluation Model ◽  
Creep Damage ◽  
Operating Conditions ◽  
Damage Analysis ◽  
Damage Evaluation ◽  
Analysis Model ◽  
Estimation Model

Current maintenance, having a great impact on the safety, reliability and economics of gas turbine, becomes the major obstacle of the application of gas turbine in energy field. An effective solution is to process Condition based Maintenance (CBM) thoroughly for gas turbine. Maintenance of high temperature blade, accounting for most of the maintenance cost and time, is the crucial section of gas turbine maintenance. The suggested life of high temperature blade by Original Equipment Manufacturer (OEM) is based on several certain operating conditions, which is used for Time based Maintenance (TBM). Thus, for the requirement of gas turbine CBM, a damage evaluation model is demanded to estimate the life consumption in real time. A physics-based model is built, consisting of thermodynamic performance simulation model, mechanical stress estimation model, thermal estimation model, creep damage analysis model and fatigue damage analysis model. Unmeasured parameters are simulated by the thermodynamic performance simulation model, as the input of the mechanical stress estimation model and the thermal estimation model. Then the stress and temperature distribution of blades will be got as the input of the creep damage analysis model and the fatigue damage analysis model. The real-time damage of blades will be evaluated based on the creep and fatigue analysis results. To validate this physics-based model, it is used to calculate the lifes of high temperature blade under several certain operating conditions. And the results are compared to the suggestion value of OEM. An application case is designed to evaluate the application effect of this model. The result shows that the relative error of this model is less than 10.4% in selected cases. And it can cut overhaul costs and increase the availability of gas turbine significantly. Therefore, the physical-based damage evaluation model proposed in this paper, is found to be a useful tool to tracing the real-time life consumption of high temperature blade, to support the implementation of CBM for gas turbine, and to guarantee the reliability of gas turbine with lowest maintenance costs.

Remaining Creep Life Assessment of Service Superheat Tube Boiler

2015 ◽  
Vol 659 ◽  
pp. 686-690 ◽  
Author(s):  
Pornsak Thasanaraphan ◽  
Pannawat Thapnuy ◽  
Duangporn Ounpanich ◽  
Pratip Vongbandit
Keyword(s):  
Accumulation Rate ◽  
Creep Damage ◽  
Damage Mechanism ◽  
Thickness Measurement ◽  
Life Assessment ◽  
Remaining Life ◽  
Design Data ◽  
Remaining Life Assessment ◽  
Maintenance And Inspection ◽  
Creep Life Assessment

The demand of remaining life assessment of the boilers arises from technical, economic, and legal reasons. Creep is major damage mechanism of primary superheat tube boiler during prolong operation at high temperature and pressure in a water tube boiler. This paper presents the calculation method for the remaining life assessment due to creep damage. The service-exposed primary superheat tube made of 2.25Cr-1Mo steels. During scheduled inspection, wall thickness measurement, metallographic investigation by replica technique, design data and operating condition were used to estimate the remaining life in the form of creep damage accumulation rate calculated from life fraction using Larson-Miller Parameter. The results indicate that the primary superheat tubes satisfy in extension service life. By attaining an accurate and timely discussion of the results, the engineer can manage the maintenance and inspection schedule for the critical part in the boiler.

Fitness for Service and Remaining Life Assessment for 1-1/4Cr-1/2Mo Reactor System Piping on a Catalytic Reformer Unit

2006 ◽  
Author(s):  
Ayman M. Cheta ◽  
Ray Konet ◽  
F. Skip Hoyt
Keyword(s):  
Creep Damage ◽  
Pressure Vessels ◽  
Operating Conditions ◽  
Life Assessment ◽  
Low Alloy Steels ◽  
General Corrosion ◽  
Remaining Life ◽  
Reheat Cracking ◽  
Remaining Life Assessment ◽  
Welded Pipe

Fitness for service and remaining life assessment were performed on high temperature reactor piping to verify mechanical integrity for a desired remaining life. The NPS 20 1-1/4Cr-1/2Mo piping, which is the subject of this paper, was built in 1968 to the 1966 edition of ASA B31.3 for design conditions 465 psi at 950 °F / 365 psi at 1000 °F (3.16 MPa at 510 °C / 2.48 MPa at 538 °C) for hydrogen and naphtha service. The actual operating conditions are 400 psi at 900 °F / 330 psi at 950 °F (2.72 MPa at 482 °C / 2.24 MPa at 510 °C). Due to numerous reported failures in the industry in the 1980’s, the ASME codes for piping and pressure vessels lowered the allowable stresses for low alloy steels operating in the creep range, mainly above 900 °F (482 °C). Piping systems designed prior to changing the allowable stress do not satisfy today’s codes. The operating stresses which can lead to failure from potential damage mechanisms, e.g. creep, reheat cracking and general corrosion, are defined and their impact on fitness-for-service and remaining life evaluated. Acceptance criteria for different types of defects were established prior to the unit maintenance turnaround by: 1. Finite element modeling of assumed different degrees of weld peaking and pipe out-of-roundness for longitudinally welded pipe. 2. Piping flexibility / stress analysis to identify areas with the highest operating stresses. 3. Stresses from 1 and 2 above were used to calculate the creep life based on Larson-Miller parameter (API 530). Acceptable flaw sizes were limited by the desired remaining life. Inspection plans were developed to inspect for reheat cracking, creep damage, peaking, out of roundness, as well as general corrosion.

Elevated-Temperature Life Assessment

2021 ◽  
pp. 146-166
Author(s):  
Arun Sreeranganathan ◽  
Douglas L. Marriott
Keyword(s):  
High Temperature ◽  
Elevated Temperature ◽  
Stress Relaxation ◽  
Damage Mechanics ◽  
Elevated Temperatures ◽  
Constitutive Models ◽  
Life Assessment ◽  
Remaining Life ◽  
High Temperature Components ◽  
Remaining Life Assessment

Abstract This article provides some new developments in elevated-temperature and life assessments. It is aimed at providing an overview of the damage mechanisms of concern, with a focus on creep, and the methodologies for design and in-service assessment of components operating at elevated temperatures. The article describes the stages of the creep curve, discusses processes involved in the extrapolation of creep data, and summarizes notable creep constitutive models and continuum damage mechanics models. It demonstrates the effects of stress relaxation and redistribution on the remaining life and discusses the Monkman-Grant relationship and multiaxiality. The article further provides information on high-temperature metallurgical changes and high-temperature hydrogen attack and the steps involved in the remaining-life prediction of high-temperature components. It presents case studies on heater tube creep testing and remaining-life assessment, and pressure vessel time-dependent stress analysis showing the effect of stress relaxation at hot spots.

Latest Developments in Optimizing Reformer Tube Life Through Advanced Inspection and Remaining Life Assessment

2013 ◽  
Author(s):  
Brian Shannon ◽  
Carl E. Jaske
Keyword(s):  
Operating Conditions ◽  
Life Assessment ◽  
Inspection System ◽  
Remaining Life ◽  
Centrifugally Cast ◽  
Steam Methane ◽  
Recent Developments ◽  
Reformer Tubes ◽  
Remaining Life Assessment ◽  
Tube Life

Steam methane reformer tubes must withstand high temperature and pressures during operation and are made from centrifugally cast austenitic materials, typically HK-40, HP Modified, and Micro-Alloy materials. Since operating conditions can result in various forms of damage, the identification and quantification of damage is of vital importance if tube life is to be predicted accurately. This paper describes the recent developments in an integrated inspection system which uses multiple NDT techniques to provide a most comprehensive assessment of current tube condition. This system is coupled with a sophisticated remaining life assessment software model which predicts the remaining life of each tube in a furnace.

Remaining Life Assessment of an External Pressure Vessel in Creep Range and Inspection Findings

2017 ◽  
Author(s):  
Yoichi Ishizaki ◽  
Futoshi Yonekawa ◽  
Takeaki Yumoto ◽  
Teppei Suzuki ◽  
Shuji Hijikawa
Keyword(s):  
Pressure Vessel ◽  
Creep Damage ◽  
External Pressure ◽  
Pressure Vessels ◽  
Life Assessment ◽  
Remaining Life ◽  
Assessment Technique ◽  
Creep Cavity ◽  
Creep Analysis ◽  
Remaining Life Assessment

As widely recognized in the industry, it is important to evaluate the creep damage of an elevated temperature vessel so that the mechanical integrity of the vessel can be achieved through the adequate repair and replacement planning. This is quite straight forward procedure for internal pressure vessels. For an external pressure vessel, it is not easy to assess the creep damage due to the complexity of the creep buckling analysis. Eventually, creep cavity evaluation technique without identifying the correct stress distribution has been used so often. However, due to the uncertainty of the technique itself plus conservative mindset of the inspectors, it tends to leads to an excessive maintenance most of the cases. In order to conduct a reasonable remaining life assessment, it is desirable to use the creep cavity inspection in conjunction with another assessment technique such as FEM creep analysis as stated in API 579-1/ASME FFS-1 10.5.7. In this paper, comprehensive approach with FEM and field inspection such as creep cavity evaluation to reinforce the uncertainty of each method will be demonstrated.

Power Turbine Remaining Life Assessment

2001 ◽  
Author(s):  
Bruce deBeer ◽  
Paul Chilcott ◽  
Dave Seib
Keyword(s):  
Analytical Techniques ◽  
Spare Parts ◽  
Operating Conditions ◽  
Life Assessment ◽  
Remaining Life ◽  
Operating Cycle ◽  
Statistical Probability ◽  
Power Turbine ◽  
Remaining Life Assessment ◽  
As Stress

The design life of an industrial power turbine has traditionally been 100,000 hours or 5,000 starts, based on a specific set of assumed operating conditions. Actual operating conditions vary from site to site, and are often less severe than the initial assumptions used by the manufacturer. This is why Dresser-Rand has developed a Remaining Life Assessment program. The objective of this program is to assist operators in extending the life of expensive components, determining inspection intervals, developing component replacement schedules, and establishing a spare parts stocking program. A comprehensive remaining life assessment must take into account unit operating history, a thorough non destructive examination of the components being considered for reuse, thermal and structural analyses using current analytical techniques, and material evaluations. There is some amount of variability in the input and output for each of these steps. Defects smaller than a given size are not always detected, material test results have a statistical distribution, and each operating cycle is unique. Traditionally the expected life has been based on a predetermined set of assumptions, such as stress analyses using typical dimensions, minus three sigma fatigue and creep properties, etc. The Dresser-Rand approach accounts for these inherent variations and establishes the statistical probability of successfully extending power turbine life without failure or unplanned maintenance as a function of time.

scholarly journals 120 PENERAPAN STANDAR UJI TANPA MERUSAK UNTUK MENENTUKAN SISA UMUR PIPA KETEL UAP PADA UNIT PEMBANGKIT LISTRIK TENAGA UAP

2008 ◽  
Vol 8 (3) ◽  
pp. 120
Author(s):  
Supriadi Supriadi
Keyword(s):  
Hardness Test ◽  
Thickness Measurement ◽  
Test Methods ◽  
Life Assessment ◽  
Remaining Life ◽  
Boiler Tube ◽  
Destructive Test ◽  
Electrical Generator ◽  
Remaining Life Assessment ◽  
Non Destructive

<p>Application of standard for remaining life assessment at boiler tube of steam powered electrical generator unit by<br />non-destructive test (NDT), up to now has been very important. The condition of boiler tube used in electrical<br />generator in Indonesia has reached its design limit and even some of them have replaced. This research used nondestructive<br />test methods by SNI, JIS and API standard and was conducted at boiler unit II in Indonesia, that has<br />already in 25 years operated. This method consists of several technique approaches that are: replica methods<br />(microstructure), hardness test, outside diameter measurement (OD), and wall thickness measurement. After<br />assessment and analysis, the results of non destructive test methods showed that the remaining life of boiler tube<br />is 100.000 to 120.000 operation hours.</p>

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