scholarly journals Development of On-Line Monitoring Systems for High Temperature Components in Power Plants

Sensors ◽  
2013 ◽  
Vol 13 (11) ◽  
pp. 15504-15512 ◽  
Author(s):  
Hongcai Zhang ◽  
Jiuhong Jia ◽  
Ning Wang ◽  
Xiaoyin Hu ◽  
Shan-Tung Tu ◽  
...  
Keyword(s):  
High Temperature ◽  
Power Plants ◽  
Monitoring Systems ◽  
On Line ◽  
High Temperature Components

Application of Damage Mechanics and Polynomial Chaos Expansion for Lifetime Prediction of High-Temperature Components Under Creep-Fatigue Loading

2020 ◽  
Author(s):  
Felix Koelzow ◽  
Muhammad Mohsin Khan ◽  
Christian Kontermann ◽  
Matthias Oechsner
Keyword(s):  
High Temperature ◽  
Power Plants ◽  
Damage Mechanics ◽  
Fatigue Loading ◽  
Probabilistic Methods ◽  
Lifetime Prediction ◽  
Model Parameters ◽  
Creep Fatigue ◽  
High Temperature Components ◽  
Mechanics Concepts

Abstract Several (accumulative) lifetime models were developed to assess the lifetime consumption of high-temperature components of steam and gas turbine power plants during flexible operation modes. These accumulative methods have several drawbacks, e.g. that measured loading profiles cannot be used within accumulative lifetime methods without manual corrections, and cannot be combined directly to sophisticated probabilistic methods. Although these methods are widely accepted and used for years, the accumulative lifetime prediction procedures need improvement regarding the lifetime consumption of thermal power plants during flexible operation modes. Furthermore, previous investigations show that the main influencing factor from the materials perspective, the critical damage threshold, cannot be statistically estimated from typical creep-fatigue experiments due to massive experimental effort and a low amount of available data. This paper seeks to investigate simple damage mechanics concepts applied to high-temperature components under creep-fatigue loading to demonstrate that these methods can overcome some drawbacks and use improvement potentials of traditional accumulative lifetime methods. Furthermore, damage mechanics models do not provide any reliability information, and the assessment of the resultant lifetime prediction is nearly impossible. At this point, probabilistic methods are used to quantify the missing information concerning failure probabilities and sensitivities and thus, the combination of both provides rigorous information for engineering judgment. Nearly 50 low cycle fatigue experiments of a high chromium cast steel, including dwell times and service-type cycles, are used to investigate the model properties of a simple damage evolution equation using the strain equivalence hypothesis. Furthermore, different temperatures from 300 °C to 625 °C and different strain ranges from 0.35% to 2% were applied during the experiments. The determination of the specimen stiffness allows a quantification of the damage evolution during the experiment. The model parameters are determined by Nelder-Mead optimization procedure, and the dependencies of the model parameters concerning to different temperatures and strain ranges are investigated. In this paper, polynomial chaos expansion (PCE) is used for uncertainty propagation of the model uncertainties while using non-intrusive methods (regression techniques). In a further post-processing step, the computed PCE coefficients of the damage variable are used to determine the probability of failure as a function of cycles and evolution of the probability density function (pdf). Except for the selected damage mechanics model which is considered simple, the advantages of using damage mechanics concepts combined with sophisticated probabilistic methods are presented in this paper.

Failure Mechanisms of High Temperature Components in Power Plants

2000 ◽  
Vol 122 (3) ◽  
pp. 246-255 ◽  
Author(s):  
R. Viswanathan ◽  
J. Stringer
Keyword(s):  
High Temperature ◽  
Power Plants ◽  
Failure Mechanisms ◽  
Laboratory Data ◽  
Broad Perspective ◽  
Section Size ◽  
Creep Fatigue ◽  
Ultimate Failure ◽  
High Temperature Components ◽  
Utility Deregulation

The principal mechanisms of failure of high temperature components include creep, fatigue, creep-fatigue, and thermal fatigue. In heavy section components, although cracks may initiate and grow by these mechanisms, ultimate failure may occur at low temperatures during startup-shutdown transients. Hence, fracture toughness is also a key consideration. Considerable advances have been made both with respect to crack initiation and crack growth by the above mechanisms. Applying laboratory data to predict component life has often been thwarted by inability to simulate actual stresses, strain cycles, section size effects, environmental effects, and long term degradation effects. This paper will provide a broad perspective on the failure mechanisms and life prediction methods and their significance in the context utility deregulation. [S0094-4289(00)00103-1]

Development of Guideline for Prediction of Inelastic Strain for Creep-Fatigue Evaluation

2013 ◽  
Author(s):  
Osamu Watanabe ◽  
Ken-ichi Kobayashi ◽  
Kyotada Nakamura
Keyword(s):  
High Temperature ◽  
Power Plants ◽  
Inelastic Strain ◽  
Local Area ◽  
Stage Of Development ◽  
Inelastic Analysis ◽  
Design Changes ◽  
Creep Fatigue ◽  
High Temperature Components ◽  
Fatigue Evaluation

Cyclic thermal and mechanical loads are frequently applied to power plants during their service lives due to the regular operation of start-up and shutdown. Design or actual lives of these high temperature machines and structures have been mainly dominated by the creep-fatigue failure life. Since most of these failures happen at limited local area, namely, it may happen at the geometrical or material discontinuities in structures or components, the detail inelastic analyses with a conservative margin are required at the design and maintenance. However, much time and colossal effort should be avoided at the stage of development to reduce the total cost of designing because the design changes many times until the final configuration is fixed. Many materials in the high temperature components are subjected to inelastic behaviors; plastic or creep strain always cause in the components. In the computational analyses such as Finite Element Analyses, constitutive equations of both plasticity and creep affect analytical results. Neuber’s rule is employed in the present design code to achieve the simplified design of component but its result sometimes provides more conservative margin. Stress Redistribution Locus (Hereinafter denoted as SRL) method is a simplified inelastic analysis and was developed in Japan. ETD committee in HPI has studied its applicability to basic problems and actual components.

Creep Assessment of Large Size High Temperature Components Using Small Creep Test Specimens

2016 ◽  
Author(s):  
Balhassn S. M. Ali
Keyword(s):  
High Temperature ◽  
Creep Test ◽  
Nuclear Power ◽  
Power Plants ◽  
Elevated Temperatures ◽  
Life Time ◽  
Safe Operation ◽  
Large Size ◽  
Testing Techniques ◽  
High Temperature Components

Most of the large components in the thermal, traditional and nuclear power plants such as pressurized vessels and pipes are operating at elevated temperatures. These temperatures and stress are high enough for creep to occur. For variety of reasons many of these power plants are now operating beyond their design life time. It is -known fact that as the high temperature components aged the failure rate normally increases as a result of their time dependent material damage. Further running of these components may become un-safe and dangerous in some cases. Therefore, creep assessment of the high temperature components of these plants is essential for their safe operation. Mainly for economic reasons these components have to be creep assessed as they are in service. However, assessing the creep strength for these high temperature components as they are in service, it can be challenging task, especially when these components are operating under extremely high temperature and/or stress. This paper introduces newly invented, small creep test specimens techniques. These new small types of specimens can be used to assess the remaining life times for the high temperature components, using only small material samples. These small material samples can be removed from the operating components surface, without affecting their safe operation. Two of the high temperature materials are used to validate the new testing techniques.

Remaining Lifetime Evaluation of High Temperature Components of Power Plant Steam Boilers: Case Studies

2009 ◽  
Author(s):  
Vaclav Mentl ◽  
Va´clav Lisˇka ◽  
Jaroslav Koc ◽  
Michal Chocholousˇek
Keyword(s):  
High Temperature ◽  
Power Plants ◽  
Fatigue Loading ◽  
Assessment Method ◽  
Operational Capability ◽  
Safety Coefficient ◽  
Working Temperature ◽  
Working Stress ◽  
Steam Boilers ◽  
High Temperature Components

The energy producing power plants are designed for operational period of 20, 30 years. During this period, inspections are realized to investigate the operational capability of the respective components and the plant as a whole, and when the designed time is approaching its limit, the crucial questions are raised with respect to the following possible operation, its safety and risks that stem from the fact that the continuous degradation of material properties occured during the longtime service as a result of service conditions, e.g. high temperatures, fatigue loading etc. The inspection of the boiler and the assessment of its future operational capability should ensure the safe operation and minimazing the failure risks. In comparison with the more sofisticated and much more expensive methods that use numbers of variables that enter the evaluation process of the lifetime exhaustion, or the metallographic non-destructive or even destructive methods that do not result often in a quantitative lifetime assessment, a relatively simple assessment method was used to evaluate the remaining lifetime of the high temperature components. On the basis of accelerated creep test data performed on the degraded materials, the remaining lifetime hours were calculated for the three “safety” situations: 1. “ZERO SAFETY” (neither recommended k = 1, 5 safety coefficient for working stress nor +70deg Celsius increase of working temperature were taken into consideration). 2. “STRESS SAFETY” (1, 5 safety coefficient for working stress and working temperature were taken into consideration). 3. “FULL SAFETY” (1, 5 safety coefficient for working stress and working temperature +70 deg Celsius were taken into consideration). This paper summarizes the results of remaining lifetime calculation for three different cases of steam boilers inspected after longtime service by Skoda Research ltd. Recently. On the basis of performed examination, the results provided the customer the recommendations relating the future safe and reliable operation.

Performance Monitoring Systems for Power Plants: General Features and Application Models

2002 ◽  
Author(s):  
M. Gambini ◽  
M. Vellini
Keyword(s):  
Monitoring System ◽  
Heat Recovery ◽  
Power Plants ◽  
Performance Monitoring ◽  
Measured Data ◽  
Diagnostic Information ◽  
Monitoring Systems ◽  
Heat Recovery Steam Generator ◽  
On Line ◽  
Plant Components

The general features and benefits of a performance monitoring system (PMS) and its capabilities on plant auditing and management are illustrated. The criteria for the validation and reconciliation of the measured data are tackled and the energetic diagnosis of components, by means the comparison between current performance and expected one, is shown. A “on line–real time” monitoring system evaluates the current performance of the power plant immediately and realistically, as well as it informs the operator of problems as soon as they occur and provides diagnostic information so that the operator can remedy the problem. After generals about PMS, two application models are shown: the first one deals with the reconciliation of measured data and it has been numerically developed with reference to a heat recovery steam generator; the second one deals with the energetic diagnosis of plant components and it has been developed with reference to a steam condenser.

Sign in / Sign up

Export Citation Format

Share Document