A techno-economic probabilistic approach to superheater lifetime determination

2006 ◽  
Vol 17 (1) ◽  
pp. 66-71
Author(s):  
M Jaeger ◽  
H Benhaim ◽  
D Tzidony ◽  
A Dumai ◽  
T Itai
Keyword(s):  
Life Cycle ◽  
Wall Thickness ◽  
Life Cycle Cost ◽  
Evaluation Model ◽  
Probabilistic Approach ◽  
Probability Of Failure ◽  
Operating Conditions ◽  
Time To Failure ◽  
Average Life ◽  
Failure Evaluation

In the commonly used approach, the lifetime of a superheater is estimated by characteristic values of the production parameters and the operating conditions. In this approach, a lower bound for a superheater lifetime is based on some arbitrary safety factor that does not necessarily reflect real life, where unexpected failures do occur. The method proposed here suggests coping with this reality, by employing a techno-economic probabilistic approach. It comprises the following two models: • A probabilistic time to failure evaluation model that considers the variability of the lifetime determining parameters. • A model to optimise values of technical parameters and operating conditions and to determine a superheater’s optimal replacement policy, based on life cycle cost considerations. The proposed probabilistic time to failure evaluation model can help to identify the most influential parameters for planning for a minimal probability of failure. It is applied to a unique problematic steel T22 superheater of rather specific parameters: corrosion rate, the Larson Miller Parameter (LMP), diameter and wall thickness. Sensitivity analysis has shown that the dominant factor affecting variation in superheater lifetime is the variation in the LMP, while the effect of the other parameters is quite marginal. Decreasing the standard deviation of the LMP (by keeping a more uniform material) lowered the probability of failure. This resulted in a practical recommendation to perform periodical checks of the parameter wall thickness. We also tested the effect of changing the nominal values of these parameters on the lifetime distribution. Hence, we suggest that the selection of the nominal values should be based on life cycle cost considerations; and propose a model to calculate, for any given combination, the average life cycle cost. The latter model, the optimal parameters combination model, optimises the combination of changes in all the superheater’s parameters by minimising the average life cycle cost associated with the superheater. Demonstrating the usefulness of the proposed approach, in a problematic case, suggests that it can be beneficially employed in the more general case whenever the planned lifetime of a design is threatened.

Non-intrusive corrosion-erosion monitoring for subsea applications

2011 ◽  
Vol 51 (1) ◽  
pp. 543
Author(s):  
Geir Instanes ◽  
Sindre Kristiansen ◽  
Olav Brakstad
Keyword(s):  
Wall Thickness ◽  
Life Cycle Cost ◽  
Assessment Tool ◽  
Pipe Wall ◽  
Guided Wave ◽  
Operating Conditions ◽  
Metallic Surface ◽  
High Coverage ◽  
Pipe Surface ◽  
Ultrasonic Guided Wave

Detection and monitoring of corrosion and erosion are essential prognostic means in preserving material integrity and reducing the life-cycle cost of industrial infrastructure, ships, aircrafts, ground vehicles, pipelines, oil installations, etc. Even topside, the operating conditions can be extremely difficult, facing problems like pipe surface roughness, fluid loading, temperature variations, and a host of other factors that make development of a robust wall thickness assessment tool a challenging task. Deploying a monitoring system subsea makes the application even more demanding when factors such as high pressure and limited access must be taken into account. The ClampOn Corrosion-Erosion Monitor has already been successfully installed at several locations topside and is now in its final stages of the subsea development. Non-invasiveness, high repeatability and high coverage are among its advantages, making it an excellent candidate for subsea use. The technology is based on the dispersion of ultrasonic guided wave modes. By using electromagnetism these waves can be transmitted through the pipe wall without the sensor being in direct contact with the metallic surface. It is installed on the outer pipe wall to produce real-time wall thickness information, not as a spot measurement, but as a unique average path wall thickness.

scholarly journals Effect of change in role of an aircraft on engine life

2013 ◽  
Vol 117 (1196) ◽  
pp. 1053-1070
Author(s):  
A. Gad-Briggs ◽  
A. Haslam ◽  
P. Laskaridis
Keyword(s):  
Life Cycle ◽  
Life Cycle Cost ◽  
Low Cycle Fatigue ◽  
Operating Conditions ◽  
Significant Life ◽  
European Theatre ◽  
Harsh Climate ◽  
Performance Conditions ◽  
Dust Ingestion

Abstract New aircraft require years of development from concept to realisation and can be prone to delays. Consequently, military operators take existing fleets and operate them in a different role. The objective of this study is to examine the effect of operating a typical low bypass military fast jet engine, originally designed for a European theatre, in a hot and harsh climate. The specific purpose is to determine the effect on the high-pressure turbine blade life and the life- cycle cost of the engine. A mission profile and respective performance conditions were analysed and modelled using an in-house performance tool. The flow conditions were simulated using ANSYS® FLUENT. A conjugated heat transfer solution was adopted to determine the blade metal temperature. The blade was modelled physically in 3D using SIMULIA® ABAQUS FEA software. The stresses were derived and used to calculate the temperature coupled low cycle fatigue and creep life. A deterioration case was also studied to evaluate the effect of sand and dust ingestion. There was a significant life reduction of approximately 50% due to creep. The reduction in life was inversely proportional to the life cycle cost of the engine depending on the operating conditions. The results were compared with similar engines and summarised in the context of airworthiness regulations and component integrity.

Coating Rejuvenation: New Repair Technology for High Pressure Turbine Blades

2000 ◽  
Author(s):  
Jeffrey A. Conner ◽  
Michael J. Weimer
Keyword(s):  
High Pressure ◽  
Life Cycle ◽  
Wall Thickness ◽  
Life Cycle Cost ◽  
Protective Coatings ◽  
Turbine Blades ◽  
High Pressure Turbine ◽  
Aluminide Coatings ◽  
Patent Applications ◽  
Blade Repair

With the evolution of advanced directionally solidified and single crystal nickel base superalloy turbine blades, managing life cycle costs of high pressure turbine (HPT) blades has become increasingly more difficult. Today’s advanced high pressure turbine blades in aero and aero-derivative turbines feature thin walls (<.030 inches), complex internal geometries, three dimensional (3D) aerodynamic shapes, multiple protective coatings and complex film cooling schemes. A major contributor to blade life cycle cost is the ability to perform multiple repairs without compromising the integrity of these complex components. Repair of HPT blades has traditionally fallen into two categories: mini or partial repairs where blade tips are restored and coated, and full repairs where flowpath coatings are removed, blade tips restored and new coating(s) applied to flowpath surfaces. Historically, the number of full repairs allowed ranges from zero to two based on numerous design considerations, one of which is maintaining a minimum wall thickness. Removal of protective coatings during full repair reduces wall thickness which limits the number of times a full repair can be performed. Furthermore, blades that have sufficient design allowance to permit two full repairs typically have very low yields at the second full repair due to thinning of airfoil walls below minimum thickness limits. The life of a given HPT blade is therefore controlled to a large degree by at what shop visit a full repair is performed. GE Engine Services has developed a new blade repair approach — Coating Rejuvenation — which significantly extends blade life by restoring protective coatings and maintaining wall thickness. Included in the Coating Rejuvenation repair are technologies that allow: removal of physical vapor deposited (PVD) thermal barrier coatings from external surfaces and cooling holes without impacting the bond coat; removal of oxidation and corrosion products from engine exposed coatings without impacting adjacent intact coating; restoration of coating composition to optimize environmental resistance; and upgrade of existing aluminide coatings to platinum aluminide coatings without removal of the existing coating. Combined together, these technologies can be used to support a comprehensive blade repair workscope plan that dramatically increases the life of HPT blades and decreases the life cycle cost for these components. Overviews of these technologies are presented in this paper along with information on how the technology was matured. Due to pending patent applications with the US Patent & Trademark Office as well as pending patent applications in other countries, significant technical detail cannot be presented at this time.

scholarly journals Probabilistic and Fuzzy Approaches for Estimating the Life Cycle Costs of Buildings under Conditions of Exposure to Risk

2019 ◽  
Vol 12 (1) ◽  
pp. 226 ◽  
Author(s):  
Edyta Plebankiewicz ◽  
Wiesław Meszek ◽  
Krzysztof Zima ◽  
Damian Wieczorek
Keyword(s):  
Life Cycle ◽  
Environmental Sustainability ◽  
Life Cycle Cost ◽  
Probabilistic Approach ◽  
Operating Costs ◽  
Life Cycle Costs ◽  
Financial Risks ◽  
Model Structure ◽  
Fuzzy Approach ◽  
Comparison Analysis

The paper discusses issues related to life cycle costs in construction. Life cycle cost is a key element in the assessment of environmental sustainability in construction and it provides a tool for the economic evaluation of alternative sustainability options exhibiting different capital, operating costs or resource usage. The authors reviewed selected models of estimating life cycle costs in construction, drew attention to the complex mathematical models developed so far, namely those which take into account only financial risks and those which involve the possibility of the influence of other risk factors and described the main assumptions accompanying the original model for estimating the whole life costs of buildings, including: reasons for choosing theory of possibility, division and parametrization of input data. The aim of this paper is to confirm the validity of the model structure assumptions adopted by the authors by comparing the originally selected fuzzy approach to calculating life cycle costs taking into account the risk with the probabilistic approach, as well as indicating the domain in which the probabilistic approach will complement the fuzzy approach chosen by the authors. The paper presents a comparison analysis of two approaches used in the authors’ model, a fuzzy and a probabilistic approach, recommended by the ISO standard 15686-5:2008. The authors used the Oracle Crystall Ball software in their simulations.

COMPARISON OF LIFE CYCLE COST OF CENTRALIZED AND SPLIT AIR CONDITIONING SYSTEMS

2016 ◽  
Vol 3 (1) ◽  
Author(s):  
Dharma Hagare ◽  
Jason Ho ◽  
Swapan Saha
Keyword(s):  
Life Cycle ◽  
Life Cycle Analysis ◽  
Life Cycle Cost ◽  
Air Conditioning ◽  
Residential Buildings ◽  
Operating Conditions ◽  
Central System ◽  
Operating Schedule ◽  
Ac Systems ◽  
Split System

Central and split systems are the two most common air conditioning (AC) systems used in residential applications. Central system employs one large unit to produce and distribute conditioned air through a system of ductwork. On the other hand, the split system, employs several small ACs. Each AC consisted of outdoor and indoor units to produce conditioned air directly to the designed area. Each system has distinct strengths and weaknesses. Depending on the structure of cooling area and operating schedule, the performance of each system will be different. The aim of this paper is to examine the impact of various parameters such as operating schedule and building characteristics to the performance of central and split AC systems over the 25 years of their operation. The life cycle analysis (LCA) considered essential factors which have significant impact on the energy consumption and both initial and operating costs of the two systems. All required sections of life cycle analysis are included according to the relevant Australian Standards. The results indicated that under standard operating conditions, central system is more economical and energy efficient than split system. However, when the flexibility in operation of split system is considered, there was a significant reduction in its operating cost, which was below that of central system. Overall, total life cycle cost of split system was slightly lower than central system. Also, considering the usage flexibility and the comfort of users, it appears that the split system is more suitable than the central AC system for residential buildings.

Construction of an evaluation system for selecting an appropriate waterproofing method for the roof of a building

2012 ◽  
Vol 39 (12) ◽  
pp. 1264-1273 ◽  
Author(s):  
Sung-Min Choi ◽  
Sang-Keun Oh ◽  
Chee-Ho Seo
Keyword(s):  
Life Cycle ◽  
Life Cycle Cost ◽  
Evaluation System ◽  
Evaluation Model ◽  
Evaluation Criteria ◽  
Value Engineering ◽  
Cost Evaluation ◽  
Final Decision ◽  
Decision Making Processes ◽  
And Performance

In this study, the discussion focus on the analysis of evaluation systems for selecting an appropriate waterproofing method, which involves a series of decision-making processes for providing unbiased, methodical, and suitable grounds to facilitate the final decision of the house owner. Thus, the research can potentially develop a decomposable model for validation and a deployable application model for the construction and performance-based design of materials. This paper has determined the performance evaluation criteria of 28 items and the evaluation index that is derived from the application of the value engineering procedure through the analysis for selecting the appropriate waterproofing method, and made a cost evaluation model of the risk based weighted life cycle cost so that life cycle cost evaluation can be performed in consideration of the risk.

Study and Application of the Life-Cycle Cost Control Model of Water Conservancy and Hydropower Project Based on Entropy and FAHP

2014 ◽  
Vol 1046 ◽  
pp. 564-568 ◽  
Author(s):  
Chun Yan Wang ◽  
Ning Wei
Keyword(s):  
Life Cycle ◽  
Life Cycle Cost ◽  
Cost Control ◽  
Comprehensive Evaluation ◽  
Evaluation Model ◽  
Fuzzy Comprehensive Evaluation ◽  
Life Cycle Management ◽  
Project Cost ◽  
Hydro Power ◽  
Water Conservancy

How to implement the life-cycle management of water conservancy and hydro power project cost effectively, and how to distinguish the influence degree of different factors on project cost stage management. This is a key problem in project cost control. In this paper, based on the influence of each factor on the overall evaluation goal influence, FAHP is applied to set up Fuzzy Comprehensive Evaluation Model. Aiming at the variability characteristics of factors in each stage, the information entropy is used to determine the objective weight in the model, in combination with AHP the subjective weights to determine the weight.

scholarly journals On the matter of the terminology of aeronautical structures survivability

Dependability ◽  
2019 ◽  
Vol 19 (2) ◽  
pp. 42-47
Author(s):  
V. V. Efimov
Keyword(s):  
Damage Tolerance ◽  
Probabilistic Approach ◽  
Probability Of Failure ◽  
Operating Conditions ◽  
Operating Efficiency ◽  
Extreme Conditions ◽  
Flight Safety ◽  
Efficient Operation ◽  
Literary Sources ◽  
Definition Of

Aim. The paper examines the existing definitions of survivability and damage tolerance (operational survivability) of aeronautical structures. An attempt is made to unambiguously define the survivability of aeronautical structures that can subsequently be extended to an aircraft as a whole and other complex technical items. The primary goal of this paper is to clearly distinguish between dependability and survivability. In order to ensure efficient operation and flight safety, an aircraft must possess airworthiness, a comprehensive characteristic of an aircraft that is defined by the implemented design principles and solutions and that allows performing safe flights under expected conditions and under the established methods of operation. The expected operating conditions are described in the Aviation Regulations – Airworthiness Requirements. Despite the fact that compliance with the Airworthiness Requirements ensures a sufficiently high level of flight safety, the most vital structural components are designed in such a way as to remain operable even under extreme conditions beyond the expected operating conditions. But dependability cannot be responsible for operability outside the expected operating conditions. Conclusion suggests itself that under extreme conditions beyond the expected operating conditions operability is to be ensured by another property, i.e. survivability. Methods. This research was conducted using the logical and probabilistic approaches. The author examined literary sources primarily dedicated to the matters of dependability and survivability of aeronautical structures, as well as other complex technical items. In order to ensure an optimal understanding of the differences and correlation between the concepts of dependability and survivability, the probabilistic approach was used. Results. Upon the analysis of literary sources, survivability was defined as the property of an item to retain in time the capability to perform the required functions under extreme conditions beyond the expected operating conditions under the specified methods of maintenance, storage and transportation. Additionally, the paper proposes the definition of damage tolerance (operational survivability) as the property of an item to retain in time the capability to perform the required functions under extreme conditions beyond the expected operating conditions depending on the methods of maintenance, storage and transportation. The probabilistic approach to the delimitation of the concepts of dependability and survivability of aeronautical structures was examined using the known indicator of operating efficiency of a transport aircraft that is represented as the mathematical expectation of the efficiency indicator. An aircraft may be either in the expected operating conditions or in extreme conditions beyond the expected operating conditions. No third option exists. Then, the sum of the probabilities of an aircraft encountering such conditions must be equal to one. The probability of no-failure can be calculated by means of the probability of the contrary event, i.e. the probability of failure that can be represented as the product of the probability of an aircraft encountering certain operating conditions and the probability of failure in such conditions. For the case of extreme conditions beyond the expected conditions the well-known concepts of perishability and vulnerability with the author’s improvements can be used. Conclusions. A definition of survivability was obtained that is clearly different from the concepts of dependability and fail-safety. Additionally, the concept of damage tolerance (operational survivability) was proposed that was introduced similarly to the previously introduced concept of operational dependability.

scholarly journals On the matter of the terminology of aeronautical structures survivability

Dependability ◽  
2019 ◽  
Vol 19 (2) ◽  
pp. 43-48
Author(s):  
V. V. Efimov
Keyword(s):  
Damage Tolerance ◽  
Probabilistic Approach ◽  
Probability Of Failure ◽  
Operating Conditions ◽  
Operating Efficiency ◽  
Extreme Conditions ◽  
Flight Safety ◽  
Efficient Operation ◽  
Literary Sources ◽  
Definition Of

Aim. The paper examines the existing definitions of survivability and damage tolerance (operational survivability) of aeronautical structures. An attempt is made to unambiguously define the survivability of aeronautical structures that can subsequently be extended to an aircraft as a whole and other complex technical items. The primary goal of this paper is to clearly distinguish between dependability and survivability. In order to ensure efficient operation and flight safety, an aircraft must possess airworthiness, a comprehensive characteristic of an aircraft that is defined by the implemented design principles and solutions and that allows performing safe flights under expected conditions and under the established methods of operation. The expected operating conditions are described in the Aviation Regulations – Airworthiness Requirements. Despite the fact that compliance with the Airworthiness Requirements ensures a sufficiently high level of flight safety, the most vital structural components are designed in such a way as to remain operable even under extreme conditions beyond the expected operating conditions. But dependability cannot be responsible for operability outside the expected operating conditions. Conclusion suggests itself that under extreme conditions beyond the expected operating conditions operability is to be ensured by another property, i.e. survivability. Methods. This research was conducted using the logical and probabilistic approaches. The author examined literary sources primarily dedicated to the matters of dependability and survivability of aeronautical structures, as well as other complex technical items. In order to ensure an optimal understanding of the differences and correlation between the concepts of dependability and survivability, the probabilistic approach was used. Results. Upon the analysis of literary sources, survivability was defined as the property of an item to retain in time the capability to perform the required functions under extreme conditions beyond the expected operating conditions under the specified methods of maintenance, storage and transportation. Additionally, the paper proposes the definition of damage tolerance (operational survivability) as the property of an item to retain in time the capability to perform the required functions under extreme conditions beyond the expected operating conditions depending on the methods of maintenance, storage and transportation. The probabilistic approach to the delimitation of the concepts of dependability and survivability of aeronautical structures was examined using the known indicator of operating efficiency of a transport aircraft that is represented as the mathematical expectation of the efficiency indicator. An aircraft may be either in the expected operating conditions or in extreme conditions beyond the expected operating conditions. No third option exists. Then, the sum of the probabilities of an aircraft encountering such conditions must be equal to one. The probability of no-failure can be calculated by means of the probability of the contrary event, i.e. the probability of failure that can be represented as the product of the probability of an aircraft encountering certain operating conditions and the probability of failure in such conditions. For the case of extreme conditions beyond the expected conditions the well-known concepts of perishability and vulnerability with the author’s improvements can be used. Conclusions. A definition of survivability was obtained that is clearly different from the concepts of dependability and fail-safety. Additionally, the concept of damage tolerance (operational survivability) was proposed that was introduced similarly to the previously introduced concept of operational dependability.

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