scholarly journals Maintenance Modelling of Ceramic Claddings in Pitched Roofs Based on the Evaluation of Their In Situ Degradation Condition

2020 ◽  
Vol 5 (9) ◽  
pp. 77
Author(s):  
Cláudia Ferreira ◽  
Ana Silva ◽  
Jorge de Brito ◽  
Ilídio S. Dias ◽  
Inês Flores-Colen
Keyword(s):  
Service Life ◽  
Maintenance Strategies ◽  
Total Replacement ◽  
Remaining Service Life ◽  
In Situ Degradation ◽  
Maintenance Policies ◽  
And Performance ◽  
The Impact ◽  
Maintenance Model

Existing maintenance policies have several limitations, mainly due to the lack of knowledge regarding the durability and performance of buildings. Usually, the maintenance policies are insufficiently accurate, neglecting the risk of failure over time and the global costs associated with repairs. In this study, a condition-based maintenance model, based on Petri nets, is proposed to evaluate the impact of three maintenance strategies of ceramic claddings in pitched roofs (CCPR): MS1—only total replacement; MS2—composed of total replacement and minor intervention and MS3—composed of total replacement, minor intervention and cleaning operations. In this study, 146 CCPR were inspected in situ, with a total area of 43,991.6 m2. The remaining service life of the CCPR; the global costs over the claddings’ lifetime (considering inspection, maintenance, replacement and disposal costs); the claddings’ degradation condition and the number of replacements during the time horizon are used to evaluate the performance of the different maintenance strategies through a simplified multi-criteria analysis. The results show that the gains in performance, in terms of expected service life and durability, of the consideration of preventive maintenance actions (minor interventions or cleaning operations) outweigh the increase of the operation costs.

scholarly journals Condition-Based Maintenance Strategies to Enhance the Durability of ETICS

2021 ◽  
Vol 13 (12) ◽  
pp. 6677
Author(s):  
Cláudia Ferreira ◽  
Ana Silva ◽  
Jorge de Brito ◽  
Ilídio S. Dias ◽  
Inês Flores-Colen
Keyword(s):  
Service Life ◽  
Condition Based Maintenance ◽  
Performance Criteria ◽  
Time Interval ◽  
Maintenance Strategies ◽  
Total Replacement ◽  
Remaining Service Life ◽  
The Impact ◽  
Maintenance Model

The increase of awareness with sustainability and the desire of reducing the energy consumption in the construction sector haved increased the application of External Thermal Insulation Composite Systems (ETICS) across Europe in the last decades. Nevertheless, the implementation of appropriate maintenance strategies is still neglected. The aim of this study is to analyse the impact of different maintenance strategies. For that purpose, a condition-based maintenance model, based on Petri nets, is used to evaluate three maintenance strategies: MS1—total replacement only; MS2—combination of minor intervention and total replacement; and MS3—combination of cleaning operations, minor intervention, and total replacement. In the end, a multi-criteria analysis is used to discuss the impact of the three maintenance strategies proposed, evaluating the remaining service life, the global costs over time, the ETICS’ degradation condition, and the number of replacements (end of service life) over the time horizon. For this purpose, a sample of 378 ETICS was analysed, based on in situ visual inspections, carried out in Portugal. The results from this study reveal that maintenance plays an important role to increase the durability of ETICS, and therefore their sustainability. Regular maintenance can promote the extension of the ETICS’s service life between 88% and 159% (between 15 to 27 years), improve the global degradation condition of the ETICS, and reduce the impact on users by reducing the number of deeper interventions. Further research is essential to optimise the maintenance strategies (time interval between inspections, stakeholders’ performance criteria, and environmental exposure).

scholarly journals Fleet Resilience: Evaluating Maintenance Strategies in Critical Equipment

2020 ◽  
Vol 11 (1) ◽  
pp. 38
Author(s):  
Orlando Durán ◽  
Javier Aguilar ◽  
Andrea Capaldo ◽  
Adolfo Arata
Keyword(s):  
Application Study ◽  
System Availability ◽  
Maintenance Strategies ◽  
Resilience Index ◽  
Reliability Block Diagrams ◽  
Maintenance Policies ◽  
Definition Of ◽  
The Impact ◽  
Important System ◽  
Intrinsic Characteristic

Resilience is an intrinsic characteristic of systems. Through it, the capacity of a system to react to the existence of disruptive events is expressed. A series of metrics to represent systems’ resilience have been proposed, however, only one indicator relates the availability of the system to this characteristic. With such a metric, it is possible to relate the topological aspects of a system and the resources available in order to be able to promptly respond to the loss of performance as a result of unexpected events. This work proposes the adaptation and application of such a resilience index to assess the influence of different maintenance strategies and topologies in fleets’ resilience. In addition, an application study considering an actual mining fleet is provided. A set of critical assets was identified and represented using reliability block diagrams. Monte Carlo simulation experiments were conducted and the system availability data were extracted. Resilience indexes were obtained in order to carry out the definition of the best maintenance policies in critical equipment and the assessment of the impact of modifying system redundancies. The main results of this work lead to the overall conclusion that redundancy is an important system attribute in order to improve resiliency along time.

Structural Impact in FPSO Life Extension: A Class Perspective

2013 ◽  
Author(s):  
Christiane L. Machado ◽  
Sudheer Chand
Keyword(s):  
Service Life ◽  
Oil And Gas ◽  
Structural Response ◽  
Oil And Gas Industry ◽  
Environmental Data ◽  
Life Extension ◽  
Element Analysis ◽  
Actual Performance ◽  
Remaining Service Life ◽  
The Impact

The Offshore Oil and Gas Industry has converted a large number of units from trading tankers and carriers into Floating Production, Storage and Offloading units (FPSOs). Several of these have been moored offshore Brazil during the last 15 years. Following the discovery of offshore pre-salt fields some years ago, demand for FPSOs has increased, and the forecasts for productive field lives have grown. The result of these developments is the need to extend the service lives of existing FPSOs. The main aim of this study is to investigate FPSO structural response to environmental conditions and functional loads, considering the actual available tools for numerical simulations and Rule requirements, which currently are basic requirements for design review for Classification. The procedure was developed from one selected FPSO converted from a trading Very Large Crude Carrier (VLCC) tanker approximately 15 years ago and includes investigation of the impact on hull behavior comparing the motion analyses of the production unit under environmental data and software capabilities available at the period of conversion and actual performance: variances in the environmental (sea scatter diagrams) datasets; updates to Classification requirements for defining offloading conditions, environmental loads, acceptance criteria and remaining fatigue life (RFL); and incorporating the most recent gauged thickness for primary structure. The selected FPSO was evaluated according to prescriptive Rule requirements and also using finite element analysis, taking into account the previous conditions of Classification approval as well as the actual requirements and available data. Structural analysis included one global model and some local refined models to address strength, buckling and fatigue capacity of the typical portions/connections of the hull. The comparisons performed from the results of these analyses are a crucial step toward understanding the structural capacity of the FPSO at the conversion stage, its performance during the last 15 years, and its remaining service life. Differences were tabulated and evaluated so that a more precise level of uncertainty could be achieved for predicting the estimated remaining service life, and consequently, a new and dedicated approach to investigate the existing FPSO fleet is being generated.

scholarly journals ASR: Practical investigative techniques and field monitoring systems used to assess ASR for service life modeling.

2019 ◽  
Vol 289 ◽  
pp. 08004
Author(s):  
Irene Matteini ◽  
Paul Noyce ◽  
Gina Crevello
Keyword(s):  
Service Life ◽  
Significant Risk ◽  
Field Monitoring ◽  
Alkali Silica Reaction ◽  
Material Degradation ◽  
Deterioration Mechanism ◽  
Investigative Techniques ◽  
The Impact

Alkali Silica Reaction (ASR) is a common deterioration mechanism affecting many concrete structures of any type and age. Initially identified more than 60 years ago (Stanton, 1930), this mechanism is based on the chemical reactions between certain siliceous minerals present in the aggregate and the alkalinity of the concrete in the presence of moisture (internal RH). While certain deterioration patterns are clearly associated with ASR, such as gel exudation, aggregate expansion, and characteristic cracking, the material degradation can often be misdiagnosed to the untrained eye. In addition, certain elements of a structure can be severely affected while neighboring elements of the same batch/ mix design do not bear signs of deterioration or impact. Thus far, in situ field monitoring of ASR affected structures is related to moisture measurements, electrical resistivity, expansion, service life models are based on fracture mechanics of the aggregate. The impact to the concrete is loss of integrity, decreased compressive strength, shear and tensile strength. Some observed structures have split, with such force, that the concrete structure had cracks greater than 25mm where steel retention bands have split. The authors of this paper were engaged in two instances to provide service life assessments for ‘corrosion related degradation’ on ASR affected structures. In all instances the elements which were assessed were structural, load bearing elements, which if failed could pose a significant risk to owner, user, or end recipient. The need to develop an assessment technique for monitoring and service life assessments which are practical and efficient is being developed. The paper will discuss the development of the approach, from visual indicators identifying condition hierarchies, to long term condition monitoring for various concrete parameters combined with laboratory testing (expansion and residual alkalis) and mathematical modeling. Three case studies will be presented to illustrate conditions and process.

scholarly journals The challenges of an in situ validation of a non-equilibrium model of soil heat and moisture dynamics during fires

2020 ◽  
Author(s):  
William J. Massman
Keyword(s):  
Heat Flux ◽  
Equilibrium Model ◽  
Soil Heat Flux ◽  
Flow Equation ◽  
Vapor Source ◽  
Apparent Thermal Conductivity ◽  
And Performance ◽  
The Impact ◽  
Non Equilibrium

Abstract. With the increasing frequency and severity of fire there is an increasing desire to better manage fuels and minimize, as much as possible, the impacts of fire on soils and other natural resources. Piling and/or burning slash is one method of managing fuels and reducing the risk and consequences of wildfire, but the repercussions to the soil, although very localized, can be significant and often irreversible. In an effort to provide a tool to better understand the impact of fire on soils, this study outlines the improvements to and the in-situ validation of a non-equilibrium model for simulating the coupled interactions and transport of heat, moisture and water vapor during fires. Improvements to the model eliminate two important (but heretofore universally overlooked) inconsistencies: one that describes the relationship between evaporation and condensation in the parameterization of the non-equilibrium vapor source term and the other, is the incorrect use of the apparent thermal conductivity in the soil heat flow equation. The first of these enhanced the stability and performance of the model. The second is an important improvement in the model's physical realism, but had less of an impact on the model's performance and stability than the first. The model validation uses (in-situ temperature, soil moisture, and heat flux) data obtained in a 2004 experimental slash pile burn. Important temperature dependent corrections to the instruments used for measuring soil heat flux and moisture are also discussed and assessed. Despite any possible ambiguities in the calibration the sensors or the simplicity of the parameterization of the surface heating function, the difficulties and complexities of formulating the upper boundary condition, and the obvious complexities of the dynamic response of the soil's temperature and heat flux, the model produced at least a very credible, if not surprisingly good, simulation of the observed data. This study then continues with a discussion and sensitivity analysis of some important feedbacks (some of which are well known and others that are more hypothetical) that are not included in the present (or any extant) model, but undoubtedly are dynamically influencing the physical properties of the soil in-situ during the fire and thereby modulating the behavior of the soil temperature and moisture. This manuscript concludes with a list of possible future observational and modeling studies and how they would advance the research and findings discussed here.

Prediction of the Remaining Service Life of Superheater and Reheater Tubes in Coal-Biomass Fired Power Plants

2013 ◽  
Vol 856 ◽  
pp. 343-348 ◽  
Author(s):  
Mohammad Asgaryan ◽  
Nigel Simms ◽  
Shao Min Wu
Keyword(s):  
Service Life ◽  
Power Plants ◽  
Operating Conditions ◽  
Fireside Corrosion ◽  
Remaining Service Life ◽  
Boiler Efficiency ◽  
Early Failures ◽  
Oxidation Damage ◽  
Type Of Failure ◽  
The Impact

Burning biomass in power plants is believed to result in severe fireside corrosion of superheater/reheater tubing and cause unexpected early failures of tubes. Morover, higher operating temeprtures and pressures (to increase the boiler efficiency) will also increase the risk of fireside and steamside oxidation damage to the boiler tubing and lead to shorter component lives. Predicting the remaining service life of superheater/reheater tubes in coal-biomass fired power plants is therefore an important aspect of managing such power plants. The path to this type of failure of tubes involves five processes: combustion, deposition, fireside corrosion, steam-side oxidation, and creep. To fully understand the impact of new fuel mixes and changing operating conditions on such failures, an integrated model of all of these processes is required. This work has produced an integrated set of models and so predicted the remaining life of tubes based on the conceptual and mathematical frameworks developed.

scholarly journals How Long Can a Wood Flooring System Last?

Buildings ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 23
Author(s):  
Pedro Coelho ◽  
Ana Silva ◽  
Jorge de Brito
Keyword(s):  
Service Life ◽  
Life Prediction ◽  
Degradation Mechanisms ◽  
High Importance ◽  
Wood Flooring ◽  
Renewable Material ◽  
Life Values ◽  
And Performance ◽  
The Impact ◽  
Over Time

Wood is a natural, sustainable, and renewable material, which has been used as flooring for centuries, but not enough is known about its durability and performance over time when subjected to different degradation agents. This study proposes a methodology for the service life prediction of wood flooring systems, considering the impact of different factors that influence the floors’ durability. For that purpose, a fieldwork survey is performed to evaluate the degradation phenomena of 96 indoor wood floorings in-use conditions, located in Portugal. The data collected are converted into degradation patterns that graphically illustrate the loss of performance of wood floorings over time. An estimated service life of 44 years is obtained. This study thus allows quantifying the impact of various characteristics on the indoor wood floorings’ service life. The results reveal the high importance of the type of protection, the type of wood, and the type of floor (with a range of estimated service life values of around 18, 17 and 16 years, respectively). This study is a first step to understanding the degradation mechanisms of the wood flooring systems, in order to extend their service life, while allowing optimising of maintenance actions, thus promoting the durability and sustainability of these floorings.

Service Life and Life of Service: The Maintenance Commitments

1998 ◽  
Vol 1650 (1) ◽  
pp. 5-9
Author(s):  
L. G. (Gray)Byrd
Keyword(s):  
Service Life ◽  
Service Research ◽  
Highway Maintenance ◽  
Repair Work ◽  
User Costs ◽  
Research And Innovation ◽  
Maintenance Program ◽  
Performance Specifications ◽  
Maintenance Policies ◽  
The Impact

The magnitude of today’s highway maintenance challenge, the impact of research on maintenance, basic objectives that should drive a maintenance program, and the progress made in meeting them over the last 4 decades are discussed. Highway maintenance should include the objectives of providing a consistently safe, comfortable, and efficient travel way for highway users and a safe environment for maintenance crews; providing optimum service life; maintaining as-built capacity and reliability; inviting, supporting, and using research and innovation; and performing with professionalism, competence, and diligence. Some of the challenges in meeting these objectives today are accelerating rates of deterioration, limited time available to work, complex interchanges and crowded rights-of-way, environmental restrictions, a litigious society, and public skepticism about all government functions. Three categories of responses are technologies, policies, and professionalism. A significant array of new, innovative tools and other products of research are making maintenance technology more effective. Maintenance managers need to be activists in promoting progressive policies in providing as-built capacity while performing maintenance and repair work and in procuring products and services. Maintenance policies should include recognition of user costs, use of performance specifications, fabrication of off-site repair components, design of repairable highway systems, use of corrosion-resistant materials, privatization of segments of the maintenance program, and establishment of an international maintenance technology reference program. Individual professionals must embrace continuing education, environmental sensitivity, community service, research and development, innovative management, and societal and political responsibilities.

scholarly journals Reliability-based life cycle costing analysis for embedded rails in level crossings

2019 ◽  
Vol 234 (8) ◽  
pp. 821-833
Author(s):  
Yue Shang ◽  
Martine van den Boomen ◽  
Amy de Man ◽  
ARM (Rogier) Wolfert
Keyword(s):  
Life Cycle ◽  
Asset Management ◽  
Life Cycle Cost ◽  
Life Cycle Costing ◽  
Maintenance Strategies ◽  
Failure Data ◽  
Maintenance Policies ◽  
Age Replacement ◽  
The Impact ◽  
Costing Analysis

Reliability-based life cycle costing analysis (LCCA) supports optimized decisions on capital and operational expenditures for engineering asset management. In addition, it allows investigation of the impact of maintenance decisions on designing the service life of assets. The application of reliability-based LCCA in railway practice is challenging, as there is limited research with regard to integrating maintenance strategies, reliability and costs especially for embedded rail systems. Therefore, in this research, an LCCA model for these embedded rail system assets has been developed, which shows the optimum between the actual reliability profile, financial parameters and maintenance policies for specific variable conditions. This model incorporates both the uncertainties associated with degradation and maintenance strategies which have been integrated into a discounted age replacement model. This model facilitates a better understanding about the interaction among life cycle cost, rail degradation and maintenance strategies for a set of variable conditions. The output supports decision making on rail replacement and/or maintenance engineering. The model is demonstrated in a case study and validated with available (real) failure data from Dutch railroad service contractors. The potential of the applicability to ballasted tracks is also demonstrated.

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