An optimal inspection and replacement policy for a two-unit system

2018 ◽  
Vol 232 (6) ◽  
pp. 766-776 ◽  
Author(s):  
Li Yang ◽  
Yu Zhao ◽  
Xiaobing Ma ◽  
Qingan Qiu
Keyword(s):  
Replacement Policy ◽  
Offshore Wind ◽  
Maintenance Cost ◽  
Offshore Wind Turbine ◽  
Maintenance Policy ◽  
Preventive Replacement ◽  
Unit System ◽  
Binary State ◽  
Preventive Maintenance Policy

We study a preventive maintenance policy for a system composed of two units, a binary state unit and a three-state unit. Failures of both units are hard and self-announcing. The intermediate, defective state for the second unit can be regarded as a signal of pending failures. Unit 2 is inspected when its age attains integral multiples of interval [Formula: see text] and when unit 1 fails, and preventive replacement is immediate once the defective state is revealed. This strategy could be extended by further providing preventive replacement for the first unit. A case study on an offshore wind turbine is presented for illustration. We find that opportunistic maintenance schemed for both units could effectively reduce the maintenance cost.

scholarly journals Optimal Maintenance Probabilities and Preventive Replacement Maintenance Policy for Photocopy Machines

2021 ◽  
Author(s):  
Nse Udoh ◽  
Akaninyene Udom ◽  
Fredrick Ohaegbunem
Keyword(s):  
Minimum Cost ◽  
Maintenance Cost ◽  
Logistic Distribution ◽  
Maintenance Policy ◽  
Preventive Replacement ◽  
Maintenance Time ◽  
Replacement Model ◽  
Cumulative Function ◽  
Optimal Maintenance ◽  
Preventive Maintenance Policy

The need for suitable replacement policies are essential to minimize down time, maintenance cost and maximize the availability and reliability of equipment. On this premise, this work models the failure rate of Photocopy machines and obtain its optimal preventive maintenance policy that would prevent damage and its attendant losses to both users and end-product consumers. The failure distribution of the machine was shown to follow the Log-Logistic distribution with shape parameter, αˆ=1.723339368 and scale parameter, βˆ=763.9219635. Optimal probabilities of the distribution were obtained and utilized in both the cumulative failure function and cumulative hazard function-based replacement models to formulate a replacement maintenance policy for the machine. The failure cumulative function-based replacement model was found to be a better model which yields optimal replacement maintenance time of 166 hours at a minimum cost of 113 Naira for maintaining the machine per cycle time with 96% availability, 94% reliability and 0.07% chance of failure occurrence in the machine.

scholarly journals Impact of Typhoons on Floating Offshore Wind Turbines: A Case Study of Typhoon Mangkhut

2021 ◽  
Vol 9 (5) ◽  
pp. 543
Author(s):  
Jiawen Li ◽  
Jingyu Bian ◽  
Yuxiang Ma ◽  
Yichen Jiang
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Safety Evaluation ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Motion Response ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines ◽  
Coupling Motion

A typhoon is a restrictive factor in the development of floating wind power in China. However, the influences of multistage typhoon wind and waves on offshore wind turbines have not yet been studied. Based on Typhoon Mangkhut, in this study, the characteristics of the motion response and structural loads of an offshore wind turbine are investigated during the travel process. For this purpose, a framework is established and verified for investigating the typhoon-induced effects of offshore wind turbines, including a multistage typhoon wave field and a coupled dynamic model of offshore wind turbines. On this basis, the motion response and structural loads of different stages are calculated and analyzed systematically. The results show that the maximum response does not exactly correspond to the maximum wave or wind stage. Considering only the maximum wave height or wind speed may underestimate the motion response during the traveling process of the typhoon, which has problems in guiding the anti-typhoon design of offshore wind turbines. In addition, the coupling motion between the floating foundation and turbine should be considered in the safety evaluation of the floating offshore wind turbine under typhoon conditions.

Optimizing the Cost and Reliability of Shared Anchors in an Array of Floating Offshore Wind Turbines

2021 ◽  
Author(s):  
Michael Devin ◽  
Bryony DuPont ◽  
Spencer Hallowell ◽  
Sanjay Arwade
Keyword(s):  
Optimization Algorithm ◽  
System Reliability ◽  
Failure Modes ◽  
The United States ◽  
Offshore Wind ◽  
Bayesian Optimization ◽  
Maintenance Cost ◽  
Offshore Wind Turbine ◽  
Trade Offs ◽  
Floating Offshore Wind Turbines

Abstract Commercial floating offshore wind projects are expected to emerge in the United States by the end of this decade. Currently, however, high costs for the technology limit its commercial viability, and a lack of data regarding system reliability heightens project risk. This work presents an optimization algorithm to examine the trade-offs between cost and reliability for a floating offshore wind array that uses shared anchoring. Combining a multivariable genetic algorithm with elements of Bayesian optimization, the optimization algorithm selectively increases anchor strengths to minimize the added costs of failure for a large floating wind farm in the Gulf of Maine under survival load conditions. The algorithm uses an evaluation function that computes the probability of mooring system failure, then calculates the expected maintenance costs of a failure via a Monte Carlo method. A cost sensitivity analysis is also performed to compare results for a range of maintenance cost profiles. The results indicate that virtually all of the farm's anchors are strengthened in the minimum cost solution. Anchor strength is in- creased between 5-35% depending on farm location, with anchor strength nearest the export cable being increased the most. The optimal solutions maintain a failure probability of 1.25%, demonstrating the trade-off point between cost and reliability. System reliability was found to be particularly sensitive to changes in turbine costs and downtime, suggest- ing further research into floating offshore wind turbine failure modes in extreme loading conditions could be particularly impactful in reducing project uncertainty.

Evaluating the Coupledness of the Aerodynamics and Hydrodynamics on the Estimation of Fatigue Damage Equivalent Load for a Floating Offshore Wind Platform

2018 ◽  
Author(s):  
Samuel Kanner ◽  
Bingbin Yu
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Environmental Conditions ◽  
Offshore Wind ◽  
Coupled Analysis ◽  
Offshore Wind Turbine ◽  
Wave Conditions ◽  
Equivalent Load ◽  
The Waves

In this research, the estimation of the fatigue life of a semi-submersible floating offshore wind platform is considered. In order to accurately estimate the fatigue life of a platform, coupled aerodynamic-hydrodynamic simulations are performed to obtain dynamic stress values. The simulations are performed at a multitude of representative environmental states, or “bins,” which can mimic the conditions the structure may endure at a given site, per ABS Floating Offshore Wind Turbine Installation guidelines. To accurately represent the variety of wind and wave conditions, the number of environmental states can be of the order of 103. Unlike other offshore structures, both the wind and wave conditions must be accounted for, which are generally considered independent parameters, drastically increasing the number of states. The stress timeseries from these simulations can be used to estimate the damage at a particular location on the structure by using commonly accepted methods, such as the rainflow counting algorithm. The damage due to either the winds or the waves can be estimated by using a frequency decomposition of the stress timeseries. In this paper, a similar decoupled approach is used to attempt to recover the damages induced from these coupled simulations. Although it is well-known that a coupled, aero-hydro analysis is necessary in order to accurately simulate the nonlinear rigid-body motions of the platform, it is less clear if the same statement could be made about the fatigue properties of the platform. In one approach, the fatigue damage equivalent load is calculated independently from both scatter diagrams of the waves and a rose diagram of the wind. De-coupled simulations are performed to estimate the response at an all-encompassing range of environmental conditions. A database of responses based on these environmental conditions is constructed. The likelihood of occurrence at a case-study site is used to compare the damage equivalent from the coupled simulations. The OC5 platform in the Borssele wind farm zone is used as a case-study and the damage equivalent load from the de-coupled methods are compared to those from the coupled analysis in order to assess these methodologies.

scholarly journals Maintenance Grouping Optimization for Offshore Wind Turbine Considering Opportunities Based on Rolling Horizon Approach

2018 ◽  
Vol 25 (2) ◽  
pp. 123-131 ◽  
Author(s):  
Yang Lua ◽  
Liping Suna ◽  
Jichuan Kanga ◽  
Xinyue Zhang
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Poor Performance ◽  
Offshore Wind ◽  
Maintenance Cost ◽  
Offshore Wind Turbine ◽  
Rolling Horizon ◽  
Imperfect Maintenance ◽  
Opportunistic Maintenance ◽  
Maintenance Schedule

Abstract In future, offshore wind turbines may be consider a crucial part in the supply of energy. Maintenance processes are directed to attain a safe and reliable operation of offshore machines and wind turbines. In this paper, an opportunistic maintenance strategy for offshore wind turbine is proposed, considering imperfect maintenance and the preventive maintenance durations. Reliability Centric Maintenance serves as a proactive tactic to operations and maintenance by inhibiting the possible reasons of poor performance and controlling failures. Other components can implement the opportunistic preventive maintenances if one component has reached its reliability threshold. According to the rolling horizon approach, it is of great importance to update the maintenance planning for the sake of the short-term information. By figuring out the best combination, the maintenance schedule in the mission time has been finally determined. Failure information are obtained from previous studies to accomplish the calculations. The outcomes indicate that the maintenance cost has been dramatically reduced through the application of opportunistic maintenance.

scholarly journals ON PREVENTIVE MAINTENANCE POLICY FOR WAVE DISSIPATING BLOCKS COVERING CAISSON BREAKWATER

2018 ◽  
pp. 72
Author(s):  
Takao Ota ◽  
Hiroyuki Kawamura ◽  
Yoshiharu Matsumi ◽  
Junji Koyanagi ◽  
Takashi Satow
Keyword(s):  
Mathematical Model ◽  
Preventive Maintenance ◽  
Maintenance Cost ◽  
Maintenance Policy ◽  
Reliability Engineering ◽  
Coastal Structures ◽  
Service Period ◽  
Caisson Breakwater ◽  
External Forces ◽  
Preventive Maintenance Policy

The infrastructures are required to keep a certain level of performance during the duration of service. Because the performance of the infrastructures including harbor and coastal structures deteriorates due to aging and damage that is caused by the action of external forces, it is necessary to perform appropriate maintenance. Satow et al. (2009) proposed a mathematical model for the preventive maintenance of wave dissipating blocks based on the method of the reliability engineering. They also derived the expected maintenance cost over the in service period and the optimal preventive maintenance policy. In this study, the optimal threshold for preventive maintenance to minimize the expected maintenance cost is determined for the wave dissipating blocks covering caisson breakwater by using the above model.

Optimal Preventive Maintenance Policy Under a Budget Constraint

2008 ◽  
Author(s):  
Inderjeet Singh ◽  
Elmira Popova ◽  
Ernie Kee
Keyword(s):  
Preventive Maintenance ◽  
Real Data ◽  
Integer Program ◽  
South Texas ◽  
Maintenance Cost ◽  
Maintenance Policy ◽  
Data Set ◽  
Finite Time Horizon ◽  
Preventive Maintenance Policy ◽  
Operating Company

We design an optimal preventive maintenance policy for a system of N items that minimizes the total expected maintenance cost. We assume that the budget for preventive maintenance is limited and constrained. The problem has a finite time horizon and we consider constant inter-preventive maintenance times for every item. The resulting nonlinear optimization problem is reformulated as a binary integer program and computation results are presented on a real data set from South Texas Project Nuclear Operating Company in Bay City, Texas, USA.

Creating strategic couplings in global production networks: regional institutions and lead firm investment in the Humber region, UK

2019 ◽  
Vol 19 (4) ◽  
pp. 853-872 ◽  
Author(s):  
Stuart Dawley ◽  
Danny MacKinnon ◽  
Robert Pollock
Keyword(s):  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Production Networks ◽  
Global Production Networks ◽  
Regional Institutions ◽  
Political Environments ◽  
Firm Investments ◽  
Adaptive Coupling ◽  
Lead Firm

Abstract This article aims to unpack and analyse the institutional and political dynamics of strategic coupling from a host region perspective, adopting an actor-centred approach that focuses on regional institutions’ efforts to attract and embed lead firm investments within global production networks. We are particularly concerned with understanding the strategic agency and shifting coalitions of actors that create couplings and shape their evolution over time. This involves opening up the institutional underpinnings of strategic couplings by focusing more specifically on the key episodes in their creation and the organisation of the temporary coalitions that do the work of creating couplings. This approach is operationalised through a case study of the Siemens offshore wind turbine plant in the Humber region of England. In conclusion, we emphasise the need for regional institutions to develop adaptive coupling creation strategies that co-evolve with the reconfiguration of production networks and the reshaping of national institutional and political environments.

scholarly journals Optimizing preventive maintenance policy: A data-driven application for a light rail braking system

2017 ◽  
Vol 231 (5) ◽  
pp. 534-545 ◽  
Author(s):  
Francesco Corman ◽  
Sander Kraijema ◽  
Milinko Godjevac ◽  
Gabriel Lodewijks
Keyword(s):  
Preventive Maintenance ◽  
Data Driven ◽  
Sequential Optimization ◽  
Maintenance Cost ◽  
Light Rail ◽  
Maintenance Policy ◽  
Maintenance Costs ◽  
Braking System ◽  
Optimal Maintenance Policy ◽  
Preventive Maintenance Policy

This article presents a case study determining the optimal preventive maintenance policy for a light rail rolling stock system in terms of reliability, availability, and maintenance costs. The maintenance policy defines one of the three predefined preventive maintenance actions at fixed time-based intervals for each of the subsystems of the braking system. Based on work, maintenance, and failure data, we model the reliability degradation of the system and its subsystems under the current maintenance policy by a Weibull distribution. We then analytically determine the relation between reliability, availability, and maintenance costs. We validate the model against recorded reliability and availability and get further insights by a dedicated sensitivity analysis. The model is then used in a sequential optimization framework determining preventive maintenance intervals to improve on the key performance indicators. We show the potential of data-driven modelling to determine optimal maintenance policy: same system availability and reliability can be achieved with 30% maintenance cost reduction, by prolonging the intervals and re-grouping maintenance actions.

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