Total Maintenance Cost Research Articles

Retrofitting Vessel with Solar and Wind Renewable Energy Sources as an Example of the Croatia Study-Case

The ship’s power system is one of the most important systems on board. It is designed for uninterrupted power supply to all ship consumers under different conditions of exploitation. When designing a ship, various optimizations are conducted to build the ship as economically and environmentally friendly as possible. The paper aims to analyze the possibility of applying renewable energy sources (RES), particularly solar and wind energy, on an existing vessel by conducting technical and economic analysis. Data for the solar hour’s number and wind distribution are gathered from the six locations in the Adriatic Sea over 32 years period. Firstly, it was investigated if data were position dependent or independent. Performing a Pearson correlation coefficient and an ANOVA analysis with F-test, it was concluded that the RES analysis is position-independent (p > 0.05, p = 0.826). Secondly, the energy system model created in Simulink was used for the analysis of the electrical network fundamental parameters. Finally, the object of the analysis is the total costs of procurement, installation, and maintenance of the system within a period of 25 years. Consequences are savings in the cost of exploitation and reduction of harmful gas emissions. The use of solar energy would result in savings of 111,556 L of diesel fuel, while the savings from wind energy would be 170,274 L of diesel fuel for 25 years.

Exploring New Computational Strategies for Managing Maintenance Activities of Airport Pavement Systems

AbstractIn this paper, the optimization of the maintenance management problem regarding airport pavements is addressed by developing a series of fast computational procedures whose rationales pursue both practical and economical objectives. Particularly, the study involves the design of five new heuristic algorithms replicating different management strategies that can be undertaken by the airport managers in a certain time horizon for reducing the pavement maintenance costs while considering the impact on the service level of the airport. Each algorithm works on the basis of a preliminary computational framework that has a twofold scope: (i) selecting the pavement portions to be maintained during the provided time horizon. (ii) using a K-means method based on three well-known performance indicators, which, namely, are Residual Life (RL), International Roughness Index (IRI) and Pavement Condition Index (PCI), to group the selected portions into homogenous clusters named work-zones. To evaluate the effectiveness and the efficiency of the proposed optimization algorithms in coping with the maintenance programming problem under investigation, an extended design of experiments based on international airport regulations has been arranged. The obtained numerical results revealed that no single strategy can be selected as the most performing in terms of cost and quality conditions of the pavements. To make robust the numerical results, a sensitivity analysis is conducted to evaluate the influence of the total cost of maintenance on runway length and number of sections. However, the results obtained in this study provide a series of managerial implications, further expanding the research contribution.

Feasibility evaluation of nanofluid based solar collector for biodiesel hot wash: An experimental study

To reduce emissions of carbon monoxide, particulate matter, unburned hydrocarbons and sulfates, biodiesel production has grown rapidly to replace conventional diesel. Sodium methoxide (SMOX) acts as an excellent catalyst for the chemical synthesis of biodiesel, and in recent years, has observed an increase in its global market share. As biodiesel synthesis requires high temperature water for removing unwanted contaminants, this work proposes a new application of aqueous SMOX as a nanofluid in solar collectors for passive heating instead of traditional energy consuming heaters. The results indicate an increase in the heat gain by 50 % at a solar irradiance of 700 W/m2, and the maximum efficiency of the device was found to be around 78 %, which is an increase of 17 % when compared to water as the working fluid. An economic analysis was performed to check the viability of the proposed solar collector in comparison to conventional industrial heaters. It is estimated that aqueous SMOX-based solar collectors are 53 % and 88 % cheaper in terms of total cost and maintenance cost per unit respectively. Apart from biodiesel synthesis, this data can effectively prove the viability of reusing excess and raw SMOX in other sub-processes of a small-scale biodiesel plant.

An optimum budget‐based development in maintenance for electric power transmission networks

On the topic of power systems, the most critical assignment would be providing facilities to make electricity available at the lowest price with a fulfilled level of reliability for all consumers. Today, power transmission reliability has received more concentration due to the increasing essence of providing high-quality energy to customers and operating competitive conditions in electricity markets. In this regard, this paper scrutinizes the reliability-centred maintenance (RCM) issue in terms of considering two optimal maintenance strategies for transmission assets to decrease their forced outage rate (FOR). This techno-economic budget-based maintenance is a probabilistic approach to help asset managers and experts in the decision-making process: to determine between maintenance strategies with associated costs and provide the most economical resource allocation for these elements, which leads to an improvement in the reliability of the whole network. Decreasing the average probability of Energy Not-Supplied (ENS), the simulation determined the proper maintenance strategy for transmission components. After that, the repercussions of the fallen ENS will be analyzed in total maintenance cost (MC), operation cost (OC), and the system's total cost (TC). Also, the IEEE 24-bus reliability test system is considered as a case study demonstrating the proposed technique's practicality.

A Group Maintenance Method of Drone Swarm Considering System Mission Reliability

Based on the characteristics of drone swarm such as low cost, strong integrity, and frequent information exchange, as well as the high cost of timely maintenance of traditional units. This paper proposes a swarm maintenance method based on the reliability assessment of multi-layer complex network missions, which combines the multi-layer complex network system evaluation method with the group maintenance method. On the basis of considering the problem of maintenance grouping cost, the failure mechanism of drones in different modes and the impact of drone maintenance on the system are studied. According to the failure model of single node, the complex network method is used to establish the swarm system’s topology model and evaluate the system mission reliability. The maintenance grouping strategy is optimized by using the multi-objective planning of cost and system mission reliability. Compared with the existing just in time maintenance methods, this method can greatly reduce the total maintenance cost of the swarm system maintenance under the condition of ensuring the high mission robustness of the swarm. In addition, a universal drone swarm mission scenario is used to illustrate the method, and the results verify the feasibility and effectiveness of the method.

Preventive Maintenance Planning 500 Hm on Dump Truck Mercedes Benz Axor 4843k at PT. Mega Jasa Karya Bersama Site PT. Baramulti Sukses Sarana

The problem that is often encountered is the service time that has passed from the time specified by the company, namely 500 HM. With the background of these problems, thoughts arise why there can be delays in service time at PT. Mega jasa Karya Bersama. The research method used is preventive maintenance which in this method prevents damage to the unit in operation by scheduling routine maintenance. In this method, replace components so that the unit's life can be longer, and minimize damage. Where in this study also looks for the average hour meter unit for one year, and also the cost of maintenance. The average result of Hm service for 1 year at PT. Mega Jasa Karya Bersama Site PT. Baramulti Suksessarana is 542 Hm. The total maintenance cost of 500 Hm on Dt MJKB-679 for 1 year in 2021 at PT. Mega Jasa Karya Bersama site PT. Baramulti Suksessarana is Rp. 27.440.000 (twenty seven million four hundred forty thousand rupiah). Estimated waktu service time 500 Hm is 25 days.

A bidding mechanism for maintenance of generation units considering inter-ISO power exchange

To ensure the reliability of power systems, the independent system operator (ISO) manages the planning process of the maintenance of generation units for generation companies (GENCOs). This paper focuses on a widely studied two-layer long-term predictive maintenance decision making framework in a deregulated environment. In the first layer the ISO-wide maintenance schedule is optimized for the GENCOs, targeting minimal total maintenance cost and degradation statuses. In the second layer, a bidding mechanism is designed for GENCOs who are not satisfied with the time slots scheduled by the first layer, so that they can bid for their preferred time slots. A novel bidding mechanism for the host ISO (i.e., the ISO that manages the maintenance planning process) is proposed, called interchangeable bidding mechanism for maintenance (IBMM). In this mechanism, the GENCOs of the host ISO can use their bid price to purchase the supportive energy from the GENCOs of the neighbor ISOs. Furthermore, they also can pay a penalty fee for reducing the amount of energy transmitted from the host ISO to the neighbor ISO with respect to what has been stipulated in the long-term inter-ISO power exchange contract. IBMM provides more opportunities for GENCOs of the host ISO to obtain their preferred maintenance time slots. Additionally, the power system reliability can be ensured. IBMM is formulated as a mixed-integer non-linear bidding programming problem. Then, the bidding programming problem is recast into a mixed-integer second-order cone programming (MISOCP) problem that can be solved using Gurobi. In the case study, the IEEE 118-bus network is studied to illustrate the performance of the proposed bidding strategy.

Optimal maintenance period and maintenance sequence planning under imperfect maintenance

AbstractMaintenance is essential for today's equipment or systems and maintenance costs account for a significant portion of the overall expenditure of devices. Maintenance period optimization and maintenance sequence planning are primary aspects of maintainability. To this end, this paper proposes an approach for maintenance period optimization and maintenance sequence planning, with the consideration of imperfect maintenance. A model of the total maintenance cost per unit time is set up, and the optimal time period for preventive maintenance is calculated. In addition, a new index is created to evaluate the maintenance efficiency of optimal maintenance sequences in different scenarios. The performance of the proposed method is validated by a maintenance sequence optimization and maintenance sequence planning of baggage handling systems. The results indicate that the proposed method is efficient and contributes to maintenance cost savings.

Thermo-economic analysis of integrated gasification combined cycle co-generation system hybridized with concentrated solar power tower

Integrated gasification combined cycle (IGCC) systems have the ability to utilize low-quality coal with reduced emissions and multiple co-generation capabilities (i.e., power, chemicals and fuels). Integration of solar power tower (SPT) with IGCC co-generation can provide an opportunity to use lignite coal with lowest greenhouse gas emissions. In this work, thermodynamic and economic evaluations of solar-IGCC 100% power (power only) hybrids and co-generation (electricity, methane and ammonia) hybrids have been performed using Aspen Plus® V.11 and system advisor model (SAM). Two designs (i.e., large and medium solar) of the SPT have been simulated and optimized for Pakistani weather conditions. Thermodynamic evaluations include, net electrical efficiency, effective energy efficiency and solar-to-electric efficiency of hybrid plants. Economic estimations include, levelized cost of energy, total plant costs, operating and maintenance costs for hybrid plants. Specific CO2 emissions after hybridization are also evaluated. Total annualized revenue at flexible market scenarios and production scenarios have also been evaluated. The net boosted electrical efficiency of 100% power (Hyb-1A) is 38.77%, and the improved efficiency after flue gas integration with SPT for the pre-heating of boiler feed water is 39.10%. The minimum specific CO2 emission achieved from one hybrid combination (Hyb-4A) is 42.1 kg/MWhnet.

Optimisation of Preventive Maintenance Regime Based on Failure Mode System Modelling Considering Reliability

Today, the ability to maintain a continuous complex system operation is viewed as a key attribute for ensuring uninterrupted revenue contribution and the survival of a business. Many industrial organisations have come to understand that by having an effective plan of maintenance, the efficiency and reliability of a system can be improved, while costs can be minimised and revenue-generating production can continue. The novelty of this paper is based on using failure modes and effects analysis (FMEA) to develop a holistic preventive maintenance schedule for a complete system. A system can be modelled as a series and parallel arrangement of subsystems and components, and failure of different components of the system can be determined from their life expectancy. The objective is to ensure continuity of production output while maintaining a high level of system reliability and minimising the total maintenance costs. The reliability of a complete system is analysed using the Weibull failure-time distribution. By using the exhaustive search optimisation method, the maintenance cost is minimised by determining the optimal replacement interval for each FMEA block, subject to system reliability. Based on the results obtained from a case study, it is shown that the approach in this paper can ensure the continuity of production output during maintenance activities, reduce system maintenance costs, and achieve maximum system reliability. This holistic approach can be applied to any form of complex system, and at every step of the process.

Maintenance versus replacement of medical equipment: a cost-minimization analysis among district hospitals in Nepal

BackgroundAbout half of all medical devices in low- and lower-middle-income countries are currently non-operational because equipment maintenance is lacking. Thus, choosing a cost-efficient equipment maintenance approach has the potential to increase both the quantity and quality of important health services. Between 2010 and 2014 Nepal’s Ministry of Health chose two of its development regions to pilot the contracting-out of maintenance services to the private sector. We develop a cost model and employ different data to calculate the cost of this contracted-out scheme. The latter we compare with two additional common approaches to maintenance: in-house maintenance and no maintenance.MethodsWe use invoiced pilot program costs, device depreciation estimates from the literature, and hospital case numbers from Nepal’s Health Management Information System. We estimate net-present values for a three-year horizon, incorporating both fixed and operational cost. Operational costs include downtime cost measured as lost revenues due to non-working equipment.ResultsThe contracted-out maintenance scheme shows a strong relative cost performance. Its cost after 3 years amount to 4,501,574 International Dollars Purchasing Power Parity (I$ PPP), only 90% of the cost with no maintenance. The contracted-out scheme incurs 670,288 I$ PPP and 3,765,360 I$ PPP in fixed cost and operational cost, respectively. The cost for replacing broken devices is 1,920,467 I$ PPP lower with maintenance. In addition, after 3 years total cost of contracted-out maintenance is 489,333 I$ PPP (11%) below total cost of decentralized in-house maintenance. After 10 years, contracted-out maintenance saves 2.5 million I$ PPP (18%) compared to no maintenance.ConclusionsWe find that contracted-out maintenance provides cost-efficient medical equipment maintenance in a lower-middle income context. Our findings contrast with studies from high- and upper-middle-income countries, which reflect contexts with more in-house engineering expertise than in our study area. Since the per hospital fixed cost decrease with scheme size, our results lend support to an expansion of contracted-out maintenance to the remaining three development regions in Nepal.

Routing in offshore wind farms: A multi-period location and maintenance problem with joint use of a service operation vessel and a safe transfer boat

This paper studies an interesting logistical problem related to maintaining a set of selected turbines in offshore wind farms. A service operation vessel (SOV), used to support maintenance activities, also carries a safe transfer boat (STB), which is used to transport technicians, parts, and equipment to the turbines. The maintenance activities are optimised over a planning horizon by simultaneously coordinating the SOV and the STB. A mixed-integer linear programming model is designed, where the objective function is to minimise the total maintenance cost. As the proposed mathematical model is hard to solve with a commercial solver, a decomposition approach is developed. A two-stage stochastic programming model is also designed to tackle uncertain conditions, including the duration of maintenance and the STB’s travel time. The performance of the solution method is evaluated using the Thanet Offshore Wind Farm, in the southeast of the UK. The results of our experiments show that joint use of an SOV and an STB can yield a lower total maintenance cost than only using an SOV or crew travel vessels (CTVs) that are currently the common practice in maintaining offshore turbines.

Maintenance planning estimations and policies optimization for single-unit systems using Hawkes processes

ABSTRACT Maintenance planning and optimizations are very important issues in both theory and practice. In this paper, Hawkes processes, a tool for description of self-excited failure effects, are used to model the failure processes of single-unit systems under the assumption of neglected repair times. For such degraded single-unit systems, some maintenance planning estimations such as the distribution, mean and variance of failures or repairs by time , reliability, mean cost of maintenance, mean and variance of system lifetime are presented under the maximal entropy assumption on repair effects. Meanwhile, two optimization problems are developed by considering the lifetime mean of the single-unit system and total maintenance cost as objective functions and constraints alternatively. We have proved that both optimization problems can reduce to two simplified optimal cases, respectively, and their optimal policies are increasing stepwise sequences of increasing rates of failure rates, which greatly reduce the scope of optimal solutions. The relationships between the estimations and the optimizations are discussed. Furthermore, the detailed optimal maintenance policies for a special case are given as well including an algorithm.

TECHNO-ECONOMIC STUDY OF ELECTRICITY GENERATING POTENTIALS OF FLARED GASES IN KOKORI TOWN OF DELTA STATE, NIGERIA

According to the Department of Petroleum resource (DPR) in its 2018 annual report, 11% of total gas production in Nigeria was flared that year, which translate into about 88.06 BSCF (billions standard cubic feet) of gases that could have been delivered to power plants. This work aims to study the economic benefits of utilizing flared gases for power generation in Nigeria using Kokori Island in Delta State as a case study. Data such as flare volumes and gas turbines fuel consumption were obtained from July to December 2018. The research work was carried out using a five steps methodology which include; Intensive literature review, Site visits, Data collection, Data classification and analysis using payback period. Primary data used were collected through direct measurement of related parameters, The following findings were made; (1)That about 86 % ($5, 002, 391.844) of the total annual operating and maintenance cost goes into purchasing of natural gas for fuelling the turbines to generate electricity, (2) That the average daily gas flaring volume is about 7.2 mmscf/d (Million Standard Cubic Feet per Day) which translates into about 2,625 million mmscf per year, (3) Hitachi H25 gas turbine generator requires about 3.5657 mmscf of natural gas per day to generate 22.9 Mega Watts of electricity which translates into about 1,301 mmscf per year. The following are the recommendations;(1) That the federal government through its Department of Petroleum resource (DPR) should enforce a total ban on gas flaring in Nigeria, (2) That the federal government of Nigeria should decentralize electricity generation and distribution to encourage more investors through a competitive market system, (3) That more indigenous engineers and scientists should undertake researches in electricity generation, transmission and distribution so as to make the commodity available and affordable to Nigerian citizens in the nearest future.

Improving the Operational Output of Marine Vessel MainEngine System through Cost Reduction using Reliability Technique

This research seeks to use reliability technique to improve operational output through cost reduction of the main engine system of a ship. The various subsystems of the marine vessel main engine were identified. The failure mode effect and criticality index of the engine system and their root causes were analyzed. The reliability of the main engine system was analyzed using exponential reliability model and a maintenance task that reduces the operational cost of main engine system was generated thereby improving output. The reliability centred maintenance technique identified all the perspectives of failures in the ship main engine systems and employed the appropriate maintenance approach for each failure respectively. The results of the reliability analysis performed on the main engine systems generated the proposed preventive maintenance (PM) tasks and plan. Decrease in the rate of Run-To-Failure (RTF) data remains inevitable and programmed performance of condition based, task demand and fault finding (CD, TD and FF) was recommended. The projected work program if implemented will decrease labour cost from N177, 600,000.00/year to N100, 800,000.00/year (approximately 43.24% of the total annual labour expenditure). The projected PM scheduling outcomes showed a 44.64% saving in the total cost of maintenance when compared with the existing RTF practice. The main engine systems reliability increases with decreased labour cost. The proposed spare parts plan for the main engine systems was generated and the results showed that approximately 55.42% of the yearly costs of spare parts are saved when projected PM scheduling is adopted.

Technician Collaboration and Routing Optimization in Global Maintenance Scheduling for Multi-Center Service Networks

With the popularization of service-oriented manufacturing, the current operation & maintenance (O&M) has shifted from traditional in-house maintenance to proactive outsourcing maintenance. It is paramount for an original equipment manufacturer (OEM) to provide timely and cost-effective maintenance schemes to geographically distributed customer enterprises. Interestingly, transportation theories could be combined to facilitate multi-location O&M management. In this paper, a transportation-oriented cross-regional opportunistic maintenance (TCOM) policy is developed for solving O&M optimizations and planning real-time schemes for the multi-center service network. The optimization model of this TCOM policy addresses several inter-related decisions: (1) most suitable maintenance times for each leased machine, (2) cost-effective arrangements of technician teams to perform maintenance tasks, and (3) optimal service routes for required teams. We not only integrate maintenance grouping and technician routing, but also investigate the new issues arising from the collaborative sharing of technician teams belonging to different maintenance centers. Numerical examples show that this TCOM policy can achieve significant cost-saving in cross-regional maintenance grouping and multi-location routing optimization for OEMs. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> —This paper is motivated by the critical problem of computing an optimal maintenance policy for the multi-center service network of geographically distributed production systems to achieve a timely and cost-effective O&M management. We consider individual machine degradations, complex maintenance opportunities and network logistics optimization to establish a global maintenance scheme for the multi-center service network. The existing approaches are to schedule the preventive maintenance (PM) for a single machine or multi-unit leased system, which is unilateral and cannot be applied to multi-location production systems. Although the network opportunistic maintenance policy has been proposed in the literature for maintenance grouping and technician routing problem, it still does not consider the limited workforce resource and the collaborative sharing of technician teams from different maintenance centers. To fill this literature gap, in this paper, we develop the TCOM policy to determine the optimal maintenance timetable for leased machines, as well as the cost-effective service route of technician teams belonging to multiple maintenance centers, so as to conduct timely and cost-effective PM on multi-location production systems. Compared with the conventional maintenance policy, our adaptive policy greatly reduces the total outsourcing maintenance cost in long-term O&M services.

Remaining-Useful-Life prognostics for opportunistic grouping of maintenance of landing gear brakes for a fleet of aircraft

Several studies have proposed Remaining-Useful-Life (RUL) prognostics for aircraft components in the last years. However, few studies focus on integrating these RUL prognostics into maintenance planning frameworks. This paper proposes an optimization model for opportunistic maintenance scheduling of aircraft components that integrates RUL prognostics and that groups the maintenance of these components to reduce costs. We illustrate our approach for the maintenance of a fleet of aircraft, each equipped with multiple landing gear brakes. RUL prognostics for the landing gear brakes are obtained using a Bayesian regression model. Based on these RUL prognostics, we group the replacement of brakes using an integer linear program. As a result, we obtain a cost-optimal RUL-driven opportunistic-maintenance schedule for the brakes of a fleet of aircraft. Compared with traditional maintenance strategies, our approach leads to a reduction of up to 20% of the total maintenance costs.

Application of Fminsearch Optimization to Minimize Total Maintenance Cost with the Aim of Reducing Environmental Degradation

This study examined a production system under deterioration and its impact on the degradation of the environment. The environment degrades as the production system reaches a certain level of deterioration. To reduce environmental degradation, the system's deterioration is monitored through scheduled inspections, after which preventive or corrective actions are taken. To achieve the optimum inspection dates that minimize the average total cost per time unit, the Fminsearch algorithm was applied to calculate the optimal inspection dates for two cases of sequential inspection: periodic and aperiodic. To validate the performance of the proposed Fminsearch algorithm, simulation results were compared with the Nelder-Mead method. The comparison results showed the superiority of the Fminsearch algorithm in optimizing inspection maintenance dates to reduce the environmental degradation ratio.

Multi-Objective Model and Variable Neighborhood Search Algorithms for the Joint Maintenance Scheduling and Workforce Routing Problem

This paper addresses a problem faced by maintenance service providers: performing maintenance activities at the right time on geographically distributed machines subjected to random failures. This problem requires determining for each technician the sequence of maintenance operations to perform to minimize the total expected costs while ensuring a high level of machine availability. To date, research in this area has dealt with routing and maintenance schedules separately. This study aims to determine the optimal maintenance and routing plan simultaneously. A new bi-objective mathematical model that integrates both routing and maintenance considerations is proposed for time-based preventive maintenance. The first objective is to minimize the travel cost related to technicians’ routing. The second objective can either minimize the total preventive and corrective maintenance cost or the failure cost. New general variable neighborhood search (GVNS) and variable neighborhood descent (VND) algorithms based on the Pareto dominance concept are proposed and performed over newly generated instances. The efficiency of our approach is demonstrated through several experiments. Compared to the commercial solver and existing multi-objective VND and GVNS, these new algorithms obtain highly competitive results on both mono-objective and bi-objective variants.

Implant-Retained Mandibular Overdentures: Patient-Related Outcome Measurements after Seven Years of Function.

Denture wearers often complain about jeopardized function and reduced quality of life due to lack of prosthesis’ retention. Implant-retained mandibular overdentures, on two non-connected implants (2IOD) are well-proven solutions to overcome these issues. We prospectively assessed 69 patients and scrutinized clinical records until at least seven years of function. Thirty-six were retained on Locator® Abutments (LA) and thirty-tree on Ball Abutments (BA). Both systems were compared regarding the type, amount, and total cost of required maintenance. One implant was lost, yielding 98.7% survival after seven years. In total, 438 technical issues occurred: 121 (27.35%) in BA and 317 (72.4%) in LA. Out of these, 343 events (78%) were solved chairside: 191 (43.6%) were replacements of retention caps, 113 (25.8%) were minor acrylic repairs, 26 (5.9%) pressure ulcers had to be relieved, and 13 (3%) were related to abutments. LA required 179 insert replacements compared to 12 in the BA group. The overall initial treatment cost was EUR 3850 (base year of the analysis: 2003). The average total maintenance cost in relation to the initial cost for the LA and BA groups was 19.11 (range 0–82.24%) and 18.91% (range 0–113.26%) respectively (p = 0.540). Conclusions: The seven-year maintenance costs for a 2IOD is acceptable when the patient is regularly checked and professionally maintained. Most events are easily solvable chairside, but a few patients required more expensive interventions, regardless of the type of attachment used.