Maintenance Intervals Research Articles

Influences of Waste Inclusion on Impact and Crushing Force Resistance of Track Ballast

Recently, the incorporation of various waste materials into the ballast is studied in terms of physical and mechanical behavior. However, the inclusion of concrete debris (CD) and bottom ash (BA) waste, which are enlisted as the inventory materials for railway ballast have not been thoroughly examined. Hence, this paper investigates the improvement in damage resistance of waste incorporated conventional ballast (CB) under impact and crushing force using impact hammer and crushing machine. The initial and final particle size distribution (PSD) were obtained to analyze the damages through the Hardin‘s breakage index and fouling index. The results show that the resistance against crushing and impact force is better when the composition is in the ratio of 1:1 of conventional ballast (CB) and concrete debris (CD). Under crushing load, mixture with 50% of CD recorded breakage index with 4% deviation compared to using 100% of CB. However, integrating with 40% of CD and 10% of BA proved that the values are 2.14% lower than the ACV limit and 9.09% higher than the AIV limit set by British Standard. Although the impact and crushing index of 100% CB aggregates are below the allowable limit, mixing the CD and BA also records results which is only slightly different than the threshold limit. This is due to the cushioning effect caused by the waste acting as the buffering material that reduces the time of impact, which saves the angular materials from wearing off. This will reduce the ballast maintenance intervals that indirectly reduce the service cost and promotes sustainable construction. Based on the results from this study, further experiments are recommended to be carried out to relate and understand which waste material plays a major role in damage reduction or causing higher maitenance cost.

Grease Degradation Alternate Test Method and Storage Interval for Roller Bearings: An Empirical Research

Pandemic caused parts into prolong storage conditions. Empirical experiment was carried out to determine the viscoelastic behaviour and consistency of unworked grease from inside a wheel roller bearing. The grease samples intervals were 9, 10, 11 and 24 months from stored wheel roller bearings. Fresh grease is also tested as a controlled sample. A rheometer amplitude oscillation test was performed. The grease was tested for contaminants such as oxidation, nitration, soot, sulfation, and water using FTIR. Rheology test exhibited changes in viscoelastic behaviour. Grease consistency changed from grade 2 to grade 1. This confirms that the grease tends to soften and degrade over time. FTIR results revealed that there is no significant contaminant for unworked and packed grease in the wheel. Storage and maintenance interval derived from this study.

Optimization of Preventive Maintenance and Replacement Strategies for Nonrenewing Two-Dimensional Warranty Products Experiencing Degradation and External Shocks

“Vehicle damage insurance” in China, “Protection Plus Mobile Elite” launched by Samsung, “iPhone Apple Care +” offered by Apple, and so on are special warranty services aiming at external shocks. These warranty terms, named accident insurance, exist widely in the marketplace. Considering the effect of external shocks on degradation, a two-dimensional preventive maintenance and replacement strategy for products, sold with a nonrenewing and two-dimensional rectangle warranty service, is proposed in this paper. Under this strategy, preventive maintenance actions are scheduled based on units of age or usage, which occurs first. There is a reduction in the intensity function after a preventive maintenance action. Each shock before the Nth shock causes a failure of the product or an increase in product failure rate. The product is replaced by a new one on the Nth shock if it survives the N − 1 shocks. From the view of manufacturers, the mean warranty servicing cost over the whole warranty region is obtained by using the renewal theory. Based on direct numerical Riemann–Stieltjes integration, an approximation algorithm of the cost is also given. The mean cost is minimized by the optimization of preventive maintenance interval and the number of shocks N. A numerical example is given to illustrate the feasibility of the proposed strategy. The effects of maintenance cost, the arrival rate of the shocks, and other model parameters on the optimal strategy are also investigated numerically.

고장확률 기반 계획정비 대기행렬 시뮬레이션: 해군 전투함정을 중심으로

The constant maintenance interval performed by ROK Navy ships has the advantage of convenient maintenance planning. In the past study, the failure rate of the ship continued to change with the life of the ship. Planned maintenance performed at regular intervals may not be appropriate to maintain the varying amount of failure of ships. Probability-based maintenance considers the changing amount of ship failure. Although the effect of probability-based maintenance was derived from previous studies, it was studied based on a single ship. Therefore, in this study, the effect of applying probability-based maintenance to multiple ships was confirmed as in reality. When maintenance was performed according to probability, the maintenance time overlapped and queuing occurred. The system dynamics simulation was performed considering the advantages of applying probability-based maintenance and the disadvantages due to queuing at the same time.

Optimisation of Maintenance Policies Based on Right-Censored Failure Data Using a Semi-Markovian Approach.

This paper exposes the existing problems for optimal industrial preventive maintenance intervals when decisions are made with right-censored data obtained from a network of sensors or other sources. A methodology based on the use of the z transform and a semi-Markovian approach is presented to solve these problems and obtain a much more consistent mathematical solution. This methodology is applied to a real case study of the maintenance of large marine engines of vessels dedicated to coastal surveillance in Spain to illustrate its usefulness. It is shown that the use of right-censored failure data significantly decreases the value of the optimal preventive interval calculated by the model. In addition, that optimal preventive interval increases as we consider older failure data. In sum, applying the proposed methodology, the maintenance manager can modify the preventive maintenance interval, obtaining a noticeable economic improvement. The results obtained are relevant, regardless of the number of data considered, provided that data are available with a duration of at least 75% of the value of the preventive interval.

Estimation of residual stress distribution in railway axles

The manufacturing process of railway axles usually includes axle surface treatment to induce compressive residual stress on the axle surface to increase impact resistance and fatigue lifetime. A proper determination of residual stress enables to obtain correct input data for other procedures, e.g., optimization of specialized treatment or lifetime estimation, which sets safe, but not unnecessary frequent, maintenance intervals of the axles. The most common methods for residual stress determination used by R&D centers of axle manufacturers are the hole drilling method and X-ray diffraction. However, we can use these methods for the determination of surface or close-to-surface residual stress only. In the case of large components like railway axles, it is essential to have information about the residual stress in the whole cross-section, not only from the axle surface, especially if the residual stress is developed by induction hardening, which can influence the residual stress distribution in a considerable depth.The work presented in this paper aims to develop a reliable methodology for determining residual stress in the whole cross-section of a railway axle with reasonable equipment prices or commonly used equipment. Two presented methods follow the defined methodology. They combine well-known destructive methods (layer removal and sectioning methods) with X-ray diffraction and numerical simulations to evaluate correct residual stress distribution. Both ways are applied to the case of an induction-hardened railway axle from the EA4T steel. Results of both methods are then compared to results obtained by neutron diffraction technique and other experimental methods to validate the plausibility of the proposed scenarios.

Flow-induced pulsations in Francis turbines during startup - A consequence of an intermittent energy system

Hydraulic turbines are increasingly responsible for regulating the electric grid, due to the rapid growth of the intermittent renewable energy resources. This involves a large increase in the number of starts and stops, which cause severe flow-induced pulsations and fluctuating forces that deteriorate the machines. Better knowledge of the evolution of the flow in the machines during transients makes it possible to avoid hazardous conditions, plan maintenance intervals, and estimate the costs of this new kind of operation. The present work provides an in-depth and comprehensive numerical study on the flow-induced pulsations and evolution of the flow field in a high-head model Francis turbine during a startup sequence. The flow simulation is carried out using the OpenFOAM open-source CFD code. A thorough frequency analysis is conducted on the fluctuating part of different pressure probes and force components, utilizing Short-Time Fourier Transform (STFT) to extract the evolution of the frequency and amplitude of pulsations. Low-frequency oscillations are detected during the startup, which are induced by the complex flow structure in the draft tube. A decomposition is performed on the draft tube pressure signals, and the variations of the synchronous (plunging) and asynchronous (rotating) modes are studied. The plunging mode is stronger at minimum and deep part load conditions, whereas the rotating mode is dominant during the presence of the Rotating Vortex Rope (RVR) at part load. The velocity field in the draft tube is validated against experimental data, and the complex flow structures formed during the startup procedure are explained using the λ2 vortex identification method.

Recommendations for Refined Preventive Maintenance Management of Concrete Bridges in China Based on Environmental Risk Zoning

Service environment has an important influence on the durability of concrete bridges. Environmental factors are often considered in the design stage, however, they tend to be ignored in the process of maintenance management. It is of great significance in prolonging the service life of a bridge to pay attention to the influence of the environment on the deterioration of the bridge during the preventive maintenance process. Concrete carbonation, chloride ion corrosion, sulfate corrosion, concrete cracking, concrete abrasion, and freeze–thaw damage are the main causes of decline of bridge durability. Based on these six kinds of distress, indexes of environmental zoning are proposed. For this purpose, variable weight theory is introduced into the matter-element extension model, and the comprehensive environmental risk values of various regions are calculated. The environmental risk zoning map of the concrete bridge’s location is then drawn using data visualization software (Tubiaoxiu). These maps show that the east, south, and southwest of China are the most high-risk areas for the deterioration of concrete bridges, and the validity of the results is proved by the distribution of collected bridge collapse accidents. Through the environmental risk zoning map, managers can intuitively grasp the degree of environmental risk in each region in real time. This approach could help bridge management department to implement differential management of concrete bridges in different regions, adjust bridge maintenance intervals dynamically, predict the state of bridges scientifically, and realize refined preventive maintenance management.

Using In-Vehicle Monitoring Data to Assess Road Conditions of Traffic Flows

Developments in adaptive systems for maintenance and repair of automotive vehicles set the task of monitoring the conditions of their operation. One of the main factors determining these conditions is the type of road surface.The article describes the results of identification of the type (and condition) of the road surface obtained by theoretical and experimental methods based on the analysis of vertical accelerations recorded on the vehicle body.The purpose of research was to provide a possibility of continuous monitoring of the type of road surface on which a vehicle is driving, with the subsequent application of the obtained data to correct maintenance intervals. The results of experiments have shown the dependence of the vertical acceleration of the body on the micro-profile of the road surface. The described experimentally obtained profiles of vertical accelerations refer to different types of road surface in different conditions. For quantitative assessment, it is proposed to calculate the average level of accelerations as an integral average over a certain time interval.The results of the experiments have allowed to substantiate the empirical dependence of the average level of accelerations on speed of a vehicle. Based on this dependence, a method is proposed for recalculating the current values of the average levels of accelerations obtained at different speeds into values adjusted to the base speed to ensure the possibility of their comparison.It is shown that based on the values of average acceleration levels obtained through operation monitoring regarding a previously known type of road surface, it is possible to determine its condition. A short algorithm is formulated for practical implementation and assessment of road conditions of traffic flows. As for hardware, it is proposed not to equip a vehicle with additional sensors but to use operational standard accelerometers as part of in-vehicle emergency call systems, e.g., ERA-GLONASS equipment units.

Impact of dust loads in long railway tunnels: In-situ measurements and consequences for tunnel facilities and operation

Reliable information concerning rail tunnel dust emissions dependent on parameters such as train type, train speed, operating conditions, etc. is quite rare. Thus, in order to quantify the effect of heavy metals on the environment, specific data is needed when designing air filtration systems inside the tunnel, or in carrying out environmental assessment studies. Detailed investigations were therefore carried out in a test installation in an Austrian rail tunnel. In order to be able to use these data for the long railway tunnels currently under construction, train-specific emission factors were determined. It was found that emissions from freight trains are up to 6.68 times higher than those from passenger trains. Bulk freight transport in open cars produces the highest emissions, while the short regional passenger trains exhibit the lowest emission levels. Chemical analysis of the samples came up with a mass fraction of 60% related to metals, of which, iron is the dominating component. Based on these findings, maintenance intervals for high quality dust filters were derived.In addition, the knowledge gained on train type-dependent emission factors greatly helps to improve upon the very poor data now used in environmental studies, particularly when determining railway particulate matter emissions.

Reliability Importance Measures considering Performance and Costs of Mechanical Hydraulic System for Hydraulic Excavators

Although some reliability importance measures and maintenance policies for mechanical products exist in literature, they are rarely investigated with reference to weakest component identification in the design stage and preventive maintenance interval during the life cycle. This paper is mainly study reliability importance measures considering performance and costs (RIMPC) of maintenance and downtime of the mechanical hydraulic system (MHS) for hydraulic excavators (HE) with energy regeneration and recovery system (ERRS) and suggests the scheduled maintenance interval for key components and the system itself based on the reliability R i t . In the research, the required failure data for reliability analysis is collected from maintenance crews and users over three years of a certain type of hydraulic excavators. Minitab is used for probable distribution estimation of the mechanical hydraulic system failure times, and the model is verified to obey Weibull distribution. RIMPC is calculated by multiplying the reliability R i t and weighting factor W i and then compared with other classical importance measures. The purpose of this paper is to identify the weakest component for MHS in the design stage and to make appropriate maintenance strategies which help to maintain a high reliability level for MHS. The proposed method also provides the scientific maintenance suggestion for improving the MHS reliability of the HE reasonably, which is efficient, profitable, and organized.

PENENTUAN INTERVAL WAKTU PERAWATAN MESIN INJECTION MOULDING MENGGUNAKAN METODE RCM DI PT “X”

In the industrialized world, product is the main of a production process that forms a production process system. In order to a system of production process running continuesly, need a maintenance of the equipment and production machines. The machine maintenance is needed to minimize the damage of machine then the machine can be used for a long time. The purpose of the study is to calculate the reliability value in which the interval time of maintenance will be determined so that it can support the reliability of the tool. Method of the study uses the RCM (Reliability Centered Maintenance) to solve machine maintenance problems that often occur at PT “X”. RCM method has the advantage of defining a machine focused maintenance program and avoids unnecessary maintenance activities by specifying appropriate maintenance intervals. This study also presents qualitative data in the form of FMEA analysis (Failure Mode Effect Analysis) and quantitative data in the form of determining reliability values and determining maintenance time intervals which provide a solution for PT. “X”.The result of the study, reliability value of the MJM-JLB-HQ Injection Moulding Machine is 0.9183 at 12 hours, VICTOR Injection Moulding is 0.9243 at 4 hours, and the reliability value of MJM-JLB 198-HQ Mould is 0.5125 at 96 hours, VICTOR's Mould is 0.5063 at 72 hours. For the results of maintenance interval to keep the value of reliability not going down below 0.9 is 12 hours for MJM-JLB198-HQ Injection Molding Machines, then 4 hours for VICTOR Injection Moulding Machines. The result maintenance interval analysis of mould with reliability not going down below the value of 0.5 is 96 hours on MJM-JLB198-HQ Injection Moulding Machine, and 72 hours at VICTOR Injection Moulding Machine.

Guided waves for structural health monitoring in composites: A review and implementation strategies

Structural Health Monitoring (SHM) systems provide a useful tool to diagnose any engineered structural system and eventual critical damage that may occur at any moment during the operational life. In the past two decades progress has been made in all the fields of SHM, from sensor technology to system integrated techniques. The common goal of any SHM system, whatever the specific application is, may be synthesized in three main points: identify structural deterioration stage, recognize its severity and evaluate the necessity to make a more detailed inspection or proceed to maintenance on condition, based on a potential hazard that may lead to a catastrophic failure. The implementation of such a system leads to making normal operations with the same safety levels but with more efficient maintenance procedures. In addition, it allows avoiding the oversizing of structural components extending the inspection and maintenance intervals. Both these results help to reduce the life-cycle cost of the specific engineered system as it is possible to perform maintenance when it is necessary, i.e. on-condition.The current state of the art about the guided waves (GW) based structural health monitoring of aerospace composite structures is reviewed in this paper, looking at the implementation of the methodologies proposed and assessed by the authors and giving an outlook on what has been done by the scientific community.

Optimization maintenance performance level through collaboration of overall equipment effectiveness and machine reliability

Maintenance performance level (MPL) is an important part of the key performance indicator (KPI) to improve the effectiveness of machine maintenance which includes factors of overall equipment effectiveness-machine effectiveness (OEE-ME) and machine reliability (MR). The purpose of this paper is to optimize the value of the maintenance performance level (MPL) through the collaboration of overall equipment effectiveness-machine effectiveness (OEE-ME) and machine reliability (MR). The study began with collecting research data, namely machine operation, preventive maintenance, and corrective maintenance. The data is processed using the Pareto principle to determine the critical system based on failure frequency. The selected critical system is tested for probability distribution and machine reliability (MR) assessment with several predetermined maintenance time interval scenarios. The main result of this research is the optimal maintenance time interval is a better criterion than other criteria. The optimal maintenance time interval was chosen because it can meet the requirements of overall equipment effectiveness-machine effectiveness (OEE-ME) at a world-class maintenance performance level (MPL) with a value of 90.43%, and the proposed machine reliability (MR) is better than the initial machine reliability (MR) based on the failure ratio value. Therefore, it can be boldly stated that the collaboration of overall equipment effectiveness-machine effectiveness (OEE-ME) and machine reliability (MR) can influence and optimize the value of maintenance performance level (MPL), which has a strong correlation and significant impact.

Обоснование потенциала увеличения интервала замены моторного масла двигателя КАМАЗ Р-6

Abstract. The article is devoted to solving the actual scientific and practical problem of substantiating at the design stage the potential for increasing the frequency of maintenance of an automobile diesel engine, which is distinguished by an improved design, improved indicators of reliability, efficiency, environmental friendliness and quality of the operating materials used. The general goal of scientific research is to reduce operating costs and increase the efficiency of using cars with high-tech engines by increasing the frequency of their maintenance. The solution of the problem within the framework of this article is to establish the factors that affect the potential for increasing the engine oil change interval, taking into account modern and future requirements for automotive diesel engines. The methodological apparatus for solving this problem consisted in an analytical study of many years of experience in designing, manufacturing, testing and operating engines of the KAMAZ V8 family, as well as engines from leading world manufacturers. It has been established that for modern high-tech automotive diesel engines, the potential for increasing the engine oil change interval is a combination of a set of factors, namely: the use of diesel fuel with a minimum sulfur content; reduction of heat stress of lubricated parts. The main results are that specific basic requirements have been formulated for engine oil, diesel fuel, design and manufacturing technologies for parts, assemblies, diesel engine systems to increase the frequency of maintenance and oil change intervals for engines of the new KAMAZ R6 family. The scientific novelty lies in the fact that a complex of factors has been identified, the combination of which affects the reduction in the rate of deterioration of the quality indicators of engine oil, taking into account which allows increasing the intervals for its replacement during the operation of a diesel engine. The theoretical value for the development of the branch of science “Operation of road transport” lies in the fact that the identified factors and relationships contribute to the study and improvement of the processes of organizing car maintenance, which helps to increase their operational reliability and operational efficiency. The direction of further research is the solution of the following complex task — bench and operational tests of the engine of the new KAMAZ R6 family to confirm the validity of the potential for increasing the frequency of maintenance.

Population growth of the golden mussel (L. fortunei) in hydroelectric power plants: a study via mathematical and computational modeling

ABSTRACT Golden mussel is an invasive species in Brazil which impacts local environments, dislocating native species and altering microecological conditions as well as affecting hydroelectric power plants and water treatment systems. The objective of this research is to establish a method that is both effective and efficient to quantify the population of the Golden mussel in hydroelectric power plant reservoirs, with a focus on population control measures. A two-dimensional mathematical model was developed combining hydrodynamics and populational dynamics to simulate the distribution of mussels in a reservoir. The results showed that dam’s region was progressively infested, and after 18 months of simulation it has reached around 80% of its carrying capacity. The method proved to be satisfactory and the generated map of cluster locations for the golden mussel corresponds to field observations. Furthermore, the result of the algae density simulation matched chlorophyll-a density map obtained from satellite images. The methodology can be further applied to new areas and could be expanded to predict population variations in order to guide environmental measures for preservation and recovery of impacted reservoirs, presenting another tool for hydroelectric operators who can use information together with field inspections to plan maintenance intervals before infestation damages equipment.

Research and application of reliability-based cost optimization method for constant interval preventive maintenance

Preventive maintenance is a means to ensure the component is kept in the desired state. Lack of preventive maintenance will cause unexpected consequences for the component, and too much preventive maintenance will result in unnecessary investment of resources. Based on the reliability data of the component, this paper establishes an analysis model to determine the optimal preventive maintenance interval of the component to make the cost of preventive and corrective maintenance lowest.

Application of fuzzy mathematics for choosing maintenance intervals for non-public railway tracks

This article discusses the application of fuzzy mathematics for choosing time windows for the maintenance of non-public railway tracks. The design features of several stations and the points of junction of non-public railway tracks lead to hostile routes in the leads of the station. Moving the switching fleet through the neck creates hostility to the train route. To determine the optimal maintenance interval of non-public railway tracks, aimed at excluding hostility, it is necessary to know the throughput reserve of the railroad neck element in a certain time window. To localize the throughput reserve, it is proposed to divide the day into 30-minute intervals. This division will allow determining more accurately both the throughput reserve of the railroad neck element and the periods for servicing non-public railway tracks. The most appropriate way to calculate the throughput reserve is to use fuzzy numbers since this method allows taking into account the unequal capabilities of values within the intervals. Using the defuzzification procedure, a natural number is assigned to a given fuzzy number. After carrying out the defuzzification of the throughput reserve, the obtained values can be used to build an algorithm for selecting service intervals for non-public railway tracks.

Role of Lithium-Ion Batteries in Increasing the Operational Safety of Offshore Service Vessels

Abstract For ensuring the operational safety of offshore service vessels (OSVs) during critical operations, marine classification agencies recommend operating redundant diesel generators (DGs) as a spinning reserve for dynamic positioning (DP) systems. In view of the reduced fuel efficiency and increased emissions of DG sets when operated at low loads, lithium-ion (Li-ion) batteries are preferred as a green choice to serve the class-recommended DP power backup for 12 min. Based on the on-demand reliability analysis and Li-ion battery failure models, it is identified that an OSV with a 1.6-MW‐capacity DP system requires 538 kWh of Li-ion battery power to reliably replace a spinning DG set in serving power backup for 12 min. Based on the IEC61508/11 health, safety, and environment framework, the methodology to identify the OSV risk under various operational conditions and the battery system minimum maintenance interval requirements to meet various safety integrity levels are described.

The Development of A Reliability Evaluation Application for Power Plant Steam Turbine Vibrations to Predict Its Failure

A steam turbine is the most critical component in a thermal power plant. Due to its crucial function, it should be maintained to be able to operate without failure. This paper aims to develop an application that can be used to analyze the reliability and synchronization of vibrations in a single evaluation through the application. The application is helpful to decide the proper time the maintenance should be performed in order to provide a better maintenance strategy. In this paper, the application was used to make an ease in evaluating the reliability and vibration of a 670 MW power plant steam turbine. The reliability was analyzed by qualitative and quantitative methods. The vibration evaluation using Fast Fourier Transform (FFT) was done by diagnosing the failure symptoms from vibration spectrum. The analysis of synchronization of vibrations conducted by comparing the vibration frequency and the natural frequency of the system which can be calculated easily using the application. The algorithm program of both evaluations was built using GNU Octave software to make a friendly user interface. From the evaluation result, the most critical components of the steam turbine are coupling, labyrinth seals, bearing, diaphragm, turbine control valve, and turbine stop valve. The maintenance interval based on the expected reliability of 90% produces the highest reliability improvement. Based on the vibration analysis, there is no failure symptoms detected in the turbine bearings. Furthermore, the dominant frequencies of vibration are distant from the natural frequency. Therefore, the steam turbine condition is acceptable to operate.