Reliability Analysis for Unrepairable Automotive Components

The analysis of the reliability parameters of a technical object and the determination of the change in the reliability of the object over time, requires the knowledge of the functional characteristics and reliability parameters of the elements included in a system. On the basis of the failure data of the selected element of the object, in this case the vehicle, it is possible to determine the average working time to failure of the element and the appropriate form of distribution that characterizes the reliability and durability parameters of the tested element. The main purpose of the research presented in the article was to develop a method of assessing the reliability of an electronic component of a vehicle-a boot lid contactor. This paper also presents three possible methods of repairing the boot lid contactor (sealing the housing with adhesive with better way, replacing the element with a new one or the most time-consuming solution, changing the shape of the boot lid). The authors also decided to determine the reliability and cost parameters that will allow preventive replacement of this element. The tests were carried out on a fleet of 61 vehicles of the same model, but with different body structures. Contactor failures were reported in 41 cases, of which 29 were in the hatchback construction and 12 in the estate type. The analysis of the distribution selection for the tested part of the passenger car-the boot lid contactor-was performed using the Likelihood Value (LKV) test to determine the rank of distributions. Also the maximum likelihood (MLE) method was used to estimate the distribution parameters. The three-parameter Weibull distribution was the best-fitted distribution in both cases. It was clearly defined that one model of car with two different types of body have vastly different reliability characteristic. Based on the reliability characteristic and parameters, the appropriate preventive actions can be taken, minimizing the risk of damage, thus avoiding financial losses and guaranteeing an appropriate level of vehicle safety.

Semi-Markov Model of the System of Repairs and Preventive Replacements by Age of City Buses

The paper presents a mathematical model of the system of repairs and preventive replacements by age of city buses. The mathematical model was developed using the theory of semi-Markov processes. In the model developed, four types of city bus renewal processes are considered and three types of corrective repairs and preventive replacement. Corrective repairs are considered in two types: minimal repairs (repairs carried out by the Technical Service units) and perfect repairs (repairs carried out at the stations of the Service Station). The models of restoration systems that use semi-Markov processes in which minimal repairs, perfect repairs, and preventive replacements by age, have been examined in the literature to a limited extent. The system under consideration is analysed from the point of view of two criteria: profit per time unit and availability of city buses to carry out the assigned transport tasks. Conditions of criterion functions’ extremum (maximum) existence were formulated for the adopted assumptions. The considerations presented in the paper are illustrated by exemplary results of calculations.

ANALISIS PREVENTIVE MAINTENANCE MESIN AM KORIN DENGAN AGE REPLACEMENT DI PT NUGRAHA INDAH CITARASA INDONESIA

The smooth production process of PT Nugraha Indah Citarasa Indonesia is often disrupted because AM Korin machines that act for filling processes often experience damage and cause the need to repair components that are very detrimental to the company because of the time lost for production due to breakdown of these engine components, causing production loss. Preventive maintenance schedule is needed to prevent damage in the future to find out the maintenance time intervals for AM Korin engine components so as to eliminate downtime based on selection with the most minimal cost savings. Age Replacement is a preventive replacement based on the age of the component by following a certain distribution pattern. So preventive replacement is carried out by re-establishing the time interval for the next preventive replacement in accordance with a predetermined interval in the event of a replacement due to the damage that occurred. The Age Replacement method serves to accurately predict AM Korin engine component replacement activities that often suffer damage by analyzing based on historical data of damage to these components as well as knowing the optimal cost emphasis for each time interval of component replacement.The results of the study showed that one of the optimal replacement intervals was 23 days for sensor components with a replacement cost of Rp. 77. 625,000 which reduces the cost of previous treatments, which is Rp. 99,900,000. Keywords: Age Replacement; Preventive Maintenance; BreakdownAbstrakKelancaran proses produksi PT Nugraha Indah Citarasa Indonesia sering mengalami gangguan karena mesin AM Korin yang bertindak untuk proses filling sering mengalami kerusakan dan menimbulkan keperluan untuk perbaikan komponen yang sangat merugikan bagi perusahaan karena waktu yang hilang untuk produksi akibat breakdown komponen mesin tersebut sehingga menyebabkan production loss. Jadwal preventive maintenance sangat dibutuhkan untuk mencegah kerusakan di masa yang akan datang untuk mengetahui interval waktu perawatan bagi komponen mesin AM Korin sehingga dapat mengeliminasi downtime berdasarkan pemilihan dengan penghematan biaya yang paling minimal. Age Replacement merupakan penggantian pencegahan berdasarkan umur dari komponen dengan mengikuti pola distribusi tertentu. Jadi penggantian pencegahan dilakukan dengan menetapkan kembali interval waktu penggantian pencegahan berikutnya sesuai dengan interval yang telah ditentukan jika terjadi penggantian akibat kerusakan yang terjadi. Metode Age Replacement berfungsi untuk memprediksikan secara akurat kegiatan penggantian komponen mesin AM Korin yang seringkali mengalami kerusakan dengan menganalisa berdasarkan data historis kerusakan komponen tersebut serta mengetahui penekanan biaya optimal untuk setiap interval waktu penggantian komponen. Hasil dari penelitian menunjukkan bahwa salah satu selang waktu penggantian optimal yaitu selama 23 hari untuk komponen sensor dengan biaya penggantian Rp. 77. 625.000 dimana menekan biaya perawatan sebelumnya yaitu sebesar Rp. 99.900.000.

Optimal Maintenance Probabilities and Preventive Replacement Maintenance Policy for Photocopy Machines

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.

Reliability modelling and maintenance policy optimization for a repairable parallel system

This paper proposes an integrated approach for reliability modelling and maintenance scheduling of repairable parallel systems subject to hidden failures. The system consists of heterogeneous redundant subsystems whose failures are revealed only by inspections. Inspections at periodic times reveal the components state and repair actions are decided by the excursion of a basic state process describing the total number of failed components in each subsystem. Using the standard renewal arguments, the paper aims at minimizing the average cost rate by the joint determination of the optimal inspection interval, the partial repair threshold and the preventive replacement threshold. We illustrate the procedure for the case as the components' lifetimes conform to the Weibull distribution. Numerical examples are used to illustrate the proposed model and the response of the optimal solutions to the model's parameters.

Reliability modelling and maintenance policy optimization for a repairable parallel system

This paper proposes an integrated approach for reliability modelling and maintenance scheduling of repairable parallel systems subject to hidden failures. The system consists of heterogeneous redundant subsystems whose failures are revealed only by inspections. Inspections at periodic times reveal the components state and repair actions are decided by the excursion of a basic state process describing the total number of failed components in each subsystem. Using the standard renewal arguments, the paper aims at minimizing the average cost rate by the joint determination of the optimal inspection interval, the partial repair threshold and the preventive replacement threshold. We illustrate the procedure for the case as the components' lifetimes conform to the Weibull distribution. Numerical examples are used to illustrate the proposed model and the response of the optimal solutions to the model's parameters.