Hasil Pencarian  ::  Simpan CSV :: Kembali

Abstrak :
ABSTRACT
This article an infinite-capacity two-server queue system, where the servers are subject to failure at any time. A repairman is responsible for repair the failure server and the repair rate is changeable depending on the number of failure servers. The repair rate of only one server is failure and that of two servers are all failure may be different. The steady-state reliability indexes and the stability condition of queue are derived through the transfer rate matrix. The expected queue length and some related steady-state performances are obtained by the probability-generating function transform method. Numerical examples are provided for illustration purposes.

Abstrak :
The aim of this paper is to propose a general model to illustrate the joint effect of corrective and preventive maintenance on repairable systems. The intensity of the failure process without maintenance is characterized in bathtub form. The maintenance effect is expressed by the change induced on the failure intensity before and after maintenance. It takes into account the possibility of dependent maintenance times with different effects. The likelihood functions are derived, so parameter estimations and assessment of the maintenance efficiency are possible. The properties of the parameters estimators have to be theoretically studied. Finally, results are applied to a real maintenance data set.

Abstrak :
Sistem repairable pada pengoperasian engine umumnya merupakan system kompleks dengan interval antara kegagalan tidak mengikuti distribusi yang sama. Kondisi engine sebagai sistem repairable mengalami keausan sejalan dengan waktu yang berdampak pada penurunan performance dan peningkatan cost. Hal ini merupakan permasalahan kritis khususnya dalam penentuan waktu overhaul engine di PAMA dalam pengoperasian armada dumptruck. Mengingat penentuan waktu overhaul engine sulit karena saat ini belum tersedia panduan dari perusahaan untuk menentukan kapan suatu engine harus di-overhaul secara ekonomis, maka perlu dirancang suatu model yang dapat menentukan waktu optimum overhaul dari engine dumptruck. Dalam rancangan ini model NHPP digunakan sebagai metode pendugaan awal intensitas failure yang menggambarkan penurunan performance engine. Jika model ini tidak memenuhi kesesuaian, maka digunakan model GRP. Hasil model terpilih dipadukan dengan biaya maintenance dan overhaul digunakan untuk menentukan waktu optimum overhaul engine. Dari analisis terhadap hasil model, dapat disimpulkan bahwa: 1) model GRP adalah model terbaik untuk repairable system dibanding model NHPP berdasarkan nilai LKV yang paling positif; 2) hasil nilai ? rata-rata > 1 yaitu 1.6510253, maka secara umum sistem sedang mengalami fase penurunan; 3) ratarata nilai To adalah 31,277 hourmeter, sedangkan 7 dumptruck lainnya nilai To belum dapat dihitung karena baru memiliki nilai ? < 1.

---

Repairable system in engine operations is a complex system that has interval between failure where the failure does not follow equal distribution. Engine's condition as a repairable system has worn-out by time which the impact is on reducing the performance and increasing the cost. The impact is a critical problem especially in the operating of dump truck fleet. It is difficult to estimate the time of engine overhaul because there is no guidance from the company to determine when the engine needs to be overhauled economically. Therefore, it is highly needed to design a model that is able to determine optimum overhaul time of engine dump truck. In this design, NHPP model is used as initial estimate failure intensity method that can describe reducing of engine performance. If this model is not approriate then the GRP model is used. Result of choosing model combined with average maintenance and overhaul cost are used to determine optimum overhaul engine. The following are the research results: 1) GRP model is the best model for repairable systems than NHPP model based on LKV value that is more positive; 2) results of mean value ? > 1 is 1.6510253 therefore the system is on deterioration phase; 3) mean value of To is 31,277 hourmeter meanwhile the value of 7 other dumptrucks can't be determined yet because value ? < 1.