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Penentuan interval waktu penggantian berdasar umur dan oportunitas dengan metode total time on test (TTT)

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Master Theses from JBPTITBPP / 2003-01-28 10:41:00
By : Ekawati Martyaningsih, S2-Industrial Management
Created : 2001-09-00, with files

Keyword : replacement interval, opportunity-based, age, numerical
Call Number (DDC) : TT 658. 403 2 M
Document Source : Bidang Khusus Teknik Industri Program Studi Teknik dan Manajemen Industri Program Pascasarjana ITB

Penelitian ini berhubungan dengan penentuan interval waktu penggantian untuk kebijakan penggantian berdasarkan umur dan oportunitas. Kebijakan penggantian yang diteliti dijelaskan berikut ini. Ganti sistem jika mengalami kerusakan/kegagalan pada saat xPada Iskandar dan Sandoh (2000) solusi optimal diperoleh dengan pendekatan analitik diferensial. Pada penelitian ini digunakan pendekatan yang lebih sederhana dibanding metode analitik, yaitu metode Total Time on Test (TTT). Metode ini membutuhkan suatu kondisi dimana persamaan biaya yang dibentuk harus mengandung fungsi distribusi dan scaled TTT-Transform. Variabel keputusannya adalah T dengan ukuran performansi minimasi ekspektasi biaya penggantian per unit. Contoh numerik diberikan untuk kasus kerusakan berdistribusi gamma dan weibull. Hasil perhitungan dengan kedua pendekatan kemudian dibandingkan untuk mengetahui seberapa dekat solusi yang dihasilkan dari metode TTT dengan solusi optimal. Hasil perbandingan menunjukkan adanya perbedaan nilai variabel keputusan, untuk kerusakan berdistribusi Gamma selisihnya antara 0.001 – 0.828 dan untuk kerusakan berdistribusi Weibull selisihnya antara 0.004-1.203.

Description Alternative :

This research deals with determination of replacement interval for opportunity-based age replacementpolicy. If the system fails as time x,x < S for a prespecified value S, a corrective replacement is performed. If x satisfies S < x < T, we take an opportunity tp preventively replace the system by a new one with probabaility p, and do not take the opportunity with probability 1 – p. At the moment x reaches T, a preventive replacement is executed independently og opportunities.

In Iskandar and Sandoh (2000), the optimal solution is obtained by using the analytical approach. In this thesis, we use a simpler approach, i.e. Total Time on Test (TTT) method. This method require a condition in which the long-term average cost should contain distribution function and scaled TTT-transform. The decision variable T is obtained by minimizing the expected replacement cost per unit. Numerical examples are presented to illustrate the theoritical underpinning of the proposed method with two cases, i.e. Gamma and Weibull distribution. The result of numerical examples by two approaches are compared. The difference between the optimal value and the corresponding value obtained using the graphical method has range 0.001 – 0.828 for Gamma distribution and 0.004 – 1.203 for Weibull distribution.

This research deals with determination of replacement interval for opportunity-based age replacementpolicy. If the system fails as time x,x < S for a prespecified value S, a corrective replacement is performed. If x satisfies S < x < T, we take an opportunity tp preventively replace the system by a new one with probabaility p, and do not take the opportunity with probability 1 – p. At the moment x reaches T, a preventive replacement is executed independently og opportunities.

In Iskandar and Sandoh (2000), the optimal solution is obtained by using the analytical approach. In this thesis, we use a simpler approach, i.e. Total Time on Test (TTT) method. This method require a condition in which the long-term average cost should contain distribution function and scaled TTT-transform. The decision variable T is obtained by minimizing the expected replacement cost per unit. Numerical examples are presented to illustrate the theoritical underpinning of the proposed method with two cases, i.e. Gamma and Weibull distribution. The result of numerical examples by two approaches are compared. The difference between the optimal value and the corresponding value obtained using the graphical method has range 0.001 – 0.828 for Gamma distribution and 0.004 – 1.203 for Weibull distribution.


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