Manajemen Operasi. Pemeliharaan.

Transkripsi

1 Manajemen Operasi Pemeliharaan

2 Definisi MAINTENANCE: semua aktivitas yang berkaitan dengan menjaga sistem dan peralatan agar selalu dalam keadaan siap pakai. RELIABILITY: Probabilitas suatu bagian/suku cadang dari mesin/produk dapat berjalan dengan baik untuk jangka waktu tertentu dalam kondisi yang ditentukan.

3 Tujuan Menjaga kemampuan sistem dalam keadaan siap pakai dan mengendalikan pembiayaannya.

4 Mengapa Pemeliharaan Penting.. Karena berpengaruh langsung pada: 1. Kapasitas produksi 2. Biaya produksi 3. Kualitas produk dan jasa 4. Keselamatan pelanggan dan tenaga kerja 5. Kepuasan pelanggan

5 Posisi Maintenance dlm Perusahaan.. Di bawah Dept. Operasi atau, Langsung di bawah Direksi. Level manajer maintenance ditentukan oleh The importance of maintenance for the organization. Departemen maintenance biasanya dibagi 2: Bangunan (& Pekarangan) Peralatan

6 4 Taktik Reliability Tactics 1. Improving individual components 2. Providing redundancy Maintenance Tactics 1. PREVENTIVE MAINTENANCE Implementing or improving preventive maintenance 2. BREAKDOWN MAINTENANCE Increasing repair capabilities or speed

7 Umur Mesin Umur Ekonomis Eksternal Internal Umur Teknis *Maintenance membuat umur ekonomis mendekati umur teknis.

8 Preventive Maintenance Keeping machinery and equipment running. Designing technical and human system that will keep the productive process working within tolerance.

9 A. Langkah Pencegahan Feel Inspection Tighten Clean Adjust Lubrication - Rasakan - Periksa - Kencangkan - Bersihkan - Setel - Lumasi

10 B. Overhaul (Bongkar) C. Repair (Perbaiki) D. Maintenance Scheduling.

11 Breakdown Maintenance Perbaikan. Dilakukan setelah mesin rusak.

12 Jenis Maintenance Menurut Biaya Most necessary maintenance Trouble Free Maintenance

13 Faktor Penentu Kualitatif Jenis Maintenance Vital atau tidaknya alat tsb Daya tahan alat tsb Struktur kelengkapan pabrik (layout) Line layout Trouble free Process layout Tdk harus trouble free

14 Repair, Replacement & Overhaul Keputusan2 untuk membongkar dan mengganti. Dapat dikaitkan dengan biaya modal dan operasional (termasuk biaya mantenance) dari peralatan. Biaya operasional naik untuk sementara. Adanya kenaikan biaya sedikit demi sedikit, hingga akhirnya sampai pada penggantian yg dapat dibenarkan. Adanya beda biaya modal dan biaya reparasi mesin baru dengan mesin lama dapat mempengaruhi keputusan dilakukannya penggantian, karena rancangan mesin baru punya kemajuan yg disebabkan adanya mekansime/otomatisasi yang bisa meringankan biaya tenga kerja dan biaya2 maintenance. Biaya Operasional Repair Overhaul Replacement

15 Best Practice Walt Disney Company intolerant of failure or breakdown United Parcel Service Dedicated drivers who operate the same truck every day Dedicated mechanics who maintain the same group of vehicle.

16 Improving Individual Components System reliability (Rs) is a product of individual reliability. R s = R 1 * R 2 * R 3 *... Ex: Rs = 0.90 x 0.80 x 0.99 = or 71.3%

17 Evaluating Maintenance Reliability Probability that an item will function for a given time Mean time between failures (MTBF) Average time between failures of a repairable item Failure rate Reciprocal of MTBF

18 Formula Number of failures Failure Rate(%) = FR(%) = * 100% Number of units tested Failure Per Operating Hour(n) = FR(N) = Number of failures Operating time Mean Time Between Failure = MTBF = 1 FR(N)

19 Example Twenty air-conditioning systems designed for use by astronauts in NASA space shuttles were operated for 1,000 hours at NASA s Huntsville, Alabama test facility. Two of the systems failed during the test one after 200 hours and the other after 600 hours. Compute a. The percentage of failures, b. Number of failures per operating hour and c. MTBF

20 Answer a) FR (%) = 10% b) FR (N) = failure/unit-hr c) MTBF = 9,434 hour

21 Providing Redundancy Back Up Redudancy is provided to ensure that if one component fails, the system has recourse to another.

22 Perfect Computer System No bug, no crash Extraordinarily reliable Fighter jets Space shuttle Nuclear power plants

23 Providing Redundancy Probability of first component working + Probability of second component working Probability of * needing second = P(R) component Ex: reliability of a component is 0.80 and we back it up with another component with reliability Reliabilty result = [0.80 x (1-0.80)] = 0.96

24 F-14 Tomcat F-14 Only 10% of the F-14 s software is used to fly the plane 40% used to automatic testing and verification 50% is redundancy

25 Other Example R 1 R 2 R After redundancy P (R) = 0.94

26 Types of Maintenance Preventive Routine inspection & servicing Prevents failures Basis for doing Time: Every day Usage: Every 300 pieces Inspection: Control chart deviations Breakdown Non-routine inspection & servicing Remedial Basis for doing Equipment failure

27 Preventive & Breakdown PREVENTIVE MAINTENANCE Meliputi inspeksi rutin untuk menjaga fasilitas peralatan dalam kondisi baik dan mencegah kerusakan BREAKDOWN MAINTENANCE Memperbaiki peralatan yang telah rusak

28 Formula Expected number of breakdowns = [(number of breakdowns)x(corresponding frequency)] Expected breakdown cost = (Expected number of breakdowns)x(cost per breakdown) Preventive Maintenance cost = Expected breakdowns cost if service contract signed + cost of service contract

29 Contoh Aplikasi Suatu perusahaan beroperasi dengan mengunakan sistem komputer. Dalam waktu 20 bulan terjadi kerusakan pada perangkat komputer yang ada. Biaya perbaikan setiap kali terjadi kerusakan adalah Rp 300 ribu Jumlah Kerusakan Jumlah Bulan Terjadinya Kerusakan Total 20 Saat ini perusahaan menerima tawaran kontrak preventive maintenance dari pihak ketiga. Meskipun misalnya nanti perusahaan memutuskan untuk menerima penawaran preventive maintenance tersebut, kerusakan akan tetap terjadi dengan perkiraan rata-rata kerusakan satu mesin per bulan. Nilai kontrak yang ditawarkan adalah Rp 150 ribu per bulan.

30 4-Langkah Pengerjaan 1. Hitung expected number of breakdowns (tanpa preventive maintenance) 2. Hitung expected breakdown cost per month (tanpa preventive maintenance) 3. Hitung expected breakdown cost per month (dengan preventive maintenance) 4. Bandingkan kedua pilihan yang ada.

31 Jawaban 1. Expected number of breakdowns = 1,6 kerusakan per bulan. 2. Expected breakdown cost = Rp per bulan 3. Preventive Maintenance cost = Rp per bulan 4. Tanpa Preventive Rp sedangkan dengan preventive Rp Terima tawaran kontrak.

32 Breakdown Maintenance Reliability and preventive maintenance are seldom perfect. Good Maintenance facility: Well-trained personnel Adequate resources Ability to establish a repair plan and priorities Ability and authority to do material planning Ability to identify the cause of breakdowns Ability to design ways to extend MTBF.

33 Isu Mengenai Pemeliharaan TPM (Total Productive Maintenance) Combines total quality management with strategic view of maintenance from process and equipment design to preventive maintenance. Reducing variability & Improving Reliability designing machines that are reliable, easy to operate and easy to maintain. Emphasizing total cost of ownership when purchasing machines, so that service and maintenance are included in the cost. Developing preventive maintenance plans that utilize the best practices of operators, maintenance departments and depot services. Training workers to operate and maintain their own machines.

34 Challenger 28 Januari detik Bocor tangki bahan bakar bagian kanan. Columbia 1 Februari 2003 Meledak saat akan mendarat