2. Macam Macam Perawatan

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WHY DO MACHINES FAIL? • Wajar – – – – –

Aus (wear): scuffing, galling, fretting, abrasion Lelah (fatigue) Karat (corrosion) Erosi (erosion) Penuaan (aging)

• Prematur – Pelumasan tidak bagus (kualitas, kuantitas pelumas, periode penggantian pelumas tidak benar) – Kotor/kontaminasi – Overheated – Misalignment (pada kopling, bearing, belt, rantai) – Sifat material berubah??????

WHY DO MACHINES FAIL? Brinelling karena overloaded

Overheated

WHY DO MACHINES FAIL? Fatigue damage

FAILURE PATTERN

Failure Rate

• Dahulu orang percaya bahwa semua kegagalan komponen mengikuti “bathtub curve” • Ternyata bathtub curve tsb hanya mencakup 4% dari populasi komponen (mis: bearings, connector, switches, IC, PCB, etc) • Age related failure hanya 11% Start up cycle

Break down cycle Useful life period (wealth cycle) Critical wear point Time

FAILURE PATTERN Arti dari bathtub curve • Start up cycle: kerusakan terjadi karena ketidak sempurnaan material, pengerjaan, pemasangan, pelatihan operator. Pada saat awal komponen mesin akan saling menyesuaikan karena berbagai ketidak sempurnaan pembuatan (permukaan masih kasar yang saling menghaluskan) • Useful life: mesin berproduksi dengan baik karena komponen2nya sudah saling menyesuaikan • Break down cycle: komponen mengalami fatigue, keausan berlebih, erosi, abrasi dlsb. Bath tube curve cocok untuk komponen mekanik.

FAILURE PATTERN 4%

7%

2%

14%

68% 5%

Age related failure (1, 2, 3)

Age unrelated failure (4, 5, 6)

Artinya: komponen akan rusak ketika sudah tua

Artinya: komponen bisa gagal secara random, pada saat masih muda maupun sesudah tua

FAILURE PATTERN POPULATION PERCENTAGE

1 2 3 4 5 6

FAILURE PATTERN

1940

1950

1960

1970

1980

1990

2000

Kategori Mesin/Peralatan Produksi • Ditinjau dari tingkat kerumitan, harga, peranan dan resiko dalam suatu mata rantai produksi, mesin digolongkan atas. – Critical – Essential (Potentially critical) – General Purpose (Non critical)

• Kategori ini untuk menentukan strategi perawatan yang cocok.

Mesin “Critical” • • • •

Kalau rusak dapat membahayakan Kalau rusak proses produksi terganggu Investasi mahal Biaya perbaikannya mahal (misal: high speed turbine) • Waktu untuk perbaikan lama

Mesin “General Purpose” • Kalau rusak tidak membahayakan • Kalau rusak tidak mengganggu proses produksi • Investasi tidak mahal • Biaya perbaikan tidak mahal • Mempunyai unit cadangan • Tidak mengakibatkan kerusakan sekunder

Mesin Essential (Potentially Critical) • Di antara mesin critical dan general purpose.

PERKEMBANGAN STRATEGI PERAWATAN • Sebelum PD II rancangan mesin sederhana, kokoh, berat, “robust” • Perawatan sederhana • Munculnya sistem produksi massal berarti kerusakan mesin produksi dapat menimbulkan kerugian besar • Bersamaan dgn itu, rancangan mesin bertambah rumit, ringan, ramping • Perlu strategi baru dalam perawatan

PERKEMBANGAN STRATEGI PERAWATAN

Generasi pertama -Perbaiki kalau rusak 1940

1950

Generasi kedua -Availability lebih baik -Umur peralatan lebih panjang -Efektifitas biaya lebih baik

1960

1970

Generasi ketiga -Availability dan reliability lebih baik -Keselamatan lebih baik -Kualitas produk lebih baik -Tidak mencemari lingkungan -Umur peralatan lebih panjang -Efektifitas biaya lebih baik

1980

1990

2000

PERKEMBANGAN STRATEGI PERAWATAN

Generasi pertama -Perbaiki kalau rusak 1940

1950

Generasi kedua -Overhaul terjadwal -Sistem utk perencanaan dan pengendalian kerja -Komputer besar dan lambat

1960

1970

Generasi ketiga -Pemantauan kondisi mesin -Design for reliability and maintainability -Hazard studies -Komputer kecil, cepat -FMEA -Expert systems -Multi tasking and teamworks

1980

1990

2000

PERKEMBANGAN FILOSOFI PERAWATAN • Break down (run to failure) maintenance : mesin dioperasikan tanpa perawatan sampai kerusakan terjadi. Kerusakan primer hampir selalu menimbulkan kerusakan sekunder. • Preventive maintenance (PM) atau time base maintenance: mesin di”maintain” secara terjadwal setelah beroperasi dalam jangka waktu tertentu. • Predictive (on condition based) maintenance (PdM): kondisi mesin dipantau secara menerus. Bila terdeteksi adanya ketidak normalan baru diambil tindakan. • Proactive (prevention) maintenance: kerusakan yang terjadi dicari penyebabnya untuk mencegah kerusakan yang sama berulang.

PERKEMBANGAN FILOSOFI PERAWATAN Strategy

Reactive, Run To Failure

Preventive Maintenance

Predictive Maintenance

Proactive Maintenance

Definition

Fix it when it breaks, Run to Failure

Conduct maintenance at regular intervals

Maintain based upon known condition/standard

Redesign to eliminate root cause of failure

Advantages (when implemented correctly)

Cheap

Can be planned for or scheduled

Can spot potential failure

Less maintenance required

Disadvantages (when implemented correctly)

High spare stock level. Emergency outages

Unnecessary replacement of parts. Poor utilization of labor.

Costly if implemented incorrectly

Could be expensive

Oil change

Automobile tires

2 year lease

Component you Head light would maintain

Run-to-Failure Maintenance • Run-to-failure maintenance is sometimes called "crisis maintenance" for good reason. This has been the dominant form of maintenance for a long time, and its costs are relatively high because of unplanned downtime, damaged machinery, and overtime expenditure.

• REACTIVE: – Trouble / Breakdown / RTF / M&R • “Fix it when it breaks” – “Run to failure”

• PREVENTIVE (PM): Functional Checks of Equipment – For Rotating Equipment: • • • • •

Lubrication Belts Filters Housekeeping Visual Observations

– Work Orders generated Facility Asset Management Information System

Periodic Preventive Maintenance • Periodic preventive maintenance, which is sometimes called "historical" maintenance. This is where the histories of each machine type are analyzed and periodic overhauls are scheduled to occur before the statistically expected problems occur. It has long been known that most groups of similar machines will exhibit failure rates that are somewhat predictable if averaged over a long time. This gives rise to the so-called "Bathtub Curve" which relates failure rate to operating time, as follows:

PREVENTIVE MAINTENANCE (TIME BASED) • Preventive maintenance adalah suatu tindakan untuk menjaga agar peralatan tetap dapat beroperasi dengan cara inspeksi, deteksi dan pencegahan kerusakan. • Semua kegiatan perawatan dijadwal berdasar waktu (mingguan, bulanan, triwulanan, 1000 jam, 3000 jam dlsb) • Pelaksanaan mudah, tinggal mengikuti jadwal: pembersihan, pengecatan, pelumasan, pemeriksaan, perbaikan.(Rencana dan jadwal tahunan harus disiapkan). • Penganggaran mudah: anggaran umumnya dibuat tahunan.

PREVENTIVE MAINTENANCE (TIME BASED) • Murphy Law: Kerusakan biasanya terjadi pada waktu peralatan sangat dibutuhkan. • Contoh: Pada saat banyak order, peralatan produksi rusak. Perbaikan dapat memakan waktu beberapa jam atau beberapa hari. • Hal yang tidak menguntungkan ini dapat dicegah dengan PM. • Alasan lain: keselamatan, penghematan biaya perbaikan karena kerusakan sekunder.

PREVENTIVE MAINTENANCE (TIME BASED) Peralatan apa yang cocok untuk di PM? • Peralatan yang menyebabkan : – – – –

“major shut down”, penurunan kualitas produk, kerusakan terhadap komponen terkait, bahaya kepada karyawan

• Penerangan, lantai, plafon yang dapat mengganggu kualitas produksi atau menimbulkan kondisi kerja yang buruk.

PREVENTIVE MAINTENANCE (TIME BASED) Peralatan apa yang tidak perlu di PM? (cukup dg RTF) • Peralatan yang mempunyai cadangan • Peralatan yang harganya lebih rendah dari biaya PM • Peralatan yang umur harapannya cukup panjang tanpa PM

Example •

3 pumps of exactly the same type and manufacturer, however, each requires different maintenance strategy. – Pump A: Preventive maintenance (PM) – Pump B: Break down maintenance (RTF) – Pump C: Periodic test to eliminate hidden failure or PM

Pump A (continuous running)

Production Train 1 100 l/min cooling water

Pump B (continuous running) Pump C (standby, hidden failure)

100 l/min cooling water

Loss USD 200,000./day when stop

Production Train 1 Loss USD 200,000./day when stop

Example • • • •

3 pumps of exactly the same type and manufacturer Pump A: Predictive maintenance ??? Pump B: Break down maintenance??? Pump C: Periodic test??? Pump A (continuous running)

Production Train 1 100 l/min nitric acid

Pump B (continuous running) Pump C (standby, hidden failure)

100 l/min nitric acid

Loss USD 200,000./day when stop

Production Train 1 Loss USD 200,000./day when stop

PM cost

PREVENTIVE MAINTENANCE (TIME BASED)

Lebih banyak uang untuk PM, terjadi sedikit keterlambatan Lebih sedikit uang untuk PM, terjadi banyak keterlambatan

% maintenance delay

PREVENTIVE MAINTENANCE (TIME BASED) Cost

Production cost as affected by maintenance cost

Production cost due to delay #1 PM cost

#2

#3 % maintenance delay

PREVENTIVE MAINTENANCE (TIME BASED) • #1: terlalu banyak PM, menghamburkan tenaga, suku cadang dan uang. • #2: sangat kurang, akan terjadi banyak kerusakan • #3: sangat optimum, tapi jarang tercapai. Indikasinya 20% peralatan mengalami kerusakan sebelum diperbaiki. • Bila tidak terjadi kerusakan sebelum diperbaiki berarti PM terlalu banyak.

PREVENTIVE MAINTENANCE (TIME BASED) • Rumus empirik untuk menentukan faktor PM (makin tinggi nilainya PM makin perlu) PM = D(A+B+C)/(EF) PM = inspection factor D = number of break down/year A = cost of break down repairs B = cost of lost production C = cost of repairing other equipment involved in the breakdown E = cost of PM activity (average) F = number of PM cycle per year

PREVENTIVE MAINTENANCE (TIME BASED) Do PM (Preventive Maintenance) if number of break down x Average cost per break down x 70% > cost of PM system

PREVENTIVE MAINTENANCE (TIME BASED) Optimum Frequency/Interval for PM ditentukan berdasar: • Failure history • CM history • Manufacturer recommendations • Industry history • Regulatory requirements • Design and operation considerations • Other tasks scheduled on the same component • Planned outages • Ability to gain access to the component • Operator capability • PdM monitoring activity • Environment

PM Tasks Type of Task

Example

Inspection

Look for leak in hydraulic system

Cleaning

Remove debris from machines

Tightening

Tighten anchor bolts

Operating

Warming up machine/prepare for operation

Adjusting

Adjust tightening bolt

Take reading

Read temperature, pressure, vibration

Lubricate

Add oil

Scheduled replacement Remove and replace pump Analysis

History analysis of a type of machine

Interview operator

Ask operator how machine is operating

PREVENTIVE MAINTENANCE (TIME BASED) Inspection • Memastikan performansi peralatan sesuai perancangan • Mengevaluasi semua komponen terhadap masalah yang potensial menimbulkan kerusakan • Mengidentifikasi komponen yang dapat menyebabkan kerusakan dan mengestimasi waktu sampai kerusakan terjadi. Contoh: dinding pressure vessel mengalami penipisan selama dioperasikan.

PREVENTIVE MAINTENANCE (TIME BASED) Inspeksi dilakukan • Karena tuntutan peraturan: Pressure vessel harus diinspeksi secara berkala sesuai dengan peraturan pemerintah tentang keselamatan kerja. • Karena mesin tidak dilengkapi dengan cadangan dan beresiko terhadap keberlangsungan proses produksi. • Pada peralatan yang sedang rusak

Equipment availability

CORRECTIVE MAINTENANCE (PERBAIKAN) SEBAGAI RESPONS TERHADAP INSPEKSI DALAM PM

Biaya perbaikan

PREDICTIVE MAINTENANCE (PdM)

Preventive Maintenance

Time Based Maintenance

Condition Based Maintenance

Predictive Maintenance • Predictive maintenance allows management to control the machinery and maintenance programs rather than vice versa. In a plant using predictive maintenance, the overall machinery condition at any time is known, and much more accurate planning is possible. • Benefits of Predictive Maintenance – The major benefit of predictive maintenance of mechanical equipment is increased readiness due to greater reliability of the equipment. The trending over time of developing faults in machines can be carefully done so as to plan maintenance operations to coincide with scheduled shutdowns.

SAAT PERAWATAN YANG TEPAT Predictive Maintenance (PdM). Perbaikan tepat pada waktunya

Perbaikan dilakukan terlalu awal

Mesin terlambat diperbaiki

Time based preventive maintenance (PM)

Predictive Maintenance Technologies • • • • • • • •

Lubrication analysis Vibration analysis Infrared thermography Partial discharge (for generators, transformers etc) MCSA (Motor Current Signature Analysis) for electric motors Operating parameters (temperature, pressure, flow rate etc) Ultrasonic Acoustic Smell, looking, feel, listen

PROACTIVE MAINTENANCE (PREVENTION MAINTENANCE) • Kerusakan premature (belum saatnya) dapat terjadi atas peralatan • Mencegah perbaikan berulang atas kerusakan premature • Kerusakan jenis tersebut harus dicari penyebabnya dengan Root Cause Analysis (RCA) • Improvement/redesign komponen dilakukan berdasar hasil RCA

Proactive Maintenance Technologies • • • • • • •

Dynamic Balancing Precision Shaft Alignment Ultrasonic Testing / Air & Steam Belt / Pulley Alignment Acceptance Testing Water / Air Flow balancing & Measuring Metering

Pro-active Maintenance • Pro-active maintenance, which uses a variety of technologies to extend the operating lives of machines and to virtually eliminate reactive maintenance. The major part of a pro-active program is root cause failure analysis (RCA), which is the determination of the mechanisms and causes of machine faults. The fundamental causes of machine failures can thus be corrected, and the failure mechanisms can be gradually engineered out of each machinery installation.

Maintenance Strategy Comparation Maintenance Strategy

Technique Needed

Human Health Parallel

Proactive

Monitoring and Cholesterol and blood correction of “failing root pressure monitoring, causes” followed by diet control

Predictive

Monitoring of vibration, temperature, alignment, pressure, wear debris

Detection of heart disease by ECG or ultrasonic

Preventive

Periodic components replacement

By-pass or transplant surgery

Break down

Large maintenance budget

Heart attack or stroke

RCM (Reliability Centered Maintenance)

RCM (Reliability Centered Maintenance) RCM (Reliability Centered Maintenance)

Reactive, RTF

PM, Time Based

PdM, Condition Based, Predictive

Proactive

•Small items

•Subject to wear out

•Random failure patterns •Age exploration

•Non critical

•Consumable replacement

•Not subject to wear

•RCFA

•PM Induced failures

•FMEA

•Inconsequential •Unlikely to fail

•Failure pattern known

•Redundant RCFA = Root Cause Failure Analysis FMEA = Failure Mode and Effect Analysis

•Acceptance testing

RCM (Reliability Centered Maintenance)

RULES FOR BREAKDOWN MAINTENANCE • • • • • • •

If equipment is redundant Low cost spares available Interruptible process, stock pile Safe failure modes Long MTTF/MTBF Low cost secondary damage Quick repair/replacement (low cost of interuption of production)

RULES FOR PREVENTIVE MAINTENANCE • • • • • •

Statistical failure rate available Narrow failure distribution (predictable MTBF) Maintenance restore full integrity Single failure mode (known) Low cost of regular overhaul/replacement Unexpected interruption to production is expensive (scheduled interruption is not so bad) • Low cost spares available • Reduced number of breakdown is required • Costly secondary damage

RULES FOR PREDICTIVE MAINTENANCE • Expensive/critical machinery • Long lead time for replacement (no spares) • Uninterruptible process (both regular and unexpected)costly • Large/complex machinery • Overhaul expensive (need highly trained people) • Reduced number of highly skilled maintenance people • Cost of monitoring program is acceptable • Safety is priority (failure dangerous) • Remote/mobile equipment • Failure is not indicated by operation degeneration • Costly secondary damage

ALIRAN INFORMASI Dari mana pekerjaan perawatan bermula? • Internal (dari dalam department of maintenance): tugas preventive maintenance dan corrective maintenance • Eksternal (dari luar departemen): permintaan dari manajer produksi, rehabilitasi

Komponen Penting dalam Perawatan

Gunung Es Perawatan

Organisasi Perawatan

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