Preventive Maintenance-Presentation

Preventive Maintenance-Presentation - Preventive...

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Preventive Maintenance Chris Brammer Mike Mills
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Why is preventive maintenance important? ± Reduce equipment downtime ± Reduce environmental and workplace hazards ± To save money
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Project overview ± Build preventive maintenance scheduler ± Assess potential losses ± Find frequency of failure ± Determine optimal maintenance policy ± Assist in Data Formation and Collection ± Fortran Program – Quang Nguyen ± Sample plant: Tennessee Eastman
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Tennessee Eastman Process Plant
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Theory Maintenance types: ± Corrective (CM) ± Event driven (repairs) ± Preventive (PM) ± Time driven ± Equipment driven ± Opportunistic
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Equipment failure modes ± How does an equipment fail? ± Why does it fail? ± Preventive maintenance…
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Equipment Data ± Equipment type ± Failure type ± Mean time between failure ± Time needed for CM ± Time needed for PM ± PM interval ± Economic loss ± CM cost ± PM cost ± Inventory cost
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Equipment Types ± Valves ± Pumps ± Compressor ± Reactor ± Flash Drum ± Heat Exchangers ± Stripping Column
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Failure Types ± Fatigue ± Corrosion ± Wear ± Overload ± Contamination ± Misalignment
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Mean time between failure… ± Log of equipment for particular time period ± Literature / Assumptions-Probability MTBF NS2
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Slide 10 NS2 Shouldn't this be MTBF??? Nico Simons, 4/13/2007
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Failure frequency Equation: •Exponential distribution for all failures = P MTBF t 1 1 ln P = probability t= time of failure MTBF = mean time between failure
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Exponential distribution (graph) Exponential Distribution with MTBF of 100 days 0 0.2 0.4 0.6 0.8 1 0 50 100 150 200 250 300 350 400 Days Probabilit y of Failure . 0.6321 probabilty of failure by the MTBF
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Time Needed for CM & PM ± Why? ± Calculating Labor Costs ± Duration of Job ± Scheduling
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Preventative Maintenance Interval (PMI) Based on MTBF ± High Frequency MTBF – Shorter PM Interval ± Low Frequency MTBF – Longer PM Interval ± Adjust to optimize cost ± Using a ratio of the MTBF
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Economic Loss ± Losses occurred from reduced or halted process flows ± When CMs is performed ± Equipment with failure that has not been Repaired
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CM Cost ± Economic Loss (EL) ± Labor Costs (LC) ± Inventory Cost (IC) ± CM = EL + LC + IC
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PM Cost ± Economic Loss (EL) ± Labor Costs (LC) ± Inventory Cost (IC) ± PM Interval (PMI) ± PM = EL + LC + IC ± Per PMI
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Inventory Cost ± Inventory Cost – Opportunity Cost ± ± PC = Parts Cost ± i = Interest Rate for investing money ± MTBF in years ± Not Accounted for Currently ( ) PC i PC IC MTBF + = 1
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PM Scheduler/Model ± Monte Carlo Simulation ± Optimize occurrence of PMs ± Taking in to account the distributions of failure ± PMs cost < Amount saved ± Verify optimum with plots of total cost versus number of PMs
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Monte Carlo Simulation ± Random Number Generation ± Used to produce a random samples ± Compile/Compute Data easily ± Large sample size – represents system ± Analyze the results ± Optimization ± Change the parameters ± Repeat the simulation
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A Perfect Model ± Equipment Data control ±
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Preventive Maintenance-Presentation - Preventive...

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