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Presentation to the 2010 Fall Technical Conference
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Equipment Availability Analysis
Fred Schenkelberg, FMS Reliability Angela Lo, Kaiser Permanente
Overview
• Bottling line– Multiple bottle sizes– Multiple flavors
• Build to finished goods inventory– Mixed shipments of FG to distribution centers– Daily shipments– Broad variation in demand of bottle size and flavor
Introduction
• Throughput directly related to inventory size• Inventory is expensive
• Goal is to improve the throughput to equipment capabilities seen over long runs to short runs.
How much inventory reduction is possible?
Existing Analysis
• The filler (bottleneck) has the following values
MTBF =Minutes of operation
# of failures=46.5 minutes
MTTR =Minutes of downtime
# of failures=2.45 minutes
Availability =MTBF
MTBF + MTTR⎛⎝⎜
⎞⎠⎟100%=95%
Throughput =Availability x 400 bottles/min=380 bottles/min
Given a 400 bottles / min equipment average capability
Desired Improvement
• (Anecdotally) the line runs better over time
• Improve the analysis to calculate MTBF over various length runs
• Make the calculations time dependant
Mean Cumulative Function
Filler - Time to Failure
Filler - Time to Repair
General Renewal Process
• Assumptions– Time to first failure is known (Weibull)– Time to repair is negligible relative to runtime.
• Permit modeling of repairs that are between– As good as new– As bad as old
Cumulative Failure Intensity vs Time
New MTBF ValuesLength of
run (minutes)
120 240 480 960 1440
Cumulative MTBF
7.17 9.29 11.56 13.26 14.16
Instantaneous
MTBF20.75 26.53 32.57 37.45 34.72
The long term MTBF value is 45.6, resulting in approximate 2.63 minutes to build 1000 units. Building the same inventory faster, permits the inventory reduction.
ResultsLength of
run (minutes)
120 240 480 960 1440
Time to build 1000
units3.53 3.33 3.19 3.12 3.09
%Improvementwith
380/min25.5 20.9 17.5 15.6 14.7
For a 4 hour run (240 minutes) if the equipment is improved toa 380/minute throughput, there is at least a 20% inventory reduction
Summary & Conclusion
• Using the GPP model to estimate MTBF for various run time and calculate throughput
• The possible throughput improvement costs can now be balanced with potential cost savings
• The improved performance visibility encouraged a study of the shift change and restart behavior
Contact Information
Fred SchenkelbergReliability and Management Consultant
[email protected]+1 (408) 710-8248