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

www.fmsreliability.comfms@fmsreliability.com+1 (408) 710-8248