Reliability Maintenance Engineering 3 - 1 Measuring Availability
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Transcript of Reliability Maintenance Engineering 3 - 1 Measuring Availability
Reliability Engineering
Fred [email protected]
MEASURING AVAILABILITY Day 3 Session 1
Objectives
• Structuring a hierarchy of goals and measures• Determining constraints and bottlenecks• Developing five measures of availability• Obtaining measures for critical equipment• Embarking on structured approach to improve
availability. • Formulating a condition monitoring program
Availability & Business
• Translating business objectives into availability
• Cost• Yield• Throughput• ROI• …
Hierarchy of Goals
• Business goals to line, system, or process
• Decision & budget level
• Physical alignment
• Process alignment
Actionable level
• Apportionment
• RBD and apportionment
• Available• Reliability• Maintainability
Sample goal statements
• Line x in plant y operates with 90% availability over each shift
• Function• Environment• Probability• Duration
• Compressor x on equipment y provides z pressure with 95% reliability over 5 years of continuous operation.
• Replacement of compressor x occurs 90% of the time in less than 2 hours with existing equipment and diagnostics.
Performance Reporting Flow
Discussion & Questions
Process flow modeling
• Map the process including
• Physical item movement
• Information movement• Transitions, decisions• Durations and gates
Constraints
A limiting factor
• Capacity• Throughput• Budgetary
Bottlenecks
: a delay caused when one part of a process or activity is slower than the others and so hinders overall progress
• Opportunity• Optimization
Examples
• Bottling plant
• Filler equipment– 600 per hour fill rate– Lowest rate of all
equipment
• Buffer (inventory holding area)– Limited by size or floor
space
Discussion & Questions
Availability
• Ratio of the expected value of uptime to the aggregate of the expected values of up and down time.
Inherent Availability, Ai
• The probability of satisfactory operation at given point in time under stated conditions in an ideal support environment.
• Downtime only counts corrective maintenance and does not include– Logistics time– Administrative time– Preventative
maintenance
• Items under control of equipment designer.
Achieved Availability, Aa
• Probability of satisfactory operation at given point in time under stated conditions in ideal support environments
• Downtime only includes active preventative and corrective maintenance time (wrench time).
• Does not include– Logistics time– Administrative time
Operational Availability, Ao
• Probability of satisfactory operation at given point in time under stated conditions with actual support environment.
• Downtime includes everything.
Reliability/
Supportability/ Maintainability/
Design “Cause” Operational “Effect”
Operation
Logistics Maintenance
Time toSupport (TTS)
Time toMaintain (TTM)
Time toFailure (TTF)
System Downtime
Time
Discussion & Questions
Critical Equipment
• What to optimize?
• Bottleneck equipment
• Quality element
• ‘Where the magic occurs’
Risk Minimization
• Long repair times
• Safety issues– Explosion– Releases
• Poor Quality impact
What to Measure
• Direct performance
• Performance indicators
• Quality stability
• Leading indicators– Current– Pressure
Measurement Techniques
• Product measurements
• Process parameters
• Process Control
• Inspections and Studies
Discussion & Questions
Availability Improvement Planning
• Assessment
• Process mapping
• Data collection
• Characterize current state (and reason for current state)
Level of detail
• Enough data to make informed decisions
• Is the process stable?• What causes
differences?
• What is cost of downtime?
Focus on Value
• Select improvement projects and tasks that have highest ROI– Low hanging fruit– Major return potential– Portfolio approach
• Estimate value and risk before selecting tasks
Program Approaches
• Major redesign
• Incremental improvements
• Process control (stability)
• Backup plan
Discussion & Questions
Condition Monitoring
• Regular observations or measures of indictors of impending failure.
– Oil level– Current draw– vibration
Image from article by Ricky Smith on The Maintenance Phoenix site
Experiments, Models and Measures
• Start measuring today
• Engineering judgment and experience to starting monitoring
• Design experiments to determine effective predictors
Considerations
• Ability to detect fault indicators
• Lead time requirements– Spare parts– Specialized equipment
• Scheduling optimization
Discussion & Questions
Summary
• Structuring a hierarchy of goals and measures
• Determining constraints and bottlenecks
• Developing five measures of availability
• Obtaining measures for critical equipment
• Embarking on structured approach to improve availability.
• Formulating a condition monitoring program
Measuring Availability