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Reliability Maintenance Engineering Day 3 session 1 Measuring AvailabilityThree day live course focused on reliability engineering for maintenance programs. Introductory material and discussion ranging from basic tools and techniques for data analysis to considerations when building or improving a program.
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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