Reliability Maintenance Engineering 3 - 1 Measuring Availability

Reliability Engineering

Fred Schenkelbergfms@fmsreliability.com

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