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WBG052114205536FLL
NC AWWA-WEA Spring Conference
J.D. Solomon, PE, CRE, CMRP [email protected]
April 13, 2015
RELIABILITY OF INFRASTRUCTURE SYTEMS: MEANING AND APPLICATIONS
Today’s Discussion - Topics
1. Reliability Defined
2. Reliability in the Asset Lifecycle
3. Reliability in Practice
4. Case Study: Reliability Assessment Defers $25M
WBG052114205536FLL
Reliability Defined
What is Reliability?
Reliability is the probability that an item will perform its intended function for a specified interval under stated conditions.
Key aspects of the definition
• Probability
• Function
• Time
• Conditions
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Reliability and Quality
Reliability is the probability that an item will perform its intended function for a specified interval under stated conditions.
Quality is a subjective term for which each person has his or her own definition. In technical usage, quality can have two meanings: 1. the characteristics of a product or service that bear on its ability to satisfy stated or implied needs. 2. a product or service free of deficiencies.
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Reliability function usually leads in the design process and Quality function usually leads
in the production/construction process.
Reliability and Risk
Reliability is the probability that an item will perform its intended function for a specified interval under stated conditions.
Risk is the effect of uncertainty on objectives. An effect is a deviation from the expected – either positive or negative.
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Reliability in concerned with establishing the expectations and Risk is concerned with
managing the deviations from those expectations. Uncertainty is present in both and that
overlap ties the two together.
For the Financial Types….Reliability and Risk
If there is 100 percent reliability, then there is no risk. (let us assume this is possible)
Can we afford this?
Herein lies is a key conundrum.
Remember the old adage: You can have 2 of 3 things – quality, cost, and speed – but you can’t have all three.
Speed – to market and to repair – is a given in modern society.
So the more quality and more reliability we have – which means less uncertainty and less risk - then the more things will cost.
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Reliability and Availability
Reliability is the probability that an item will perform its intended function for a specified interval under stated conditions.
Availability is the ability of a product (item) to be in a state to perform its designated function under stated conditions at a given time.
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For repairable items Reliability evaluates the time until the first failure and Availability evaluates the time after the first failure.
If non-repairable items, then reliability and availability are the same. If maintenance and redundancy are perfect for repairable
items, then the two are essentially the same.
Reliability and Availability
Reliability is the probability that an item will perform its intended function for a specified interval under stated conditions.
Availability is the ability of an item to be in a state to perform its designated function under stated conditions at a given time.
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Question: Does everything need to be 100% available? Consider certain types of standby equipment and peaking facilities.
Dependability is the degree to which an item is operable and capable of performing its required function at any randomly chosen time during its specified operating time (or mission).
WBG052114205536FLL
Reliability in the Asset Lifecycle
Asset Lifecycle
Planning and Design
Production and/or
ConstructionOperations Maintenance
Asset Lifecycle
Reliability ReliabilityQuality Mix
Key concept: Design function establishes the maximum reliability. Production/Construction
ensures that the designed reliability is put into service. Operations and Maintenance
cannot improve reliability beyond what is established in the design.
Asset Lifecycle
• Designed
function is
delivered
• Designed
& produced
function sees
maximum
stresses and
degrades
• Reliability
establishes
the function
• Reliability
restores the
function
MaintenancePlanning and
Design
Production and/or
ConstructionOperations
Renewal and
Replacement
Decisions
Reliability Engineers are most active in the Design and Maintenance Phases
WBG052114205536FLL
Reliability in Practice
Reliability in Maintenance
System Reliability Function and Policy
Preventative Maintenance Analysis and Optimization
Corrective Maintenance Analysis
Condition Assessment and Strategies
Predictive Maintenance
Testability (including Built-In)
Spare Parts Analysis and Logistics
Planning and Scheduling Optimization
Redundancy and Common Mode Failure
Resource Evaluations and Management
O&M Strategies
Reliability in Design
Environmental and Use Factors
Physics of Failure, including Stress-Strength
Failure Modes and Effects
Common Mode Failure
Tolerance and Worst Case
Design of Experiments
Fault Tolerance
Human Factors Analysis
Reliability Apportionment
Systems Optimization
At the Interface of Maintenance and Design
Reliability Assessments
Maintenance Assessments
Renewal and Replacement Models
Maintenance Improvement Frameworks and Implementation
Root Cause Analysis and Continual Improvement Programs
O&M Data Management and Predictive Maintenance
Risk Assessments and Modeling
Strategic Design Support
Strategic Plans and Master Plans
WBG052114205536FLL
Case Study: Reliability Assessment Defers $25 M
Reliability Assessments - General
Vary widely in scope depending on system type and problem frame
Approach for this assessment:1. Establish the Problem Statement
2. Verify and calculate future stresses (loads/demands/flows)
3. Establish the system condition and asset performance history
4. Perform systems reliability analysis
5. Evaluate ability to predict or accept risk associated with potential reliability shortfalls
6. Determine Repair or Replacement Alternative
7. Document Repair or Replacement Alternative
System Infrastructure
Intake / RWPS
RWPS
Intake
WTP
30” (1930) & 42” DIP (2009)~8 miles
36” outlet (1930)42” outlet (2009)Cross-connected
Original 1954, upgraded in 199742” DIP (1997)
~6 miles
48” PCCP (1961) ~11 miles
Original 1961; added PS 1973
Raw Water Operations
Stovall WTP
Table Rock North Saluda
1. 23 mgd gravity
4. 20 mgd pump (1 of 3 working)3. 9 mgd pump (2 of 3 working)
2. 25 mgd gravity
75 mgd of 95-100 mgd maximum day system demand
Targeted Reliability: 45 mgdTargeted Reliability: 30 mgd
2009 Master Plan
Outdated and base data did not reflect post-2008 economic factors
Updated with current data and new statistical analysis
Probabilistic analysis added to better forecast range of uncertainty and risk• Per capita use
• Population growth
• Non-residential growth
• Peaking factors
• Drought conditions
Analysis of Past Operating Data
Verification of reported operating paradigm
Confirmation of how water demands correlated to use of systems, especially pump systems
Identification of potential anomalies due to equipment failures, equipment limitations, and/or natural environment (droughts or natural disasters)
Simulated Future Pumping Requirements
Annual Pattern For Hourly Flow
ProbabilisticAverage DayForecast for EntireSystem
Raw Water Supply Operational Rules
Future Hourly Pattern2015-2022
Reliability - Processes, Tools, and Approaches
Structured Processes and Approaches• Failure Mode and Effects Analysis (FMEA)
• Reliability Block Diagrams (RBD)
• Fault Tree Analysis (FTA)
• Root Cause Analysis (RCA)
Data, Statistics, and Software Applications• Factory Data, Test Data, Field Data
• Predictions (failure rates, warranties, etc.)
• Discrete and Continuous Probability Distributions
• Commercially Available Software Applications
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Summary of Reliability Assessment
1. Not a question of “if” but “when”
2. Proposed capital improvements would replace things because they were old but did not improve overall reliability of system
3. Some of the capital improvements were for “redundancy”, but actually would not improve redundancy at all based presence of common mode failures
4. Better dollars were spent on more proactive Corrective Maintenance (CM) planning and mitigation strategies
5. Reliability Assessment led to a better understanding of what reliability and redundancy really meant, and in doing so helped to better quantify and treat risks
WBG052114205536FLL
NC AWWA-WEA Spring Conference
J.D. Solomon, PE, CRE, CMRP [email protected]
April 13, 2015
RELIABILITY OF INFRASTRUCTURE SYTEMS: MEANING AND APPLICATIONS
