“reliability, safety and risk analysis”€¦ · “reliability, safety and risk analysis”...
TRANSCRIPT
“RELIABILITY, SAFETY AND RISK ANALYSIS”
Lecture 1: Introduction to the Course
24/02/2019Piero Baraldi ([email protected])
Piero Baraldi
2
Introduction to the course:• Reliability• Safety• Risk Analysis
Piero Baraldi
Degradation & Failure3
Healthy Degradation initiation
Evolution to… failure
Failure
44Piero Baraldi
Degradation (some examples)
Creeping of turbine blades
Erosion of chokevalves
Crack propagation
Consequences
Failure: an Example from the Nuclear Industry
• Davis-Besse accident (February 2002): Refueling outage a cavity of the size of an American football in the reactor
pressure vessel head. Only a layer of cladding of 7.6 mm thick was left by the corrosion.
5
Repair Action: new lid (600M $) Stop operation until March 2004 (2 years)
Possible consequences in case of rupture Loss of coolant accident (LOCA)
Emergency safety procedures to protect from core damage or meltdown
The jet of reactor coolant might have damaged adjacent control rod drive mechanisms,
hampering or preventing reactor shut-down.
Core melt down
66Piero Baraldi6
Explosion of the platform Deepwater Horizon (Gulf of Mexico), April 2010 (source: sciencesetavenir.fr)
Probable cause: leakage in the oil pumping system
Kamal MEDJAHER and Noureddine ZERHOUNI, workshop (Politecnico di Milano, 2015)
11 fatalities 4.9 billion barrels of oil spilled into Gulf of
Mexico Reputation Reputation Repair efforts:
1 billion dollars spent in Google, Adwords, and Youtube advertising
New CEO $20 billion claims fund $52 million to federal and state health
organizations to fund behavioural healthsupport and outreach programs across theUS Gulf Coast region
Consequences
Failure: an Example from the Oil and Gas Industry
Piero Baraldi
7
Cause: failure of a fishplate (source: Bureau d’enquêtes sur les accidents de transport terrestre)
Train derailment in Brétigny-sur-Orge in July 2013
7 fatalities 21 people were seriously injured 180 people were injured
Failure: an Example from Railway
Consequences
Sources: Keynote of Pierre Dersin at PHM Europe 2014, Muller et al. 1996, Sovacool 2008, Tzanakakis 2013, Kamal MEDJAHER and Noureddine ZERHOUNI workshop (Politecnico di Milano, 2015)
Piero Baraldi
Failure 8
Piero Baraldi
Failure 9
Piero Baraldi10
Failure costs (Some Numbers)
According to Network Rail (UK), rail infrastructure failures and defects are responsible for 14 million minutes of delay per year
In automobile domain, failures cost around 288 millions US $ per day
Sources: Keynote of Pierre Dersin at PHM Europe 2014,
Piero Baraldi
Failure Definition 11
Failure definition: the termination/loss of ability of an item to perform its required function
Failure examples: Total cessation of function
• An engine stops running• A structure collapses
Deterioration/instability of function• a motor that is no longer capable of delivering a specified torque• a structure that exceeds a specified deflection
Piero Baraldi12
Failure prevention
FailuresPrevented by
Design for Reliability Maintenance
Time
NormalDegradation
onsetRepair
Piero Baraldi
Reliability
Reliability (ISO8402): ability to perform an assigned task for a given time under given environmental and operational conditions • Always present in human activities
• From reasonable to rational solutions
13
Piero Baraldi
Reliability engineering: When?
II World War: USA
Radar Vacuum tubes
GERMAN
V1 Missile
14
• lot of failures• poor system performance• high maintenance costs
first reliabilitystudies
first 10 launcheswere allfiascos
first reliabilitystudies
Lusser (German Mathematician):“the reliability of a chain of components is determined by the reliability of the weak link”
Piero Baraldi
Reliability Engineering
• Why do systems fail? (reliability physics to discover causes and mechanisms of failure and to identify consequences)
• How to develop reliable systems?• How to measure/test reliability (in design and operation)? • How to maintain systems reliable (maintenance)?
15
Piero Baraldi
Our big problem…
t
t
X
X
lamp of my wife’s bedside table
lamp of mybedside table
http://www.centennialbulb.org/photos.htm
Piero Baraldi
Our big problem…
t
t
X
X
The failure time is a random variable!
How to represent the failure time?
Probability distribution: fT(t)
lamp of my wife’s bedside table
lamp of mybedside table
Piero Baraldi
Reliability and Probability
Definition of reliability (ISO8402): the ability to perform an assigned task for a given time under given environmental and operational conditions
Operative definition of reliability: Probability that an item performs its assigned task for a given time under given environmental and operational conditions
Piero Baraldi
Reliability, performance and cost: the trade-off
• Objective: design and build product for improved performance Faster aircraft Thermodynamically more efficient energy conversion
devices
• Increase ‘load’ Aircraft decrease weight Energy conversion devices work at higher temperature
• Approach the physical limit of the system Aircraft Increase stress level in its components Energy conversion devices heat-induced losses of
strengths and more rapid corrosion
• Number of failures increases (reliability decreases)
• Countermeasures should be taken (cost increases) Purer material Tighter dimensional tolerance Monitoring & improved maintenance
19
Piero Baraldi
Reliability, performance and cost: the trade-off
• Objective: design and build product for improved performance Faster aircraft Thermodynamically more efficient energy conversion
devices
• Increase ‘load’ Aircraft decrease weight Energy conversion devices work at higher temperature
• Approach the physical limit of the system Aircraft Increase stress level in its components Energy conversion devices heat-induced losses of
strengths and more rapid corrosion
• Number of failures increases (reliability decreases)
• Countermeasures should be taken (cost increases) Purer material Tighter dimensional tolerance Monitoring & improved maintenance
20
Use new-design components, thanks to new technologies
Potentially, in the long term:• Better performance• Lower costs• Larger reliability
But in the early stage of introduction of the new technology:• Lower reliability
e.g. iron instead of wood in structures:• Problem of brittle fractures
Piero Baraldi
• Maintenance (IEC60300): set of actions that ensure the ability of an item to be retained in (preventive maintenance) or restored to (corrective maintenance) the functional state required by the purpose for which it was conceived.
Maintenance 21
Failure Maintenance
preventivemaintenance
correctivemaintenance
Piero Baraldi
Maintenance Costs
Derived from M. Garetti
G$/year
Piero Baraldi
23
Introduction to the course:• Reliability• Safety• Risk Analysis
Piero Baraldi
Safety
• SAFETY ≡ freedom from unaffordable harm
Piero Baraldi
Hazard
barrier
No Hazard
Safety
• SAFETY ≡ freedom from unaffordable harm
• The ‘parmesan cheese’ model
Piero Baraldi
Not all barriers work...
Safety
Piero Baraldi
No Hazard
Hazard
Safety: Multiple Barriers
Piero Baraldi
Geological Barrier
Technical BarriersEmbeddingStorage caskOver packsBackfill
Waste
Safety: Multiple Barriers - Example
Piero Baraldi
Hazard
HumanErrors
ProceduralErrorsFaults in
Redundancies
Safety: the Swiss Cheese Model
Piero Baraldi
30
Introduction to the course:• Reliability• Safety• Risk Analysis
Piero Baraldi
The Concept of Risk
Hazard
SafeguardsEnvironment
People
UNCERTAINTY
Piero Baraldi
The Concept of Risk 32
RISK = POTENTIAL DAMAGE + UNCERTAINTY
Dictionary: RISK = possibility of damage or injuryto people or things
Piero Baraldi
Probabilistic Risk Assessment 33
1. What undesired conditions may occur? Accident Scenario, S
2. With what probability do they occur? Probability, p
3. What damage do they cause? Consequence, x
RISK = { Si, pi, xi }
Piero Baraldi
S p x
S1 p1 x1
… … …
SN pN xN
{Si, pi, xi}
Probabilistic Risk Assessment (PRA): Results
Piero Baraldi
RISK = p∙xRisk Measures
Piero Baraldi
RISK = p∙x k(>1)
Risk Measures
Piero Baraldi
RISK = Σipixik(>1)
WARNING:
RISK (A)= RISK (B) A=(P, x); B=(p, X)
RISK REDUCTION:
A: Prevention B: Mitigation, Protection
Risk Measures
Piero Baraldi
The level of risk is not acceptableand risk control measures arerequired to move the risk figure tothe previous regions
The level of risk is broadlyacceptable and generic controlmeasures are required aimed atavoiding deterioration
The level of risk can be tolerableonly once a structured review ofrisk-reduction measures hasbeen carried out
Risk Evaluation: Risk Matrix
Piero Baraldi
Risk Assessment & Management Procedure 39
Piero Baraldi
40
Course Syllabus
Piero Baraldi
Topics
• Basics of probability• Reliability of simple systems• Markov processes for reliability and availability
analysis of more complex systems• Monte Carlo simulation method for reliability and
availability analysis• Estimation of reliability parameters from
experimental data• Maintenance in the energy industry• Probabilistic Risk Assessment• Fault and event tree analysis for identification and
quantification of accidental sequences• Dependent Failures• Importance Measures• Uncertainty and Sensitivity Analysis
Part 1: Reliability
Part 2: Risk
Assessment
Piero Baraldi
Topics (Part 1)
• Basics of probability
t
t
X
X
The failure time is a random variable!
How to represent the failure time?
Probability distributions: fT(t|λ)
Piero Baraldi
Topics (Part 1)
• Basics of probability• Reliability of simple systems
pumping system
Piero Baraldi
Topics (Part 1)
• Basics of probability• Reliability of simple systems• Markov processes for reliability and availability analysis of more
complex systems
Piero Baraldi
Topics (Part 1)
• Basics of probability• Reliability of simple systems• Markov processes for reliability and availability analysis of more
complex systems• Monte Carlo simulation method for reliability and availability analysis
Monte Carlo Simulationfor reliability and availability analysis
Piero Baraldi
Topics (Part 1)
• Basics of probability• Reliability of simple systems• Markov processes for reliability and availability analysis of more
complex systems• Monte Carlo simulation method for reliability and availability analysis• Estimation of reliability parameters from experimental data
(Accelerated) degradationtests
Failure times15.8 h15.9 h15.1 h17.2 h…14.5 h
fT(t|𝜃𝜃)
Piero Baraldi
Topics (Part 1)
• Basics of probability• Reliability of simple systems• Markov processes for reliability and availability analysis of more
complex systems• Monte Carlo simulation method for reliability and availability analysis• Estimation of reliability parameters from experimental data• Maintenance
?
Piero Baraldi
Topics (Part 2)
• (Probabilistic) Risk Assessment• Fault and event tree analysis for identification and quantification of
accidental sequences• Dependent Failures• Importance Measures• Uncertainty and Sensitivity Analysis
48
Piero Baraldi
Topics
• (Probabilistic) Risk Assessment
49
S p x
S1 p1 x1
… … …
SN pN xN
Piero Baraldi
Topics
• Probabilistic Risk Assessment• Fault and event tree analysis for identification and quantification of
accidental sequences
50
Blowout Accident in Oil and Gas Wells during drilling
Blowout
Kick
Piero Baraldi
Topics (Part 2)
• Probabilistic Risk Assessment• Fault and event tree analysis for identification and quantification of
accidental sequences• Dependent Failures
51
electric grid
Piero Baraldi
Topics (Part 2)
• Probabilistic Risk Assessment• Fault and event tree analysis for identification and quantification of
accidental sequences• Dependent Failures• Importance Measures
52
Which is the most«critical» component?
Piero Baraldi
Topics (Part 2)
• Probabilistic Risk Assessment• Fault and event tree analysis for identification and quantification of
accidental sequences• Dependent Failures• Importance Measures
53
Piero Baraldi
Teaching Organization
• Lectures• Exercise Sessions• Project
development of a stochastic simulation code for the estimation of the reliability and availability of a nuclear or energy system
team formed by a nuclear and an energy engineering student.• Seminars
Piero Baraldi
Teaching Organization (energy and nuclear engineering students)
February 25th
April 17th
ENERGY ENG. STUDENTS
NUCLEAR ENG. STUDENTS
June7th
Part 1
May 22th
Part 2
Piero Baraldi
Final Evaluation
Written exam (40% of the final mark):• Exercises and questions on all the course topics
Oral exam (40% of the final mark):• 2 questions (on all the course topics)
Project (20% of the final mark)
To be admitted to the oral it is necessary to have at least 18/31 in the written exam
Piero Baraldi
Course Material
• Lecture slides (http://www.lasar.polimi.it/)• Zio E., An introduction to the basics of reliability and risk analysis,
World Scientific, 2007.• Zio E., Computational methods of reliability and risk analysis, World
Scientific, 2009.• Zio E., The Monte Carlo Simulation Method for System Reliability and
Risk Analysis• Zio E., Baraldi P., Cadini F., “Basics of Reliability and Risk Analysis:
Worked Out Problems and Solutions”. World Scientific, Singapore, 2011
Piero Baraldi
58
Piero Baraldi
59
Piero Baraldi
60