Embed Size (px)
Citation preview
Introduction to Risk Analysis and Management
IST
C. Guedes Soares and Ângelo Teixeira
Risk Analysis 2
Introduction
Any plant or system should be designed and operated in such a way asto satisfy a given set of safety goals.
This is a goal-oriented approach where goals are first specified, and thenthe plant is designed, constructed, operated and maintained accordingly.
Risk Analysis 3
Introduction
Risk Analysis 4
Accidents do happen
Risk Analysis 5
Introduction
Disasters and accidents have always occurred
Engineers make decisions in regard to activities associated withUncertainties:
Models are not preciseData are not sufficientNatural variabilityExperience is subjective
How to deal with uncertainties?
How safe is safe enough?
risk-based decision makingrisk-informed integrated decision making
Risk Analysis 6
What is uncertainty?
Definitions
“a general concept that reflects the lack of sureness about something, ranging from just a sort of complete sureness to an almost complete lack of conviction about an outcome” (Sayers et al., 2002)
http://www.floodrisknet.org.uk/glossary/uncertainty
“a situation in which an individual has incomplete information as to what is going to happen in the future
http://www.worldbank.org/hsr/class/module1/glossary.htm
Risk Analysis 7
What is uncertainty?
Definitions (cont.)
A potential deficiency in any phase or activity of the modeling process that is due to the lack of knowledge." (AIAA G-077-1998)
www.grc.nasa.gov/WWW/wind/valid/tutorial/glossary.html
Uncertainty is an inevitable part of the assertion of knowledge: see Bayesian probability.
www.en.wikipedia.org/wiki/Uncertainty
Risk Analysis 8
What is uncertainty?
Definitions (cont.)
“Uncertainty is that which disappears when we become certain”
“In practical scientific and engineering contexts, certainty is achieved through observations, and uncertainty is that which is removed by observations. Hence uncertainty is concerned with results of possible observations”
T. Bedford & R. Cooke (2001)
Risk Analysis 9
Types of uncertainties
Aleatory (or stochastic) uncertaintyVariability due to the nature of physical phenomena
Epistemic (or knowledge-based) uncertainty• uncertainty due to inadequate knowledge (model uncertainty)• statistical uncertainty (sparse information).
The knowledge-based uncertainty can be reduced by further study.The aleatory uncertainty, on the other hand, is by definition irreducible.
The variables and the parameters used in design and analysis are subjected either to:
Risk Analysis 10
Epistemic (or knowledge-based) uncertainty
Statistical uncertainty
The statistical uncertainties are associated with the statistical evaluation of results of tests or observations. They may result from:
Model uncertainty
arises from the fact that any model, conceptual or mathematical, willinevitably be a simplification of the reality it is designed to represent
• a limited number of observations or test results which cause uncertainties in the estimation of statistical parameters, e.g. mean and standard deviation,
• neglecting systematic variations of the observed variables e.g. of climate variables,
• neglecting possible correlations.
Risk Analysis 11
What is uncertainty?
Probability theory
Express uncertainty in terms of probability
Provides the basis for the assessment of numerical measures of the likelihood of the occurrence of uncertain events
Risk Analysis Reliability Analysis
Decision Analysis
(probabilities)
Risk Analysis 12
Bayesian or subjective interpretation
The probability assigned to A depends on the present knowledge about the occurrence of A, which can be updated by further knowledge.
degree of belief ≠ degree of truth
A of occurence in the ,individualon of belief, of degree)( AP
The subjective interpretation of probability is widely applied in risk analysis
Based on this interpretation the probability P(A) of the event A is formulated as a degree of belief that A will occur:
Risk Analysis 13
Risk and Safety in Engineering
Risk assessment, within the framework of decision analysis, providesa basis for rational decision making subject to uncertain and / orincomplete information
Thereby we can take into account, in a consistent manner, the prevailinguncertainties and quantify their effect on risks
Thus we may find answers to the following questions:
- How large is the risk associated with a given activity ?- How may we reduce and / or mitigate risks ?- How much does it cost to reduce and / or mitigate risks ?- What risks must we accept – what can we afford ?
Risk Analysis 14
Risk analysis is defined as a systematic approach to the identification,analysis and evaluation of factors that may lead to accidents. (It alsofrequently includes the generation of proposals for increasing levels ofsafety).
The main objective of a risk analysis is to achieve a risk level reduction.
Main components of a Risk assessment are
• Risk identification ;
• Risk analysis;
• Risk evaluation:
Risk assessment
Risk Analysis 15
Definition of Risk
Risk is a characteristic of an activity relating to all possible events nE
which may follow as a result of the activity
The risk contribution RiskEi from the event Ei is defined through the productbetween
- the Event probability PEi
- the Consequences of the event CEi
The Risk associated with a given activity RA may then be written as
EventCosteConsequenc
TimeEEventobability
TimeCostRisk i
Ei Pr
(The risk is an expected cost per unit time)
Ei
n
iA RiskR
Ei
1
Risk Analysis 16
Individual risk (fatality risk in occupational accidents in Portugal per year)
Since there are in average 250 fatalities in occupational accidents per year in Portugal in a population of 10 million
yearpersonfatality
personyear
.105.2
1010/accident aloccupation infatality 250 5
6
Example 1:
Risk Analysis 17
-90 000 road accidents per year in Portugal,
- In average 450 million Euros are spent in human and material damages
- 1 million cars circulating in Portugal
Annual frequency of accidentyearcar
accidentcar
yearaccident
09.0101
/000906
Consequence of a car accidentaccidentEuro
accidentEuro 5000
0009010450 6
yearcarEuro
accidentEuro
yearcaraccidentRisk
450500009.0
Example 2:
Risk Analysis 18
-250 000 occupational accidents in Portugal per year,
- 300 million Euros are spent annually in occupational accidents in Portugal per year
- Workforce: 4,6 million people
yearaccidentyearaccident
.worker0.054
Worker106.4/000250
6
accidentEuro
accidentEuro 1200
00025010300 6
yearEuro
accidentEuro
yearaccidentRisk
.worker651200
.worker054.0
Example 3:
Annual frequency of accident
Consequence of an accident
Risk Analysis 19 Risk Analysis 20
Types of Risk in Public Activities
Individual Risks: Risks that affect individuals such as death, disabilities,deficiences and illness
Social Risks : Risks that affect groups of persons that live in a region orhave any common activity such as work or transportation.
Environmental Risks : Risks that are reflected in damages to the environment
Different types of risks have different type of acceptance criteria
Risk Analysis 21
Public Perception of Risk
Potencial for catastrophes
Risk for future generations,
Familiarity with the risk
Potencial for irreversible effects
Lack of personal control
Local cultural values
Public Perception of Risk reflects the attitute of the general public towards acceptance of different kind of risks
Public Perception of Risk often does not coincide with the real risk levels
Public Perception of Risk depends on
Risk Analysis 22
Risk description
Risk depends on the probability of occurrence of an accidental event and of its consequences
Risk depends on time as both probability and consequences can depend on time. Therefore it is specified with reference to a specific period of time
When consequences are losses of live risk is often substituted by the probability of loss of live or when they are multiple, by the expected number of lives lost
Risk acceptance levels are required for decision making
Risks can be described at different level of detail
Risk Analysis 23
Examples of Different risk Levels
Risk of death in Portugal, 1994
Risk of death due to all causes and external causes(Source: Direcção Geral da Saúde, Estatísticas de mortalidade).
0
0,002
0,004
0,006
0,008
0,01
0,012
HM H M
Sex
Risk
of D
eath
All causesExternal causes
Risk Analysis 24
Individual risk of deathUK 1980-84.
(Source: Fernandes - Russel, 1987a) Population at risk: all population of UK
Individual Risk / year
(all ages) All causes 10-2 All internal causes 10-2 All external causes (accidents, violence, poisoning...)
10-4
All accidents 10-4 All industrial accidents 10-5
Individual Risk
Risk Analysis 25
Main causes of death in Portugal, 1995 (Source: INE)
A – AVC occurrencesB - TumorsC – Heart deseasesD – Ill defined symtoms E - AccidentsF - Other causes of death
22.6
19.3
16.5
11.4
6.1
17
0
5
10
15
20
25
A B D D E F
Causes of death
% o
f dea
ths
Risk Analysis 26
Comparing individual risk of death due to internal and external causesUK1980-84. (Source: Fernandes - Russel, 1987a)
Individual risk / year INTERNAL CAUSES Boold circulation system 5800 x10-6 Neoplasms 2700 x10-6 Breathing system 1600 x10-6 Digestion system 300 x10-6 EXTERNAL CAUSAS Accidents in motor vehicle 100 x10-6 Acidental falls 90 x10-6 Suicides 90 x10-6
Individual Risk
Risk Analysis 27
Comparing individual risk of death due to selected causesUK1980-84. (Source: Fernandes - Russel, 1987a)
Individual risk / year Lightnings 0.1 x10-6 Medical accidents 0.9 x10-6 Air transportation 1.2 x10-6 Accidental poisoning 13.1 x10-6 Accidents in motor vehicles 101.0 x10-6
Individual Risk
Risk Analysis 28
Work accidents in Portugal (1990-2000)
Nº Total de Acidentes de Trabalho 1989-2000
0
50000
100000
150000
200000
250000
300000
350000
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
Ano
Nº T
otal
de
Aci
dent
es
0
0,01
0,02
0,03
0,04
0,05
0,06
0,07
Frequência
Nº Total de Acidentes de Trabalho Frequência
Risk Analysis 29
Deadly work acidents in Portugal
Nº Total de Acidentes Mortais de Trabalho (1989-2000)
0
50
100
150
200
250
300
350
400
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
Ano
Nº T
otal
de
Aci
dent
es
Mor
tais
de
Trab
alho
0,0E+001,0E-052,0E-053,0E-054,0E-055,0E-056,0E-057,0E-058,0E-059,0E-05
Frequência
Nº Total de Acidentes Mortais Frequência
Risk Analysis 30
Deadly work acidents in Portugal by activity (2000)
Actividades: Acidentes de Trabalho Mortais
Número Total Agricultura/Pecuária 18
Silv./Explor./Flor. 4 Pesca 5
Extr. Min. Não Metálicos 5 Indústria Alim./Beb./Tabaco 10
Indústria Têxtil 2 Indústria Vestuário/Confecção 1
Indústria Calçado 1 Indústria Madeiras/Cortiça 8
Indústria Papel 4 Indústria Química 6
Indústria Por./Olaria/Vidro 2 Indústria Cerâmica 13
Indústria Metalúrgica de Base 3 Indústria Prod. Met. Mat. Eléctr. 7
Outras Ind. Transformadoras 3 Electricidade/Gás/Água 3
Construção Civil 132 Com. Rep. Auto 1
Com. Grosso 9 Com. Retalho 5
Indústria Hoteleira 2 Transp./Armazenagem 15
Comunicações 5 Bancos 3
Serviços Prestados Empresas 12 Serviços Sociais 4
Serviços Saneamento/Limpeza 2 Serviços Recreat./Culturais 2
TOTAIS 287
Risk Analysis 31
Deadly work acidents in Portugal by activity (2000)
Indústrias Transformadoras
38%
Construcção23%
Com. Gr/Ret. Rep V. Auto Moto
14%
Agricutura, Silvicultura e Pesca
3%
Transportes, rmazenagem e
Comunicações4%
Outras6%
Outros Serv. Coilectividade, Sociais
e Pessoais2%
Alojamento e Restauração
4%
Adm. Publ. Defesa e Seg. Social
2%
Activ. Imob. Alug. Serv. Pr. Emp.
4%
Risk Analysis 32
Frequency of Fatal Accidents in Coal minesUK 1949-1987
Individual Risk
Risk Analysis 33
Deadly work accidents in selected industriesUK1980-84. (Source: Fernandes - Russel, 1987a)
Population at risk: Total employees in each industry
Individual risk / year Professional services 1 x10-6 Electrical engineering 6 x10-6 Paper industry 11 x10-6 Chemical industry 19 x10-6 Transportation 33 x10-6 Metalurgical industry 76 x10-6 Building industry 102 x10-6 Minning industry 179 x10-6 Quarry industry 390 x10-6 Deep sea fishing 880 x10-6 Average all industries 22 x10-6
Individual Risk
Risk Analysis 34
a. Sleeping time b. At home washing, dressing...c. Driving to workd. Daily working timee. Lunch breakf. Using motorcycleg. Hobbies
Daily risk
Risk Analysis 35
Frequency of road accidents compared with accidents in Chemical and Petrochemical Industries in UK
Road Accidents Nº of accidents with x deaths
Accidents in Chemical and Petrochemical Industries
Year
1 2 3 4+ 1 2 3 4 15 1981 4969 306 61 19 1 0 0 0 0 1982 5056 320 54 17 1 1 0 0 0 1983 4691 278 39 19 3 1 0 1 0 1984 4789 274 51 24 2 2 1 0 1 1985 4456 261 33 18 2 1 0 0 0
Individual and Social Risk
Risk Analysis 36
Social Risk (F-N Curves)
1967-2001
Risk Analysis 37
Social Risk (F-N Curves)
Risk Analysis 38
Social Risk (F-N Curves)
Risk Analysis 39
Definição de RiscoRisk Acceptance (Qualitative) Example
Risk Analysis 40
Risk Acceptance (Qualitative) Example
Risk matrix (ex: BS 8800:2004)
Con
sequ
ence
1
2
3
4
5
1 2 3 4 5
Acceptable
Not acceptable
Likelihood / Frequency
Risk Analysis 41
A – Car accident
Freq. = 4, Cons. = 3
B – Aviation accident
Freq. = 1, Cons. = 5
A
B
Risk Acceptance (Qualitative) Example
Con
sequ
ence
1
2
3
4
5
1 2 3 4 5
Not acceptable
Likelihood / Frequency
Acceptable
Risk Analysis 42
Risk Analysis 43
Risk Management Process
Risk management process involves applying logical and systematic methods for:
- identifying, analyzing, evaluating and treating risk associated with any activity, process, function, project, product, service or asset;
- monitoring and reviewing risk
Risk Analysis 44
select one or more options for modifying risks, and implementing those options.
Risk identification
Risk Analysis
Is the risk level
tolerable?
Risk treatment
No
Yesmaintaining existing risk controls
Risk evaluation
Risk Management Process
Define likelihoods and consequences(qualitative, semi-quantitative or quantitative)
Risk Analysis 45
Risk Management Process (ISO 31000)
Risk Analysis 46
Risk assessment is the overall process of:risk identification, risk analysis and risk evaluation.
Risk assessment
identifying sources of risk, areas of impacts, events and their causes and their potential consequences
The aim of this step is to generate a comprehensive list of risks
Risk identification tools and techniques which are suited to its objectives and capabilities, and to the risks faced should be applied
Risk identification
Risk Analysis 47
Risk assessment
Risk analysis is about developing an understanding of the risk
Risk analysis involves consideration of the causes and sources of risk, their positive and negative consequences, and the likelihood that those consequences can occur.
Risk analysis can be undertaken with varying degrees of detail depending on the risk, the purpose of the analysis, and the information, data and resources available.
Analysis can be qualitative, semi-quantitative or quantitative, or a combination of these, depending on the circumstances.
In practice, qualitative analysis is often used first to obtain a general indication of the level of risk and to reveal the major risks.
When possible and appropriate, one should undertake more specific and quantitative analysis of the risks as a following step.
Risk Analysis
Risk Analysis 48
Risk assessment
The purpose of risk evaluation is to assist in making decisions, based on the outcomes of risk analysis, about which risks need treatment to prioritize treatment implementation.
Risk evaluation involves comparing the level of risk found during the analysis process with risk criteria established when the context was considered.
If the level of risk does not meet risk criteria, the risk should be treated.
In some circumstances, the risk evaluation can lead to a decision to undertake further analysis.
The risk evaluation can also lead to a decision not to treat the risk in any way other than maintaining existing risk controls.
Risk evaluation
Risk Analysis 49
Risk treatment
Risk treatment involves selecting one or more options for modifying risks, and implementing those options.
Risk treatment involves a cyclical process of assessing a risk treatment; deciding whether residual risk levels are tolerable or not; if not tolerable generating a new risk treatment; and assessing the effect of that treatment until the residual risk reached complies with the organization’s risk criteria.
Risk treatment options can include the following:- avoiding the risk by deciding not to start or continue with the activity that gives rise to the risk;- seeking an opportunity by deciding to start or continue with an activity likely to create or enhance the risk;- removing the source of the risk;- changing the nature and magnitude of likelihood;- changing the consequences;- sharing the risk with another party or parties; and- retaining the risk by choice.
Risk Analysis 50
The risk analysis is applied to study proposed facilities and procedures thatcan create dangers or operation flaws. The situations where this type ofanalysis is more appropriate are:
• When the plan of the facility is being perform;
• When it begins to give a concrete form to safety's objectives;
• During the assessment and proposed measures;
• On final inspection;
• During the initial period of operation.
Risk analysis
Risk Analysis 51
An risk analysis can supply information to improve safety's conditions,considering variables as the total cost, materials, personnel and availableequipments, etc.
The risk analysis can be applied as support to decision, allowing theassessment of risks of alternative solutions.
Risk analysis
Risk Analysis 52
There are many different methods of risk analysis.
In general, it can be said that any one specific method will only cover alimited part of the risk panorama.
Analysis from a technical perspective,
Man-Machine interaction,
Analysis of the organization.
The methods are classified as follows:
Therefore, it is useful that a analysis doesn’t restrain herself to just onemethod.
Methods of Risk Analysis
Risk Analysis 53 Risk Analysis 54
