Introductionto Risk Analysis
Unit 1
Introduction to Quantitative Process
Risk Analysis
1
Risk Analysis
Hazard vs. Risk
Some important Definitions-I
Safety: The freedom of injury, damage or loss of resources.
Hazard: The condition that can result in or contribute to a mishap. It is the
potential to cause harm, harm including ill health, injury or even fatality or
damage to the property, plant, product or the environment. Sometimes it may
lead to the production loss or increased liability.
Mishap: Mishap that is unintended event that can cause injuries, damage
or loss of resources.
Risk: Risk is the probability or a chance or occurrence of undesired event
and the severity of resulting consequences.
Risk analysis: Process of assessing, managing, and informing others about
existence, nature, magnitude,
probability, contributing factors, and
uncertainties of potential losses (or gains).
Some important Definitions-II
Risk Assessment: The process of Qualitative (analysis) risk categorization
or Quantitative risk estimation.
Qualitative: Descriptive( non-numerical data)
Quantitative: Numeric variables (e.g., how many; how much; or how often).
Risk Management: The process of risk identification, risk assessment, risk
disposition and risk tracking and control.
Probability: The chance or the likelihood of occurrence of an event or a
particular event.
Reliability: The probability that an item will perform its intended function
for a specified mission or profile, so reliability may be attributed to the
different safety devices, different process conditions etc.
Risk level:(size or magnitude) due to hazard exposure under known
conditions: both the probability (or frequency) of upset scenarios and the
outcome consequences are needed to estimate risk.
Some important Definitions-III
 Voluntary risks: A risk that result from hazards of activities people
choose to engage in.
 Examples: driving a car, riding a motorcycle, climbing a ladder, entering a
laboratory, skydiving, vehicle racing, hauling in a farm harvest …
[working in a plant?]
 Involuntary risks: Result from hazards of activities or events
without prior consent or choice of persons.
 Examples: Acts of nature such as lightning, fires, floods, tornados,
exposure to environmental contaminants
 For which of these two types of activities are people more willing to
tolerate risk or to accept a higher level of risk? Why?
.
Probability or Frequency
 Probability or likelihood A quantitative measure of the certainty or
uncertainty in the occurrence of a value, value range, event, or an event
sequence. Probability is defined as a number without units within [0,1].
 Frequency Number of occurrences of an event per unit time, often hour
or year, or per distance, area, or volume. Frequency of occurrence is used
also to estimate probability of occurrence within a particular time,
distance, area, or volume.
.
Hazard
 Not always identified until an accident occurs.
 Essential to identify the hazard and reduce the risk well in advance
of an accident, so that we can minimize the losses
 For each process in chemical plant, one must as the following
question and answer for all those questions.
1. What are the hazards?
2. What can go wrong?
3. What are the chances? (calculating the risk)
4. What are the consequences?
Categorizing the Hazard
There are two (diff) type of basic category of hazard.
1. Acute Hazards: Having an immediate and obvious impact that is
for example risk of falling or being wounded because of the
slippery or wet floor.
2. Chronic hazards: Having more hidden, cumulative or long-term
impacts. For example, workplace bullying where the long-term
impact result in the stress or other psychological injuries.
Grouping of the Hazard
Hazard generally fall into following six groups
1. Physical hazard: Slippery floor, object in the walkways, excessive noise, fire etc.
2. Chemical hazards: Gases, dust, fumes, vapors and liquid.
3. Ergonomic hazards: poor design of equipment, workstation design sometimes
postural or work floor problems, manual handling, repetitive movement.
4. Radiation hazard: Microwave, infrared, ultraviolet, laser, X-ray, gamma rays etc.
One may encounter these type of radioactive hazards. while characterizing the various
chemical samples
5. Psychological hazards: Shift work, stress, workload stress, dealing with the
public stress, harassment, threat of danger, discrimination etc.
6. Biological hazards: Presence of a bacteria, virus, fungi, parasites, through a cut,
insect bite, or a contact with infected person or contaminated object.
Hazard consequences
Adverse Consequence
Human Impacts
Environmental Impacts
Economic Impacts
Consumer Injuries
Off-site contamination
(Air, Water, Soil)
Property damage
Community Injuries
On-site contamination
(Air, Water, Soil)
Inventory loss
Onsite personal injuries
Production outage
Unit personnel injuries
Loss market share
Lost of employments
Legal Liabilities
Psychological Effects
Negative Image
Examples of Hazard and their impact
Hazard Identification and Control policy
 Systematic process hazard identification
 Systematic control policy.
1.
Provide a procedure that is reasonable, practicable, integrates different type of
identification, reporting and investigation of foreseeable hazard related to the work
activities and in consideration with the workers, the timely elimination or minimization
of risk to health and safety using the hierarchy of risk control.
2.
Ensure a presence of a formal process of hazard identification and risk assessment
which will effectively manage the hazard that occur within the workplace.
Hazard Identification Protocol
 Hazard identification and risk assessment are sometimes combined into a
general category that is called the hazard evaluation.
 Risk assessment is sometimes called the hazard analysis.
1.
Risk assessment procedure that determines the probability which is frequently called
the Probabilistic Risk Assessment (PRA).
2.
The procedure that determines the probability and consequences is called the
Quantitative Risk Analysis(QRA).
1.
Hazard identification can be performed independent of Risk Assessment. So, these two
things are altogether independent.
What is Risk Assessment
 Risk assessment that is the process of quantifying the probability of harmful effect
to individual from a certain human activities
 It includes the Incident identification and Consequence Analysis
 Incident identification this describes how an incident occurs; it frequently includes
an analysis of various kind of probabilities. So, enlist all kind of probabilities that
may happen
 Consequence Analysis, this describes the expected damage, this includes the loss
of life, damage to the environment or the capital investment or the capital
equipment and the days outage
Give an example of a risk-free activity.
Why Risk Assessment?
 Protect our self
 Because the risk assessment is the key to prevention of accident
 Elevate safety aware ness and ownership
 Aware about the various kind of hazards, risk and control and practicing safe science
 Compliance with regulatory bodies
Because “Risk” is the combination of likelihood of an occurrence of a hazard event or
exposure and the severity of injury or ill health or fatality that may be caused by the event or
exposure. So, life of workers, protection of environment (other human beings) and reduction
in economic loss
Risk Concept
What can go wrong?
How likely is it?
What are the impacts?
Risk Level
Manage Risk
Risk management includes the control and monitoring of acceptable risk as
well as the communicating the risk to the nearby people or those who may
get affected with that risk.
5-steps for risk assessment
The 5-steps
1.
Identify the Hazards
2.
Identify who might be harmed
3.
Evaluate the Risks
4.
Records the Findings
5.
Review the assessments
Probabilistic Risk Assessment (PRA).
 Rigorous technical discipline, that has been used in the countless complex
technological applications such as airline industry or nuclear power plant
to reveal design, operation and maintenance aspect, to enhance the safety
and reduce the cost
 Risk in PRA is feasible detrimental outcome of an activity or action.
 Risk is characterized by two quantities
1. Magnitude (severity) of the possible adverse consequences
2. Likelihood (probability) of occurrence of each consequences.
Quantitative Risk Analysis (QRA)
 Formal and systematic approach to estimate the likelihood and
consequences of the harmful procedures and expressing the results
quantitatively as to risk to people, environment or in business
 Assesses the robustness and validity of quantitative results by identifying
critical assumptions and risk driving elements.
 Studies are typically required for the construction and processing
facilities, high pressure pipelines and storage facilities at important sites
including LPG, LNG, etc.
 Contributes to improved decision making by highlighting the accident
scenarios that contributes most to overall risk.
Objective of Quantitative Risk Analysis
 Identify the hazard associated with facility
 Determine the potential frequencies and consequences of the identified
hazard.
 Determine the system availability of the protection system
 Quantify the risk associated with a facility( e.g Risk Contours, Individual
Risk per annum, potential loss of life (PLL) and F-N curve.)
 Suggest the recommendation to reduce the risk to human life, assets,
environment or business interruptions to as low as reasonably practicable


Risk Contours : Lines that connect points of equal risk around the facility ("isorisk" lines).
F-N curve: A plot of cumulative frequency versus consequences (often expressed as number of fatalities).
Risk Levels
• Risk assessment and management is an approach to
achieve a cost effective balance between a risk level and a
return level, which includes direct/indirect
costs,
performance, profits, good will, reputation,…
• A risk level that is acceptable or tolerable to one person,
organization, or community, may not be acceptable to
another person, organization, or community.
[Why?]
10
If Risk Cannot Be Reduced to Zero,
What Should be Our Target?
Risk Analysis Models
 Models to represent engineering systems:
• Deterministic → predict exact or unique
result (with specific uncertainty), e.g., what
caused a component or system to fail.
• Probabilistic → predict output range
probabilities
of variables or system
behavior to estimate uncertain events that
could result in losses
16
Areas of Risk Applications
Risk Analysis
Category
To Estimate
Health
Disease and loss of life
Safety
Harm due to natural events, fabricated
products, technologies, systems
Security
Harm due to war, terrorism,
riot, crime, misinformation
Financial
Individual, institutional, and societal
monetary losses and gains
Legal
Probability of innocence or guilt beyond
reasonable doubt
Environmental
Losses due to noise, contamination, and
pollution in ecosystems
17
Risk Applications, Examples
• Patient risk of anesthesia or medicines
• Seismic risk analysis and mitigation to affect
building codes and strategies
• Inspection and monitoring of critical
infrastructure, e.g., major bridges
• Monitoring and maintenance schedules of
chemical processes and plants as part of
industrial risk management
18
Engineering Risk Analysis Methods and
Decisions During Life Cycle of a System
Conceptual design
Design
Development
Regulation (Risk
Management)
Operation (Risk
Management)
Decommissioning
Decisions about alternative design options
Decisions to prevent, reduce or eliminate hazards
minimize life-cycle cost, maximize performance
Identify & test systems that contribute most to risk,
quality assurance, warranty development
Decisions concerning system elements that
contribute most to risk, set monitoring and
performance criteria, perform inspections
Decisions to optimize cost of operation, tests,
and maintenance, define surveillance
requirements, schedules, replacement policies &
decisions, aging estimation & management,
security measures
Decisions for safe decommissioning alternatives,
19
select disposal methods, assess long term liability
Consider the following Design Approaches, Which LifeCycle Stage Do They Belong To?
1.
2.
3.
4.
Inherently Safer Design
Circular Economy
HAZOP
Value Engineering
Elements of Risk Analysis
Risk
Management
Risk
Assessment
Decision
Making
Estimation of
probabilities and
consequences
Risk
Communication
Exchange, share, discuss the risk
and consequence analysis & decisions
Evaluation,
minimization,
and control of
risk within
acceptable limits
22
(adapted from Modarres, RAE)
Risk Assessment
Questions of risk assessment:
1. What can go wrong?— Identify and
characterize hazards, develop scenarios from
initiation to outcome events due to the hazards
2. How likely? — Estimate probabilities of scenario
events including barriers, and scenario outcome
events
3. What are the consequences? — Estimate
magnitudes of scenario
outcome events.
23
Types of Risk Assessment
• Quantitative Risk Assessment: Calculate risk in form of a
numerical probability (or frequency) of an event and the outcome
consequence magnitude. Generally needed for most critical parts
of a system.
• Semi-quantitative RA: Use order of magnitude for
frequency and for outcome magnitude for non-critical parts
of a system.
• Qualitative RA: Use of linguistic or ordinal scales (e.g., low,
medium, high; 1, 2, 3) for probability or the outcome magnitude.
Often used for screening, but to be useful, the linguistic or
ordinal scale ranges must be defined
25
Hazards and Scenarios
• To assess risk, hazards must first be identified
and characterized.
• Scenario development: Events, event conditions, and event sequences
leading to potential loss outcomes involving the hazards must be
identified.
26
Methodology of Risk Assessment-I
Scenario development with estimation of probability and
consequence of each credible scenario.
1. What can go wrong?
1.Identify hazards: with a nature to cause losses
(chemical, biological, thermal, mechanical, electrical,
radiation).
2.Identify system barriers. Each hazard is
analyzed to select barriers to prevent or mitigate
exposure to the hazard.
3. Identify challenges to barriers.
Each barrier
must be tested, monitored, and serviced to maintain its
function and respond to system demands.
27
3. Consequences?
2. How likely?
Methodology of Risk Assessment-II
4. Frequency or probability. Scenarios that pose
similar hazard exposure can be
represent outcome occurrence
categories
grouped to
frequency
5. Consequence evaluation. Losses are estimated
and modeled using knowledge and history of the
hazard behavior and amount of exposure.
Note that this 5-item risk assessment approach is another28 expression of the 3-item approach.
Risk Management (RM)
Decision making activities to reduce loss event probability,
and minimize consequences due to risk exposures, selecting
actions based on assessed risk values, economic and
technology constraints, and legal and political issues.
Techniques, methods:
Focus Areas:
• Inherently safer
design, technology
• Minimize hazards
• Cost-benefit analysis
• Prioritize risks levels
• Risk effectiveness
• Predictive failure
analysis (reliability)
• Decision Analysis
• Assess the performance
• Strategies to analyze,
minimize, control risks
• Assess effectiveness
and revise strategies
29
Quantitative Risk Assessment (QRA)
Risk = F(s, c, f)
s = hypothetical scenario
c = estimated consequence(s)
f = estimated frequency
 This ‘‘function” can be extremely complex and there can be many numerically different
risk measures (using different risk functions) calculated from a given set of s, c,f.
 Acute, rather than chronic, hazards are the principal concern of QRA.
 Chronic effects such as cancer or other latent health problems are not normally
considered in CPQRA
 Remember the difference between Incident and incident outcome.
 A single incident can have many outcomes.
 Leak of flammable and toxic gas could cause
 A jet fire
 A vapor cloud explosion
 A vapor cloud fire
 A toxic cloud
Quantitative Risk Assessment (QRA)
 QRA provides a tool for the engineer or manager to quantify risk and analyze
potential risk reduction strategies. Risk reduction measures can be applied to the
major hazard contributors and assessed using cost-benefit methods.
 Quantitative approach for safety is not new to chemical process industries.
 For every process, the kinetics of the chemical reaction, the heat and mass
transfers, the corrosion rates, the fluid dynamics, the structural strength of vessels,
pipes and other equipment as well as other similar items are determined
quantitatively by experiment or calculation, drawing on a vast body of experience.
Incident
• Incident
• Incident outcome
• Incident outcome case
Chemical Process Quantitative Risk Analysis (CPQRA)
Use of vapor dispersion model, fire and explosion model
Fault trees and Event trees
Impacts on people, environment and property
Potential consequences with frequency of event
Identify the major sources of risk and determine if there are
cost-effective process or plant modifications which can be
implemented to reduce risk.
Identify and prioritize potential risk reduction measures if the risk is excessive
Chemical Process
Quantitative Risk
Assessment
(CPQRA)
• The full logic of a CPQRA involves the
following component techniques:
• 1. Definition
• 2. System Description
• 3. Hazard Identification
• 4. Incident Enumeration
• 5. Incident Selection
• 6. Model Construction
• 7. Consequence Estimation
• 8. Likelihood Estimation
• 9. Risk Estimation
• 10. Utilization of Risk Estimates
Complete CPQRA Procedure
• Definition: Converts user requirements into study goals ( Table 1.4) (
originates from external sources such a regulatory bodies or form internal
initiative (senior management) and objectives.
• User requirement: Standards, economic criteria, Risk targets etc.
• Objectives could be:
• Determination of societal risk from company operations that include any of a
specified list of chemicals.
• Determination of risk to employees from modification to an existing process unit
• Identification of cost-effective risk reduction measures for achieving target risk
level of an existing process unit.
• Evaluation and ranking of competitive process strategies considering impact to
surrounding community
• Determination of relative effectiveness of each of several alternatives to reduce
risk from a single piece of equipment.
• Depth of Study
Complete CPQRA Procedure
A careful determination of the depth of study is essential if CPQRA goals and objectives
are to be achieved, adequate resources are to be assigned, and budget and schedules are
to be controlled.