Risk Analysis - Prof Carpignano - Appunti di Fabio Galizia

Corso di laurea magistrale in Risk Analysis

Prof. Andrea Carpignano

Appunti di Fabio Galizia

Lezione 1

Introduction to Risk Analysis

Politecnico di Torino Dipartimento Energia

Safety and Risk Analysis

Andrea Carpignano
andrea.carpignano@polito.it

Francesco Ganci
francesco.ganci@polito.it

Anna Chiara Uggenti
anna.uggenti@polito.it

Introduction

The course is held for students in Energy Engineering.

Five lectures (including Monte Carlo) per week (1.5 hours each).

Rooms:

• Wednesday 13.00-16.00 Room 29
• Friday 10.00 - 13.00 Room 29
• Friday 16.00 – 17.30 Room 27

Ed. 2011/12

Rooms

Rooms 8.30 10.00 11.30 13.00 14.30 16.00 17.30

Schedule Sep 30 MC MC AR

Oct 5 MC MC
7 AR AR AR
12 MC MC
14 AR AR AR
19 MC MC
21 MC MC AR
26 AR AR AR
28 MC MC AR

Nov 2 MC MC
4 AR
9 AR
11 AR AR AR
16 MC MC
18 AR AR AR
23 MC MC
25 AR AR AR
30 MC MC

Dec 2 AR AR AR
7 MC MC
14 MC MC
16 MC MC AR
21 MC MC

Jan 11 MC MC
13 AR AR AR
18 MC MC
20 AR AR AR

White cells means lectures (MC Monte Carlo, AR Risk Analysis).

Yellow cells are exercises split into 2 groups (Room 27 and Aula Capetti).

Rules for the exam

Rules for Safety and Risk Analysis exam must be downloaded from the didactic portal.

Please read them carefully!

Ed. 2011/12

Introduction to the course

Practical Lectures are held by Francesco Ganci and Chiara Uggenti.

Lecture notes will be at disposal of the students on the “Portale della didattica”, the Polito web site for the students.

I will give you also some references for books, papers that can help you to deepen some specific topics or to use them in your future working activity (most of them are available in the POLITO Library).

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Goals

General goal: Students are required to join their skills in different topics (gained in previous courses) to face an engineering project, by a professional approach.

• Clarify concepts & definitions
• Introduce to the risk based approach for the everyday life
• Provide methodologies and techniques for safety and risk assessment
• Provide sensibility versus regulations
• Address students to a professional approach to industrial safety by practical case study

Ed. 2011/12

Contents of the course

• Introduction to terminology
• The “Risk” concept
• Risk perception and acceptability
• Risk analyses methodologies (probabilistic and damage analyses)
• Reliability theory
• Fundamentals on consequence assessment (fires, explosions, gas dispersion, …)

Ed. 2009/10

Contents of the course

Safety and Risk Analysis

• Introduction to terminology
• The “Risk” concept
• Monte Carlo methods
• Risk perception and acceptability
• Risk analyses methodologies (probabilistic and damage analyses)
• Reliability theory
• Fundamentals on consequence assessment (fires, explosions, gas dispersion, …)

Localizzazione e Impatto Ambientale

Ed. 2009/10

Introduction to the “Risk” concept

What is safety? Damage free. Situation where you are.

What is risk? Distance to safe.

Is the risk to zero. We are not able to reduce.

Which is the relationship between Safety and Risk? The risk is the measure of our distance from fully safety.

Ed. 2011/12

Introduction to the “Risk” concept

What is safety? A condition characterised by the absence of possible damages (abstraction).

What is risk? A technical “measure” able to assess the distance from safety of a system/situation.

Which is the relationship between Safety and Risk? Risk can be seen as the distance from the “full” safety.

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Introduction to the “Risk” concept

Safety

Risk

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Introduction to the “Risk” concept

Which kind of damages we are interested in?

• Damage to people (deaths, injuries)
• Damage to environment
• Economical damage
• Direct damage (cost for asset recovery)
• Indirect damage (loss of production)
• Damage to reputation

Authorities

Company

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In the past the worst damage was related to damage to people. Now in the engineering the risk includes 4 types of damage:

• Damage to people
• Damage to environment
• Economical damage. Indirect, direct, amount of money have to spend to recover the damage, loss of production due to a damage causes the plant doesn't work for a time. Usually indirect >> direct: loss of production is more important compared to repair of component.
• Damage to reputation: social damage

The first 2 damages are the most important and are regulated by legislation.

R = f(scenario, probability, death)

R = frequency X damage expected

[event/year] [death/event]

Risk is the possibility that undesired and uncertain event occurs.

Our final results will be always affected by uncertainty.

Rtot = R1+R2+R3+...+Rn = f*d1+f*d2+...+fn*dn

The total risk is due to the sum of all the risk: (Sum of damage weighted by its probability occurs).

The estimation of the risk must be in a period of time and this is the difference between frequency and probability.

Introduction to the “Risk” concept

Definition of Risk

“The possibility that an undesired and uncertain event occurs”

R (deaths/y) = f (events/y) x d (deaths/event)

Road Accident: 240.000 acc/y * 1/40 (death/acc) = 6000 (deaths/y)

Ed. 2011/12

Introduction to the “Risk” concept

Different ways to interpret “Risk”:

• It is an estimation of damages, weighted by their probability of occurrence (R = Rtot + R1 + R2 + … = f1*d1 + f2*d2 + …)
• It is the social cost of an incident (technical failure, human error, natural event …)

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Introduction to the “Risk” concept

Social cost means: The cost paid by the community deriving from the introduction of a new technology.

2 kinds of social costs:

• Routinely cost: the cost in terms of daily environmental impact (e.g. air pollution, noise, …)
• Probabilistic cost: the cost deriving from potential accidents (loss of life due to an explosion)

Ed. 2011/12

Introduction to the “Risk” concept

Environmental Impact Assessment

A procedure aiming to obtain the authorisation to the construction and operation of a new installation in Europe.

It must deal with:

• Soil and underground impacts — EEC Directive 85/337
• Impact on water reserves, rivers, lakes, … — EC Directive 96/61
• Emissions to the atmosphere — EC Directive 97/11
• Noise and vibration
• Ionising and non ionising radiations
• Impact on the landscape
• Impact on public health (routinely and accidental)

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Plant authorisation processes

Major Accident installations

• Process safety (Safety Report + Fire prevention, DLgs. 105/15 (2012/18 UE), DLgs. 145/15 (30/2013 UE))
• Environmental Impact Assessment (DLgs 152/06)

Other installations

• Fire prevention (DPR 151/2011, DM 7/8/2012, DM 3/8/2015)
• Environmental Impact Assessment (not for all, includes risk analysis, DLgs 152/06)

In Italy (and EU) all the authorisation processes are split in two stages:

• For construction (NOF, VIA, Esame Progetto)
• For operations (PTC, AIA, CPI)

Other important regulations:

• Safety and Health for workers (DLgs 81/2008 - 1989/391 CE)
• Safety for Machinery (DLgs. 17/2010 2006/42 CE)

Legislation

Major Accident Installation: the damage to people and environment are outside the major plant. The amount is important to determine if it is or not.

Seveso Directive: Accident that moves the European community to have a specific legislation.

3º Seveso
DLgs 145/15 (30/2013 UE)

1º Seveso
DLgs 105/15 (2012/18 UE)

On shore, off shore.

1º Seveso was for the 2º for.

• Preliminary design of plant and parallel perform the risk analysis to verify the design.
• Authorization of plant/project by authority (NOF Nulla Osta di Fattibilità, VIA Valutazione Impatto Ambientale, Esame progetto) for construction, (PCT Parere Tecnico Costruttivo, CPI Certificato Prevenzione Incendi, AIA) for operator.
• Safety for machinery (marchio E cerchiato)

Introduction to the “Risk” concept

Type of Risk:

• Social / Individual
• Immediate / Delayed
• Voluntary / involuntary

Ed. 2011/12

Introduction to the “Risk” concept

Social/Individual

Immediate/Delayed

Voluntary/Involuntary

Introduction to the “Risk” concept

Attention please… the final risk figure is not so interesting, it could be affected by big uncertainties, it is a tool, not the truth…

Risk analysis aims to:

• Investigate a system in terms of failures and errors in order to increase its robustness.
• Reduce the frequency.
• Identify and suggest the preventive measures (design review, preventive maintenance, etc.) reducing the probability of occurrence.
• Reduce the damage.
• Identify and suggest the mitigation measures (design review of protection systems, land use planning, emergency planning, etc.).
• Compare different design solution in order to choose the safer one.

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Introduction to the “Risk” concept

Problems related to the Risk Assessment:

• Merging of several disciplines
• Complexity of the phenomena we must study
• Uncertainty of the estimations
• Need to cover all the operational configurations (risk depends on equipment, human, environment)
• Need to follow the system evolution (ageing, design review, etc.)
• Political and social implications

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Glossary

Risk (Rischio)

Probability/Frequency

Hazard (Pericolo)

Initiating Event or Initiator

Accidental Sequence

Consequence

Vulnerability

Damage

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Glossary

Risk (Rischio)

Probability/Frequency

Hazard (Pericolo): a situation of potential damage.

Initiating Event: the event able to “activate” the hazard.

Accidental Sequence: the sequence of events, staring from the initiating event, describing all the accident evolution.

Consequence: the physical effects of the accident.

Vulnerability: the capability of the context to transform the consequence in damage.

Damage: the final effects of an accident in terms of loss of lives, injuries, money, etc.

Ed. 2011/12

Security: is against the voluntary act.

Safety: is against unvoluntary act.

Hazard: is the physical situation that is able to produce damage. The risk is only the evaluation of the hazard. (Hazard = pericolo)

Before we have to list all the hazard and then the relative risk.

Vulnerability: capacity to transform the consequences to real damage.

Glossary

Safety: absence of any possible damage (an unreachable goal!).

Hazard: a situation that could be potentially dangerous (e.g. the presence of a storage of dangerous materials, high pressures, …).

Risk: possibility that a dangerous event occurs, i.e., possibility that the Hazard becomes Damage.

Consequence

Damage

Accidental Sequence (e.g. mg/m³)

Initiating Event

Hazard

Ed. 2011/12

Types of initiating events

• Technical failures (e.g. pipe break, valve stuck, pump failures, electronic malfunctioning, …)
• Operational/Maintenance errors
• Software errors (leading to a malfunctioning of the control system)
• External events (plane crashes on the plant, earthquakes, external fires, flooding, etc.)

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Accident evolutions & Safety Critical Barriers

• Technical failures (design, operations, maintenance, organisation)
• Human errors
• Software errors
• External events
• Damage

https://www.youtube.com/watch?v=SFGfRtfsp-w

Ed. 2011/12

Risk assessment

Approaches to Risk Assessment

Qualitative assessment

Probability Damage

1 - Not expected: …

2 - Rare: …

3 - Occasional: …

4 - Probable: …

1 - Negligible: …

2 - Light damage: …

3 - Major damage: …

4 - Catastrophic: …

4 8 12 16
3 6 9 12
2 4 6 8
1 2 3 4

F (ev./anno) D

The manager of company decides which is the too high risk and which is the acceptable risk.

Not quantitative assessment

Non accettabile

Acceptable

5.0 E-5

5.0 E-6 ALARA Statistical approach

Acceptable

Accettabile

5.0 E-7 1 10 100 D (morti)

Analytical approach (When there are no statistic elements to discuss).

Ed. 2011/12

Risk perception

People feel the risk in this way:

DR = F x

• They have an high perception of damage
• They don’t take into particular account the frequency of occurrence… some people are afraid to take the plane but drive every day their car…

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Risk perception

USA interview

Results of the interview

Real number of deaths per year

Cancer

Heart diseases

Flooding

Tornados

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Risk perception

To respect people perception we could use the following relationship for risk:

R = F x D^k

With k>1

The Nederland uses K=2!

The value of K is a socio-political matter, not a technical point!

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Risk tolerability

Which is the acceptable/tolerable level of Risk? R<Rmax?

Rmax

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Individual risk tolerability

Individual risk

Causes (deaths/y*person)

All causes

Cancer

Accident

Individual risk

Type of accident deaths (deaths/y*person)

• Car accident
• Falls
• Fires
• Drowning
• Poison
• Weapon
• Machines
• Naval transport
• Airplane
• Dropping objects
• Electric shock
• Rail transport

Ed. 2011/12

Social risk tolerability

Rischio

Risk

Social Risk R1

F (ev./anno)

F (ev./y) R2

5.0 E-5 €C1 C2 €

Non accettabile

Unacceptable

5.0 E-6 ALARA

Acceptable

5.0 E-7 1 10 100 D (morti)

D (deaths)

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Social risk tolerability

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Overall risk assessment

Natural risks

• Hydro-geological (land slips, flooding, …)
• Forest fire
• Exceptional meteo events (hurricanes, tornados)
• Snow (snow slips)
• Seismic (earthquakes)

Technological/Antropic risks

• Transportation
• Industrial Risk
• Health Risk (virus, bacteria)
• Nuclear Risk

Ed. 2011/12

Risk and legislation

In Italy:

In the past, the technical laws were prescriptive (e.g. road code: the max speed is 50 km/h).

The new technical regulation, based on EU Directives, is “goal setting” or “performance based” (prestazionale) (i.e. based on the risk analysis).

At the moment we have in EU good performance rules for industry while transportation is still based, mainly, on prescriptive rules (some exception, for instance the new regulation for the risk analysis of tunnels).

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On shore: 105 Directive Seveso/2015.

Off shore: 145/2015.

Perspective rule: set of rules that must be followed; the legislation has decided the good approach for safety.

Starting from '20 there was changing in legislation; there is no precise rule but the organization can decide the rules of safety with “goal based rule” prestazionali) (leggi within the risk analysis.

This is the situation for industry. For transport is different because is not local problem.

Must be agreed the uniform change.

The evolution of legislation in transport is very low, in fact.

ADR License: International agreement and gives the rules for transportation (rules for construction of truck and for the hours to transport: night or day).

RID: for trains.

IMO/SOLAS: maritime transportation.

ICAO: planes transportation.

Fire prevention: is still prescriptive rule but there are some changing to goal based within risk analysis.

Molte volte non si possono seguire le regole (museo con dipinti importanti alle pareti e non si possono aprire uscite di emergenza) tramite risk analysis si può garantire e dimostrare la sicurezza pur non seguendo le direttive.

Fire fighting: is not to shutdown the fire but to cool the surround to avoid the propagation.

Foam: Useful if we have liquid that is flammable, to separate the vapor fase from liquid fase.

Other way to fire fighting: We remove the air and insert CO2. The fire is shutdowned; it must be done if there is no people inside (there is usually a door protection).

Risk and legislation

Aims of the main rules

• To check and guarantee the safety and health in work environment (89/391 EC, …, 2004/40 EC, DLgs 81/2008).
• To check the safety for the community in Major Hazard Installations: Refineries, Chemical plants, (2012/18 EU, DLgs 105/2015 “Seveso Directive”) Nuclear plants, Oil&gas plants (2013/30 EC, DLgs 145/2015).

Ed. 2011/12

Risk and legislation

In transportation…

• To check and guarantee the safety still for the transportation of people (prescriptive rules).
• To check and guarantee the safety for the transportation of dangerous goods (flammable, explosive, toxic substances …) (2004/54 EC for road tunnels, DLgs 2006/264).

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Risk and legislation

In fire fighting…

• To design “ad hoc” fire emergency systems where the regulation is not prescriptive applicable (e.g. historical buildings) (DPR 151/2011, DM 9/5/07).
• During the machinery design and construction: Risk analysis to identify the residual risk and to prepare the technical documentation for the commercialisation of the machine (2006/42 CE - DLgs. 17/2010).

Ed. 2011