SEVESO SAFETY REPORT Guide Linesenserenergy.com/pdf1/dok-4.pdf · SEVESO SAFETY REPORT Guide Lines RISK ANALYSIS AND ASSESSMENT Page 4 / 13 Seveso Safety Report Guideline - Risk Assessment

SRL

Vicolo Boni, 7 - 52044 Cortona (AR) - Tel. +39.0575.6383.11 - Fax +39.0575.6383.79 - www.icarocortona.it -

[email protected]

SEVESO SAFETY REPORT

Guide Lines

RISK ANALYSIS AND ASSESSMENT

Jan. 2015

File: Seveso Safety Report Guideline - Risk Assessment - 3

SEVESO SAFETY REPORT Guide Lines

RISK ANALYSIS AND

ASSESSMENT

Page 2 / 13 Seveso Safety Report Guideline - Risk Assessment .docx -

INDEX

GENERAL INFORMATION ON THE SITE .................................................................. 3

PROCESSES, TECHNOLOGIES, ORGANIZATION AND FACILITY DESCRIPTION ........ 3

DANGEROUS SUBSTANCES CLASSIFICATION AND INVENTORY ............................. 4

IDENTIFICATION OF EVENTS LEADING TO MAJOR ACCIDENTS ............................. 4

TOP EVENTS FREQUENCY ...................................................................................... 5

POSSIBLE SCENARIOS AND RELEVANT FREQUENCY .............................................. 6

SCENARIO EFFECTS ................................................................................................ 8

CONSEQUENCES ASSESSMENT ............................................................................. 8

DOMINO EFFECTS ................................................................................................. 9

RISK ASSESSMENT ............................................................................................... 10

DEFINITIONS ........................................................................................................ 11

REFERENCED BIBLIOGRAPHY AND SOURCES ...................................................... 12


RISK ANALYSIS AND

ASSESSMENT


GENERAL INFORMATION ON THE SITE

The Safety Report will be introduced by a detailed description of the terminal, including among

others:

• Environmental description of surrounding

• Geological and hydrographic information

• General description of the facility under analysis.

The information will be supported by graphical representation (general chorography of the

area in a suitable scale).

PROCESSES, TECHNOLOGIES, ORGANIZATION AND FACILITY DESCRIPTION

Detailed description of

the facility’s general description and history;

the processes utilized in the facility (establishment) under analysis;

the technologies adopted;

the organization of the facility (daily and on-shift personnel).

The description will be joined to drawings and schemes illustrating the specific subject (PFDs,

lay-outs, organization schemes and so on).

Example of PFD scheme


RISK ANALYSIS AND

ASSESSMENT


DANGEROUS SUBSTANCES CLASSIFICATION AND INVENTORY

A deep analysis will be carried out of all substances present and processed in the

Establishment, with their classification according to the Manufactory Safety Data Sheets

(MSDS) and the identification of those falling under the Attachment 1 to Seveso Directives as

implemented in Turkish laws and regulations. The analysis will avail of a proprietary software

developed di ICARO for this purpose.

Computation of the maximum inventory of Seveso’s dangerous substances, will be based on

the maximum hold up in the process and storage areas, including larger pipelines and mobile

trucks stationed within the legal limits of the establishment. The inventory calculation will be

performed in accordance to the criteria provided in Annex 1 of amended Seveso II Directive.

IDENTIFICATION OF EVENTS LEADING TO MAJOR ACCIDENTS

Two are the main instruments for starting to hypothesize the events (such as leaks, failures,

over running of process parameters) capable to induce a major accident:

- Historical and statistic analysis

- Operability Studies (Hazop).

Historical and statistic analysis

Preliminary identification of major risks possibly affecting the subjected establishment is

carried out by a desk analysis of occurred or near missed past accidents in the facility under

study or in similar facilities/plants/units, taking into account involved substances, modalities,

causes, effects and consequences. Necessary information will be assumed also from

international referenced bibliography (reports) and specialized databases. With its experience

ICARO has built a proprietary data base, which recollects, updates and organizes information

from EU JRC Major Accidents Reporting System (MARS) and many other referenced sources.

HAZOP study

The HAZard and OPerability study is a structured and systematic examination of process or

operation that allows to identify and evaluate problems that may represent risks to personnel

or equipment. HAZOP is carried out by multi-disciplinary team (HAZOP team) during a set of

meetings. This technique leads to identify the potential hazards associated to process upsets,

by means of a deep analysis of process and the connected P&IDs. This method is the most

commonly used for major accidents identification.

Other methods

Other methods are available, according to some specific requirements, as

- Failure Mode and Effects analysis (FMEA)

- What If analysis

- Check lists and others.


RISK ANALYSIS AND

ASSESSMENT


The identified events (Top Events) are generally consisting in loss of dangerous substances

potentially leading to major accident hazards. In some cases sudden explosions or runaway

reactions are taken into account, according to specific situations.

Example of Hazop worked out P&I

The study will obviously consider the technological and organizational safety measures

implemented to prevent or mitigate the Top Events analyzed.

TOP EVENTS FREQUENCY

Frequency of Top Events (TE) will be generally estimated by two methods:

- statistical analysis of the recorded Losses Of Containment (LOC) frequency in similar facilities due to random causes (Random events);

- the application of the Fault Tree Analysis technique (Process Events).

Statistical frequency (Random events)

Loss of containment due to random causes are recollected to 3 basic equivalent diameters

having: 6,35 mm for small leaks, 25,4 mm for medium leaks, up to 100 mm about (4” = 101,6

mm) for heaviest leaks. Full bore failure is considered as conceivable for piping having small

diameters. Particularly, as far as heaviest leaks are concerned, taking into account also past

experiences of ICARO and literature indications, following cases have to be taken as a basis:

• full bore rupture for piping till 3” diameter (up to 3” = 76,2 mm std equivalent diam.);

• the 4” leak equivalent diameter for the 8” piping upward.

• for pipes included between 4” and 6”, equivalent diameter = 76,2 mm.


RISK ANALYSIS AND

ASSESSMENT


Characterization of the selected released stream (source terms as substance, pressure,

temperature, phases, flow rate), to be used in the accidental scenario’s analysis, has to be

performed in each case. TE basic frequency) will be selected within those indicated in the

American Petroleum Institute (API) referenced standards 581 (ed. 2000 and 2008), with some

adjustments to specific situation of the site, as recognized by API std, in terms di technological

and organizational safety measures implemented.

Fault Tree technique (Process events)

This technique allows to gather the information from HAZOP report and reproduce the logic

connections that bring from the initial causes to the final release of dangerous substances

(LOC). The representation will be developed with application of specific software, FTA Pro

released by Diadem Inc. The failure rate of each single initial cause will be taken from the

following international data bases:

• OREDA; Offshore Reliability Database Handbook, 2009

• Exida; Safety Equipment Reliability Databook, 2007

Negligible frequency (All events)

Events that are classified with an expected frequency of occurrence below the threshold value

of 1,0 x 10-6 occasions/year will be considered as negligible risks and not further developed.

POSSIBLE SCENARIOS AND RELEVANT FREQUENCY

Flammable and toxic gases releases may evolve in different ways, according to their

characteristics (i.e. flammable, not flammable) and to the presence of ignition sources. In

order to qualify and quantify all potential outcome scenarios (like fire, explosion, dispersion in

atmosphere), the “Event Tree” technique will be applied. This technique allows investigation of

all possible logical paths, each one having an assigned probability value.

Example of Event Tree application technique


RISK ANALYSIS AND

ASSESSMENT


Combining all the branches of the tree in the hypothesized accidental sequence, it is possible

to obtain the qualification and quantification (in terms of expected frequency) of all potential

scenarios. The evaluation of the predicted frequency of a scenario due to a release relies also

on properties of gas, temperature and pressure of the release, flow rate and environmental

condition. Basic frequency of the scenarios will be determined by means of probability

parameters usually adopted in the referenced literature/data bases.

As an example, in determining the specific source terms, release time of the leaks in absence

of necessary information will be determined as 30’. As far as ignition probability is concerned,

following set of values will be assumed from scientific literature:

In case of flammable mass below 500 kg, the UVCE is not considered as a possible scenario.

Technological and organizational safety measures implemented could largely influence the

frequency of an accidental scenario.

Negligible frequency (All scenarios)

Scenarios that are classified with an expected frequency of occurrence below the threshold

value of 1,0 x 10-7 occasions/year will be considered as negligible risks and not further

developed.

Example of a final summary reporting distribution of scenarios frequency


RISK ANALYSIS AND

ASSESSMENT


SCENARIO EFFECTS

A study on the physical effects of each identified scenario (radiation, pressure waves, tox.

concentrations and so on) will be performed by application of a specific software tool, the

package Phast Pro 7.1 released by DNV Technica. The package is generally used to calculate

the following effects, but not limited to:

• Radiation curves associated to fire scenarios;

• Overpressure values associated to explosions;

• Substance concentration profile associated to flammable and/or toxic dispersion.

The time duration of each single scenario will take into account the availability of prevention,

mitigation and containment measures (both technical and organizational) and the response

time of operating personnel and the Emergency Squads. Scenario’s effects are generally

ranked according to the following threshold values:

• Thermal steady radiation (jet/pool fires): 37.5 kW/m2, 12.5 kW/m2, 7 kW/m2, 5 kW/m2

• Gas cloud concentration for ignition (Flash fires): LFL, 0.5 LFL

• Blast Wave Overpressure: 0.3 bar, 0,15 bar, 0.05 bar

• Toxic Concentration: IDLH, LC50 and LC1.

• Thermal dose (4-3 s): 3200 kW/m2 (~100% fatality probability), 2000 kW/m2 (~50% fatality probability) and 1000 kW/m2 (~1% fatality probability).

With reference to the options available in the package, following assumptions will be applied:

• constant flow rate of the released fluid;

• jet fire: API model (sectioned open cone model);

• vapor cloud explosions: multi-energy model per plant area (partially confined), based on TNO model.

Effects evaluation will be developed according to the meteorological data of the site. As a

general criteria, in absence of specific local data, single wind speed and stability category (2-D

or 2-F) will be selected for the simulation, choosing amongst two the more dangerous in

extending the consequences of an accident.

CONSEQUENCES ASSESSMENT

Consequences analysis could be defined as the evaluation of the spatial spread of the effects,

determined as beforehand described, with the assessment of potential damages affecting

people, environment and assets.

Effects of a major accident will be properly mapped within the establishment, involving also

the surrounding territory if affected. The maps will allow the identification of the areas that

are potentially exposed to the ranked effects of the scenarios.

In the example below reported, the item initials (i.e. EP 01) are identifying a Top Event, source

of the considered scenarios. Bleu enveloped curves are referring to areas affected by Flash


RISK ANALYSIS AND

ASSESSMENT


Fire, violet curves are referring to areas affected by explosions (VCE), at 0,3 bar blast wave.

Inside dark brown curves could be found areas subjected to deadly toxic effects.

Example of scenarios’ effects map

DOMINO EFFECTS

An analysis of secondary major accident (Domino event) generated by a first accidental

scenario identified in the Safety Report is sometime required as detailed side study. The

Domino event unfortunately doesn’t find a unique definition accepted at worldwide level.

According to HSE -UK [COMAH):

“A domino event is defined as a loss of containment on a major hazard installation which has resulted

directly or indirectly from a loss of containment of an adjacent nearby major hazard installation. The two

events must occur concurrently or in close sequence and the hazard range must extend beyond that of

initiating event”.

ICARO srl developed many studies of Domino effects, with a proprietary methodology,

grounded on the most referenced literature and public/private sources. Starting from a

scenario developing effects affecting potential neighboring domino targets (i.e. strong blast

waves or radiation/jet fires hitting large inventories of LPG, LNG or flammable liquids), the

study will take into consideration: the target exposure (times, surface) to hitting vectors, the

prevention measures (such as gas detection system), the protection systems implemented


RISK ANALYSIS AND

ASSESSMENT


(physical barriers, cooling systems, steam barriers and others), the response to the emergency

by the organization and specialized squads, the accessibility to the scenario location and the

means/tools available and other parameters. Composing each parameter in a Event Tree, the

final frequency of a further induced major accident (Domino Effect) could be found as well as it

is possible to define the type of secondary scenario (i.e collapse, explosion) derived from the

first scenario.

RISK ASSESSMENT

For each identified scenario, the combination of frequency of occurrence and the relevant

severity of consequences, taking into account potential targets exposed to damages (people,

environment, assets) will be used in order to classify the risk, by means of the application of a

specific risk matrix. The risks will be classified as acceptable, ALARP (As Low As Reasonably

Practicable) and unacceptable, according to the specific matrix categorization. In case of

unacceptable or ALARP risk, measure for risk reduction will be identified and recommended.

As an example of Risk Matrix, following picture is reported below:

Dark brown boxes represent unacceptable risks. Grey boxes represent ALARP area, while

white boxes indicate acceptable risks condition.

Cla

ss

es o

f F

req

ue

ncy

Consequences: Classes of severity


RISK ANALYSIS AND

ASSESSMENT


DEFINITIONS

QRA: Quantitative Risk Assessment.

Hazop: the Hazard Operability study is a structured hazard identification tool using a

multi-disciplined team, for a process plant, directed towards the analysis of process

upsets which might lead to an accident.

Random loss: A loss of containment from piping and equipment due to random causes

which leads to a release of a hazardous substance in the environment.

Process loss: A loss of containment from piping and equipment due to process causes

which leads to a release of a hazardous substance in the environment.

Top Event (TE): A well identified and defined leak of hazardous substance,

characterized by a specific hole size and relevant frequency, following a random or

process loss.

Equivalent diameter: The measure of the hole size as diameter of a circle having the

same surface of the real hole.

Frequency: The estimated number of occasions that might lead to a Top Event

occurrence referred to a time period (normally a year).

Fault tree: Logical qualitative and quantitative representation of the possible

anomalies in plant operation that might lead to an accident or Hazard.

Event tree: Logical qualitative and quantitative representation of accident sequences,

from initial release to final scenarios (fire, explosion and dispersion).

Scenario: The final form assumed by the development of the accidental sequence

started by a top event, in terms of fire, explosion and/or dispersion in atmosphere.

Jet fire: The flame jet developed from the ignition of a pressurized release of a

flammable substance from a hole.

Pool fire: The fire developed from the ignition of a liquid pool of flammable substance.

(U)VCE: (Unconfined) Vapour Cloud Explosion; an accelerated combustion (from

deflagration to detonation) of a mass of flammable vapour in atmosphere that

produces significant values of over pressure.

LFL: Lower Flammable Limit: The lower concentration of flammable substance that

can be ignited in atmosphere.

Flash fire: An accelerated combustion of a vapour cloud without significant

overpressure consequences.

Stability class: Characteristic state of the atmosphere that influences the dispersion of

a gas. The higher the stability the more compact the cloud will travel.


RISK ANALYSIS AND

ASSESSMENT


REFERENCED BIBLIOGRAPHY AND SOURCES

1International Association of Oi l & Gas Producers , Risk Assessment Data Directory,

Report No.434-6.1 "Ignition Probabi l i ties", March 2010.2010

2

Flemish Government – LNE Department, Environment, Nature and Energy Pol icy Unit,

Safety Reporting Divis ion: “Handbook of fa i lure frequencies for drawing up a Safety

Report – Technica l report and Appendix, 5 maggio 2009

2009

3National Insti tute of Publ ic Health and the Environment (RIVM), Reference Manual Bevi

Risk Assessments , vers ion 3.2, 01/07/2009.2009

4API STD 581 – “Risk based inspection – Downstream Document - Recommended Practice ”

September 20082008

5 Exida 2007: Safety Equipment Rel iabi l i ty Handbook 2007

6UK HSE, Cl ive Nussey – “Fa i lure frequencies of high pressure s torage vessel at COMAH

s i tes . A comparison of data used by HSE and the Netherlands”, 20062006

7

H.I. Beerens , J.C. Post, P.A.M. Ui jt de Haag – “The use of generic fa i lure frequencies in

QRA: the qual i ty and use of fa i lure frequencies and how to bring them up to date” –

Journal of Hazardous Materia ls , 130 (2006), 265-270

2006

8 TOTAL - “Guidel ines for ri sk analys is”, doc HSE-SRD-004, 2006 2006

9Energy Insti tute, 2006, IP Research Report – Ignition Probabi l i ty Review, Model

Development and Look-up Correlations , London, UK.2006

10 Sintef 2006: PDS Data Handook 2006

11HSE – Planning case and assessment guide (PCAG) – Fa i lure rate and event data for use

within risk assessments , 20042004

12 W.K. Muhlbauer, Pipel ine Risk Management Manual , 3rd Ed., 2004, Elsevier 2004

13 SINTEF – OREDA, Offshore Rel iabi l i ty Data, 2002 2002


RISK ANALYSIS AND

ASSESSMENT


14Dimitri B. Kececioglu, "Rel iabi l i ty & Li fe Testing Handbook, Vol 1”, 2002, DEStech

Publ ications2002

15 Oreda 2002: Offshore Rel iabi l i ty Data, 2002 2002

16 API STD 581 – “Risk based inspection – Base Resource Document”, 2000 2000

17DNV Technica, a cura di John Spouge – “A guide to quanti tative ri sk assessment for

offshore insta l lations” – CMPT, 19991999

18TNO - Committee for the Prevention of Disasters , CPR, “Guidel ines for quanti tative ri sk

assessment – Purple Book”, doc CPR 18 E, 19991999

19Lees – “Loss Prevention in the Process Industries”, 2nd edition, 1996 – Butterworth –

Heinemann1996

20 E&P Forum: Quanti tative Risk Assessment Data Directory - Report No 11.8/250 1996 1996

21 AIChE – Chemica l Transportation Risk Anal isys – CCPS 1995

22

Hurst et a l . – “Fa i lure rates and incident database for Major Hazards” – 7th International

Sympos ium on Loss prevention and Safety Promotion in the Process Industry, Taormina

(IT), 1992

1992

23 Hydrocarbon Leak and Igni tion Database (1992). 1992

24 CCPS: Process Equipment rel iabi l i ty data base 1989

25 Progetto ARIPAR, Anal is i dei Rischi Industria l i e Portual i del l ’Area di Ravenna, 1987 1987

26 World Bank - “Manual of Industria l Hazard Assessment Techniques”, 1985 1985

27 B.J. Wiekema - TNO - "An Analys is of Vapour Cloud Explos ions Based on Accidents". 1983

28Thomas, HM – “Pipe and vessel fa i lure probabi l i ty” – Rel iabi l i ty Engineering, 1981; 2:83 -

1241981

29

Cremer & Warner - App IX in COVO Commiss ion- “Risk analys is of s ix potentia l ly

hazardous industria l objects in the Ri jnmond Area, a pi lot s tudy – A report to the

Ri jnmond Publ ic Authori ty”, 1981

1981

Documents

SEVESO SAFETY REPORT Guide Linesenserenergy.com/pdf1/dok-4.pdf · SEVESO SAFETY REPORT Guide Lines RISK ANALYSIS AND ASSESSMENT Page 4 / 13 Seveso Safety Report Guideline - Risk Assessment