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GUIDELINES FOR THE APPLICATION OF THE METHODOLOGY FOR STUDYING
DOMINO EFFECTS
I. INTRODUCTION
................................................................................................................
2
II. PRELIMINARY PHASE: GATHER NECESSARY INFORMATION FOR THE
DOMINO STUDY
....................................................................................................................
3
III. FIRST STEP: LOCATE DANGEROUS EQUIPMENT
............................................... 4 III.1. Followed
method
.........................................................................................................................
4
III.1.1. First point: "Locate sections on the establishments
plan" .................................................. 6 III.1.2.
Second point: "Draw up a list of the equipment being part of the
sections" ....................... 7 III.1.3. Third point:
"Equipment selection"
.....................................................................................
9 III.1.4. Fourth point : "Selected equipment classification"
........................................................... 15
III.1.5. Fifth point : "Regroup equipment in equipment zones"
..................................................... 17 III.1.6.
Sixth point: "note pipes linking equipment zones or feeding the
flare". ............................ 20 III.1.7. Seventh point :
"Meet the safety manager and visit the establishment".
........................... 20 III.1.8. Eighth point : "Fill in the
equipment data sheets"
............................................................ 21
III.1.9. Ninth point : "Final definition of the equipment zones"
.................................................... 21
III.2. Processing of the results
............................................................................................................
21
IV. STEP 2: SELECTION OF PRIMARY EQUIPMENT ITEMS OR EQUIPMENT
ZONES - PRIMARY ACCIDENTS, ASSOCIATED EFFECTS AND EPICENTRES ..
26
IV.1. Primary accidents, associated effects and epicentre
location .................................................... 26
IV.1.1. Solid products storage equipment
......................................................................................
26 IV.1.2. Pressure storage equipment
...............................................................................................
27 IV.1.3. Atmospheric or cryogenic storage equipment
...................................................................
27 IV.1.4. Small conditionings equipment
..........................................................................................
27 IV.1.5. Loading / unloading equipment
.........................................................................................
27 IV.1.6. Process equipment
.............................................................................................................
28 IV.1.7. Pipe networks
.....................................................................................................................
28
IV.2. Coupling equipment and accident scenario
..............................................................................
28 IV.2.1. Fire:
...................................................................................................................................
28 IV.2.2. Explosion and dust explosion:
...........................................................................................
28 IV.2.3. Pool fire:
............................................................................................................................
29 IV.2.4. Jetfire:
................................................................................................................................
29 IV.2.5. BLEVE:
..............................................................................................................................
29 IV.2.6.
VCE:...................................................................................................................................
29 IV.2.7. Tank fire:
............................................................................................................................
33 IV.2.8. Boilover:
............................................................................................................................
33
IV.3. Processing of the results
...........................................................................................................
33
V. STEP 3: SECONDARY EQUIPMENT DETERMINATION
....................................... 34 V.1. Determination of
effect distances
...............................................................................................
34 V.2. Processing of the results
.............................................................................................................
34
VI. STEP 4: DETAILED ANALYSIS OF PAIRS RETAINED DURING THE THIRD
STEP AS LIKELY TO BE INVOLVED IN A DOMINO EFFECT
................................. 35
VII. BIBLIOGRAPHY
..........................................................................................................
36
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GUIDELINES FOR THE APPLICATION OF THE METHODOLOGY FOR STUDYING
DOMINO EFFECTS
I. INTRODUCTION This document constitutes a practical guide for
the application of the methodology for studying domino effects [1].
The user must thus imperatively be acquainted with the contents of
this methodology and with the terms used. Moreover, this guide is
supplemented by a Technical Appendix [2]. The four steps
methodology permits to locate and characterize quickly hazardous
equipment items in dangerous establishments, as well as sequences
of accidents likely to form a domino effect (figure 1). These four
steps are preceded by a preliminary phase in order to gather
information.
Locate dangerous equipment
relevant data
Specific accidents forms
Step 1
Selection of primary equipment, accidents
and effects
Determination of secondary equipment,
domino effects
Detailed analysis of domino effects
Step 2
Step 3
Step 4
historical analysis and selection rules
method for calculating effect distances and selection rules
Simulation tools or experimentation
Preliminary phase
methodology description
needed data, equipment forms
establishment visit
Gather information
selection rules
contact safety officers
Potential domino effects
figure 1: a methodology for studying domino effects
In order to help the user of the methodology, a set of decision
diagrams were developed. These decision diagrams are presented and
commented in the continuation of the text.
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II. PRELIMINARY PHASE: GATHER NECESSARY INFORMATION FOR THE
DOMINO STUDY Various information about the studied establishments
are needed before the domino study can begin. The needed
information for each establishment are presented in the document
describing the methodology [1]. From the very beginning of the
preliminary phase, the document summarizing the principles of the
methodology must be given to the concerned establishments, so that
they understand what is expected from them. Equipment forms are
joined to this document and will be used later in order to obtain
detailed information about some hazardous equipment items (see at
the end of the first step). After receipt of these information, it
is useful that the user of the methodology visits the concerned
establishments and meets the safety managers. The aims of the
meeting with the safety manager are: To check that the methodology
process has been well understood by the safety manager of
the studied establishment; To check that the information at the
methodology user disposal is complete enough to
realize the study. During this meeting, it is especially
advisable to: examine the establishment plan in order to understand
what are and for what are used the
elements appearing on the plan; ask the safety manager to
specify the location and the nature of the hazardous equipment
items; check the presence of possible underground pipes; specify
the location of all loading/unloading equipment (watch especially
road
loading/unloading facilities which can be scattered in the
establishment whereas rail and river facilities are more easy to
locate on a plan);
specify the location of compressors, pumps and other utilities;
specify the location of eventual boilers; specify the location of
an eventual gas expansion facility; examine the neighbourhood of
the establishment: are there other companies covered by the
Directive in the vicinity of the establishment considered ? If
so, these establishments must be integrated into the domino
study.
The visit of the site helps to be aware of the real volume and
configuration of the equipment items, their layout on the site, the
position of pipes... During the visit, it is necessary to pay
attention to:
the presence of roads close to the different equipment items
(risk of traffic accident involving an equipment item, risk of
hitting a pipe ...);
the presence of temporary parkings (for example rail or road
tank cars waiting for loading or unloading) and their location with
respect to the different equipment items;
the congestion of the different zones of the establishment (the
congestion is important in order to evaluate vapour cloud explosion
hazards), and the average height of the equipment items (in order
to determine the volume of an eventual vapour cloud present
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in the congested zone. Detailed calculation is explained in the
Technical Appendix [2]);
the presence and the layout of bunds and safe away spill
containment; the presence of hot spots (furnaces, boilers, engines,
flares ...) likely to be an ignition
source for a vapour cloud; the presence of safety systems.
III. FIRST STEP: LOCATE DANGEROUS EQUIPMENT The purpose of the
first step is to catalogue, categorize and locate dangerous
equipment items or equipment zones in every concerned
establishment. III.1. FOLLOWED METHOD The logical way of drawing up
the list of equipment zones to be retained in the domino study is
specified in decision flowcharts. These flowcharts are presented in
the text below. It concerns the following decision flowcharts:
flowchart 1.1: Summary of the first step; flowchart 1.2: List of
equipment items being part of a section; flowchart 1.3: Selection
criteria for equipment items belonging to storage or loading /
unloading sections; flowchart 1.4: Selection criteria for
equipment items belonging to process sections; flowchart 1.5:
Selection criteria based on the nature of the substances and the
quantities
involved; flowchart 1.6: Determination of a category for the
storage equipment; flowchart 1.7: Regroup storage equipment,
loading / unloading equipment and pipe
network in equipment zones. The first step includes 9 points
which are listed below.
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Flowchart 1.1: Summary of the first step
1. Locate sections on the establishment plan
2. Draw up a list with the equipment being part of the sections
(flowchart 1.2)
3. Apply selection criteria for each equipment item (flowchart
1.3, 1.4, 1.5)
Were all theequipment listed in the second
point examinated?
The list of equipment items involved in the domino study is
determined
4. Classify selected equipment (equipment categories) (flowchart
1.6)
5. Group equipment in equipment zones (flowcharts 1.7, 1.8)
yes
yes
no
Are all the elementsof the plan included
in a section ?
no
(List DOMINO98-L1)
(List DOMINO98-L2)
(List DOMINO98-L2)
(List DOMINO98-L2)
(List DOMINO98-L2)
6. Not pipes linking equipment zones (flowchart 1.5) and pipe
network feeding the flare.
The list of equipment zones involved in the domino study is
determined
7. Meet the safety manager and visit the establishment.Choose
equipment requiring an equipment data sheet to be filled in.
8. Fill in equipment data sheets (safety manager).
9. Final definition of the equipment zones.
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III.1.1. First point: "Locate sections on the establishments
plan" a) Definitions Establishment: the whole area under the
control of an operator where dangerous substances
are present in one or more installations, including common or
related infrastructures or activities (article 3, paragraph 1 of
the European Directive 96/82/EC of 9 December 1996 [3]).
Section: part of an establishment forming a logical set,
geographically separated from the other parts of the establishment
(for example by a wall or an open space). The following sections
are considered: storage, loading and unloading, process and
buildings.
Storage section: section used for the storage of raw materials,
intermediate goods, manufactured products or waste products. These
sections are only used for storage (not for the processing of
substances).
Loading / unloading section: section used for inlet and outlet
of substances in the establishment, involving transport equipment
(rail or road tank car, barge ...)
Process section: section used for the processing of the
substances or for the production of the energy used in the
establishment. The process section can be a "power", "classic" or
"miscellaneous " one.
"Power" process section: process section specifically designed
for the production and the supply of energy to the establishment
(e.g.: section including furnaces, boilers, ...).
"Classic" process section: process section specifically designed
for the processing or the physical or chemical separation of
substances (e.g.: reaction, distillation, purification zone,
secondary products or effluents treatment zone, ...)
"Miscellaneous" process section: process section which does not
include any of the above quoted elements but which handles
dangerous substances (e.g.: set of pumps, compressors, gas
expansion facility, ...).
"Buildings" section: section made up of buildings
(administrative, technical, ... ones). b) Comments The plan of the
establishment must be used in order to define sections, by means of
simple logical and geographical criteria (open spaces, walls,
buildings, roads, ...)
These sections are:
storage sections (raw materials, intermediate goods,
manufactured products, waste products, ...);
loading / unloading sections for in and out goods; process
sections (products processing, energy production, ...)
buildings.
At the end of this first point, the user of the methodology must
draw up the list DOMINO98-L1
of all the sections identified in the studied establishments
(see "processing of the results" in paragraph III.III.2.).
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III.1.2. Second point: "Draw up a list of the equipment being
part of the sections" a) Definitions Equipment: elementary
constitutive parts of a section (for example: storage tank,
reactor,
distillation column, boiler, heat exchanger, rail tank car, ...)
"Slender" equipment: equipment item which is higher than 20 m and
which height/diameter
ratio is higher than 4. Intermediate storage equipment:
container used in a process in order to stock substances
temporarily. This container is located in the corresponding
process section. Dangerous substances [3]: substances which
toxicity, flammability, unstability or explosivity
may induce hazard for people or equipment. The used hazard
characteristics are based on the hazard classes of the 'Guide des
Pompiers de Genve' [4]. The following classes are selected:
toxic substances: classes 2, 3 and 4; flammable substances:
classes 1, 2, 3 and 4; unstable substances: classes 3 and 4;
explosive substances: classes 3 and 4.
The hazard classes of the main substances handled in industry
are given in the Technical Appendix [2].
Quantity: a quantity is the mass of substance being used. This
quantity can be a static mass
(mass in a vessel) or a dynamic mass (maximum flow rate
multiplied by a period of time given in the methodology, for
example half an hour).
b) Comments For every section defined in the first point, the
constituent equipment items should be listed. This is performed in
accordance with flowchart 1.2. With regard to the "Buildings", one
must make sure that they are not used for the storage of dangerous
substances, for a process section (pilot unit, ... ) or for a
loading / unloading section. If it is not the case, the 'building'
section is no longer considered. In the opposite case, this section
should be classified and treated as a storage, process or loading /
unloading section. At the end of this second point, all the
equipment items constituting the above defined sections must have
been listed by the user. The set of these equipment items must be
listed in the list DOMINO98-L2 (see "processing of the results",
paragraph III.III.2.).
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Flowchart 1.2: list of equipment items being part of a
section
loading /unloadingsection ?
yes
Draw up a list with : the mean of transport type (lorry, rail
tank car, barge, ... ) the nature of the substance contained in
each equipment item the mass or the volume of substance contained
in each equipment
item, as well as the flow rates during transfer operations
no
"power"process
section ?
processsection ?
"classic"process
section ?
yes
yes
Draw up a list with : boilers and furnaces equipment items using
thermal oil at high temperature the energy used (gas flow rate or
quantity of stored
fuel)END
no
yes
Draw up a list with: columns, "slender" equipment items,
reactors intermediate storage equipment equipment working at a
pressure higher than 30 bar equipment working with thermal oil at
high temperature for each equipment item, note down the handled
substance (nature, quantity and/or flow rate)
no
Note down the main handled substances and their quantityand/or
flow rate
storagesection ?
yes
Draw up a list with: the identification codes of the storage
equipment items. the nature and quantity of the substances
contained in each
equipment item
ENDno
(List DOMINO98-L2)
(List DOMINO98-L2)
(List DOMINO98-L2)
(List DOMINO98-L2)
(List DOMINO98-L2)
no
Building ?
Do the buildinghouse a storage, process
or loading/unloadingsection ?
yes
Classify this section as a storage, process orloading/unloading
one.
The section is no longerconsidered in the continuation of
the domino study
Impossible ! The section must be a storage,
process,loading/unloading or building one.
Go back to the beginning of the flowchart 1.2
END
yes
no
no
END
END
END
"miscellaneous"processsection
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III.1.3. Third point: "Equipment selection" a) Definitions
Runaway hazard: hazard of uncontrolled acceleration of a reaction
in a reactor or a tank
(often intermediate storage tank in a process), generating a
high overpressure endangering the integrity of the vessel.
Internal explosion: explosion of a closed vessel, often due to
the accumulation of explosive
substances (vapour, gas or dust) under the tank roof. b)
Comments Each equipment item listed in the second point must be
examined by means of selection criteria given in decision
flowcharts 1.3, 1.4 and 1.5, in order to select or not the
equipment item for the continuation of the domino study.
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Flowchart 1.3: selection criteria for equipment items belonging
to storage orloading - unloading sections
Is the substancecontained in the equipment
item a dangerous one ?Do not select the equipment item END
yes
Storage equipment (solid, underpressure, atmospheric,
smallconditionnings) or loading -
unloading equipment
no
Is the substancequantity known ?
Get information about the substance quantity
no
Is thesubstance quantity
higher than5 tonnes ? See flowchart 1.5.
no
END
yes
yes
SELECT the equipment item END
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Flowchart 1.4: Selection criteria for equipment items belonging
toprocess sections
"power"process ?
no
process section
Select automatically: boilers furnaces burning gas fuel tanks if
the stored quantity is higher than 5
tons equipment items using thermal oil at high
temperature
END
yes
"classic"process ?
Select automatically : columns "slender" equipment items
equipment items working at pressure higher
than 30 bar equipment items using thermal oil at high
temperature
yes
Select: reactors and intermediate storage equipment
IF risk of runaway or IF risk of internal explosion all
equipment items containing or handling
dangerous substances in sufficient quantity(see flowchart
1.5)
Select equipment items containing or handlingdangerous
substances in sufficient quantity(see flowchart 1.5)
no
END
"miscellaneous"process ?
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Flowchart 1.5: Selection criteria based on the nature of
thesubstances and the quantities involved
Dangeroussubstance ?
no
DO NOT SELECT END
yes
Quantityhigher than
5 tons ?
yes
no
Work at atemperature nearthe flash point ?
Flammablesubstance ?
(1,2,3,4)*yes
no
SELECT END
Fire durationlonger than 10 to 15
minutes ?
no yes
SELECT END
Substance ofclass 1 ?
yes
yes
SELECT END
no
no
*: hazard classes of the "guide orange des sapeurs-pompiers
genevois"
page 1/3
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Flowchart 1.5.
page 2/3
Explosivesubstance ?
(3,4)*
yes
Is thesubstance reactivity
high ?
SELECT
yes
Quantityhigher than 100
kg ?
yesno
SELECT
END
yes
Quantityhigher than 500
kg ?
yesno
SELECT
Quantityhigher than 1000
kg ?
yes
no
no
no
END
END
no
The storedor handled substance
is gaseous or liquid at a temperaturehigher than its boiling
temperature at atmosphericpressure ?
yes
no
Is thesubstance reactivity
average ?
The substancereactivity
is low.
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The substance issolid
Is the vaporpressure at 20Cbetween 0.5 and
1 bar ?
yes
Flowchart 1.5.page 3/3
Is the substancereactivity high ?
no
yes
Possible poolsurface higherthan 200 m ?
no
SELECT
END
no
yes
Toxicsubstance ?
(2,3,4)*yes
Substance ofclass 4 ?
noSELECT
yes
END
SELECT
Substance ofclass 3 ?
yes
Quantityhigher than
?
yesno
END
SELECT
Substance ofclass 2 ?
Quantityhigher than
?
yes
ENDUnstable
substance ?(2,3,4)*
The substanceis liquid at atmospheric
pressure ?
yes
selection criteria remainto be defined
selection criteriaremain to be defined
*: hazard class of the "guide orange des sapeurs-pompiers
genevois"
no
no
no
yes
no
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Decision flowcharts 1.3 and 1.4 give respectively selection
criteria for, on the one hand, equipment of storage sections (four
types) or loading/unloading sections and for, on the other hand,
equipment of process sections. The decision flowchart 1.5 must only
be used if the user is referred to it by the flowcharts 1.3 or 1.4
(or for selection criteria related to pipes, see point 6). Some
remarks can be made about these decision flowcharts:
Once an equipment item is selected on any criterion, the other
selection criteria do not need to be examined. The association
between an equipment item and the other accident scenarios will be
made in the second step.
In the decision flowcharts 1.3 and 1.4, if the quantity of
dangerous substance handled or stored is higher than 5 tons, the
equipment item will automatically be taken into consideration in
the continuation of the study. In most accident cases, this
quantity is considered as sufficient to cause significant effects
in the sense of domino effects.
In the decision flowchart 1.4, it can be noted that only
furnaces burning gas are selected, and will be coupled with a gas
release scenario. Furnaces burning fuel oil or other liquid fuel
will not be selected for themselves, but the corresponding fuel
tank will be selected (if the quantity is higher than 5 tons).
In the decision flowchart 1.4, reactors and intermediate storage
tanks are systematically selected if a risk of runaway or internal
explosion is present.
In the decision flowchart 1.5, the selection of an equipment
item containing or handling a flammable substance depends on the
duration of the possible fire. An easy method for the computation
of pool fires duration is proposed in the Technical Appendix
[2].
In the decision flowchart 1.5, with regard to the selection of
equipment items containing liquid explosive substances, only the
case of highly reactive substances is taken into account, as far as
these substances have a vapour pressure between 0.5 and 1 bar and
are likely to form a pool whose surface is larger than 200 m (a
method for calculating the pool surface is given in the Technical
Appendix [2]). For equipment containing substances with other
reactivity or other vapour pressure, a quantity higher than 5 tons
is necessary for creating a severe risk of explosion. Therefore,
either these equipment items are already selected, either they must
not be retained.
III.1.4. Fourth point : "Selected equipment classification" a)
Definitions Equipment category: the seven equipment categories
permit to classify the equipment items
according to their characteristics. The equipment categories are
the following ones:
solid products storage equipment pressure storage equipment
atmospheric or cryogenic equipment small conditionings storage
equipment loading / unloading equipment process equipment pipe
networks
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(1) solid products storage equipment It concerns storage of
solid substances in the form of powder or pellets. These substances
must be stored in bulk (solid products storage in form of bags are
not taken into account).
(2) pressure storage equipment Pressure storage tanks shall mean
storage tanks working at a pressure above 2 bar (pressure exerted
by the substance or by an inert). These tanks are used to store
pressure liquefied gases as chlorine, LPG, vinyl chloride monomer,
ammonia, ... that is to say substances with a vapour pressure
largely higher than the atmospheric pressure. Refrigerated pressure
storage are also classified among pressure storage equipment, as
far as the pressure is higher than 2 bar. Even if other equipment
is likely to work above atmospheric pressure (for example some
reactors), only storage tanks are included in this category. (3)
atmospheric storage equipment This category concerns only storage
tanks. The different types of atmospheric storage (with floating
roof, with fixed roof, without roof) are included in this category.
Cryogenic storage are in the same category as atmospheric storage,
since they work generally at atmospheric pressure or at low
pressure. (4) small conditioning storage equipment Small
conditionings shall mean low capacity storage as carboys, drums and
all storage tanks which individual volume is smaller than 1 m.
Considered alone, they can probably not cause a major accident.
Nevertheless, they are sometimes stockpiled in a limited space and
the extent of the stored volume of substances represents a
potential cause of accident.
(5) loading / unloading equipment Loading and unloading
equipment is necessary to the establishment operations. The
equipment can be road tank cars, rail tank cars or boats. They are
potentially dangerous because they imply frequent handling. (6)
process equipment This category includes: equipment designed for
the processing or the physical or chemical separation of
substances (reactor, distillation column, absorption column,
liquid-liquid extraction, centrifuge, ... );
intermediate storage equipment integrated into the process;
utility facilities (pumps, heat exchangers, compressors, gas
expansion facility, ...); equipment designed for energy production
and supply (furnaces, boilers, ...); all the pipes pertaining to
the above quoted equipment are included in the process
equipment. (7) pipes networks Piping linking different equipment
zones are considered as "pipes networks" (for example a pipe
linking an unloading facility and a storage area, or linking a
storage area and a process area), as well as pipes feeding the
flare.
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Are not considered as "pipes networks" Small pipes pertaining to
an equipment item (for instance drain off pipe or sampling
pipe ...). Those are considered to belong to the equipment item
with which they are connected.
Pipes pertaining to a process. Those are studied with the
process equipment. b) Comments The classification into categories
is obvious for process, loading/unloading equipment and pipes
networks. On the other hand, for storage equipment, the decision
flowchart 1.6 can help the user in order to classify storage
equipment in the above defined categories. The selection of pipes
will be explained in point 6 hereunder. III.1.5. Fifth point :
"Regroup equipment in equipment zones" a) Definitions Equipment
zone: set of equipment items belonging to a same category (among
the seven
categories quoted above), logically grouped and behaving, in
principle, identically in case of accident. In an equipment zone,
in order to calculate effect distances, only primary accidents
related to the most dangerous equipment item (for example the
larger one) will be studied. An equipment zone can be constituted
by a single equipment item.
b) Comments The decision flowchart 1.7 can be used in order to
group most equipment items selected in the previous point in
equipment zones. The grouping criteria are: 1. For solid products
storage equipment (see decision flowchart 1.7): solid storage
are
separated according to simple geometric criteria (warehouses,
storage areas, ... ) and according to the stored substances.
2. For pressure storage equipment (see decision flowchart 1.7):
Each equipment zone
belonging to the category 'pressure storage equipment' includes
storage vessels presenting the following common features:
substances likely to produce the same types of accidents; a
location in a same bund if there is a bund, or a same location on
the plant in case of
lack of bund. Furthermore, if the involved substances are likely
to give rise to a BLEVE, the equipment zone can only be constituted
of vessels presenting a similar geometry (sphere, horizontal
cylinder, vertical cylinder). If vessels differ from one another in
one criterion quoted above, they have to be grouped in distinct
equipment zones.
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Flowchart 1.6: determination of category for storage
equipment
The equipment item isa storage one
Substancestored in a solid
form ? Solid substances storage END
yes
Substancestored in a gaseousform (and volume
higher than1 m) ?
Pressure storage END
yes
Pressure storage END
no
no
yes
Pressure inthe tank higher than
2 bar ?
yes
Atmospheric storage END
no
no
Possible classification in thesmall conditionings category
Substancestored in a liquid
form (and volumehigher than
1 m) ?
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Flowchart 1.7: Grouping in equipment zones for:storage,
loading/unloading equipment and pipes networks
Are the consideredsubstances likely to produce the same
type of accidents ? (closely relatedhazard classes)
yes
Presence of a bund ?
The consideredequipment items are located at
a same place on theplant ?
The consideredequipment items are in
the same bund ?
yes
yesyes
no
Are the consideredequipment items likely to give rise to
a BLEVE ?
Do theequipment itemspresent the same
geometry ?
yes
The equipment items belongto different equipment zones
The equipment items belong tothe same equipment zone
no no
no
yes
no
no
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3. For atmospheric storage equipment (see decision flowchart
1.7): the atmospheric tanks are
grouped in a same equipment zone if they are located in a same
bund and if the contained substances are likely to cause the same
types of accidents. If there is no bund, the tanks are grouped
according to simple geographical criteria. The equipment zones are
defined according to the presence of traffic ways, buildings, ...
The division by substances is always kept. In no case, a single
equipment zone can include equipment items belonging to distinct
bunds.
4. For 'small conditionings' equipment (see decision flowchart
1.7): small conditionings will
be grouped in equipment zones according to geographical criteria
(storage areas, warehouses, ...) and according to the nature of the
stored substances.
5. For loading/unloading equipment (see decision flowchart 1.7):
An equipment zone will be
defined in every plant location where there is a loading or
unloading area. If different substances are handled in a same place
and if they present different hazards, several equipment zones will
be defined.
6. For process equipment: The process equipment are grouped in a
single equipment zone if
they are located at a same place in the plant and if they are
likely to give only rise to the same types of accidents.
III.1.6. Sixth point: "note pipes linking equipment zones or
feeding the flare". Once the grouping in equipment zones (storage,
loading / unloading and process) is achieved, the linking pipes can
be selected and grouped. The selection is based on the decision
flowchart 1.5. Equipment zones are created by separating pipes
according to their location and the nature of the considered
substances, as shown in the decision flowchart 1.7. III.1.7.
Seventh point : "Meet the safety manager and visit the
establishment". The meeting with the safety manager of the
concerned establishment is essential. This meeting is notably
useful in order to:
review all the selected equipment zones and discuss their
relevance; gain from the safety manager's experience and from his
in-depth knowledge of his
establishment; be bothered about accidents which previously
occurred in the establishment or in other
companies using similar process. At the end of this meeting,
equipment items for which an equipment data sheet is needed should
have been chosen. If necessary, a second visit of the establishment
can be useful, especially for the choice of the congested
zones.
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III.1.8. Eighth point : "Fill in the equipment data sheets"
Equipment data sheets will be filled in by the safety manager.
III.1.9. Ninth point : "Final definition of the equipment zones"
The received equipment data sheet allow to complete the definition
of the equipment zones. III.2. PROCESSING OF THE RESULTS During the
first step, the user must draw up a first list (DOMINO98-L1)
presented hereunder. For each establishment, the user must write
down the name of the concerned industrial area, the name of the
establishment, the date, the person in charge of the study. He must
also list and describe succinctly the sections present in the
establishment:
storage sections; loading / unloading sections; process
sections; buildings.
A second list, also presented hereunder (DOMINO98-L2), allows
the person in charge of the
study to draw up a list with all the equipment items
constituting the above described sections, with the following
information:
the concerned section; the identification number or code of the
equipment item; the equipment item description; the substance
stored or handled in this equipment item; the hazard classes of the
considered substance (see Technical Appendix [2] or
[4]); possibly the temperature and pressure conditions (to be
specified for process
equipment); the stored or handled quantity (content or concerned
flow); the selection or not of the equipment item for the
continuation of the domino
study. if the equipment item is selected, it is classified in
one of the seven categories
previously defined (solid storage SOL, pressure storage PS,
atmospheric storage ATM, small conditionings SM, loading/unloading
LU, process PRO, pipes networks PIP);
the equipment zone number: several selected equipment may belong
to a same equipment zone. This zone will be considered in the
continuation of the domino study.
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Industrial area:
Establishment: Date :
Person in charge of the study:
DOMINO98 - L1: LIST OF SECTIONS
Types of sections : Storage; loading and unloading; Process :
"power","classic", "miscellaneous"; Buildings.
Identification Type of
section Description
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Once these lists are filled in, the user of the methodology can
begin to prepare a table (DOMINO98-L3) including the following
columns:
column 1: equipment zone number; column 2: code allowing to
identify the equipment zone on the plan; column 3: description of
the equipment zone, nature and quantity of handled substances
considered as characteristic of the equipment zone; column 4:
type of equipment zone (SOL, PS, ATM, SC, LU, PRO, PIP).
This table, actual summary of the information gathered during
the domino study, will be completed during the following steps. The
reader can see the Technical Appendix [2] in order to examine a
fictitious example of application of the methodology.
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IV. STEP 2: SELECTION OF PRIMARY EQUIPMENT ITEMS OR EQUIPMENT
ZONES - PRIMARY ACCIDENTS, ASSOCIATED EFFECTS AND EPICENTRES The
purpose of this second step is to select equipment or equipment
zones likely to develop a primary accident, among those previously
selected. Moreover, potential effects and epicentres must be
associated with these equipment. Only equipment or equipment zones
likely to cause an accident with thermal and/or mechanical effects
are selected as primary equipment or equipment zones. Equipment
zones only presenting toxic hazards are to be considered among
secondary equipment zones. According to a data analysis on past
accidents [5], it can be noted that some types of equipment zones
or some types of accidents cannot be the first event producing a
domino effect. Those are listed as follows:
Small conditionings equipment rarely cause a major primary
accident. Actually, the simultaneous failure of several containers
is unlikely. On the contrary, they can produce a secondary fire or
lead to missile effects.;
A BLEVE can only occur if the vessel is fire engulfed (or
nearly). The BLEVE is then a secondary accident. The primary
accident is often a pool fire or a jet fire;
A boilover is a secondary accident, too. It is the consequence
of a primary fire, namely a tank fire or a pool fire.
However, these secondary equipment or accidents can become
primary ones in domino effects in series (the secondary accident in
the first domino effect becomes the primary accident in a second
domino effect). Therefore, small conditionings are nevertheless
retained among primary equipment, as well as BLEVE and boilover are
studied with primary accidents. They are not the first event in a
domino effect, but can be primary events during domino effects in
series. IV.1. PRIMARY ACCIDENTS, ASSOCIATED EFFECTS AND EPICENTRE
LOCATION The following tables summarize primary accidents,
associated effects and epicentre location for each equipment type
selected. In order to realize this association, one must accurately
determine the scenarios, among possible ones, which must be
associated with the considered equipment zone (see paragraph
IV.IV.2.). IV.1.1. Solid products storage equipment Primary
accident Primary effect Epicentre location
Fire Radiation In the considered equipment zone Explosion and
dust explosion
Overpressure Missiles
In the considered equipment zone
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IV.1.2. Pressure storage equipment Primary accident Primary
effect Epicentre location
Pool fire Radiation In the considered equipment zone Jet fire
Radiation In the considered equipment zone BLEVE Overpressure
Missiles In the considered equipment zone
VCE Overpressure In a congested zone located within a given
range round the considered equipment zone
NB.: Each time a VCE (Vapour Cloud Explosion) can occur, a
flashfire can happen too. The flashfire is observed when the
flammable cloud ignites outside a congested zone. In that case, the
flame speed is not sufficient to lead to notable pressure effects.
Moreover, the thermal effects of a flashfire are generally
insufficient to induce a secondary accident. In most cases [5], the
flashfire consequences are to cause a pool fire or a jet fire in
the flammable release location. Therefore, the flashfire is not
considered as a specific accident, but its eventual consequences
are taken into account. IV.1.3. Atmospheric or cryogenic storage
equipment Primary accident Primary effect Epicentre location
Pool fire Radiation In the considered equipment zone Tank fire
Radiation In the considered equipment zone Tank explosion Missiles
In the considered equipment zone VCE following the vaporization of
a flammable substance
Overpressure In a congested zone located within a given range
round the considered equipment zone
Boilover (not for cryogenic storage)
Radiation In the considered equipment zone
IV.1.4. Small conditionings equipment Primary accident Primary
effect Epicentre location
Fire Radiation In the considered equipment zone Explosion
Missiles In the considered equipment zone IV.1.5. Loading /
unloading equipment Depending on whether the substance is solid or
liquid at atmospheric pressure or under pressure (also gaseous
substance) the effects and epicentres will be the same as
considered respectively for solid products storage, atmospheric
storage and pressure storage.
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IV.1.6. Process equipment Primary accident Primary effect
Epicentre location
Fire Radiation In the considered equipment zone Jet fire
Radiation In the considered equipment zone Explosion and dust
explosion
Missiles Overpressure
In the considered equipment zone
VCE Overpressure In a congested zone located within a given
range round the considered equipment zone
IV.1.7. Pipe networks Primary accident Primary effect Epicentre
location
Pool fire Radiation In the considered equipment zone Jet fire
Radiation In the considered equipment zone VCE Overpressure In a
congested zone located within a given range
round the considered equipment zone IV.2. COUPLING EQUIPMENT AND
ACCIDENT SCENARIO Each equipment or equipment zone retained during
the first step of the methodology can, a priori, cause various
primary accidents presented in the previous paragraph. However,
according to the concerned type of equipment, the nature and the
quantity of involved substances, some accident scenarios will be
removed from the domino study. IV.2.1. Fire: The "fire" accident
scenario must be associated with solid products storage equipment,
small conditionings equipment, loading/unloading equipment and
process equipment containing or handling a substance belonging to
the flammability class 1, 2, 3 or 4 (for the substances belonging
to the class 1, only if they are used at a temperature higher than
their flash point), as far as the potential duration of the fire is
longer than 10 to 15 minutes. Moreover, it is always necessary to
verify that the fire smokes do not contain toxic substances
(secondary accident). IV.2.2. Explosion and dust explosion: The
"explosion" accident scenario must be associated with all the
equipment in which a sudden pressure increase can occur, and cause
the failure of the equipment item with a possible ejection of
missiles. So, we consider: dust explosion in storage silos and in
equipment handling pulverulent solids (crushing,
drier, ...); tanks explosions; explosions of reactors (runaway),
columns, intermediate storage tanks integrated in a
process, equipment items working at a pressure higher than 30
bar; small conditionings explosion; ...
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IV.2.3. Pool fire: The "pool fire" accident scenario can be
associated with pressure storage equipment, atmospheric or
cryogenic storage equipment, loading / unloading equipment and
pipes networks. The decision flowchart 2.1 helps the user to
realize the association between an equipment item and a pool fire
scenario. The choice of the scenario depends on the fire duration.
A method for calculating this duration is presented in the
Technical Appendix [2]. IV.2.4. Jetfire: The "jetfire" accident
scenario must be associated with all pressure equipment items
containing a flammable substance. IV.2.5. BLEVE: The "BLEVE"
accident scenario must be associated with all the pressure
equipment items containing a substance quoted in the Table 1. This
list is not exhaustive.
Acetylene Hydrogen chloride Carbon dioxide Ethylene oxide
Ammonia Methyl chloride Ethylene Oxygen Butadiene (and C4) Vinyl
chloride monomer Liquefied natural gas Propane Butane, Butene and
isomers Cyclohexane Hydrogen Propylene Butadiene chloride Dimethyl
ether Methane
Table 1: List of main substances likely to give rise to a BLEVE
[6] IV.2.6. VCE: The "VCE" accident scenario can be associated with
pressure storage, atmospheric or cryogenic storage, loading /
unloading equipment, process equipment and pipes networks. The
decision flowchart 2.2 helps the user to realize the association
between an equipment item and a VCE scenario. The existence of a
congested zone is needed in order to envisage a VCE scenario (see
Technical Appendix [2]). This congested zone can be located in an
establishment different from the establishment where the release
occurs.
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Flowchart 2.1: selection criteria for a pool fire scenario
Flammablesubstance ?(class 1*, 2,
3 ou 4)
no
DO NOT SELECT THE SCENARIO END
yes
Quantityhigher than
5 tons ?
no
yes
SELECT THE SCENARIO END
Fire durationlonger than 10 to 15
minutes ?
no
DO NOT SELECT THE SCENARIO
END
yes
SELECT THE SCENARIO END
*: a substance belonging to the first flammability class is only
takeninto consideration if used at a temperature higher than its
flash point
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no
Explosivesubstance ?
(3,4)
yes
SELECTION
yes
yesno
SELECTION
END
yes
yesno
SELECTION
yes
no
no
no
END
END
no
yes
Flowchart 2.2: Selection criteria for a VCE** scenario
NOSELECTION
END
** it is tought that acongested zone is present
The storedor handled substance
is gaseous or liquid at a temperaturehigher than its boiling
temperature at atmosphericpressure ?
Is thesubstance reactivity
high ?Quantity
higher than 100kg ?
Is thesubstance reactivity
average ?
Quantityhigher than 500
kg ?
The substancereactivity
is low.Quantity
higher than 1000kg ?
page 1/2
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The substanceis liquid
Pool outsidea bund on a concrete
soil ?
yes
Flowchart 2.2.
page 2/2
SELECTION IF the released quantity is higherthan the quantity
shown in the table (tons)
no
Pool within a bund or on aground nature other than
concrete SELECTION IF the pool surface is larger thanthe surface
shown in the table (m)
END
END
0.5 < Psat < 1 bar 2 5 100.1 < Psat < 0.5 bar 5 10
40Psat < 0.1 bar 40 no no
Highreactivitysubstance
Averagereactivitysubstance
Lowreactivitysubstance
0.5 < Psat < 1 bar 200 500 10000.1 < Psat < 0.5 bar
500 1000 4000Psat < 0.1 bar 4000 no no
Highreactivitysubstance
Averagereactivitysubstance
Lowreactivitysubstance
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IV.2.7. Tank fire: The "tank fire" accident scenario must be
associated with all atmospheric or cryogenic storage equipment
containing a substance belonging to the flammability class 2, 3 or
4. IV.2.8. Boilover: The boilover scenario can only be associated
with atmospheric storage equipment meeting the conditions defined
in the Technical Appendix [2]. IV.3. PROCESSING OF THE RESULTS In
the table DOMINO98-L3 summarizing the results of the domino study,
several columns can be filled in:
column 5: primary or secondary nature of the equipment zone;
column 6: primary accidents associated with the equipment zone
(pool fire, VCE,
BLEVE, ...); column 7: primary effects and thresholds associated
with the accidents (overpressure
160 mbar, radiation 8 kW/m, ...); column 8: epicentre of each
accident (if the accident considered is a VCE, note down
every congested zone located in a range of 200 m around the
considered equipment zone).
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V. STEP 3: SECONDARY EQUIPMENT DETERMINATION The purpose of this
third step is to quickly select pairs of equipment zones belonging
to different establishments and likely to be involved in a domino
effect. In order to achieve this, for each effect associated with
an accident related to a primary equipment or equipment zone, an
effect distance is estimated, by means of simple criteria. An
effect distance shall mean a distance at which a given effect
threshold is reached. An equipment item or equipment zone exposed
to this effect threshold runs the risk of being sufficiently
damaged to produce a secondary accident (domino effect). V.1.
DETERMINATION OF EFFECT DISTANCES A set of tools for estimating the
effect distances are described in the Technical Appendix [2]. In
order to identify equipment or equipment zone likely to give rise
to a domino effect, the user must, on the plan of the concerned
establishments, locate the geographical position of all the
equipment items or equipment zones, as well as of all the congested
zones. With the exception of the pipes, all the equipment items and
the equipment zones, as well as the congested zones, are located by
their centre. The pipes are located by the both ends of each
segment constituting the pipe. With these data, the user can
calculate the distances between any equipment items or equipment
zones of the different establishments, including congested zones.
Therefore, he can determine equipment or equipment zones likely to
be reached by the effects of the different retained accident
scenarios. All the results of the domino study must be summarized
in the table DOMINO98-L3 (see "processing of the results" in
paragraph 0.V.2.). V.2. PROCESSING OF THE RESULTS The last columns
of the table DOMINO98-L3 can be filled in:
column 9: effect distance associated with each primary effect
related to the different types of accidents (see Technical Appendix
[2]);
columns 10, 11, ... : equipment or equipment zones likely to be
reached by the considered effect according to the distance between
the primary equipment zone and the secondary equipment or equipment
zones considered (external domino effects, one column by external
establishment);
last column: equipment or equipment zones likely to be reached
by the considered effect inside the establishment where the primary
accident occured (internal domino effect).
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VI. STEP 4: DETAILED ANALYSIS OF PAIRS RETAINED DURING THE THIRD
STEP AS LIKELY TO BE INVOLVED IN A DOMINO EFFECT The purpose of the
fourth step is to verify the relevance of pairs of equipment items
or equipment zones selected in the third step as likely to be
involved in a domino effect. Actually, during the third step, the
determination of the effect distances is based on simple and rapid
criteria. This rapidity and this simplicity are obtained with some
approximations and simplifications in the used methods. During this
fourth step, more precise approachs can be envisaged. The user of
the methodology can especially tackle four topics:
a more detailed approach of accidents; a study of aggravating
factors; a study of safety systems and favourable circonstances;
the historical knowledge.
These points are presented in the document giving the principles
of the methodology for studying domino effects [1]. These further
analyses must always be relevant according to scientifically proved
knowledge.
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VII. BIBLIOGRAPHY [1] Delvosalle C., Benjelloun F., Fivez C.
A methodology for studying domino effects. Ministre Fdral de
l'Emploi et du Travail - Administration de la Scurit du Travail -
Inspection technique - (Contrat de gr gr CRC/WPS/07/97) - Facult
Polytechnique de Mons - July 1998.
[2] Delvosalle C., Benjelloun F., Fivez C. Technical appendix
for the application of the methodology for studying domino effects.
Ministre Fdral de l'Emploi et du Travail - Administration de la
Scurit du Travail - Inspection technique - (Contrat de gr gr
CRC/WPS/07/97) - Facult Polytechnique de Mons - July 1998.
[3] Council Directive 96/82/EC of 9 December 1996 on the control
of major accident hazards involving dangerous substances. Official
Journal of the European Communities - 14/01/1997 - N L 10/13 to
10/33.
[4] Rpertoire des produits dangereux - Guide Orange des
Sapeurs-Pompiers Genevois.
Ville de Genve, Service d'Incendie et de Secours, 2me dition.
[5] Levert J.M., Delvosalle C., Anstett P.A., Benjelloun F., Pons
P., Verriest C. Mthodologie d'analyse des effets domino en milieu
industriel - Rapport final -
Ministre de l'Emploi et du Travail - Administration de la Scurit
du Travail - Inspection technique - (Contrat de gr gr
CRC/WPS/07/95) - Facult Polytechnique de Mons - Juillet 1996
[6] Gonzales P. Une problmatique du feu. Institut National de
lEnvironnement Industriel et des
Risques, Verneuil-en-Halatte, France.