-
PREVENTION OF MAJOR ACCIDENTS
GUIDANCE ON COMPLIANCE WITH THE
SEVESO II DIRECTIVE
IGC Doc 60/04/E
Revision of Doc 60/98
EUROPEAN INDUSTRIAL GASES ASSOCIATION
AVENUE DES ARTS 3-5 B 1210 BRUSSELS Tel : +32 2 217 70 98 Fax :
+32 2 219 85 14
E-mail : [email protected] Internet : http://www.eiga.org
-
EIGA 2004 - EIGA grants permission to reproduce this publication
provided the Association is acknowledged as the source
EUROPEAN INDUSTRIAL GASES ASSOCIATION Avenue des Arts 3-5 B 1210
Brussels Tel +32 2 217 70 98 Fax +32 2 219 85 14
E-mail: [email protected] Internet: http://www.eiga.org
IGC Doc 60/04/E
PREVENTION OF MAJOR ACCIDENTS
GUIDANCE ON COMPLIANCE WITH THE
SEVESO II DIRECTIVE KEYWORDS
HAZARD
LEGISLATION
SAFETY
Disclaimer
All technical publications of EIGA or under EIGA's name,
including Codes of practice, Safety procedures and any other
technical information contained in such publications were obtained
from sources believed to be reliable and are based on technical
information and experience currently available from members of EIGA
and others at the date of their issuance. While EIGA recommends
reference to or use of its publications by its members, such
reference to or use of EIGA's publications by its members or third
parties are purely voluntary and not binding. Therefore, EIGA or
its members make no guarantee of the results and assume no
liability or responsibility in connection with the reference to or
use of information or suggestions contained in EIGA's publications.
EIGA has no control whatsoever as regards, performance or non
performance, misinterpretation, proper or improper use of any
information or suggestions contained in EIGA's publications by any
person or entity (including EIGA members) and EIGA expressly
disclaims any liability in connection thereto. EIGA's publications
are subject to periodic review and users are cautioned to obtain
the latest edition.
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IGC DOC 60/04
1
Table of Contents
1
Introduction.......................................................................................................................................
4
2 List of substances and qualifying criteria
.........................................................................................
6 2.1 List of substances particular interest for industrial gases
industry............................................ 7 2.2 List of
substances not specifically
named.................................................................................
8 2.3 Addition of dangerous
substances............................................................................................
9 2.4
Mixtures...................................................................................................................................
12
3 Notification of establishment
..........................................................................................................
13
4 Major Accident Prevention Policy (MAPP) and Safety Management
System (SMS) .................... 14 4.1 Guidance for drawing up a
Major Accident Prevention Policy (MAPP)
.................................. 14
5 Safety
Reports................................................................................................................................
15 5.1
Oxygen....................................................................................................................................
15
5.1.1 Incidents involving liquid oxygen
.....................................................................................
15 5.1.1.1
Background...............................................................................................................
15 5.1.1.2 Liquid Oxygen Venting and Injury to Employee - Canada
(1996) ............................ 15 5.1.1.3 Liquid Oxygen
Release in Residential Area - Philippines
(1993)............................. 16 5.1.1.4 Liquid Oxygen
Release from Cylinder Fixed in a Pallet - France (1992)
................. 16 5.1.1.5 Germany
(1990)........................................................................................................
16 5.1.1.6 Liquid Oxygen Release from ISO Container - UK
(1990)......................................... 16 5.1.1.7 Shooting
of LOX Storage Tank - Colombia
(1989)................................................... 16
5.1.1.8 Liquid Oxygen Release - Car Caught Fire - USA (1989)
......................................... 16 5.1.1.9 Major Spill of
Liquid Oxygen from ASU Storage Tank - USA (1988)
....................... 16 5.1.1.10 Liquid Oxygen Release Near
Welding Shop - Australia (1985) ............................... 17
5.1.1.11 Liquid Oxygen Release from Tank
(1980s)..............................................................
17 5.1.1.12 Liquid Oxygen Release from Storage Tank - UK
(1977).......................................... 17 5.1.1.13
Exploration Survey Ship - Australia
(1970s).............................................................
17 5.1.1.14 Liquid Oxygen Release and the Death of Four
Construction Workers -
USA (1970s)
.............................................................................................................
17 5.1.2 Hazard analysis
...............................................................................................................
17
5.1.2.1 Identification of Substances and Safety
Data........................................................... 17
5.1.2.2 Fires and Explosions
................................................................................................
17 5.1.2.3 Cryogenic temperatures
...........................................................................................
18 5.1.2.4 Overpressure effects
................................................................................................
18 5.1.2.5 Fog
formation............................................................................................................
18 5.1.2.6 Environmental effects
...............................................................................................
19 5.1.2.7 Vessel
rupture...........................................................................................................
19
5.1.2.7.1 External impact
.....................................................................................................
19 5.1.2.7.2 Natural
events.......................................................................................................
19 5.1.2.7.3 Sabotage
..............................................................................................................
19 5.1.2.7.4 Design/manufacturing fault
...................................................................................
19 5.1.2.7.5
Over-pressure.......................................................................................................
20 5.1.2.7.6 Other events
.........................................................................................................
20
5.1.2.8 Consequence Analysis
.............................................................................................
21 5.2
Acetylene.................................................................................................................................
21
5.2.1 Incidents involving acetylene
...........................................................................................
21 5.2.1.1 Explosion in a neutralisation vessel, Germany,
1996............................................... 21 5.2.1.2 Fire
in a generator, Colombia,
1995.........................................................................
21 5.2.1.3 Fire in the devalving station, Norway, 1994
............................................................. 21
5.2.1.4 Fire/explosion in filling area, Australia
......................................................................
21 5.2.1.5 Explosion in a generator, Germany,
1990................................................................
21 5.2.1.6 Decomposition, explosions in compressor and filling
ramps, Spain, 1989 .............. 22 5.2.1.7 Decomposition,
explosion, fire in a compressor, Portugal, 1989
............................. 22 5.2.1.8 Decomposition: Detonation
in a piping system, Spain, 1988 ...................................
22
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5.2.1.9 Fire in the devalving area, Belgium, 1982
................................................................ 22
5.2.1.10 Decomposition, explosion, fire in a filling station,
Venezuela, 1979......................... 22 5.2.1.11 Fire in a
drier battery, Sweden, 1979
.......................................................................
22 5.2.1.12 Deflagration in carbide dust exhausting system,
Germany, 1978............................ 22 5.2.1.13 Explosion,
fire in the dust separator, generator, Germany,
1977............................. 22 5.2.1.14 Explosion of a
gasholder after decomposition, Denmark,
1974............................... 22
5.2.2 Hazard analysis
...............................................................................................................
22 5.2.2.1 Fire / Explosion
.........................................................................................................
23 5.2.2.2 Decomposition / Explosion
.......................................................................................
23
5.2.2.2.1 Gaseous acetylene
...............................................................................................
23 5.2.2.2.2 Liquid
acetylene....................................................................................................
24 5.2.2.2.3 Solid acetylene
.....................................................................................................
24
5.2.2.3 Other hazards of acetylene
......................................................................................
24 5.2.2.4 Solvent
spill...............................................................................................................
24 5.2.2.5 Calcium carbide
........................................................................................................
24 5.2.2.6 Discussion of failure cases
.......................................................................................
24
5.2.2.6.1 External events:
....................................................................................................
24 5.2.2.6.2 Sabotage /
Vandalism...........................................................................................
25 5.2.2.6.3 Design / Construction
fault....................................................................................
25 5.2.2.6.4 Internal events
......................................................................................................
25
5.2.2.7 Consequence analysis
.............................................................................................
26 5.2.2.7.1 Loss of containment of acetylene from the process:
............................................ 26 5.2.2.7.2 Explosion
within process equipment
....................................................................
27 5.2.2.7.3 Cylinder rupture
....................................................................................................
27 5.2.2.7.4 Solvent
spill...........................................................................................................
28
5.2.2.8 Specific safeguards in acetylene production
............................................................ 28
5.2.2.8.1 Emergency shutdown
systems.............................................................................
28 5.2.2.8.2 Flame arrestor
......................................................................................................
28 5.2.2.8.3 Venting systems
...................................................................................................
28
5.2.2.9 Storage and handling of calcium carbide
.................................................................
28 5.2.2.9.1 General
.................................................................................................................
28 5.2.2.9.2 Calcium carbide store
...........................................................................................
28
5.2.2.10 Acetylene generation and cylinder filling
..................................................................
29 5.2.2.10.1 Acetylene generators - general
..........................................................................
29 5.2.2.10.2 Generator systems
.............................................................................................
29 5.2.2.10.3 Gasholder
...........................................................................................................
30 5.2.2.10.4 Operation and maintenance of generator and
gasholder................................... 30 5.2.2.10.5
Purification
..........................................................................................................
31 5.2.2.10.6 Compressors
......................................................................................................
31 5.2.2.10.7 Drying
system.....................................................................................................
32 5.2.2.10.8 Filling station equipment, cylinders and storage
................................................ 32
5.3 Specialty gases
.......................................................................................................................
33 5.3.1 Incidents involving specialty
gases..................................................................................
33
5.3.1.1 Ammonia valve incident, UK,
1994...........................................................................
33 5.3.1.2 Rupture of flexible rubber hose, Italy,
1994..............................................................
33 5.3.1.3 Vacuum pump over-pressurised, UK, 1993
............................................................. 33
5.3.1.4 Fluorine fire, Belgium,
1993......................................................................................
33 5.3.1.5 Arsine release, Belgium,
1993..................................................................................
33 5.3.1.6 Gas escape, Germany,
1988....................................................................................
34 5.3.1.7 Burns from hydrogen fluoride drum, Belgium,
1986................................................. 34 5.3.1.8
Connection leak, UK,
1986.......................................................................................
34 5.3.1.9 Flame in cylinder preparation area, Belgium,
1985.................................................. 34
5.3.2 Hazard analysis
...............................................................................................................
34 6 Emergency
plans............................................................................................................................
34
6.1 Internal emergency
plans........................................................................................................
35 6.1.1 Introduction
......................................................................................................................
35 6.1.2 Consultation
.....................................................................................................................
35 6.1.3 Basis for external emergency plan
..................................................................................
35 6.1.4 Changes of risk
................................................................................................................
35
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6.1.5 Basis of plan
....................................................................................................................
35 6.2 External emergency
plans.......................................................................................................
38
6.2.1 Introduction
......................................................................................................................
38 6.2.2 Duties of the operator
......................................................................................................
38 6.2.3 Requirements for external emergency
planning..............................................................
38
6.3 Rehearsal of the emergency plans
.........................................................................................
38 7 Information to the public
.................................................................................................................
39
7.1 Guidelines for installations falling under Article 13.1
.............................................................. 39
7.2 Safety Reports
........................................................................................................................
39
8 Land use planning
..........................................................................................................................
39
9 Reporting of major
accidents..........................................................................................................
40 9.1 Information to be supplied by the
Operator.............................................................................
40 9.2 Information to be supplied by the Competent Authority to the
Commission........................... 40
ANNEX A - Council
Directives...............................................................................................................
42
ANNEX B - EIGA List of Substances / Qualifying
Contents..................................................................
72
ANNEX C - IGC-Reference Documents / Supporting Literature
........................................................... 77
ANNEX D - Catastrophic failure statistics for cryogenic storage
tanks ................................................. 79
ANNEX E - Consequence analysis
examples.......................................................................................
81
ANNEX F- Public Information Examples
...............................................................................................
97
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1 Introduction
Directive 96/82/EC amended by 2003/105/EC on the control of
major accident hazards involving dangerous substances The purpose
of this document is to give guidance to EIGA members and their
customers on the "Seveso II" directive which became effective on 3
February 97. An amendment 2003/105/EC was published previously.
Therefore this document was updated. The main change is an adaption
in the interpretation of the addition rule in paragraph 2.3 /
example 4. Note: Text taken directly from the directive is shown in
italics. Specific notes or comments for EIGA members are in bold
print. The numbering and content of most of the Articles have
changed, and some additional requirements have been included. The
main changes are as follows: Article 2 A clearer definition of
establishments and installations falling under the requirements
with
selection based mainly on classes of dangerous substances with 2
threshold levels. Article 6 Notification is required based on the
quantity of substance on the establishment not the type
of process (the previous Annex 1 has been deleted). Article 7
All establishments are required to produce a Major Accident
Prevention Policy (MAPP)
document and ensure it is properly implemented. Article 8
Competent Authorities are required to take necessary steps for the
exchange of information
between neighbouring hazardous installations where there is a
possibility of domino effects. Article 9 A clearer definition of
the contents of a safety report for upper tier major hazard sites
with a
requirement for feedback from the Competent Authority "within a
reasonable period of receipt of the report".
Article 11 There is now an annex describing the contents of the
emergency plan (Annex IV). Internal
and external emergency plans must be reviewed and tested at
least every 3 years. Article 12 Competent Authorities are required
to properly take account of hazards in land use planning. Article
13 The safety report must be made available to the public, amended
to exclude confidential
information. Article 15 A clearer definition of which major
accidents need to be reported by the Competent Authority
to the Commission, in particular environmental incidents.
Article 18 Competent Authorities are required to make on site
inspections of upper tier establishments.
The inspection will either be to a programme based on the hazard
or at least once per year. EIGA WG-3 has reviewed and commented on
each draft of the new legislation direct to DGXI and has supported
the changes in the legislation. In particular the setting of
thresholds for categories of substances and preparations based on
the hazardous properties and therefore consequences of an accident
is more rigorous and fairer than a list of substances. The number
of named substances has therefore reduced, and also the qualifying
quantity for arsine and phosphine has increased to 200kg (lower
tier) and 1T (upper tier). Chlorine, Fluorine, Hydrogen, Hydrogen
Chloride, Acetylene, Ethylene Oxide, Propylene Oxide and Oxygen
remain unchanged whereas the lower tier for Phosgene has reduced to
300kg. Other industrial gases and mixtures are covered by generic
classes (eg. toxic) as determined by the classification, packaging
and labelling
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IGC DOC 60/04
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directive 88/379/EEC. Guidance with examples on how to calculate
whether your installation exceeds the lower or upper tier
thresholds is given in this document. It should be noted that DGXI
has published some guidance notes on the content of the safety
report, safety management systems and the MAPP which is useful.
This document will supplement this with specific guidance for
storage and operations involving industrial gases. A flowchart for
applying the directive is given in Fig 1. A copy of the Seveso II
directive is given in Annex A of this document. Figure 1 Flowchart
for the Application of the SEVESO II - Directive
Any substance thresholdquantity of column 3
**Add Substances > 2 % Col. 3using formula given in Annex
1,
Note 4 and using Col. 3 thresholds
Establishment / installation doesnot fall under the
regulations
of the Directive
Definition: see Art. 3,No. 1 , No. 2 , No. 4 Are dangerous
substances on establishment/ installation ?
Articles 6: Notification 7: Major accident prevention policy
apply
Sum 1
1 substance
*Determine the maximum quantities of dangerous substanceswhich
are present or are likely to be present at any one time
> 1 substance
Directive does not apply
Articles 9: Safety Report,
11: Emergency Plans13: Information on Safety Measures apply
Add Substances using formulagiven in Annex 1,
Note 4 and using Col.2 thresholds
Sum 1
no
no
yes
threshold quantityof column 3
threshold quantityof column 2
threshold quantity of column 2 threshold quantity of column
3
no
yes
yes
yes
no
Notes to Figure 1: *) Do not include substances with quantities
2% of Column 2 which cannot act as an initiator of
a major accident on the site (Ref: Annex A, Introduction No 4).
**) Do not include substances with quantities 2% of Column 3 which
cannot act as an initiator of
a major accident on the site.
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2 List of substances and qualifying criteria
One of the most essential parts of the Seveso II directive are
the annexes which list the dangerous substances and the threshold
levels at which different controls apply. In order to assist EIGA
members in using the directive, tables have been prepared including
the substances which are of particular interest to the industrial
gases industry. In the Seveso II directive there are some changes
in the lists of dangerous substances. Quite a few substances have
been removed from the list, some threshold values have changed and
the different threshold values for storage vs. production is now
removed. The quantities listed are the maximum quantities which are
present or are likely to be present at any one time. The more
generic list of substances not specifically named, originally
described in the amending Directive 82/501/EEC from 1988, has been
revised and extended. In this guidance both old and new values are
listed to simplify a view over any differences. Note: EIGA members
should refer to their own national regulations to ensure that the
details are correct for their particular case at the time of use.
This is necessary as the definitions and conditions which are the
basis of the threshold quantities can vary between different
countries and the Directive. The reason for this is that the
Directive allows member states to impose stricter requirements with
lower quantities. No national regulations have been listed as in
the previous IGC TN 502/86E, as they were not available at the time
of writing this document. The qualifying rules for adding
substances are shown and illustrated with examples at the end of
this chapter.
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IGC DOC 60/04
7
Substance according to Annex I, Part 1 in Seveso II
directive
Chemical formula, (Category in Part 2)
Lower tier Article 6+7
(tonnes)
Upper tier
Article 9 (tonnes)
Seveso I Lower tier Article 3+4
storage/production
(tonnes)
Seveso I Upper tier Article 5
storage/production
(tonnes) Acetylene C2H2
(8) 5 50 5/-- 50/50
Arsenic trihydride (arsine) AsH3 (1) (8)
0.2 1 --/-- --/0.01
Carbonyl dichloride (phosgene)
COCl2 (1)
0.3 0.75 0.75/-- 0.75/0.75
Chlorine Cl2 (2)
10 25 10/-- 75/25
Ethylene oxide C2H4O (8) (2)
5 50 5/-- 50/50
Hydrogen H2 (8)
5 50 5/-- 50/50
Hydrogen chloride (liquefied gas)
HCl (2)
25 250 25/-- 250/250
Liquefied extremely flammable gases (LPG, natural gas etc)
CxHy (8)
50 200 50/-- 200/200
Oxygen O2 (3)
200 2000 200/-- 2000/2000
Phosphorous trihydride (phosphine)
PH3 (1) (8)
0.2 1 --/-- --/0.1
Propylene oxide C3H6O (8) (2)
5 50 5/-- 50/50
2.1 List of substances particular interest for industrial gases
industry
The following substances were previously named in Seveso I
directive and the IGC TN 502/86/E, but are now removed from the
Seveso II directive. However, they fall into categories in the list
of not specifically named substances. Hydrogen sulphide H2S
Hydrogen cyanide HCN Carbon disulphide CS2 Ammonia NH3 Stibine
SbH3 Methyl bromide CH3Br Nitrogen oxides NxOy Hydrogen fluoride HF
Nickel tetra carbonyl Ni(CO)4 Oxygen difluoride OF2 Sulphur dioxide
SO2
The risk classes of the substances listed above are given in a
more extensive list of substances for the industrial gas industry
in Annex B of this document.
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IGC DOC 60/04
8
2.2 List of substances not specifically named
Unnamed substance according to Annex I, Part 2 in Seveso II
directive
Lower tier Article 6+7
(tonnes)
Upper tier Article 9 (tonnes)
EIGA Example
1. Very toxic
5 20 NO2
2. Toxic
50 200 SO2
3. Oxidizing
50 200 NF3
4. Explosive - a substance/preparation which creates risk of
explosion by chock, friction, fire or other source of ignition
(risk phrase R2) - a pyrotechnic substance - an explosive
pyrotechnic substance
50 200 --
5. Explosive - a substance/preparation which creates extreme
risk of explosion by chock, friction, fire or other source of
ignition (risk phrase R3)
10 50 --
6. Flammable - substances and preparations having a flash point
> 21oC and
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IGC DOC 60/04
9
Note: Article 6 + 7 relates to notification requirements,
Article 9 to issuing safety reports, and other
requirements. In the case of substances and preparations with
properties giving rise to more than one
classification, for the purpose of this Directive the lowest
threshold shall apply. One example is Carbon monoxide, CO, which
falls under category 2 (toxic) and 8 (extremely flammable). As the
limits of category 8 are 10 tonnes (lower tier) and 50 tonnes
(upper tier) as the qualifying quantities compared to the
respective 50 tonnes and 200 tonnes for category 2, the threshold
limits of category 8 shall be used.
Some of the industrial gases, eg. N2, Ar etc, are defined as
non-toxic and do not fall under the Directive.
Calcium Carbide does not fall under the directive. 2.3 Addition
of dangerous substances
If the amounts of substances are such that the establishment is
not immediately covered by the directive, it may be necessary to
add the amounts of substances and compare with threshold quantities
to determine if the directive applies or not. The rules for
addition are described through a number of examples. When
summarising dangerous substances named or not specifically named,
the substances present in quantities less or equal to 2% of the
qualifying quantities in Part 1 or Part 2 shall normally not be
included. This is to facilitate the work to see whether an
establishment qualifies or not. The exception is if the small
quantity is located in such a way that the substance may act as an
initiator of a major accident elsewhere on the establishment. It is
difficult to give specific guidance on this exception. The
exclusion of substances should be made when it is fairly obvious
that there is no possibility of acting as an initiator. In cases
not as evident, some kind of hazard assessment will be needed in
order to determine whether the substance may be excluded or not. As
an example oxygen tanks/containers with less than 2% of 200 tonnes
= 4 tonnes, should not be included in the lower tier notification
calculation. Similarly, less than 40 tonnes should not be included
in the calculation for upper tier (Article 9). This rule could also
be applied to cylinders, e.g. containing small amounts of toxic
gases etc. Finally, note that transportation is not covered by the
directive, which means that quantities temporarily present in road
or railroad tankers (eg. during loading/unloading) should not be
included, independent of the amounts. Note: EIGA members should
consult their competent authority to confirm if temporary storage
also includes overnight or longer periods of parking of the
vehicles. Addition shall also be used when named or not
specifically named substances from categories 1, 2, and 9 in Part 2
are present at the same establishment, i.e. toxic, very toxic
substances and substances dangerous for the environment, or when
named or not specifically named substances from categories 3, 4, 5,
6, 7 and 8 in Part 2 are present at the same establishment, i.e.
oxidising, explosive, flammable, highly flammable and extremely
flammable substances. The addition of dangerous substances shall be
carried out according to a simple formula:
(1) 1 2 3q
+q
+q
+. . . > 11 2 3Q Q Q
where q equals the quantity of the named substance in Part 1
(partly described by table of named substances) or unnamed
substances in Part 2 (described in table for substances not
specifically named above), and Q equals the threshold value in Part
1 or 2. If the value is >1 then the establishment is subjected
to the Seveso II Directive. Note that the sum may be based on the
upper or lower tier values (Q) and depending on which sum exceeds
1, Article 6 + 7 or Article 9 will apply.
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IGC DOC 60/04
10
Note: These examples comply with the intent of the directive but
according to the letter of the text named substances in Part 1 from
different categories need not be added together. Guidance should be
obtained from the competent authority in this case. Example 1
Oxid.
Sum
Flam.+
O2LPG H2
An establishment has an Air Separation Unit which feeds an
oxygen pipeline as well as providing some liquid oxygen for tanker
deliveries. Back-up for the pipeline is provided by storage of
liquid oxygen, pumps and a vaporiser fuelled by LPG. Also at the
establishment is a storage facility for liquid hydrogen which is
imported and delivered by tankers. The maximum inventories at the
establishment of each of these materials named in Annex 1 are:
Oxygen 1400 tonnes, LPG 40 tonnes, Hydrogen 8 tonnes. This
establishment has lower tier quantities for oxygen and hydrogen,
and so Articles 6 & 7 apply. When the rule of addition is
applied using the threshold values for article 9:
14002000
40200
850
106+ + = . Article 9 therefore applies to this establishment. NB
Under the previous directive this site would have been lower
tier as oxidising material was not added to flammable
material.
Example 2
Verytoxic
Sum
Verytoxic
+
HCNCOCl2
An establishment have only approximately 200 kg of Carbonyl
dichloride (phosgene) and 400 kg of Hydrogen cyanide on the site.
The first of the two substances is in the named substances list
(Part 1) and the second is not, which instead is covered by the
same class in the unnamed substance list (Part 2), very toxic. The
rule of addition to apply is:
0 20.3
0 45
0 75. .
.+ = The threshold values used are those for article 6+7 and the
value is less than 1. Using the threshold values of article 9 would
result in an even lower sum, which means that neither article 6+7
nor 9 of the directive applies.
Example 3
Oxid.
Sum
Toxic+
SO2O2
An establishment have 180 tonnes of Oxygen and 9 tonnes of SO2
on the same site. Both substances are on the named substances list,
but in quantities below the lower tiers, which are 200 and 10
tonnes. In this case the rule of addition do not apply, since the
two substances are of different categories that should not be
added, i.e. toxic and oxidizing, or category 2 and 3
respectively.
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IGC DOC 60/04
11
Even if the application of the addition rule in the case of
substances and preparations with properties giving rise to more
than one classification has not been considered in the same way by
all the national competent authorities, double classified
substances should be included in both the additions: first added to
the other eventual substances of groups 3, 4, 5, 6, 7,and 8
(oxidable, explosive and flammable substances) and then added to
the other eventual substances of group 1, 2 and 9 (toxic and
dangerous for the environment) using the threshold limits of the
respective categories. EIGA members should consult their competent
authority or consultants to verify the national application of the
addition rule in case substances and preparation with properties
giving rise to more than one classification are presents in an
establishment. Example 4
Oxid.
Sum
Flam.+
O2 LPG CO AsH3
Verytoxic
Sum
Oxid.
Sum
Flam.+
O2 LPG CO AsH3
Verytoxic
Sum
Verytoxic+
An establishment have Oxygen, LPG, Carbon monoxide and Arsine on
the same site. The quantities are 180, 4, 8 tonnes and 900 kg
respectively. The threshold quantities are Oxygen 200 t (low) /
2000 t (high) LPG 50 t (low) / 200 t (high) AsH3 (Arsine) 0,2 t
(low) / 1 t (high) Carbon monoxide is considered a toxic (Category
2) and extremely flammable (Category 8) gas for which the
corresponding limits are: Carbon monoxide 50 t (low) / 200 t (high)
as toxic 10 t (low) / 50 t (high) as extr.flamm as specified at the
note 1 of Annex I, Part 2 of the Directive ( In the case of
substances and preparations with properties giving rise to more
than one classification, for the purpose of this Directive the
lowest thresholds shall apply ) the threshold limit quantities for
CO to be considered are therefore 10 t and 50 t. The addition rules
for the categories 3, 4, 5, 6, 7a, 7b, 8 of Annex I, Part 2 are:
lower tier
78.110
)(850
)(4200
)(180 =++ COLPGOxygen , higher tier
27.0508
2004
2000180 =++ ,
which shows that the site is a lower tier site for oxidable,
explosive and flammable substances. The addition rules for the
categories 1, 2 and 9 of Annex I, part 2 will be: for lower tier
values
66.42.0
)3(9.050
)(8 =+ AsHCO for higher tier values
94.019.0
2008 =+
which shows that the site is also a lower tier site for toxic
and dangerous substances for the environment.
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2.4 Mixtures
Annex I of the Directive states that mixtures or preparations
where substances on the named or unnamed list are included,
generally shall be treated as pure substances provided they remain
within the concentration limits are such that their properties
(e.g. flammable, toxic, explosive etc) still are expressed.
Additional guidance may be found in the directives covering
classification, packaging and labelling of dangerous preparation
(67/548/EEC and 88/379/EEC). These references are given in the
Seveso II directive. An example is a mixture of arsine in nitrogen.
If the percentage composition is marked on the cylinder and the
mixture is greater than 1% arsine, then the classification is still
very toxic and the percentage arsine should be used in the
calculation against the relevant arsine threshold (0.2, 1T). Below
1%, the property changes to toxic and the entire contents of the
mixture should be used in the calculation against the toxic
category thresholds (50 and 200T). It may be simpler and acceptable
to the competent authority to take the entire contents of the
cylinder as a very toxic gas for mixtures over 1% arsine content
against the very toxic category thresholds (5 and 20T).
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3 Notification of establishment
The notification to the competent authorities as required by
Article 6 of the Directive has to be done within the following time
limits:
For new establishments a reasonable period of time prior to the
start of construction or operation.
EIGA suggests to do the notification together with the request
for the operating permit and/or together with the start-up of the
construction of the concerned establishment.
For existing establishments one year from the date laid down in
Article 24(1), = not later than 24 months after its entry into
force: 24 February 97.
Before 24 February 2000 Note: The competent authority may define
different periods according to national legislation. In case of an
existing establishment for which all the necessary information has
already been provided, a new notification may not be required. The
total product quantities comprise the maximum storage capacity plus
product inside the plant during operation. All dangerous substances
need to be considered in the notification. (a) The name or trade
name of the operator and the full address of the establishment
concerned. (b) The registered place of business of the operator,
with the full address. (c) The name or position of the person in
charge of the establishment, if different from (a). (d) Information
sufficient to identify the dangerous substances or category of
substances involved. Example for oxygen: Oxygen, O2, is an oxidiser
and named substance in annex A, part 1. Oxygen is not flammable
itself nor will a higher oxygen content in the air endanger human
life. An enriched oxygen atmosphere will increase fire risk of
combustible materials and may lead to fire. Example for acetylene:
C2H2, is classified as extremely flammable, and a named substance
in annex A, part 1. Example for specialty gas: Arsine, AsH3 is a
named substance in annex 1, part 1 and classified as very toxic and
extremely flammable. Reference material safety data sheet. (e) The
quantity and physical form of the dangerous substance or substances
involved. Example for oxygen: State maximum quantity of oxygen,
liquid and gaseous form. Example for acetylene: State maximum
quantity of acetylene in gaseous and dissolved form. State solvent
used and quantity. Calcium carbide is not a dangerous substance
under this directive but the quantity stored should be stated.
Example for specialty gas: State maximum quantity of arsine in pure
form and/or mixtures. State arsine is a gas.
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(f) The activity or proposed activity of the installation or
storage facility. Example for oxygen: Air is compressed and cooled
down below its liquefaction temperature and then separated into its
main components nitrogen, oxygen and argon by distillation. Liquid
oxygen LOX, liquid nitrogen LIN and liquid argon LAR are stored in
large-capacity tanks at a slight overpressure ready for liquid
transport. Gaseous oxygen GOX, nitrogen GAN and argon GAR are
compressed to final consumer pressure, and supplied by pipeline.
Example for acetylene: Acetylene is generated by the chemical
reaction between calcium carbide and water in a generator. The gas
is purified, compressed and charged into acetylene cylinders where
it is dissolved into a solvent. Example for specialty gas: The
facility comprises storage and compression equipment for the
purification and mixing of toxic, flammable and oxidising gases for
filling into cylinders. There is a disposal system for residuals,
purge gas and waste. Note: Competent authorities may request
further information, eg. a simplified flowsheet. (g) The immediate
environment of the establishment (element liable to cause a major
accident or to aggravate the consequences thereof). Simple map(s)
of establishment and its surroundings. Show on the map or describe
separately: - location of dangerous substances on the
establishment, - neighbouring activities, installations, storage
areas, - transportation networks, roads, railways, canals,... -
areas of environmental importance, woods, lakes,... - areas of
population, schools,
4 Major Accident Prevention Policy (MAPP) and Safety Management
System (SMS)
Article 7 of the Seveso II Directive requires the operator of a
major hazard establishment to "draw up a document setting out his
major accident prevention policy and to ensure that it is properly
implemented. The major accident prevent policy established by the
operator shall be designed to guarantee a high level of protection
for man and the environment by appropriate means, structures and
management systems".
4.1 Guidance for drawing up a Major Accident Prevention Policy
(MAPP)
The MAPP is a short document (typically 1 or 2 pages) which sets
down the objectives and responsibilities for the safe operation of
a major hazard establishment and outlines the organisation and
arrangements that are implemented through a safety management
system (SMS); that implementation requests a set of working
documents. The MAPP would be at the top of a hierarchy of
documentation which would increase in detail and specificity
through down the hierarchy. Many operators will have an overall
SMS. If this existing policy already includes the requirements of
the MAPP, then no further document should be necessary. If an
existing safety policy does not include the specific MAPP
requirements then the operator can add a separate document which
includes those MAPP requirements.
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For top tier establishments the MAPP document may be included in
the safety report (Article 9 of the Directive). For low tier
establishments the document shall be available as soon as the
Directive enters into force in each country. An operator with
several major hazard establishments could have one general MAPP
that applies to all those establishments. The operator may also
have one SMS that is common to all his establishments. However, the
detail of how the policy and management are implemented at each
separate installation will be specific to each installation. The
MAPP doesn't need to describe the SMS in detail but should indicate
that the systems cover in particular: - organisation and personnel
- major hazards identification and evaluation - operational control
- management of change - planning for emergencies - monitoring
performance - audit and review Refer to reference 12 (Annex C) for
more information on the points. The MAPP and the SMS must be
periodically revised by the management to ensure that safety
performances reach the objectives defined.
5 Safety Reports
It is recommended that the guidance given in Annex D of this
document is followed for preparing the safety report. Specific
guidance for oxygen, acetylene and specialty gases for inclusion in
the safety report is given below.
5.1 Oxygen
5.1.1 Incidents involving liquid oxygen
The following incidents are recorded in the EIGA database. It is
recommended that all these incident summaries are not repeated in
the safety report but this document should be referenced.
5.1.1.1 Background
The following incidents all involve the release of large amounts
of liquid oxygen and the descriptions are intended to highlight the
consequences of these types of releases. There have been serious
accidents involving gaseous oxygen but these have involved confined
spaces. Eight men died during construction of a nuclear destroyer
(HMS Glasgow) in 1976. Oxygen leaked into a compartment of the ship
and when a welding arc was struck, an intense fire started. A
similar incident occurred in the Netherlands in 1994 resulting in 2
fatalities. IGC 8/76 and 4/93 should be consulted for prevention
advice.
5.1.1.2 Liquid Oxygen Venting and Injury to Employee - Canada
(1996)
Out of specification, liquid oxygen was being vented through a
disposal stack when it ran along the ground and entered a control
room. As an employee entered the building, he quickly became
engulfed in flames, and although several fire extinguishers were
used on him, it was almost impossible to put out the flames. The
flames started around the legs of the employee and most of the burn
injuries were below waist level.
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5.1.1.3 Liquid Oxygen Release in Residential Area - Philippines
(1993)
A liquid oxygen tank that was located in a building was being
filled from a tanker. The brazed connection from the valve to the
tank failed and 13-tonne of liquid oxygen were released into the
building, which had several openings. The cold oxygen vapours
exited from the building and flowed down walled streets into an
area where there were food stalls and open fires. Members of the
public were smoking and one person reported seeing sparks on his
feet as he entered his vehicle to start it. Another person's
clothing went on fire, but they managed to douse the flames in the
local canal. One person was burned, mainly on the lower parts of
the body. An administration building was burned down and also a
vehicle.
5.1.1.4 Liquid Oxygen Release from Cylinder Fixed in a Pallet -
France (1992)
A 160 litre liquid cylinder fixed in a pallet was positioned in
front of an oxygen tank by a fork lift driver and connected to the
tank by a flexible hose. The next day another driver reversed the
fork lift and the pallet came back with it, the hose pulling out
the valves and the copper tube on the tank. No injuries to
personnel but 22,000 litres of LOX spilled onto the ground and
formed a large cloud. Small damage to a refrigerator unit occurred
even though all power supplies were cut immediately.
5.1.1.5 Germany (1990)
A liquid oxygen rail car was being filled from a large storage
tank in an air separation plant. The liquid oxygen was transferred
from the storage tank to the rail tanker by hose. Because of the
distance, two hoses were connected together to achieve the suitable
length filling hose. After filling had commenced, it was seen that
the connection between the two hoses was not completely leak tight
and during the filling process LOX escaped into the groove of the
rail line close to a point where the rails were connected together
by screwed fish plates. Approximately three meters of the rail were
frozen and due to the contraction of the rail the bolts connecting
the rail and fish plates together ruptured and an explosion
occurred. The pavement stones and parts of the rail connection were
ejected to distances over 100 meters away, but fortunately no-one
was injured. The investigation revealed that while the surface of
the roadway around the rails was reasonably clean, below the
surface the bolts which connected the fish plates to the rails were
lubricated with a black hydrocarbon grease. The source of ignition
was most likely the rupturing bolts which ignited the black
grease/LOX mixture.
5.1.1.6 Liquid Oxygen Release from ISO Container - UK (1990)
A 20 tonne ISO container had just been filled when the hose
connection to the tank became detached, and the contents of the ISO
container were released into the atmosphere. There were no injuries
or damage reported.
5.1.1.7 Shooting of LOX Storage Tank - Colombia (1989)
A terrorist rocket was fired at a flat bottom vertical type
storage tank perforating the outer and inner vessels with a hole 6
x 7cm2. Approximately 14,000 litres of LOX were leaked from the
inner tank mainly to the area between the inner and outer tank. The
outer tank froze but the ice had melted some 14 hours after the
incident and no cracks were found on the outer vessel. There were
no injuries. A nearby LIN tank was perforated by 5 bullets from a
rifle but the inner tank was not damaged.
5.1.1.8 Liquid Oxygen Release - Car Caught Fire - USA (1989)
A 3 position valve at a road tanker loading facility was turned
to manual mode and instantly discharged oxygen onto the ground. The
fill valve was closed but LOX spilled onto the roadway. A
contractor's vehicle drove through the LOX and the car stalled.
When the contractors attempted to restart the engine a flash
occurred. The car caught fire and was subsequently destroyed. There
were no injuries.
5.1.1.9 Major Spill of Liquid Oxygen from ASU Storage Tank - USA
(1988)
A major spill of liquid oxygen occurred from an ASU storage
tank. The carbon steel bolts which held the bonnet of a gate valve
had corroded due to the sea air and the complete topworks,
valvestem and
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wedge of the 3 inch gate valve was ejected from the valve body.
The entire contents of the tank was spilled over a 12-13 hour
period. No-one was injured but considerable property losses
occurred. Secondary effect of 1.2m below gravel installed firewater
line froze up and ruptured.
5.1.1.10 Liquid Oxygen Release Near Welding Shop - Australia
(1985)
A liquid oxygen tank was parked on a sharp incline, filling a
customer tank. The tanker driver built up the pressure in the
tanker using the pressure raising coil, but unfortunately the
vapour vent in the tanker was now below liquid level because of the
slope. Liquid began to run from the vent down the sharp incline and
below the shutter doors of a small engineering company. Two
employees in the shop were conducting braising/welding operations
and both died from injuries sustained when their clothing caught on
fire.
5.1.1.11 Liquid Oxygen Release from Tank (1980s)
A road tanker pulled away from the tank while still connected,
and the pipework was damaged. The total contents of the tank were
released, but the gas dispersed safely and there were no
injuries.
5.1.1.12 Liquid Oxygen Release from Storage Tank - UK (1977)
A cylinder filling pump suction hose was disconnected for pump
repair access; one valve isolated the contents of a LOX tank from
the open end of the hose. The actuation thread on the valve
"stripped" causing the valve to fail to the fully open position.
Approximately 11 tonne of LOX were released. An extensive vapour
cloud resulted. Traffic in an adjacent railway line was halted and
the site evacuated. There were no injuries or fatalities.
5.1.1.13 Exploration Survey Ship - Australia (1970s)
A liquid oxygen road tanker was filling a tank on the deck of a
survey ship when there was a leak at the hose connection to the
tank. Liquid oxygen was released onto the deck of the ship and
subsequently found its way through the deck surface into the holds
of the ship. The ship quickly became engulfed in flames and
subsequently sank. There were no injuries.
5.1.1.14 Liquid Oxygen Release and the Death of Four
Construction Workers - USA (1970s)
A large flat-bottom nitrogen tank was over-pressurised and the
single pressure relief valve did not operate properly because of
icing. The walls and sides of the tank became detached from the
base and subsequently came to rest on the ground after it had
severed a 6-inch liquid oxygen line on a neighbouring tank. The
site and a neighbouring site, which was under construction, were
evacuated but four people from the neighbouring site re-entered the
site before all the liquid oxygen had dispersed. Their car caught
fire and all four were burned to death.
5.1.2 Hazard analysis
The major accident hazard is the oxygen enrichment of the
atmosphere resulting from a large spillage of liquid oxygen.
Therefore the hazard analysis is focussed on the effects of oxygen
enrichment and how this event could occur. Other hazards of oxygen
are given for general information.
5.1.2.1 Identification of Substances and Safety Data
Include safety data sheets for liquid oxygen and other hazardous
substances present on the site, eg. propane storage, ammonia for
refrigeration etc.
5.1.2.2 Fires and Explosions
Effect of oxygen concentration on burning of materials: In
either the liquid or gaseous states, oxygen itself does not burn,
but readily supports combustion of other materials. The way in
which common materials burn in air is well known, but when the
oxygen
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concentration is increased materials will burn more rapidly. The
hazard of increased oxygen concentration is only realised when a
fuel supply and a source of ignition are present. For the general
public, the fuel most likely to be sufficiently close to them to
cause injury is their flammable clothing and body hair and the most
likely ignition source is a lighted cigarette. Oxygen enriched
atmospheres increase the fire hazard of materials by:
decreasing ignition energy
increasing rate of burning
increasing spread of fire. Further information on the effect of
oxygen enrichment on the burning characteristics of cloth materials
can be found in Appendix 1 of reference 1 (Annex C). In general,
the effects of oxygen enriched atmospheres on burning rate, ease of
ignition and fire spread on materials are slight at approximately
25% oxygen, significant by 40% oxygen and near to their maximum at
about 50% oxygen. It is normal practice to consider atmospheres
below 25% as not presenting a hazard. For the purposes of risk
assessment 25% and 40% contour lines should be drawn around a
potential leakage point. The area within the 40% contour should be
treated as a high risk area and the area beyond the 25% contour
should be discounted. The area between the 25% and 40% contours
should be assessed relevant to the local environment. Further
information on this topic can be found in Appendix 3 of reference 1
(Annex C). Oxygen - metal fire: Most metals will burn in oxygen if
ignited. The ease of ignition is dependent on the oxygen pressure
and the material. This reaction could occur in the process pipework
or compression equipment and result in a release of oxygen, molten
metal and a shock wave. Further information can be found in
reference 3. Reactions of liquid oxygen: The combination of liquid
oxygen and combustible materials (eg. hydrocarbons) can result in
an explosion. Further information can be found in reference 4
(Annex C).
5.1.2.3 Cryogenic temperatures
At temperatures below -40C, there is a risk to people exposed to
cryogenic vapours in their effect on skin, eyes and respiratory
system. Details of injuries and appropriate medical treatment can
be found in the safety data sheets. All equipment normally in
contact with cryogenic temperatures is designed in appropriate
materials. There is a risk of other items coming into contact with
a cryogenic temperature due to a leak but in practice the hazard is
negligible due to the layout of the plant and the protection
afforded by insulation.
5.1.2.4 Overpressure effects
Damage and injury from resulting shock wave and flying fragments
due to catastrophic failure of a high pressure equipment.
5.1.2.5 Fog formation
Clouds in the area of evaporating liquid oxygen consist of air,
oxygen and fog (condensed water from the moisture in the air). This
fog may pose a hazard if site is close to a major roadway.
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Under normal atmospheric conditions, the edge of the visible
cloud from a cryogenic spill is less than 25% oxygen concentration.
Thus the limit of the fog will generally indicate a safe area.
5.1.2.6 Environmental effects
Non toxicity (oxygen is part of normal atmosphere) and high
volatility of oxygen do not comprise any threat to the environment.
Materials which come into contact with the liquid are violently
chilled, while gaseous oxygen is generated. Liquid oxygen freezes
the ground and causes ice formation. Pipes can become blocked and
brittle entailing an increased risk of pipe rupture.
5.1.2.7 Vessel rupture
The worst scenario which theoretically could occur is
catastrophic failure of the LOX storage tank. This could occur for
a variety of reasons. The safety report must address all possible
scenarios, and should confirm catastrophic failure is a very
unlikely event. Listed below are some arguments to help support
this view. However each company should prepare its own case
specific to the site in question.
5.1.2.7.1 External impact
The location of the LOX storage tank in relation to the local
airport and flight paths should be described. Any nearby military
airbase or overhead flying by the military should be mentioned. The
chance of an aircraft crashing into the tank and leading to a major
spill of LOX could then be estimated using reference 2. (Annex C).
The probability of missiles formed from an explosion on or off the
site (eg. neighbouring chemical plant) should be discussed.
Calculations may be necessary to discount this possibility if
flammables, explosives or high pressure volume equipment are
located on or near the site. It should be stated that the outer
shell and perlite insulation affords substantial protection against
external impact. See incident 5.1.1.7.
5.1.2.7.2 Natural events
The possibility of an earthquake or land subsidence should be
discussed. If there is no historical evidence of significant
seismic activity or subsidence in the area this should be stated.
It may be necessary to calculate the degree of earth tremor which
could damage the tank and estimate the probability of the event.
Details of the concrete piling and civil engineering codes followed
may be referenced. If flooding could cause a problem (eg. a nearby
river bursting its banks) this should also be discussed. The design
wind loading should be compared with historical weather data for
the area.
5.1.2.7.3 Sabotage
The security arrangements at the site should be discussed. Any
special precautions to prevent sabotage should be noted.
5.1.2.7.4 Design/manufacturing fault
The vessel dossier should be referenced which should contain the
specification, engineering drawings, details of non destructive
testing, pressure test, material certification, etc. If all this
information is not available then measures to obtain this data
should be outlined. The following facts could be stated:
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The tank is built to a recognised design code (state applicable
code) which is more than
adequate for the service conditions.
The product being stored is dry, clean and non corrosive. The
production process is such that possible corrosive contaminants are
removed from the feedstock atmospheric air before LOX is
produced.
The materials of construction of the inner vessel exhibit
enhanced mechanical properties at
low temperatures and good corrosion resisting properties at low
temperatures. At cryogenic temperatures corrosion does not occur.
Critical size defects for initiation of unstable fracture
propagation are large and will not escape detection with the degree
of pre-service inspection employed. Credible existing defects in
cryogenic materials will not grow by fatigue to such dimensions
that unstable fracture propagation could occur. If cycled beyond
their design fatigue levels defects will grow at localised points
and a "leak before break" situation will exist (refer to Annex D of
this document). The probability of a leak developing during the
life of a tank is considered to be extremely low.
The tank design was approved and the construction inspected by
an independent inspector
(state approval authority). The inspection dossiers are
available for examination.
The tank undergoes a periodic external visual examination in
accordance with a written scheme of inspection to confirm the
satisfactory condition of the outer shell and associated exposed
pipework, valves, controls and auxiliary equipment.
Periodic monitoring of the composition of the purge gas in the
insulation space is performed to
identify the existence of any inner vessel leaks. The supply of
purge gas is checked periodically to ensure an effective purge is
being maintained.
The chance of an initial defect causing subsequent catastrophic
failure of the vessel is an extremely unlikely event. If it is
necessary to support this view then the data of the type presented
in Annex D of this document can be used.
5.1.2.7.5 Over-pressure
Over-pressure of the storage tank is a possible process cause of
catastrophic tank failure. It is recommended that a fault tree be
drawn to show the combination of events which must take place for
the tank to fail from over-pressure. It is recommended to support
the case that over-pressure is a very unlikely event, that the
fault tree is quantified. If possible, maintenance records from the
site and/or similar plants should be used to confirm the average
failure rates of the fault tree components.
5.1.2.7.6 Other events
Based upon the hazard identification, a simple list of the other
events which can result in oxygen release should be given. For
example:
tanker towaway damage hose failure or leak pipe fracture (list
sizes) - external impact; movement of pipe; trapped liquid fire in
an oxygen line overfill of tanker under-pressure of storage tank
liquid discharge from overfill of storage external fire /
explosion.
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5.1.2.8 Consequence Analysis
Once the events have been determined the consequences of each
event on the environment have to be considered. The liquid leak is
generally the major event but the gas leak should also be
considered. Once the liquid has leaked, three steps must be
examined:
spill vaporisation dense gas cloud dispersion.
See Annex E of this document for example calculations.
5.2 Acetylene
5.2.1 Incidents involving acetylene
The following incidents are recorded in the EIGA database. It is
recommended that all these incident summaries are not repeated in
the safety report but this document should be referenced.
5.2.1.1 Explosion in a neutralisation vessel, Germany, 1996
Some minutes after restarting an acetylene plant after a
weekend, an explosion occurred in a vessel to neutralise spent acid
(H2SO4) in lime. Due to very low temperatures during the whole
weekend (approx -15C) the surface of the remaining lime in the
vessel became frozen and blocked the level switch of the lime pump.
The pump started and emptied the vessel below the ice formation.
Several minutes later when fresh lime entered the vessel the ice
cracked, fell on the metallic propeller equipment and damaged it. A
spark formed by the propeller touching the surrounding equipment
and ignited acetylene which was evaporating from the incoming lime.
Safety flaps opened and released the overpressure. The vessel was
slightly damaged, no persons injured. Propeller construction was
changed and the vessel was equipped with a jacket heater.
5.2.1.2 Fire in a generator, Colombia, 1995
Cleaning of acetylene generator (maintenance) through manhole
resulting in an explosion. Generator was purged with CO2 for 45
minutes. Cleaning resumed, another explosion occurred. Two
operators burnt. Probable cause - unreacted poor quality carbide
insulated by lime.
5.2.1.3 Fire in the devalving station, Norway, 1994
An acetylene cylinder was sent for devalving without checking by
weighing that it was really empty. After devalving the cylinder,
the worker started to remove the filter. Cloud of gas came out.
Fire started. Burns to hand (no protective gloves). Damage.
5.2.1.4 Fire/explosion in filling area, Australia
Blowdown to atmosphere inside the filling building of a large
number of acetylene cylinders due to acetone spitting problems. An
ignition occurred and fire spread causing the destruction of the
cylinder filling building, filling racks and about 800 cylinders.
One operator received slight burns requiring hospital treatment for
2 days. Fall out of asbestos containing porous filler spread up to
1 km down wind of the site.
5.2.1.5 Explosion in a generator, Germany, 1990
During maintenance of a generator the lime and residue were
washed out by means of a water hose. An explosion occurred. No
injury, windows broken.
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5.2.1.6 Decomposition, explosions in compressor and filling
ramps, Spain, 1989
Two explosions occurred in an acetylene plant. The first one in
an oil separator compressor, the second in one of the filling
ramps. Further, a fire occurred. No injury. Damage on separator
compressor, the second in one of the filling ramps. Further, a fire
occurred. No injury. Damage on separator, cooler, ramps, plant
roof.
5.2.1.7 Decomposition, explosion, fire in a compressor,
Portugal, 1989
In an acetylene plant, when an operator started a regular
operation of compressor purge, the compressor caught fire, causing
explosion in the oil separator cylinder. Operator killed. Separator
cylinder destroyed, shop damaged.
5.2.1.8 Decomposition: Detonation in a piping system, Spain,
1988
An explosion occurred due to acetylene decomposition in the
piping between the acetylene compressor and the downstream
acetylene drier. No injury. Piping, compressor and drier damaged.
Rooms and technical equipment damaged.
5.2.1.9 Fire in the devalving area, Belgium, 1982
After disconnecting an acetylene cylinder the acetone escaped
because the valve was not closed. Cylinder dropped out of the hands
of the worker. Escaping acetone vapour and acetylene ignited. One
man died in the flames, two men received burns.
5.2.1.10 Decomposition, explosion, fire in a filling station,
Venezuela, 1979
Decomposition in a filled acetylene cylinder caused an explosion
and fire in the surrounding cylinders. Cylinders were Coyne type,
bottom and top melt. Two operators injured (burns), considerable
damage - building, filling racks, compressors, driers.
5.2.1.11 Fire in a drier battery, Sweden, 1979
Outflowing gas ignited when the gel in a drier battery for
acetylene was replaced. Pressure had been let out of the cylinders,
and they had been purged with nitrogen. A spark caused the
ignition. One man received facial burns, no damage.
5.2.1.12 Deflagration in carbide dust exhausting system,
Germany, 1978
Deflagration in carbide dust exhausting system with fire in
carbide storage hopper of generator. Secondary deflagration in same
storage hopper. Carbide dust exhausting system damaged, windows
broken. Operator slightly burned on face, hands. The generator had
not been purged before adding the carbide.
5.2.1.13 Explosion, fire in the dust separator, generator,
Germany, 1977
Sucked up acetylene ignited in the dust separator piping. The
fire reached the generator which burnt. Operator suffered burns,
complete installation destroyed.
5.2.1.14 Explosion of a gasholder after decomposition, Denmark,
1974
Prior to restarting an acetylene plant, a finishing welding was
initiated on a generator hopper cover. An explosive ignition passed
through the main hydraulic seal into the gas holder, which
exploded. No injury, damage to gas holder, windows, roof.
5.2.2 Hazard analysis
The major hazards of acetylene result from its two principal
properties:
The extremely wide range of its flammable limits.
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The characteristic of acetylene to decompose with a high energy
release with or without the presence of air.
The analysis is focussed on the effect of these hazards and on
those areas of the plant where there could be acetylene/air
mixtures, or where the physical conditions of the acetylene
(pressure and temperature) may be conducive to a decomposition.
Information on the hazards: Include safety data sheets for
acetylene and all the other hazardous materials handled and stored
on site.
5.2.2.1 Fire / Explosion
Mixtures of 2.3 % to 82% acetylene in air can be easily ignited
and lead to an explosion. The ignition temperature of acetylene in
air is 305C. Acetylene is about 10% lighter than air and will
disperse relatively quickly in the open. Release inside buildings
may accumulate at high levels.
5.2.2.2 Decomposition / Explosion
5.2.2.2.1 Gaseous acetylene
Undissolved acetylene can decompose without the presence of air
and revert to its basic elements, carbon and hydrogen. This may
occur at pressures of less than 1 barg and is dependent on the
ignition energy. Considerable amounts of heat are evolved during
the process of decomposition which can occur explosively. The
energy required to start the reaction and the manner in which the
reaction proceeds, i.e. a deflagration or detonation, are dependent
on the pressure of the gas and the dimensions of the pipe or
container. See Figure 2. The decomposition temperature for
compressed acetylene in the presence of small quantities of rust
can be reduced to 280C. In the presence of acetylene, especially
when moist, unalloyed copper, silver and mercury can form explosive
acetylides, which are easily ignited and create a decomposition.
Alloys containing high amounts of these materials, eg. >70% Cu
can react in a similar way. For further information see reference
7. Figure 2
A: Deflagration Limit Line / Ligne limite de dflagration /
Deflagrationsgrenzlinie
B: Detonation Limite Line / Ligne limite de dtonation /
Detonatonsgrenzlinie
10
Wor
king
Pre
ssur
e /
Pre
ssio
n de
Ser
vice
/ B
etrie
bsdr
uck
(bar
a)
B
A
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5.2.2.2.2 Liquid acetylene
Liquid acetylene can be formed under the conditions of high
pressure and low temperature and may decompose violently under the
influence of vibration or heat. Temperatures of formation of liquid
acetylene (reference 7): Acetylene gauge pressure (bar) 25 22 19 16
14 12 10 Liquefaction temperature (C) -1 -5 -10 -15 -20 -25 -30
5.2.2.2.3 Solid acetylene
Solid acetylene cannot be formed in an acetylene production
plant. It is formed at 1 bar and when the temperature is less than
-84C. At atmospheric pressure it sublimes to a gas. It is less
sensitive to explosive decomposition than liquid acetylene.
5.2.2.3 Other hazards of acetylene
Unpurified acetylene contains small amounts of toxic impurities
(eg. phosphine, ammonia) and prolonged inhalation should therefore
be avoided. Purified acetylene is not toxic but inhalation of low
concentrations can cause headaches, nausea, etc. At high
concentration in air it can cause asphyxiation from the depletion
of oxygen. Acetylene reacts violently with oxidants such as
bromine, chlorine and fluorine.
5.2.2.4 Solvent spill
The main hazard of the solvent acetone and DMF should be
described (make reference to material safety data sheets of acetone
and DMF).
5.2.2.5 Calcium carbide
Inadvertent contact of calcium carbide and water will produce
acetylene. Calcium carbide dust will even react with moisture in
the air to produce acetylene. Calcium carbide dust is not flammable
and therefore cannot produce a dust explosion.
5.2.2.6 Discussion of failure cases
The worst scenario which could occur is an explosion or fire in
the plant. This could be caused from a variety of reasons. The
safety report must address all possible scenarios, to demonstrate
that a major fire or explosion is unlikely and cannot cause a major
hazard. Listed below are some of the reasons which support this
view. However, each company should prepare a specific case for the
site in question.
5.2.2.6.1 External events:
The effect of a fire or explosion on or off site (eg.
neighbouring forest or chemical plant) should be discussed.
Calculations may be necessary to evaluate the consequences of this
especially if flammables, explosives or high pressure-volume
equipment are located on or near to the site. If there is a risk of
flooding the protection of the carbide store should be
described.
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5.2.2.6.2 Sabotage / Vandalism
The security arrangements at the site should be described. Any
special precautions to prevent sabotage should be noted.
5.2.2.6.3 Design / Construction fault
The Permission Dossier of the plant should be referenced. This
should contain the specification, engineering drawings, details of
non destruction testing, pressure test, material certification etc.
If some of this information is not available then measures must be
taken to ensure that the system is basically safe.
5.2.2.6.4 Internal events
Carbide store: The building may be damaged by floods or
hurricanes. In this case proper protection should
be provided and described (see section 5.2.2.9)
Carbide transfer from vessels to the generator: If there is a
decomposition of acetylene in the hopper, the container could be
destroyed and a
large quantity of acetylene may be released.
Generators: Under normal operating conditions, the main causes
of incidents are usually mechanical
failure or lack of maintenance. Several scenarios are possible;
those causing over-pressure, negative pressure or abnormal heating
can be controlled by the appropriate protection devices, i.e. valve
operation, nitrogen injection, cut off of carbide supply, increased
water flow rate etc.
However, the risk of a generator catastrophic failure is quite
unlikely and none has been
reported since records have been formally collected by EIGA
(since 1980 and for approximately 150 plants in Europe).
Accidents have been caused by purge failures during shutdown or
startup and carbide
charging. These which have occurred had a limited effect and did
not cause a hazard to the surrounding population.
Low pressure circuits:
These circuits, which generally consist of large diameter pipes
(e.g. 100mm) transfer the gas from the generator to the
compressor.
The low pressure of the gas in these circuits, usually only a
few millibars, makes a
decomposition unlikely. However, EIGA have recommended that low
pressure circuits are designed to accommodate a deflagration which
would result in an 11 times pressure increase (see Doc 9/78).
Compressor:
The compressor receives the acetylene normally at slightly
elevated pressure. If this pressure falls below a fixed low point,
a pressure switch stops the machine, thus preventing the possible
suction of air into the compressor. In high pressure circuits, a
pressure switch stops the machine if the pressure exceeds the
maximum permitted pressure. An abnormal increase in gas temperature
during compression could start an explosive decomposition of the
compressed acetylene. This is controlled by a high temperature
switch. In such a case, it is unlikely that this decomposition
could cause a detonation, because the volumes involved are small,
and the internal design configuration of the machine. Furthermore,
those components which are in contact with the compressed gas are
tested to 11 times maximum operating pressure.
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In practice, the effects of an explosion in the compressor or
its associated equipment could only be felt downstream of the
machine, in the high pressure pipe network, and this is designed
and tested to withstand these pressures.
Fire in a cylinder filling room:
A possible scenario is a fire or explosion in the cylinder
filling room where cylinders are connected to manifolds and placed
very close to one another.
During filling the amount of acetylene absorbed in the cylinder
increases at the same time as
the pressure, the number of connections means that there is the
possibility of a leak. Under these circumstances a small fire in
this area could cause the gas in the pipework or the cylinders to
decompose leading to an explosion or fire which could affect
adjacent cylinders and result in a much more serious incident.
Failure of protection systems:
A routine inspection and test of the fire protection system
instruments shall be carried out in accordance with a written
schedule and the manufacturer's recommendations.
Faulty or damaged cylinders:
Precautions are described to ensure that faulty or damaged
cylinders are not filled and methods for identification, repair
and/or disposal.
Other internal events:
Based upon the hazard identification a simple list of the other
events which could result in an acetylene release should be given
here. For example:
- internal accidents (lorries, fork lift trucks) - hose failure
or leak - operator error - pipe fracture (list sizes) from external
impact; movement of pipe; trapped gas or
solvent; external fire/explosion - acetylene decomposition in
the pipework - liquid acetylene formation - over-pressure of a
generator - cylinder rupture - failure of a fusible plug.
5.2.2.7 Consequence analysis
Once the events have been determined the consequence of each
event on the environment has to be considered. For the
determination of consequences the following steps should be
reviewed. Example calculations are given in Annex E of this
document.
5.2.2.7.1 Loss of containment of acetylene from the process:
Low pressure release The amount of gas contained in the low
pressure system usually does not exceed 50 kg.
Calculate the maximum size of cloud in the flammable range for
each of the relevant failure cases above. Gas dispersion will be
dependent upon the size of leak (i.e. flow rate and time It should
be possible to demonstrate that for most of the failure cases, the
size of the flammable cloud is small and if ignition occurred would
result in only limited damage and not create a major accident
hazard. Calculate the over-pressure and thermal radiation from the
ignition of the largest flammable cloud. See Annex E.
High pressure release
All acetylene plants are designed to ensure that the amount of
acetylene contained in the high pressure pipework is very small,
typically not more than 1 kg. (This assumes that there is 100m of
20mm pipe and the acetylene driers are at a pressure of 26
bara).
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This excludes the acetylene absorbed in the cylinders which are
separated from the system by non return valves and it assumes the
compressor has been stopped. If a pipe fails there would not be
sufficient gas to sustain a jet and the resulting puff would not
last more than 2 or 3 seconds. Therefore this is not considered a
major hazard. If the compressor has not stopped it is possible to
have a continuous release into the building. The resulting
over-pressure of an explosion of the acetylene inside the building
should be calculated. See Annex E.
5.2.2.7.2 Explosion within process equipment
Theoretically there are three possible causes:
decomposition of the gas A decomposition on the HP-side will not
create a major hazard because the system is
designed to withstand the highest pressures which are likely to
occur and only have a local effect due to the installation of
multiple flame arrestors and quick shut off valves in the
lines.
Decomposition and deflagration on the low pressure side
(excluding the gasholder) will not
result in damage to the equipment because the resulting
pressures are below the design pressure. The only recorded case in
Europe (about 150 plants) was an incident in a 50m3 gasholder. In
this case the bell acted as a safety valve and released the
decomposition products. The only consequence of this incident was
minor local damage which was not capable of producing a major
accident.
formation of liquid acetylene
The formation of liquid acetylene in the high pressure system
can be excluded for water cooled compressor systems as the
temperature of the acetylene cannot fall below 0C (see 5.2.2.2.2
provided the pipework is properly protected against frost. For air
cooled compressors risk and consequence analysis should be
prepared.
ingress of air and ignition.
The ingress of air into the low pressure system and a subsequent
ignition could result in serious damage to the plant.
A suitable analysis, such as a fault tree should be prepared to
show that this possibility has
been taken into account and protection devices added to make the
probability extremely low. No consequence analysis would then be
necessary.
5.2.2.7.3 Cylinder rupture
A cylinder rupture is extremely dangerous and can be caused
by:
external overheating internal decomposition
and contributory factors can be:
overcharging of the cylinder incorrect acetylene/solvent ratio
failure of the porous mass presence of air or oxygen in the
system.
A cylinder rupture can lead to a domino or cascade effect on
other cylinders or equipment causing them to fail. Also missile
debris from the cylinder will be produced although these are
usually impeded by buildings and equipment.
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5.2.2.7.4 Solvent spill
A solvent spill may result in a pool fire and the effect of the
resulting radiant heat should be considered. The possibility of the
solvent entering the site drainage system should also be considered
as ignition of the vaporised solvent could result in an explosion.
Other consequences could be the contamination of the surrounding
ground and water course. However, suitable precautions should be
described to show that significant contamination is unlikely and a
consequence analysis is not necessary.
5.2.2.8 Specific safeguards in acetylene production
5.2.2.8.1 Emergency shutdown systems
The plant is equipped with an emergency shutdown system, which
can be easily operated from a number of locations (i.e. from the
generator room, compressor room, cylinder filling room, control
room etc). The system stops the generator carbide feed and the
compressors. Simultaneously, the emergency water spray system
installed in filling rooms and filling areas will be manually or
automatically started. The nitrogen purge system will also be
started. The sprinkler systems in these areas supply the highest
water flow rate per unit of surface areas available in an acetylene
plant. Sprinkling continues for as long as necessary to cool the
cylinders. Special instructions are posted for these circumstances
in all plants. Similar instructions are also given to the fire
department. The safety report shall include details of the
equipment and its method of operation. This will probably include
sketches and other design details, as well as the routine
maintenance and test records.
5.2.2.8.2 Flame arrestor
As an example one of the important safeguards to prevent the
propagation of the decomposition of acetylene within the high
pressure pipework is the flame arrestor. The policy for the
installation of these flame arrestors should be stated, eg. IGC-Doc
19/84.
5.2.2.8.3 Venting systems
Venting systems are installed in the roof areas of the
buildings, additional protection can be provided by the
installation of flammable gas detectors. The equipment and piping
system are designed and constructed to ensure that no gas will leak
out during normal operation. Safety valves are provided to avoid
excessive pressure in the system. All pressure releasing devices
vent into safe areas. Regular inspection and leak tests are carried
out to enable the detection of small leaks and their repair.
5.2.2.9 Storage and handling of calcium carbide
5.2.2.9.1 General
Whilst handling full or empty calcium carbide vessels or
containers the formation of an air/acetylene mixture is prevented
and there are no ignition sources in the area. They are earthed and
non spark tools are used to prevent any ignition. Additionally the
vessels are purged with dry air or inert gas, eg. nitrogen.
5.2.2.9.2 Calcium carbide store
The store is kept well ventilated, dry, and ingress of water to
the store is prevented. The vessels are designed to withstand a
drop test. They are also waterproof. No naked flames or smoking is
permitted in the storage area.
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The permanent electrical equipment of the store is to a
classification which allows for a very occasional release of
acetylene into the atmosphere, and no portable unclassified
electrical equipment is allowed inside the store. If there is a
fire, water is not used. Dry powder fire extinguishers are kept in
designated areas. Other chemicals such as acids, corrosives and
flammables are not kept in the carbide store. Suitable notices are
displayed at all access points, both inside and outside. Methods of
handling a hot or pressurised vessel should be described. An
example for a drum could read as follows: Hot carbide drums should
not be moved and not be opened while hot to the touch; after they
have cooled they should be left a further 24 hours. The drum should
then be opened by first puncturing it with a suitable non spark
tool in two places on opposite sides of the top or opposite ends of
the drum. Nitrogen should be blown through one of the small holes
produced to completely purge the drum before the top is cut out
using an approved cutter.
5.2.2.10 Acetylene generation and cylinder filling
5.2.2.10.1 Acetylene generators - general
The hazard analysis will define the precise scope of the
protection equipment:
Precautions to avoid or to minimise the formation of
acetylene/air mixtures. Methods to ensure that any hazardous
mixtures can be dispersed safely. Precautions to prevent the
generation of static electricity and sparks (earthing). Precautions
to avoid overfilling the feed hopper.
Typical examples of the safety equipment which may be fitted to
generators in order to fulfill these requirements are listed
below:
Earthing - all the equipment is properly earthed and includes
containers, barrels and drums, whil