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 : info@eiga.org 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: info@eiga.org 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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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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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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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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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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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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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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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