major accidents in process industry

Journal of Loss Prevention in the Process Industries 12 (1999) 361–378www.elsevier.com/locate/jlp

Major accidents in process industries and an analysis of causes andconsequences

Faisal I. Khan, S.A. Abbasi*

Computer Aided Environmental Management Unit, Centre for Pollution Control and Energy Technology, Pondicherry University, Kalapet,Pondicherry-605 014, India

Abstract

This paper briefly recapitulates some of the major accidents in chemical process industries which occurred during 1926–1997.These case studies have been analysed with a view to understand the damage potential of various types of accidents, and thecommon causes or errors which have led to disasters. An analysis of different types of accidental events such as fire, explosionand toxic release has also been done to assess the damage potential of such events. It is revealed that vapour cloud explosion(VCE) poses the greatest risk of damage. The study highlights the need for risk assessment in chemical process industries. 1999Elsevier Science Ltd. All rights reserved.

Keywords:Industrial hazards; Risk assessment; Explosions; Fires

1. Introduction

To understand the mechanisms of accidents and todevelop accident prevention and control strategies, it isessential to know about and learn from past accidents.However, industries are generally reluctant in revealingwhat had happened and have a tendency to underplaytheir mistakes. This aspect has been discussed byBadoux (1983); Marshall (1987); Kletz (1989); Lees(1996). Unfortunately the negative attitude of the indus-tries to cover up the truth has caused an increase in thefrequency of accidents. Among these accidents many aredue to the repetition of the same/similar faults (Kletz,1991a, b). Not only for industrial accidents but even foraccidents occurring during transportation there is alwayssomeone with an interest in suppressing the facts.

In India a study funded by the International LabourOffice pertaining to identification of major accident haz-ards and the development of a control system was con-ducted (Gupta, 1990), which revealed a total of 586major accident hazard (MAH) units and 75 hazardouschemicals. The distribution of MAH units and hazardouschemicals across various states of India is presented in

* Corresponding author. E-mail: [email protected]

0950–4230/99/$ - see front matter 1999 Elsevier Science Ltd. All rights reserved.PII: S0950-4230 (98)00062-X

Table 1 (Raghavan & Swaminathan, 1996). It is seenthat the states of Gujarat and Maharashtra have the lar-gest number of MAH units and also handle the largestnumber of hazardous chemicals. No wonder, then, thatthe maximum number of accidents in the past occurredin these two regions.

2. Definition of accidents

According to Suchman (1961), an event can be classi-fied as an accident if it is unexpected, unavoidable andunintended. He has proposed the following three charac-teristics with which to classify an event as an accident:(1) degree of expectedness, (2) degree of avoidabilityand (3) degree of intention.

Secondary characteristics are: (1) degree of warning,(2) duration of occurrence, (3) degree of negligence and(4) degree of misjudgement. An event is an accident ifit gives little warning, happens quickly, or if there is alarge element of negligence and misjudgement leadingto it.

Suchman has added that as knowledge increases anevent is more likely to be described in terms of its causalfactors and less likely as an accident.

362 F.I. Khan, S.A. Abbasi /Journal of Loss Prevention in the Process Industries 12 (1999) 361–378

Table 1State-wise distribution of major hazardous units (MAH) and hazard-ous substances

State MAH units Hazardous substances

Andhra Pradesh 35 24Bihar 12 11Delhi 19 8Goa 8 9Gujarat 112 32Karnataka 26 14Kerala 19 19Maharashtra 97 24Madhya Pradesh 33 10Tamil Nadu 41 31Uttar Pradesh 40 14West Bengal 40 23Assam 7 10Haryana 7 4Jammu Kashmir 7 4Nagaland 1 1Orissa 13 10Pondicherry 3 3Punjab 12 6Rajashthan 54 17

Total number of MAH factories, 586.Total number of hazardous substances, 75.

2.1. Modelling of accident process

It is helpful to model the accident process in order tounderstand more clearly the factors which contribute toaccidents and the steps which can be taken to avoidthem. One type of model, discussed by Houston (1971),is the classical one developed by lawyers and insurerswhich focuses attention on the ‘proximate cause’. It isrecognised that many factors contribute to an accident,but for practical, and particularly for legal, purposes aprincipal cause is identified. This approach has a numberof defects: there is no objective criterion for dis-tinguishing the principal cause, the relationships betweencauses are not explained, and there is no way of knowingif the cause list is complete.

Another type of model is the fault tree model. A sim-ple fault tree model of an accident is presented in Fig.1. The initiating event which constitutes a potential acci-dent occurs only if some enabling event occurs, or hasalready occurred. This part of the tree is termed a‘demand’ tree, since it puts a demand on the protectivefeatures. The potential accident is realised only if pre-vention by protective equipment and human action fails.An accident occurs which develops into a more severeaccident only if mitigation fails. A similar model basedon fault tree has been proposed by Wells, Phang, Ward-man and Whetton (1992).

Another approach to model accidents is that taken byKletz (1988), who has developed a model orientedtoward accident investigation. The model is based essen-

Fig. 1. Fault tree accident model.

tially on the sequence of decisions and actions whichlead up to an accident, and shows against each step therecommendations arising from the investigation (Fig. 2).

A model which emphasises the broader, socio-techni-cal background to accidents has been developed byGeyer and Bellamy (1991) as shown in Fig. 3. It presentsa generic model and the application of the model toan incident.

3. Major process hazards

The major hazards with which the chemical industryis concerned are fire, explosion and toxic release. Ofthese three, fire is the most common but explosion ismore significant in terms of its damage potential, oftenleading to fatalities and damage to property. Toxicrelease has perhaps the greatest potential to kill a large

363F.I. Khan, S.A. Abbasi /Journal of Loss Prevention in the Process Industries 12 (1999) 361–378

Fig. 2. Kletz accident model.

number of people and cause an area to be toxified forseveral months to several years. Large toxic releases arerare but, as the Bhopal tragedy indicates, may have veryhigh death tolls.

Often no distinction is made between fire andexplosion losses. The latter are normally included in theoverall fire statistics. In fact, it is explosions which causethe most serious losses (Doyle, 1969, 1981; Norstrom,1982; Davenport, 1988; Carson and Mumford, 1988). Asmuch as two-thirds of the losses arising from an accidentoccurring in chemical process industries are attributableto explosions (Health and Safety Executive, 1988; Lees,1996). Over three-quarters of the explosion involve com-bustion or explosive materials. Norstrom (1982) ana-lysed fire-based and explosion-based accidents separ-ately (Tables 2 and 3). It is evident that about 18% offires are due to release and overflow of flammable gasesand/or liquids. Fires contributed about 20% to the totalloss. In comparison, explosions contributed about 75%to the total loss. Failure of proper reaction controlsseems to be the most frequent cause leading to accidents.It contributed 35% to the total number of accidents. Theprocessing area is the most susceptible location of theaccident.

Marshall (1977); Bellamy, Geyer and Astley (1989)have reported data for various release accidents (Table4) in which the incidents are ranked in terms of the

Fig. 3. Gayer and Bellamy model of the accident process (Geyer &Bellamy, 1991).

Table 2Main causes of large fires in the chemical and allied industries(Norstrom, 1982)

Causes Proportion(%)

Flammable liquid or gas (release, overflow) 17.8Overheating, hot surfaces, etc. 15.6Pipe or fitting failure 11.1Electrical breakdown 11.1Cutting and welding 11.1Arson 4.4Others 28.7


Table 3Information related to explosion in the chemical and allied industries(Lees, 1996)

Proportion(%)

Main causeChemical reaction uncontrolled 20.0Chemical reaction accidental 15.0Combustion explosion in equipment 13.3Unconfined vapour cloud 10.0Overpressure 8.3Decomposition 5.0Combustion sparks 5.0Pressure vessel failure 3.3Improper operation 3.3Others 16.8

Frequent location of occurrenceEnclosed process or manufacturing buildings 46.7Outdoor structures 31.7Yard 6.7Tank farm 3.3Boiler house 3.3Others 8.3

Various contributing factorsRupture of equipment 26.7Human element 18.3Improper procedures 18.3Faulty design 11.7Vapour-laden atmosphere 11.7Congestion 11.7Flammable liquids 8.3Long replacement time 6.7Inadequate combustion controls 5.0Inadequate explosion relief 5.0

amount of vapour released. Their reports suggest thatlarge releases often result in explosions rather than fires.

The problem of avoiding major hazards is essentiallythat of avoiding loss of containment. This includes notonly preventing an escape of materials from leaks etc.,but also avoidance of an explosion inside the plant ves-sels and pipe work. Some factors which determine thescale of the hazard are:

1. the inventory;2. the energy factor;3. the time factor;4. the intensity–distance relations;5. the exposure factor;6. the intensity–damage and intensity–injury relation-

ships.

Data related to major injuries (including fatality) inchemical and allied industries have been plotted in Fig.4. It is evident from the data that, in the chemical indus-tries, the rate of fatal injuries is less than in mineral oilprocessing industries (refineries, etc.). But during the last

Table 4Characteristics of accidental release from pipework and in-line equip-ment (Bellamy et al., 1989; Lees, 1996).

No. of incidents

Location typeChemical plant 278Refinery 96Factory 187Storage depot 47Tank yard 28Fuel station 15Other 38Unknown 232Total 921

Site statusNormal operations 343Storage 103Loading/unloading 33Maintenance 146Modification 8Contractor work 18Testing 5Unknown 128Other 40Start-up 42Shut-down 18Total 884

Materials releasedAmmonia 54Hydrocarbons (unspecified) 54Chlorine 50Hydrogen 37Benzene 33Crude oil 28Steam 25Natural gas 24Propane 20Butane 18Fuel oil 18Hydrochoric acid 16Sulphuric acid 16Ethylene 16Hydrogen sulphide 14Water 13Nitrogen 13Oxygen 13Vinyl chloride 12LEG 12Styrene 11Naphtha petroleum 10Total 507

Material phaseLiquid 393Gas 260Vapour 13Solid 9Liquid 1 gas/vapour 120Solid 1 gas/vapour 3Total 798


Table 4Continued.

No. of incidents

Unignited material dispersionFlammable 127Toxic 123Flammable/toxic 47Corrosive 97Irritant 1Unignited gas 96Vapour cloud 180Liquid 212Spill 186Jet/spurt 8Spray 10Total 1087

Fire or explosion eventFire 145Flash fire 11Pool fire 4Jet fire 1Fireball 7BLEVEa 4Explosion 63Explosion followed by fire 77Explosion followed by flash fire 2Total 314

aBoiling liquid expanding vapour explosion.

Fig. 4. Incidence rates of fatal and major injuries in chemical andmineral oil processing industries (1981–1990).

few years the rates seem to have come close to eachother for the two types of industries.

3.1. General causes of accident

After an accident, various analysts and pressuregroups formulate different theories of the possiblecauses. There are almost as many different diagnoses asthere are investigators. Unfortunately, there is no accept-

ance, or consistent cause–effect diagnostic system, so itis often difficult to reconcile different analyses.

3.2. Reporting of incidents and databases

According to Lees (1980, 1994, 1996), the extent andthe accuracy of the reporting of incidents and injuriesare variable and this creates problems, particularly forattempts to perform statistical analysis of the data.

For example, past incidents in the USA, the UK, andsome of the EU (European Union) countries have gener-ally been reported in detail and analysed critically butcomparable incidents in the erstwhile USSR, China andBalkan states have received much less publicity andassessment.

The problem has been discussed by Badoux (1983).Fig. 5 shows schematically the probable extent of under-reporting, curve A representing the actual reporting situ-ation and curve B the ideal one (Lees, 1996).

There are a number of databases specifically dealingwith case histories. They include the following.

I Major Hazards Incident Data System (MHIDAS) andthe corresponding explosives data system EIDAS.These are operated by SRD (Safety and ReliabilityDirectorate, UK Atomic Energy Authority).

I The FACTS incident database.I The Major Accident Reporting System (MARS),

described by Drogaris (1991, 1993).I The FIRE incident database for chemical warehouse

fires, described by Koivisto and Nielsen (1994).I The offshore Hydrocarbon Release (HCR) database

described by Bruce (1994).

In this paper a study of industrial accidents has beenconducted with a view to identify the factors which leadto accidents and the lessons for loss prevention to belearnt from these accidents. This study may be helpful

Fig. 5. Under-reporting of accident (Lees, 1996).


in developing newer know-how for process safety andaccident damage control.

3.3. Classification of accidents

Accidents involving hazardous chemicals can bebroadly categorised into two major groups: fixed instal-lation accidents and transportation accidents. The fixedinstallation accidents consider all accidents occurring inindustries during different stages of operation, whiletransportation accidents consider accidents occurringduring transportation, loading or unloading of chemicals.The transportation accidents can be further categorisedaccording to the different mode of transportation.

A search of the literature covering the time span 1926through to 1997 revealed reports of 3222 accidents relat-ing to handling/transportation/processing/storage ofchemicals (Nash, 1976; Lewis, 1984, 1993; Marshall,1987; Hasstrup & Brochoff, 1990; Chowdhury & Park-inson, 1992; Taylor, 1993; Thomas, 1995; Lees, 1996;Khan & Abbasi, 1996, 1997). The actual number maybe high as reports of all accidents are not available in theprimary literature. Moreover, we have considered hereaccidents involving the loss of more than $1 millionand/or fatalities.

Of the 3222 accidents, 54% are fixed installation acci-dents, 41% are transportation accidents and 5% miscel-laneous accidents (Fig. 6). The 1320 transportation acci-dents can be further classified according to the differentmodes of transportation. Such classification (Fig. 7) indi-cates that 37% occurred during rail transport, 29% dur-ing road transport, 6% during marine transport, 18% dur-ing pipeline transport, 4% during inland waterwaytransport, and the remaining during loading andunloading of chemicals. Whether pipelines should beconsidered as fixed installations or a means of transpor-

Fig. 6. Accident classification.

Fig. 7. Accident cases concerning transportation.

tation is a matter of some controversy. We feel that theportion of the pipeline which falls within the confinesof the industry should be treated as a fixed installationand the portion outside the industrial periphery as atransport vehicle.

Of the different means of transportation, rail hashigher damage potential as larger quantities are trans-ported by this means. However, if we consider the dam-age it may cause to life and property, transport by roadis more hazardous, as roads often pass through populatedareas, especially in developing countries (Khan &Abbasi, 1995).

Pipeline transportation is comparatively safer, pro-vided that the speed and conditions of transportation(temperature, phase, and pressure) as well as the routeof the pipeline are carefully managed. A summary of theworst transport disasters are presented in Table 5.

4. Fixed installation accidents

Our survey reveals that 1744 significant accidentshave occurred during the period 1928–1997. A study ofmajor factors (vessels, chemicals, process conditions)leading to accidents is summarised in Table 6. It revealsthat chemical process plants are most prone to accidents.Ammonia is the chemical most often involved. Of the1744 accidents (up to November 1997), 441 (25%) haveinvolved fires and explosions, and 1247 (71%) haveinvolved toxic release. The remaining accidents (4%)featured a combination of fire, explosion and toxicrelease. In terms of harmful consequences, toxic releasecovers wider areas than fires/explosions. Also if the tox-icity of the released chemical is high, as was the casewith the MIC (methyl iso-cynate) leak during the Bhopaldisaster, the damage may be very severe.

The destructive impact of an explosion generallycovers a wider area than the region-of-impact of a fire.


Table 5The most gruesome transportation accidents dealing with hazardous chemicals

Year Location Chemical Incident Fatality/injury

Pipeline transport1981 S. Raface, Venezuela LPG Explosion 18/351984 Cubato, Brazil Gasoline Fire and explosion 508/311984 Ghari Dhoda, Pakistan LNG Explosion 60/111988 Mexico City, Mexico Crude oil Fire and explosion 12/801989 Nizhnevartovsk, Russia LPG Explosion and fire 462/290

Road transport1975 Texas, USA LPG Explosion 16/351978 Los Afaques, Spain Propylene Explosion and fire 216/4001978 Xilotopee, Mexico Butane Explosion 100/2001987 Preston, UK Diesel oil Fire 12/161988 Karo, Nigeria Petrol Explosion and fire 15/351995 Madras, India Benzene Explosion and fire 115/10

Rail transport1974 Decatur, USA Isobutane Explosion 7/1521978 Tennessee, USA Propane Explosion 25/501981 Potosi, Mexico Chlorine Toxic release 29/10001983 Pojuca, Brazil Gasoline Fire 10/401983 Dhurabai, India Kerosine Explosion 47/151988 Arzanas, Russia Explosive Explosion 73/230

Table 6Major factors leading to accident in the chemical industries (Lees,1996)

No. of times Proportion(%)

Equipment failure 223 29.2Operational failure 160 20.9Inadequate material evaluation 120 15.7Chemical process problems 83 10.9Material movement problems 69 9.0Ineffective loss prevention program 47 6.2Plant site problems 27 3.5Inadequate plant layout 18 2.4Structures not in conformity with use 17 2.2requirement

Secondly, except in certain cases when ambient con-ditions conspire to enable very rapid spread of a fire,most fires take time to consolidate. If emergency pre-paredness measures are in place, this time proves crucialin enabling control of the fire. On the other hand, whenan explosion takes place it does so instantly, giving notime for escape.

In a very large number of situations, explosions inchemical process industries are either caused by fire, orlead to a fire. A summary of major catastrophic accidentsfor the period 1928–1997 is presented in Tables 7–9.This information was collected by various literaturesources (Nash, 1976; Gugan, 1979; Amesz, Francocci,Primavera & Van der Pas, 1983; Lees, 1980, 1994, 1996;

Marshall, 1977, 1987; Kletz, 1988, 1991a; Lees & Ang,1984; Kharbanda & Stallworthy, 1988; Hasstrup & Bro-choff, 1990; Palmer, 1983; Prugh, 1991; Amendola,Contini & Nichele, 1988; TPL, 1992; Khan & Abbasi,1996, 1997; Koivisto, Vaija & Dohnal, 1989; Koivisto &Nielsen, 1994; Chemical Industrial Digest, 1995; LossPrevention bulletins, 1980, 1981, 1982, 1983, 1984,1986).

The worst ever accident in the chemical process indus-tries involving toxic release occurred at Bhopal in 1984.The worst ever fire-cum-explosion accident (on shore)occurred in Mexico in the same year. The worst everoff-shore accident occurred on Piper Alpha in 1988.

5. Case studies

We present below brief case-histories of typical acci-dents.

5.1. Accidents in refineries

At a refinery in France, a spillage occurred on 4 Janu-ary 1966 when an operator was draining water from a1200 m pressurised propane sphere. The propane vapourspread over a radius of 150 m and was ignited by a caron the road. The pool of propane below the sphereengulfed the vessel in flames. The resultant boiling-liquid-expanding-vapour explosion (BLEVE) killed thefireman and 17 others. The conflagration took 48 hoursto control and caused extensive damage to the refinery.


Table 7List of major accidents in chemical process industries, 1926–1969

Year Location Chemical Event Deaths/injured

1926 St. Auban, France Chlorine Toxic release 19/1051928 Homburg, Germany Phosgene Toxic release 10/501929 Syracause, New York Chlorine Toxic release 1/1001939 Zarnesti, Romania Chlorine Toxic release 60/?1940 Mjodelana, Norway Chlorine Toxic release 3/341942 Tessenderloo, Belgium Ammonium nitrate Explosion > 1001943 Ludigshafen, Germany Butadiene Explosion 57/371943 Los Angeles, CA Butane Fire 5/ > 251944 Cleveland, OH LNG Fire and explosion 128/3001944 Denison, TX Butane Fire 10/451947 Brest, France Ammonium nitrate Explosion 21/?1947 Rauma, Finland Chlorine Toxic release 19/2001947 Texas City, TX Ammonium nitrate Explosion 552/30001948 Ludigshafen, Germany Dimethyl ether Explosion 245/25001949 Perth, NJ Hydrocarbons Fire 4/261950 Poza Rica, Mexico Hydrogen sulphide Toxic release 22/3201952 Walsum, Germany Chlorine Toxic release 7/561954 Bitburg, Germany Kerosine Fire 32/161955 Whiting, IN Naptha Explosion 2/301958 Niagara Falls, NY Nitromethane Explosion ?/ > 200i1958 Signal Hills, CA Oil forth Fire 2/341959 Meldrin, GA LPG Explosion 23/781959 Kansas City, MO Gasoline Fire 5/?1959 Phillipsburg, NJ Seal oil Explosion 6/61959 Roseberg, OR Ammonium nitrate Explosion 13/741959 Ube, Japan Ammonia plant Explosion 11/401960 Forepart, TX Allyl chloride Explosion 6/141960 Kingsport, TN Aniline plant Explosion 15/551961 La Barre, LA Chlorine Toxic release 1/1141962 Doe Run, Key Ethylene oxide Explosion 2/191962 New Belin, NY LPG Explosion 10/751962 Ras Taruna, Saudi Arabia Propane Fire 1/1111962 Toledo Acrylic polyamide Explosion 10/461964 Mebronville, MA PVC Explosion 7/271964 Texas, USA Ethylene Explosion 2/341965 Louisville, KY Mono. acetylene Explosion 12/601965 Natchitoches, LA Natural gas Explosion 17/561966 Freyzin, France Propane Fire and explosion 18/831966 Larsoe, LA NGL Fire 7/201966 LaSallie, Quebec Styrene Explosion 11/101966 West Germany Methane Explosion 3/831967 Antwerp, Belgium VCM Explosion 4/331967 Hawthorn, NJ ? Explosion 2/161967 Lake Charles, LA Isobutane Explosion 7/141968 East Germany VCM Explosion 241968 Hull, UK Acetic acid Explosion 2/131968 Lievin, France Ammonia Toxic release 5/351968 Pernis, Netherlands Oil (compr.) Explosion 2/851969 Basel, Switzerland Nitro liquid Explosion 3/281969 Repcelak, Hungary Carbon dioxide Explosion 9/231969 Crete, NB Ammonia Toxic release 8/201969 Escombreaes Petroleum Explosion 4/31969 Laurel, MS LPG Explosion 2/9761969 Puerto la Cruz Light hydro. Explosion 5/231969 Teeside, UK Cyclohexane Fire 2/23

?, information not available.




1970 Philadelphia, Panama Catl. cracker Explosion 7/421971 Emmerich, Germany Ammonia Toxic release 4/531971 Houston, TX VCM Explosion 1/501971 Longview, TX Ethylene Explosion 4/601971 Netherlands Butadiene Explosion 8/211972 Rio de Janerio, Brazil Butane Explosion 37/531972 Lynchburg, VA Propane Fire 2/31972 Netherlands Hydrogen Explosion 4/401972 Weirton, WV Coke plant Explosion 10/101972 West Virginia, USA Gas Explosion 21/201973 Kingman, AZ Propane Fire 13/891973 Austin, TX NGL Fire 6/211973 Japan VCM Explosion 1/161973 Potchefstroom Ammonia Toxic release 18/341973 St. Amand L’Eaux, France Propane Explosion 5/451973 Sheffield, UK Gas works Explosion 4/241973 Staten Island, NY LNG Fire 401974 Beaumont, TX Isoprene Explosion 2/101974 Czechoslovakia Ethylene Explosion 14/791974 Decatur, IL Propane Explosion 7/1521974 Flixborough, UK Cyclohexane Explosion 28/761974 Houston, TX Butadiene Explosion 1/2351974 Madras, India Potassium sol. Hot release 9/151974 Wenatchee, WA MENiterate Explosion 2/661975 Antwerp, Belgium Ethylene Explosion 61975 Beek, Netherlands Propylene Explosion 14/1081975 Eagle Pass, TX Propane Fire 16/71975 Philadelphia, Panama Oil vapours Explosion 8/201975 Scunthorpe, UK Water-methyl Explosion 11/151975 South Africa Methane Explosion 7/71976 Chalmette, LA Ethyl benzene Explosion 13/?1976 Houston, TX Ammonia Toxic release 6/2001976 Los Angles, CA Gasoline Fire 6/351976 Gadsden, AL Gasoline Fire 3/241976 Sandefijord, Norway Flamm. liquid Explosion 6/?1976 Seveso, Italy TCDD Toxic release ?/3001977 Colombia, USA Ammonia Toxic release 30/221977 Gela, Italy Ethylene oxide Explosion 1/251977 Gujarat, India Hydrogen Explosion 5/351977 Mexico Ammonia Toxic release 2/1021977 Umm Said, Qatar LPG Fire 7/871977 Westwego, LA Explosive dust Explosion 35/51978 Chicago, IL Hydrogen sulphate Toxic release 8/291978 Santa Cruz, Mexico Propylene Fire 52/881978 St. Marys, WV Cooling water ? 51/261978 San Carlos, Spain Propylene Explosion 2111978 Texas City, TX Butane Fire 7/111978 Waverly, TN Propane Explosion 12/211978 Youngestown, FL Chlorine Toxic release 8/501979 Banter Bay, Eire Oil Explosion 50


At a refinery at Pernis (Netherlands) in 1968, an over-flow of hydrocarbon caused a small explosion. This trig-gered another small explosion which in turn led to amajor explosion with fire, extensively damaging an areaof about 300 m. Two people were killed and 85 injured(Lees, 1996).

At Texas city, USA (on 30 May 1978), one of theLPG storage vessels in a petrochemical factory(Mahoney, 1990) suffered overpressure while it wasbeing filled, due to failure of a pressure gauge and alsoof a relief valve. It cracked and leaked LPG. The leakignited into a massive fire ball, which shattered the ves-




1981 Montanas, Mexico Chlorine Toxic release 29/501982 Spencer, OK Heated water Burning 7/121983 Reserve, LA Chlorobutadine Fire and toxic release 3/121983 Houston, TX Methyl bromide Toxic release 2/111984 Brazil Gasoline Fire and toxic release 508/2211984 Roeoville, IL Propane Explosion 15/761984 Mexico City, Mexico LPG Fire and explosion 550/231985 Clinton, USA Ammonia Toxic release 5/81985 Breed Ford, UK Ammonia Toxic release 2/131985 Brazil Ammonia Toxic release > 5000 evacuated1985 Illinois, USA Naptha Explosion 7/121985 Priola, Italy Ethylene Explosion 23/111985 Algerais, Spain Naptha Explosion and fire 18/561985 Mont Belyieu, TX Propane Fire 4/131986 Basel, Switzerland Fungicide Toxic release ?/severe damage to

ecosystem1986 Ohio, USA HCL Toxic release 3/261986 Kennedy Space Center, FL Hydrogen Explosion 7/1191986 Pascagoula, MS Aniline Fire 3/761987 Grangemouth, UK Hydrocarbon Explosion and fire 67/211987 Piper Alpha Hydrogen Explosion 167/551987 Antwerp, Belgium Ethylene oxide Explosion 5/201987 Pampa, TX Acetic acid Explosion 3/431987 Louisiana, TX Hydrocarbon Fire and explosion 15/211988 Maharastra, India Naptha Fire 25/231988 Rafnes, Norway Vinyl cloride Explosion 7/131988 Narco, LA Propane Explosion 7/481989 Antwerp, Belgium Aldehyde Explosion 32/111989 USSR Ammonia Explosion and toxic release 7/571989 Baker, Gulf of Mexico Natural gas Explosion 2/241989 Worms, Germany Carbon dioxide Explosion 3/251989 Pasadena, TX Ethylene Explosion 23/3141989 Boston Rouge, LA Ethane Explosion 4/121989 Phillips, USA Ethylene Explosion 23/1301990 Channeiview, TX Waste oil Fire 5/131990 Rio de Janerio, Brazil Hydrocarbon Fire 3/?1990 Czechoslovakia Hydrogen Explosion 15/261990 Fagaras, Romania Explosives Explosion 21/341990 Thane, India Hydrocarbon Fire and explosion 35/101990 Porto de Leixoes, Portugal Propane Fire and explosion 14/761992 Sodegraura, Japan Hydrogen Explosion 10/71993 Panipat, India Ammonia Explosion and toxic release 3/251994 Dronka, Egypt Fuel Fire 410/?1995 Gujrat, India Natural gas Fire ?/?1995 Ukhta, Russia Gas Fire 12/?1996 Bombay, India Hydrocarbon Fire 2/451997 Chennai, India LPG Fire 3/41997 Chennai, India Molten metal Explosion 2/51997 Gujart, India Hydrocarbon Explosion 3/111997 Visag, India LPG Fire and explosion 60/30


sel, propelling its fragments as missiles. During the next20 minutes five horizontal bullets and four vertical oneswere damaged by missiles. The other two vessels werealso damaged in this way.

On 8 March 1984 an explosion in a refinery at Keraladestroyed a fire tender along with the shed in which itwas housed, besides a chemical warehouse, cooling

tower and other facilities. Later investigations revealedmany shortcomings in the plant layout.

On 12 December 1987 a crude oil storage tank in arefinery at Maharashtra, India, started boiling over, spill-ing its contents on the dike around it. The emergencyservices were alerted and tried to evacuate the contents.After 4 hours of pumping out, the tank caught fire and


exploded, spilling the contents. Eight hours of vigorousfire fighting had to be carried out before the fire couldbe controlled. There was extensive damage to the pro-perty. A liberal sizing of the dike and providing a separ-ate dike for a large tank like this would have helped toprevent the spread of fire to other tanks.

An accident took place on 18 April 1989 in a 14 inchnatural gas pipeline owned by a gas company in India.The pipeline was carrying compressed natural gas at apressure of about 295–298 psig from the compressorstation to various consumers. The accident occurredabout 730 ft. from the compressor station. Security per-sonnel heard a loud sound at about 09:50 h and saw ahuge cloud of black smoke emanating from the rupturedpipeline which caught fire immediately. The flame roseas high as 150 ft. during the initial stage.

The fire damaged buildings consisting of the generalstores and the office of the materials department. Twoemployees died and six others received burn injuries.Investigations revealed that the portion of the pipelinewhich had blown off was extensively corroded comparedwith other portions of the pipeline. The undergroundpipeline was close to the materials department where oldlead cells were stored. The corrosion could be due to theleakage of spent weak acid which seeped through theground and corroded the buried pipeline.

5.1.1. Maharashtra accidentOn 5 November 1990 an explosion at the offside bat-

tery of compressors at a gas cracking plant in Maharash-tra, India, killed 35 people, as well as causing heavydamage to property and business interruption losses.Among the deficiencies in the layout, identified after thedisaster, was the location of a contractor’s shed danger-ously close to the gas compressors. Less publicised, butperhaps of greater consequence, was the lack of a facilityto shut down the flow of hydrocarbon at the site itself.The plant personnel had to run to the control room fasterthan the vapour that followed them to close the feedvalve.

5.1.2. Visakhapatnam disasterOn 14 September 1997, a huge fire and explosions

devastated the terminals and storage tanks at the refineryof HPCL (Hindustan Petroleum Corporation Limited) atVisakhapatnam unit in India. More than 55 people werekilled and dozens of others seriously injured (TheHindu, 1997a).

Two bodies were found on the upper storey of theadministrative block which had collapsed while threemore were seen in the debris underneath by a team ofreporters who ventured in later in the evening. The build-ing, housing, the recreation club and canteen were alsodestroyed.

One of the eight Horton spheres or globe tanks, whichcontained LPG, crude and kerosene tanks separately,

near the main gate of the HPCL refinery, caught fire at06:40 h and exploded, rocking Visakhapatnam city. Thestorage tanks were all full, with crude imports unloadedat the HPCL berth just a few days previously. Thesecond sphere exploded 15 minutes later and beforenoon, the others also caught fire. The blaze spread. Hugetongues of flame and thick black smoke billowed intothe sky and joined the hovering monsoon clouds. Therewas a sharp shower in the morning and people wearingwhite shirts saw them turn black with soot. The rainwater flooding the road also turned black and murky.

With both the entrances to the refinery blocked byburning tanks, neither the fire tenders nor the officialscould enter the premises for several hours. Only whenthe contents in the tanks were burnt out could they ven-ture in. The death toll could have been higher had thefire started half-an-hour later when the first shift staffwould have been present.

Even more significant, as the accident occurred on aSunday, the administrative personnel, who number over200, were not on duty. There were some contract labour-ers along with the HPCL personnel in the Crude Distil-ling Unit which was shut down for routine maintenancework. The shock of the initial explosion made peoplethink an earthquake had occurred. They ran helter-skelter, leaving their belongings behind.

5.2. Accidents in chemical/petrochemical industries

On the evening of 21 September 1921, two explosionsoccurred at the Oppau works of Badische Aniline andSodafabrik (BASF) in a span of 3 seconds. Theexplosions created a mammoth crater of 80 m diameter,destroyed the plant, and 700 of the 1000 houses nearby.The explosion was caused by the detonation of some4500 t of a 50:50 mixture of ammonium sulphate andammonium nitrate. It was set off by blasting powder,which was being used to break up storage piles ofmaterial which had become caked. Exactly the same pro-cedure had been carried out without any mishap some16 000 times previously!

Even houses in the adjacent city of Ludwigshafen andin the Mannheim area were damaged. Walls were dislo-cated and windows broken. At these places and at Heid-elberg, which is about 14 miles from Oppau, the effectof the explosion was first felt by two very heavy earth-quake-like shocks. In Mannheim some seconds later, andin Heidelberg 82 seconds after the shocks, there camean enormous rush of air which broke windows and doorsand caused damage to gas holders, oil tanks, and manyriver barges. The sound of the explosion and the earthshocks reached as far as Bayreuth, a distance of 145miles, and the air pressure wave caused considerabledamage in Frankfurt, which is about 53 miles from thescene of the explosion. The explosion killed 430 people,including 50 people in the village.


On 3 July 1987 an explosion occurred inside an ethyl-ene oxide purification column at a chemical factory atAntwerp, Belgium (Lees, 1996). The explosion was dueto decomposition of ethylene oxide. It was accompaniedby a fire ball, which started a number of secondary fires.These, together with blasts and missiles, caused exten-sive damage. Fourteen people were injured.

Faulty operations at the Tomsk-7 fuels reprocessingfacility in Russia are believed to have resulted in the‘running away’ of a solution of 500 litres of tributylphosphate (TBP) saturated with strong nitric acid,resulting in explosive failure of the storage vessel andsubsequently blowing out a wall of the reprocessingbuilding. TBP is an important organic solvent used inacidic extraction steps in separation processes at fuelreprocessing facilities. Solutions of TBP, hydrocarbondiluent, and HNO3 (known as ‘red oil’ because of thecolour of nitrated hydrocarbons) undergo exothermicreactions that can thermally ‘run away’ if heated to atemperature where the heat of reaction exceeds heat loss-es.

A recent accident (14 May 1997) at Hanford was theresult of a spontaneous (autocatalytic) chemical reactionof the solution stored in a tank (Tank A-109) located inthe plutonium reclamation facility. This 1500 litre tankinitially contained a solution of 0.35 M hydroxylamine(OHNH2HNO3) and 0.25 M nitric acid called CCX sol-ution. The unused solution in the tank had been slowlyevaporating. The loss of water concentrated the solutionuntil conditions were reached that caused a spontaneouschemical decomposition reaction. The reaction created arapid release of gases, which built up pressure inside thetank. The pressure blew the lid off the tank and severelydamaged the room. No casualties were reported as no-one was near at the time of the accident.

On 25 November 1997 explosion occurred in a chemi-cal factory manufacturing rubber products at Halol inPanchmahal district of Gujrat state. Three persons werekilled and 11 others injured (The Hindu, 1997b). Theexplosion occurred in one of the reactors. Detailed infor-mation is awaited.

5.2.1. The Flixborough disasterThe Flixborough plant of Nypro Limited, UK, was

built for the production of caprolactum which is the basicraw material for the production of Nylon 6. Cyclohex-anol necessary for the production of caprolactum wasproduced by oxidation of cyclohexane. The latter chemi-cal, which in many of its properties is comparable withpetrol, had to be stored. More importantly, large quan-tities of cyclohexane had to be circulated through thereactors under a working pressure of about 8.8 kg/cm2

and a temperature of 155°C. The reaction is exothermic;any escape of cyclohexane from the plant was thereforedangerous. The cyclohexane plant at Flixborough con-sists of a stream of six reactors in series in which

cyclohexane was oxidised to cyclohexanone andcyclohexanol by air injection in the presence of a cata-lyst.

On the evening of 27 March 1974, it was discoveredthat reactor number 5 was leaking cyclohexane. The fol-lowing morning an inspection revealed that the leak hadextended by some 6 ft. This was a serious state of affairsand a meeting was called to decide a course of action.A decision was taken to remove reactor 5 and to installa bypass assembly to connect reactor 4 directly to reactor6 so that the plant operation could continue.

The openings to be connected on these reactors wereof 28 inch diameter, but the largest pipe which was avail-able on site and which might be suitable for the by-passwas of 20 inch diameter. The two flanges were at differ-ent heights so that the connection had to take the formof a dogleg of three lengths. Calculations were done tocheck that (a) the pipe had a large enough cross-sectionalarea for the required flow, and (b) that it was capable ofwithstanding the pressure as a straight pipe.

But no calculations were done which took intoaccount the forces arising from the dog-leg shape of thepipe; no drawing of the by-pass pipe was made otherthan in chalk on the workshop floor; and no pressuretesting was carried out either on the pipe or on the com-plete assembly before it was fitted. A pressure test wasperformed on the plant after the installation of the by-pass, but the equipment was tested to a pressure of 9kg/cm2. Further, the test was pneumatic not hydraulic(Lees, 1996).

The plant was restarted. Initially the by-pass assemblygave no trouble. On 29 May 1974 the bottom valve onone of the vessels was found to be leaking. The plantwas again shut down for repairs, and restarted on June1. A sudden rise in pressure up to 8.5 kg/cm2 occurredearly in the morning when the temperature in Reactor 1was only 110°C and less in the other reactors. Later thatmorning, the pressure reached 9.1–9.2 kg/cm2.

During the late afternoon an event occurred whichresulted in the escape of large quantities of cyclohexane.This event was the rupture of the dog-leg shaped by-pass system. It was perhaps aided by a fire on a nearby8 inch pipe. The escaped cyclohexane soon caught aspark, and there was a massive unconfined vapour cloudexplosion. The blast and the fire destroyed the cyclohex-ane plant as well as several other plants in the vicinity.

Of those working on the site at the time, 28 werekilled and 36 others suffered injuries. Outside the plant,injuries and damage were widespread but no-one waskilled. Of the 28 people who died 18 were in the controlroom. Some of the bodies had suffered severe damagefrom flying glass. The main office of the factory wasdemolished by the blast of the explosion. Mercifully, theaccident had occurred on a Saturday afternoon when theoffices were not occupied. If they had been, the deathtoll would have been much higher.


Property damage extended over a wide area, and apreliminary survey showed that 184 houses and 167shops and factories had suffered to a greater or alesser degree.

5.2.2. Seveso disasterOn the morning of Saturday, 10 July 1976, a safety

valve vented on a reactor at the Icmesa Chemical Com-pany at Seveso, a town of about 17 000 inhabitants some15 miles from Milan (Italy). A white cloud drifted overpart of the town, heavy rainfall brought the cloud toearth. The release occurred from a reactor producingtrichlorophenol, which is used to make a bactericide hex-achlorophenol and the herbicide 2,4,5 trichloro phenoxyacetic acid. The reactor also contained the chemical gen-erally referred to as TCDD (2,3,7,8-tetrachloro dibenzoparadioxin). This substance was not an intended reactionproduct but an undesired by-product. An estimated 2 kgof TCDD were released, although this estimate is neces-sarily approximate.

In normal operations the amount of TCDD made inthe reactor was small, but on this occasion the reactorhad got out of control. The contents had got overheatedand the safety valve had vented. The higher temperaturein the reactor favoured the production of an abnormalquantity of TCDD.

In the immediate area of the release the vegetationwas contaminated and animals began to die. On thefourth day a child fell ill and on the 5th day civil auth-orities declared a state of emergency in Seveso. An areaof some 2 square miles was declared contaminated andpeople were asked to avoid contact with the vegetationor eating anything from this area. The contaminated areawas later sought to be closed completely. On 27 July thefirst evacuation of some 250 people took place. By theend of July, 250 cases of skin infection had been diag-nosed. Some 100 people had been told to evacuate theirhomes and some 2000 people had been given blood tests.In early August it was found that the area contaminatedwas about five times larger than originally thought(Lees, 1996).

5.2.3. Other accidents involving TCDDThere have been accidents involving TCDD release

prior to the Seveso disaster. At Ludwigshafen, 55 peoplewere exposed when there was accidental TCDD releasein 1953, and many developed severe symptoms ofTCDD poisoning. Various measures were taken todecontaminate the plant building, including the use ofdetergents, the burning off of the surfaces, the removalof insulating material and so on, but these were noteffective and eventually the whole building had to bedestroyed. In another accident at Duphar in 1963, a leakof 0.03–0.2 kg of TCDD occurred. Some 50 personswere involved in cleaning up the leakage, of whom foursubsequently died, and about a dozen suffered occasional

skin troubles. The plant was sealed for 10 years and thendismantled from the inside brick by brick, the rubble wasembedded in concrete, and the concrete blocks weresunk in the Atlantic. Five years later yet another accidentinvolving TCDD release occurred at Bolsover. Itinvolved a runaway reaction in a trichlorophenol reactor,similar to the one that later occurred at Seveso. The reac-tion reached 250°C, the reactor exploded and the super-vising chemist was killed. The plant was closed down,and then reopened after 2 weeks when it appeared thatworkers exposed had suffered no ill effects. But within7 months, 79 persons complained of TCDD symptoms.The plant was dismantled and buried in a deep hole. Butthe story did not end there; 3 years later contractors onthe site developed TCDD symptoms. The only apparentpossible source of contamination was a metal vesselwhich had been thoroughly cleaned and subjected tosensitive testing.

The lesson that emerged from Seveso was that press-ure relief valves on plants handling highly toxic sub-stances should not discharge to the atmosphere but to aclosed system.

5.2.4. The Bhopal disasterThe worst ever disaster in the history of the chemical

industry occurred in Bhopal, India, on 3 December 1984.A leak of methyl isocyanate from a chemical plant,where it was used as an intermediate in the manufactureof a pesticide, spread beyond the plant boundary andcaused death by poisoning of over 2500 people—injur-ing about 10 times as many.

Methyl isocyanate boils at about 40°C at atmosphericpressure. According to press reports, the contents of thestorage tank became overheated and boiled, causing therelief valves to lift. The discharge of vapour—about 25t—was too great for the capacity of the scrubbing sys-tem. The escaping vapour spread beyond the plantboundary where a shanty town had sprung up. The causeof the overheating was contamination of the methyl iso-cyanate, by water or other materials, and several possiblemechanisms were suggested. According to some reports,cyanide was produced. Had Union Carbide conductedrisk analysis (specifically maximum credible accidentanalysis) during the design of the MIC system or evenlater, it would have learnt that in the event of a MICleak the scrubbing system would be inadequate. Thiswould have enabled the industry to install better emerg-ency handling systems, thereby saving thousands of lives(Abbasi, Krishnakumari & Khan, 1997).

5.2.5. The Worms ExplosionOn 21 November 1988 an explosion occurred in a

liquid storage vessel of Proctor Gamble, Worms, Ger-many. The explosion was supposed to be the worstamong ever explosion in cryogenic storage of liquefiedcarbon dioxide. The storage tank was a horizontal-high-


pressure vessel having a nominal capacity of 30 t of car-bon oxide and was well connected to a relief andsafety system.

The main reasons for the explosion were identified as:(a) overheating causing excessive pressure and failure ofthe relief valve; (b) brittle failure of a tank at or nearnormal operation; (c) a combination of the above. Adetailed investigation has been carried out by the FederalGovernment as well as Proctor Gamble to find the realcauses of the failure. It was found that tank was brittlefailure from two position (non uniform—faulty design).Due to excessive pressure, liquid carbon dioxide escap-ing from the relief valve reached a critical point andsealed the relief valve by forming dry ice. This preventedthe gas from escaping and hence an explosion tookplace.

The explosion intensity was so great that it destroyedtwo neighbouring units. An excess of pressure of morethan 1 atm was reported over a radius of 1000 m. Theshock wave velocity also exceeded 500 m/s. Fragmentsof vessel of more than 100 kg were found more than500 m from the site of the accident. Good planning ofthe unit’s location ensured that no hazardous chemicalswere stored nearby, so only mechanical damage tookplace.

The consequences of explosion were three fatalities atthe site, more than 10 people hospitalised and an esti-mated damage of $20 million with 3 months of pro-duction lost.

5.2.6. Pepcon explosionOn 4 May 1988 a massive explosion destroyed a

Pacific Engineering and Production Company(PEPCON) plant near Henderson, about 12 miles southof Las Vegas, USA.

PEPCON was one of only two plants in the USA thatproduced ammonium perchlorate (AP); the other was theKerr-McGee plant, also located in Henderson about 2miles from the PEPCON plant. PEPCON reportedly pro-duced about one-third of the AP used as an oxidiser andpropellant in solid, composite rocket fuels for NASA’sspace shuttle and missiles.

Although a fire started the PEPCON explosion, thecause of the fire was not easy to explain. After theexplosion, PEPCON blamed the fire on a leaking under-ground pipeline of Southwest Gas Company that tra-versed PEPCON’S property. But the natural gas pipelinehad been installed about 10 years before the PEPCONplant had been built, and although ruptured, it only con-tributed to the fire and heat required to detonate thesecond and the largest explosion.

The fire was also attributed to a welder’s torch butone of the reports absolved the welder of any blame.Some blamed the batch dryer’s fibre glass insulationwhich had a history of AP spills into the combustibleinsulation.

The following were the tell-tale conditions in andaround PEPCON:

I lack of proper storage;I combustible fibre glass insulation and sources of fire;I glass panel walls in the batch house;I inadequate spacing between adjacent process vessels

and product storage tanks;I no alarm to warn plant personnel, fire departments or

Henderson’s other citizens;I no dependable fire-fighting arrangement with sprink-

lers and deluge system;I no modern, dependable, radio system to back-up dam-

aged telephone lines needed to call for help, co-ordi-nate response teams and warn the community;

I lack of an effective emergency response plan at PEP-CON, within the surrounding industrial complex andwithin the town of Henderson.

The explosion caused about $100 million in damageto the surrounding community and completely destroyeda neighbouring marshmallow plant. About 350 personswere injured. Two persons died—the plant manager andthe controller.

5.2.7. The Phillips explosionThe explosion at the Phillips petrochemical (similar

to the present case study) plant in Pasadena, Texas, on23 October 1989 is one of the worst industrial accidentsof the last 10 years.

The immediate cause was simple: a length of pipe wasopened up to clear a choke without bothering to see thatthe isolation valve (which was operated by compressedair) had not been closed. The air hoses which suppliedpower to the valve were connected up the wrong wayaround so the valve was open when its actuator was inthe closed position. Identical couplings were used for thetwo connections so it was easy to reverse them. Accord-ing to company procedure they should have been discon-nected during maintenance but they were not. The valvecould be locked open or closed but this hardly matteredas the lock was missing. The explosion occurred lessthan 2 minutes after the leak started and two iso-butanetanks exploded 15 minutes later. The explosive forcewas equivalent to 2.4 t of TNT; 23 people—allemployees—were killed and over 130 injured. Nearly 40t of ethylene gas leaked and exploded.

5.2.8. Panipat explosionOne evening during August 1993 there was an

explosion at the National Fertiliser Limited (NFL) ferti-liser plant near Panipat, which later followed by toxicrelease and dispersion of the deadly gas, ammonia. Anaccurate official report on what happened and how, hasnot as yet been made available. However, some reliablesources reported that one evening an operator observeda leak in one of the vessels, which he reported to the


supervisor. To rectify the problem the vessel was iso-lated and repaired. After repair, the vessel was broughtback into operation without checking whether the iso-lation (slip plate) device had been removed. Pressuregradually built up inside the vessel and after a few hoursan explosion (BLEVE) occurred, spreading the contentsof the vessel over the area. As the plant was situated farfrom a populated area and the quantity was not too great,the consequences were not severe.

Four members of the operating team and two shiftengineers died, more than 25 people were injured andmore than 1000 people were adversely affected. Thepresence of proper safety arrangements prevented thedeath toll and damage from being much greater. Severedamage was inflicted on an area of around 2 km2 andthe cost of the damage has been estimated to be around$20 million.

5.3. Accidents at other facilities

On 22 June 1974 a 16 inch elbow of a pipe carryingpotassium carbonate solution in a fertiliser plant at Tam-ilnadu, India, ruptured suddenly, splashing the hot sol-ution into the nearby control room. The toughened glasspanes shattered; eight people died in the control roominstantaneously, one died in the hospital and others sus-tained grievous injuries.

On 31 August 1997 a blast occurred at Sterlite coppersmelter plant at Tuticorin, Tamilnadu state. Two peoplewere killed and two were seriously injured. Accordingto the management report, four strong blasts occurred ina rotary holding furnace in a period of 30 seconds (TheHindu, 1997c). The blasts were so intense they wereaudible even 10 km from the site of the accident. Dueto the blast molten copper and slag at a temperature of1200°C spilled out over the whole area.

5.3.1. The Siberian accidentPerhaps the most macabre accident—next only to the

Bhopal gas tragedy in its severity—occurred on 3 June1989, near Nizhnevartovsk in western Siberia. Engineersnoticed a sudden drop in pressure at the pumping endof an LPG pipeline. The pipeline was commissioned in1985 to carry mixed LPG to feed the industrial city ofUfa. Instead of investigating the trouble, the engineersresponded by increasing the pumping rate in order tomaintain the required pressure in the pipeline. The actualleakage point was about 890 miles downstream betweenthe towns of Asma and Ufa, where the pipeline wasinstalled about 1/2 mile away from the Trans-SiberianRailway. The smell of escaping gas was reported fromthe valley settlements in the area but no-one did anythingabout it. The escaping liquefied gas formed two largepockets in the low lying areas along the railway line.The gas cloud then drifted for a distance of 5 miles.Some hours later, after the main leakage had started, a

train from Nizhnevartovsk destined for the Red Searesort of Alder was approaching the leakage area whenthe driver noticed a fog in the area that had a strongsmell. The driver of another train approaching from theopposite direction (Alder to Nizhnevartovsk) saw muchthe same as he approached the west-bound train. Bothtrains were full, with a total of 1168 people on board,and as they approached the area, the turbulence causedby them mixed up LPG mist and vapour with the overly-ing air to form a flammable cloud. One of the trainsignited the cloud. Several explosions took place in quicksuccession, followed by a ball of fire that was about 1mile wide and which raced down the railway track inboth directions. Trees were flattened within a radius of2.5 miles of the epicentre of the explosions and windowswere broken up to 8 miles away. The accident left 462dead and 796 hospitalised with 70–80% burn injuries.

5.3.2. Sao Paulo accidentOn 25 February 1984, at least 508 people, most of

them young children, were killed in Sao Paulo (Brazil)when a gasoline pipe 2 ft. in diameter ruptured and 700t of gasoline spread across a strip of swamp. The causeof the pipe rupture was not reported, though it was saidto have been brought to a pressure above the safetythreshold. It was also stated that there was no way ofmonitoring the pressure in the pipeline.

5.3.3. The Basel disasterOn 1 November 1986, a warehouse at Sandoz near

Basel caught fire and burned. The warehouse containedten types of pesticide, totalling about 1200 t, and 12 tof mercuric fungicide. Most of these chemicals are toxicto both humans and animals. Around 70 to 80% of thestored chemicals have been drained out in differentforms due to fire. Although an alarm was given, the citi-zens of Basel received no relevant information and werein a state of disquiet for several hours. The health of theRiver Rhine nearby was seriously endangered. Severalmiles of the river turned a red colour and all aquatic lifewas destroyed. Nearby vegetation was also adverselyaffected.

In total, 50 000 people were affected, and approxi-mately 5 km2 of river, ground water and 2 km2 of soilwere contaminated. The total damage was estimated as$SFR 100 million.

6. Accident analysis

6.1. Fatality–frequency (FN) analysis

FN curves, also known as social risk plots, representthe probability of fatalities as a function of the numberof fatalities. Maximum fatalities have been observed infixed installation accidents (47%) followed by transpor-


Fig. 8. FN curves for transportation and fixed installation accidents.

tation accidents (34%). However, the FN curve for trans-portation accidents (Fig. 8) is more flat than the curvepertaining to fixed installation accidents, indicating thatthe probability of fatality is higher in transportation acci-dents than in fixed installation accidents. In other words,fatalities per accident are higher during transportationthan in a fixed installation. This is apparently due to theadditional risks a hazardous unit faces when it is in tran-sit compared to when it is fixed. Further, if an industrywhere a fixed installation accident takes place has anefficient emergency preparedness programme in place,the damage may be contained. Such damage control israrely possible if a vessel fails due to a transportationaccident, or during transit.

The FN curves also reveal that fires and explosionscause more fatalities per accident compared with toxicrelease (Fig. 9). The possible reason may be that onlydeaths occurring immediately after the toxic release arereported in the literature. Long-term chronic impacts—which could be very significant—do not normally cometo light. Of the total fatalities due to fixed installation

Fig. 9. FN curves for fire and explosion, and toxic release accidents.

Fig. 10. Trend of vapour cloud explosions.

accidents, about 49% have been attributed to fires andexplosions, 38% to toxic release and 13% to combi-nations of these effects. The average fatality per accidentin fixed installations is 2.32; it is 3.27 for fire andexplosion, and 2.49 for toxic release. The FN curve forfire and explosion includes fire, vapour cloud explosion(VCE), confined vapour cloud explosion (CVCE) andboiling liquid expanding vapour cloud explosion(BLEVE). The number of explosions (either type) hasbeen plotted as a function of a 5 year moving averagein Fig. 10. It is evident from the figure that during 1975–1979 a large number of explosions were reported, whilesubsequently there was a sharp decrease. To study thedamage consequence of each accidental event, FNcurves for various accidental events (explosions, fires,and toxic release) are presented in Fig. 11. It can beobserved that the curve for VCE is the flattest, while thatfor fire is the steepest, indicating that VCE has the high-est risk of fatalities while fire has the least.

Fig. 11. FN curves for various accidental events.


An illustrative table of fatality rates due to accidentsin different countries is presented in Table 10. TheNetherlands has the lowest fatality rate per accidentwhile Austria and Belgium have the highest.

7. Conclusion

From a study of the available models of accidents andcase studies, the following conclusions can be drawn.

I Most of accidents take place due to malfunctioning ofa component of equipment and/or minor negligenceof personnel during operation or maintenance.

I Although the number of accidents per year hasdeclined through the 1980s, theextentof damage peraccident has increased substantially. This is parti-cularly true in developing countries such as India.

I The damage potential of an accident depends upon thechemical in use, causative factors, operating con-ditions and site characteristics.

I The damage potential in terms of the area affected isa maximum for toxic release and depends upon thetype of chemical, meteorological conditions and sitecharacteristics.

I The impacts of fires and explosions extend over muchlesser areas but the devastation caused is moreimmediate and severe than in most cases of toxicrelease (except in cases such as the MIC leak at Bho-pal in 1989). Fire and explosions can also cause a‘domino’ effect (chain of accidents).

I The number of fatalities per accident is highest forthose involving explosions.

Table 10Fatal accidents in manufacturing industry in different countries(Raghavan & Swaminathan, 1996)

Fatality rate

Deaths per 1000 Deaths per 100 000man-years workers per year

Argentina 0.020Austria 0.142Belgium 0.140Canada 0.080 14Czechoslovakia 0.061France 0.068 11Germany (FRG) 0.120 17Germany (GDR) 0.030Italy 8Japan 0.010 5Netherlands 0.009 4Norway 0.050Poland 0.066Spain 0.109Switzerland 0.080UK 0.020 4USA 0.022 7

I Pipeline transport of chemicals is comparatively safe,provided that the line is carefully maintained and itsroute does not pass through populated areas.

I With an increase in density of industries in a complex,the probability of accidents as well as that of the dom-ino effect increase sharply.

The study highlights the need for accident forecasting,consequence assessment, and development of up-to-dateemergency preparedness and disaster management plansin the chemical process industries.

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