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Abstract:
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The hazards associated with major accident hazard (MAH) industries
are fire, explosion and toxic gas releases. Of these, toxic gas release is the worst
as it has the potential to cause extensive fatalities. Qualitative and quantitative
hazard analyses are essential for the identitication and quantification of the
hazards associated with chemical industries. This research work presents the
results of a consequence analysis carried out to assess the damage potential of
the hazardous material storages in an industrial area of central Kerala, India. A
survey carried out in the major accident hazard (MAH) units in the industrial
belt revealed that the major hazardous chemicals stored by the various industrial
units are ammonia, chlorine, benzene, naphtha, cyclohexane, cyclohexanone
and LPG. The damage potential of the above chemicals is assessed using
consequence modelling. Modelling of pool fires for naphtha, cyclohexane,
cyclohexanone, benzene and ammonia are carried out using TNO model. Vapor
cloud explosion (VCE) modelling of LPG, cyclohexane and benzene are carried
out using TNT equivalent model. Boiling liquid expanding vapor explosion
(BLEVE) modelling of LPG is also carried out. Dispersion modelling of toxic
chemicals like chlorine, ammonia and benzene is carried out using the ALOHA
air quality model. Threat zones for different hazardous storages are estimated
based on the consequence modelling. The distance covered by the threat zone
was found to be maximum for chlorine release from a chlor-alkali industry
located in the area. The results of consequence modelling are useful for the
estimation of individual risk and societal risk in the above industrial area.Vulnerability assessment is carried out using probit functions for toxic,
thermal and pressure loads. Individual and societal risks are also estimated at
different locations. Mapping of threat zones due to different incident outcome
cases from different MAH industries is done with the help of Are GIS.Fault Tree Analysis (FTA) is an established technique for hazard
evaluation. This technique has the advantage of being both qualitative and
quantitative, if the probabilities and frequencies of the basic events are known.
However it is often difficult to estimate precisely the failure probability of the
components due to insufficient data or vague characteristics of the basic event.
It has been reported that availability of the failure probability data pertaining to
local conditions is surprisingly limited in India. This thesis outlines the
generation of failure probability values of the basic events that lead to the
release of chlorine from the storage and filling facility of a major chlor-alkali
industry located in the area using expert elicitation and proven fuzzy logic.
Sensitivity analysis has been done to evaluate the percentage contribution of
each basic event that could lead to chlorine release. Two dimensional fuzzy
fault tree analysis (TDFFTA) has been proposed for balancing the hesitation
factor invo1ved in expert elicitation . |