Transcript A Review of Models for Chemical Hazard Mitigation - Hrdp

Risk Assessment for
Chemical Disasters
A Presentation by
P.S. Dutt
Scientist and Head, BDU
NEERI, Nagpur
National Training Course on
Chemical Disaster Management,
NIDM, New Delhi
August 16-20, 2010
Chemical Hazard: Characteristics
 Manmade and technological disasters
 Prevention and control is possible
– At design, operations and post operations
 Chemical hazards and emergencies
– Manufacture, storage, transportation , handling,
waste management
 Chemicals in environment vs chemicals and
development
Aim is to enhance intrinsic safety of
chemical plant design & operations
Hazards and consequences
 Hazards (Fires, explosions and toxic releases)
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Flammability
Reactivity
Toxicity
Corrosivity
 Causes
– Design
– Operations
– Human error
 Consequences
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Loss of life and injury
Loss to Plant & Machinery
Onsite and offsite
Environmental damage
Past Accidents
 Flixborough, UK (June 1, 1974)
Due to a rupture of bypass assembly, about 80 tonnes of hot liquid
cyclohexane (at 155o C and 8 bar pressure) escaped at sonic velocity
forming thick clouds as big as football pitch which exploded within a
minute of the rupture. The intensity of explosion was equivalent to 30
tonnes of TNT. It wrecked the total works and main office block and
damaged property within a radius of 5 km. 28 persons working in the
control room were killed and more than 100 persons were injured
including those in off-site area.
 Bhopal, India (December 2, 1984)
Due to a leak of toxic MIC gas, more than 2500 persons died and several
thousand injured. In the long term, about 16,000 people died as a result of
exposure to the gas. More than 5 lakh claims for injuries and losses were
recorded.
Past Accidents
 Visakhapatnam, India (September 14, 1997)
Due to a leak from a flange of a pipeline while unloading
LPG from a tanker to refinery LPG sphere, a vapour
cloud was formed in the early hours which led to the
explosion of LPG sphere at 6.40 AM. As a result of this
explosion, 5 LPG spheres in the tank farm (of 7 LPG
spheres), 3 petroleum product tanks of the refinery and
11 petroleum product storage tanks in the adjoining
marketing terminal were caught fire. Three buildings of
the refinery including control room were collapsed.
The pressure wave damage was widespread and
extended up to Air Port Control Tower. About 1 lakh
people were panic stricken. The fire was extinguished
after two days.
Current Scenario
Purpose of Models
 To represent facts and reality objectively
 To analyse logically and systematically all relevant
facts
 To build confidence by presenting quantitative
assessment and accuracy
 To provide meaningful insights under varying
scenarios in accordance with considered view of
human/public perception
 To serve as handy tools for effective decision
making
Characteristics of Models
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Several assumptions
Scientific – deterministic/probabilistic/fuzzy
Empirical – facts and event driven
Accurate data and information driven
Uncertainty
Range of models for specific needs
– Modelling systems and softwares
– Location specific models – GIS based
– Expert systems
– Online and offline systems
Models for CHM
 Pre-disaster planning
– Hazard identification
 Chemical/process/operation
 Fire/Explosion/Toxic release/combination
– Consequence analysis
 Loss to property/Risk evaluation/environmental decay
– Emergency planning
– Loss prevention
– Training
 Post-disaster planning
– Accident investigation
– Review of procedures
– Learning
Models for Risk Assessment
Purpose
Technique
Application Data reqd.
Haz. identification
Engg.
Early design
judgement
stage
FETI
NFPA
Thermochemical
analysis
Properties
Process sequence
Operation details
Safety data sheets
Equip. specs.
Haz. effects
HAZOP
Chem. Outflow
Effect scenario
Modelling
accident
Safety audit
Process flow sheet
P&I D
Engg. Drawings
Operations
manuals
Equip. specs
Met. data
Late design
Redesign of
existing
Models for Risk Assessment
Purpose
Technique
Application Data reqd.
Consequence
analysis
WHAZAN
EFFECT
SAFETI
ARCHIE, etc
Late design
Redesign of
existing
Plant layout
Past accident
information
All above
Probabilistic risk
assessment
System reliability
ETA/FTA
FMEA
QRA
Late design
Redesign of
existing
Failure probability
Accident data
Human reliability
All above
Risk mitigation
Accident analysis
Emergency mgmt
CAMEO
APELL
Late design
Redesign of
existing or
Post disaster
All above
(outflow,
dispersion,
evaporation,
radiation,
BLEVE,VCE)
Meteorological Scenarios
Options for LPG Storage
Sl.
No
Item
Cryogenic
Pressurised Cavern
1
Size (m3)
10,000 to
1,00,000
1,000 to
5,000
10,000 to
5,00,000
2
Facility Cost(Rs.
per T)
20,000 to
45,000
30,000 to
55,000
10,000 to
30,000
3
Operating Cost
High
High
Low
4
Land for 60,000 T
50 acres
60 acres
Minimal
5
Rate of tanker
discharge (T/hr)
1000
300
1000
6
Safety
Addl
controls
Addl
controls
Inherently safe
Results of Risk Analysis
Conclusions
 Chemical plants and installations are a necessity
for development
 Safety and environment concerns warrant safe
design of chemical plants
 Emergency preparedness needs scientific basis to
plan for onsite and offsite
 Models and risk assessment provide tools to
enhance inherent safety of design and
containment thereby mitigation of accidents
 Risk assessment (PRA/QRA) is inexpensive and
effective when compared to losses due to
accidents
 Training and development of qualified personnel is
the need of the hour
Thank You