is still alive. It will always alive till the concept
of safety will alive, search of cause of accidents
and remedial measures will alive and chemical threats
of humanity will alive.
is said and published about Bhopal disaster. Still
its talk is continued. This is because of the gravity
of the accident causing deaths of more than 2500 lives,
more than that badly affected, claims of lacs of rupees,
politics penetrated and ultimate closer of the factory.
such severe accident took place and how can we prevent
similar reoccurrence is an important lesson of Bhopal
incident. It has the opened the eyes of our people
and created worldwide safety awareness. That is why
we have selected, first, this unique example to explain
the concept of safety, causation analysis and basic
rules of accident prevention.
facts of the accident in brief
It was the night of 2/3 December 1984 when the night
shift staff of the Union Carbide factory, Bhopal,
took around 11 p.m. There were double-walled, partly
buried S.S tanks (No. 610,611 and 619), each of 60
tones capacity and all containing the poisonous gas
MIC (Methyl ico cyanate) to be used to produce a deadly
pesticide carbaryl. At @ 11-30 p.m, workers in the
plant realized, there was an MIC leak somewhere: their
eyes began to tear. A few if them went to the MIC
structure and noticed a drip of liquid with yellowish-white
gas, about 50 feet of the ground. They told the supervisor,
who, however, decided to deal with the leak after
the tea-brack which ended at 12-40 a.m when the events
had moved very fast. The temperature of the tank 610
and reached 250C, the top of its scale and the pressure
was increased twenty time rushing towards 40 psi at
which the emergency safety valve was to open. Soon
the pressure gauge showed 55 psi, the top of the scale
and the safety valve had opened releasing MIC with
a loud hissing sound and the tremendous heart. A white
cloud drifting over the plant was moving towards the
The workers tried to operate the safety devices, but
nothing seemed to work. The water jet failed to reach
the top of the 120 feet stack from which MIC was escaping.
The vent gas scrubber to neutralize the escaping gas
did not work. The scrubber was under maintenance;
the flow meter was not indicating the circulation
of caustic soda whose concentration was also not known
since October. The flare tower to burn off the gas
could not be used because its piping was corroded
and not replaced. The refrigeration system, of 30
tone capacity to keep the MIC in liquid state at 0
c was closed down since June 1984 as an economy drive
and the gas was at 150-200C which was unsafe. For
approximately two hours, the safety valve remained
opened releasing over 50,000 pounds of MIC (might
also containing phosgene, chloroform, hydrogen cyanide,
carbon dioxide etc) out of 90,000 pounds stored in
the tank 610 at the time of the incident. Sometime
between 1-30 to 2-30 am the safety valve reseated
as the tank pressure went below 40 psi.
The Causes of the Accident
the published press reports they seem to be:
The refrigeration system to keep the gas cool
was since long.
The vent gas scrubber was under designed, not
The corroded flare tower pipe not replaced
and not connected
The water curtain jets were undersigned to
reach the maximum
All the three tanks were filled in while one
ought to have kept
empty to use as emergency bypass.
The computerized pressure/temperature sensing
warning device to give alarm and to control
the situation at
the time of abnormal condition was no
The carbon steel valves were used instead of
and the valves were notorious for leaking.
The instrument to check the valve-leakage were
The wind direction and velocity indicator was
not installed to
warn the people about leakage direction
The neighboring community was not told of the
the danger alarm and the dangers posed
by the material used
in the Plant.
Control instruments at the plant were faulty.
Maintenance and operational practices were
Chemical reactors, piping and valves were not
and aired before maintenance operations.
The slip blind to disallow the water in the
tank through the
valve was Missing.
Under qualified workers were running the factory.
People with chemical engineering background
were replaced by
less Skilled operators.
The strength was reduced from 850 to 642 during
two Years and the operations duty relieving
The operation manual was grossly inadequate,
all necessary emergency procedures to
At the time of accident, n the MIC control
room, there was
only one operator who found it virtually
impossible to check
the 70-odd panels indicators and controllers.
A design modification of jumper line
to interconnect relief
valve vent Header and the process
vent header was defective,
as it allowed the water to go into the
The leak was not attended as soon as it was
The first information of, five-fold pressure
rise was dismissed
in the belief that the pressure
gauge could be faulty.
A newly recruited supervisor had asked a novice
clean a pipe and slip blind was not inserted
while doing so
The public siren was put on around I am
nearly an hour after
the gas leakage, and that too for a few
The correct antidotes and medical treatments
suggested to surrounding doctors. On the
of MIC or phosgene or hydrogen cyanide
Above unsafe conditions and actions lead to the violent
unsafe reaction. Different hypothesis have been expounded
by carbides scientists, Indian exerts and Dr.S.Varadrajan,
who lead the investigations on behalf of the government.
According to him small quantity of water reacted with
phosgene in the tank, mixed with MIC as an impurity
to keep it stable. The phosgene water reaction produced
heat co and HCI. The heat and HCI acted as the accelerators
of the polymerization of MIC leading to a runaway
reaction. According to others, the increased temperature
of MIC (It vaporize above 38 c) generated heat, pressure
and side reactions, higher than normal amount
of chloroform in the stored MIC and an iron catalyst
lead to the violent reaction. Because of the colder
night of December, the escaped MIC settled down and
traveled downward covering the sleeping surroundings
with the blanket of death and damages.
All the 25 major causes of accident described above
in (A) and (B), suggest the remedial measures. To
avoid repetition all these contributing causes should
be removed first and necessary steps should be taken
to run the plant always safe and sound, with all the
safety devices properly working. The working conditions
must be improved and unsafe actions must be removed
by proper policy, training and education.
The Lessons and Increased Need of safety
The lessons will last for so many years. They are
General safety awareness must be increased
Factory owners and trainers must open their
eyes to pay more
attention on safety, Particularity to provide
and maintain safety
devices and to improve the working conditions.
Workers including staff and supervisors must
Authorities must go in much details and must
compliance of safety rules .No politics
Necessary amendments must be made in safety
Safety literature, education and training must
Wide publicity must be given to safety programs
and safe work
practices on Radio, T.V., Newspapers
to make alert and
educated the people maintain high standards
Safety councils, Labour Institutes and Associations/Unions
employers and employees must increase
All safety inspections must be carried out
sufficient time, and for this purpose, the
number of inspectors
must be increased. All authorities under various
must take care of their provisions to uplift
the manifold aspect
The Government must provide more funds for
vehicles, instruments, literatures etc
and towards aid/subsidy
for safety planning.
All these lessons point out the increased need of
safety. It recalls the basic concept of safety and
basic rules of behavior. They are explained below
concept of safety
Safety, in general terms means freedom or protection
from danger. In an industrial context it means the
minimization of contact between human and hazard and
is predominantly concerned with the prevention of
physical harm (injury) to an individual. This is an
age-old concept as well as specific. Basic concept
needs all basic, general, fundamental and primary
safety rules, while specific concept includes specific
safety knowledge to solve specific problems. The concept
is engineering and physiological, scientific and human.
Branches (Area of work)
Industrial, Environmental, Road and Home safety are
the main branches. Mechanical, Chemical, health and
hygiene etc may form sub branches.
The coverage of concept of safety is very wide. It
included all branches of engineering, science and
technology health and hygiene.
The concept Development:
(2) Total Loss control and
(3) Total Loss prevention
may be defined as an unexpected, unplanned event in
a sequence of events, that occurs through a combination
of causes. It results in physical harm (injury or
disease) to an individual, damage to property, equipment,
buildings etc, a near-miss, loss to the company, or
any combination of theses effects.
Control may be defined as a management system to reduce
or eliminate all accidental loss or wastage of manpower,
materials, machinery, methods, and product, money,
Loss prevention may be defined as the application
of engineering techniques in order to reduce the occurrence
of accidents that result in personal injury, damage
to property, product, equipment, buildings etc and
those accidents that have no end result in the near-miss
safety included all above aspects in chemical fields.
study the causes, chances or probabilities of accidents.
They may be unsafe conditions, unsafe actions or their
combination. Many illustrations can be given to explain
this broad classification. Our illustration of Bhopal
accident throws light on this classification.
on above determination and further study find out
the appropriate remedial measures and apply them.
Safe trail and error method may also be useful.
basic attitudes, general principles or basic rules
of safety are given below. They are applicable to
things make perfection but perfection is no small
thing. Safety should be made perfect by smallest precautions.
of a problem lies through the problems. To achieve
safety try through all stages in sequence.
Safety is duty as well right. Perform the duty and
enjoy the right.
(4) It is the knowledge that works and not the designation.(like
it is not the gun that
Fires, but it is the heart of iron which fires the
(5) Increase the knowledge of safety, first perpendicular
(ie in your own branch),then
Horizontal (ie in other or side branches)
March beyond basic, from known to unknown, from general
to specific, from divergence to convergence. Be the
master of your subject.
(7) Be useful and humane to others. Fit the unfit
Safety is human Engineering. Human must be at the
Be always safety minded. Develop safety eye safety
outlook and improve safety controls. Safety devices
should be failsafe.
Rules of safety should be absolute and not negotiable.
these rules always in mind. They will help you to
meet with the increased need of safety.
Though safety in each field is of equal importance,
safety in chemical field needs more attention because
of its specific nature. Chemical safety seems more
complicated than civil, mechanical or electrical safety,
because each chemical has many properties, many process
many hazards and many controls. The state pressure,
temperature, process parameters etc ,are also changeable.
Many hazard data and complete reaction documents are
still not available. Many hazards are known after
the accident only as incase of Bhopal and so many
incidents. Engineering controls may not be possible
or available at many places. Control devices and personal
protections are inadequate many times. Warning devices
may either not be available or not be functioning
well All these diversified working conditions and
operational situations pose many dangers which need
their proper knowledge and attention followed by proper
safety measures and proper preventive as well as corrective