The Unfolding of Bhopal Disaster
T.R. Chouhan
Ex-MIC Plant Operator
Union Carbide Plant, Bhopal
trbhopal@rediffmail.com
Abstract:
As an employee of Union Carbide India at the Bhopal plant, I know how the
disaster happened. The merciless cost-cutting severely affecting material of
construction, maintenance, training, manpower and morale resulted in the disaster
that was waiting to happen. Significant differences between the West Virginia, USA
plant and the Bhopal, India plant show the callous disregard of the corporation for
the people of the developing countries. The narrative below, if given a proper thought
by the management and governments, should help in significantly reducing industrial
accidents.
Key words: Bhopal Gas Tragedy, Safety, Industrial accidents, Methyl Isocyanate,
MIC
The Details:
Since I was an employee of the Union Carbide India before and also when the
tragic event took place on the night of December 2-3, 1984 in Bhopal, I am aware of
the sequence of events that led to it. I am here today to share my experience with
you.
To begin with, I would like to state that the disaster was not merely an
accident! Extensive details are given in Ref. 1. The points that I would highlight
subsequently will prove how such a big multi national corporation (like Union
Carbide) had little concern about the safety and well-being of people in a developing
country like ours. Not just that, even the technology they used was unproven and
faulty. For instance: Emergency procedure for MIC storage tanks for Bhopal plant as
per the MIC operating manual reads: ``If a leak develops in a tank that cannot be
stopped or isolated, the material in the tank may be pumped to another tank … There
will be exceptions to all these guidelines…. We will learn more and more as we gain
actual experience…’ It implies that they did not know the process well enough to
advise the emergency procedure in many situations.
The toxic gas that leaked into the Bhopal atmosphere that night was due to
water (along with catalytic material: iron, rust, etc.) entering the storage tank 610 of
the Union Carbide MIC plant. The phosgenes stripping still and the quench filters’
safety valves downstream (4 in numbers) were connected to the relief valve vent
header (RVVH). These lines were badly choked with solid sodium salts deposition.
The exercise of washing these filters started at 8:30 PM on 2nd December 1984.
Because of the choking of these lines and malfunctioning of RVVH isolation valve,
the water entered the RVVH main header (Fig. 1). This header was connected to the
MIC storage area. The RVVH header of storage area was also connected to the
process vent header (PVH) with a jumper line (Fig. 2 shows where the jumper line
was connected. It was removed when the remainder MIC was utilized on December
16, 1984). The blow down valve of the MIC tank 610 was malfunctioning and was in
an open position. (The tank had been unable to maintain pressure when presurrised
using nitrogen a few days earlier.) The water along with the catalytic material entered
the tank. Other MIC storage tanks, numbered 611 and 619, were holding pressure so
that they were not contaminated.
As the 42 tones of MIC in tank 610 got contaminated with water and the
catalytic material, the exothermic reactions began and within an hour, turned into
violent runaway reactions resulting in high pressure and temperature in the tank. The
reaction products and the unreacted MIC started coming out through PVH ® Jumper
line ® RVVH ® VGS and finally to the atmosphere through the atmospheric vent
line and overflow vent line of scrubber, between approximately 12:15 AM to 2:30 AM
The safety equipment provided for the Bhopal plant were as follows:
1. Vent Gas Scrubber (VGS): It was designed to neutralize the toxic release
material released from various equipment of MIC plant. However, it was not
capable of controlling the runaway reaction. (Further, it was not operational
that night).
2. Flare tower: It was designed to burn out excess CO and MIC vapors at a
controlled rate and was not capable of burning the huge amounts released
that night. (Further, it was under maintenance that night).
3. MIC storage 30 tones refrigeration system: It was installed to keep the
storage tank material below 5o C. (However, the system had been shutdown in
May 1984 to save power, approx. $ 20 per day).
4. Water spray: This could be used to knock out the toxic chemical vapor by
spraying large amount of water. But, while the toxic gases were released at 30
– m (100 ft) above ground, the water spray could not reach that height and
hence could not knock out any gas.
5. Danger alarm (siren): Installed for warning the community people, was
switched off after 5 minutes as per the revised company policy. Thereafter,
only the muted siren for the plant personal was sounded. No plant person
died due to the gas. If the loud alarm for the community had been sounded for
long, many would have escaped before the gas overpowered them.
6. Evacuation plan: It was only made for the plant personal, not for the
community.
The management had told the workers that the Bhopal plant was designed
and built on the basis of 20 years’ experience in making MIC in the West Virginia,
USA plant. We felt excited knowing that we were going to work in a modern,
sophisticated and automatic chemical plant. After the disaster, I came to know of a
lot of differences between the MIC plants in W. Virginia and Bhopal (Table 1). It is
evident from Table 1 that the Bhopal plant was not designed to handle emergencies
that the West Virginia plant could have.
CAUSES BEHIND THE BHOPAL GAS DISASTER
The order for water washing was given without
Placing slip blinds
Checking related lines
Disconnecting various lines.
Sodium Hydroxide (NaOH) solution, in the VGS unit and field storage tanks,
was insufficient for neutralization of such a large amount of gas.
The pressure control valve for the MIC storage tank (610) had not been
functioning for over a month. Water entered through this route.
The temperature sensor and alarm for the MIC storage tank had not been
working for almost 4 years. Therefore, regular recording of temperature in the
log sheets was not done. According to the officers this parameter was not
important. However, it could have warned of the runaway reaction occurring
much earlier.
The refrigeration unit (30 Tones capacity) had been 'down' for over an year,
and was totally shutdown in May 1984. As a result the MIC tank was at
ambient temperature while the MIC manual had strongly recommended
keeping MIC below 5o C.
The Vent Gas Scrubber was not operating at the time of the accident.
The flare tower had been under maintenance since Nov. 25, 1984 and
maintenance was not completed until the accident. The job could have been
completed within 8 hours but for the shortage of staff
Manpower was reduced in all categories (Fig. 3)
Fire and rescue squad (emergency squad) members were not qualified and
trained to handle such an accident.
There was no maintenance supervisor for the night shift.
Nobody was aware of such types of runaway reactions in the storage tank
and therefore proper emergency steps were not taken.
MIC plant operating personnel did not have the qualifications and training that
were necessary. Training had been reduced over the years (Fig. 4)
The agreement between the union and the management was completed in
1983 by-passing the safety rules.
Improper behavior of management with the operating personnel.
Incorrect modifications of the Relief Valve Vent Header (RVVH) and Process
Vent Header (PVH) by providing interconnection with a jumper line in the MIC
storage area (Fig. 2)
The design and technology given by the Union Carbide Corporation was not
safe and sufficient for preventing contamination and controlling runaway
reaction.
The loud siren did not start at the proper time and was shut down after 5
minutes since the siren policy had been modified.
There was no evacuation plan for the neighboring area/communities. Even
after the accident the neighboring communities were not informed.
The Plant superintendent did not inform outside agencies about the accident.
Initially, they denied the accident, and then stated that MIC gas was like a tear
gas and the effects would be temporary. No effective antidote was told.
The civic authorities did not know the treatment since they had not been
informed of the extremely hazardous nature of the material stored.
Keeping all the above developments in mind, no one should be surprised that
such a major accident took place. It was waiting to happen.
My objective in this presentation is to see that such disasters are averted all
over the world. I do hope that MNCs while investing in such projects in developing
countries would be as concerned and careful of the safety and well being of the
recipient country people as they would be of their own.
Reference
Chouhan, T. R. and others (2004), ‘Bhopal – The Inside Story’, 2 nd edition, Goa,
India: Other India Press; New York, USA: The Apex Press
Figure-1: Four Quench Filters and RVVH Isolation Valve (with wheel, top right)
Figure-2: Jumper line was connected to PVH line (left) and RVVH line (right, larger
diameter)
MIC escape
point
Figure-3: Vent Gas Scrubber. MIC came out from the tall pipe left of centre
Figure-4: Flare Tower
1979-80 1981-82 1984 1984 Nov
Figure-5: MIC plant supervisory/operating staff; declining numbers 1979-84
1975 1977 1978 1979 1980-82 1984 1984
8 Nov-Dec
Figure-6: Duration of training programme for operators of UC plant, Bhopal
Relative safety of MIC plant based on its design, operation, maintenance,
number of staff and their training 1984
1979-81 1982-83 1984 Nov- Dec
1980 1981 1982 1983 1984
Year
Figure-7: Declining number of trained staff; operators and supervisors at MIC plant.
Transferees from other plants had less training.
1979-81 1982-83 1984 1984
Nov- Dec
Figure-8: Relative safety of MIC plant based on its design, operation, maintenance,
number of staff and their training
Table-1: Comparative Design of Union Carbide MIC Production Plants in West
Virginia, USA and Bhopal, India
West Virginia plant Bhopal plant
All lines and instruments spread out over whole On one single manhole
tank
Computerized control No computerized control
PVH and RVVH lines: 304 SS C- Steel (although prohibited due to safety
considerations)
Unit storage tank between MIC manufacture and No such tank
large storage tank to check purity
4 Vent Gas Scrubbers (VGS, inbuilt redundancy) 1 Vent Gas Scrubber (No redundancy)
VGS had no atmospheric vent VGS released gases into air. This caused the
tragedy
2 Flare towers (FT, inbuilt redundancy) 1 Flare tower (No redundancy)
Designed for emergency MIC release Designed for occasional releases only
VGS, FT operational around the clock due to Not available when shutdown for repairs
redundancy
Intermediate, non-interactive refrigerant Direct brine as coolant: Could react with MIC in
case of leak
α-Naphthol added through pipe line α-Naphthol added manually from jute sacks after
opening MIC reactor manhole. Several other
hazardous operations performed manually
Pressure, Temperature, Level instruments Not trustworthy; Temperature indicator worked
functioned well only the first few months
PVH and RVVH lines from storage tank direct to Lines from other equipment also joined these
VGS and Flare tower lines. Probability of contamination of MIC high
Contd…
MIC Storage temperature ≤ 5oC < 5oC when drums being filled to minimise
vapour loss. Refrigeration shutdown since May
1984. Power saved (~ $ 20/day) > Cost of MIC
vapour loss
Operation and maintenance under trained, Not so (training and number declined)
experienced staff, enough in number
Complete evacuation plan for community in place No evacuation plan for community
Hospital, train, road, river transport, police, civic No such arrangements existed
administration informed in an emergency
