Case Ditails

Scenario
Case Name Explosion caused due to a change of a draw-off method of coolant in a jacket of a reactor from air pressure to steam pressure at a medical intermediate manufacturing plant
Pictograph
Date June 15, 1995
Place Kawahigashi, Fukushima, Japan
Location Chemical factory
Overview In the manufacturing process for a pharmaceutical intermediate, the reactor was heated by a different procedure from the job standard. Therefore, the reaction ran away, internal pressure rose, and the reactor exploded.
However, a fire did not occur, harmful gas flowed into the surroundings, and rescue activities became difficult.
Incident In the preparation of Benzyl chloroformate (an intermediate of pharmaceuticals), excessive carbonyl chloride in a reaction liquid and hydrogen chloride gas generated in the reaction were separated in a degassing process. As the reactor was heated accidentally by a different method from usual, the reaction ran away. The reactor exploded and harmful gas was released.
Processing Manufacture
Individual Process Reaction
Chemical Reaction Other
Chemical Equation Fig2.Chemical reaction formula
Substance Benzyl chloroformate, Fig3
Benzyl alcohol, Fig4
Phosgene, Fig5
Benzyl chloride, Fig6
Type of Accident Explosion, leakage, health hazard
Sequence About 03:00 on June 14th, 1995. 2nd lot manufacture of Benzyl chloroformate started.
21:15 on June 14th. The reaction finished and a ripening process started.
From 04:00 on June 15 to 5:30. On drawing off brine (a refrigerant) in the reactor jacket and changing to warm water circulation, the draw-off method was changed to steam pressurize from air pressurize, which was usually used.
06:00. Warm water was fed into the jacket and degassing of the reactor started. However, very small amounts of brine were recovered. The shift changed to the day shift.
08:45. As washing was poor, after draining warm wate, it was washed again with steam. Warm water was fed again.
10:00. The temperature of the liquid in the reactor rose to 50.7 °C. The warm water in the jacket was temporarily changed to cooling water. Subsequently, it was returned to warm water.
16:30. The reaction temperature was 40 °C, which was 10-20 °C higher than usual. Warm water was stopped and cooling water was fed.
Around 17:20. When an operator observed the inside of the reactor, foaming at the surface was more intense than usual. Internal pressure increased.
Around 17:35. The reactor exploded and harmful gas flowed out. Five operators left the factory. Three operators who were exposed to the bubbles washed in a shower. Two employees wearing gas masks went to rescue one operator. However, they were not successful.
17:44. An operator notified the fire department. One fire fighter was injured during fire fighting activities.
Cause On drawing off brine in a reactor jacket, unlike usual practice, steam was introduced twice. For this reason, the reactor was heated locally and benzyl chloroformate was decomposed into benzyl chloride and carbon dioxide by a reaction.
Furthermore, hydrogen chloride was generated by a condensation reaction of benzyl chloride.
Iron oxide changed to iron chloride by the action of hydrogen chloride. As iron chloride promoted a condensation reaction of benzyl chloride, the reaction ran away. The above-mentioned reaction with benzyl chloroformate etc. was clarified by an experiment after the accident.
Response A co-worker with a simple gas mask rescued the injured.
Three rescue crews, three rescue teams, and one pump vehicle party turned out.
Because of the harmful gas (Benzyl chloroformate, phosgene, a benzyl chloride, hydrogen chloride), they could not work not wearing protective devices.
Countermeasures Observance of the operation process.
Restudy of a chain of command.
Safety education on dangerous materials.
Education on the technological background of a job standard.
Installation of safety facilities and escape equipment.
As it was handling harmful gas, the reactor was not equipped with a safety valve. A receiver tank should be installed in the plant, and then safety valves and rupture disks should be installed.
Knowledge Comment When harmful gas flows out, even if the substance's name is clear, noone can deal with it without preparation of fundamental knowledge about the substance and its processing.
Therefore, when an accident occurs, after acquiring information from the person in charge of the workplace, or a specialist in hazardous properties, the fire authorities or a hospital staff should determine the method of neutralization and medical treatment.
Especially at the last lot on weekends, workers tend to lose their concentration on the work, and an intentional omission of work procedure tends to be done.
Background It was a operation standard that the temperature of the reactor was kept at 12-15 °C for the reaction and 35 °C water was sent to the jacket at degassing. In spite of being set up under such conditions, steam exceeding 100 °C was fed into the jacket. It was clearly human error. The hazard of a runaway reaction became clear after this accident. There might be no explanation regarding safety about why a low temperature must be maintained. Probably, although there was a violation of working instructions, research was also insufficient.
It is concluded that process management was insufficient. It seems a lack of recognition that harmful gas was being handled.
Incidental Discussion Sometimes a person deviates from an operation standard, but we cannot imagine the degree of deviation. Since it might be useless for them to prepare the prohibited matters in a job standard, education on common sense during operation and discipline are necessary prior to education on a job standard.
Reason for Adding to DB Example of accident caused due to misjudgment of operation methods
Scenario
Primary Scenario Poor Value Perception, Poor Safety Awareness, Inadequate Risk Recognition, Organizational Problems, Inflexible Management Structure, Insufficient Education/Training, Insufficient Analysis or Research, Insufficient Practice, Lack of Imagination, Regular Operation, Erroneous Operation, Wrong Change of Utility, Planning and Design, Poor Planning, Poor Process Design, Bad Event, Chemical Phenomenon, Abnormal Reaction, Secondary Damage, External Damage, Explosion, Bodily Harm, Death, Bodily Harm, Injury, 4 person injured, Loss to Organization, Economic Loss, Manetary Damage 160 million yen
Sources Fire and Disaster Management Agency, Explosion at pharmaceutical intermediate manufacturing process in the factory. Accident cases of dangerous materials. 1995, pp.204-205.
The Res. Inst. of Industrial Safety material. (Closed).
Number of Deaths 1
Number of Injuries 5
Physical Damage The second floor and the third floor of a three-story steel-frame building collapsed. 1/4 of a reactor was blown away.
Financial Cost ¥ 160 million. (Fire and disaster Management Agency).
Consequences Bad smell
Multimedia Files Fig3.Chemical formula
Fig4.Chemical formula
Fig5.Chemical formula
Fig6.Chemical formula
Field Chemicals and Plants
Author ITAGAKI, Haruhiko (Japan National Institute of Occupational Safety and Health)
TAMURA, Masamitsu (Center for Risk Management and Safety Sciences, Yokohama National University)
Scenario