| Case Name |
Explosion during preparation for manufacturing pesticide caused due to stopping of cooling water from a failure position setting error at a control valve |
| Pictograph |
|
| Date |
September 2, 1980 |
| Place |
Omuta, Fukuoka, Japan |
| Location |
Pesticide factory |
| Overview |
On September 2nd, 1980, when chlorine gas was supplied to four reactors in series containing nitrobenzene and m-chloronitrobenzene for the production of a soil germicide, the fourth reactor exploded. Chlorine flow meter failure occurred at the beginning of the operation, and a temperature controller was mistakenly switched off during repair of the flow meter. Stopping of cooling water resulted in a rise in temperature and pressure in the reactor and explosion. The primary cause was an error when setting the failure position of the temperature control valve. |
| Incident |
A temperature controller of a reactor of a pesticide manufacturing plant was mistakenly switched off, and a temperature control valve was closed completely. Then, an explosion occurred due to an exothermic reaction. |
| Processing |
Manufacture |
| Individual Process |
Reaction |
| Process Flow |
Fig2.Process flow sheet
|
|
Fig3.Unit process flow
|
| Chemical Reaction |
Halogenation |
| Substance |
Nitrobenzene, Fig4 |
| Chlorine, Fig5 |
| m-chloronitrobenzene, Fig6 |
| Type of Accident |
Explosion |
| Sequence |
Chlorine gas was supplied to four reactors in series containing nitrobenzene and m-chloronitrobenzene for the production of a soil germicide. Chlorine was supplied as follows: reactor A to reactor B, then to reactor C, and finally to reactor D; supply to reactor A was stopped during supplying to reactor B to C to D, and then supply to reactor B was stopped, and so on. When chlorine supply to reactor A was stopped, pressure and temperature of reactor D increased, and it exploded. |
| Cause |
At the start of operations, a flow meter for chlorine gas was out of control. During repairing the flow meter, a temperature controller of reactor D was mistakenly switched off, which stopped the supply of cooling water. The temperature increased in reactor D due to an exothermic reaction, and it exploded. The reason for a runaway reaction on switching the chlorine supply from reactor A to B was assumed to be temperature accumulation and increase of chlorine gas supplied to reactor D. |
| Countermeasures |
1. The failure position must be changed to "open."
2. Considering arrangement of important switches so that their failure would not affect other tasks. |
| Knowledge Comment |
1. In a system where a temperature rise can result in a serious accident, introduction of a fail-safe mechanism, such as a double check system for temperature control and supply of coolant when a temperature signal is lost, are essential.
2. Release of the whole fluid to a safe place is desirable. |
| Background |
1. The primary cause was a design error in the failure position setting of the temperature control valve. In an emergency, cooling of the reactor is required to stop or delay an exothermic reaction, so the control valve must be opened fully to feed the maximum volume of cooling water. The operator overlooked an error in failure position setting of the control valve.
Failure position; The position of the control valve (full open, full closed or stay) at control signal cut-off or at instrument air failure is set beforehand. The position is called "failure position."
2. The temperature controller switch was easily cut. It is necessary to choose arrangement and structure that do not malfunction, because if a switch of an important meter is incorrectly set, it affects other work. Consideration of human engineering was insufficient. |
| Incidental Discussion |
The failure position when an instrument air failure occurs has been thoroughly discussed. However, the failure position when the controller switch is cut-off was not always discussed. If either failure position was wrong, safety in an emergency could not be maintained. It is not the responsibility of a person in charge of instrumentation. It is the responsibility of a process designer and a person in charge of operation. |
| Reason for Adding to DB |
Example of a runaway reaction caused due to defective temperature control |
| Scenario |
| Primary Scenario
|
Organizational Problems, Inflexible Management Structure, Insufficient Information Transfer, Misjudgment, Misunderstanding, Insufficient Consideration on Instrument Design, Non-Regular Operation, Emergency Operation, Mis-design of Failure Position, Planning and Design, Poor Planning, Problem in Operation Indication, Bad Event, Chemical Phenomenon, Abnormal Reaction, Secondary Damage, External Damage, Explosion, Loss to Organization, Economic Loss
|
|
| Sources |
Ministry of Labor. Safety Section. Cases of fire and explosion disaster and countermeasures. [A]. Explosion of gas, vapor, etc. Case 2. New edition. Case of labor accidents and countermeasures. pp.202-204(1984)
Masamitsu Tamura. Masahide Wakakura. Explosion when manufacturing pesticide. Reaction danger- Accident case and analysis - p.94(1995)
|
| Financial Cost |
¥12 million. |
| Multimedia Files |
Fig4.Chemical formula
|
|
Fig5.Chemical formula
|
|
Fig6.Chemical formula
|
| Field |
Chemicals and Plants
|
| Author |
YOSHINAGA, Jun (Graduate School of New Frontier Sciences, The University of Tokyo)
TAMURA, Masamitsu (Center for Risk Management and Safety Sciences, Yokohama National University)
|
|
