| Case Name |
Burst of a phenolic resin reactor due to abnormal reaction |
| Pictograph |
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| Date |
December 3, 1965 |
| Place |
Aichi Prefecture |
| Location |
Chemical factory |
| Overview |
Raw materials were charged into the reactor that manufactured dihydroxydiphenylmethane by a reaction of phenol with formaldehyde at night on the previous day. By putting in the catalyst in the morning of the day, the contents were heated to the fixed 80 °C, and heating was stopped. However, the temperature continued to rise, so cooling was attempted, but a runaway reaction occurred. As a result, the internal pressure of the reactor increased and the reactor burst. One operator was injured. Although the cause cannot be specified, it is supposed that the temperature was raised too high initially, agitation was started while the temperature was rising, and vapor pressure was increased because cooling water piping was blocked, and so on. |
| Incident |
In the night on December 2nd, 1965, raw materials were charged into a reactor where dihydroxydiphenylmethane was manufactured by a reaction of phenol and formaldehyde. On the next day the catalyst was put in and the reactor was heated to the fixed 80 °C. Then heating was stopped. However, the temperature in the reactor continued rising due to an abnormal reaction. Cooling was attempted, but a runaway reaction occurred, and internal pressure increased. As a result, the reactor exploded, and one worker got injured. |
| Processing |
Manufacture |
| Individual Process |
Reaction |
| Process Flow |
Fig3.Unit process flow
|
| Chemical Reaction |
Condensation |
| Chemical Equation |
Fig2.Chemical reaction formula
|
| Substance |
Phenol, Fig4 |
| Formaldehyde, Fig5 |
| Dihydroxydiphenylmethane, Fig6 |
| Type of Accident |
Burst |
| Sequence |
Two operators charged 1140 kg of phenol and 760 kg of formaldehyde as raw materials into the reactor from 23:40 on December 2nd, 1965 to 01:40 on the following day. At about 07:30, two operators of the next shift put hydrochloric acid into the reactor to promote the condensation reaction. Then, agitation and heating with steam started. About 17 minutes later, when the temperature in the reactor had reached the fixed 80 °C, heating was stopped, and water was run through the condenser. After a while, the internal temperature of the reactor rose to about 95 °C by heat of reaction. However, bubbling was less than usual, inner pressure increased, the rubber plug at the hydrochloric acid inlet was pushed up, and the liquid level began to rise and fall. Workers thought that an abnormal reaction had occurred, ran cooling water into the jacket, and tried to lower the temperature in the reactor. However, the internal pressure continued to increase, and a whooshing sound was heard near the condenser. The reactor burst when workers felt danger and tried to escape. One of two operators got seriously injured. |
| Cause |
The following three causes were considered.
1. The operators forgot to start the agitation of the reactor at the beginning of the reaction. They remembered that they have to start the agitation and started it in a hurry while heating. Therefore, the reaction progressed rapidly.
2. Condensation became insufficient because the tubes of the condenser were blocked. As a result, the vapor pressure in the reactor increased.
3. During heating of the reactor, the temperature was raised a little higher than usual. |
| Response |
The operators ran cooling water into the jacket when the reaction was considered abnormal, and tried to lower the temperature in the reactor, but failed. |
| Countermeasures |
1. Constructing the system to confirm that agitator is surely operating. If possible, an interlock system should be equipped to prevent heating when the agitator stopped.
2. Equipment and facilities such as condensers and exhaust pipes are checked periodically.
3. Not steam but warm water should be used for heating..
4. Cooling water injection facilities for emergencies are established.
5. Pressure relief devices such as a rupture disk are equipped. |
| Knowledge Comment |
1. A backup system of hardware is necessary to prevent human errors where an operating error can cause an accident.
2. Pressure relief devices such as a rupture disk are equipped so that a reactor does not burst even if a runaway reaction occurs in the reactor.
3. Starting a batch reaction is difficult. In the temperature rise, initial temperature, temperature of the heating surface, temperature rising rate, etc. might change every time, and the thermal history of the reaction might also differ. The stability of the reaction is decided by its controllability. |
| Background |
1. There might have been operating conditions that gave priority to production yield over safety.
2. As the operation relied on the operator, the risk of human error leading to the accident is high.
3. Basically, it is necessary that an exothermic reaction, especially in a batch method operation, should be carried out with sufficient study on the facilities side, including agitation and cooling, which are basic temperature control methods, and also on the operation side. |
| Reason for Adding to DB |
Example of accident caused due to insufficient safety management of maintenance and work control |
| Scenario |
| Primary Scenario
|
Poor Value Perception, Poor Safety Awareness, Insufficient Safety Measure, Ignorance, Insufficient Knowledge, Insufficient Study, Condensation Reaction, Planning and Design, Poor Planning, Poor Design, Usage, Maintenance/Repair, Insufficient Inspection, Regular Operation, Erroneous Operation, Mis-Setting Condition, Bad Event, Chemical Phenomenon, Abnormal Reaction, Failure, Large-Scale Damage, Rapture
|
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| Sources |
Masamitsu Tamura, Masahide Wakakura, Explosion in phenolic resin condensation reaction, Reaction danger -Accident case and analysis- p.32(1995)
Ministry of Labor Industrial Safety and Health, Department safety section Explosion in condensation reactor in phenolic resin manufacturing process, Safety of batch process, pp.42-43(1987)
Ministry of Labor Labour, Standards Bureau, Reactor of phenolic resin exploded, Case and countermeasure of the plant accident, pp.527-528(1969)
|
| Number of Injuries |
1 |
| Physical Damage |
The reactor was seriously damaged |
| Financial Cost |
About ¥ 80 thousand. (Property insurance rate calculation association) |
| Multimedia Files |
Fig4.Chemical formula
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Fig5.Chemical formula
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Fig6.Chemical formula
|
| Field |
Chemicals and Plants
|
| Author |
OGAWA, Terushige (Graduate School of Environment and Information Sciences, Yokohama National University)
TAMURA, Masamitsu (Center for Risk Management and Safety Sciences, Yokohama National University)
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