| Case Name |
Fire caused due to stopping an agitator of a liquid seal-type reactor during a temporary shutdown procedure at an ethylidene norbornene plant |
| Pictograph |
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| Date |
October 18, 1973 |
| Place |
Kawasaki, Kanagawa, Japan |
| Location |
Chemical factory |
| Overview |
At a plant which synthesized vinyl norbornene using butadiene and cyclopentadiene as raw materials, a liquid phase liquid tight reactor with an agitator and a cooling coil was shut down. Operators stopped agitation immediately of the liquid having the same component as in normal operation. So the reaction continued, but it was not possible to carry out cooling, and there occurred a runaway reaction. Part of the Teflon gasket was melted at the high temperature, and the liquid spouted out. The leaked material caught fire. |
| Incident |
At a plant where ethylidene norbornene, the third component of ethylene propylene diene monomer (EPDM) rubber, was manufactured using butadiene and cyclopentadiene as raw materials, a reactor where butadiene and cyclopentadiene were fed for the Diels-Alder reaction (the DA reaction) was shut down temporarily. At that time, a runaway reaction occurred because the agitator of the reactor stopped too early. The fluid leaked from the flanges of the reactor and ignited. Two operators died and two operators were seriously injured.
EPDM rubber: Abbreviation of Ethylene Propylene Diene Monomer rubber. One kind of special elastomer that is made mainly from ethylene and propylene by adding some diene as the third component. |
| Processing |
Manufacture |
| Individual Process |
Reaction |
| Process Flow |
Fig3.Unit process flow
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Fig4.Unit process flow
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| Chemical Reaction |
Addition (Diels-Alder reaction) |
| Chemical Equation |
Fig5.Chemical reaction formula
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| Substance |
Vinilidenenorbornene, Fig6 |
| Cyclopentadiene, Fig7 |
| 1,3-butadiene, Fig8 |
| Type of Accident |
Leakage, fire |
| Sequence |
At 11:30 on October 18th, 1973, it was decided that the plant was to be temporarily shut down.
At about 13:05, the shutdown procedure of the section including the DA reactor was started. This work finished at around 13:30.
Soon after stopping raw materials feed to the DA reactor, the agitator was stopped and a block valve of the pressure control valve installed at the reactor outlet was closed. The reactor pressure gradually rose. The normal operation pressure was 2.1 MPaG.
At about 14:10 and 14:15, the block valve was opened twice to reduce the reactor pressure. Then, the block valve was closed again because the pressure had dropped.
The pressure gradually started to rise again from about 14:50, exceeded 2.1 MPaG at about 14:55, and 2.2 MPaG at about 15:10. The pressure incresed suddenly, and reached over 3.5 MPaG for ten minutes, which was outside of the scale of the chart. The period of the pressure rise from 2.6 MPaG to 3.5 MPaG was only about one minute. The temperature in the reactor was also outside of the scale of the chart, which means the temperature was over 150 °C at that time.
At about the same moment, an abnormal sound was detected at the ground 15 m from the reactor and at the control room, and three operators rushed to the site.
At about 15:19, soon after the abnormal sound, a fire occurred at the upper part of the reactor. First, a flame suddenly spouted from the flange of the safety valve. In addition, a little larger flame rose from the upper part of the reactor, and after a few seconds the whole reactor was wrapped in flames. |
| Cause |
The agitator was stopped at the same liquid composition and temperature as the normal operation. In another word, the DA reactor was shut down with still having reaction potential. The valve installed at the reactor inlet/outlet was closed at that time. Therefore, cooling became impossible, and it shifted to a runaway reaction due to a temperature rise, and in addition, the temperature and pressure rapidly rose. The Teflon-made gasket of each part flange melted, high-temperature contents blew out, ignited and a fire broke out. |
| Response |
A total of 26 fire engines and fire boats of the public fire brigade, Maritime Safety Divisions, police, private fire brigades, etc. turned out to extinguish the fire. They sprayed water for cooling to prevent the fire from spreading without extinguishing the leaking gas. |
| Countermeasures |
This plant was dismantled and was not restored. After a few years, it was reconstructed at a new location in Ibaragi Prefecture. The facilities and the operation manual were reexamined at that time, and following improvements were made.
1. In the operation manual, the conditions for stopping an agitator were clarified as follows. 1) Composition in the reactor should not have reaction potential. 2) The temperature should be 50 °C or less. Urgent drawing off of the reactor fluid should be carried out when agitation stopped.
2. At the facilities level, the following were done: Duplication of power supply to important safety equipment, increase of thermometer points in the reactor, increase of the cooling surface area in the reactor, doubling of the reactor safety valve. In addition, two remote control valves, which urgently discharge the reactor fluid when hazards are sensed, were installed at the upper and lower parts of the reactor. |
| Knowledge Comment |
1. This plant was the first one developed in-house. It was the first plant to manufacture ENB domestically, and the third plant in the world, Conditions for stopping the agitator had been clarified at a certain stage. However, it was not clear on the operation site. Through each stage including laboratory research, development, process design, mechanical design, construction, a test run, and a commercial run, it is very important that sufficient consideration is given to secure safety and establish rules for transmission from one stage to the next stage, and that a follow-up system after transmission is executed.
2. All things, which have been established after a lot of efforts, might be end in failure only by just a basic mistake in operation and/or a basic judgment error. The judgment error in this case was to stop agitation. The manager and the engineering staff who run the plant must sufficiently understand not only the characteristics of the plant but also the basic operation of the plant, and they must teach them to the operators. |
| Background |
1. The shutdown method itself seemed to be wrong. The most important problem was the agitator was stopped. Why did they decide to take such a shutdown method? It was the basic accident factor.
2. The DA reaction was a comparatively large exothermic reaction, and operators had not been sufficiently taught the hazards of an exothermic reaction and countermeasures. The DA reaction is an exothermic reaction without any catalyst, and the reaction rate is decided only by composition and temperature. If agitation is stopped, cooling is conducted by only natural convection heat transfer, and the cooling power decreases remarkably. At the same time, it is not possible to cool a hot spot by mixing, even if a hot spot is generated. Naturally, the temperature of the reactor rose and a hot spot was generated easily. It is very natural a runaway reaction should occur if agitation stopped.
3. The operation manual was inadequate. It did not give clear directions on the shutdown procedure for repairs. It described that the shutdown procedure for repairs should be done according to the normal shutdown method, and it was not always concrete. Although the basic design material, which was prepared for the operation manual, stated that the reactor temperature should be 40 °C or less before stopping agitation, it was not clearly standardized in the operation manual.
4. In addition, the transmission of hazard information from the research and development side to the process engineers and from process engineers to the operation side might not have been correctly carried out.
At the research side, they might at least have known about the hazard of stopping agitation during keeping the same composition and temperature as normal operation.
However, the accurate information might not have been transmitted to the operation side. |
| Sequel |
The plant constructed later operates smoothly, and construction of the No.4 plant is being carried out in the USA. At the present they are boasting a top share in the world. |
| Incidental Discussion |
A phenomenon like bumping occurred due to a hot spot in the reactor. Therefore, a capacity of the safety valve became insufficient, and an abnormal pressure rise occurred.
There is an opinion that operators knew reaction heat could not be removed by stopping agitation, and they believed heat generated from agitation was bigger than the reaction heat. However this has not been confirmed. |
| Reason for Adding to DB |
Example in which a simple mistake in operation caused a major accident |
| Scenario |
| Primary Scenario
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Organizational Problems, Inflexible Management Structure, Insufficient Information Transfer, Organizational Problems, Poor Staff, Poor Experiment of Staff, Ignorance, Insufficient Knowledge, Insufficient Study, Diels-Alder Reaction, Non-Regular Action, Inaction, Not Change the Operation Conditions, Non-Regular Operation, Change in Operation, Agitator Stop, Malfunction, Poor Hardware, Mal HeatTransfer, Bad Event, Chemical Phenomenon, Runaway Reaction, Extraordinary Pressure Rise, Failure, Large-Scale Damage, Leakage, Secondary Damage, External Damage, Fire, Bodily Harm, Death, 2 Person Died, Bodily Harm, Injury, Serious Injury
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| Sources |
Tetsuzo Kitagawa. Fire under vinyl norbornene manufacturing. Analysis of explosion hazard. pp.251-253, pp.251-253(1980)
Kanagawa Labour Standards Bureau . Research Report on Fire Accident at Ethylidenenorbornene manufacturing plant. (1974)
Dangerous material safety research association of Kawasaki City. Accident case. It is useful at present. Examples of accidents at dangerous facilities. (with FTA). pp.17-19(1997)
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| Number of Deaths |
2 |
| Number of Injuries |
2 |
| Physical Damage |
A reactor, towers and vessels, heat exchangers, a cracking furnace, instruments, piping, and a motor burned out. About 7.5 kilo liters of a liquid mixture burned, mainly cyclopentadiene and butadiene. 99 square meters of a reaction section burned out. |
| Multimedia Files |
Fig2.Photograph of the damaged reactor
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Fig6.Chemical formula
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Fig7.Chemical formula
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Fig8.Chemical formula
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| Field |
Chemicals and Plants
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| Author |
KOBAYASHI, Mitsuo (Office K)
TAMURA, Masamitsu (Center for Risk Management and Safety Sciences, Yokohama National University)
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