| Case Name |
Dust explosion of purified anthracene powder in a weighing hopper |
| Pictograph |
|
| Date |
April 2, 1986 |
| Place |
Ichikawa, Chiba, Japan |
| Location |
Chemical factory |
| Overview |
The weighing hopper was struck with a mallet when purified anthracene particles were dropped from the weighing hopper to the product hopper. In the following work, 30 kg of anthracene was dropped from a cushion hopper to the weighing hopper. The anthracene powder floated in the weighing hopper entered the range of explosion. The anthracene particles ignited, and there was an explosion. Static electricity generated by the falling particles was considered to be the ignition source. There seemed to be a weak awareness of the danger. |
| Incident |
A dust explosion occurred during weighing purified anthracene powder. The product after weighing was dropped from the weighing hopper to the product hopper. The next lot to be weighed was dropped from the cushion hopper to the weighing hopper. The joint of the hoppers was damaged by fire with a loud sound, and a hot blast spouted out. Anthracene caused a dust explosion. |
| Processing |
Manufacture |
| Individual Process |
Rundown and takingout |
| Process Flow |
Fig2.Unit process flow
|
| Substance |
Anthracene, Fig3 |
| Type of Accident |
Explosion |
| Sequence |
Anthracene was dropped into the product hopper after purified anthracene was weighed by a weighing hopper. The operator struck the weighing hopper with a mallet to assist the dropping of material adhering to the weighing hopper. After all of the powder had dropped into the product hopper, the cut gate between the weighing hopper and the cushion hopper was opened, One or two seconds after 30 kg of anthracene in the cushion hopper dropped, a fire occurred. The weighing hopper was earthed. |
| Cause |
Anthracene particles float in the weighing hopper because they are very fine, and the concentration of anthracene was in the range of explosion. Static electricity was generated when a large amount of anthracene was dropped from the cushion hopper, and it ignited the floating particles. |
| Countermeasures |
1. The earth should be perfect. Not only the weighing hopper but the whole facilities should be earthed so that air in the hopper should not be charged.
2. The oxygen concentration in the hopper should be controlled. Nitrogen substitution, etc. should be studied.
3. The transfer method should be changed to reduce dust. |
| Knowledge Comment |
Fine particles are readily floating, even if they are solid particles, and also become a cause of dust explosions. It is necessary to pay the same attention as to a volatile liquid. |
| Background |
There was no recognition that there was a dangerous condition.
1. There was a danger of entering the range of explosion due to powder floating.
2. There was not a perfect earth. In particular, the earth of suspended substances is very difficult. |
| Incidental Discussion |
This accident is difficult to be understood. According to the accident report, the work procedure at the time of the accident seems to have been usual. It is not clear whether there was any change to the work when the accident happened or whether there was always danger in transfer work. Although it is indicated that the device was struck with a mallet, it is not written that the act increased the suspended particles. |
| Reason for Adding to DB |
Example of explosion of fine solid powder due to static electricity |
| 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, Usage, Operation/Use, Planning and Design, Poor Planning, Poor Design, Bad Event, Thermo-Fluid Event, Static Electricity, Secondary Damage, External Damage, Explosion, Bodily Harm, Injury
|
|
| Sources |
Japan Industrial Safety and Health Assoc, The details of accident situation.
Japan Industrial Safety and Health Assoc. Safety and health information center, Case of labor accident No.644. Explosion in purified anthracene weighing hopper. The Japan Industrial Safety and Health Assoc. home page.
|
| Number of Injuries |
1 |
| Physical Damage |
A canvas at the joint of a cushion hopper and a weighing hopper was damaged by fire. |
| Multimedia Files |
Fig3.Chemical formula
|
| Field |
Chemicals and Plants
|
| Author |
KOBAYASHI, Mitsuo (Office K)
TAMURA, Masamitsu (Center for Risk Management and Safety Sciences, Yokohama National University)
|
