| Case Name |
Fire caused due to back flow of dimethylamine during repairing work of piping from a reactor to a scrubber |
| Pictograph |
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| Date |
April 29, 1995 |
| Place |
Kawasaki, Kanagawa, Japan |
| Location |
Chemical factory |
| Overview |
On April 29th, 1995. A fire occurred when remodeling was carried out at equipment in a chemical plant in Kanagawa Prefecture. At a reactor that synthesized polyoxyethylene nonyl ether, repair work, including hot work, was being done, in which an emergency discharge manual valve was changed to a remotely operated automatic valve. Dimethylamine remained in the scrubber, which was the discharging point. However, mandatory insertion of a blind plate was not carried out. Therefore, the dimethylamine flowed back, and a combustible gas-air mixture was formed. Combined with careless use of tools that generated sparks, an accident occurred. In particular, a careless repair method that infringed safety regulations was a problem, as well as the assumption that there was a check valve. |
| Incident |
Replacement of the manual valve to the automatic valve was carried out at vent piping from the reactor (R-12) that synthesized polyoxyethylene nonylphenyl ether to a scrubber. To adjust the length of a newly mounted valve, part of the piping was cut off with an electric saw. Then, when the cutting face was being polished with an electric grinder, flames came out from the vent piping. Two workers in the vicinity suffered burns. The upper part of the scrubber had been opened to the atmosphere. |
| Processing |
Manufacture |
| Individual Process |
Maintenance |
| Process Flow |
Fig2.Unit process flow
|
| Substance |
Dimethylamine, Fig3 |
| Type of Accident |
Fire |
| Sequence |
On April 29th, 1995, about 09:00. Before doing hot work using an electric saw and an electric grinder, atmosphere was checked by the combustible gas detector. A blind plate should have been installed at the connection flange, but the repair worker (subcontractor's worker) neglected this.
About 14:00. The manual valve was detached. The inlet side piping of the valve was cut off using an electric saw to install a new automatic valve.
About 14:36. An electric grinder was used to polish and finish the cutting face. At that time, flames spouted about 1 m from the opening of lower piping. Two workers received burns to their hands. |
| Cause |
Formation of a combustible gas-air mixture:
Vent piping from another reactor (R-20) was also connected to the scrubber. While the reactor R-20 was working, dimethylamine was discharged to the scrubber. As the connection valve from the reactor R-12 to the scrubber was open, dimethylamine gas flowed back from the scrubber. A combustible gas-air mixture was generated in the reactor before the valve was disconnected.
In the operation standard, the operation was considered as in-tank work, so it was necessary to measure the combustible gas concentration in the tank. However, measurement was not carried out and a combustible air mixture formed was not detected. The person related was convinced a check valve had been set in the connecting piping and did not think about the back flow.
Ignition cause:
The combustible gas-air mixture was ignited by a spark of the electric grinder. Since a blind plate was not installed at the flange, the gas reached a place where sparks were generated. |
| Response |
Flames were self-extinguished. As black smoke was coming out from the opening, other workers blew dry chemicals into the reactor from the opening. |
| Countermeasures |
Improving safety education. In particular, sufficient arrangements must be made in advance by the repair operation department, the facilities management department, and the subcontractor before repair work.
A check valve is installed in the vent piping leading to the scrubber
During important work, including hot work, operators should make it a habit to confirm the plant situation with drawings such as P&ID and others and do field checks without depending only on human memory. |
| Knowledge Comment |
Safety management is the responsibility of the company. Besides, the following can be pointed out.
Thorough safety education and safety management for subcontractors are important. In particular, close attention is necessary to repair in a complicated plant. Safety education for subcontractor's employees is also important. |
| Background |
When operation stopped, there was a possibility of a back-flow because the pressure balance had changed. Therefore, for safety, a blind plate must be inserted into piping that is open to the atmosphere.
It is not permitted to depend only on human memory. In principle, construction equipment should be checked using P&ID and other drawings. |
| Reason for Adding to DB |
Example of fire during plant repairing work |
| Scenario |
| Primary Scenario
|
Ignorance of Procedure, Disregard of Procedure, No bliud Plate, Organizational Problems, Poor Management, Slackness of Management, Misjudgment, Misperception, Mis-Convincement, Malicious Act, Rule Violation, Safety Rule Violation, Secondary Damage, External Damage, Fire, Bodily Harm, Injury, 2 person injured
|
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| Sources |
Kawasaki City Fire fighting station. Prevention division. Peace section. Fire accident at reactor of N Co. K factory. Material of the Kawasaki City complex safety countermeasure committee. (1995)
|
| Number of Injuries |
2 |
| Physical Damage |
Three automatic valves and instrumentation cables were destroyed by fire. |
| Financial Cost |
¥ 80,000 (Material of the Kawasaki City complex safety countermeasure committee) |
| Multimedia Files |
Fig3.Chemical formula
|
| Field |
Chemicals and Plants
|
| Author |
DOBASHI, Ritsu (School of Engineering, The University of Tokyo)
TAMURA, Masamitsu (Center for Risk Management and Safety Sciences, Yokohama National University)
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