| Case Name |
Leakage of fuel oil from a tank and an outflow to a canal caused due to an inadequate automatic control system |
| Pictograph |
|
| Date |
February 8, 1993 |
| Place |
Kawasaki, Kanagawa, Japan |
| Location |
Ink factory |
| Overview |
Fuel oil leaked into the sea from an ink manufacturing factory. The fuel oil circulation pump which supplied fuel to a boiler from a service tank was stopped as the boiler broke. As the power supply of a level indicator of the service tank was the same as that of a fuel oil circulation pump, the level could not be detected any more. On the other hand, the fuel supply pump (A fuel oil pump of Fig3) for the service tank was another power supply. As the pump continued supplying fuel oil, it overflowed. Irresponsible automatic control caused the accident. |
| Incident |
At an ink factory, fuel oil leaked from a vent pipe of a fuel oil tank on a roof as a result of an unsuitable automatic control system. It flowed into the canal through rainwater piping. |
| Processing |
Consumption and usage |
| Substance |
Fuel oil |
| Type of Accident |
Leakage, environmental pollution |
| Sequence |
About 08:40 on February 8th, 1993: Although each device was turned on according to the procedure, a circulation pump (not shown in Fig3) for supplying fuel oil to a boiler from a service tank did not start.
10:00: When a person in charge checked the control panel etc., he found that a magnetic switch of the circulation pump was broken.
10:30: To change the switch, a switch of the control panel was turned off. Moreover, the main power supply of the boiler was also shut off as a precaution.
13:05: The Maritime Safety Station had information that oil had spread over the sea.
13:15: The Maritime Safety Station started treating of oil. Investigation for the source of an outflow started simultaneously.
13:30: In the factory, an air passage test was performed with a device in another system under the poor condition. An employee climbed onto the roof to check the situation. He found that the liquid was flowing out from the vent pipe of the tank. Air was stopped immediately.
14:00: As the outflow was still continuing when he went up to the roof again, all oil pumps were stopped.
14:30: Absorbent was thrown into the catch basin and residual oil was gathered.
15:50: The public fire department crew arrived at the factory. At the time, recovery of residual oil had been completed and the oil film spread on the sea surface was removed.
The amount of leakage was about 2500 L. About 1600 L leaked to the sea. |
| Cause |
The power supply system of pumps and that of a control alarm system that were related to each other were irrational. When a magnetic switch of the fuel oil circulation pump of the boiler was changed, the main power supply was shut off, and a level control system of the fuel oil tank (service tank of Fig3) was turned off, and a level sensor of the tank stopped working. However, power supply of the supply pump (A fuel oil pump in Fig3) of the underground tank to the fuel oil tank was still on. As a self-holding circuit of an instrument board was operating, the pump continued to supply fuel oil to the tank. Finally, fuel oil leaked from the vent pipe.
A subcontractor had not taken the level control system into consideration at the time of starting the factory.
That is, a transmitter circuit of the operation signal was built into a custom-made control panel instead of the control panel of the plant.
When an employee shut off the main power supply, he did not know that the underground tank pump, an electromagnetic valve, and an alarm etc.
could not be controlled. |
| Response |
The Maritime Safety Station treated oil spill. Absorbent was thrown into the catch basin and a new outflow was prevented. Residual oil was gathered. |
| Countermeasures |
The automatic operation system should be changed so that the oil supply pump would stop and the electromagnetic valve would close when the boiler main power supply is shut off.
The operation circuit should be changed so that the fuel oil supply would restart after the fuel oil low level alarm operated when the boiler main power supply is switched on.
The discharge pressure of the pump should be lowered so that the oil can not leak physically.
Overflow piping from a roof tank to an underground tank is installed.
Refer to Fig2. |
| Knowledge Comment |
If a fail-safe system of the automatic control system is insufficient, it is very difficult to treat the automatic control system because the safety of the plant depends on the function of the system and the system is not operated usually.
An alarm system is an example of automatic control systems. Even if a control system has stopped, the alarm must be able to operate. The power supply of an alarm system therefore should be independent of a control system. |
| Background |
Safety facilities were installed by a sub-contractor, and the operating company did not consider the system. Maintaining safety of a plant is a duty of the operating company. Even if it entrusts the design of an instrumentation system to a sub-contractor, for safety preservation, the operating company itself should take responsibility.
The second factor was that the company had not educated the employees, or that the employees had not studied the instrumentation system of the plant they operated. |
| Incidental Discussion |
Discussion on failure of the instrumentation system might not have been held. In this case, when overflow return piping from a service tank to the fuel main tank was installed, the problem did not occur. Return piping is installed even in the water supply tub of an apartment. |
| Reason for Adding to DB |
Example of leakage and an outflow to a canal caused due to inadequate design of a power supply system of instrumentation |
| Scenario |
| Primary Scenario
|
Insufficient Analysis or Research, Insufficient Practice, Lack of Imagination, Poor Value Perception, Poor Safety Awareness, Inadequate Risk Recognition, Planning and Design, Poor Planning, Poor Design, Malfunction, Poor System, Poor Operation System, Secondary Damage, External Damage, Leakage, Secondary Damage, Damage to Environment, Sea Pollution
|
|
| Sources |
High Pressure Gas Safety Inst. of Japan, High-pressure gas protection overview, pp.260-261 (1995).
Kawasaki City Fire fighting station, Prevention division, Peace section, Fuel oil leakage accident at dangerous material manufacturer N ink Co., Ltd. T factory. Material of Kawasaki City Complex safety countermeasure committee.
Ministry of Health, Labor and Welfare, Outline of major accident. The safe and health yearbook.
|
| Financial Cost |
¥ 75,000. (Material of the Kawasaki City Complex safety countermeasure committee). |
| Consequences |
About 1600 L leakage into a canal. |
| Multimedia Files |
Fig2.Service tank level control system diagram
|
| Notes |
Although the kinds of oil differed, the same company caused almost the same accident before. |
| Field |
Chemicals and Plants
|
| Author |
ITAGAKI, Haruhiko (Japan National Institute of Occupational Safety and Health)
TAMURA, Masamitsu (Center for Risk Management and Safety Sciences, Yokohama National University)
|
