| Case Name |
Fire during receiving gasoline at an inner floating roof tank |
| Pictograph |
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| Date |
November 23, 2002 |
| Place |
Yokohama, Kanagawa, Japan |
| Location |
Oil terminal |
| Overview |
A fire occurred at an inner floating gasoline tank during receiving operation from a tanker, and the fire spread to become a full-face fire. The cause could not be specified. Two possibilities were indicated. 1) Remained pressurized air in the piping was discharged into the tank, and part of the floating roof and the tank wall made strong contact with each other. 2) Parts that had corroded fell away due to vibrations at the receiving part, and sparks were generated by metal-to-metal friction caused by parts falling away. It was considered that sparks ignited the gasoline liquid surface, which was generated by a damaged seal of the floating roof. The fire spread from the inner floating structure. Although there is no direct suggestion, management of facilities seems to have been imperfect. |
| Incident |
At a 2000 kL gasoline tank of the inner floating type, a fire occurred on receiving gasoline from a tanker. There was no spread of fire to nearby tanks.
Inner float type tank: a kind of floating roof type tank. The tank is installed with a floating roof inside a fixed roof tank (for example, a cone roof type tank). Ventilation is often considered so that combustible gas should not accumulate in the space between a fixed roof and a floating roof. There are examples of remodeling to an inner float type tank from a fixed roof type tank when hydrocarbon emission prevention measures are executed or storage oil is changed to gasoline. |
| Processing |
Storage |
| Substance |
Gasoline |
| Type of Accident |
Fire |
| Sequence |
The progress during the day of the accident;
On November 23rd, 2002
01:13, shipping for the previous day had ended, and current storage quantity of the tank was measured.
11:03, receiving from the tanker started. The flow rate was very low at first and gradually increased after confirming that the inner floating roof had started to float.
11:06, a fire occurred at the tank suddenly.
11:08, "Stopping all work in the yard" was directed.
History of the tank
In March, 1964, the tank was constructed as a cone roof type kerosene tank
In September, 1987, it was remodeled to the inner float type and the oil type was changed to gasoline
In August, 1997, an inside overhaul inspection and main body repair were carried out. |
| Cause |
Although the fact that specified the cause was not obtained, it is strongly thought that the fire might have been generated by sparks caused by friction of metal against metal. The following two causes of metal friction are considered.
1. Contact between a tank wall and a floating roof.
On starting to receive gasoline, pressurized air that remained in the piping after the previous receiving operation spouted out as bubbles. The bubbles floated, and the roof vibrated strongly, and part of the floating roof, especially a protrusion, made strong contact with the tank wall. The gasoline that had been exposed by degradation of the seal of the roof caught fire due to sparks generated.
2. Due to vibration of the tank on beginning to receive and/or singing of the tank caused by wind, a corroded fixed bolt of the tank came off and dropped. As a result, a beam fell, and it collided with the tank wall, supports, and the floating roof etc. Then, sparks ignited a combustible gas mixture generated by the receiving operation and the gasoline exposed by degradation of the seal of the floating roof caught fire.
The reason why the flame spread rapidly to damage the entire tank was thought to be as follows. While the fire in the floating roof made of aluminum advanced, the flames spread, and the gas in the space between the floating roof and the fixed roof expanded rapidly. Therefore, the tank internal pressure rose, and the tank swelled, while gas rapidly spouted from openings such as a bleeder, and the tank was deformed. The roof weld line of the fixed roof that could not withstand the pressure broke, and an opening was made. Simultaneously, it shifted to a fire in the entire tank, because the roof beams fell, and the deck skin of the roof was destroyed. |
| Response |
Receiving was stopped. Block valves were closed in all tanks. Fire extinguishing activities were carried out by the public fire brigade. |
| Countermeasures |
The countermeasures for the two possible causes are given below. They are not countermeasures for this accident, but general countermeasures.
1. For cargo handling (receiving). (Refer to "On the side").
(1) Decrease of air in the piping at the end of cargo handling.
(2) Attention to the receiving flow rate for air remaining in the piping at the start of handling.
2. The structure inside the floating roof.
(1) Strengthening equipment for preventing rotation of the floating roof.
(2) Ensuring that a sharp protrusion does not exist at the outer part of the floating roof where there might be contact with the side wall during assembling the floating roof.
3. Considerations for an inspection.
3-1. Turnaround checks.
(1) Confirmation of the floating roof seal.
(2) Checking dangerous materials of the floating roof.
(3) The situation of rotation-preventing cables.
3-2. Overhauls. (Once in 10 years).
(1) The situation of fixing bolts for the roof beam.
(2) The eccentricity of the tank. |
| Knowledge Comment |
1. When a fire is generated in an inner floating tank, it can lead structurally to a conflagration.
2. The key in accident prevention is that there should be clear inspection points at a turnaround shutdown inspection and a routine inspection. |
| Background |
Accident causes seem to indicate problems with management. One is degradation of the seal of the floating roof, and the other is corrosion of the bolt. These are maintenance problems. |
| Incidental Discussion |
A liquid is sent in by pump cargo handling from the tanker as much as possible. Therefore, it flows in until air is drawn into the pump. The pumps used are mainly gear pumps. Therefore, air remains in the tank receiving piping even if the receiving method was not an air pressurizing system. On receiving, it is difficult to control the volume, because it is generally done at the ship's side. It is considered that most of the air can be removed if a vapor trap is established for the receiving piping. Actually, it is not certain to what extent this is effective. If it is effective, it should be installed. |
| Reason for Adding to DB |
Fire of an inner floating roof tank structurally having the property to expand the fire |
| Scenario |
| Primary Scenario
|
Poor Value Perception, Poor Safety Awareness, Inadequate Risk Recognition, Organizational Problems, Poor Management, Slackness of Management, Carelessness, Insufficient Precaution, Overlooking Unsuitable Position, Malicious Act, Rule Violation, Insufficient Inspection, Regular Movement, Careless Movement, Too High Velocity, Bad Event, Mechanical Event, Friction/Impact, Bad Event, Chemical Phenomenon, Heat Generation/Ignition, Secondary Damage, External Damage, Fire, Loss to Organization, Economic Loss, Direct Manetary Damage 150 million yen
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| Sources |
Fire fighting station of Yokohama City. Kazutomo Hamaoka, Tank fire at D Co. Y oil terminal. Safety & Tomorrow, No.88, pp.40-44 (2003).
Fire fighting station of Yokohama City. Kazutomo Hamaoka, D Co. Y oil terminal, an outline of tank fire and safety countermeasures No.21. Industry and Security, Vol.19, No.24, pp.14-17 (2003)
Fire and Disaster Management Agency, Outline of accidents of dangerous materials during 2002. p.26 (2003).
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| Physical Damage |
A gasoline storage tank burned. About 25 kiloliters of high-octane gasoline burned. |
| Financial Cost |
¥ 153 million. (Fire and Disaster Management Agency) |
| Multimedia Files |
Fig2.Situation of damage
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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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