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Natech Accident
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Type
Natech Accident
Date
2011/03/11
Time
14:46
Duration
235 hour(s)
Natural Hazard
Tōhoku Earthquake, Japan, 2011
Site
Cosmo Oil Refinery, Japan
Status
Published

Units Involved

  1. Name
    LPG storage tank 364
    Type
    Storage: Pressurized storage tank
    Description
    LPG tank No. 364 was one of a total of 17 LPG spheres in Cosmo Oil refinery's LPG storage area. At the time of the earthquake the tank was under regulatory inspection and was filled with water, instead of LPG, in order to remove air from inside the tank.
  2. Name
    LPG storage tank farm
    Type
    Storage: Pressurized storage tank
    Description
    The LPG storage tank farm consisted of 17 LPG tanks.
  3. Name
    Asphalt tanks
    Type
    Storage: Atmospheric storage tank
    Description
    The asphalt tanks were located adjacent to the LPG storage area.

Event Sequences

  1. Name
    ES1 (Collapse of LPG storage tank)
    Unit
    1. LPG storage tank 364
    Description
    The main earthquake shock at 14:47 caused several of the diagonal braces that were supporting the tank legs to fracture. During the after shock at 15:15, some legs holding up the tank bent and the tank collapsed, severing LPG pipes and resulting in LPG leakage.

    While the tank in question met all earthquake design requirements for the area assuming LPG filling, at the time of the earthquake it contained water due to an inspection. With water being 1.8 times heavier than LPG the tank braces and legs could not withstand the additional loading due to the earthquake forces. This situation had not been considered in the earthquake design requirements.
    Contributing Factors
    Organisational: Testing / inspecting / recording: Unclear
    It is good practise during LPG tank inspections to leave the water for not more than 2-3 days in the tank. At the time of the earthquake the tank that collapsed had been filled with water for 12 days.
    Initiating EventCritical EventMajor Event
    Component (Structural): Collapse of support columns
    The earthquake shock caused the tank braces to fracture and eventually the legs to buckle. During the main earthquake shock at 14:47, the measured PGA was 0.12 g (114 gal, Ichihara City). At 15:15, the aftershock PGA was 0.10 g (99 gal, Ichihara City).
    Component (Structural): Complete collapse
    		-
    Event Sequence: ES2 (Fire and explosions)
  2. Name
    ES2 (Fire and explosions)
    Unit
    2. LPG storage tank farm
    Description
    The LPG leaking out from the ruptured pipes spread out and caught fire. As a consequence, the tank adjacent to Tank 364 exploded (BLEVE), spreading the fire from tank to tank and eventually throughout the whole LPG tank farm, leading to several explosions.
    Substances Involved
    1. Name
      Liquefied Petroleum Gas
      Involved Quantity
      5227 ton
    Initiating EventCritical EventMajor Event
    Event Sequence: ES1 (Collapse of LPG storage tank)
    Component (Non-structural): Pipe break / damage
    Contributing Factors
    Measure: Emergency shut off / safety valves: Unavailable
    Human: Failure to carry out duties: Non-existent
    Prior to the earthquake an emergency valve on the LPG pipes had been manually locked "open" to prevent it from actuating due to minor air leakages during repair work. Once LPG started to be released from the damaged pipe and the fire ignited, the valve could not be reached and closed, thereby continuously providing LPG to feed the fire. This exacerbated the fire and made it burn out of control. By manually overriding the emergency valve, the company was in violation of the High-Pressure-Gas law. In a personal communication, the Chiba Prefecture Fire Department expressed its belief that the accident might have been manageable had the safety valve not been open.
    Release: Gas, vapour, mist, or smoke release to air
    Explosion: Vapour cloud explosion
    The shock waves and debris from the explosions triggered fires in the adjacent premises of Maruzen Petrochemical Co., Ltd., and Chisso Petrochemical Corporation.
    Explosion: BLEVE
    Event Sequence: ES3 (Asphalt release)
    Fire: Jet fire
  3. Name
    ES3 (Asphalt release)
    Unit
    3. Asphalt tanks
    Description
    Asphalt tanks adjacent to the affected LPG storage tank area were damaged and
    asphalt leaked out of the tanks.
    Substances Involved
    1. Name
      Asphalt
      CAS No
      8052-42-4
    Initiating EventCritical EventMajor Event
    Event Sequence: ES2 (Fire and explosions)
    The damage to the asphalt tanks occurred due to debris impact from the exploding LPG tanks.
    Release: Solid release to ground
    Release: Solid release to water
    Dispersion: Substance in / on water
    Asphalt reached the sea.

Emergency Response

Response Planning
Emergency response plan is sufficient in taking Natech events into consideration: No
Response Planning Activities
The facility/response teams were not prepared for an accident of this magnitude.
Difficulties in Response to the Natural Hazard
Insufficient personnel and equipment to respond to both emergencies: Yes
Natech event prevents efficient operation of personnel in the natural hazard affected area: Yes
Response Teams and Equipment Involved
  • On-site systems (e.g. sprinkler, water cannon)
  • On-site fire fighting team
  • Local fire fighting team
  • Fire fighting teams of nearby plants
  • Regional / national fire fighting teams
Sheltering and Evacuation due to the Natech event
  • On-site evacuation
  • Off-site evacuation
Response to the Natech Event
Due to the fires and explosions 1142 residents had to be evacuated. The fire-fighting teams worked from both land and sea, however, due to the many release sources it was decided to let the tanks burn until the LPG was exhausted.

Consequences

On-site Injured
6
Human Health Impacts
1 severe and 5 minor injuries.
Environmental Impacts
There is very little information on environmental impact of the event, although some asphalt seems to have entered the sea. However, Cosmo Oil indicated that all asphalt was successfully recovered. They also highlight that there is no lasting impact on air, water or soil from the accident.
Economic Impacts
The explosions caused damage to nearby vehicles and ships. The shock waves also caused broken windows and damaged shutters and roof shingles in nearby residential areas.
Built-up Areas Impacted
  • Industrial areas (e.g. factories)
  • Residential areas (e.g. housings, hotels)
  • Infrastructure (e.g. roads, railways, air transport)

Lessons Learned

Lessons Learned on Equipment
As a preventive measure, LPG tanks will be surrounded by flexible pipelines to prevent damage should a tank collapse on the pipelines.
Lessons Learned on Organisational Aspects
- Locking the safety valve in the open position was in violation of safety regulations and exacerbated the accident. Cosmo Oil has eliminated the practice of locking emergency shutoff valves in an open position.
- In the future, the period during which a tank will be filled with water due to inspections, will be minimised.
- There will be safety inspections to ensure that all personnel are aware of applicable laws and regulations regarding the safety of the facility and its processes.
- Emergency drills will be executed to improve preparedness for large-scale disasters.
ID: 14, Created: Elisabeth KRAUSMANN, 2013-07-17 15:06:37 – Last Updated: Kyriaki GKOKTSI, 2024-03-26 10:03:46

Attachments

NoDescriptionFile Size
1.Cosmo Oil Press Release 02/08/2011 280.30KB
2.Incident Summary Report by the Japan High Pressure Gas Safety Institute (in Japanese) 627.36KB
3.Krausmann, Cruz, 2013 700.65KB
4.Photo Status 31 March 2011 128.74KB
5.Wada, Wakakura 2011 1.11MB
Last update: 2024/04/17 | Top