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Natech Accident
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Type
Natech Accident
Date
2011/09/17
Time
19:25
Natural Hazard
Lightning, France, 2011
Site
Feyzin Refinery, France
Status
Published

Units Involved

  1. Name
    Tank
    Type
    Storage: Atmospheric storage tank
    Description
    The fixed-roof buffer tank with a capacity of 2000 m3 was used to recover process water containing varying hydrocarbon loads from the atmospheric distillation unit.

    The tank was grounded and its roof thickness was sufficient to withstand a direct lightning strike.
  2. Name
    Flare
    Type
    Process: Stack

Event Sequences

  1. Name
    Tank explosion
    Unit
    1. Tank
    Substances Involved
    1. Name
      Process water containing hydrocarbons
      Involved Quantity
      770 m³
      Potential Quantity
      2000 m³
      Description
      The quantity involved in the accident was 770 m3. The full tank capacity was 2000 m3.
    Initiating EventCritical EventMajor Event
    Natural Hazard: Sparking
    The tank caught fire due to the lightning strike. Ignition occurred at one or more vents and the combustion spread inside the tank, eventually leading to an explosion and tank fire.
    Contributing Factors
    Equipment: Component malfunction:
    Malfunctioning of a stripper caused the presence of a hydrocarbon supernatant which in turn resulted in the formation of a hydrocarbon vapour space.
    Measure: Instrument / control / monitoring devices: Inadequate
    The tank vents were equipped with flame guards instead of flame arrestors which would have provided a higher safety level.
    Component (Non-structural): Roof damage
    Due to the explosion the tank roof tore open along the weld that connected it to the tank wall. The roof was dislodged and dangled from the shell.
    Release: Firewater runoff into water
    Small amounts of fire-fighting water and foam entered the Rhone River Canal via the refinery's stormwater drainage system.
    Contributing Factors
    Measure: Containment system (e.g. walls, dikes, enclosed room): Non-existent
    The tank did not have a retention basin which allowed fire-fighting water and foam to enter the Rhone River Canal.
    Fire: Unknown
    After ignition at the vents, the fire spread inside the tank, causing an explosion and tank fire.
    Explosion: Deflagration
  2. Name
    Flare lightning
    Unit
    2. Flare
    Description
    The flare was hit by a lightning strike. There appeared not to have been any adverse consequence.
    Initiating EventCritical EventMajor Event
    Natural Hazard: Sparking
    The flare was struck by a lightning.
    		--

Weather Conditions

Description
The lightning strikes occurred during a storm warning phase.

Emergency Response

Response Planning Activities
The refinery had an internal emergency plan.
Difficulties in Response to the Natech Event
Insufficient personnel and equipment to respond to both emergencies: No
Damage to lifelines (e.g. water, power, communication, transportation): No
Response Teams and Equipment Involved
  • On-site fire fighting team
  • On-site fire fighting trucks
Response to the Natech Event
The internal emergency plan was activated at 19:45 and several production units were placed in safe operating mode. The on-site fire fighting team put out the fire at 20:10.

Floating booms were placed in the Rhone River Canal to contain the pollution caused by the dispersion of the fire-fighting water in the canal.

Consequences

Environmental Zones Impacted
Freshwater (e.g. pond, lake, stream)
Environmental Impacts
Small amounts of water and foam from fire fighting entered the Rhone River Canal.

Remedial Activities

Remediation Activities
The day after the accident, the operator installed a buffer tank bypass circuit and secured the roof.
Restoration Activities
Following the accident, the operator verified the presence of flame arrestors at tanks operating under identical conditions. In addition, although ordinarily not storing flammable substances, the damaged tank was included in the refinery's safety report.

The site's risk analysis was updated to include a more realistic lightning risk analysis. For instance, a study was commissioned to identify the locations most at risk from lightning strikes in the plant during inclement weather conditions.

Lessons Learned

Lessons Learned on Equipment
While the tank had been properly grounded to avoid the spreading of lightning current to other parts of the installation, this safety measure was not sufficient to protect it from nearby lightning strikes.

Flame guards (a single flame retardant grating) at tank vents are not sufficient to prevent ignition due to a lightning strike. Flame arrestors should be used instead.
Lessons Learned on Organisational Aspects
Also smaller-size storage tanks which can contain small amounts of flammable substances are vulnerable to lightning strikes. Lightning risk, as well as the risk of accidental spills, should be included in the safety report of the facility.

The accident investigation highlighted that the term "flame guard" was apparently widely used in the oil industry to designate the more sophisticated "flame arrestors" that provide a higher level of protection. Terminology should be clarified to avoid confusion in the designation of complex equipment that might potentially lead to different safety levels than expected.
ID: 18, Created: Bogdan DORNEANU, 2013-08-05 15:28:34 – Last Updated: Amos NECCI, 2021-03-31 07:34:25

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