Feyzin Oil Refinery Disaster

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Feyzin Oil Refinery Disaster

• Feyzin Oil Refinery (near Lyons), France
•  
• 4th January 1966  
•  
• A large storage tank at an oil refinery holding
  liquefied propane exploded and killed a number of
  fire fighters. The incident was an important
  lesson for the hydrocarbon industries
• Thanks to
• Ann-Marie McSweeney, John Barrett Jacinta
  Sheehan Ware
• Department of Process Engineering, UCC

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Feyzin Oil Refinery Disaster

• Feyzin Oil Refinery
• A fire developed in a tank farm at an oil
  refinery. No person was in apparent danger.
• The fire service was called out  but as the fire
  had already taken hold they decided to simply
  monitor it until it safely burnt itself out.
• However the firemen appeared unaware of the
  significance of the enormous radiant heat flux
  from the fire that was impinging on adjacent
  pressurized storage tanks and spheres.
• This was raising their temperature and the
  temperature of the products within them.
• More importantly it was weakening the integrity
  (tensile strength) of the wall material (material
  tensile strength falls with higher temperature).
• When the membrane stress in the storage vessels
  due to the raised internal pressure exceeded the
  reduced tensile strength of the wall material,
  the vessels burst open.
• The contents of the vessels then ignited in a
  fireball and killed the fire fighters.

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Feyzin Oil Refinery Disaster

• Feyzin Oil Refinery
• A very good description of the incident is given
  in the book
• SAFETY LOSS PREVENTION
• AUTHOR FRANK LEES
• (In the UCC Library under Classification 660.28)
• The course notes for PE 3005 should also be
  consulted especially the material dealing with
  the temperature dependence of material strength.
  Similarly the notes of PE 2003 dealing with
  pressure vessel analysis.

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Feyzin Oil Refinery Disaster

• Refinery Storage Vessels Pressurized Spheres

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Feyzin Oil Refinery Disaster

• PRODUCT DESCRIPTION
• The material in the storage tanks was Propane
•  
• C3H8
• Third member in the saturated hydrocarbon group
  known as the alkanes. Commonly used as a fuel.

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Feyzin Oil Refinery Disaster

• Thermodynamic Properties
• Boiling Point is 42 C at Patm.
• Colourless Gas at Room Temperature and
  Atmospheric Pressure
•  
• Molecular Weight M 44
• Gas Constant R 189 J/kgK
•  
• Calorific Value 47 MJ/kg
• Flammability Limits (in air) 2.5 to 9.5
•  

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Feyzin Oil Refinery Disaster

• Thermodynamic Properties
•  
• Liquid Density 588 kg/m3 (at 1bar)
• Vapour Density 2.28 kg/m3 (at 1bar)
• It can be seen that the liquid is lighter than
  water and the vapour is heavier than air.
• Specific Heat Cp 1679 J/kgK
• Ratio of Specific Heats ? Cp/Cv 1.126
• Latent heat of evaporation ? 428 kJ/kg

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Feyzin Oil Refinery Disaster

• Vapour Pressure Curve (actually that of Propene)

From this chart, knowing the temperature of the
propane, its vapour pressure (i.e. tank internal
pressure) can be found.
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Feyzin Oil Refinery Disaster

• CONTAINMENT DESCRIPTION
• The vessel in question was a large outdoor
  spherical vessel resting on vertical legs
  designed for the bulk storage of liquefied
  propane. The vessel was amongst other similar
  storage vessels. There was a pressure relief
  valve (safety valve) at the top on a pipeline
  leading to a flare. In emergencies this valve
  would open and the escaping vapour flared off. No
  information on the diameter of the safety valve
  orifice (subsequently assume it is 100 mm).
• Vessel Geometry
• Vessel Diameter D 14 m Vessel Radius, R 7
  m
• Total Volume Vtotal 4/3pR3 1437 m3
• Ullage (i.e. free space) set at 20
• Working Volume Vworking 0.8 x 1437 1150 m3

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Feyzin Oil Refinery Disaster
Illustration of storage sphere showing vessel
supports and pressure relief system



Safety Valve



Flare





Support Legs




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Feyzin Oil Refinery Disaster

• Vessel Geometry
• Material of construction is structural steel
  with a density
• ?s 7800 kg/m3
• Wall thickness, t 45 mm
•  
•         Mass of tank wall 4pR2 t ?s 216
  tonnes
•         Surface area of tank 4pR2 616 m2
•         Projected area of tank pR2 154 m2

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Feyzin Oil Refinery Disaster

• Vessel Pressure Stress Analysis
• Tensile Strength (maximum strength) of
  structural steel
• ?TS 620 MN/m2
•  
• Rupture Pressure can be estimated from knowledge
  of the membrane stress in a spherical vessel
•  
• PR 80 bar
• Under normal conditions, the vessel would not be
  expected to rupture until the internal (propane)
  pressure reached 80 bar.
•  
• Vessel was un-insulated
• Propane temperature Ambient outside
  temperature.

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Feyzin Oil Refinery Disaster

• Vessel Pressure versus Ambient Temperature
• Storage pressure (i.e. propane vapour pressure)
  varies with ambient (i.e. propane) temperature.
•  For this location - 20 C lt TAMB lt 40 C
• Hence can tabulate the normal pressures that
  might exist within the gas storage spheres.

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Feyzin Oil Refinery Disaster

• Vessel Pressure Analysis
• Thus normal tank internal pressure is well below
  the tank failure pressure. To prevent internal
  pressure for whatever reason rising to and
  reaching the rupture pressure, the safety valve
  was set to lift (i.e. open) at 20 bar
  corresponding to a propane temperature of about
  60 C.
•  
• Thus the maximum membrane stress that could be
  developed in the tank wall would be when internal
  pressure was 20 bar.

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Feyzin Oil Refinery Disaster

• Reduction in Steel Tensile Strength with
  Temperature
• The mechanical strength of metals depends on
  their temperature as the temperature rises, the
  strength falls off. Unless otherwise stated, any
  quoted mechanical strength value is the value
  that exists at ambient temperatures.

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Feyzin Oil Refinery Disaster

• Significance of the Previous Chart
• At cold i.e. ambient temperatures, the vessel
  can contain internal pressures of up to 80 bar
  because the tensile strength ?TS 620 MN/m2
  (note it could even be higher!).
•  
• However, if the vessel wall temperature rises to
  700 C, in which case the steel tensile strength,
  ?TS falls to 150 MN/m2, then the vessel will
  rupture even with the safety valve open.
•  
• PSET 20 bar gt s 155 MN/m2
•  
• s gt sTS RUPTURE!

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Feyzin Oil Refinery Disaster

• INCIDENT DESCRIPTION
• What follows is a simplified account of what
  actually happened.
• At the date in question, there were 400 tonnes of
  propane in the tank.
•  
• Volume occupied V 680 m3
•  
• Given the working volume VW 1150 m3
•  
• Tank was approximately 60 full.
•  

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Feyzin Oil Refinery Disaster

• INCIDENT DESCRIPTION
• An adjacent hydrocarbon storage tank at the depot
  caught fire and burnt fiercely (the actual
  incident was a good deal more involved).
•  
• gt Propane storage sphere exposed to intense
  radiant heat.
• gt Temperature of propane (and steel wall) will
  rise.
• gt Vapour pressure of propane rises.
•  
• When the vapour pressure reaches relief valve
  pressure setting, PSET of 20 bar, the safety
  valve lifted and propane vapour was expelled from
  the vessel and sent to the flare.

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Feyzin Oil Refinery Disaster

• INCIDENT DESCRIPTION
• Assuming the pressure inside the vessel
  henceforth remains at 20 bar
• We have a kind of controlled equilibrium boiling
  off propane vapour at a constant pressure of 20
  bar.
• The fire fighting strategy was to let the vessel
  empty itself over time much like a kettle boiling
  itself dry at the end all that would be left
  would be a burnt out empty vessel.
• The fire fighters that had been called to the
  scene remained in proximity to the fire.

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Feyzin Oil Refinery Disaster

• INCIDENT DESCRIPTION
• What the firemen didnt know!
• The lower part of the tank wall in contact with
  the boiling liquid propane will remain at
  something close to the liquid propane temperature
  (60 C at 20 bar) due to the very high heat
  transfer coefficient (say 10,000 W/m2K) between a
  boiling liquid and metal wall.
• However the upper part of the tank wall in
  contact with the vapour receives no such cooling
  (H.T.C. of 100 W/m2K) and it will rise towards
  the of the radiant flame temperature. This would
  be an upper theoretical limit of about 1300 C.

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Feyzin Oil Refinery Disaster

• INCIDENT DESCRIPTION
•  A race is on!
• If the wall of the vessel reaches 700 C before
  the vessel has emptied itself, the wall will
  rupture and the remaining propane will go up in a
  fireball!
• Two times must be calculated
• 1 Time for upper surface of tank wall to reach
  700 ºC due to radiant heat transfer from adjacent
  fire.
• 2 How much propane will have left the sphere
  through the open safety valve in this time.

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Feyzin Oil Refinery Disaster
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Feyzin Oil Refinery Disaster

• Radiant Heat Transfer Calculation
• Early morning in January, so initial temperature
  of Propane tank Ti ? 0 C
• How long will it take for upper tank wall to
  reach 700 C?
• Do a very crude energy balance!
• Radiant heat flux QR ?.?.A.(TFlame4 TWall4)
•  Take TFlame 1300 C 1600 K
•  TWall ½(0 C 700 C) 350C 620 K
• A is the projected area of the sphere 154 m2
• Stefan-Boltzman Constant ? 5.67 x 10-8 W/m2K
• Emissivity ? (really a fudge factor), Take ?
  0.5
• QR 0.5. 5.67 x 10-8. 154 (16004 6204)
• QR 28 MW i.e. 28 MJ/s

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Feyzin Oil Refinery Disaster

• Temperature Rise in System
• Calculate the amount of thermal energy needed to
  produce the corresponding temperature rise of the
  system so that the upper wall reaches 700 ?C.
  Note the total heat in has sensible heat transfer
  and latent heat transfer components
• 1.   Bring 400 tonnes of propane from 0 C up to
  60 C.
• 2.   Bring approximately half of tank wall (108
  tonnes of steel) from 0 C up to 60 C.
• 3.    Bring other half of tank wall from 0 C up
  to 700 C.
• 4.    Evaporate off some portion (say half) of
  the propane.
•  
• Note the specific heat capacity of steel cp 450
  J/kgK

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Feyzin Oil Refinery Disaster

• Temperature Rise in System
• Q 400 x 103. 1679. (60 0) (1)
• 108 x 103. 450. (60 0) (2)
• 108 x 103. 450. (700 0) (3)
• 200 x 103. 428 x 103 (4)
•  
• Q 40 3 34 86 GJ 163 GJ
•  
• Dividing the total heat requirement by the heat
  flux to obtain time
•  
•  
• t 5821 s 97 minutes
• So, very roughly we might expect that one hour
  and a half after the outbreak of the initial
  fire, the tank wall temperature will reach 700
  C.

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Feyzin Oil Refinery Disaster

• Rate of Vessel Emptying
• How much vapour has been expelled through the
  safety valve after an hour and a half (and
  assuming the safety valve lifts soon after the
  fire starts)?
•  
• Require the mass flux through the safety valve
  model the process as isentropic expansion of an
  ideal gas across a nozzle with choked flow at
  outlet.

J Mass flow rate kg/s P Vessel pressure
bar A Valve outflow area m2 T Propane
vapour temperature (absolute) K
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Feyzin Oil Refinery Disaster

• Rate of Vessel Emptying
• P 20 bar, T 60 C 333 K
• 0.008 m2
• ? 1.126, R 189 J/kgK (Propane)
•  
• J 38.3 kg/s
•  
• Total outflow of propane in 5821 s
• J 38.3 x 5821 223 tonnes
•  
• Thus after an hour and a half, the amount of
  propane remaining in the tank is
•  
• 400 223 177 tonnes.

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Feyzin Oil Refinery Disaster

• Accident Progression
• Plotting tank wall temperature and tank internal
  pressure versus time

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Feyzin Oil Refinery Disaster

• Accident Progression
• Plotting mass of propane in vessel, wall membrane
  stress and wall tensile strength versus time.

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Feyzin Oil Refinery Disaster

• CONSEQUENCES
• An hour and a half or so after the commencement
  of the fire
•  
•         Wall temperature reached 700 C
•         Membrane stress was at 155 MN/m2
•         Steel tensile strength had fallen to 150
  MN/m2
•         Hence the Storage Sphere ruptured
•         177 tonnes of propane exploded into a
  fireball
•         17 people killed

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Feyzin Oil Refinery Disaster Disaster

• FIRE BALL (BLEVE) CALCULATIONS
• Model the instantaneous combustion of the escaped
  vapour. Duration of burning of fire ball is
• The radiative power of the fire can be calculated
  from
• QR Radiative power W
• HC Calorific Value J/kg

td Duration of fire ball s M Mass of fuel in
fire ball kg
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Feyzin Oil Refinery Disaster

• FIRE BALL (BLEVE) CALCULATIONS
• A point source model of the fire gives the
  radiative heat flux as
• ? Radiative flux W/m2
• QR Radiative power of flame W
• r Distance from source m
• In turn the thermal radiation dosage can be
  calculated as
• L Thermal radiation dosage (kW/m2)1.33s
• ? Intensity of radiation (radiation flux) kW/m2
• t Duration of exposure s

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Feyzin Oil Refinery Disaster

• FIRE BALL (BLEVE) CALCULATIONS
• Note the duration of exposure is equal to the
  duration of the fire ball.
• Damage to people exposed to the fire can be
  quantified with
• Hence can estimate how close people must have
  been to the fire to have been killed or injured.

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Feyzin Oil Refinery Disaster

• VIEW OF INCIDENT

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Feyzin Oil Refinery Disaster

• VIEW OF INCIDENT

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Feyzin Oil Refinery Disaster

• VIEW OF INCIDENT

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Feyzin Oil Refinery Disaster

• STORAGE SPHERES AFTER THE INCIDENT

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Feyzin Oil Refinery Disaster

• POSSIBLE ACCIDENT PREVENTION STRATEGIES
• 1. Install a larger pressure relief valve so if
  the tank is exposed to fire, its contents can be
  flared more rapidly.
• 2. Space the tanks further apart so that an
  outbreak of fire in one does not impose excessive
  heat radiation on adjacent units.
• 3. Place thermal insulation on tank.
• 4. Spray water over the top of tank to keep it
  cool and hence maintain its mechanical strength.
• 5. Choose a different material of construction
  for the tank specifically a heat resistant steel
  that can maintain substantial mechanical strength
  even at elevated temperatures.