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
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.
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.
Feyzin Oil Refinery Disaster
Refinery Storage Vessels – Pressurized Spheres
Feyzin Oil Refinery Disaster
PRODUCT DESCRIPTION
The material in the storage tanks was Propane
C3H8
H
H
H
H
C
C
C
H
H
H
H
Third member in the saturated hydrocarbon group known as the alkanes.
Commonly used as a fuel.
Feyzin Oil Refinery Disaster
Thermodynamic Properties
Boiling Point is – 42 °C at Patm.
Colourless Gas at Room Temperature and Atmospheric Pressure
Molecular WeightM = 44
Gas Constant
R = 189 J/kgK
Calorific Value = 47 MJ/kg
Flammability Limits (in air) 2.5 % to 9.5 %
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
Ratio of Specific Heats
Latent heat of evaporation
Cp= 1679 J/kgK
 = Cp/Cv = 1.126
 = 428 kJ/kg
Feyzin Oil Refinery Disaster
Vapour Pressure Curve
(actually that of Propene)
Vapour Pressure Curve
Pv (bar)
15
Liquid
10
Vapour
5
T °C
-50
0
50
From this chart, knowing the temperature of the propane, its vapour pressure
(i.e. tank internal pressure) can be found.
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
Total Volume
Vtotal = 4/3πR3
Vessel Radius, R = 7 m
=
1437 m3
Ullage (i.e. free space) set at 20 %
Working Volume Vworking = 0.8 x 1437
= 1150 m3
Feyzin Oil Refinery Disaster
Illustration of storage sphere showing vessel supports and
pressure relief system
Safety Valve
Flare
Support Legs
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 =
Surface area of tank =
Projected area of tank =
4πR2 t s
4πR2
πR2
= 216 tonnes
= 616 m2
= 154 m2
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
4 t  TS 4 x 0.045 x 620 x10 6
PR 

D
14
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.
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 < TAMB < 40 °C
Hence can tabulate the normal pressures that might exist within the gas
storage spheres.
TAMB (°C)
PV (BAR)
- 20
4
0
7
20
9.5
40
13
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.
PD 20 x105 x 14


 155 MN / m2
4t
4 x 0.045
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.
TS
700
600
MN/m2
500
400
300
200
100
0
200
400
600
800
T
°C
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
σ > σTS
=> σ = 155 MN/m2
RUPTURE!
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
400 x10 3
V 

588
m
Given the working volume VW = 1150 m3
Tank was approximately 60 % full.
V = 680 m3
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).
=> Propane storage sphere exposed to intense radiant heat.
=> Temperature of propane (and steel wall) will rise.
=> 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.
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.
Feyzin Oil Refinery Disaster
INCIDENT DESCRIPTION
What the firemen didn’t 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.
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.
Feyzin Oil Refinery Disaster
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) = 350°C = 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
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:
Q  m c p T  J 
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
Feyzin Oil Refinery Disaster
Temperature Rise in System
Q = 400 x 103. 1679. (60 – 0)
+ 108 x 103. 450. (60 – 0)
+ 108 x 103. 450. (700 – 0)
+ 200 x 103. 428 x 103
Q = 40 + 3 + 34 + 86 GJ
(1)
(2)
(3)
(4)
= 163 GJ
Dividing the total heat requirement by the heat flux to obtain time
Q 163 x109
t

QR 28 x10 6
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.
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
J
P
A
T
P A    1  2   1


2    1
T R
Mass flow rate
Vessel pressure
Valve outflow area
Propane vapour temperature (absolute)
kg/s
bar
m2
K
Feyzin Oil Refinery Disaster
Rate of Vessel Emptying
P = 20 bar,
A

4
0.12 
 = 1.126,
T = 60 °C = 333 K
0.008 m2
R = 189 J/kgK
20 x105 0.008
J
0.048
18.25
(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.
Feyzin Oil Refinery Disaster
Accident Progression
Pressure - bar
Temperature - °C
Plotting tank wall temperature and tank internal pressure versus time
700
600
Tank upper wall
100
Tank lower wall (and propane)
0
10
20
30
40
50
60
70
80
90
0
10
20
30
40
50
60
70
80
90
Time (min)
20
10
Time (min)
Feyzin Oil Refinery Disaster
Accident Progression
Mass of Propane - tonnes
Plotting mass of propane in vessel, wall membrane stress and wall
tensile strength versus time.
400
300
200
100
0
10
20
30
40
50
60
70
80
90
Time (min)
Stress - MPa
700
600
Steel tensile strength
200
Membrane stress in wall
Fracture
100
0
10
20
30
40
50
60
70
80
90
Time (min)
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
Feyzin Oil Refinery Disaster Disaster
FIRE BALL (BLEVE) CALCULATIONS
Model the instantaneous combustion of the escaped vapour. Duration of burning
of fire ball is
t d  0.46 M 0.333
td
M
Duration of fire ball
Mass of fuel in fire ball
s
kg
The radiative power of the fire can be calculated from
M HC
QR  0.3
td
QR
HC
Radiative power
Calorific Value
W
J/kg
4
L  3 t
Feyzin Oil Refinery Disaster
FIRE BALL (BLEVE) CALCULATIONS
A point source model of the fire gives the radiative heat flux as


QR
r
QR
4 r 2
Radiative flux
Radiative power of flame
Distance from source
W/m2
W
m
In turn the thermal radiation dosage can be calculated as
4
L  3 t
L

t
Thermal radiation dosage
Intensity of radiation (radiation flux)
Duration of exposure
(kW/m2)1.33s
kW/m2
s
4
L  3 t
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
Dosage, L
(kW/m2)1.33s
90
100
1000
1200
2100
2500
6500
Severity of Burns
-
Fatalities
-
Pain Threshold
First Degree
1%
Second Degree
50 %
Third Degree
99 %
Hence can estimate how close people must have been to the fire to have
been killed or injured.
Feyzin Oil Refinery Disaster
VIEW OF INCIDENT
Feyzin Oil Refinery Disaster
VIEW OF INCIDENT
Feyzin Oil Refinery Disaster
VIEW OF INCIDENT
Feyzin Oil Refinery Disaster
STORAGE SPHERES AFTER THE INCIDENT
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.