434 15

Risk Assessment Data Directory
Report No. 434 – 15
March 2010
I n t e r n a t i o n a l A s s o c i a t i o n o f O i l & G a s P r o d u c e r s
Vulnerability
of plant/structure

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RADD – Vulnerability of plant/structure
©OGP
contents
1.0 Scope and Definitions ........................................................... 1
1.1 Application ......................................................................................................1
1.2 Definitions .......................................................................................................1
2.0 Summary of Recommended Data ............................................ 1
2.1 Fire ...................................................................................................................2
2.1.1 Vulnerability of Plant/Structure under Fire Loading............................................... 2
2.1.2 Derivation of Fire Loads ............................................................................................ 4
2.2 Explosions.......................................................................................................7
2.2.1 Vulnerability of Plant/Structure to Explosions........................................................ 7
2.2.2 Overpressure Loading............................................................................................. 10
2.2.3 Drag Loading on Equipment ................................................................................... 11
2.2.4 Response of Plant/Structure................................................................................... 12
2.3 Missiles..........................................................................................................14
3.0 Guidance on use of data ...................................................... 17
3.1 General validity .............................................................................................17
3.2 Uncertainties .................................................................................................17
4.0 Review of data sources ....................................................... 17
5.0 Recommended data sources for further information ............ 18
6.0 References .......................................................................... 19
6.1 References for Sections 2.0 to 4.0 ..............................................................19
6.2 References for other data sources examined............................................19

©OGP
Abbreviations:
2D Two-dimensional
AIChE American Institute of Chemical Engineers
API American Petroleum Institution
BLEVE Boiling Liquid Expanding Vapour Explosion
BS British Standard
CCPS Center for Chemical Process Safety
CoP Code of Practice
DLM Direct Load Measurement
DNV Det Norske Veritas
ESREL European Safety and Reliability
FPSO Floating Production, Storage and Offloading unit
HSE (UK) Health and Safety Executive
ISO International Organization for Standardization
LPG Liquefied Petroleum Gas
LPGA LP Gas Association
MDOF Multiple Degree of Freedom
QRA Quantitative Risk Assessment
SDOF Single Degree Of Freedom
UKOOA United Kingdom Offshore Operators Association (now Oil & Gas UK)

©OGP 1
1.0 Scope and Definitions
1.1 Application
This datasheet provides information on vulnerability of plant/structure to the
consequences of major hazard events on onshore and offshore installations. The focus
is on primary structures (e.g. primary beams/columns, firewalls, control rooms etc.) and
major items of equipment such as pressure vessels where failure can lead to escalation
effects. Information is presented relating to the structural response failure criteria. The
following consequences are considered:
• Fire
• Explosion
• Missile
For the purposes of a QRA the information provided in this datasheet may be sufficient
and, where applicable, acceptable to the regulatory authority. However, where the risks
arising from structural failure are significant, more detailed analysis of the vulnerability
of plant/structure to heat, overpressure and impact loads may be required. This should
be carried out by specialists within those fields as it requires both a sound
understanding of the underlying physics and the use of complex numerical simulations.
Such assessments would, typically, require a multi-disciplinary approach involving
safety, process and structural engineering disciplines amongst others.
It should also be stressed the vulnerability of plant/structure can be significantly
reduced by employing the principles of inherent safety. For example, application of
good local and global layout methods can reduce not only the likelihood and the
severity of fires and explosions but also the likelihood of escalation of the event and the
overall consequences.
1.2 Definitions
• Emissivity A constant used to quantify the radiation emission characteristics
of a flame: it is the fraction of the maximum theoretical radiative
flux (that of a “perfect black body”) emitted by the flame.
• Convective Flux Refers to the transfer of heat from one point to another
within a fluid, gas or liquid, by the mixing of one portion of the fluid
with another.
• Impulse The integral of a force or load over an interval of time.
• Radiative Flux Refers to the transfer of heat from one body to another by thermal
radiation.
• Rise Time The time taken for the explosion overpressure to increase from
zero to the peak overpressure.
2.0 Summary of Recommended Data
The data presented in this section are set out as follows:
• Section 2.1: Response to Fires
• Section 2.2: Response to Explosions
• Section 2.3: Impact of Missiles

©OGP2
2.1 Fire
Section 2.1.1 gives typical data for vulnerability of plant/structure under fire loading.
Characteristic data for typical hydrocarbon fires are given in Section 2.1.2.
2.1.1 Vulnerability of Plant/Structure under Fire Loading
Table 2.1 gives typical times to failure of various items of plant/structure. Critical
temperatures for failure of various components and vessels are shown in Table 2.2.
Table 2.1 Time to Failure of Pipework, Vessels, Equipment and Structures
affected by Fire [1]
Fire Scenario (Note 1) Failure Time to Failure (Note 2)
Flame with heat flux of
250 kW/m2
impinging onto
a pipe support with no fire
protection.
Excessive deformation of
pipe supports leading to
loss of tightness and
potential rupture.
< 5 min
250 kW/m2
impinging onto
a connector or flange
(clamp or bolted) with no
fire protection.
Hub connector or flange
(clamp or bolted), loss of
tightness.
< 5 min
250 kW/m2
impinging onto
a valve with no fire
protection.
Valve, loss of tightness. < 10 min
250 kW/m2
impinging onto
a safety valve with no fire
protection.
Safety valve, opens at a
pressure lower than the
setting pressure.
< 10 min
250 kW/m2
impinging onto
a bursting disc device with
no fire protection.
Bursting disc, opens at a
pressure lower than the
setting pressure or is
destroyed.
< 10 min
250 kW/m2
impinging onto
pressure vessel with no
fire protection.
Pressure vessel rupture
with the potential formation
of projectiles.
< 40 min depending on the
flame size with respect to
vessel size, vessel
contents, wall thickness
and the size of pressure
relief/blowdown orifice.
Determine the time to
failure by multi-physics
analysis.

©OGP 3
Fire Scenario (Note 1) Failure Time to Failure (Note 2)
250 kW/m2
impinging onto
a pipe attached to a
pressure vessel. The pipe
is unprotected and the
vessel is protected so that
heat is conducted by the
pipe into the pressure
vessel shell forming a hot
spot with loss of strength.
Pressure vessel rupture
with the potential formation
of projectiles.
size of the pipe and fire
intensity.
250 kW/m2
impinging onto
a vessel support with no
fire protection.
Excessive deformation of
vessel supports leading to
loss of tightness at nozzle
flanges.
< 5 min
250 kW/m2
impinging
locally onto a structural
member with no fire
protection.
Loss of load bearing
capacity of a structural
member, which may lead to
large deformation in some
locations and loss of
tightness of pipework.
member size
250 kW/m2
impinging
locally onto a joint of
structural members or
engulfing several joints.
Collapse of structure or its
part leading to loss of
tightness of pipework and
large releases of hazardous
fluids.
member sizes.
250 kW/m2
impinging onto
the storage or transport
tanks with no fire
protection.
Collapse of atmospheric
storage tanks, road tankers,
rail tank cars and marine
tankers leading to large
releases of hazardous
fluids.
flame size with respect to
tank size and the tank
contents, fill level, wall
thickness and the size of
any pressure relief device.
Determine the time to
failure by multi-physics
analysis.
Notes
1. The time to failure for heat fluxes other than 250 kW/m
2
should ideally be determined by
transient calculations.
2. The times to failure given are upper limits, as per the original source reference. Judgment
should be used to select a suitable minimum or other absolute value if required.

©OGP4
Table 2.2 Commonly used critical temperatures [2]
Exposed Structure Temperature
(°C)
Structural steel onshore 550-620
LPG tanks (France and Italy) 427
Structural steel offshore 400
LPG tanks (UK and Germany) 300
Structural aluminium offshore 200
Unexposed face of a division/boundary 180
Unexposed face of a division/boundary 140
Surface of safety related control panel 40
Note that these values are indicative only and, if the risks from structural failure due to
fire are significant, more detailed analysis may be required in order to determine the
thermal response of plant/structure. Generally for simple linear elements, all that is
required is the temperature distribution across the section at the mid point. This may be
computed using 2D thermal analysis. For more complex elements and whole structures,
typically the complete temperature history of all parts of the structure is required
although some simplification may be possible.
In particular, the material behaviour under elevated temperatures i.e. temperatures
above ambient, should be accounted for. The effects of elevated temperatures when the
structure is considered to be stress-free are threefold:
• reduction of modulus of elasticity and hence changes in stiffness
• reduction in yield strength of structural steel and
• thermal strains.
Data for the behaviour of various grades of steel under elevated temperatures is given
in [3].
2.1.2 Derivation of Fire Loads
The assessment of the vulnerability of plant/structure to fires requires that the following
be established:
a) The fire scenario or design fire
b) Heat flow characteristics from the fire to the plant/structure
c) The behaviour of material properties of the plant/structure at elevated temperatures
d) The properties of fire protection systems.
The actual fire scenarios and design fluxes must first be defined. Design fires are
usually characterised in terms of the following variables with respect to time [4]:
• heat release rate
• toxic-species production rate
• smoke production rate
• fire size (including flame length)

©OGP 5
• duration.
Other variables such as temperature, emissivity and location may be required for
particular types of numerical analysis. Generally, the following should be considered in
the determination of fire loads:
a) whether the fire is a pool or jet fire and confined/unconfined
b) whether fire is ventilation or fuel controlled
c) whether flame is obstructed/unobstructed
d) composition of fire fuel (one-phase or two-phase)
e) gas to oil ratio in the burning fluid
f) temporal and spatial variation of heat flux within a flame.
[2] and [5] include details of a wide range of pool and jet fires that enable the radiative
and convective heat transfer to be calculated more accurately than in the past for a wide
range of fire scenarios. These are presented in Table 2.3 to Table 2.7 below for high
pressure gas jet fires, high pressure two-phase jet fires, pool fires on installation, pool
fires on sea and fire loading on pressure vessels respectively.
Table 2.3 Characteristic Data for High Pressure Gas Jet Fires [2]
Size (kg/s) 0.1 1 10 >30
Flame Length (m) 5 15 40 65
Radiative flux (kW/m2
) 80 130 180 230
Convective flux
(kW/m2
)
100 120 120 120
Total heat flux (kW/m2
) 180 250 300 350
Flame emissivity 0.25 0.4 0.55 0.7
Table 2.4 Characteristic Data for High Pressure Two-Phase Jet Fires [2]
Fuel mix of 30% gas, 70% liquid
by mass
Flashing Liquid
fires (e.g.
propane/butane)
Size (kg/s) 0.1 1 10 >30 1
Flame Length (m) 5 13 35 60 not given in [2]
Radiative flux
(kW/m2
)
100 180 230 280 160
Convective flux
(kW/m2
)
100 120 120 120 70
Total heat flux
(kW/m2
)
200 300 350 400 230
Flame emissivity 0.3 0.55 0.7 0.85 1

©OGP6
Table 2.5 Characteristic Data for Pool Fires on Installations [2]
Methanol Pool Small
Hydrocarbon
Pool
Large
Hydrocarbon
Pool
Typical Pool Diameter (m) 5 <5 >5
Flame Length (m) Equal to pool
diameter
Twice pool
diameter
Up to twice pool
diameter
Mass burning rate
(kg/(m2
s))
0.03 Crude: 0.045 -
0.06 Diesel: 0.055
Kerosene: 0.06
Condensate: 0.09
C3/C4s: 0.09
Crude: 0.045 -
0.06 Diesel: 0.055
Kerosene: 0.06
Condensate: 0.10
C3/C4s: 0.12
) 35 125 230
Convective flux (kW/m2
) 0 0 20
) 35 125 250
Flame emissivity 0.25 0.9 0.9
Table 2.6 Characteristic Data for Pool Fires on Sea [2]
Typical Pool Diameter > 10
Flame Length (m) Up to twice
diameter
Mass burning rate (kg/(m2
s)) Crude: 0.045 - 0.06
Diesel: 0.055
Kerosene: 0.06
Condensate: 0.10
C3/C4s: 0.20
) 230
Convective flux (kW/m2
) 20
) 250
Flame emissivity 0.9
Table 2.7 Characteristic Fire Loading for Pressure Vessels and Other
Equipment [5]
Jet Fire
0.1 kg/s < leak
rate < 2 kg/s
leak rate > 2 kg/s
Pool Fire
Local Peak Heat Load (kW/m2
) 250 350 150
Global Average Heat Load
(kW/m2
)
0 100 100
The global average heat load represents the average heat load that exposes a
significant part of the process segment or structure and provides the major part of the
heat input to the process segment thereby affecting the pressure in the segment.

©OGP 7
The local heat load exposes a small area of the process segment or structure to the
peak heat flux. The local peak heat load, with the highest flux, determines the rupture
temperature of different equipment and piping within the process segment.
2.2 Explosions
The loading on plant/structure from an explosion arises from both overpressure loading
and drag loading. The input data required for the assessment of the vulnerability of
plant/structure include:
• Peak pressure
• Impulse
• Load duration
• Rise time (to peak pressure)
• Drag pressure
• Approximate impulse duration for dynamic drag
2.2.1 Vulnerability of Plant/Structure to Explosions
Survey of damage due to explosion overpressure has been carried by a number of
researchers, where Table 2.8 and Table 2.9 present the data from Clancey [6], which
looked at damage effects produced by a blast wave in general, and Stephens [7], which
focused on vulnerable refinery parts.
As for the fire damage cases reported in Table 2.1, the values given in Table 2.8 and
Table 2.9 are indicative only. The determination of the vulnerability of a plant/structure
should be determined based on an assessment of the criticality of the structure
followed by a proportionate modelling approach (i.e. one based on the criticality and
complexity).

©OGP8
Table 2.8 Damage Estimates for Common Structures Based on
Overpressure [6]
Pressure
Psig kPa
Damage
0.02 0.14 Annoying noise (137 dB if of low frequency 10-15 Hz)
0.03 0.21 Occasional breaking of large glass windows already under strain
0.04 0.28 Loud noise (143 dB), sonic boom, glass failure
0.1 0.69 Breakage of small windows under strain
0.15 1.03 Typical pressure for glass breakage
0.3 2.07 "Safe distance" (probability 0.95 of no serious damage1
below this
value); projectile limit; some damage to house ceilings; 10%
window glass broken
0.4 2.76 Limited minor structural damage
0.5-1.0 3.4-6.9 Large and small windows usually shattered; occasional damage
to window frames.
0.7 4.8 Minor damage to house structures
1.0 6.9 Partial demolition of houses, made uninhabitable
1.0-2.0 6.9-13.8 Corrugated asbestos shattered; corrugated steel or aluminium
panels, fastenings fail, followed by buckling; wood panels
(standard housing) fastenings fail, panels blown in
1.3 9.0 Steel frame of clad building slightly distorted
2 13.8 Partial collapse of walls and roofs of houses
2.0-3.0 13.8-20.7 Concrete or cinder block walls, not reinforced, shattered
2.3 15.8 Lower limit of serious structural damage
2.5 17.2 50% destruction of brickwork of houses
3 20.7 Heavy machines (3000 lb) in industrial building suffered little
damage; steel frame building distorted and pulled away from
foundations
3.0-4.0 20.7-27.6 Frameless, self-framing steel panel building demolished; rupture
of oil storage tanks
4 27.6 Cladding of light industrial buildings ruptured
5 34.5 Wooden utility poles snapped; tall hydraulic press (40,000 lb) in
building, slightly damaged
5.0-7.0 34.5-48.2 Nearly complete destruction of houses
7 48.2 Loaded, lighter weight (British) train wagons overturned
7.0-8.0 48.2-55.1 Brick panels, 8-12 inch thick, not reinforced, fail by shearing or
flexure
9 62 Loaded train boxcars completely demolished
10 68.9 Probable total destruction of buildings; heavy machine tools
(7,000 lb) moved and badly damaged, very heavy machine tools
(12,000 lb) survive
300 2068 Limit of crater lip
1
Understood to be to typical brick built buildings

©OGP 9
Table 2.9 Damage Estimates Based on Overpressure for Process Equipment [7] (legend on next page)
Overpressure, psiEquipment
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 12.0 14.0 16.0 18.0 20.0
Control house steel roof A C D N
Control house concrete
roof
A E P D N
Cooling tower B F O
Tank: cone roof D K U
Instrument cubicle A LM T
Fixed heater G I T
Reactor: chemical A I P T
Filter H F V T
Regenerator I IP T
Tank: floating roof K U D
Reactor: cracking I I T
Pipe supports P SO
Utilities: gas meter Q
Utilities: electronic H I T
Electric motor H I V
Blower Q T
Fractionation column R T
Pressure vessel:
horizontal
PI T
Utilities: gas regulator I MQ
Extraction column I V T
Steam turbine I M S V
Heat exchanger I T
Tank sphere I I T
Pressure vessel: vertical I T
Pump I V

©OGP10
Legend to Table 2.9:
A. Windows and gauges broken L. Power lines are severed
B. Louvres fail at 0.2-0.5 psi M. Controls are damaged
C. Switchgear is damaged from roof collapse N. Block walls fail
D. Roof collapses O. Frame collapses
E. Instruments are damaged P. Frame deforms
F. Inner parts are damaged Q. Case is damaged
G. Brick cracks R. Frame cracks
H. Debris - missile damage occurs S. Piping breaks
I. Unit moves and pipes break T. Unit overturns or is destroyed
J. Bracing fails U. Unit uplifts (0.9 tilted)
K. Unit uplifts (half tilted) V. Unit moves on foundation
2.2.2 Overpressure Loading
DNV OS-A101 [8] provides some generic overpressure values for various offshore units
including drill rigs, FPSOs and production platforms as detailed in Table 2.10.
Table 2.10 Nominal Design Blast Overpressures for Various Offshore Units
[8]
The characteristic representation of the overpressure load is via a triangular blast
profile and the response of the plant/structure to the explosion is primarily determined
by the ratio of the blast load duration, td, to the natural period of vibration of the
plant/structure, T as detailed in Table 2.11 [2].
In an impulsive response regime, the blast load is very short compared with the natural
period of the structural element. The duration of the load is such that the load has

©OGP 11
finished acting before the element has had time to respond. Due to inertial resistance of
the structure, most of the deformation occurs after the blast load has passed. Impulse is
an important aspect of damage-causing ability of this type of blast and may become a
controlling factor in design situations where the blast wave is of relatively short
duration.
In the quasi-static regime, the duration of the blast load is much longer than the natural
period of the structural element. In this case, the blast loading magnitude may be
considered constant while the element reaches its maximum deformation. For quasi-
static loading, the blast will cause the structure to deform while the loading is still
applied.
In the dynamic regime, the load duration is similar to the time taken for the element to
respond significantly. There is amplification of response above that which would result
from static application of the blast load.
Table 2.11 Regimes of Dynamic Response [2]
Impulsive td/T <
0.3
Dynamic 0.3 < td/T <
3.0
Quasi-static td/T >
3.0
Peak Load Preserving the
exact peak value is
not critical
Preserve peak value - the response is sensitive
to increases or decreases in peak load for a
smooth pressure pulse
Duration Preserving the
exact load duration
is not critical
Preserve load duration
since in this range it is
close to the natural
period of the structure.
Even slight changes
may affect response.
Not important if
response is elastic
but is critical when
response is plastic.
Impulse Accurate
representation of
impulse is not
critical
Accurate representation
of the impulse is
important
Accurate
representation of the
impulse is not
important
Rise Time Preserving rise
time is not
important
Preserving rise time is important; ignoring it
can significantly affect response
2.2.3 Drag Loading on Equipment
For the drag loading, the directional force on equipment is given by:
Fd = 0.5 ρ A Cd |v| v
where Fd is the drag force vector, ρ is the fluid density, A is the maximum cross
sectional area of the object in a plane normal to v, Cd is the drag coefficient and v is the
large scale fluid velocity ignoring spatial fluctuations in the vicinity of the object.
For small obstacle diameters, the drag coefficient can be estimated by using the values
given in Figure 2.1. For equipment with diameters greater than 2 m, it is recommended
to use the Direct Load Measurement (DLM) method in which the pressure difference
between upwind and downwind sides is computed (using Computational Fluid
Dynamics) and multiplied by the obstacle windage area for the X, Y and Z direction. A
description of this approach is given in [9].

©OGP12
Figure 2.1 Drag Coefficients, CD, for Various Shapes [9]
2.2.4 Response of Plant/Structure
Essentially three methods of analysis are available to calculate the response of a
structure subjected to transient loads as illustrated in Figure 2.2. These methods are
termed:
• Approximate methods
• Single degree of freedom
• Multiple degree of freedom

©OGP 13
Figure 2.2: Methods of Analysis
Approximate methods are limited to energy methods and static analysis methods. The
energy method (based on principle of equating work done by load to change in strain
energy in structure) are adequate for simple structural elements and load regimes but
for more complex structural elements and load configurations, these methods become
very laborious and time consuming. They are therefore not recommended for any but
the simplest cases. Static analysis methods have been used where quasi-static blast
loads act (i.e. dynamic amplification in response is minimal). As large conservatism can
occur, these methods are generally not recommended.
Single-degree-of-freedom (SDOF) methods are commonly used to model the response
of simple elements to dynamic loading. This method can only be used if the structural
system can be adequately idealised as a single-degree-of-freedom system (i.e. a real
system that is comparatively simple e.g. a single plate or beam). The SDOF model has
the ability to modify equations and parameters if a time-stepping procedure is employed
which enables a nonlinear system to be modelled. This method is most suited if the
primary requirement in determining the behaviour of a blast-loaded structure is its final
state (e.g. maximum displacement) rather than a detailed knowledge of its response
history.
Where a structure cannot be idealised as a SDOF system, a more rigorous approach is
required. This can be obtained by performing a multiple-degree-of-freedom (MDOF)
analysis using numerical techniques e.g. finite element analysis. Such analysis can be
carried out using commercially available software such as ANSYS, ABAQUS, NASTRAN,
DYNA-3D.
It should also be noted that the mechanical properties of materials are affected by the
dynamic loading induced by a blast load. In particular, those materials having definite
yield points and pronounced yielding zones show a marked variation in mechanical
properties with changes in loading rate. Yield strengths are generally higher under rapid
strain rates (as what happens under blast loads) than under slowly applied loads.
The strain rate dependency in steels is generally modelled using the Cowper-Symonds
relationship:

©OGP14
where σd is the dynamic stress at a particular strain rate, σ is the static stress at a
particular strain rate, is the uniaxial plastic strain rate and D and q are constants
specific to the steel.
Typical values for D and q are as follows:
• Mild steel: D = 40 s-1
, q = 5
• Stainless steel (grade 304); D = 100 s-1
, q = 10
2.3 Missiles
There are two possible types of missiles/projectiles. Primary missiles result from the
rupture of pressurised equipment such as pressure vessels or failure of rotating
machinery (e.g. gas turbines and pumps). Secondary missiles arise from the passage of
a blast wave which imparts energy to objects in its path. These objects could be small
tools, loose debris and other structures disrupted by the explosion.
Various models for the calculation of the missile velocity and range of missiles are
given in [10] and [11]. However, the models provide no information on the distribution of
mass, velocity or range of fragments to be expected.
Baker et al. ([12],[13]) compiled data on the number and distribution of fragments for 25
accidental bursts as shown in Table 2.12. As the data on most of the events considered
were limited, it was necessary to group similar events into six groups in order to yield
an adequate base for useful statistical analysis. The range for the source energy was
calculated based on the assumption that the total internal energy E of the vessel
contents is translated into fragment kinetic energy.
Baker also performed statistical analysis on each of the groups to yield estimates of
fragment-range distributions and fragment mass distributions as illustrated in Figure
2.3. It should, however, be noted that a number of problems still exist with regard to the
determination of missile loading, namely [9]:
• Fraction of explosion energy which contributes to fragment generation is unclear
• Methods do not exist to predict even the order of magnitude of the number of
fragments produced. Effect of parameters such as material, wall thickness and initial
pressure are not known.

©OGP 15
Table 2.12 Behaviour of fragments in some vessel explosions [10]
Event
Group
Number
Number
of
Events
Explosion
Material
Source
Energy (J)
Vessel
Shape
Vessel
Mass
Number of
Fragments
1 4 Propane,
anhydrous
ammonia
1.49 to 5.95 ×
105
Rail tank
car
25542 to
83900
14
2 9 LPG 3814 to 3921 Rail tank
car
25464 28
3 1 Air 5.2 × 1011
Cylinder
pipe and
spheres
145842 35
4 2 LPG,
propylene
550 Semitrailer
(cylinder)
6343 to
7840
31
5 3 Argon 244 to 1133 ×
1010
Sphere 48.3 to 187 14
6 1 Propane 24.8 Cylinder 512 11

©OGP16
Figure 2.3: Fragment range distribution from some accidental events [10]:
(a) event groups 1 and 2, and (b) event groups 3-6 (see Table 2.12 for event
groups)

©OGP 17
3.0 Guidance on use of data
3.1 General validity
The data set out in Section 2.0 are based on a review of the latest guidance in the
literature. However, the limits of applicability of the data should be recognised
particularly with regard to the damage data.
The vulnerability of plant/structure should generally be assessed via a recognised
analytical framework and should not rely on solely on data provided in Table 2.5 and
Table 2.6 for example. The analytical framework would typically involve numerical
simulations and the depth of those simulations would depend on the complexity of the
problem and the critically of the plant/structure. It is highly recommended that expert
judgement is sought for those assessments.
3.2 Uncertainties
The main area of uncertainty relate to the numerical modelling of plant/structure under
dynamic loads such as blast loading. The complexity of the problem requires
simplifying assumptions regarding the:
• Structural model and boundary conditions
• Loading characteristics
• Geometric nonlinearity
• Material nonlinearity
Comprehensive data on material behaviour at elevated temperatures and under dynamic
loading are not available.
4.0 Review of data sources
The principal source of the fire and explosion criteria presented in Section 2.0 is the
UKOOA/ HSE Fire and Explosion Guidance [2]; besides the references included in the
table captions and text of Section 2.0, additional information has been obtained from the
following references:
• Fire [11], [14]
• Explosion [14]
The data sources from which the critical temperatures given in Table 2.2 were obtained
are identified in Table 4.1; [2] gives the full references for these data sources.

©OGP18
Table 4.1 Data sources for commonly used critical temperatures given in
Table 2.2 [2]
Temperature
(°C)
Use Source (see
[2] for full
reference)
Criteria
550-620 Structural steel
onshore
ASFP, 2002
(BS 5950)
Temperature at which fully
stressed carbon steel loses
its design margin of safety
427 LPG tanks
(France and Italy)
ISO 23251:2006
(2007)
Based on the pressure relief
valve setting
400 Structural steel
offshore
ISO 13702,
1999
Temperature at which the
yield stress is reduced to the
minimum allowable strength
under operating loading
conditions
300 LPG tanks
(UK and Germany)
LPGA CoP 1,
1998
Integrity of LPG vessel is not
compromised at
temperatures up to 300°C for
90 minutes
200 Structural
aluminium
offshore
ISO 13702,
1999
Temperature at which the
yield stress is reduced to the
minimum allowable strength
under operating loading
conditions
180 Unexposed face of
a
division/boundary
ISO 834 BS 476 Maximum allowable
temperature at only one point
of the unexposed face in a
furnace test
140 Unexposed face of
a
division/boundary
ISO 834 BS 476 Maximum allowable average
temperature of the
unexposed face in a furnace
test
40 Surface of safety
related control
panel
ISO 13702 Maximum temperature at
which control system will
continue to function
5.0 Recommended data sources for further information
The following references should be consulted if further information is required.
• Structural Dynamics: [15]
• Structural response to dynamic loading: [16][17]
• Offshore fire and blast loading: [18]

©OGP 19
6.0 References
6.1 References for Sections 2.0 to 4.0
[1] Medonos S, 2003. Improvement of Rule Sets for Quantitative Risk Assessment in
Various Industrial Sectors, Safety and Reliability, Proc. ESREL 2003 Conf., Vol. 2,
A.A. Balkema Publishers, ISBN 5809 596 7.
[2] UKOOA/HSE, 2007. Fire and Explosion Guidance, Issue 1.
[3] Steel Construction Institute, 2001. Elevated temperature and high strain rate
properties of offshore steels, Offshore Technology Report OTO 2001 020, Sudbury,
Suffolk: HSE Books. http://www.hse.gov.uk/research/otopdf/2001/oto01020.pdf.
[4] Fire safety engineering. Structural response and fire spread beyond the enclosure of
origin, BS ISO/TR 13387-6:1999, ISBN 0 580 34037 6.
[5] NORSOK N-004 Design of Steel Structures, N-004, Rev.1, December 1998.
[6] Clancey V J, 1972. Diagnostic features of explosion damage, 6th
Intl. Meeting on
Forensic Sciences, Edinburgh, Scotland.
[7] Stephens M M, 1970. Minimising damage to refineries from nuclear attack, natural or
other disasters, Office of Oil and Gas, US Department of the Interior.
[8] DNV, 2005. DNV OS-A101, Safety Principles and Arrangements, DNV Offshore
Standard.
[9] Natabelle Technology Ltd., 1999. Explosion Loading on Topsides Equipment, Part 1,
Treatment of Explosion Loads, Response Analysis and Design, Offshore Technology
Report OTO 1999 046, Sudbury, Suffolk: HSE Books.
http://www.hse.gov.uk/research/otopdf/1999/oto99046.pdf.
[10] CCPS, 1994. Guidelines for evaluating the characteristics of vapor cloud explosions,
flash fires and BLEVEs, New York: AIChE.
[11] Lees’ Loss Prevention in the Process Industries, Hazard Identification, Assessment and
Control, 3rd
ed., Mannan S (Ed.), 2004.
[12] Baker W E, Kulesz J J, Ricker R E, Westine P S, Parr V B, Vargas L M, and Mosely
P K, 1978. Workbook for Estimating the Effects of Accidental Explosion in Propellant
Handling Systems. NASA Contractors Report 3023, Contract NAS3-20497. NASA
Lewis Research Center, Cleveland, Ohio.
[13] Baker W E, Cox P A, Westine P S, Kulesz J J, and Strehlow R A, 1983. Explosion
Hazards and Evaluation, Amsterdam: Elsevier Scientific Publishing Company.
[14] Steel Construction Institute, 2005. Protection of Piping Systems subject to Fires and
Explosions, Technical Note 8.
6.2 References for other data sources examined
[15] Biggs, J M, 1964. Introduction to Structural Dynamics, New York: McGraw-Hill
Companies.
[16] Steel Construction Institute, 2002. Simplified Methods for Analysis of Response to
Dynamic Loading, Technical Note 7.
[17] Steel Construction Institute, 2007. An Advanced SDOF Model for Steel Members
Subject to Explosion Loading: Material Rate Sensitivity, Technical Note 10.
[18] API, 2006. Recommended Practice for the Design of Offshore Facilities Against Fire
and Blast Loading, API Recommended Practice 2FB, 1st
. ed.

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