Risk Assessment Data Directory Report No. 434 – 15 March 2010
Vulnerability of plant/structure International Association of Oil & Gas Producers
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RADD – Vulnerability of plant/structure
contents 1.0 1.1 1.2
Scope and Definitions ........................................................... 1 Application ...................................................................................................... 1 Definitions ....................................................................................................... 1
2.0 2.1
Summary of Recommended Data ............................................ 1 Fire ................................................................................................................... 2
2.1.1 2.1.2
Vulnerability of Plant/Structure under Fire Loading ............................................... 2 Derivation of Fire Loads ............................................................................................ 4
2.2
Explosions....................................................................................................... 7
2.2.1 2.2.2 2.2.3 2.2.4
Vulnerability of Plant/Structure to Explosions ........................................................ 7 Overpressure Loading ............................................................................................. 10 Drag Loading on Equipment ................................................................................... 11 Response of Plant/Structure ................................................................................... 12
2.3
Missiles .......................................................................................................... 14
3.0 3.1 3.2
Guidance on use of data ...................................................... 17 General validity ............................................................................................. 17 Uncertainties ................................................................................................. 17
4.0
Review of data sources ....................................................... 17
5.0
Recommended data sources for further information ............ 18
6.0 6.1 6.2
References .......................................................................... 19 References for Sections 2.0 to 4.0 .............................................................. 19 References for other data sources examined ............................................ 19
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RADD – Vulnerability of plant/structure
Abbreviations: 2D AIChE API BLEVE BS CCPS CoP DLM DNV ESREL FPSO HSE ISO LPG LPGA MDOF QRA SDOF UKOOA
Two-dimensional American Institute of Chemical Engineers American Petroleum Institution Boiling Liquid Expanding Vapour Explosion British Standard Center for Chemical Process Safety Code of Practice Direct Load Measurement Det Norske Veritas European Safety and Reliability Floating Production, Storage and Offloading unit (UK) Health and Safety Executive International Organization for Standardization Liquefied Petroleum Gas LP Gas Association Multiple Degree of Freedom Quantitative Risk Assessment Single Degree Of Freedom United Kingdom Offshore Operators Association (now Oil & Gas UK)
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RADD – Vulnerability of plant/structure
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
•
Em issivity
•
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.
•
Im pulse
•
Radiative Flux Refers to the transfer of heat from one body to another by thermal radiation.
•
Rise Tim e
2.0
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.
The integral of a force or load over an interval of time.
The time taken for the explosion overpressure to increase from zero to the peak overpressure.
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
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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 Tim e to Failure of Pipework, Vessels, Equipm ent and Structures affected by Fire [1]
2
Fire Scenario (Note 1)
Failure
Tim e 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
Flame with heat flux of 250 kW/m2 impinging onto a connector or flange (clamp or bolted) with no fire protection. Flame with heat flux of 250 kW/m2 impinging onto a valve with no fire protection. Flame with heat flux of 250 kW/m2 impinging onto a safety valve with no fire protection.
Hub connector or flange (clamp or bolted), loss of tightness.
< 5 min
Valve, loss of tightness.
< 10 min
Safety valve, opens at a pressure lower than the setting pressure.
< 10 min
Flame with heat flux of 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
Flame with heat flux of 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.
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RADD – Vulnerability of plant/structure
Fire Scenario (Note 1)
Failure
Tim e to Failure (Note 2)
Flame with heat flux of 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.
< 40 min depending on the size of the pipe and fire intensity.
Flame with heat flux of 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
Flame with heat flux of 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. Collapse of structure or its part leading to loss of tightness of pipework and large releases of hazardous fluids.
< 15 min depending on the member size
Collapse of atmospheric storage tanks, road tankers, rail tank cars and marine tankers leading to large releases of hazardous fluids.
< 40 min depending on the 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.
Flame with heat flux of 250 kW/m2 impinging locally onto a joint of structural members or engulfing several joints. Flame with heat flux of 250 kW/m2 impinging onto the storage or transport tanks with no fire protection.
< 30 min depending on the member sizes.
Notes
1. The time to failure for heat fluxes other than 250 kW/m2 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.
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Table 2.2 Com m only used critical tem peratures [2] Exposed Structure Structural steel onshore LPG tanks (France and Italy) Structural steel offshore LPG tanks (UK and Germany) Structural aluminium offshore Unexposed face of a division/boundary Unexposed face of a division/boundary Surface of safety related control panel
Tem perature (°C) 550-620 427 400 300 200 180 140 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)
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•
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) Flame Length (m) Radiative flux (kW/m2) Convective flux (kW/m2) Total heat flux (kW/m2) Flame emissivity
0.1 5 80 100
1 15 130 120
10 40 180 120
>30 65 230 120
180 0.25
250 0.4
300 0.55
350 0.7
Table 2.4 Characteristic Data for High Pressure Two-Phase Jet Fires [2] Fuel m ix of 30% gas, 70% liquid by m ass Size (kg/s) Flame Length (m) Radiative flux (kW/m2) Convective flux (kW/m2) Total heat flux (kW/m2) Flame emissivity
0.1 5 100
1 13 180
10 35 230
>30 60 280
Flashing Liquid fires (e.g. propane/butane) 1 not given in [2] 160
100
120
120
120
70
200
300
350
400
230
0.3
0.55
0.7
0.85
1
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Table 2.5 Characteristic Data for Pool Fires on Installations [2] Methanol Pool
Typical Pool Diameter (m) Flame Length (m) Mass burning rate (kg/(m2s))
Radiative flux (kW/m2) Convective flux (kW/m2) Total heat flux (kW/m2) Flame emissivity
5 Equal to pool diameter 0.03
35 0 35 0.25
Sm all Hydrocarbon Pool 5 Up to twice pool diameter Crude: 0.045 0.06 Diesel: 0.055 Kerosene: 0.06 Condensate: 0.10 C3/C4s: 0.12 230 20 250 0.9
Table 2.6 Characteristic Data for Pool Fires on Sea [2] Typical Pool Diameter Flame Length (m) Mass burning rate (kg/(m2s))
Radiative flux (kW/m2) Convective flux (kW/m2) Total heat flux (kW/m2) Flame emissivity
> 10 Up to twice diameter Crude: 0.045 - 0.06 Diesel: 0.055 Kerosene: 0.06 Condensate: 0.10 C3/C4s: 0.20 230 20 250 0.9
Table 2.7 Characteristic Fire Loading for Pressure Vessels and Other Equipm ent [5]
Local Peak Heat Load (kW/m2) Global Average Heat Load (kW/m2)
Jet Fire 0.1 kg/s < leak leak rate > 2 kg/s rate < 2 kg/s 250 350 0 100
Pool Fire
150 100
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.
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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).
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Table 2.8 Dam age Estim ates for Com m on Structures Based on Overpressure [6] Pressure Psig kPa 0.02 0.14 0.03 0.21 0.04 0.28 0.1 0.69 0.15 1.03 0.3 2.07
1
8
0.4 0.5-1.0
2.76 3.4-6.9
0.7 1.0 1.0-2.0
4.8 6.9 6.9-13.8
1.3 2 2.0-3.0 2.3 2.5 3
9.0 13.8 13.8-20.7 15.8 17.2 20.7
3.0-4.0
20.7-27.6
4 5
27.6 34.5
5.0-7.0 7 7.0-8.0
34.5-48.2 48.2 48.2-55.1
9 10
62 68.9
300
2068
Dam age Annoying noise (137 dB if of low frequency 10-15 Hz) Occasional breaking of large glass windows already under strain Loud noise (143 dB), sonic boom, glass failure Breakage of small windows under strain Typical pressure for glass breakage "Safe distance" (probability 0.95 of no serious damage1 below this value); projectile limit; some damage to house ceilings; 10% window glass broken Limited minor structural damage Large and small windows usually shattered; occasional damage to window frames. Minor damage to house structures Partial demolition of houses, made uninhabitable Corrugated asbestos shattered; corrugated steel or aluminium panels, fastenings fail, followed by buckling; wood panels (standard housing) fastenings fail, panels blown in Steel frame of clad building slightly distorted Partial collapse of walls and roofs of houses Concrete or cinder block walls, not reinforced, shattered Lower limit of serious structural damage 50% destruction of brickwork of houses Heavy machines (3000 lb) in industrial building suffered little damage; steel frame building distorted and pulled away from foundations Frameless, self-framing steel panel building demolished; rupture of oil storage tanks Cladding of light industrial buildings ruptured Wooden utility poles snapped; tall hydraulic press (40,000 lb) in building, slightly damaged Nearly complete destruction of houses Loaded, lighter weight (British) train wagons overturned Brick panels, 8-12 inch thick, not reinforced, fail by shearing or flexure Loaded train boxcars completely demolished Probable total destruction of buildings; heavy machine tools (7,000 lb) moved and badly damaged, very heavy machine tools (12,000 lb) survive Limit of crater lip
Understood to be to typical brick built buildings
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Table 2.9 Dam age Estim ates Based on Overpressure for Process Equipm ent [7] (legend on next page) Equipment
Overpressure, psi 0.5
1.0
1.5
Control house steel roof
A
C
D
Control house concrete roof Cooling tower
A
E
P
Tank: cone roof Instrument cubicle
B
2.0
2.5
3.0
3.5
4.0
4.5
5.0
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
N D
N
F
O
D
K A
U
LM
Fixed heater
G
Reactor: chemical
A
Filter
H
T
I
T I
P
T
F
Regenerator
I
Tank: floating roof
K
V IP
T
T U
Reactor: cracking
I
Pipe supports
P
D I
T
SO
Utilities: gas meter
Q
Utilities: electronic
H
I
Electric motor
H
Blower
Q
Fractionation column
5.5
T I
V T
R
Pressure vessel: horizontal Utilities: gas regulator
T PI
T
I
Extraction column
MQ I
V
Steam turbine
I
Heat exchanger
I
Tank sphere
T M
I
I
Pressure vessel: vertical
I
Pump
I
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V
T T
T V
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Legend to Table 2.9: A. Windows and gauges broken B. Louvres fail at 0.2-0.5 psi
L. Power lines are severed M. Controls are damaged
C. Switchgear is damaged from roof collapse
N. Block walls fail
D. Roof collapses E. Instruments are damaged
O. Frame collapses P. Frame deforms
F. Inner parts are damaged
Q. Case is damaged
G. Brick cracks H. Debris - missile damage occurs
R. Frame cracks S. Piping breaks
I. Unit moves and pipes break
T. Unit overturns or is destroyed
J. Bracing fails K. Unit uplifts (half tilted)
U. Unit uplifts (0.9 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 Nom inal 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
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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 quasistatic 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 Regim es of Dynam ic Response [2]
Peak Load
Duration
Impulse
Rise Time
2.2.3
Im pulsive t d /T < 0.3 Preserving the exact peak value is not critical Preserving the exact load duration is not critical
Accurate representation of impulse is not critical Preserving rise time is not important
Dynam ic 0.3 < t d /T < Quasi-static t d /T > 3.0 3.0 Preserve peak value - the response is sensitive to increases or decreases in peak load for a smooth pressure pulse Preserve load duration Not important if since in this range it is response is elastic close to the natural but is critical when period of the structure. response is plastic. Even slight changes may affect response. Accurate representation Accurate of the impulse is representation of the important impulse is not important Preserving rise time is important; ignoring it can significantly affect response
Drag Loading on Equipment
For the drag loading, the directional force on equipment is given by: F d = 0.5 ρ A Cd |v| v where F d 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].
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Figure 2.1 Drag Coefficients, C D , 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
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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:
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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.
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Table 2.12 Behaviour of fragm ents in som e vessel explosions [10] Event Group Number 1
Number of Events 4
Explosion Material
Source Energy (J)
Vessel Shape
Vessel Mass
Number of Fragments
1.49 to 5.95 × 105
Rail tank car
25542 to 83900
14
9
Propane, anhydrous ammonia LPG
2
3814 to 3921
25464
28
3
1
Air
5.2 × 1011
145842
35
4
2
550
3
6343 to 7840 48.3 to 187
31
5
LPG, propylene Argon
Rail tank car Cylinder pipe and spheres Semitrailer (cylinder) Sphere
6
1
Propane
Cylinder
512
11
244 to 1133 × 1010 24.8
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Figure 2.3: Fragm ent range distribution from som e accidental events [10]: (a) event groups 1 and 2, and (b) event groups 3-6 (see Table 2.12 for event groups)
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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.
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RADD – Vulnerability of plant/structure
Table 4.1 Data sources for com m only used critical tem peratures given in Table 2.2 [2] Tem perature (°C) 550-620
427
Structural steel onshore
Source (see [2] for full reference) ASFP, 2002 (BS 5950)
LPG tanks (France and Italy) Structural steel offshore
ISO 23251:2006 (2007) ISO 13702, 1999
300
LPG tanks (UK and Germany)
LPGA CoP 1, 1998
200
Structural aluminium offshore
180
Unexposed face of a division/boundary
ISO 834 BS 476
140
Unexposed face of a division/boundary
ISO 834 BS 476
40
Surface of safety related control panel
400
5.0
Use
ISO 13702, 1999
ISO 13702
Criteria
Temperature at which fully stressed carbon steel loses its design margin of safety Based on the pressure relief valve setting Temperature at which the yield stress is reduced to the minimum allowable strength under operating loading conditions Integrity of LPG vessel is not compromised at temperatures up to 300°C for 90 minutes Temperature at which the yield stress is reduced to the minimum allowable strength under operating loading conditions Maximum allowable temperature at only one point of the unexposed face in a furnace test Maximum allowable average temperature of the unexposed face in a furnace test Maximum temperature at which control system will continue to function
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:
•
Offshore fire and blast loading: [18]
18
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[16][17]
RADD – Vulnerability of plant/structure
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. Steel Construction Institute, 2002. Simplified Methods for Analysis of Response to Dynamic Loading, Technical Note 7. Steel Construction Institute, 2007. An Advanced SDOF Model for Steel Members Subject to Explosion Loading: Material Rate Sensitivity, Technical Note 10. API, 2006. Recommended Practice for the Design of Offshore Facilities Against Fire and Blast Loading, API Recommended Practice 2FB, 1st. ed.
[16] [17] [18]
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19
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