International Conference on Hydrogen Safety 2011 – San Francisco, 12 Sept 2011 Risk informed...
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Transcript of International Conference on Hydrogen Safety 2011 – San Francisco, 12 Sept 2011 Risk informed...
International Conference on Hydrogen Safety 2011 – San Francisco, 12 Sept 2011
Risk informed separation distances for hydrogen refuelling stations
Frederic BarthAir Liquide Hydrogen Energy
2 ICHS 2011 – San Francisco, 12 Sept 2011
Background and general motivation
Approach developed for ISO/DIS 20100 Gaseous Hydrogen – Fuelling stations within TC197/WG 11 Fueling stations by TG1 Separation distances
To substantiate lay-out requirements for HRS sub-systems Applied to gaseous hydrogen systems
Hydrogen supply system (e.g. tube trailer) Hydrogen compression skid Hydrogen buffer storage Hydrogen dispensers
Hydrogen is being developed for generalized use as an energy carrier: Higher operating pressures than previously considered Installation and use in public settings Variety of applications (e.g. RV fuelling stations, back-up power, materials
handling…)
Inherently safe designs and built-in safety measures
Need of a robust rationale and approach for addressing these new applications consistently
3 ICHS 2011 – San Francisco, 12 Sept 2011
Separation distances in codes & standards Rationale
Purpose : a generic means for mitigating the effect of a foreseeable incident and preventing a minor incident escalating into a larger incident (EIGA IGC 75/05)
Apply separation as appropriate, along with other means, to achieve freedom from unacceptable risk
Separation is not always necessary, nor most appropriate means
Where applied, appropriate separation can be defined by application of a risk criterion
Protection against catastrophic events is essentially achieved by other means than separation, such as prevention, specific means of mitigation, or emergency response, which are also addressed.
4 ICHS 2011 – San Francisco, 12 Sept 2011
Separation distances in codes & standards Form of specification
Continue to express requirements by means of a good table that is suitable for the covered application
Most practical Tabled distances have been checked Same distance for similar systems supports standardization Relying on a formulas raises the risk that design parameters will be chosen
to minimise safety distance requirements although this choice does not reduce the actual risk level to exposures
Practical value added of specifying distance by means of formulas is not clear
Different applications may require different tables e.g. Fuelling stations, bulk hydrogen storage systems, hydrogen
installations in non industrial environment
5 ICHS 2011 – San Francisco, 12 Sept 2011
Table based separation distances specification – Basic steps
Table Lines : Exposures or sources of hazard ; Columns: system category
1. Select system characteristics that fundamentally determine actual risk impact
2. Define system categories associated to a graduation of risk impact Taking into account different types of equipment actually used Limit the number of categories to justified need
3. Use a risk model to determine the separation distances for each category, by application of a criterion on estimated residual risk,
Based on max values for the category Higher risk Greater separation
4. Populate the distance table and evaluate the result.
6 ICHS 2011 – San Francisco, 12 Sept 2011
Selection of system characteristics that fundamentally determine actual risk impact
Separation distances should not be determined only by Pressure and Internal Diameter. Need to integrate fundamental factors determining actual risk impact, such as inventory, system complexity, and exposure criticality
Over sensitivity to a detail design parameter such as internal diameter needs to be avoided
7 ICHS 2011 – San Francisco, 12 Sept 2011
Selection of system characteristics that fundamentally determine actual risk impact
1. Storage system size Small Large
2. Complexity level as reflected by number of components Very simple (for Small systems only) Simple Complex
3. For Small systems only : pressure Regular High
8 ICHS 2011 – San Francisco, 12 Sept 2011
Categorization of compressed hydrogen storage systems
Boundaries defined according to equipment types in use
Storage classification for determination of clearance distances
10
100
100 1000 10000 100000
Water volume (L)
Se
rvic
e p
res
su
re (
MP
a)
3
1
2
P <= 55 MPa
P > 55 Mpa
Stored quantity
> 100 kg
3000
55
1 kg
Storage classification for determination of clearance distances
10
100
100 1000 10000 100000
Water volume (L)
Se
rvic
e p
res
su
re (
MP
a)
3
1
2
P <= 55 MPa
P > 55 Mpa
Stored quantity
> 100 kg
3000
55
1 kg
9 ICHS 2011 – San Francisco, 12 Sept 2011
Resulting categorization for gaseous hydrogen storage systems
8 categories
Small systems < 3000L or < 100 kg
Medium to high pressure <= 55 MPa
Very high pressure > 55 MPa
Large systems > 3000L and > 100kg
Size-pressure category 1 Size-pressure category 2 Size-pressure
category 3
Very simple
Simple Complex Very
simple Simple Complex Simple Complex
10 ICHS 2011 – San Francisco, 12 Sept 2011
Leaks
FearedEffect
Risk model for determination of a separation distance requirement from a system
oc
c./
yr
10-6
10-5
10-4
10-3
10-2
Target
Fre
qu
en
cy
Leak rate (g/s)
0,10,01 101 100
10-6
10-5
10-4
10-3
10
Leak rate (g/s)
0,10,01 101 100
Separation distanceTo be applied
1 103 30
Separationdistance (m)
Referenceleak size
10-110
Cumulated frequency of feared effects from leaks greater than X g/s
11 ICHS 2011 – San Francisco, 12 Sept 2011
Key parameters of risk model
Cumulative leak frequency vs leak sizeSee next slides
Probability of having the feared event (injury) when a leak occursPignition x Geometric factor = 0,04 x 0,125 = 0,005
Consequence model providing distance up to which leaks can produce the feared event, in function of leak size and type of feared effect (e.g thermal effects or 4% H2 concentration)
Sandia National Laboratories jet release and fire models
Target value for the feared event frequency,Non-critical exposure: 10-5 /yr
Critical exposure: 4 10-6/yr
Risk model does not provide an accurate evaluation of risk, but allows to take into consideration the main risk factors consistently
Separation distances are risk informed
12 ICHS 2011 – San Francisco, 12 Sept 2011
Determination of system leak frequency distributionin function of component leak frequency distribution
Consider main contributors to leaks Joints, Valves, Hoses, Compressors
Estimate cumulated leak frequency in function leak size (% of flow section) for each type of component, from available statistical data
Estimate cumulated leak frequency in function of leak size for the whole system, by summation of contributing component leak frequency data
13 ICHS 2011 – San Francisco, 12 Sept 2011
Component leak frequency – Source of input to risk model
Risk model requires leak frequency input for following leak size ranges : [0.01% ; 0,1%], [0.1% ; 1%][1% ; 10%][10% ; 100%]
Use of published leak frequencies compiled by SNL (J. LaChance) Extract for valves, where information on leak size is provided (34% of records):
Data input to risk model:Leak size range [0.01% ; 0,1%] [0.1% ; 1%] [1% ; 10%] [10% ; 100%]Log. average freq. of extrapolated “Small leaks” “Large leaks” “Ruptures”
Component
Specific Component
Type Severity Frequency UnitsLeak Size
Description Source Type Source
Valve Manual, 2 inch Small Leak 1,40E-05 Per Year >1 mm HydrocarbonSpouge, John, "New Generic Leak Frequencies for Process Equipment, “Process Safety Progress, Vol. 24, No. 4, 2005
Valve Manual, 6 inch Small Leak 4,80E-05 Per Year >1 mm HydrocarbonSpouge, John, "New Generic Leak Frequencies for Process Equipment, “Process Safety Progress, Vol. 24, No. 4, 2005
Valve Manual, 18 inch Small Leak 2,20E-04 Per Year >1 mm HydrocarbonSpouge, John, "New Generic Leak Frequencies for Process Equipment, “Process Safety Progress, Vol. 24, No. 4, 2005
Valve
Actuated, 6 inch diam non-pipeline Small Leak 2,60E-04 Per Year >1 mm Hydrocarbon
Spouge, John, "New Generic Leak Frequencies for Process Equipment, “Process Safety Progress, Vol. 24, No. 4, 2005
Valve All Sizes Small Leak 1,00E-03 Per Year1% cross
sectional areaChemical Process
Cox, A.W., Lees, F.P., Ang, M.L., "Classifications of Hazardous Locations," Institution of Chemical Engineers, 2003
Valve All Sizes Large Leak 1,00E-04 Per Year10% cross
sectional areaChemical Process
Cox, A.W., Lees, F.P., Ang, M.L., "Classifications of Hazardous Locations," Institution of Chemical Engineers, 2003
Valve Manual, 6 inch Rupture 4,80E-07 Per Year >50 mm HydrocarbonSpouge, John, "New Generic Leak Frequencies for Process Equipment, “Process Safety Progress, Vol. 24, No. 4, 2005
Valve
Actuated, 6 inch diam non-pipeline Rupture 1,90E-06 Per Year >50 mm Hydrocarbon
Spouge, John, "New Generic Leak Frequencies for Process Equipment, “Process Safety Progress, Vol. 24, No. 4, 2005
Valve Manual, 18 inch Rupture 2,30E-06 Per Year >50 mm HydrocarbonSpouge, John, "New Generic Leak Frequencies for Process Equipment, “Process Safety Progress, Vol. 24, No. 4, 2005
Valve All Sizes Rupture 1,00E-05 Per Year100% cross
sectional areaChemical Process
Cox, A.W., Lees, F.P., Ang, M.L., "Classifications of Hazardous Locations," Institution of Chemical Engineers, 2003
14 ICHS 2011 – San Francisco, 12 Sept 2011
Risk model leak frequency input for valves (1)
Valves - Small leaks - Cumulative leak frequency
1,00E-05
1,00E-04
1,00E-03
1,00E-02
1,00E-01
0,000% 0,001% 0,010% 0,100% 1,000% 10,000% 100,000%
Leak area (%)
Cu
mu
lati
ve f
req
uen
cy (
/yr)
Original Data SNL collected Leak frequency
Small leaks - Median
Frequency and size of “small leaks”
15 ICHS 2011 – San Francisco, 12 Sept 2011
Risk model leak frequency input for valves (2)
Frequency and size of “small leaks”
Valves - Ruptures - Cumulative leak frequency
1,00E-07
1,00E-06
1,00E-05
1,00E-04
0,000% 0,001% 0,010% 0,100% 1,000% 10,000% 100,000%
Leak area (%)
Cu
mu
lati
ve f
req
uen
cy (
/yr)
Original Data SNL collected Median freq.
Ruptures - Median
16 ICHS 2011 – San Francisco, 12 Sept 2011
Risk model leak frequency input for valves (3)
Note : adequacy of using log-average of “Small leak”, “Large leak”, and “Rupture” frequencies as risk model input for [0.1% ; 1%], [1% ; 10%],[10% ; 100%] ranges was verified for all types of components
Valves - Cumulative leak frequency - ISO interpretation
1,00E-07
1,00E-06
1,00E-05
1,00E-04
1,00E-03
1,00E-02
1,00E-01
0,000% 0,001% 0,010% 0,100% 1,000% 10,000% 100,000% 1000,000%
Leak area (%)
Cum
ulat
ive
freq
uenc
y (/
yr)
Original Data SNL Median freq. ISO Cumulative
Small leaks freq.
Large leaks freq.
Ruptures freq.
[0,1% - 1%] leak frequ
[10% - 100%] leak frequ
"Small leaks" size range"Ruptures" size range
ISO cumulative frequency curve
[1% - 10%] leak frequ
17 ICHS 2011 – San Francisco, 12 Sept 2011
Risk model component leak frequency functions
Cumulated Leak Frequency in function of Leak area
1,00E-06
1,00E-05
1,00E-04
1,00E-03
1,00E-02
1,00E-01
1,00E+00
0,01% 0,10% 1,00% 10,00%
%A
Lea
k F
req
uen
cy (
/yr)
Compressor Hoses Joints Valves
18 ICHS 2011 – San Francisco, 12 Sept 2011
Consequence Model
Interpolation of flame length and flammable cloud length formulas developed by SNL (Bill Houf) :
Targeted hazardous effect: Flammable atmosphere
Targeted hazardous effect: Thermal effects
SD = 1,02 * LD * SP0,46
Or alternatively:
SD = 1,34 * LQ0,5
SD = 0,84 * LD * SP0,46
Or alternatively:
SD = 1,11 * LQ0,5
With LQ = 0,58 * LD2 * SP0,92, which is
equivalent to LQ = 0,73 * LA * SP0,92
19 ICHS 2011 – San Francisco, 12 Sept 2011
Risk informed leak diameters& separation distances for storage/transfer systems
Very simple Simple Complex Very simple Simple Complex Simple Complex
MID mm 8 8 8 8 8 8 12,3 12,3
P Mpa 55 55 55 110 110 110 25,0 25,0
HPI Joint eq. 15 60 135 15 60 135 45 100
Probability 0,04 0,04 0,04 0,04 0,04 0,04 0,106 0,106
mm 0,32 0,52 0,32 0,52 0,76 1,07
% 0,16% 0,42% 0,16% 0,42% 0,38% 0,75%
g/s 2,4 6,3 4,5 12,0 6,5 12,9
Flash fire distance m 2,1 3,4 2,8 4,6 3,4 4,8
Therm. effects dist. m 1,7 2,8 2,4 3,9 2,8 4,0
mm 0,24 0,56 0,91 0,24 0,56 0,91 1,51 2,14
% flow area 0,09% 0,48% 1,30% 0,09% 0,48% 1,30% 1,50% 3,00%
g/s 1,3 7,3 19,7 2,5 13,8 37,3 25,9 51,8
Flash fire distance m 1,5 3,6 5,9 2,1 5,0 8,2 6,8 9,6
Therm. effects dist. m 1,3 3,0 4,9 1,8 4,1 6,8 5,7 8,0
Cri
tica
l
Small (<= 3000L and <=100 kg)
Large(> 3000L or > 100 kg)
Category 1 (<= 55 Mpa)
Category 3Category 2 (> 55 Mpa)
System
IgnitionHyp
oth
.E
xp
osu
re Tar
get
:
10-5
/yr Leak size
Tar
get
:
4 10
-6/y
r Leak size
Reg
ula
r
20 ICHS 2011 – San Francisco, 12 Sept 2011
Separation distance requirements for compressedfor gaseous hydrogen storage/transfer systems
Distance in meters
VS S C VS S C S C
Occupied buildings - openable openings and air intakes 1,5 4,0 6,0 2,0 5,0 8,0 7,0 10,0
Occupied buildings - bay-windows* - 5,0 8,0 - 7,0 12,0 9,0 15,0
Unoccupied buildings - openable openings and air intakes - 2,0 3,0 - 3,0 5,0 4,0 5,0
Buildings of combustible material 1,5 3,0 5,0 2,0 4,0 7,0 8,0 8,0
Flammable liquids above ground <= 4000 L 1,0 2,0 3,0 - 2,5 4,0 8,0 8,0
Flammable liquids above ground > 4000 L 1,5 3,0 5,0 2,0 4,0 7,0 8,0 8,0
Underground flammable liquid storage - vents and fill openings - - 5,0 5,0
Stocks of combustible material 1,0 2,0 3,0 - 2,5 4,0 8,0 8,0
Flammable gas storage above ground > 500 Nm3 1,0 2,0 3,0 - 2,5 4,0 8,0 8,0
Facility lot line - 2,0 3,0 - 3,0 5,0 4,0 5,0
Areas not subjected to restrictions of activity - 2,0 3,0 - 3,0 5,0 4,0 5,0
Pedestrian and vehicle low-speed passage ways - 2,0 3,0 - 3,0 5,0 4,0 5,0
High voltage lines and trolley or train power line - -
Other overhead power lines - -
Roadways - -
* non-re-enforced to withstand overpressure effects
3,0
5,0
5,0
Cat. 3(Q > 100 kg)
10,0
5,0
3,0
5,0
Safety distances (m)
Exp
osu
res
or
So
urc
es o
f h
azar
d
Category 1 (SP <= 55 MPa)
Category 2 (55 < SP <= 110 MPa)
5,0
5,0
5,0
5,0
Passive hydrogen systems
21 ICHS 2011 – San Francisco, 12 Sept 2011
Thank [email protected]