International Conference on Hydrogen Safety 2011 – San Francisco, 12 Sept 2011 Risk informed separation distances for hydrogen refuelling stations Frederic

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


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.


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


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.


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


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


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


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


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


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


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


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

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



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




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”



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



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


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


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


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


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


Thank [email protected]

Documents

International Conference on Hydrogen Safety 2011 – San Francisco, 12 Sept 2011 Risk informed separation distances for hydrogen refuelling stations Frederic