INTERNATIONAL CONFERENCEON HYDROGEN SAFETY

September 8-10, 2005 – PISE - ITALY

230003_Barthélémy, H. and Allidières, L.,Gaseous hydrogen Refuelling Stations : Selection of Materials for Hydrogen High

Pressure Fuelling Connectors

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EXAMPLE OF FUELLING STATION FOR EXAMPLE OF FUELLING STATION FOR HYDROGEN VEHICLESHYDROGEN VEHICLES

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HYDROGEN EMBRITTLEMENTHYDROGEN EMBRITTLEMENT

Internal

External

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1 - COMBINED STATE :

Hydrogen attack

2 - IN METALLIC SOLUTION :

Gaseous hydrogen embrittlement

HYDROGEN EMBRITTLEMENTHYDROGEN EMBRITTLEMENT

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T 200°C Hydrogen embrittlement

T 200°C Hydrogen attack

Important parameter : THE TEMPERATURE

HYDROGEN EMBRITTLEMENTHYDROGEN EMBRITTLEMENT

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GASEOUS HYDROGEN EMBRITTLEMENTGASEOUS HYDROGEN EMBRITTLEMENT(G H E)(G H E)

Reversible phenomena

Transport of H2 by the dislocations

H2 TRAPS – CRITICAL CONCENTRATION

AND DECOHESION

ENERGY

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(GHE) – DIFFERENT TYPES OF TEST (GHE) – DIFFERENT TYPES OF TEST METHODS (1)METHODS (1)

Static (delayed rupture test)

Dynamic

Constant strain rate

Fatigue

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(GHE) – DIFFERENT TYPES OF TEST (GHE) – DIFFERENT TYPES OF TEST METHODS (2)METHODS (2)

Fracture mechanic (CT, WOL, …) Tensile test Disk test Other mechanical test (semi-finished

products) Test methods to evaluate hydrogen

permeation and trapping

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Specimens for compact tension test

(GHE) – DIFFERENT TYPES OF TEST (GHE) – DIFFERENT TYPES OF TEST METHODS (3)METHODS (3)

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Can also be performed with specimens cathodically charged and with tensile specimens in a high pressure cell

(GHE) – DIFFERENT TYPES OF TEST (GHE) – DIFFERENT TYPES OF TEST METHODS (4)METHODS (4)

Tensile specimens for hydrogen tests

(hollow tensile specimen)

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I = (% RAN - % RAH) / % RAN

I = Embrittlement index

RAN = Reduction of area without H2

RAH = Reduction of area without H2

(GHE) – DIFFERENT TYPES OF TEST (GHE) – DIFFERENT TYPES OF TEST METHODS (5)METHODS (5)

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Disk testing method – Rupture cell for embedded disk-specimen

(GHE) – DIFFERENT TYPES OF TEST (GHE) – DIFFERENT TYPES OF TEST METHODS (6)METHODS (6)

1. Upper flange2. Bolt Hole3. High-strength steel ring4. Disk5. O-ring6. Lower flange7. Gas inlet

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EXAMPLE OF A DISK RUPTURE TEST EXAMPLE OF A DISK RUPTURE TEST CURVECURVE

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DISK TEST – EMBRITTLEMENT INDEXDISK TEST – EMBRITTLEMENT INDEX

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Hydrogen embrittlement indexes (I) of reference materials versus maximum wall stresses (m) of

the corresponding pressure vessels

m (MPa)

I

Thin wall cylindersThin wall cylinders

Thick wall cylindersThick wall cylinders

(Good H2 behaviour)(Bad H2 behaviour)

DISK TEST – EMBRITTLEMENT INDEXDISK TEST – EMBRITTLEMENT INDEX

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Fatigue test - Principle

DISK TEST – EMBRITTLEMENT INDEXDISK TEST – EMBRITTLEMENT INDEX

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Fatigue test - Pressure cycle

DISK TEST – EMBRITTLEMENT INDEXDISK TEST – EMBRITTLEMENT INDEX

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0

1

2

3

4

5

6

4 5 6 7 8 9 10 11 12 13

Delta P (MPa)

Cr-Mo STEEL

Pure H2 H2 + 300 ppm O2

F 0,07 Hertz

2

2

nH

nN

FATIGUE TESTS, VERSUS FATIGUE TESTS, VERSUS P CURVES P CURVES nN2

nH2

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Fatigue test Principle to detect fatigue crack initiation

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TESTS CHARACTERISTICSTESTS CHARACTERISTICSType of hydrogen embrittlement and Type of hydrogen embrittlement and transport modetransport mode

TESTSLOCATION OF

HYDROGENTRANSPORT MODE

Disk rupture test External Dislocations

F % test External + Internal Diffusion + Dislocation

Hollow tensile specimen test

External Dislocations

Fracture mechanics tests

External Dislocations

P.E.S. test External Dislocations

Tubular specimen test

External Dislocations

Cathodic charging test

External Diffusion

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TESTS CHARACTERISTICSTESTS CHARACTERISTICSPractical point of viewPractical point of view

TESTSSPECIMEN

(Size-complexity)

CELL

(Size-complexity)

COMPLEMENTARY

EQUIPMENT NEEDED

Disk rupture testSmall size and very simple

Small size and very simple

Hydrogen compressor and high pressure vessel

Tensile testRelatively small size

Large size Tensile machine

Fracture mechanics test

Relatively large size and complex

Very large size and complex

Fatigue tensile machine for fatigue test only

P.E.S. testAverage size and very easy to take from a pipeline

Average size --

Tubular specimen test

Large size and complex

No cell necessaryLarge hydrogen source at high pressure

Cathodic charging test

Small size and simple

Small size and very simple

Electrochemical equipment (potentiostat)

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TESTS CHARACTERISTICSTESTS CHARACTERISTICSType of hydrogen embrittlement and Type of hydrogen embrittlement and transport modetransport mode

TESTSTESTS

SENSIBILITY

HYDROGEN BEHAVIOR OF MATERIALS –

POSSIBILITY OF CLASSIFICATION

SELECTION OF MATERIALS –

EXISTING CRITERIA

PRACTICAL DATA TO

PREDICT IN SERVICE

PERFORMANCE

Disk rupture High sensitivity Possible

Yes

PHe/PH2 Fatigue life

Tensile testGood/Poor sensitivity

Possible/Difficult Yes/No Treshold stress

Fracture mechanics

Good sensitivity

PossibleNo, but maximum

allowable KIH could be defined

- KIH

- Crack growth rate

P.E.S. test Poor sensitivity Difficult No

Tubular

specimen testGood

sensitivityDifficult No - KIH

Cathodic

chargingGood

sensitivityPossible but

difficult in practiceNo

Critical hydrogen concentration

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MAIN CHARACTERISTICS AND EMBRITTLEMENT INDEXES (E.I.)

N°AISI

GRADEE.I.

D*

(%)

Ni.eq.

(%)MS(°C)

y.s.

(MPa)u.t.s. (MPa)

1

2

3

4

5

6

7

9

13

14

16

17

18

321

304

304 L

316 Ti

204 LN

304

316 L

321

321

301 LN

316 LN

321

304 L

3.9

2.6

1.25

1.3

4.94

2.13

1.29

3.77

5.18

4.55

1.36

2.2

1.2

- 1.8

- 2.2

- 1

+ 1.5

- 4

- 1

+ 1.1

- 1.9

- 2.2

- 4.2

+ 0.6

- 0.4

+ 0.05

12

37

60

> 100

5

30

> 100

10

2

14

> 100

30

10.25

9.545

10.025

13.25

8.195

10.97

12.88

10.395

9.725

8.11

12.585

12.11

12.055

- 135

- 168

- 150

- 258

- 232

- 189

- 286

94

- 129

- 224

- 395

- 173

- 248

280

301

258

299

585

343

278

254

273

361

368

264

680

698

618

956

931

666

610

640

708

794

703

620

583

*D : Deformation necessary at 20°C to initiate 1 % of martensite formation

TEST RESULTSTEST RESULTS

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EFFECT OF STEEL STABILITY (EFFECT OF STEEL STABILITY () ON) ONTHE EMBRITTLEMENT INDEX (E.I.)THE EMBRITTLEMENT INDEX (E.I.)

0

1

2

3

4

5

6

-5 -4 -3 -2 -1 0 1 2

= Ni + 0.5 Mn + 35 C – 0.0833[Cr + 1.5 Mo – 20]2 -12

E.I.

204 LN 321

301 LN 321 321

304 304

321

304 L 304 L

316 L

316 L

316 Ti

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EFFECT OF MARTENSITE FORMED AT LOW EFFECT OF MARTENSITE FORMED AT LOW TEMPERATURE AND CHEMICAL COMPOSITIONTEMPERATURE AND CHEMICAL COMPOSITION

EFFECT OF MARTENSITE FORMED AT LOW TEMPERATURE

STEEL No

AISI GRADE E.I. E.I. (20 % Ms)*

3

7

18

304

316 L

304 L

1.25

1.29

1.2

3.83

1.71

3.5

* Embrittlement index after cold working at – 196°C so as to form 20 % martensite in the austenitic structure

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TEST RESULTS FOR A 1.4057 (x 7 CrNi 16-2)TEST RESULTS FOR A 1.4057 (x 7 CrNi 16-2)STEEL (HV STEEL (HV ~~ 500 HV) 500 HV)

Pressure increase rate (bar/min)

0

1

2

3

4

0,001

0,01 0,1 1 10 100 Pressure increase rate (bar/min)

PH

e/P

H2

0

100

200

300

400

500

600

700

0,001

0,01 0,1 1 10 100

Burst under He

Burst under H2

Bu

rst

pre

ssu

re (

bar

)

Embrittlement index

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SELECTION OF MATERIALS FOR FUELLINGSELECTION OF MATERIALS FOR FUELLINGCONNECTORSCONNECTORS

Hydrogen compatible materials for parts exposed to high pressure hydrogen

Non hydrogen compatible materials only for :

Material not exposed to hydrogen Material used at a low enough stress If a risk analysis shows that the failure has

no consequence on the safe use If the connector is only used for a short

period (to be checked by fatigue test)

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CONCLUSIONCONCLUSION

The fuelling connector is a critical part for thedispensing line

This equipment is exposed during service tovery severe conditions

We have indicated how to select the right materials (test methods and design considerations)