Study of potential leakage on several stressed fittings for hydrogen pressures up to 700 bar - PowerPoint PPT Presentation


Title: Study of potential leakage on several stressed fittings for hydrogen pressures up to 700 bar


1
Study of potentialleakage on severalstressed
fittingsfor hydrogen pressuresup to 700 bar
ICHS4 2011 September, San Francisco
D Houssin-Agbomson1, D Jamois2, Ch Proust2, J
Daubech2, S Ruban1, S Jallais1 sidonie.ruban_at_airl
iquide.com
1 Air Liquide, Centre de Recherche
Claude-Delorme, 78350 Les Loges-en-Josas,
France 2 INERIS, 60550 Verneuil-en-Halatte,
France
2
Content
  • Context
  • Tested configurations
  • Experimental device
  • Results
  • Conclusions and perspectives

3
I. Context
4
Study description
  • Context
  • Several H2 applications developed in "Hydrogène
    Horizon Energie" (H2E) project
  • Define "predictable" and "accidental" leaks and
    be able to assess consequences in order to
  • Design natural ventilation to avoid any dangerous
    accumulation of predictable leaks
  • Prove that an "important" leak (potentially
    inducing an explosion) has a very low probability
  • Objectives
  • Quantify "small" leaks which are probable
  • Contribute to assess the probability of
    "important" leaks
  • Means
  • H2 systems analysis by fault tree
  • Scope fittings
  • Identification of leak causes and means of
    mitigation
  • Tests for leaks
  • INERIS test bench H2, up to 700 bar, on double
    ring tube fittings and threaded ring fittings

5
II. Tested configurations
Studied fittings Stress configurations
6
Studied fittings
  • Based on a preliminary study of potentially
    leaking elements, four kinds of commercial
    fittings usually employed on H2 energy-based
    systems were chosen and tested

6-mm double ring tube fitting
Medium-pressuredouble ring tube fitting
Threaded ring tube fitting
Fittings External tube size Maximum working pressure recommended by the constructor
Swagelok double ring tube fitting(316 SS) 6 mm 420 bar
Rotarex double ring tube fitting(316 SS) 6 mm 420 bar
Swagelok medium-pressure double ring tube fitting (316 SS) 1/2 1035 bar
Maximator threaded ring tube fitting (316 SS) 9/16 1500 bar
7
Stress configurations (1/2)
  • Existing literature
  • Few results in open literature
  • Conditions already studied(1)
  • Moderate pressures ? up to 35 bar
  • Mainly 1/4'' pipe fittings
  • Main result
  • leak flow rate of 800 cm3.s-1 at 20 bar for
    tightening by hand of the fitting
  • Experimental conditions of the present study
  • H2, up to 700 bar
  • Test matrix considered as maximal stress in
    real-life conditions of a hydrogen-based
    application
  • Fatigue conditions tested beyond constructor
    tests and recommendations for users
  • Stress configurations
  • Two kinds of stresses
  • stresses applied at atmospheric pressure
    ( static tests ) assembly/dismantling cycles /
    tightening / "thermal effects"
  • stresses applied when the fitting were under
    pressure (dynamic tests) rotation / flexion /
    traction

(1) Gentilhomme, O., Tkatschenko, I., Joncquet,
G., Anselmet, F., Outcomes from the French
National Project DRIVE, Proceedings of the
Seventh International Conference and Trade Fair
on Hydrogen and Fuel Cell Technologies,22-23
October 2008, Hamburg, Germany
8
Stress configurations (2/2)
  • Details of the tested configurations

Stresses Normal conditions of use Tested stress level considered as maximum in situation
Static stresses Assembly-dismantling cycles Around 20 cycles, for 6 mm double ring tube fitting 100 cycles
Static stresses Assembly-dismantling cycles lt 20 cycles, for high pressure fittings (double and threaded ring tube fittings) 50 cycles
Static stresses Under-tightening 1 1/4 turn, for 6 mm double ring tube fitting 1 turn
Static stresses Under-tightening 1 1/4 turn, for 1/2 double ring tube fitting 3/4 turnand 1 turn
Static stresses Under-tightening 80 N.m with silicone grease on conical sealing surfaces, for 9/16 threaded ring tube fitting 60 N.m with silicone grease
Static stresses Over-tightening 1 1/4 turn, for 6 mm double ring tube fitting 1 1/2 turn
Static stresses Thermal effects 60 to -20C Crimping at 100C and leakage testat 30C
Dynamic stresses Counter-clockwise rotation 0 turn 1/8 turn compared to initial position
Dynamic stresses Flexion 0 10 from fitting initial axis
Dynamic stresses Traction 0 N 320 Nin fitting axis direction
9
III. Experimental device
Main test bench "Dynamic stress" module
10
Main test bench
  • A simple but accurate AND safe test bench
  • Characterization of H2 high pressure leaks
  • Gas for tests H2
  • Pressure range up to 700 bar
  • Sensitivity flow rate higher than 10-2 cm3.s-1
  • Main equipment
  • A H2 compressor
  • High pressure reservoirs
  • Pneumatic valves
  • Accurate pressure transducers
  • Thermocouples

Climatic enclosure
Climatic enclosure with device for tests
Scheme of the main test bench
11
Module for "dynamic stress"
  • Characteristics
  • Module set-up in order to apply stress on
    pressurized fittings thanks to a pneumatic jack
  • Pressure range up to 700 bar
  • Tested "dynamic" stresses
  • Flexion
  • Rotation
  • Traction
  • Only applied on 6-mm tube fitting
  • "Dynamic" module
  • Main equipment a pneumatic jack (up to 320 N)
  • Inserted inside the climatic enclosure of the
    main test bench

12
IV. Results
13
Results of the study
  • Only two test configurations showed small
    leakages
  • ? leak flow rates experimentally determined
    appear close to the threshold sensitivity value
    of 10-2 cm3.s-1

Fitting Fitting External tube size Tested stress Pressure conditions Measured leakage rate
Swagelok medium-pressure double ring tube fitting 1/2 After 50 assembly-dismantling cycles 700 bar 0.05 cm3.s-1
Maximator threaded ring tube fitting 9/16 Under-tightening with silicone grease60 N.m instead of 80 N.m 700 bar 4.3 cm3.s-1
  • These values are very low compared to the flow
    rates usually considered for risk analyses of
    potentially hazardous systems (i.e. around 900
    cm3.s-1 for the "0.1 mm-200 bar" hypothesis),
  • It would be detected by normal control procedures
    particularly for these types of stresses

Leak visualisation in water
  • The other stress scenarii did not exhibit
    detectable leakage given experimental
    installation sensitivity

14
V. Conclusions and perspectives
15
Conclusions
  • A specific experimental installation was designed
    and set-up by INERIS in order to study potential
    leakages on fittings commonly used in H2 existing
    systems
  • This test bench enables
  • to accurately quantify, when existing, leakages
    with a flow rate above 10-2 cm3.s-1
  • to carry out the tests with hydrogen in safe
    conditions
  • to reach test pressures up to 700 bar
  • to apply stresses on fittings under H2 pressure
    (i.e. dynamic stresses)
  • Very few scenarios gave rise to quantifiable
    leaks (given test bench detectable thresholds)
  • Only two stress configurations showed measurable
    but low leak flow rates compared to values
    usually employed for risk assessment
  • 0.05 cm3.s-1 for the Swagelok 1/2
    medium-pressure double ring tube fitting after 50
    cycles of assembly-dismantling
  • 4.3 cm3.s-1 for a 25 under-tightening of the
    Maximator 9/16 threaded ring tube fitting
  • ? A good reliability of the fittings used in
    H2-energy based systems is shown
  • ? For hydrogen systems considered for the H2E
    project, the present leakage rates are much too
    low to produce an accumulation of a flammable
    atmosphere a leakage rate of a few tens of
    cm3.s-1 would be required

16
Perspectives
  • This study is a first step and several other
    tests can be considered
  • Determining the critical stress levels which give
    rise to significant leaks
  • Testing other stresses (e.g. vibration effects)
  • Combining different types of stress (e.g.
    under-tightening and traction)
  • Testing other potentially leaking elements of
    H2-based systems

17
Thanks foryour attention
ICHS4 2011 September, San Francisco
Study of potential leakage on several stressed
fittingsfor hydrogen pressures up to 700 bar
sidonie.ruban_at_airliquide.com
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Study of potential leakage on several stressed fittings for hydrogen pressures up to 700 bar

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Title: Study of potential leakage on several stressed fittings for hydrogen pressures up to 700 bar


1
Study of potentialleakage on severalstressed
fittingsfor hydrogen pressuresup to 700 bar
ICHS4 2011 September, San Francisco
D Houssin-Agbomson1, D Jamois2, Ch Proust2, J
Daubech2, S Ruban1, S Jallais1 sidonie.ruban_at_airl
iquide.com
1 Air Liquide, Centre de Recherche
Claude-Delorme, 78350 Les Loges-en-Josas,
France 2 INERIS, 60550 Verneuil-en-Halatte,
France
2
Content
  • Context
  • Tested configurations
  • Experimental device
  • Results
  • Conclusions and perspectives

3
I. Context
4
Study description
  • Context
  • Several H2 applications developed in "Hydrogène
    Horizon Energie" (H2E) project
  • Define "predictable" and "accidental" leaks and
    be able to assess consequences in order to
  • Design natural ventilation to avoid any dangerous
    accumulation of predictable leaks
  • Prove that an "important" leak (potentially
    inducing an explosion) has a very low probability
  • Objectives
  • Quantify "small" leaks which are probable
  • Contribute to assess the probability of
    "important" leaks
  • Means
  • H2 systems analysis by fault tree
  • Scope fittings
  • Identification of leak causes and means of
    mitigation
  • Tests for leaks
  • INERIS test bench H2, up to 700 bar, on double
    ring tube fittings and threaded ring fittings

5
II. Tested configurations
Studied fittings Stress configurations
6
Studied fittings
  • Based on a preliminary study of potentially
    leaking elements, four kinds of commercial
    fittings usually employed on H2 energy-based
    systems were chosen and tested

6-mm double ring tube fitting
Medium-pressuredouble ring tube fitting
Threaded ring tube fitting
Fittings External tube size Maximum working pressure recommended by the constructor
Swagelok double ring tube fitting(316 SS) 6 mm 420 bar
Rotarex double ring tube fitting(316 SS) 6 mm 420 bar
Swagelok medium-pressure double ring tube fitting (316 SS) 1/2 1035 bar
Maximator threaded ring tube fitting (316 SS) 9/16 1500 bar
7
Stress configurations (1/2)
  • Existing literature
  • Few results in open literature
  • Conditions already studied(1)
  • Moderate pressures ? up to 35 bar
  • Mainly 1/4'' pipe fittings
  • Main result
  • leak flow rate of 800 cm3.s-1 at 20 bar for
    tightening by hand of the fitting
  • Experimental conditions of the present study
  • H2, up to 700 bar
  • Test matrix considered as maximal stress in
    real-life conditions of a hydrogen-based
    application
  • Fatigue conditions tested beyond constructor
    tests and recommendations for users
  • Stress configurations
  • Two kinds of stresses
  • stresses applied at atmospheric pressure
    ( static tests ) assembly/dismantling cycles /
    tightening / "thermal effects"
  • stresses applied when the fitting were under
    pressure (dynamic tests) rotation / flexion /
    traction

(1) Gentilhomme, O., Tkatschenko, I., Joncquet,
G., Anselmet, F., Outcomes from the French
National Project DRIVE, Proceedings of the
Seventh International Conference and Trade Fair
on Hydrogen and Fuel Cell Technologies,22-23
October 2008, Hamburg, Germany
8
Stress configurations (2/2)
  • Details of the tested configurations

Stresses Normal conditions of use Tested stress level considered as maximum in situation
Static stresses Assembly-dismantling cycles Around 20 cycles, for 6 mm double ring tube fitting 100 cycles
Static stresses Assembly-dismantling cycles lt 20 cycles, for high pressure fittings (double and threaded ring tube fittings) 50 cycles
Static stresses Under-tightening 1 1/4 turn, for 6 mm double ring tube fitting 1 turn
Static stresses Under-tightening 1 1/4 turn, for 1/2 double ring tube fitting 3/4 turnand 1 turn
Static stresses Under-tightening 80 N.m with silicone grease on conical sealing surfaces, for 9/16 threaded ring tube fitting 60 N.m with silicone grease
Static stresses Over-tightening 1 1/4 turn, for 6 mm double ring tube fitting 1 1/2 turn
Static stresses Thermal effects 60 to -20C Crimping at 100C and leakage testat 30C
Dynamic stresses Counter-clockwise rotation 0 turn 1/8 turn compared to initial position
Dynamic stresses Flexion 0 10 from fitting initial axis
Dynamic stresses Traction 0 N 320 Nin fitting axis direction
9
III. Experimental device
Main test bench "Dynamic stress" module
10
Main test bench
  • A simple but accurate AND safe test bench
  • Characterization of H2 high pressure leaks
  • Gas for tests H2
  • Pressure range up to 700 bar
  • Sensitivity flow rate higher than 10-2 cm3.s-1
  • Main equipment
  • A H2 compressor
  • High pressure reservoirs
  • Pneumatic valves
  • Accurate pressure transducers
  • Thermocouples

Climatic enclosure
Climatic enclosure with device for tests
Scheme of the main test bench
11
Module for "dynamic stress"
  • Characteristics
  • Module set-up in order to apply stress on
    pressurized fittings thanks to a pneumatic jack
  • Pressure range up to 700 bar
  • Tested "dynamic" stresses
  • Flexion
  • Rotation
  • Traction
  • Only applied on 6-mm tube fitting
  • "Dynamic" module
  • Main equipment a pneumatic jack (up to 320 N)
  • Inserted inside the climatic enclosure of the
    main test bench

12
IV. Results
13
Results of the study
  • Only two test configurations showed small
    leakages
  • ? leak flow rates experimentally determined
    appear close to the threshold sensitivity value
    of 10-2 cm3.s-1

Fitting Fitting External tube size Tested stress Pressure conditions Measured leakage rate
Swagelok medium-pressure double ring tube fitting 1/2 After 50 assembly-dismantling cycles 700 bar 0.05 cm3.s-1
Maximator threaded ring tube fitting 9/16 Under-tightening with silicone grease60 N.m instead of 80 N.m 700 bar 4.3 cm3.s-1
  • These values are very low compared to the flow
    rates usually considered for risk analyses of
    potentially hazardous systems (i.e. around 900
    cm3.s-1 for the "0.1 mm-200 bar" hypothesis),
  • It would be detected by normal control procedures
    particularly for these types of stresses

Leak visualisation in water
  • The other stress scenarii did not exhibit
    detectable leakage given experimental
    installation sensitivity

14
V. Conclusions and perspectives
15
Conclusions
  • A specific experimental installation was designed
    and set-up by INERIS in order to study potential
    leakages on fittings commonly used in H2 existing
    systems
  • This test bench enables
  • to accurately quantify, when existing, leakages
    with a flow rate above 10-2 cm3.s-1
  • to carry out the tests with hydrogen in safe
    conditions
  • to reach test pressures up to 700 bar
  • to apply stresses on fittings under H2 pressure
    (i.e. dynamic stresses)
  • Very few scenarios gave rise to quantifiable
    leaks (given test bench detectable thresholds)
  • Only two stress configurations showed measurable
    but low leak flow rates compared to values
    usually employed for risk assessment
  • 0.05 cm3.s-1 for the Swagelok 1/2
    medium-pressure double ring tube fitting after 50
    cycles of assembly-dismantling
  • 4.3 cm3.s-1 for a 25 under-tightening of the
    Maximator 9/16 threaded ring tube fitting
  • ? A good reliability of the fittings used in
    H2-energy based systems is shown
  • ? For hydrogen systems considered for the H2E
    project, the present leakage rates are much too
    low to produce an accumulation of a flammable
    atmosphere a leakage rate of a few tens of
    cm3.s-1 would be required

16
Perspectives
  • This study is a first step and several other
    tests can be considered
  • Determining the critical stress levels which give
    rise to significant leaks
  • Testing other stresses (e.g. vibration effects)
  • Combining different types of stress (e.g.
    under-tightening and traction)
  • Testing other potentially leaking elements of
    H2-based systems

17
Thanks foryour attention
ICHS4 2011 September, San Francisco
Study of potential leakage on several stressed
fittingsfor hydrogen pressures up to 700 bar
sidonie.ruban_at_airliquide.com
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