18.08.2005Helfried Rybin 1 AUTOMOBILENTWICKLUNG / ENGINEERING Safety Demands for Automotive Hydrogen Storage Systems Helfried Rybin

18.08.2005 Helfried Rybin 1

ww

w.m

agn

aste

yr.c

om

AUTOMOBILENTWICKLUNG / ENGINEERINGAUTOMOBILENTWICKLUNG / ENGINEERING

Safety Demands for Automotive Hydrogen Storage Systems

Helfried Rybin

Risk Management

E-Mail: [email protected]


ww

w.m

agn

aste

yr.c

om


Content

• Introduction

• Demands for design and reliability

• Methods to minimize risks of

design failures

• Validation

• Summary and outlook


ww

w.m

agn

aste

yr.c

om


Safety demands for automotive hydrogen storage systems

Future hydrogen powered vehicles operated by not specially trained people

• Fuel storage systems for vehicles require a fail-safe design strategy

• Materials and accessories used shall be compatible with hydrogen

Source: BMW Group / Munich, Germany Source: BMW Group / Munich, Germany


ww

w.m

agn

aste

yr.c

om


Fail-safe design strategy for liquid hydrogen fuel tanks

Design

Redundant systems for safety, i.e. if one system fails, another system has to secure the hydrogen fuel tank

This philosophy is reflected by the following regulation and standards:

• Draft UN ECE Regulation revision 14 and 14 add. 1

• keeping the probability of critical failures at an acceptable level

• risk of hydrogen powered vehicles may not exceed the risk of conventional vehicles

• Draft ISO 13985 Liquid Hydrogen – Land vehicle fuel tanks


ww

w.m

agn

aste

yr.c

om



Reliability

System reliability is statistically proven over the complete life cycle

Criteria for this reliability are reflected in:

IEC 61508: Functional safety of electrical/electronic/programmable electronic safety-related systems

• about functional safety of safety-related systems

• looks at the whole safety life cycle

• classification into safety integrity levels


ww

w.m

agn

aste

yr.c

om



9. Safety related

Systems

Realising

10. Safety systems of

other technologies

Realising

11. External equipment for risk minimizing

Realising

16. Total modification and total retrofitting

15. Shut down and de-installation

13. Total safety validation

14. Total life cycle use and maintenance

12. Total installation and total start up

1. Concept

2. Definition of the whole application range

3. Risc analysis

4. Safety requirements

5. Assignments of the safety requirements

Overall planning

6. Planning and design of the total life cycle use and mainten-

ance

7. Planning and design of the total

safety valitation

8. Planning

and design of the In-stallation and total start up

Requirements and concept

Realisation

Operation and Maintenance

Safety life cycle


ww

w.m

agn

aste

yr.c

om


Methods to minimize risks of failures in an early design phase

Failure mode and effect analysis (FMEA)

• is an instrument for avoiding risks and for reducing cost for development and manufacturing of products

• researches the design for possible failures due to initiate activities to avoid or reduce the risk of this failure

• is a method which promotes the interdisciplinary team work at an early stage

• delivers a documented expertise


ww

w.m

agn

aste

yr.c

om


Lifetime estimation by finite element analysis simulations

• pressure due to vaporizing hydrogen

• expansion of materials during thermal cycling

• external loads due to mechanical vibrations

• fatigue oriented analysis of stress-time histories

• includes both physical tests and simulations

• illustrative animations of the deformation behaviour and the resulting stresses

• damage distribution of the cutting plane

Stress plot of the support structure

Rainflow AnalysisRainflow Analysis

Methods to minimize risks of failures in an early design phase

Rain flow Analysis


ww

w.m

agn

aste

yr.c

om



1 Outer jacket2 Inner tank3 Refueling coupling4 Inner tank heater5 Cooling water heat exchanger6 Pressure control valve7 Shut-off valve8 Boil-off valve9 Pressure relief valves10 Cryogenic inlet valve11 Cryogenic outlet valve12 Hydrogen pipes13 Liquid level system14 Electronics

1

12

10

2

3 13

14

8,9

11

7

6

4

5

1 Outer jacket2 Inner tank3 Refueling coupling4 Inner tank heater5 Cooling water heat exchanger6 Pressure control valve7 Shut-off valve8 Boil-off valve9 Pressure relief valves10 Cryogenic inlet valve11 Cryogenic outlet valve12 Hydrogen pipes13 Liquid level system14 Electronics

1

12

10

2

3 13

14

8,9

11

7

6

4

5


ww

w.m

agn

aste

yr.c

om


Functional tests

The basic test program includes:

• verification of valves and sensors at their operating temperatures

• leak rate measurement

• verification of the time for refuelling

• validation of the liquid level indication

• quality of the thermal insulation

Non-destructive functional testing on a liquid hydrogen test bench:


ww

w.m

agn

aste

yr.c

om


Testing of the MLI for flammability

• Reason of this test:

• Loss of vacuum causes an condensation of oxygen atmosphere with liquid oxygen in the vacuum space

• Risk of an explosion The MLI must not be flammable to avoid a fire accident

• Impact test:

• mixture of liquid nitrogen and liquid oxygen with minimum 50% liquid oxygen

• The impact energy of 79 J/cm² must not cause an ignition of the MLI

• 20 samples are required

Destructive tests


ww

w.m

agn

aste

yr.c

om


Crash and skid test

Destructive tests Dynamic vibration test

• Statistic values for estimating the lifetime behaviour

• Inner tank:

• at ambient temperature

• at cryogenic temperature (filled with liquid hydrogen)

In order to examine the:

• connection between body and liquid hydrogen fuel tank

• the suspension of the inner tank at high external loads

Source: BMW Group / Munich, Germany


ww

w.m

agn

aste

yr.c

om


Vacuum loss test

Destructive tests

Bonfire test

Proves the design of the pressure relief devices in case of a degraded thermal insulation.

Following points are observed:

• tank pressure and temperatures

• hydrogen blow-off behaviour

• hydrogen blow-off time

The average temperature in the space 10 mm below the fuel tank shall be at least 863 K

Thermal autonomy of the liquid hydrogen fuel tank shall be at least5 minutes

Verification of the design of the pressure relief devices

Source: Energie Technologie GmbH / Munich, Germany Source: BAM / Berlin, Germany


ww

w.m

agn

aste

yr.c

om



Summary

• Fuel storage systems for vehicles require a fail-safe design strategy

• Methods to minimize risks of design failures in an early design phase

• FMEA

• Lifetime estimation by use of finite element analysis

• Non-destructive and destructive tests for verification of the fuel system

Outlook

• to inspire public confidence in this new technology

• decrease costs by the standardization of legal requirements for hydrogen internationally


ww

w.m

agn

aste

yr.c

om



Thank you for your

attention

Helfried Rybin

Risk Management

E-Mail: [email protected]

Documents

18.08.2005Helfried Rybin 1 AUTOMOBILENTWICKLUNG / ENGINEERING Safety Demands for Automotive Hydrogen Storage Systems Helfried Rybin