Yohsuke Tamura, Koji Yamazaki, Kiyotaka Maeda and Kenji Sato INTERNATIONAL CONFERENCE ON HYDROGEN SAFETY September, 11-13 2017 - Hamburg (Germany) ID 104 The residual strength of automotive hydrogen cylinders after exposure to flames Yohsuke Tamura, Koji Yamazaki, Kiyotaka Maeda　and Kenji Sato （JARI，Toho Univ.)

Contents Back ground and purpose Structure of cylinder Safety requirement for the handing of cylinder exposed to fire Test method and test condition Results Temperature and Internal pressure during fire Appearance of cylinders after exposure to flames The residual strength of cylinders after exposure to flames Consideration Summary

Structure and type of automotive CFRP cylinders TPRD Type Ⅲ： aluminum alloy Type Ⅳ： plastic Liner 　　CFRP Carbon fiber Matrix resin

About TPRD (Thermal Pressure Relief Device) Gas CFRP　cylinder To prevent the rupture of the cylinder, TPRD attached on the CFRP composite cylinder, was activated by the heat of fire.

Safety requirement for the handing of cylinder exposed to fire TPRD CFRP cylinder When the fire is extinguished before TPRD is activated, the high-pressure gas is left inside the cylinder damaged by fire. For the safe handling of such a cylinder, it is necessary that despite damage by fire the cylinder retain sufficient strength for withstanding the internal gas pressure.

In this study Using the cylinder without the TPRD in order to assuming the worst condition that the TPRD did not activate, residual strengths of the cylinders after burning that overheated to just before rupture or leakage were examined.

Test method Rupture conditions at a constant buring fire Pressure Temp. Rupture conditions at a constant buring fire (temperature, pressure, time, etc.) Water Pressure Temp. Natural cooling Hydraulic burst test Sample cylinders cut off the fire source and cooling (water or natural cooling) just before rupture. These cylinders examine the bursting pressure by the hydraulic burst test.

Test condition Test cylinder： 　Total of five types (20~70MPa　Type Ⅲ, Type Ⅳ) Filling pressure : 　Workling pressure、 Half of the working pressure

Fire exposure conditions 　Burner Measure point of temp. . 　Firepower is controlled to 600~800 °C　at 25mm from the cylinder bottom 　Engulfing fire、Localized fire exposured a half of the cylinder

Result -Flame and cylinder temp., Internal pressure

Result -Flame and cylinder temp., Internal pressure

Result -Flame and cylinder temp., Internal pressure

Internal pressure during fire expose and cooling Burst pressure during fire Case: 70MPa TypeⅣ cylinder, Filling 70MPa, Engulfing fire Supply of heat per unit time was the same condition. These had provided the cylinders with the maximum possible exposure to flames.

Situation of flame expose test 35MPa TypeⅢ　Natural cooling　

The appearance of a cylinder after exposure to flames Case: 35MPa TypeⅢ cylinder, Filling 35MPa, Engulfing fire Water cooling Natural　cooling

Hydraulic burst test

Burst pressure after extinguishment of a fire Cylinder Flame exposure conditions Filling pressure Cooling condition Burst pressure　after extinguishment of a fire Burst pressure/　Filling pressure Burst pressure/　Burst pressure of new cylinder 20MPa TypeⅢ Engulfing fire 20MPa Water　cooling more 84.2MPa more 4.21 0.92 Natural cooling more 84.7MPa more 4.24 Localized fire Water cooling 82.7MPa 4.14 0.89 25MPa TypeⅣ 25MPa 77.5MPa 3.1 0.63 79.8MPa 3.19 0.65 35MPa TypeⅢ 35MPa 111.1MPa 3.17 0.90 73.3MPa 2.09 0.60 70MPa TypeⅣ 70MPa 188.4MPa 2.69 1.00 187.9MPa 2.68 173.4MPa 4.95 0.94 TypeⅢ 197.5MPa 2.82 0.87 193.0MPa 5.51 0.85

Extinguished after the CFRP layer after extinguishment of a fire Layer of outside side were damaged by heat decomposition of matrix resin.

Heat characteristics of CFRP Strength during heating (fire) is reduced more than the glass transition temperature Tg. Strength after cooling (extinguished) is restored less than the heating resin loss start temperature Te. Tg<Te Reference : A. P. Mouritz(2006), Atsushi Sumida(2008)

Restore strength of CFRP Image diagram of temperature and stress change in the cylinder after fire during flame exposure Restore strength of CFRP Reduction of load accompanying decrease of internal pressure The strength of the CFRP cylinder after extinguished is higher than that during fire, has the strength to withstand the filling pressure

Summary To examine the handling of the CFRP cylinder after extinguished, CFRP cylinders without pressure relief device were exposed to a fire to the verge of bursting; then after the fire was extinguished the residual burst strengths was examined. The results indicated that these cylinders had a residual strength at least twice their internal gas pressures. Therefore, we consider that the burnout of cylinder will has the strength to withstand the pressure of the filling gas.

Thank you for your attention． This study introduces one of the achievements of the “technology development project for hydrogen production, transport and storage systems” commissioned by New Energy and Industrial Technology Development Organization (NEDO) in Japan.