JAUE2012-038: Research on the capacity to endure pressure and airtightness of gas pipes through a common duct towards construction of urban infrastructure using hydrogen

Abstract

When the gas pipeline is installed in the enclosed space like a common duct, explosion-proof of electrical equipment is required to endure explosion of the leakage gas from the gas pipeline. Besides, a gas pipeline in the common duct must be surrounded by a barrier in order to avoid leaking the gas into other space. The example of such a common duct is very few in Japan now, because of high cost for the barrier.
In this research, the double piping system intended using for hydrogen gas supply through the common duct in Tsukuba city is proposed for saving the cost, and tests of pressure and airtightness of the double piping system were conducted. The double piping system is composed of the inner pipe made of polyethylene in which hydrogen gas flows and the outer pipe made of polyvinyl chloride for preventing the leakage gas of the inner pipe from leaking to outer space. And the using gas in these tests was helium gas in this time. As a result, remarkable gas leak was not recognized in a test of enduring pressure of 250kPa for 20 minutes, tests of the airtightness with 22kPa for 17.5 hours and 50kPa for 20.5 hours. Therefore, it is concluded that the capacity of enduring pressure and airtightness of the PE pipe is enough for hydrogen supply in usual.
Moreover, two experiments on the method of early detection of gas leak in the outer pipe by a natural ventilation system and a judgment system with sound velocity were conducted. As a result, the natural ventilation system was not effective in early detection. However it is considered that the judgment system with sound velocity was effective because of observing clear change of the mean sound velocity in the mixing gas of air and helium.