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Thursday, August 21, 2014

Ball Valves Handle the High Pressure, High Stakes of Hydrogen

Hydrogen fuel cell vehicles are currently undergoing testing in Japan and Germany, with commercial rollout as early as 2015. To power these environmentally friendly autos, Japan plans to install 100 hydrogen fueling stations by 2015 and 1,000 by 2025, while Germany plans to have 137 such stations in place by 2015 and 1,000 by 2020. The United States and South Korea are also planning large-scale installations of fueling stations.

With demanding performance required of valves that handle high-pressure hydrogen, Kitz Corp., based in Chiba, Japan, and its subsidiaries and development partners Perrin GmbH, based in Nidderau, Germany, and Kitz SCT, in Tokyo, are eyeing this niche market, estimated at around $25.5 million in 2015 and $38.3 million in 2020.

Kitz is targeting to have a 30 percent share of this market in 2015, and 45 percent in 2020 with an array of flow control valves, including ball, needle and check valves, dedicated to the task of safe hydrogen handling.

Kitz’s new CLESTEC series of ball valves that control the final delivery of high-pressure hydrogen (at 70 MPa) from the fueling station to the vehicle tank represent a major technological advance, according to the company, in that they are guaranteed for 40,000 filling cycles, which should be sufficient for years of service before maintenance is required. Further, Kitz is currently working on developing a ball valve that is capable of doubling that service span — 80,000 filling cycles.

Traditional ball valves suffer reliability issues when tasked with handling high-pressure hydrogen at 70 MPa, according to Kitz, and their use to date at hydrogen fueling stations has been minimal on the account of high maintenance requirements.

 

Kitz offers manual and automatic (pneumatic) options in its valves for hydrogen fueling stations for fuel cell vehicles.

 

Kitz’s hydrogen filling valves are rated at 98 MPa, in comparison to 33 MPa for compressed natural gas ball valves. The high pressure is required in order to pack as much ultra-lightweight hydrogen fuel into the vehicle’s tank as possible, but this places performance demands on the valves.

Kitz’s development of the high-pressure-hydrogen ball valve brings a number of advantages versus needle valves and traditional ball valves. First, the ball valve’s Cv (flow coefficient) of 2.1 (9/16 in, 40,000 psi) is around tenfold that of a needle valve, meaning that the fuel cell vehicle can be filled twice as fast. Second, actuation is faster compared with a needle valve; Kitz says needle valves are more suited for application as main valves in hydrogen storage tanks, where the slower actuation is not as much of an issue because they remain open for extended periods.

Further, adoption of a metal seated structure coated with diamond-like carbon in the trunnion-mounted ball valve delivers superior sealing properties, as well as excellent high-speed gas flow properties.

Kitz offers manual ball valve and automatic (pneumatic) options for its hydrogen filling valves. A spring return actuator is employed for shutoff valve applications. The valves were developed as part of a New Energy and Industrial Technology Development Organization (NEDO) project sponsored by the Japanese government.

Needless to say, a material of construction with high resistance to hydrogen corrosion is also employed in the valve, in this case STH 2 stainless steel from Nippon Steel and SUS316 stainless steel with a nickel content of at least 12 percent.

Use of correct materials is paramount to the safety of hydrogen fueling stations, as AC Transit in Oakland, Calif., found out when an incorrect pressure release valve was used at its new $10 million hydrogen fueling station in Emeryville, Calif., resulting in a fire and evacuation, as reported by the San Jose Mercury News. According to the paper, eight months after the fueling station opened as a model to boost the use and viability of fuel-cell-powered buses, the valve failed, leaking hydrogen into the air that caught fire, exploded and then burned for two hours.

Sandia National Laboratories investigators released a 33-page report that stated the type of hard steel known to crack and fail when exposed to hydrogen was used and that “proper material selection would have prevented this incident.”

 

 

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