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2 . The non-metallic materials in contact with hydrogen shall have good compatibility , and the applicability of the materials under hydrogen conditions shall be verified ;
3 . Influence of temperature change , material performance change under ultralow temperature conditions ;
4 . Permeation rate of hydrogen atom shall be known ;
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5 . The mechanical stability , strength , and service life of non-metallic materials shall be maintained within the full working conditions and life cycle due to the impact of hydrogen degradation .
• Valve metallic materials with special control of Cr 、 S 、 P and other elements , also higher mechanical proper-
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ties than standard such as ASTM A182 & A351 for liquid hydrogen service ; |
• Ferrite content : no more than 3 % for forgings , pipes and bars , and no more than 8 % for castings ;
• Cryogenic treatment : no less than 2 times for parts in liquid hydrogen medium ;
• Welding process qualification and special selection of welding materials .
Additional Technical Requirements for Liquid Hydrogen Valves
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• Shell test of the valve shall be able to reach 4 times the maximum allowable working pressure without leakage for 1 minute .
• The minimum fatigue life of bellow shall not be less than 10,000 times , and the corrugated pipe material shall be 316 L ;
• For valves with vacuum jacket structure , the valve shall be body extended . For gas insulation , the valve shall be bonnet extended ;
• The valves installed on mobile equipment such as tank cars shall undergo vibration and impact resistance tests ;
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• Globe valve or ball valve should be used for hydrogen pipelines ;
• Liquid hydrogen should be prevented from remaining in the valve core when the ball valve is closed ;
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• Prototype testing at the available qualified institute shall be done to make sure the valve meets the operation performance at super low temperature ;
Final Thoughts
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• Globe valve shall be installed in the liquid hydrogen return line as close to the container as possible , and there shall be no other accessories between them ;
• All additional valves shall be degreased and dried before assembly ;
• The valve shall be designed with an anti-static structure ( 4 Ω max ), and fire-safe design if needed ;
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To date , both gaseous and liquid hydrogen valves are widely applied in the hydrogen energy industry and traditional oil & gas industry . The focus on these specialty valves is continually developing along with the global incentive to use clean energy for the environment . Safety comes first and all industries should take every precaution in hydrogen service possible . Currently , API is developing code named API6Z for Hydrogen Valves . |