[ safety ]
reaction forces at the top of the vent stack . Refer to the vent stack design criteria within EIGA and Compressed Gas Association ( CGA-North America ) documents for details . These stacks should be located to ensure that a hydrogen release does not harm people or damage property . Vent stack outlets should be located outdoors , typically at a minimum elevation of 3 m ( 10 ft ) for GH2 and 7.6 m ( 25 ft ) for LH2 . These elevations should be increased if roofing and adjacent buildings or structures are nearby . Refer to local codes for specific required heights and allowed locations .
Improper vent stack discharge
temperature that has nitrogen gas for purging . This scenario will likely require separate vent stacks to ensure nitrogen doesn ’ t freeze solid and plug the vent stack .
10 . Not considering liquid air or ice Oxygen-rich liquid air and ice can form on piping and supports when flowing LH2 or cold hydrogen gas from an LH2 source . The oxygen-rich liquid air can cause flammable materials ( e . g ., asphalt ) to burn or explode . Extreme cold temperatures can also damage concrete and cause embrittlement and failure of surrounding supports that are not rated for the temperature , such as carbon steel . Flowing LH2 or cold hydrogen gas from an LH2 source can result in oxygen-rich liquid air and ice forming on the piping .
9 . Incorrect vent stack termination and release flow The vent stacks should direct the flow of hydrogen upward and be designed to minimize
Other design criteria
• Grounding . To minimize ignition sources , the system ( including the vent stack ) and the delivery vehicle should be grounded .
LH2 pipe with liquid air LH2 pipe with ice
Hydrogen Tech World | Issue 7 | December 2022 37