[ safety ]
Vent system incidents
Improper design of vent systems has caused injury and death and damaged property . On 8 January 2007 , a hydrogen release killed one person and injured eight others at the Muskingum River Power Plant in Beverly , Ohio , and caused substantial damage to the facility . The incident was caused by the hydrogen vent stack failing within the building in response to a change in the direction of the hydrogen flow
Muskingum River Power Plant explosion when the safety device was activated . In 1974 in Lubbock , TX , an LH2 tank exploded when the local fire department sprayed water directly on the end of the only vent stack , plugging the stack . This destroyed the LH2 tank , injured several people , and damaged property . On 11 February 2018 , an incorrectly rated rupture disc prematurely opened , damaging the vent systems and causing a fire on the back of a hydrogen trailer at Diamond Bar , CA . During the event , the vent system piping was also pulled out of the compression fittings due to incorrect installation .
• Air ingress during a release
• Interaction between flow streams
• Liquid air or ice issues as a result of incorrect installation
• A hydrogen release adversely affecting people or property
Clearly , many potential failures for a system can be ( and often are ) overlooked in the design and PHA for a hydrogen system .
The Center for Hydrogen Safety ( CHS ), a global membership organization dedicated to promoting hydrogen safety and best practices worldwide , has had extensive discussions among its members and the
Hydrogen Safety Panel about vent design and other hydrogen safety practices . As a result of these discussions , CHS has developed a list of the top 10 considerations for designers to avoid the most common mistakes that can result in vent system failure .
1 . Overpressurization The system should be designed for a minimum pressure of 40 bar , as recommended by the European Industrial Gas Association ( EIGA )
211 / 17 , Hydrogen Vent Systems for Customer Applications . Additionally , it is a best safety practice to design the pressure rating of the piping at the highest rated pressure entering the vent system .
2 . Plugging / blocking the vent system The vent system should be designed to avoid freezing from the introduction of moisture or other obstructions ( such as insects or bird nests ). For either an LH2 or a GH2 vent stack , ensure water cannot collect in the vent stack by using a water barrier cap that will open only during required hydrogen releases . If water can collect in the vent system , such as in a cold LH2 stack interaction with humid air , provide a monitored water collection chamber at least 0.6 m ( 2 ft ) below the cold hydrogen inlet at the bottom of the vent stack and ensure that it provides enough volume to collect water from the vent , typically several gallons for small vent stacks . All piping from any relief valve or valve outlet should slope downward with no liquid collection points between the components and the vertical vent stack . Signs should be placed near the vent system directing the fire department not to
Hydrogen Tech World | Issue 7 | December 2022 35