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A nitrogen purge is generally not needed for a vent system designed in accordance with CGA G-5.5.  However, there are times where this might be considered or required due to the specific design of a system.  Where determined by a risk review to be needed, A continuous purge into a vent system reduces the probability air or oxygen in the piping. Intermittent purging should be…

Category: Miscellaneous
Keywords: Purge, Vent, System Design, Operation, Maintenance

The UN ECE R134 regulation is a good requirement to follow as it copies the language in the UN GTR #13 regulation. The updated version of this UN document (UN GTR #13 Phase 2) is currently in approval review at the GRSP in Geneva and should be approved by the end of 2023. Nevertheless, since the US Department of Transportation’s National Highway Traffic Safety Administration is a contracting…

Category: FC Electric Vehicles
Keywords: FC Vehicles, Detection, Concentration

Because hydrogen is labeled as a hazardous substance, sometimes people are concerned about the environmental impact of releasing liquid hydrogen. There are currently no regulations that require reporting of hydrogen releases for environmental reasons.


However, there are safety implications. For example, the US DOT requires reporting of hazardous materials releases under certain…

Category: Miscellaneous
Keywords: Liquid, Spill, Ditch, Sewer, Lake, River

The end use of hydrogen usually drives the cleaning for initial construction. 

  1. When the hydrogen is used for combustion and many industrial applications, normal care during construction and leak testing is usually adequate. 
  2. When the hydrogen needs to be very pure, as is the case for PEM fuel cell applications, more…
Category: System Design
Keywords: Clean, Component, System

Requirements for local jurisdictions vary, so the AHJ should be consulted, but NFPA 2:2023, Hydrogen Technologies Code, Chapter 13 has requirements for installation of hydrogen generators up to 100 kg H2/h. Section 13.3.1 General says permitted water electrolysis systems are to be listed to ISO 22734:2019, Hydrogen Generators Using Water Electrolysis - Industrial, Commercial, and Residential…

Category: System Design
Keywords: Electrolyzer, Code, Standard, AHJ

It depends on the facility and risk assessment, but generally multiple pressure and temperatures to one vent stack is not the best practice unless all are similar in pressure and temperature, and the streams have compatible composition and flow rate. Care must also be taken to prevent reverse flow and misdirected flow between portions of the system. Additionally, one vent stack can become a…

Category: System Design
Keywords: Vent, Vent Stack, Code, Standard, System Design, Fire

The answers are in context of PEM and alkaline electrolysis operating at or below 30 bar and below 85 deg C°. A general suggestion: Ask component suppliers about material compatibility, but do an independent investigation to confirm. As a general resource,  safety data sheets (SDSs) sometimes provide material compatibility information. Specific recommendations follow. 

Category: System Design
Keywords: Electrolyzer, Materials, Oxygen, Alkaline, Water

A "drop and swap" delivery system using tube trailers is a common and accepted method of supply for both industrial and fueling station applications. While NFPA 2 - 2023, paragraph 10.6.3.5 states, "The use of hose in a hydrogen dispensing system shall be limited to vehicle fueling hose," this is intended for the dispenser itself, not the entire fueling station. This does not limit the use of…

Category: Fueling Stations
Keywords: Hose, "Drop and Swap", Tube Trailer

Many methods are used to mitigate the risk of a tube trailer hose loss of containment incident. Examples that otherwise exceed code requirements are provided below. These have been deployed in various combinations depending on the risk analysis for a particular system: 

  1. Installation of automatic shutoff valves on the tube trailer upstream of the hose to activate upon hose…
Category: Fueling Stations
Keywords: Hose, "Drop and Swap", Tube Trailer
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