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The recognized and generally accepted good engineering practices (RAGAGEP) for employing a purge into a hydrogen vent stack is that inerting is not generally used. Best practice is that the vent stack should be designed for a fire and the overpressure caused by an internal deflagration. This is typically not an issue for smaller sizes (less than 4”) and when using typical materials for a vent…

Category: System Design
Keywords: Helium, Nitrogen, Vent, Deflagration, Detonation

The recognized and generally accepted good engineering practices (RAGAGEP) for employing a nitrogen purge into a hydrogen vent stack is that inerting is not generally used for nitrogen purge in a hydrogen vent stack because most inert gases freeze at liquid hydrogen temperatures. The vent stack should be designed for a fire and the internal overpressure caused by a deflagration. If inerting is…

Category: System Design
Keywords: Liquid, Helium, Nitrogen, Vent, Deflagration, Detonation

Because a small spark can ignite hydrogen-air mixtures, precautions such as using spark-resistant tools is one method that can be considered to reduce the probability of an ignition. However, there is little evidence that spark-resistant tools make a significant difference.   


Spark-resistant tools are made of nonferrous materials that are inherently weaker than the steels…

Category: Miscellaneous
Keywords: Spark-resistant, Spark-proof, Non-Sparking, Tools

It depends on the construction and location of the lights. Assuming the typical practice of using non-classified lighting on vehicles, operation of those lights during a delivery could provide an ignition source if located within the classified area near the delivery or venting activity. A more modern LED lighting systems may present a lower risk.

Category: Miscellaneous
Keywords: Delivery, Ignition, Lights, Hazards, Flashing

Fuels like gasoline are exempt from OSHA process safety management (PSM) requirements. When asked about the applicability for hydrogen storage larger than 10,000 lb (4500 kg) being used as a fuel, OSHA responded with an interpretation that can be found at https://www.osha.gov/laws-regs/standardinterpretations/…

The “Hydrogen Ready Appliances Assessment Report” published by the Northwest Energy Efficiency Alliance (NEEA) in February, 2023, is one of the most recent studies on this topic.  Several key items from the report pertaining to this question include the following:

1.    “There appears to be growing consensus that blends of up to 20% or perhaps even 30% are…

Category: Properties
Keywords: Hydrogen, Blending, Appliances, Residential, Flame, Odor

Equation 6.3.1.1 in CGA S1.3 is based on modeling to API methods described in: Heitner, T. Trautmauis, and M. Morrissey, “Relieving Requirements for Gas Filled Vessels Exposed to Fire,” 1983 Proceedings-Refining Department, Volume 62, American Petroleum Institute, Washington, D.C., pp. 112-122.

This method considers the transient nature of the vessel warming in combination with the…

Category: Pressure Relief Devices
Keywords: Pressure Relief Device, Relief valve, Rupture Disc, Orifice size

API 520, Sizing, Selection, and Installation of Pressure-relieving Devices Part I - Sizing and Selection, was written for use in the process industries in gas and liquid service.

CGA S1.3, Pressure Relief Device Standards-Part 3-Stationary Storage Containers for Compressed Gases was written for fixed equipment in gas service.

Which standard to use depends on the choice by the owner…

Category: Pressure Relief Devices
Keywords: Pressure Relief Device, Relief valve, Rupture Disc, Orifice size, CGA, API

Pressure relief systems may use reclosing devices like relief valves, non-reclosing devices like rupture discs, or a combination of both in parallel. Some systems may also be equipped with emergency blowdown systems that are operated by control systems. Selection of the proper devices is dependent on the system design and relative hazards. Variables that affect the selection include the type…

Category: Pressure Relief Devices
Keywords: Pressure Relief Device, Relief valve, Rupture Disc, System Design, Installation
Category: Miscellaneous
Keywords: ignite, Static Charge, Electrolyzer, Ignition, Electrical Classification, Release, Vent Stack, Vent, atmosphere, flare, Fire, Separation Distance, flame arrestor, toroidal ring, Airfield, Pipeline, Materials, Compatibility, cast iron, Piping, Leak, Gas detector, calibration detector, portable, Outdoors, truck, attributes, set point, extinguish, Explosion, deluge, Relief, TPRD, indoors, threshold, Natural Gas, Blending, material compatibility, odorant, PRD, Pressure, mobile, Helium, Fueling Station, railroad, train, Oxygen, overpressure, Korea, composite, Tank, Cylinder, Laboratory, Odor, Fuel Cells, Conversion, delayed ignition, Jet Fire, Hazards Analysis, jacketed, barriers, Liquid, Residential, furnace, Risk, Boiling Liquid Expanding Vapor Explosion (BLEVE), emergency response, Deflagration, Detonation, training, Underground, Storage, Tube Trailer, Fueling Station, gasoline, diesel, electric charging, rupture panel, Instruments, Valves, Actuator, Procedure, Dispersion, model
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