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There are several levels of documents which can be used to assist with the design, sizing, selection, and installation of the pressure relief device settings for LH2 tanks.
Pressure vessel design codes, such as the ASME Boiler and Pressure Vessel Code will provide minimum requirements for design of pressure vessels (including LH2 tanks), relief devices, and relief systems. However…
Safety codes globally have a requirement to provide a positive means to isolate energy sources and hazardous substances prior to performing maintenance. For gaseous hydrogen systems, methods such as a blind flange, a double block valve arrangement or a double block and bleed valve arrangement can provide that positive isolation.
Installing a blind flange requires breaking the supply line…
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…
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…
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…
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.
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…
In the U.S., there is no specific national requirement for fuel cell test equipment to be certified. There may be requirements from the local authority having jurisdiction (AHJ). Local building codes will likely point to compliance with NFPA 2/55 for the hydrogen and other gas supply systems, ASME Boiler and Pressure Vessel Code for vessels, ASME B31 piping codes for piping, and National…
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…
Purging of vent systems is not required and in most instances is not recommended.
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…
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