Requirements for TPRD/PRD’s depend on the local regulations. Some jurisdictions require them, some do not. Others make them optional based on results of performance testing.
This is a complicated subject. Thermally activated pressure relief devices can be an important safeguard for hydrogen vessels if properly designed and installed in accordance with code requirement. Requirements vary globally and often depend on the type of vessel and its intended service (e.g. mobile or stationary). However, as with any device, TPRD’s offer both advantages and disadvantages.…
Relief device sizing for liquid hydrogen tanks follow recognized standards such as CGA S1.3. The sizing criteria include a worst-case scenario of an engulfing fire with loss of vacuum integrity.
LH2 tanks are unlikely to BLEVE due to the vacuum insulation outer jacket (usually carbon or stainless steel) preventing direct impingement of fire onto the main pressure vessel, as well as the…
Several organizations published a paper together on this topic in 2017 (see attached). Based on comparisons with tests and CFD simulations, the following conclusions were drawn:
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…
1. As of January 2024, we are not aware of any public data on incidents or investigations where a hydrogen fired steam boiler exploded.
2. The potential for detonations within a boiler tube would depend on both the equivalence ratio of the hydrogen present and the diameter of the boiler tube.
a. At a minimum, if the circumference of the tube is…
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