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Yes, these would be ignitable mixtures. In this case, it does not appear complicated geometry is involved, so 1200 psig pipe should be more than adequate to protect against internal deflagration. The most likely scenario is a "backfire," similar to a car, where ignition occurs too soon and shoots out the open end of the pipe. Consider using an inline deflagration flash arrestor on the…
The HSP recommends against the use of glycols for pressure tests due to the difficulty of adequately removing all glycol that might be left in a system after a hydrotest. The HSP recommends a pneumatic test at 110% of the system maximum allowable working pressure (MAWP), which is acceptable by code. Due to an increased danger with pneumatics vs hydrotesting, establish a pressure test zone for…
The Panel recommends performing a pressure test at 110% of design pressure. This requirement should be applied to all systems regardless of construction type since the intent is to ensure pressure integrity and proper installation. All fitting types have modes of failure during installation. For example, there are numerous examples where compression fittings have had ferrules installed…
Double pipes can be used in certain circumstances to reduce the likelihood of external leaks and increase
the likelihood of detection by monitoring the space between the two pipes. Vacuum jacketed piping is
double walled and is used in liquid hydrogen service to provide insulation. While not equipped with gas
detection in the annular space, loss of vacuum is used to indicate an…
The primary safety standards for applicable to this piping in the U.S. are ASME B31.3, B31.12, and NFPA 2. The editions used should be those adopted by the local jurisdiction. Design of an LH2 piping system should always be conducted and reviewed by engineers experienced in cryogenic piping design. The equipment should also be installed per NFPA 2 and NFPA 55. IT is recommended that the piping…
There are two parts for such a system to be effective. First, the system would have to activate quickly enough to establish a water mist throughout the region of interest (i.e., region occupied by a flammable gas mixture) before it could be ignited. This is challenging in terms of timing, and the impact of spraying water inside an enclosure filled with equipment not designed to get wet can be…
Explosion testing with hydrogen should be utilized only where there is not an established alternative and then only by personnel experienced in such testing.
Testing with hydrogen is always a challenge and needs to be approached carefully due to significant differences in properties between hydrogen and propane. Hydrogen can develop significantly higher overpressures and preliminary…
The Panel has not received such inquiries. Section 14.2 of NFPA 69 Standard for Explosion Prevention Systems covers foam and mesh requirements. NFPA 69 states in 14.3.4 that the tests shall be conducted with a flammable gas/air mixture with a fundamental burning velocity representative of the burning velocities of flammable vapors expected in the intended applications.
I am communicating with a company that is exploring this technology for an application involving a mixture of flammable gases, including hydrogen.
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