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I am not sure which picture you are referring to so I will attempt to answer.

If you are referring to the incident where a fire occurred and the vent system was damaged, then this may have been due to lack of proper supports and incomplete assembly of the test systems. In the past, vent systems were not pressure tested for strength but that is changing. 

If you are talking…

Category: Miscellaneous
Keywords: Cylinder, Vent System

At NASA Cape Canaveral, they used a natural gas line connected to the vent stack outlet with a thermal sensor to make sure the pilot was lit. They may also have had a sensor to ensure the H2 fire was lit. In cases where substantial quantities of unused hydrogen is vented and the timing and amount of the flow rate is known and controlled, flaring might be useful. NASA guidelines stipulate that…

Category: Miscellaneous
Keywords: Vent Stack, Pilot Ignition, Guidelines, Flare, Purge

There is no specific requirement not to vent liquid hydrogen from a vent system. Best practice would be to only vent gas from the top of the vessel to relieve pressure. If liquid must be vented, it should be vaporized first. 

Note: It is very unusual to have LH2 flow from a liquid tank out the vent system, as the vent system is connected to the vapor space on the LH2 tanks and there…

Category: Miscellaneous
Keywords: Liquid Hydrogen, Vent, LH2, GH2

No, but it depends on the application. Nearly all vents less than 4” in size are not purged with N2. This is primarily due to: 1) large flows required to dilute hydrogen below the flammable range, 2) the cost of the nitrogen, 3) the potential blockage of the stack when being inserted a vent header/stack serving a liquid hydrogen system, 4) the potential for backpressure (depending on the…

Category: Miscellaneous
Keywords: Vent, Purge, GH2, LH2

The code used for repair and alterations of an existing system depends on the code used for construction as well as on the requirements imposed by the jurisdiction. Note that getting a permit from the jurisdiction may be necessary for an extensive alteration.

Code of ConstructionGenerally Accepted Code for Repair and Alterations…
Category: Piping
Keywords: Piping, Codes

The requirements of the code used for the original construction apply. The piping may meet the requirements of more than one code. In which case, the code used for changing the rating may be different than the original code of construction. In any case, the re-rated system should meet all of the requirements of the selected code. Note that if the original proof test of the system was…

Category: Piping
Keywords: Codes, Piping, Requirements

At least three of the ASME B31 piping codes are logical choices:

  • ASME B31.1, Power Piping
  • ASME B31.3, Process Piping
  • ASME B31.12 Hydrogen Piping and Pipelines

Considerations for code selection include:

  • Requirements imposed by the authority having jurisdiction, whether by direct reference or…
Category: Piping
Keywords: Piping, Codes, Requirements

The Panel considers two approaches to be acceptable. 

  1. Stainless steel (corrosion resistant) lines embedded in concrete. This keeps the piping out of direct contact with the earth and provides a degree of physical protection from activities such as digging. 
  2. Lines enclosed within a PVC sleeve. The PVC sleeve would usually be directly buried but could also be…
Category: Piping
Keywords: Piping, Underground, Corrosion, Physical Protection

The HSP is not familiar with this particular fitting or its potential application in H2 service but can offer engineering judgment. Many similar compression-type swaged fittings are used in H2 service. These fittings must be used within the manufacturer recommendations for pressure, temperature, and fluid service. Deformation is also introduced into stainless steel tubing in other ways, such…

Category: Piping
Keywords: Piping, Fitting, Lokring Technology, Material Selection

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…

Category: Piping
Keywords: Piping, Liquid, Safety, Vacuum, Insulated, Standards
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