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…
This is a fairly common arrangement and can be acceptable if properly designed. Some considerations:
Such a compressor should NOT be used for hydrogen. There are many issues with converting a compressor to hydrogen service. First and most important, this must be approved by the manufacturer. Examples of concerns for a non-hydrogen compressor used for hydrogen service include (but are not limited to):
Refineries and large petrochemical plants will frequently have flare systems for H2 and other flammable materials. One of the major purposes of these flare systems is to prevent a large unignited cloud from forming since that could result in an explosion hazard and large deflagration overpressures if there is a delayed ignition. However, these are in large facilities which have the…
As is mentioned in the question, it should always be assumed that vent stack fires will occur. The vent stack must be designed to withstand a possible deflagration and the heat from a continuous vent stack fire. The stack should also have sufficient height and be located such that thermal radiation is safe for surrounding personnel, equipment, and buildings. The codes and standards have…
The water vapor cloud formed from venting cold hydrogen gas from a liquid hydrogen tank will vary in size depending upon atmospheric conditions including ambient temperature and humidity. There is not a direct relationship between the water vapor cloud and the flammable could of hydrogen, but it’s often used as a proxy.
Initially upon release, it is possible that H2 vapor from…
It is not, but the vent stack design outlet is based on radiant heat exposure.
An annual inspection of safety devices is recommended. Testing requirements will be based on the type of device and a quantified risk analysis. Typical replacement or function testing of relief valves is between 5 and 10 years depending on the application within the industrial gas industry. Rupture discs are not tested but are frequently replaced on an interval based on manufacturer…
Yes, although not as common as high-pressure gas releases, high-velocity cold H2 gas has ignited during rupture disc and relief valve activation.
A pressure gauge is not usually provided, as one set of devices (safety valve and rupture disc) is always online by design. If the diverter valve connecting the two sets of relief devices is in the center position, both sets are online although depending upon the design of the diverter valve, it might not allow full flow in either direction. For the secondary stack with a rupture disc and a…
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