Typical practice for gaseous tube trailers is to vent relief devices independently to the top of the vehicle. This is primarily to accommodate the large flowrates and high thrust forces involved from these releases. It’s fairly easy to do this since the vent lines are fairly short due to the maximum road height of trailers. Regulations do not prohibit piping multiple devices into a
single…
A vent system should still be installed in case the flare system does not remain ignited.
This may be able to be accomplished as a method for ignition. We have not seen it.
As flaring is not usually recommended, especially when timing is an issue, a sparker that takes time to ignite would not be recommended.
Yes, small flowrate vents may be invisible, particularly in daylight. Sometimes it may still be possible to see heat striations in the air from the heat generated by the fire, but it can be difficult to discern at low flowrates.
Plugging is a concern before, during, and after a release. Prior to the release, water may accumulate in the vent system from weather conditions (rain, snow, etc.) or from condensation, particularly if there is intermittent flow which causes the stack to get cold. This water can freeze due to ambient conditions prior to a release, thereby blocking the stack. It is also possible for
other…
The potential of an explosive atmosphere is inherent with any vent system and must be addressed through adequate design. Purging for most vent stacks is impractical due to availability or cost. In addition, and particularly for LH2 systems, the purge gas can cause potential safety issues. The primary way that explosive atmospheres are addressed is through ensuring that the design of the vent…
Yes, and this is frequently done. A redundant vent stack might have its own independent redundant relief devices, or it may take the form of a secondary stack attached to the same devices. When a secondary vent stack is installed in parallel using the same relief devices, there often will be a means to isolate the second stack, such as a rupture disc, from the first except in
emergencies.…
Absolutely. Vent systems will experience a variety of transient conditions of pressure, temperature, and thrust load, so stress analysis to anticipate the strength and flexibility needed are important for safe design. These issues are often overlooked and only become an issue when they are called upon to operate in emergencies.
It is a best practice to include the vent system in…
We would not open the vent system to inspect the internal piping without a good reason.
It is recommended to check for water in the vent stack trap
CGA G-5.5 provides several options for vent stack outlets but not all options, nor does it tell when one outlet type is better than another design.
Figure 7, is one design, but in my opinion, not the best design. For instance, for warm gas, typical no-flow, normal scenarios (like a rupture disc on a vent system), Figure 5, a capped vent pipe is the simplest.
My preference depending…
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