So- How do you get frozen moisture molecules out of the annular space of a cryogenic vessel?
And- If they are frozen, they are immobile right? So are they hurting anything?
The first answer is heat. The only simple way to get molecules freed up and moving so they can be sucked out of a cryogenic vessels annulus is by applying energy. The problem is that this must be done indirectly. More specifically, we cannot blow hot air into the annulus to free up the molecules as this just puts molecules in and can tear up the super-insulation in a SI vessel. This means that you have to apply heat to the inside of the inner vessel and possibly also to the outside of the outer vessel.
With super-insulated cryogenic liquid cylinders this is fairly easily accomplished by inserting a thermostatically controlled electric heat rod into the inner vessel. With larger vessels and cryogenic bulk tanks it is necessary to blow in filtered, hot air or pure nitrogen. This is pretty inefficient and can be expensive, but might be the only option. Heat lights or strips can also be used for heating the outer vessel.
And- If they are frozen, they are immobile right? So are they hurting anything?
The first answer is heat. The only simple way to get molecules freed up and moving so they can be sucked out of a cryogenic vessels annulus is by applying energy. The problem is that this must be done indirectly. More specifically, we cannot blow hot air into the annulus to free up the molecules as this just puts molecules in and can tear up the super-insulation in a SI vessel. This means that you have to apply heat to the inside of the inner vessel and possibly also to the outside of the outer vessel.
With super-insulated cryogenic liquid cylinders this is fairly easily accomplished by inserting a thermostatically controlled electric heat rod into the inner vessel. With larger vessels and cryogenic bulk tanks it is necessary to blow in filtered, hot air or pure nitrogen. This is pretty inefficient and can be expensive, but might be the only option. Heat lights or strips can also be used for heating the outer vessel.
In any case, it is super-critical to avoid overheating in order to stay within specifications and avoid damage or stress to the inner vessel which will weaken it. By the way- this is one more reason why there is a DOT program for inspecting and authorizing DOT-4L vessel repair facilities. And- if you want to know if your vendor is actually a DOT 4L authorized repair center just ask them for their DOT “K” number. Real prudence will prompt you to also look and make sure they are affixing their “K” tag to all serviced vessels as required.
As far as hurting anything...... next post.....
Posts
