- #1
- 72
- 0
What are the reasons (advantages) for using nitrogen when venting vacuum systems?
What are the reasons (advantages) for using nitrogen when venting vacuum systems?
1. It's cheap
2. It's readily available
3. The boil off from the liquid cylinder tends to be dry and will not cause condensation in your vacuum chamber
4. It is clean (i.e. no contamination/hydrocarbon), assuming that your venting lines and connectors are also clean.
Zz.
Common practice is to vent with dry nitrogen, e.g. boil-off from liquid, and to keep a constant flow of N2 through the chamber while you are working inside. Don't keep the chamber open any longer than necessary, and you will minimize contamination with water etc. from the ambient air. Less contamination is better than more.
There are also claims that once you've vented your chamber to dry nitrogen the surface is somehow passivated (at least partially) and will adsorb less water etc. It is not quite clear to me how this mechanism is supposed to work.
If you are going to keep your chamber open and exposed to air for a month or so you might as well vent it to air.
When venting with nitrogen from a gas cylinder be extra careful not to overpressurize the chamber as viewports cannot take a lot of internal pressure. In case of doubt always use a ballon or overpressure valve on the vent line and/or a burst disk on the actual chamber.
Don't use nitrogen if it's use is detrimental.
ie: for some processes, it poisons the stuff you're trying to make.
But you're VENTING the system! If the use of nitrogen gas "poisons" this stuff, then exposing it to air will be even worse! And that is what you are trying to do when you vent a vacuum system!
This doesn't make any sense.
Zz.
You're right, if the finished product will be exposed to air anyways. but my experience with R&D meant opening the chamber for adjustments and modifications only to continue the run later.
Nitrogen and oxygen were the two worst
What are the reasons (advantages) for using nitrogen when venting vacuum systems?
You did read the original post of this thread, didn't you?
The OP wanted to know the reason why many of us who deal with UHV systems vent out those system using N2 gas. This is a common practice in MY R&D experience, both for accelerators and for thin film fabrications of air-sensitive material. Since most, if not all, of vacuum components are made of stainless steel or aluminum or copper, those are the types of material that you have to address when you are venting it with N2 and why.
Zz.
We don't use N2 in large chambers that people enter after venting. These machines are in a large semiconductor class clean room so they are vented using normal atmosphere.Yes, I was wondering why to use N2 myself too.
I saw that you had reasonably answered the question, and that naturally begs the question of "why not to use N2"
That's the question I attempted to answer! So that others can know of alternatives, and learn from my mistakes!
(!
We don't use N2 in large chambers that people enter after venting. These machines are in a large semiconductor class clean room so they are vented using normal atmosphere.
If people enter the vessel, then venting with N2 presents a safety risk (lack of oxygen).