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-   -   Noob LN2, Dewar questions (http://www.madshrimps.be/vbulletin/f9/noob-ln2-dewar-questions-61970/)

Expat GriZ 6th March 2009 18:31

Noob LN2, Dewar questions
 
Hey guys.... I posted this over at Xtremesystems as well but no answers yet so I thought I would try closer to home. Excuse my ignorance but any and all (positive):D responses welcome.

Alright, I've read just about every post here but have some n00b, stupid embarrasing questions for you guys. I'm slowly accumulating the necessary gear to have a go, still have to build my shed so I have a "man cave" to carry this out in a controlled enviornment. (I hate clutter and want to be organized for this) But if I don't ask I'll never know so here goes....

Purchasing a Dewar.....I've looked on ebay, etc. and it seems that dewars are available in the States but pretty lean in Europe. Second hand seems to be the way to go and I've got some feelers out at hospitals, medical, farm supply places but will have to wait till I get home to follow them up. I'm thinking in the 50 liter range which should allow for a good session. Is this about right?? CPU only at this stage, maybe NB but I'm scheming on a chiller idea for graphics.

Now these things look pretty big and heavy and while I'm a rather large individual and could "moose" it around no probs I can't see tipping the dewar to pour it into a small thermos as being the most practical or safe way of doing this. Maybe when its close to empty to get the "last drop". 95 percent of the dewars advertised don't seem to come with a pressure valve assembly. Does this allow for bleeding off or pouring of the LN2 as well? Is a pressure valve absolutely necessary? Is there a tap assembly somewhere that I'm missing? As the LN2 sublimates, burns off etc. there has to be some way of releasing this pressure or does the LN2 just leak out of the top of the dewar?

Ok, you've got the board insulated, pot insulated, temp probe installed....do you just pour the LN2 straight in the pot?? No catalyst (acetone) like dice? Such a rapid change of temps will be pretty hard on the pot but is this how it is done? (I've purchased Kingpin's work of art) I figured if I'm going to try this I may as well have the best!! Not only is it gorgeous but solid!! Does anybody pre chill the pot from ambient?

And lastly, I'm currently residing in Belgium and if any of you MADShrimps are going to have a session with LN2 I'm wondering if I could look in, watch and learn from some experienced hands before just blindly proceeding...I'll bring the beer!!!

If you've made it this far, thanks for reading and please enlighten me on my questions.

Regards,
GriZ

blind_ripper 7th March 2009 16:32

hi griz.

well a 50L dewar is huge!!! massman got my old 35L dewar and when its full its heavy *** hell, though im not the biggest and strongest here i can lift it and tilt it.

e preseure vaulve to releas preseure form the dewar is needed when its filled, when u get the dewar filled let it stay out for night so its cold. never fill a hot dewar! u will lose some ln2 on that, ln2 will not evaperate that fast though but its different from every dewar.

if u want to get a good dewar price condition and so, give me a yell on pm or something.

if u want u can at me on msn ;), it will be easyer to ansewer ure qeustions ;).

greetz blind OCTB

Expat GriZ 7th March 2009 17:44

@ blind ripper

First off, Thank you for your reply and the filling tips!!:ws: It appears that from your description in your post that people do indeed tip these things to pour LN2. Hmmmm, maybe I can weld up a pouring caddy like you see for wine bottles, just bigger!! Will be Pm ing you shortly concerning a dewar...wish I could do MSN but I'm on a very slow connection offshore Spain sailing for Norway. (sounds glamorous but it isn't...its a semi sub lay barge)

Thanks again...pm ing soooooooon!!!!:woot:

blind_ripper 7th March 2009 19:53

hehe no problem ;).
try and look a bit around the forum and try to find the section about our team, maybe u can join use .
there's a lot to learn on hidden parts of this forum.

greetz blind

il send u pm with more info tomorrow or so ;).


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