Liquid nitrogen question

round here i can get my 20l filled for right around 100 bucks thats southeren PA and its a good sized welding shop the place i was going before was charging me 100 bucks for a 10l fill
 
Lucky I have a major gas supplier about 20 minutes from my house.
Get my 27 litre filled for 29 bucks out the door.
 
Outdoor Gear Dad said:
Hello BF!

I have been doing a subzero quench up till now with dry ice and denatured alcohol. Thinking about switching to LN and doing Cryo. Couple questions. Will I notice much of a difference in the outcomes? What’s the advantage?

also where do y’all buy LN from and how long will it last in the dewar before I have to replace?
Thanks!
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Outdoor Gear Dad said:
Hello BF!

I have been doing a subzero quench up till now with dry ice and denatured alcohol. Thinking about switching to LN and doing Cryo. Couple questions. Will I notice much of a difference in the outcomes? What’s the advantage?

also where do y’all buy LN from and how long will it last in the dewar before I have to replace?
Thanks!
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I have a 35 liter dewer that I get filled at my house every 90 days for about $80. Before that I was paying fairly much more at Airgas and other local places and had the hassle of moving it . If if San Antonio area contact me for my Nitrogen guy, Jerry.
 
Ken H> said:
As I mentioned in the link I posted on first page that is the same dewar I've got, same vendor, same price. Fast shipping. I got the dewar filled June 17th so it's only been a couple weeks. Not empty yet, and seems to have a good bit left. I'm thinking perhaps 3 to 4 wks. Time will tell {g}
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Ken, sorry must have missed that. I just ordered one! I suppose if I build a box and insulate it really well the LN may last longer.

Any safety concerns I should be aware of with LN other than the obvious ones?
 
Lynn Westfall said:
I have a 35 liter dewer that I get filled at my house every 90 days for about $80. Before that I was paying fairly much more at Airgas and other local places and had the hassle of moving it . If if San Antonio area contact me for my Nitrogen guy, Jerry.
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Lynn, is this a company? I am up in Austin. Curious if maybe they have multiple locations.
 
Outdoor Gear Dad said:
I suppose if I build a box and insulate it really well the LN may last longer.
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This is a waste of time and materials...Dewars are designed to keep the cold in and heat out...also designed to allow a small amount of gas to escape over a regulated time frame. Unfortunately this is the Nature of Dewars in general, and if you can get 3 months of constant use out of a c 6 month claimed storage you did damn good! Check local listing for welding supply houses many carry LN2...Airgas is a National Chain. I found Airgas to be considerably more expensive than another supplier.
 
Outdoor Gear Dad said:
Ken, sorry must have missed that. I just ordered one! I suppose if I build a box and insulate it really well the LN may last longer.

Any safety concerns I should be aware of with LN other than the obvious ones?
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Not sure what is obvious, but here is what comes to mind:
1) severe burns if spilled on your skin or splashed in eyes. Wear heavy gloves, and use eye protection
2) it is NOT toxic, BUT if you spill it it could flash to gas and displace oxygen in the room. If you spill, evacuate the room immediately, open doors and windows, use a fan to aid circulation out of the room, and stay out until well after all the liquid has evaporated. A respirator of any sort will NOT help.

there may be more expensive dewars that will keep the ln2 longer, but any time you put a blade in some liquid will evaporate and be lost - that amount will be totally independent of the quality of dewar used
 
DeadboxHero said:
No,
Leidenfrost Effect

It has to settle on skin to burn. It beads off harmlessly due to the leidenfrost effect.
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Yes and no. if you are careless enough to cup it in your hands or immerse your hands into it then the evaporative effect you are talking about is not as significant. Also, if spilled on clothes, they can cold enough to burn. You dont want to get the stuff anywhere near your eyes.... I might understand the effect of an insulating layer of gas between the liquid and my skin or eyes .... but that does not mean that I will personally, or recommend to others, go about using something that cold without precautions.....

YMMV
 
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As someone who works with liquid nitrogen in a laboratory setting almost daily, I fully endorse not wearing any gloves when handling it, assuming you don't have to touch any surfaces that are cooled by it. If you splash the nitrogen onto your skin it will just roll off due to the Leidenfrost effect but if you're wearing a glove the liquid will soak into the glove and freeze your skin. A thick enough pair of gloves can buy you enough time to remove the glove before injury but then dexterity is reduced. That being said, the usual caveats apply here like don't touch an LN2 cooled surface, don't dip your finger in the LN2, don't cup your hand and catch the LN2 if you spill some on yourself, etc. The worst LN2 injury I've personally seen was when someone spilled about a cup of nitrogen onto their forearm while wearing a cotton sweatshirt. The LN2 soaked into the shirt and froze their skin pretty badly before they were able to remove the shirt. Final word of warning: ALWAYS WEAR EYE PROTECTION WHEN WORKING WITH LIQUID NITROGEN! All it takes is a small splash into your face to cause serious injury. Don't risk it.
 
I'm not advocating lack of safety or reckless behavior but it's important to dispell myths.

Folks that have no experience with LN assume its like the movies and anything it touches is frozen solid and shatters.

I'm not saying people should be givin there LN butterfly kisses but that with reasonable precautions and common sense it's basically harmless.

One would have to go out of there way to cause injury with LN in knife making applications.

Cushing H. said:
if you are stupid enough to cup it in your hands
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https://i.imgur.com/4aUfx1Z.gifv

Cushing H. said:
Immerse your hands into it then the evaporative effect you are talking about is not as significant.
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CxJ7YYI.png



Leidenfrost effect


 
CallumRD1 said:
but if you're wearing a glove the liquid will soak into the glove and freeze your skin
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Callum - good summary, thanks. In my comment I was definitely thinking about the issue of soaking into clothes. with gloves in the lab, I am usually thinking about neoprene gloves, which would not soak in and afford a little more thermal protection than bare skin - absolutely not cloth gloves around LN2 - you make that point elegantly. I also worked with LN2 in a lab setting for about 20 years - we were lucky not to have any injuries from it, but all it takes is one slip......
 
DeadboxHero said:
I'm not advocating lack of safety or reckless behavior but it's important to dispell myths.

Folks that have no experience with LN assume its like the movies and anything it touches is frozen solid and shatters
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DeadboxHero - I am not going to respond to this issue again, but will say this. Yes it is absolutely true that the imagined movie experiences of stuff just freezing right away is absolutely wrong. However, that does not mean that LN2 can not injure you. The videos you show are pretty selective and controlled (short immersions, small amounts of liquid rolling around on a palm), and might not reflect what actually happens during an accidental spill. You might get lucky and not get hurt .... but the question, in my mind, is - how lucky do you feel? It is not a myth that LN2 can injure either your skin or your eyes (just read the above posting by Callum). I urge any reader of this thread to please not get complacent with LN2.
 
Yes, Safety is no accident.

Just important to share some of the features of the material.

I never claimed it could not cause harm.

Just wanted to enlighten folks to the leidenfrost effect.



Cushing H. said:
DeadboxHero - I am not going to respond to this issue again, but will say this. Yes it is absolutely true that the imagined movie experiences of stuff just freezing right away is absolutely wrong. However, that does not mean that LN2 can not injure you. The videos you show are pretty selective and controlled (short immersions, small amounts of liquid rolling around on a palm), and might not reflect what actually happens during an accidental spill. You might get lucky and not get hurt .... but the question, in my mind, is - how lucky do you feel? It is not a myth that LN2 can injure either your skin or your eyes (just read the above posting by Callum). I urge any reader of this thread to please not get complacent with LN2.
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When I was a student we used to pour it over our hands, freeze bananas into hammers, freeze rubber tubing until it would shatter, fling a pail of it down a long hallway...lots of dumb stuff.
Be careful etc, but to me it was one of the least scary things around the lab.
 
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