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  #1  
Old 08-18-2016, 08:27 AM
dtec1 dtec1 is offline
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liquid nitrogen dewar

hey guys so any of you that have been following some of my post's know that I have liquid nitrogen for HT ing put into a cooler and I do as many blades as possible before the liquid nitrogen evaporates. (2-3 days) I have been using a thick Styrofoam cooler the kind you would get mail order steaks in its much thicker than one you would buy in a gas station. so anyway I have 3 of these coolers and yesterday I went to get it filled up when I got home I noticed it had a very slow leak (yes the whole backseat of the car and a blanket I put over it in the car was frozen (very happy I don't have leather seats ) and well lets say about half of the liquid was gone so I poured it into another cooler, and took the other good one went back to the place and got more so I lost a lot and wasted money. the guy told me that the liquid will freeze lil channels in the Styrofoam and eventually after about 4 or 5 fills can make it all the way through and cause a lil leak (again small not like you can see the liquid actually leaking out but enough to make a difference for sure) so between this issue and the issue of oil getting to hot when I try to HT to many knives I think its time to find another way and the best way I can see is to invest in a dewar. so I have been doing a lot of searching last night and this morning and I am in a lil bit of information overload. so I was hoping some of you guys that may use liquid nitrogen and give me some advice on either a good site to buy one or a company that I should look for (or a company to stay away from) ANY thing that may point me in the right direction to solve this issue. obviously I don't want to spend $1000 bucks as cheap as possible but also not to cheap where the quality is poor and obviously the neck opening needs to be big enough to fit knives though....any help at all would REALLY be appreciated THANKS guys
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  #2  
Old 08-18-2016, 09:16 AM
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Ray Rogers Ray Rogers is offline
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Two big issues are the size of the neck opening and the rate of loss for a specific dewar. Most dewars have small necks because large necks mean faster loss. Each dewar has a rating that says how fast it will lose its contents. Finding a dewar with a large neck AND a low loss rate is not so easy to do.

But, I did it with my dewar. Mine is a 33 liter dewar with a neck more than 3" across and a loss rate of .18 liters per day. When I bought it, the price was over $900. It costs me about $60 to fill it. Kept in a dark shed out of sunlight in the moderate temperatures we have on this side of the country the LN will last 3 months. I built a wooden box to hold the dewar and lined it with ordinary house type fiberglass insulation and threw a wool blanket over it for good measure and now the LN last for 6 months. So, I fill it twice a year which is good since I have to make a 130 mile round trip to get it filled.

The first one I bought came off eBay from a college laboratory for $25. Filled it and the LN was gone over night. All it takes is the slightest crack in the liner and that dewar is done and you probably can't see the crack.

Mine is for sale but I would imagine shipping would be a real challenge ...


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Old 08-18-2016, 10:22 AM
dtec1 dtec1 is offline
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ok you said yours is 33 liters? do you need that big of one I was looking at some that were between 15 and 25. I guess really it depends on the inside chamber size. how hard is it to get these things around I mean I don't have access to a pick up truck anymore (well maybe we sold ours to my brother in law so I am sure I could work something out) but I do have everyday acces to a chevy equinox its a decent size suv I think it would deffinitly fit way in the back but what I was worried about is getting it in and out of the car especially when its full. how do you go about that are you able to do it yourself or is it a 2person job? oh also 30 liters for 60 bucks out here the cheapest I have found is $5.25 a liter.....why is yours for sale don't you use it? is something wrong with it? just curious as you said shipping probilly wouldn't make it worth it but my curiousity has peeked how much would you let it go for?? oh I also wanted to ask you say you got the dewar about halfway full as it evaporates and you put a blade in and the blades is submerged but some of the tang is stick out is that ok? or does the whole thing need to be submerged now I lay the horizontal so that's not a problem but vertically in a dewar may cause issues with that
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Old 08-18-2016, 12:09 PM
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Ray Rogers Ray Rogers is offline
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The bigger it is the longer the LN will last for any given rating. Besides, the smaller ones aren't likely to have a wide neck.

I carry mine in the back of my Blazer but you're right, it's a bear to get it out when its loaded. Two people is definitely better but I rarely have anyone around to help with it.

Mine is for sale because I retired from knife making five years ago. There's nothing wrong with it - if there was anything at all wrong with it then it would be useless.

Technically, it isn't necessary to put the blade in the liquid and no professional outfit I know of does that. The gas above the liquid is cold enough by far to do the job. That said, when the tank is full there's no other way, the blade has to go in the liquid. As long as that is done slowly - like you see me do on the video - then I've never had a problem. When the tank is down to the last few liters maybe only the tip of the blade is in the liquid but it still seems to work just fine. I mean, think about it: You stick your finger in 1" of LN and leave it there the first joint will freeze pretty quick but in a few hours your whole hand will be frozen. I always leave my blades in over night even though that's much longer than required. It does no harm and gives plenty of time for my oven to cool down ....


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Old 08-18-2016, 01:06 PM
dtec1 dtec1 is offline
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REALLY al this time I didn't know you were retired....I did some research I found the "xt21" on amazon for $640 so I looked up the company and all their products were there no prices when I called them I found out that they don't sell directly but one of their distributors is about 15 mins away from me so I looked on there sites and no prices either so I am going to take a ride over there tomorrow maybe and see what the deal is however I have narrowed it down to a few xt21, hc20 or hc34 lastly ld 25....take a look those four are from 3 different series they make so there are 3 links below one for each series if you got time take a look and let me know what you think.

http://worthingtonindustries.com/get...s.pdf?ext=.pdf
that one the LD25 is what I was thinking

http://www.techair.com/Products+Serv...-332HC-WEB.PDF
on that one either HC20 or HC34

http://www.techair.com/Products+Serv...-331XT-WEB.PDF
that one xt21...if ya get a min let me know what you think about these guys THANKS RAY!!
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Old 08-18-2016, 01:53 PM
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Ray Rogers Ray Rogers is offline
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The xt21's neck is just too small. The LD25 has a barely adequate neck at 2.5" and its .23 evaporation rate could be better.

All in all, I'd want the HC34 if I could get it but the HC20 would be a pretty fair compromise. They have very wide necks and the evaporation rate on the 20 is no worse than any of the others you are considering. The evaporation rate on the 34 is very impressive for a tank with a neck that large, it is almost identical to mine. But, the 20 would be easier to move around and I'm guessing you would have to fill it every two months, maybe less if you put it in an insulated box like I did.

A 2" neck just isn't enough as it would probably choke on an ordinary chef's knife and there's no way you'd get even a small cleaver in there. And don't even think you'll never make a cleaver because you will, or you'll make a Seax or something with a lot of curve in it. Sooner or later you'll need more than a 2" neck. And, don't forget that even if you can squeeze a wide knife into the tank getting a frozen blade out again can be much trickier....


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Old 08-18-2016, 02:54 PM
dtec1 dtec1 is offline
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awesome thanks ray yeh I am going to take a ride to this place tomorw to check them out price is also going to play a factor I am not going to be able to spend too much from what I have seen I am hoping I can find something decent for 7-8 hundred. its deffinitly worth it tho cause then I wont be spending 90 bucks on liquid nitrogen on each batch every 2 weeks and it will also solve the hot oil problem at the same time....I thought the steel actually had to be submerged in the liquid well at least the blade part I figured maybe not the tang cause the edge it relly what you trying to harden. but after reading your post I put my hand in the cooler about a inch above the liquid and after a few mins it did get very cold even tho I wasn't touching the liquid. do you put your blades in one of the canisters and then put that in the dewar or blade alone no canisters?
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Old 08-18-2016, 03:12 PM
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Ray Rogers Ray Rogers is offline
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I make a loop of baling wire through a hole in the tang, slip that loop over the handle of a canister, and then put it in the dewar. On larger knives that won't fit in a canister I tie baling wire through a hole in the tang and then run the wire out the neck. The wire is small enough it doesn't interfere much with the tank's plug. I like having the wire on the blade because you do not want to have to try fishing a blade out of that stuff.

About -100F is cold enough for cryo to work, barely. The LN itself is more than -300F, the gas just above the liquid is about -180f and even up near the neck the temp will be about -100f ...


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Old 08-18-2016, 08:36 PM
dtec1 dtec1 is offline
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yeh fishing in Ln doesn't seem to be a good idea I was reading the sheet for the hc series and it says "" provides -196 deg C at liquid surface and -190 deg C at the top of the canisters" so does that mean the canisters don't go down into the liquid??? the guy told me some of the canisters have a mesh like bottom so the liquid can flow in and out so I thought that the canisters sunk all the way down to the bottom. how does yours work do they go into the liquid or kinda hang at the top?
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Old 08-18-2016, 08:56 PM
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Ray Rogers Ray Rogers is offline
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My canisters have a mesh bottom. They settle an inch or two from the bottom of the tank. That means, they are mostly submerged when the tank is full. That sheet is probably referencing the 'recommended' way to fill the tank which stops well below the mouth of the tank. When I have mine filled we don't stop until the LN reaches the neck. Then, when the stopper is pushed into the tank LN comes gooshing out.....


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Old 08-19-2016, 04:46 AM
jimmontg jimmontg is offline
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The USPS will give you a free quote on the shipping. My experience with them is that the shipping costs is the least of your probs. I would buy Ray's in a flat minute if that's the size I'd need. Ray is a nice guy and even though I've never met him he seems to be a straight shooter. You need to hang out on Sunday nites Dtec. Ray runs that for nothing in return, so I'm guessing his word is his bond and have him over-insure the dewar. Just MHO.

Plus he lives in the middle of nowhere in Washington state so you know where he lives, but then you never know about them mountain people, they hang together pretty good.LOL

Last edited by jimmontg; 08-19-2016 at 04:53 AM.
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