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#31
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Well, good news...... I found a 1"-40 tap and die to make a plug in the
top of my cylinder. A 1 inch hole isn't exactly what I had in mind, but it'll have to work for now. I will start with some solid bar stock for the plug if I can find it..... Chances are I'll have to turn it on the lathe before the die will accept it. That's what I'll be doing over lunch today. Probably won't finish today. I still don't know what pressure this thing will balance out at..... I couldn't find any information on that. It seems to me the 1200psi would be complete "theoretical" sublimation. I have also considered, once pressure inside the tank builds, temp should change. The CO2 will absorb heat? right? I would guess the sublimation rate will be dependant on the thermal properties of the tank......The tank will get cold, right? |
#32
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Um, that's "solid roll stock" - Good grief !
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#33
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spiral_72 wrote:
Well, good news...... I found a 1"-40 tap and die to make a plug in the top of my cylinder. A 1 inch hole isn't exactly what I had in mind, but it'll have to work for now. I will start with some solid bar stock for the plug if I can find it..... Chances are I'll have to turn it on the lathe before the die will accept it. That's what I'll be doing over lunch today. Probably won't finish today. I still don't know what pressure this thing will balance out at..... I couldn't find any information on that. It seems to me the 1200psi would be complete "theoretical" sublimation. I have also considered, once pressure inside the tank builds, temp should change. The CO2 will absorb heat? right? I would guess the sublimation rate will be dependant on the thermal properties of the tank......The tank will get cold, right? Anything uninsulated that I've ever put dry ice in has gotten quite cold and had condensation all over the outside. Plan on a damp cylinder. -- __ Elaine T __ __' http://eethomp.com/fish.html '__ |
#34
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"spiral_72" wrote in message oups.com... Well, good news...... I found a 1"-40 tap and die to make a plug in the top of my cylinder. A 1 inch hole isn't exactly what I had in mind, but it'll have to work for now. I will start with some solid bar stock for the plug if I can find it..... Chances are I'll have to turn it on the lathe before the die will accept it. That's what I'll be doing over lunch today. Probably won't finish today. I still don't know what pressure this thing will balance out at..... I couldn't find any information on that. It seems to me the 1200psi would be complete "theoretical" sublimation. I have also considered, once pressure inside the tank builds, temp should change. The CO2 will absorb heat? right? I would guess the sublimation rate will be dependant on the thermal properties of the tank......The tank will get cold, right? I know this is a long shot, but is there any concern about the steel you are using for your cylinder at the very low temperature dry ice is at? Is embrittlement or anything else that could weaken the cylinder a concern? dwhite |
#35
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Actually, yea..... I thought about that. I really don't know what to
expect. I would suppose a material could be brought to a low enough temp causing that material to become brittle. Water, plastic, chewing gum, lots of stuff becomes brittle at a low enough temp. Any idea what that temp is for steel? Oh, a little note here. The dry ice did not seem to effect my lunch box. I'm still using the lunch box anyhow pat - pat..........3 hours 30 minutes till eatin' time. A damp cylinder is the least of my worries. Besides maybe I can collect it and use the water to refill what evaporates from the tank. HA! So, many unknowns..... Guess that reaffirms the fact that the cylinder's first week or two will be spent outside. |
#36
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"spiral_72" wrote in message
oups.com... Actually, yea..... I thought about that. I really don't know what to expect. I would suppose a material could be brought to a low enough temp causing that material to become brittle. Water, plastic, chewing gum, lots of stuff becomes brittle at a low enough temp. Any idea what that temp is for steel? I haven't looked that up -- maybe it can be found by googling. It probably depends on the type of steel, although they might all be in the same neighborhood. I checked on dry ice the other day and I think it sublimes at -78.5 deg C at atmospheric pressure, and warmer at higher pressure, but you'd need an equilibrium diagram for that. -78.5 C should be the worst case though. dwhite |
#37
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My odds for this one:
60% chance the whole thing is a hoax. Pretty funny one at that. 25% chance of a fizzing flop due to leaky welds and threads. 14% chance of a new Darwin Award winner 1% chance Spiral will have the last laugh when the whole thing works as planned. |
#38
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1 LITTLE PERCENT!!!???!!! WHAT'S UP WITH THAT?
Actually, the ONLY thing I am concerned about is I throw the ice in this dude....cork it..... have it build up pressure and the CO2 only lasts five minutes. I have no idea what the equivalent gas volume a 1 pound chunk of dry ice has. |
#39
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Oh, for those wanting an update...... Hopefully I will be able to cut
threads today over lunch for the tank pressure gauge. I will hopefully weld the top on it tonight.and hopefully I will have some news, good or bad, by Monday morning. 1 percent.... good grief. |
#40
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"spiral_72" wrote in message
oups.com... 1 percent.... good grief. ROFLMAO....I certainly wish you luck with it, and try not to blow yourself and family into the next millenium. -- "In the beginning, God said the four-dimensional divergence of an antisymmetric, second rank tensor equals zero, and there was Light , and it was good." |
#41
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spiral_72 wrote:
1 LITTLE PERCENT!!!???!!! WHAT'S UP WITH THAT? Actually, the ONLY thing I am concerned about is I throw the ice in this dude....cork it..... have it build up pressure and the CO2 only lasts five minutes. I have no idea what the equivalent gas volume a 1 pound chunk of dry ice has. Well, the volume depends on the temperature but the ideal gas law lets you calculate it. (more or less) pv=nrt p = pressure in atmosphteres v = volume in litres n = number of moles r = a constant = 0.08205 L atm / (mol·K) t = temperature in degrees K. C02 is 44 g/mol and a pound is 454 grams so you have about 10 moles of C02. At standard temperature and pressure (273K or 0C and 1 atm), one mole of gas is 22.4 L of volume. So your 1 lb block would sublime to occupy 231 litres of volume at freezing. You can use the number of moles, your tank volume, the temps in the tank, and this equation to predict the actual pressure in your tank in atmospheres. -- __ Elaine T __ __' http://eethomp.com/fish.html '__ |
#42
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"Elaine T" wrote in message
. .. spiral_72 wrote: 1 LITTLE PERCENT!!!???!!! WHAT'S UP WITH THAT? Actually, the ONLY thing I am concerned about is I throw the ice in this dude....cork it..... have it build up pressure and the CO2 only lasts five minutes. I have no idea what the equivalent gas volume a 1 pound chunk of dry ice has. Well, the volume depends on the temperature but the ideal gas law lets you calculate it. (more or less) pv=nrt p = pressure in atmosphteres v = volume in litres n = number of moles r = a constant = 0.08205 L atm / (mol·K) t = temperature in degrees K. C02 is 44 g/mol and a pound is 454 grams so you have about 10 moles of C02. At standard temperature and pressure (273K or 0C and 1 atm), one mole of gas is 22.4 L of volume. So your 1 lb block would sublime to occupy 231 litres of volume at freezing. You can use the number of moles, your tank volume, the temps in the tank, and this equation to predict the actual pressure in your tank in atmospheres. ....and you've already provided the volume and pressure, so he can just solve for the new pressure after finding out his cylinder volume. P1V1 = P2V2 as you know, so (1 atm)(231 litres) = P2(cylinder volume). This is the pressure at 0C. Spiral - just divide each side by the temperature (T1 = 273 and T2 = room temp or whatever you want) and solve for P2 if you want to know your pressure at different temperatures. You might need to look at a property diagram for CO2 to make sure your results are correct. If you calculate your pressures to be too high, for example, you might be getting a phase change in reality. dwhite |
#43
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"spiral_72" wrote in message
oups.com... Oh, for those wanting an update...... Hopefully I will be able to cut threads today over lunch for the tank pressure gauge. I will hopefully weld the top on it tonight.and hopefully I will have some news, good or bad, by Monday morning. 1 percent.... good grief. Hey, I thought 25% chance of leaky welds was an insult! You obviously do something like this for a living, so I have to think you will make good welds and threads. But then again, you might be a troll! dwhite |
#44
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"Dan White" wrote in message ... "spiral_72" wrote in message oups.com... Actually, yea..... I thought about that. I really don't know what to expect. I would suppose a material could be brought to a low enough temp causing that material to become brittle. Water, plastic, chewing gum, lots of stuff becomes brittle at a low enough temp. Any idea what that temp is for steel? I haven't looked that up -- maybe it can be found by googling. It probably depends on the type of steel, although they might all be in the same neighborhood. I checked on dry ice the other day and I think it sublimes at -78.5 deg C at atmospheric pressure, and warmer at higher pressure, but you'd need an equilibrium diagram for that. -78.5 C should be the worst case though. dwhite Dodge the whole embrittlement problem by putting down a layer of 1/4" - 1" thick styrofoam between the dry-ice and the base of the tank. It should not affect the volume capacity significantly, but it will keep the steel at a reasonable temperature. It will slow down your melt rate quite a bit, but that's probably not a bad thing anyways. You could use a ceramic or hard plastic insulator too, but I'd be concerned about the additional shrapnel when the tank explodes ;-) Joe |
#45
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Hey, I cut a nice plug for the top yesterday. I ended up with one inch
of 1"-40 threads on a 1.25" dia plug. I bored a 1/8" hole through the plug, down the centerline. Finally I bored a 7/16" - 1" deep hole and cut threads for 1/4" pipe. I mounted my pressure gauge in the top of the plug. All I can find at the moment is a 0-60bar gauge... 800 something psi I think. It is actually a borrowed gauge, that's why I mounted it in the plug. I figured that's better than trying to fix a big gaping hole in the tank when a new gauge requires an assortment of fittings to thread 1/4" pipe. The fitting on this gauge is brass instead of steel. I don't gat any warm fuzzies from that, but I guess we'll see. After all I am testing Da Bomb outside right? The neighbors have goats..... I wonder how goats respond to 1/4" steel debris traveling at the speed of sound? and a shock wave? "Da Bomb" = "Da Goat Bomb" |
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