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?

Um, that's "solid roll stock" - Good grief !

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 '__

"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

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.

"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

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.

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.

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.

"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."

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 '__

"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

"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

"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

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"