PDA

View Full Version : acetylene bottles lying on their side?



metalmagpie
12-14-2010, 09:56 AM
I have always been taught, read, and heard that if you ever tip an acetylene cylinder on its side (e.g. transporting it in a trunk) that you have to stand it up for 24 hours before it can then be used.

Why? What bad thing happens if you don't?

Highpower
12-14-2010, 10:01 AM
The acetone in the bottle need to settle to the bottom, otherwise you end up releasing it along with the gas. Not good. :o

tdmidget
12-14-2010, 10:02 AM
Never heard the 24 hour thing but acetylene is unstable under pressure. To keep it stable the tank is filled with an absorbent material soaked in acetone. This allows the acetylene to dissolve in the acetone. If laid on it's side the acetone/acetylene mixture can escape through the valve

moe1942
12-14-2010, 10:24 AM
If you need it right away don't transport lying down. If you can wait keep it vertical for the length of time it was on its side. The acetone should migrate at the same rate.

I have always transported my bottles on their sides. No problems but I usually don't use them til the next day.

Herm Williams
12-14-2010, 11:38 AM
I have repaired regulators with diaphragms/seals damaged from the acetone. That is another reason the regulator has a red line on it, you don't want to get ahead of the rate of seperation.
re

radkins
12-14-2010, 11:59 AM
That is another reason the regulator has a red line on it, you don't want to get ahead of the rate of separation.
re


I don't understand what you mean by that?:confused:

The red warning area has nothing to do with flow rate and is the excessive pressure warning area, flow rate can be easily exceeded at even lower pressures so staying out of the red area will not prevent excessive flow rates. This usually occurs with a high volume attachment like a heating tip but even a cutting torch can exceed the flow rate with a small tank and/or cold temperatures. In very cold weather Acetylene tank flow rates drop by a lot and using a large volume attachment can draw Acetone in those conditions when it might not if the tank was warmer. That red area is very important for the pressure setting however since Acetylene becomes unstable above 15 PSI and can self-ignite if it comes into contact with Oxygen, even small amounts of Oxygen entering the fuel line is bad enough under normal pressure settings but at over 15 PSI it can ignite without an external ignition source. In any case NEVER operate a torch with the regulator setting in the red area on the gauge!

jr45acp
12-14-2010, 12:09 PM
This observance has been from years back, early 60's or so, but I've seen pipeline welders with both tanks rigged horizontally on their trucks. I asked one if this wasn't dangerous, and he basically blew me off. So, just to be safe, if I've had a tank horizontal, I don't use it until it has been verticle for at least the same amount of time.

Richard Wilson
12-14-2010, 12:23 PM
This observance has been from years back, early 60's or so, but I've seen pipeline welders with both tanks rigged horizontally on their trucks. I asked one if this wasn't dangerous, and he basically blew me off. So, just to be safe, if I've had a tank horizontal, I don't use it until it has been verticle for at least the same amount of time.

In the UK at any rate, its a Health and Safety contravention to store or use gas bottles (thats all gases, not just acetylene) other than vertical. They not only have to be vertical, but be restrained so they can't fall over. Even if they are chained to a trolley, the preference is for the whole thing to be chained to a column. Partly its because of the acetone issue with acetylene, the other is that if the valve on the top of the bottle gets damaged or knocked off, and the gas releases at high pressure, the whole bottle can shoot off sideways like a rocket. At least, thats what the H&S inspector told me last time I fell foul of them over gas bottles.

Richard

radkins
12-14-2010, 12:30 PM
This observance has been from years back, early 60's or so, but I've seen pipeline welders with both tanks rigged horizontally on their trucks. I asked one if this wasn't dangerous, and he basically blew me off. So, just to be safe, if I've had a tank horizontal, I don't use it until it has been verticle for at least the same amount of time.



The guy probably used only very little gas from that tank, I have seen several times people trying to use a tank on it's side and Acetone is almost immediately drawn into the regulators. Another fellow I know who has a construction equipment service truck has his tanks laying on their sides and he is completely ignorant to the problem! His truck and torch rig reeks of the odor (that stuff STINKS) from the bleeding Acetylene tank and his regulator is usually junked. When I asked him about regulator problems he commented about how everything is Chinese these days and that good equipment can't be found now. When I tried to explain that his problem was the horizontal tank he did as you said the pipe line welder did, he basically just blew me off" and acted insulted. I certainly did not force the issue and did not say anything else but the guy obviously does not know what he is doing and that pipe line welder sounds like he has a lot to learn also, of course some people learn all they are going to on the first day and after that no one can tell them anything. :rolleyes:

Evan
12-14-2010, 12:39 PM
That red area is very important for the pressure setting however since Acetylene becomes unstable above 15 PSI and can self-ignite if it comes into contact with Oxygen, even small amounts of Oxygen entering the fuel line is bad enough under normal pressure settings but at over 15 PSI it can ignite without an external ignition source. In any case NEVER operate a torch with the regulator setting in the red area on the gauge!


This is a misunderstanding of the explosive hazard associated with acetylene. Acetylene is a metastable chemical compound. It will spontaneously dissociate under pressures around 30 psi if it isn't in very close contact with stabilizing surfaces. That dissociation has no dependence on contact with other elements such as oxygen and is not a combustion reaction either. It requires no oxygen to occur and is a high explosive detonation in the same manner as nitroglycerine.

The pressure limit of 15 psi is used to provide a safety margin at normal temperatures.

mike os
12-14-2010, 01:58 PM
correct... even a tightly closed bottle can go off on its own in the wrong circumstances....& that does not mean in a fire. IIRC even a hard knock can potentially "set one off", particularly if the acetone or core is damaged.

Black_Moons
12-14-2010, 02:08 PM
I keep all my bottles upright, Even the argon for my welder, Because having the valve at ground height would make it a LOT easyer to drop something on it or smash something into it without looking. I sure would love to have it tucked under my welder on a cart, but its just not safe.. Not to mention, With the regulator down there, id never remember to shut the dang thing off.

macona
12-14-2010, 02:20 PM
One of the reasons for the odd angled valve on MC tanks is because they were intended to be used at an angle, as in attached to a motorcycle frame, thats where MC comes from.

lazlo
12-14-2010, 03:14 PM
I have always been taught, read, and heard that if you ever tip an acetylene cylinder on its side (e.g. transporting it in a trunk) that you have to stand it up for 24 hours before it can then be used.

The AWS/CGA recommendation is 15 minutes for every 15 minutes the bottle was on its side in transport.

radkins
12-14-2010, 04:33 PM
This is a misunderstanding of the explosive hazard associated with acetylene. Acetylene is a metastable chemical compound. It will spontaneously dissociate under pressures around 30 psi if it isn't in very close contact with stabilizing surfaces. That dissociation has no dependence on contact with other elements such as oxygen and is not a combustion reaction either. It requires no oxygen to occur and is a high explosive detonation in the same manner as nitroglycerine.

The pressure limit of 15 psi is used to provide a safety margin at normal temperatures.


Lots of misunderstandings about Acetylene and other gases sometimes these are even in printed manuals such as what I was saying about the Acetylene, I have read that more than once- which of course does not make it so.

Your explanation actually clears up something else I have wondered about in the past and that is how the Acetylene could explode at about 30 PSI (I was quite aware of the safety margin) in a hose but not in the tank at it's much higher normal pressure since not 100% of the gas will be dissolved in the tank at all times. The only explanation was the one about Oxygen being introduced into the gas contained in the hose but there are many problems with that reasoning, still until now that was the only explanation I was aware of and it is quite common even if wrong which apparently it is, once again I have learned something and you have corrected me on a long held misconception about acetylene.

The point I was actually trying to make however is that relying on the red warning zone (and that is a "warning not to use" and not "use with caution" as some seem to think!) to prevent overdrawing the tank will not work. Overdrawing the the tank is of course a function of too much volume over a given time period and not how much pressure being supplied to the torch.

.

gary350
12-14-2010, 04:55 PM
The metal cylinder is filled with cement and it is full of holes like a sponge. The cement makes it hard to accidently damage the cylinder. It is very hard to dent or make a hole in the cylinder.

The cylinder is then filled with Acetone.

Next it is filled with Acetylene.

The Acetone adsorbs the Acetylene like a Soft drink adsorbs Carbon Dioxide. This is a safety if you accidently brake off the valve the Acetylene will not come shooting out and cause an explosions. The Acetone can catch on fire and burn but not much Acetylene will burn. Acetylene is slowly be released from the Acetone like Carbon Dioxide is slowly released from a Soft Drink.

If you lay a acetylene cylinder down you need to stand it up to use it. If you stand it up by the time you get the regulator attached it is ready to be used. I take my empty cylinder to the welding shop to get a replacement I haul it home laying down. I roll it in the shop then stand it up and chain it to the wall. Next I slowly open the valve to blow out any dirt and dust before I attach the regulator. I attach the regulator and start using it right away. I have never had a problem.

When I was young and stupid I use to make a spark plug adaptor so I could screw the spark plug it into an old air compressor tank. Then I put about 9 psi of Acetylene into the air tank. Then I put about 150 psi air pressure in the tank. Then run about about 1/4 mile of wire from the air tank to the ignition of my car. Turn the key and the air tank explodes like a whole case of dynamite. Metal pieces go flying in all directions you can hear the pieces as they go whistling through the sky in all directions. It is a miracle I didn't get killed.

loose nut
12-14-2010, 05:16 PM
Modern acetylene manifold systems are suppose to have a regulator on each bottle, that way there is no free acetylene at a pressure of over 15 psi, controlling several regulators so that they all have the same output pressure is a drawback.

The system where I work is an old (read grandfathered) high pressure system and has all the bottles tied into one regulator. This means that the hoses and pipes running between the bottles and the regulator are at what ever pressure the bottles are, up to 250psi, more on a hot day.

People hear about this and gasp, "it will explode". It's been there over 50 years and hasn't yet, I have been taking care of it for the last 27 years without any problems.

That's not to say it won't someday, hopefully after I retire.

jungle_geo
12-14-2010, 05:28 PM
When I was young and stupid I use to make a spark plug adaptor so I could screw the spark plug it into an old air compressor tank. Then I put about 9 psi of Acetylene into the air tank. Then I put about 150 psi air pressure in the tank. Then run about about 1/4 mile of wire from the air tank to the ignition of my car. Turn the key and the air tank explodes like a whole case of dynamite. Metal pieces go flying in all directions you can hear the pieces as they go whistling through the sky in all directions. It is a miracle I didn't get killed.

Wow, that sure brought back some memories of when I was much younger! We used balloons and garbage bags and a snuffed out neutral flame mix...amazing we never died doing it. It sure gives me the willies now...not sure why it didn't then...I seems so obviously stupid now. Bored young boys living far from urban constraints.

radkins
12-14-2010, 06:00 PM
Modern acetylene manifold systems are suppose to have a regulator on each bottle, that way there is no free acetylene at a pressure of over 15 psi, controlling several regulators so that they all have the same output pressure is a drawback.

The system where I work is an old (read grandfathered) high pressure system and has all the bottles tied into one regulator. This means that the hoses and pipes running between the bottles and the regulator are at what ever pressure the bottles are, up to 250psi, more on a hot day.

People hear about this and gasp, "it will explode". It's been there over 50 years and hasn't yet, I have been taking care of it for the last 27 years without any problems.

That's not to say it won't someday, hopefully after I retire.



I too am aware of a system in operation as of now that is very similar, 5 tanks all connected to a manifold made of some type of soft 1/4" ID metal tubing (bends easily but is not Copper or Aluminum) feeding into one large regulator. This then discharges into a heavy steel water filled back-flash arrester and then that is plumbed into 1/2" Black Iron pipes that go to various places in the shop. At each take-off point there is another regulator and a back-flow preventer. In the Black Iron pipes the pressure is at whatever the main regulator is set to but the 8 or 9 feet of 1/4" metal tubing plus a rather large brass fitting at the regulator are all at tank pressure, sitting outside the building this system gets quite hot in the summer but has been there for nearly 30 years.

macona
12-14-2010, 06:11 PM
The metal cylinder is filled with cement and it is full of holes like a sponge. The cement makes it hard to accidently damage the cylinder. It is very hard to dent or make a hole in the cylinder.

The cylinder is then filled with Acetone.

Next it is filled with Acetylene.

The Acetone adsorbs the Acetylene like a Soft drink adsorbs Carbon Dioxide. This is a safety if you accidently brake off the valve the Acetylene will not come shooting out and cause an explosions. The Acetone can catch on fire and burn but not much Acetylene will burn. Acetylene is slowly be released from the Acetone like Carbon Dioxide is slowly released from a Soft Drink.

If you lay a acetylene cylinder down you need to stand it up to use it. If you stand it up by the time you get the regulator attached it is ready to be used. I take my empty cylinder to the welding shop to get a replacement I haul it home laying down. I roll it in the shop then stand it up and chain it to the wall. Next I slowly open the valve to blow out any dirt and dust before I attach the regulator. I attach the regulator and start using it right away. I have never had a problem.

When I was young and stupid I use to make a spark plug adaptor so I could screw the spark plug it into an old air compressor tank. Then I put about 9 psi of Acetylene into the air tank. Then I put about 150 psi air pressure in the tank. Then run about about 1/4 mile of wire from the air tank to the ignition of my car. Turn the key and the air tank explodes like a whole case of dynamite. Metal pieces go flying in all directions you can hear the pieces as they go whistling through the sky in all directions. It is a miracle I didn't get killed.

Well, you got a little right.

Acetylene cylinders are not filled with cement. It looks like cement but much more porous. Old tanks are filled with an asbestos mix, new tank are a ceramic matrix. This works with the acetone to stabilize the acet. Also keeps it from sloshing around.

Acetone is not for safety in case the bottle valve comes off, it stabilizes the acet so that you can fill a cylinder over the critical pressure of acet without it becoming a bomb.

A bottle is not ready as soon as you turn it vertical. Like mentioned above equal time vertical as it was horizontal. Just because you have been lucky does not make it good practice.

Evan
12-14-2010, 06:15 PM
People hear about this and gasp, "it will explode". It's been there over 50 years and hasn't yet, I have been taking care of it for the last 27 years without any problems.


It won't detonate as long as there are no spaces larger than the minimum explosion cell size for the gas and the pressure it is at. Acetelyene isn't the only gas with this characteristic but it is the most familiar. Each gas has a different typical cell size for a given pressure and if it is enclosed in a smaller diameter tube it cannot propagate a detonation wave. It requires that the molecules have a given number within a particular distance from each other and distance from a solid material for detonation to occur.

radkins
12-14-2010, 06:26 PM
Evan, would free Acetylene in a metal line be adversely affected by shock such as a sharp blow to the line?

lazlo
12-14-2010, 06:28 PM
Well, you got a little right.

Acetylene cylinders are not filled with cement. It looks like cement but much more porous.

He actually got most of it right :)

Acetylene cylinders are filled with Agamassan, for which Nils Dalén won the Nobel prize (and ironically was later blinded by an acetylene explosion).
Agamassan was, until recently, a mixture of asbestos, cement, coal and diatomaceous earth. They replaced the asbestos with some other filler during the asbestos lawsuits of the 80's.

By the way, the poor guy just asked how long you have to leave acetylene bottles to sit upright before you use them. Do we have to turn everything into a Google flame fest?

metalmagpie
12-14-2010, 07:25 PM
OK. So far there have been a whole lot of posts none of which has answered the basic question. Say I lie an acetylene cylinder on its side for 24 hours. Then I stand it up, and at 23 hours I start using it. What risk am I running?
For that matter, what happens if I start using it at 5 minutes?

I already know you have to let them stand and re-equilibrate. What I don't understand is WHY.

FYI I have been using oxy/acetylene equipment since I was 15 and I'm nearly 60. And I used to make my living as a shipfitter, whose main tool is a torch.

metalmagpie

lazlo
12-14-2010, 07:39 PM
I already know you have to let them stand and re-equilibrate. What I don't understand is WHY.

As has been said, acetylene is unstable above 15 psi, especially in the presence of oxygen. Acetylene dissolves in acetone, and oxygen doesn't, so an acetylene bottle is filled with porous cement, which is then soaked with acetone, and then filled with acetylene.

At that point, the dissolved acetylene/acetone solution is no longer in contact with oxygen, and the bottle is stable.

If you tip the bottle on it's side, the acetone and acetylene separate, and you're back to volatile, pure acetylene.

That's also why you're not supposed to drain an acetylene bottle -- you're likely to backpressure air (oxygen) into the bottle by draining it.

By the way, this is an acetylene safety brochure that was handed out in one of my welding classes:

http://www.airproducts.com/nr/rdonlyres/9d325c49-7c62-41e5-aa0b-8411db4d84f8/0/safetygram13.pdf

darryl
12-14-2010, 08:18 PM
Something a little funny there. Why should the acetone and acetylene separate when the bottle is on its side? The acetone absorbs the acetylene, presumably it remains a liquid, and is under the effect of gravity. With the tank upright, the liquid is in the bottom- if the tank is on its side, the only thing that's changed is that the bottom is now wider and not as tall. I can't see that as a recipe for the two parts to separate-

What I can see is the liquid mixture invading the valve. You'd want to let that clear away back into the tank so you don't vent the acetone, hence have the tank upright. I'd bet there's a time period that it takes for a fully invaded valve to clear, and any time longer than that is wasted time if you're waiting to use the tank.

That's my guess anyway. Other than that, possibly there's an orientation to the foam inside that makes it more workable with the tank upright- though I think that's stretching it.

I'm reminded yet again about the oxygen bottle falling over in a shop here in town. The valve broke off somehow and the bottle went around the shop, then across the street, where it went through the wall of a tire store. The front and side of that store were almost completely glass- from about two feet above ground and up to near ceiling height. Needles to say, there was a lot of broken glass, but no fire and nobody got hurt apparently.

Highpower
12-14-2010, 09:34 PM
Next I slowly open the valve to blow out any dirt and dust before I attach the regulator.
I was under the impression that an acetylene cylinder is the only one you shouldn't do this on? :confused:

Evan
12-14-2010, 09:57 PM
At that point, the dissolved acetylene/acetone solution is no longer in contact with oxygen, and the bottle is stable.

If you tip the bottle on it's side, the acetone and acetylene separate, and you're back to volatile, pure acetylene.

That's also why you're not supposed to drain an acetylene bottle -- you're likely to backpressure air (oxygen) into the bottle by draining it.


It has nothing to do with oxygen. There isn't any oxygen in the acetylene bottle and the explosive properties don't depend on oxygen at all. There is free acetylene in the top of the bottle when the bottle is upright. There has to be room for the acetylene to bubble out of solution from the acetone without it passing out of the bottle. The free space isn't empty, it is filled with the porous filler. When the bottle is laid on it's side the free acetylene gradually percolates through the filler away from the outlet leaving the outlet filled with acetone. When the bottle is stood up the acetone gradually percolates down and the free acetylene percolates back to the top.

There is also a fine powder residue that is a result of particles shed by the filler material during normal handling. That powder must have time to settle back into the filler matrix along with the acetone. This in fact can be the greatest source of problems because if traces of the powder are carried out with acetone they can destroy the regulator.

This is not a guess or my opinion. My wife sells industrial gases and I am trained on the properties and handling of industrial gas cylinders so I can fill in for her if necessary.



Evan, would free Acetylene in a metal line be adversely affected by shock such as a sharp blow to the line?


Not likely. The rest of the line is still below the propagation cell size.

BTW, to answer how long the bottle must be stood up before using: One hour for every hour down to a maximum of 24 hours. If it has been down for more than 24 hours then it should be stood up for 48 hours.

lazlo
12-14-2010, 10:08 PM
This is not a guess or my opinion. My wife sells industrial gases and I am trained on the properties and handling of industrial gas cylinders so I can fill in for her if necessary.

My Wife is the North American OSHA acetylene safety regulator, so I'm trained for hazmat handling of acetylene bottles :rolleyes:

http://i164.photobucket.com/albums/u15/rtgeorge_album/acetylene2.jpg

http://i164.photobucket.com/albums/u15/rtgeorge_album/acetylene1.jpg

Evan
12-14-2010, 10:21 PM
The first poster is total bunk.

The second poster is only partly bunk. The filler has nothing to do with "allowing the acetylene to dissolve in the acetone". It will do that without filler. It is to make sure that no part of the tank has an open area that exceeds the minimum detonation cell size.

More bunk: Acetylene doesn't become unstable in contact with oxygen.

Even more bunk: Acetone can't "clog a regulator". It is a volatile liquid. It's the powder carried with it than can damage the regulator.

BTW, the acetone doesn't "stabilize" the acetylene. By dissolving the acetylene in the acetone it is no longer under pressure as a compressed gas. It is in a solution in a liquid that it essentially incompressible. The only portion of the acetylene that is a compressed gas is the small amount of free acetylene at the top.

lazlo
12-14-2010, 10:34 PM
The first poster is total bunk.

The second poster is only partly bunk.

I'm so glad a photocopier repairman knows more about acetylene safety than the Pennsylvania Bureau of Deep Mine Safety, and Victor :rolleyes:

Those "posters" are slides from

http://www.portal.state.pa.us/portal/server.pt?open=18&objID=503858&mode=2

Oxy-Acetylene Safety (http://www.portal.state.pa.us/portal/server.pt?open=18&objID=503858&mode=2)
Presented by
Bureau of Deep Mine Safety
Special thanks to Victor Equipment Co. and Valley National Gas, Inc.

Evan
12-14-2010, 10:39 PM
I'm so glad that a chip designer is suddenly an expert on industrial gases. :rolleyes: The posters are bunk, I don't care who published them. Look up the physics for yourself.

lazlo
12-14-2010, 10:41 PM
Why should the acetone and acetylene separate when the bottle is on its side?

Honestly, I don't know the chemistry. But Gary was correct in his description that you load the Agamassan (the porous cement) with acetone, then fill the soaked mixed with acetylene. In use, the acetylene evaporates out of the acetone/Agamassan mixture, and it works safely.

I do know, first-hand, that when you tilt the bottle on it's side acetone comes out -- it has a very distinctive smell.

The evaporation rate of the acetylene out of the acetone/acetylene solution is also the reason for the rule that you shouldn't pull more than 1/7th of the bottle's capacity of acetylene out per hour, because above that flow rate the acetylene can't evaporate fast enough, and you pulling acetone out. I've done that too -- fingernail polish smell :)

Evan
12-14-2010, 10:45 PM
The acetylene doesn't "evaporate" out of the acetone. It comes out of solution because of the reduction in pressure in the free acetylene above the liquid. It is exactly the same as CO2 coming out of solution from water. It has nothing to do with evaporation.

lazlo
12-14-2010, 10:49 PM
I'm so glad that a chip designer is suddenly an expert on industrial gases. :rolleyes:

Ordinarily, that would be amusing Evan, but as you know, I've just completed three semesters of welding at ACC. I don't claim to be an expert, but that's what the instructors, who are certified welding inspectors, taught us, and fortunately their explanation agrees with the Pennsylvania Department of Deep Mine Safety, Victor, and Valley national gas.

lazlo
12-14-2010, 10:56 PM
The acetylene doesn't "evaporate" out of the acetone.

From Instrumentation and Analytical Science
by P. A. G. Payne, Institution of Electrical ... - 1989 - Technology & Engineering


”As the acetylene evaporates from the acetone solution, and passes out of the reducing valve it warms slightly as the Joule-Thompson coefficient is negative ..."

Boucher
12-14-2010, 10:57 PM
In 1970 I went to work for my FIL. His tanks were laid down and they were used that way. I argued until we parted ways in 1978 and never convinced him to change. I am not advocating this but in twenty five years there was never any operational problems. I suspect that the tanks were not completely filled and the warm temperatures of south Texas may have helped.

We commonly used a large rosebud that requirred a lot of gas.

Our local welding supply had a big ruptured Acct tank by the loading dock. I sure would not have wanted to be anywhere near it when it popped.

A few years back the Acct loading plant on Industrial in Dallas exploded and burned. Big Boom!!!

I saw the failure report from an explosion resulting from transporting a bottle in the trunk of a car. It is thought that the meltable safety plug was leaking. It looked like several sticks of dynamite had exploded in the trunk.

lazlo
12-14-2010, 11:01 PM
His tanks were laid down and they were used that way. I argued until we parted ways in 1978 and never convinced him to change.

Yeah, I've done that too -- used an acetylene bottle out of the back of a truck, lying on it's side. Same deal with the 1/7th rule, which is easy to surpass with a rosebud -- the acetone smell is very distinct.

Like running a pedestal grinder without shields -- you can get away with it 99 times out of 100. The 100th time is pretty spectacular.

macona
12-15-2010, 12:48 AM
One of four parts of agamassan being cement does not make it cement.

That first part of the two page is wrong. The agamassen is not crushed fire brick. The material is quite solid if you have ever seen a cylinder split in half. Yes, acet does dissolve in acetone and o2 does not, but the main reason for it being dissolved is the stabilizing effect it has that allows it to be stored at a high pressure.

Mr. Payne is using the wrong terminology. Evan is right, the gas comes out of solution, it cannot evaporate as evaporation is a transition from liquid to gas. It is already a gas and as mentioned if it comes out of solution too fast you can get acetone in the regulators and lines which will not plug them, but destroy the rubber. Just like opening a shaken bottle of soda.

BOC says it comes out of solution:

http://zenstoves.net/MSDS/Acetylene.pdf

Here is Princeton's view on it:

http://web.princeton.edu/sites/ehs/labsafetymanual/cheminfo/acetylene.htm


Beleving an instructor knows much about the equipment is wishful thinking. I have known instructors and inspectors that barely understand how the equipment they are welding with works, but they dont need to. The use of the equipment does not require knowing how it works and knowing isnt necessarily going to make you a better operator.

lazlo
12-15-2010, 01:04 AM
One of four parts of agamassan being cement does not make it cement.

It's a cement with various lightweight aggregates to make it porous. The Cement, coal, asbestos, diamataceous earth formula has simply replaced the asbestos with silica lime.
Or, by OSHA's definition of Agamassan: "The liquid acetone is then stored in the acetylene cylinder, which in turn, is filled with a porous (sponge-like) cementitious material."


Mr. Payne is using the wrong terminology. Evan is right, the gas comes out of solution, it cannot evaporate as evaporation is a transition from liquid to gas.

The acetylene is in solution -- it's liquid acetylene until it evaporates.


BOC says it comes out of solution:

http://zenstoves.net/MSDS/Acetylene.pdf

It says it comes out of solution, it doesn't say by what mechanism:

"Acetylene is shipped in a cylinder packed with a porous mass material, and a liquid solvent, commonly acetone. Acetylene is dissolved in the acetone solution [i.e., the Acetylene is a liquid] and dispersed throughout the porous medium. When the valve of a charged acetylene cylinder is opened, the acetylene comes out of solution and passes out in the gaseous form."

The last line is true -- the acetylene comes out of the solution in the form of evaporation.

Here is Princeton's view on it:

http://web.princeton.edu/sites/ehs/labsafetymanual/cheminfo/acetylene.htm

That says the same thing every post I've linked does:

"Acetylene is shipped in a cylinder packed with a porous mass material, and a liquid solvent, commonly acetone. Acetylene is dissolved in the acetone solution [as a liquid] and dispersed throughout the porous medium. When the valve of a charged acetylene cylinder is opened, the acetylene comes out of solution and passes out in the gaseous form."


Beveling an instructor knows much about the equipment is wishful thinking.

Perhaps, but they're both AWS certified professional welding inspectors, and they weld wildly better than anyone here, except maybe Torker. So, no offense Jerry, but I'd argue that they're a lot more qualified than you, or I, or Evan.

lazlo
12-15-2010, 01:16 AM
By the way Jerry, I just looked it up in my welding textbook.

From Jeffus "Welding Principles and Applications", page 737:


"The cylinder is filled with a porous material, and then acetone is added to the cylinder, where it absorbs about twenty-four times it's own weight in acetylene.

As the acetylene is drawn off for use, it evaporates out of the acetone."

http://i164.photobucket.com/albums/u15/rtgeorge_album/Jeffus.png


and a related point I made earlier:


"The withdrawal rate of gas from a cylinder should not exceed one-seventh of the total cylinder capacity per hour."

macona
12-15-2010, 01:42 AM
So then do you consider the carbon dioxide in soda water to be a liquid carbon dioxide?

Evan
12-15-2010, 01:46 AM
Evaporation is not the same thing as a gas coming out of solution. Your references are mistaken. Evaporation is a state change from liquid to gas. When a gas is dissolved in a liquid solvent it remains a gas since the molecules of the gas are not bound to each other. Since it is still a gas it cannot evaporate as it comes out of solution.

Keep it up Robert and your scientific credibility is going to drop to zero if it hasn't already.

BTW, If you are wondering what the proper term is, it is evolution, not evaporation. The dissolved gas is evolved from the solution.

metalmagpie
12-15-2010, 02:00 AM
If the space inside the cylinder is completely filled with filler material (as I believe it is) and if this filler material has the same properties regardless of orientation then why would the acetylene and acetone separate when the cylinder was on its side but not when it was standing upright? Or is there filler material right under the valve that isn't saturated with acetone, thus allowing the acetylene gas that has come out of solution to accumulate there?

OK, I'm beginning to see a picture that makes sense. Think of the filler material as sand, and think of the acetone as water. In the beginning the cylinder is filled with dry sand. Water is added. The water occupies the open space between the sand grains. Thus there is a water level inside the cylinder. The cylinder is filled until the water level is a few inches below the valve. The space between the top of the water level and the valve is 100% full of dry sand. If you tipped such an imaginary cylinder on its side, the water would fill the sand right next to the valve. If you then stood it back up, it would stand to reason that although the water would mostly run back down, the sand in the free space would still be wet and it would take some time to drain fully.

If you think of my imaginary cylinder, maybe an acetylene cylinder works the same way. If so, then the bad thing that would happen if a cylinder were opened too soon after being restored to vertical would be that acetone would be drawn out along with the acetylene. Same as if you draw out acetylene too fast.

Hmm. Starting to make sense.

metalmagpie

Evan
12-15-2010, 02:24 AM
That is approximately correct as I explained earlier. There is also powder in the acetone that has to slowly filter back down through the pores so it isn't drawn off along with the acetone. It's the powder that causes the damage by clogging and interfering with the regulator diaphragm seat.

macona
12-15-2010, 02:55 AM
There is a picture of a tank cut down the center line on this page:

http://firespecialops.com/2010/03/23/acetylene-explosion-in-il-review-tactical-considerations-for-responding-to-acetylene-fire/

darryl
12-15-2010, 03:08 AM
Well. This has been a pretty good primer on acetylene. Learn something every day.

mike os
12-15-2010, 03:35 AM
Gases in solution evolve from the solution, liquefied gases evaporate.

Acetone removal from a cylinder increases the risk of problems becasue it creates a larger space within the cylinder for the C2H2 to exist in its gaseous state, and does so at a rate far larger than the amount of acetone drawn off (24x) potentially creating higher gas pressures in the cylinder than are really safe.

C2H2 needs nothing but the correct ( or wrong;) ) pressure/conditions to explode all by itself, no source of combustion or oxidiser required. ( also forms explosive compounds with certain metals like copper.......)

Safty & use guidelines are there for a reason, please feel free to ignore them all you want... just please dont do it anywhere near me.

Black_Moons
12-15-2010, 05:22 AM
Beleving an instructor knows much about the equipment is wishful thinking. I have known instructors and inspectors that barely understand how the equipment they are welding with works, but they dont need to. The use of the equipment does not require knowing how it works and knowing isnt necessarily going to make you a better operator.

100% agreed. Your job does not determin what you know. What you know might determin your job, But that is still just wishful thinking most of the time :)

It might determin how good you are at your job, But theres a lot of people who are very poor at thier job. Even people at the top, Like cheifs of security, Presidents, Etc.

Weston Bye
12-15-2010, 06:18 AM
It appears that the original poster has come to a reasonable working understanding of the mechanics of acetylene storage and handling, the quibbling about technical minutia notwithstanding.

I wonder how, when a tank is returned for filling, the acetone level is checked before refilling with gas. I am presuming, by weight.

radkins
12-15-2010, 08:39 AM
Beleving an instructor knows much about the equipment is wishful thinking. I have known instructors and inspectors that barely understand how the equipment they are welding with works, but they dont need to. The use of the equipment does not require knowing how it works and knowing isnt necessarily going to make you a better operator.


Amen to that!, like I said earlier misconceptions abound and they often end up in print sometimes in what one might consider an "official" publication. I have been a welder for over 37 years in the mining and heavy equipment field during which time I have attended many seminars hosted by various welding and equipment suppliers plus government safety programs dealing with welding safety. Does this make me an authority on the subject(s)? No way, nor do I claim to play one on TV but there is one thing I learned beyond doubt and that is that there is so much conflicting information from these "experts" that a lot of it is in doubt. "Acetylene is heavier than air and will accumulate in low areas where it is subject to explosion", that one was presented as fact at most safety classes as well as in print in various publications but guess what? Evan corrected me when I posted that info that had been taught to me for years from "experts" and I was sure I was going to dig up this info and correct Evan instead, a bit of research showed quickly that he was indeed right and we had been given bad info all those years. That is just one example and there are several others but the point is a lot of the printed material can cause misunderstandings due to simple mis-use of terminology as well as incomplete understanding of the author so being in print does not make it gospel. Evans explanations make sense to me and indeed clear up some of the confusing and conflicting info that has been presented over the years.

lazlo
12-15-2010, 09:17 AM
Evaporation is not the same thing as a gas coming out of solution. Your references are mistaken.

Xerox: 1
Victor, Larry Jeffus, The ACC Certfied Welding Inspectors, The Pennsylvania Bureau of Mines, Valley National Gas, and the Manchester Institute of Science and Technology: 0


I wonder how, when a tank is returned for filling, the acetone level is checked before refilling with gas. I am presuming, by weight.

Yes, acetylene tanks are filled by weight.

lazlo
12-15-2010, 09:21 AM
Beleving an instructor [who's a professional Certified Welding Inspector] knows much about the equipment is wishful thinking. I have known instructors and inspectors that barely understand how the equipment they are welding with works, but they dont need to. The use of the equipment does not require knowing how it works and knowing isnt necessarily going to make you a better operator.

Amen to that!

So what are your qualifications, that you're convinced that the preponderance of technical data and instructional information is wrong? :)

I certainly don't claim superior qualifications to professional welders, and everything I've read (and posted here) supports what they taught me ;)

lazlo
12-15-2010, 09:37 AM
Why should the acetone and acetylene separate when the bottle is on its side?

Honestly, I don't know the chemistry. But Gary was correct in his description that you load the Agamassan (the porous cement) with acetone, then fill the soaked mixed with acetylene. In use, the acetylene evaporates out of the acetone/Agamassan mixture, and it works safely.

I thought about this over coffee this morning, and the explanation is quite simple: the first key point is that acetylene is filled, and stored, in liquid form. Acetylene is of course very volatile. But if you dissolve the acetylene in acetone, the acetylene/acetone solution is safe.

In normal operation, with the tank vertical, the acetone/acetylene solution is at the bottom of the tank, and the pressure in the bottle allows a fractional amount of acetylene to evaporate and flow through the valve. The acetone remains in the bottle to stabilize the remaining liquid acetylene.

When you've emptied the bottle, all the acetylene has evaporated out of the acetone/acetylene liquid, and what remains is acetone.

If you tilt the bottle on it's side, you're drawing liquid acetone/acetylene, not the evaporated acetylene. If you've done this, that's when you get the intense acetone smell, and you've probably noticed that it makes the flame a lot softer -- acetone has much lower thermal energy than acetylene.

This is also where the safety sheets warn about the acetone rotting the valve seats and hoses. But you're also removing the liquid acetone that's stabilizing the remaining liquid acetylene.

radkins
12-15-2010, 09:38 AM
So what are your qualifications, that you're convinced that the preponderance of technical data and instructional information is wrong?



Go back and read what I said, I never claimed to know more than anyone I simply said these certified "experts" gave CONFLICTING info as well as seeing conflicting info in publications, if the info conflicts then someone has to be wrong. Mis-use of terminology is apparent in some printed material if you actually look for it and it has been pointed out here a couple of times such as is the case with the term "evaporation". Since the process inside the tank is the GAS being released from Acetone and not a vapor the term evaporation simply is inappropriate but the "experts" used it anyway.

lazlo
12-15-2010, 09:41 AM
Go back and read what I said, I never claimed to know more than anyone I simply said these certified "experts" gave CONFLICTING info as well as seeing conflicting info in publications, if the info conflicts then someone has to be wrong.

All the experts, except Evan ;), are in agreement.

Everything I've posted, is in perfect agreement with the other documents. And it makes technical sense as well.


Mis-use of terminology is apparent in some printed material if you actually look for it and it has been pointed out here a couple of times such as is the case with the term "evaporation". Since the process inside the tank is the GAS being released from Acetone and not a vapor the term evaporation simply is inappropriate but the "experts" used it anyway.

Ah, you misunderstand the term "evaporation". Evaporation is a phase transition where molecules in a liquid state spontaneously become gaseous below its boiling point.

The key point here is that acetylene is stored in liquid form. The acetylene gas you're burning has evaporated from the acetone/acetylene liquid. Unless you turn the bottle on it's side ;)

moe1942
12-15-2010, 09:45 AM
The safety police will jump on even the smallest crumb.. They have a voracious appetite.:D

lazlo
12-15-2010, 09:49 AM
The safety police will jump on even the smallest crumb.. They have a voracious appetite.:D

Yeah, Jerry's cranky because he called Gary350 out out the cement filler, but Gary's description was absolutely correct, including the way the liquids are loaded into the cylinder.

This was fun, time for some shop time. Got an acetyelene bottle that's been laying on it's side overnight :D

John Stevenson
12-15-2010, 09:55 AM
This was fun, time for some shop time. Got an acetyelene bottle that's been laying on it's side overnight :D

Torch it open to see if it's got any cement filler in it :D

Peter.
12-15-2010, 10:03 AM
What, like this guy did?

http://peterrimmer.myby.co.uk/images/wrong_wrong_wrong.jpg

lazlo
12-15-2010, 10:04 AM
Torch it open to see if it's got any cement filler in it :D

I might as well. As I mentioned to several of the Austin members in person -- someone stole the oxygen bottle off my O/A cart last Wednesday night.

In the middle of the night, someone came by, cut the strap holding the two bottles together, and swiped the oxygen bottle. They left the regulators, the acetylene bottle, the cutting torch, and the freaking cart.

Why wouldn't you just roll off the whole cart?! :rolleyes:

By the way, if you hang out on the Hobart WeldTalk forums (excellent, by the way, a lot of regulars from here and PM), once in awhile you'll see pictures of some Rocket Scientist cutting open an acetylene bottle. I wonder what percentage of those guys hit the local news first :)

Edit: Peter beat me to it.

TGTool
12-15-2010, 10:14 AM
Sounds like a contract theft. I heard about someone who lost their Corvette transmission to thieves. The thieves took off the linkage and left it with the car because that wasn't part of the contract. Who say's there isn't honor among thieves?

radkins
12-15-2010, 10:20 AM
Ah, you misunderstand the term "evaporation". Evaporation is a phase transition where molecules in a liquid state spontaneously become gaseous.



Gas and vapor are not exactly the same thing and Acetylene is released from Acetone in the tank as a gas thus the term eVAPORation, evaporation

Merriam-Webster,
www.merriam-webster.com/dictionary/evaporation

A few more

www.brainyquote.com/words/ev/evaporation162073.html

www.thefreedictionary.com/evaporation

www.yourdictionary.com/evaporation





Again this is a perf3ect example of the conflicting info I have been talking about.

gnm109
12-15-2010, 10:24 AM
Sounds like a contract theft. I heard about someone who lost their Corvette transmission to thieves. The thieves took off the linkage and left it with the car because that wasn't part of the contract. Who say's there isn't honor among thieves?


That's probably the case. In California and probably other states they passed a law that auto wreckers may no longer sell used calalytic converters. This was a part of the California EPA compliance program.

This had some unintended consequences. Now, there are criminals who go out and steal catalytic converters to order. They have the tools to lift the vehicles, cut the converters out and then leave. It takes them about three minutes start to finish.

In Sacramento recently a couple of crooks were caught with an entire truckload of stolen converters. Presumably, these are stolen to order for crooked repair shops who install them and charge the unsuspecting customers for new parts. Sweet.


.

lazlo
12-15-2010, 10:32 AM
Gas and vapor are not exactly the same thing and Acetylene is released from Acetone in the tank as a gas thus the term eVAPORation, evaporation

Again this is a perf3ect example of the conflicting info I have been talking about.

It's not conflicting information. You need to crack-open a high-school science textbook :)

Evaporation is one of two forms of vaporization.

http://en.wikipedia.org/wiki/Evaporation


"Evaporation is a type of phase transition; it is the process by which molecules in a liquid state spontaneously become gaseous. Generally, evaporation can be seen by the gradual disappearance of a liquid from a substance when exposed to a significant volume of gas."

http://www.sciencedaily.com/articles/e/evaporation.htm


"It is the process whereby atoms or molecules in a liquid state (or solid state if the substance sublimes) gain sufficient energy to enter the gaseous state."

http://www.cpc.noaa.gov/products/outreach/glossary.shtml


"Evaporation

The physical process by which a liquid or solid is changed to a gas; the opposite of condensation."

lazlo
12-15-2010, 10:36 AM
Sounds like a contract theft.

Wow, never heard of that.

I live in an upscale Yuppie neighborhood -- my neighbors wouldn't know a gas bottle if you dropped it on them.

But I noticed that the nylon loading strap holding the bottle to the cart was cut with a razor-sharp knife.

I called the local welding suppliers and told them to look out for a moron trying to sell an oxygen bottle without knowing anything about welding. They couldn't do anything more than hassle him, but no point in making life easier for him.

Lew Hartswick
12-15-2010, 11:49 AM
It's sort of amazing that so many people use as a refrence for
definitions some other field of endevor. ie. for a chemical term I'd
suggest going to a Chemist not a "how to text book on welding".
There are a lot similar examples floating around on this group.
...Lew...

radkins
12-15-2010, 12:04 PM
It's sort of amazing that so many people use as a refrence for
definitions some other field of endevor. ie. for a chemical term I'd
suggest going to a Chemist not a "how to text book on welding".
There are a lot similar examples floating around on this group.
...Lew...


That is exactly the point I have been trying to make and the conflicting information and use of terminology in some printed material is all the more reason to use a more specific source for a reference for any given process, such as in this case releasing of dissolved Acetylene inside a tank.

Evan
12-15-2010, 12:08 PM
Everything I've posted, is in perfect agreement with the other documents. And it makes technical sense as well.

It's not conflicting information. You need to crack-open a high-school science textbook

Take your own advice Robert. I am sure it exceeds 97.1 degrees Farenheit in Texas from time to time. Above that temperature acetylene cannot be made liquid no matter how high the pressure. 97.1 F is the critical temperature of acetylene. The critical pressure of acetylene is 907 psi. Acetylene bottles are filled to no more than 250 psig so that the acetylene will not undergo a phase transition even at much lower temperatures.

The acetylene is never in a liquid state in an acetylene bottle, even at lower temperatures. Therefore, it cannot evaporate.

Why is the acetylene not wanted in a liquid state? Because it then becomes shock sensitive to the same degree as liquid nitroglycerine.

lazlo
12-15-2010, 12:15 PM
The acetylene is never in a liquid state in an acetylene bottle, even at lower temperatures. Therefore, it cannot evaporate.

From OSHA (but they probably know less than Xerox):

http://www.c-f-c.com/specgas_products/acetylene.htm


OSHA standard, 1910.253(b)(3)(ii) says,

Acetylene is a compressed gas that is used as a fuel and is stored in a liquid state. When the valve is opened and pressure is released a portion of the liquid turns to gas. This gas is then used by the device that the cylinder is connected to. Because acetylene is stored as a liquid, the cylinder will only work properly if the tank is used in the upright position. Using, or storing, the tank in any other position can be extremely dangerous. According to the U.S. Department of Labor General Industry
Digest, 1994 (Revised):

lazlo
12-15-2010, 12:18 PM
It's sort of amazing that so many people use as a refrence for definitions some other field of endevor. ie. for a chemical term I'd
suggest going to a Chemist not a "how to text book on welding".

Yes, but in this case, the welders, OSHA, the Bureau of Mine Safety, Victor, and the chemists are all using the same terminology.

Evan's just in a twist because he didn't realize the acetylene is stored in the bottle in liquid form. Ironically, that's the whole reason you don't want to tip the bottle over on it's side...

Evan
12-15-2010, 12:33 PM
Evan's just in a twist because he didn't realize the acetylene is stored in the bottle in liquid form.

Sorry Robert, acetylene is never in a liquid state in an acetylene gas welding bottle.



Handbook of compressed gases By Compressed Gas Association

http://ixian.ca/pics8/acetylene.jpg

http://www.cganet.com/

From OSHA




1910.253(a)(2)
Maximum pressure. Under no condition shall acetylene be generated, piped (except in approved cylinder manifolds) or utilized at a pressure in excess of 15 psig (103 kPa gauge pressure) or 30 psia (206 kPa absolute). (The 30 psia (206 kPa absolute) limit is intended to prevent unsafe use of acetylene in pressurized chambers such as caissons, underground excavations or tunnel construction.) This requirement is not intended to apply to storage of acetylene dissolved in a suitable solvent in cylinders manufactured and maintained according to U.S. Department of Transportation requirements, or to acetylene for chemical use. The use of liquid acetylene shall be prohibited.


http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=9854


Regardless of the multiple misuses of the term liquid by the various googlefacts you dredged up you still need to explain how acetylene gas is able to undergo a phase change by being dissolved in a solvent while below it's critical pressure. That is impossible according to the known laws of physics.

Peter.
12-15-2010, 12:40 PM
Just because a safety bulletin is produced by a well-regarded authority, dosn't mean it's 100% technically correct, or even needs to be. My experience with safety briefing documents produced by safety councils and designed to be understood by people with a wide range of level of education is that the details often lean more towards ease of transmission and understanding than technically perfect information. I've seen it many times in my industry and that is the reason given whenever I've pointed out an inaccuracy.

The slightly formal wording of that passage and lack of technical terminology marks it as possibly one such document. All they need to convey to the recipient is that if the bottle is stored or used horizontally, liquid will come out and saying that the gas is stored as a liquid is accurate enough for that whether it's true or not. If someone who had been briefed some time before forgot about it and used a bottle on it's side, the liquid acetone coming out would be the reminder that person needed to stand the bottle upright. They don't care nor need to know whether the acetylene was evolved or evaporated.

Evan
12-15-2010, 12:48 PM
Quite so. However, it also means that if you take the information in such a document to inform yourself on the actual physics you risk being misinformed. Robert knows better but cannot bring himself to admit that he is now in a very deep hole with no way out.

lazlo
12-15-2010, 12:53 PM
Regardless of the multiple misuses of the term liquid by the various googlefacts you dredged up

Unlike you Evan, I wasn't educated on Wikipedia. I wanted to learn welding, so I went to the best welding school in Central Texas. Most of those citations are my class handouts, and quotes from my textbook.


Sorry Robert, acetylene is never in a liquid state in an acetylene gas welding bottle.

So now you can't read? :eek:

OSHA standard, 1910.253(b)(3)(ii)

Acetylene is a compressed gas that is used as a fuel and is stored in a liquid state. When the valve is opened and pressure is released a portion of the liquid turns to gas. This gas is then used by the device that the cylinder is connected to. Because acetylene is stored as a liquid, the cylinder will only work properly if the tank is used in the upright position. Using, or storing, the tank in any other position can be extremely dangerous.


[Quoting the same section of the OSHA manual on acetylene safety that I quoted above]

The use of liquid acetylene shall be prohibited.

Of course that's true! Igniting liquid acetylene would cause a very large explosion!

Evan
12-15-2010, 01:07 PM
You haven't a leg to stand on Robert. How about stopping with the GOOGLE-FACTS and addressing the science?

Explain how a phase change may occur when a gas is becomes a solute in a solvent. I await your next round of Wikiquotes, if you can find any that support your mistaken position. I doubt it.


Unlike you Evan, I wasn't educated on Wikipedia. I wanted to learn welding, so I went to the best welding school in Central Texas. Most of those citations are my class handouts, and quotes from my textbook.


I have heard that education in the US is in a sorry state. You are proving it.

Evan
12-15-2010, 01:18 PM
A suggestion: Start with the Ideal Gas laws that you apparently are not familiar with. If the acetylene in the cylinder were a liquid the pressure would not drop as the the gas is withdrawn until no liquid remains.

radkins
12-15-2010, 01:45 PM
Probably a mistake but here goes anyway. I would assume, and already did before this discussion even started since I was already aware that Acetylene was not stored as a simple liquid itself inside the tank, that the OSHSA statement referring to the liquid was the Acetone containing the dissolved Acetylene. Thus Acetylene is stored in the tank dissolved in a liquid but it itself is not in a liquid form.

ligito
12-15-2010, 01:48 PM
"The cylinder is then filled with Acetone.

Next it is filled with Acetylene."

If it is full of Acetone, how can you fill it with Acetylene?
If it's full, how do you get more into the cylinder?
Just asking.

BTW, Isn't Acetylene the bi-product of Carbide and water?

lazlo
12-15-2010, 02:00 PM
Probably a mistake but here goes anyway.

Yes, Evan does this with most of the threads he jumps into.


I would assume, and already did before this discussion even started since I was already aware that Acetylene was not stored as a simple liquid itself inside the tank, that the OSHSA statement referring to the liquid was the Acetone containing the dissolved Acetylene.

Correct. As I posted earlier, the Nobel Laureate Nils Dalén discovered that acetylene is highly soluble in acetone, and that the liquid acetone/acetylene solution we've been arguing about for 10 pages is very stable.


Thus Acetylene is stored in the tank dissolved in a liquid but it itself is not in a liquid form.

The tank contains liquid acetone/acetylene mixture. When the pressure is dropped by cracking the valve, the acetylene evaporates out of solution, and the acetone remains.

When you get your tank refilled, they weigh the tank to calculate the amount of acetone remaining. The DOT markings on the tank indicate how much acetone it should contain, by weight.

It's critical that there's enough acetone in the tank to absorb all the acetylene into solution, since the unabsorbed acetylene is highly volatile. So if you've managed to draw-off some of the acetone, they'll top it off first, and then add the acetylene.

In short, it's the exact same process as liquid propane or CO2: under pressure it liquefies, and when you crack the valve, the gas evaporates out.

lazlo
12-15-2010, 02:05 PM
"The cylinder is then filled with Acetone.

Next it is filled with Acetylene."

If it is full of Acetone, how can you fill it with Acetylene?

Good question. "Filled" as in adding a specific volume of liquid. You need a specific amount of liquid acetone to absorb the acetylene, as I noted above.

According to the Bureau of Mines, that's 42% acetone to 36% acetylene:

http://i164.photobucket.com/albums/u15/rtgeorge_album/acetylene1.jpg

macona
12-15-2010, 02:08 PM
The gas is stored between molecules of acetone. There are methods of storing hydrogen in much the same way.

Acetylene is made from Calcium Carbide and water. The reaction creates acetylene gas (C2H2) and lime.

radkins
12-15-2010, 02:18 PM
The tank contains liquid acetone/acetylene mixture. When the pressure is dropped by cracking the valve, the acetylene evaporates out of solution, and the acetone remains.


In short, it's the exact same process as liquid propane or CO2: under pressure it liquefies, and when you crack the valve, the gas evaporates out.



I would not consider Acetylene dissolved in liquid Acetone to be liquid Acetylene anymore than I would consider dissolved CO2 to be liquid CO2 in a bottle of soda, I hardly think a bottle of soda contains liquid CO2. Also the process by which CO2 is being released from it's dissolved state in the soda, much like Acetylene being released from it's dissolved state in the Acetone, hardly fits the description of "evaporation".

lazlo
12-15-2010, 02:35 PM
I would not consider Acetylene dissolved in liquid Acetone to be liquid Acetylene

I didn't say it was. What I, and OSHA, and everyone else say is that acetylene is stored in liquid form, in a chemical solution with acetone. The official OSHA/DOT/CGA designation is a "dissolved gas".


"Acetylene is a compressed gas that is used as a fuel and is stored in a liquid state. "


Also the process by which CO2 is being released from it's dissolved state in the soda, much like Acetylene being released from it's dissolved state in the Acetone, hardly fits the description of "evaporation".

It's exactly evaporation: which is why all the welding/OSHA/chemistry citations refer to the acetylene evaporating out of the solution. If you Google "CO2 evaporates" I'm sure you find thousands of citations describing soda :)

By the way, the Manchester University laboratory safety document I was quoting:


”As the acetylene evaporates from the acetone solution, and passes out of the reducing valve it warms slightly as the Joule-Thompson coefficient is negative ..."

...is referring to the fact that acetylene is unique in that it heats-up as it expands. Almost all gases except hydrogen, helium, neon and acetylene cool upon expansion. That makes rapid de-pressurization of acetylene especially dangerous.

radkins
12-15-2010, 02:35 PM
BTW, Isn't Acetylene the bi-product of Carbide and water?


Yep, you got it. :)

When I was a kid there were still miners who used carbide lamps even though by that time they had long since been outlawed, heck even the mines these "wildcat miners" worked in were illegal! Back then most of the little country stores had large blue cans of "Union Carbide" brand calcium carbide, since the lamps were commonly used as flashlights by others besides the miners they would sell it by the bag full to lots of people. We as kids would buy 5 or 10 cents worth at a time, they would just scoop it up and into a brown paper bag and off we would go to see what we could blow up! :D A very popular "toy" was a can with a snug fitting lid and a small hole in the bottom, toss in 3 or 4 grains of carbide, spit on it and stick a match to the hole and-BOOM! The object was to see who could shoot his lid the farthest. As kids we did not have play stations, video games or such but we had fun anyway even if that kind of fun would horrify most parents (me included now) these days.

mike os
12-15-2010, 02:51 PM
nope... evaporation is a state change, the CO2 in cola is exactly the same process of storage and recovery.....just different gasses and liquids

George Bulliss
12-15-2010, 02:57 PM
nope... evaporation is a state change, the CO2 in cola is exactly the same process of storage and recovery.....just different gasses and liquids

All this talk of evaporation has driven me to a state of exasperation. I think this thread has outlived its usefulness.

George