Sciencemadness Discussion Board

Shell Shock: Play it safe

smuv - 29-12-2008 at 23:55

I had a very scary chemistry related experience earlier today. Using an apparatus I made to pressurize various bottles, I pressurized a 500ml Kimax bottle. I had previously pressure tested a different bottle of the same model to 110 psi; It was able to maintain this pressure continuously without yielding.

As I slowly increased the pressure of the second bottle, just as the guage registered 110psi (the max of my regulator), the bottle shattered with a deafening bang, causing my ears to ring and sending glass shards everywhere (they were quite small pieces too, not as I expected the bottle to fail).

This experience was very scary for me, although I was uninjured. I stupidly took much fewer precautions while filling the second bottle; because I had tested the other bottle, and up until that point, I had tested many other bottles with no failure at 110psi.


Play it safe everyone...and count your blessings.

Also, I would recommend never to use a pressure vessel in a reaction at any more than .5x the maximum pressure you tested it.

[Edited on 12-30-2008 by smuv]

bquirky - 30-12-2008 at 01:14

Glass bottles at 110 Psi !!! :o


Id be wary about presurising any glass bottle beyond 1 atm any little piece of grit or defect caused by previous spot heating or anything like a scratch can create a stress points

Plastic still go's pop but it wont spray glass everywhere.

You can make your own vesles out of PVC pipe if you don't nead to heat it too much they have the advantage of being properly rated for a given pressure and cheap !

http://www.engineeringtoolbox.com/pvc-cpvc-pipes-pressures-d...
gives you some numbers.

good luck !

JohnWW - 30-12-2008 at 03:41

What pressure occurs in bottles used to contain carbonated beverages, in which CO2 is foced into the drink under pressure when bottling? And what about the pressure due to CO2 in bottles of champagne, in which the fermentation of the grape juice is completed only after it is bottled?

[Edited on 31-12-08 by JohnWW]

bquirky - 30-12-2008 at 04:22

Its an interesting question

according to http://hypertextbook.com/facts/2000/SeemaMeraj.shtml
soft drink bottles are various pressures around 300kpa (~42psi)

My home brew beer keg on a CO2 bottle runs at about 200kpa (28psi) for a normal head of beer


http://hypertextbook.com/facts/2003/PeterHui.shtml
quotes 60-90 psi for a Champagne bottle


sounds to me like an excuse to aquire a taste for high presure french beverages ;)

bquirky - 30-12-2008 at 04:26

I just had a thought Im not sure if it makes a difference.

but on the surface it would seem that a bottle full of air at a given pressure would make a better bang than one that was at the same pressure but only had a few cc's of gas

hissingnoise - 30-12-2008 at 05:03

Quote:
Originally posted by bquirky

A bottle full of air at a given pressure would make a better bang than one that was at the same pressure but only had a few cc's of gas.


What are you on about?
And how can one bang be "better" than any other bang?
Better for what?

smuv - 30-12-2008 at 05:06

I would say that a Champagne bottle would have a burst pressure of 200+ psi based upon what I have seen of glass bottles around this size. I would be weary to use non-borosilicate glass in any exothermic or heated reaction though, as thermal stresses could easily crack the bottle.

@Hissingnoise better = louder I believe. The failure of the empty bottle sure was loud!

[Edited on 12-30-2008 by smuv]

bquirky - 30-12-2008 at 07:00

:)

pardon my warped humor, by better I facetiously meant more dangerous


my line of thinking was that since gas is compresable given two identical bottles at the same pressure one full of a liquid and the other with no liquid and only gas.

The bottle containing the grater volume of compressed gas would contain more energy and hence produce a 'better' bang :)

despite the fact that they are both the same size and at the same pressure.

hissingnoise - 30-12-2008 at 07:20

I get it! More bang for your psi. I've already damaged one (my own) eardrum. . .

hissingnoise - 30-12-2008 at 07:38

Wouldn't the smaller volume of gas need a higher pressure to rupture the container?

hissingnoise - 30-12-2008 at 08:05

My physics isn't great this time of year---I should, perhaps, retract the question.

hissingnoise - 30-12-2008 at 08:13

On further thought, bquirky, both bangs should be equally loud, I, er, think. . .

Mr. Wizard - 30-12-2008 at 09:06

Hydrostatic testing of containers is the normal method if testing for pressure. A relatively non compressable liquid is used, such as water. When the container, pipe, or hose fails, only a small amount of noise or energy is released, because the compression of the liquid and container only stores a small amount of energy. Avoid any air or gas spaces in a container under test. They store energy and make a failure louder and more dangerous. I have tested 40 gallon homemade tanks with a small hand operated pump designed for the purpose. The dispacement of the pump is very small, with the piston diameter of only about 1/4" (6 mm). The pump could easily reach 500 psi. You can easily and quickly reach this pressure IF there was no air bubble in the tank. If there was air in the tank it takes forever to pump any pressure. You then know to remove the air.

To sum up, use a safety shield and eye protection. Use water and avoid compressed gas pockets or volume. If you do not have a pump and must use compressed air to raise the pressure on the liquid filled container, use a very small narrow line that will only cause a slight amount of air to flow if the test fails. Wrap the tested container in a towel or fabric, using many layers. Don't use a gas that dissolves in the liquid.

There is absolutely no reason to stand next to a container when you are pressure testing it.

The more compressed air the more the danger, and the louder the bang.

[Edited on by Mr. Wizard]

hissingnoise - 30-12-2008 at 09:22

Quote:
Originally posted by Mr. Wizard

The more compressed air the more the danger, and the louder the bang.



Yes, but won't identical containers fail at the same pressure and produce an equal racket?

DJF90 - 30-12-2008 at 09:40

You can't guarentee identically made containers will have exactly the same mechanical properties. Therefore there may be a small variation in the max. pressure of a set of identical bottles, but they will generally fail at approximately the same pressure (as the mechanical properties shouldn't vary that much).

bquirky - 31-12-2008 at 08:47

Being new years I had a bottle (or 3) of champaign tonight !

and had a close look at the bottle. the glass is very very thick compared to most other glass bottles and the shape of the curves seems to be be very um.... deliberate ?

The bottom of the bottle is indented with what appears to be a perfect parabolic cone such that the glass at the base appears to be mostly under compression, all of the bottles that i saw had a very similar shape to the wide shoulder coming up to the neck. a very large radius curve perhaps to avoid stress points ?

when im cleaning tomorow i can crack one open andmesure the thickness of the glass at various points.

im still not lining up to pump one up too much though :)



lets hope the global financial crisis distracts people from terrorists in sheds with compressed air vestles and we all have a good 2009 !!


regards.
*hic*

MagicJigPipe - 31-12-2008 at 21:07

"A bottle full of air at a given pressure would make a better bang than one that was at the same pressure but only had a few cc's of gas."

I saw your second explanation. At first I thought you meant something like:

A bottle is filled with ~ .5g of a nitrogen and heated until bursting pressure. Let's say 100psi. Then a bottle with 1g of nitrogen was heated to the same bursting pressure. Would the 1g bottle make a "bigger bang"?

Is that what you were getting at? My guess would be 'yes' because you have more mass escaping the bottle. Of course the bottle with .5g would have to be heated to a greater temperature which might cause more failures in the glass but...

Anyway, it seems verging on subjectivity to me.

crazyboy - 31-12-2008 at 21:32

Quote:
Originally posted by MagicJigPipe

A bottle is filled with ~ .5g of a nitrogen and heated until bursting pressure. Let's say 100psi. Then a bottle with 1g of nitrogen was heated to the same bursting pressure. Would the 1g bottle make a "bigger bang"?

Is that what you were getting at? My guess would be 'yes' because you have more mass escaping the bottle. Of course the bottle with .5g would have to be heated to a greater temperature which might cause more failures in the glass but...



I think you are wrong. assuming identical conditions but different volumes of gas the container will rupture at the exact same pressure 100psi it will just take less time in the one with more gas.

Since they both explode at 100psi and explosive power is caused by a difference in air pressure the effect will be the same regardless of the amount contained as long as pressure and container remain constant.

If 5g gas explodes in a flask at 1000psi it will be 10 times as powerful than any amount of gas in an equal sized container exploding at 100psi.

Think of it this way. If you have a bottle and heat it up just a bit then hit it it won't really explode. but take the same bottle same amount of gas and heat it up a lot then hit it it will explode quite violently right?

MagicJigPipe - 31-12-2008 at 21:49

Yes, you are right. Shame on me...

It would explode with the same force because you are putting the same amount of "potential energy" (net) into both. The potential energy at first is caused by the original pressure. Right?

[Edited on 12-31-2008 by MagicJigPipe]

Nevermore - 1-1-2009 at 01:06

many champagne or a champenous bottle has been tested by me to be completely safe up to 6 atm, the cheaper one are very thin and possibly can't reach this pressure but i didnt test them.

smuv - 1-1-2009 at 11:18

@Mr. Wizard: Filling the bottle with water is very good advice, I wish I had thought of that.

I was not standing next to the bottle, it was behind a barrier. However, during previous tests I took greater precautions and wrapped the bottle with some old carpet. What was so shocking to me, was not that the bottle failed, but the amount of energy which was released, which I had greatly underestimated.

One thing interesting about the way the bottle failed was there were no large pieces, the largest piece was maybe 1.5 in^2, which is not as I expected the bottle to fail. Most of the pieces were much smaller though, and I had a hell of a time cleaning up the mess.

Ozone - 1-1-2009 at 13:39

Happy new year.

I am glad your OK.

IIRC, the converse and a relevant discussion can be found here:
http://www.sciencemadness.org/talk/viewthread.php?tid=11616&...

O3

vulture - 2-1-2009 at 01:44

Quote:

A bottle full of air at a given pressure would make a better bang than one that was at the same pressure but only had a few cc's of gas.


That's physically impossible. If you have two identical bottles at the same pressure and temperature they also have the same amount of gas inside.

hissingnoise - 2-1-2009 at 04:01

I think bquirky meant that the second bottle would have in it a large volume of incompressible liquid and a small volume of air.
What would happen when both bottles were fed with air at a high compression is the question, I think.
Takes figuring, or I'm missing something. . .

bquirky - 2-1-2009 at 05:40

Physical impossibility only means there is a hidden variable :)


Yes hissingnoise that is what i ment, same sized bottles, same pressure one contains some incompressible fluid :)

its my contention that the bottle with the larger amount of gas is more dangourus because it contains more stored energy despite the fact that they are at the same pressure.

hissingnoise - 2-1-2009 at 06:17

But the (stored) energy required to effect rupture, if both bottles are identical, should be equal in either case.
The smaller gas-volume above the water would then, I think, need to be more highly compressed than that in the first container. . .
I'm just guessing!

MagicJigPipe - 4-1-2009 at 22:26

No, because the liquid would be pressing on the glass the same amount as a gas would; so the same amount of pressure would burst both bottles.

hissingnoise - 5-1-2009 at 06:05

As I said, I'm just guessing here, but you're essentially saying that any small volume of compressed gas over any large volume of incompressible fluid can rupture a container just as any large similarly compressed gas-volume can?
You may well be right, but how sure are you, MagicJigPipe?

DJF90 - 5-1-2009 at 06:38

Thats not what he's saying, but that is also correct. The incompressible fluid is also pressing on the vessel, and when the failure pressure is reached, a vessel containing only incompressible fluid will also rupture. Hydrostatic testing is preferred because if the vessel does rupture, then the expansion of the incompressible fluid is minimal. However if a gas was present then it will vastly increase in volume as the pressure is relieved, essentially exploding the vessel.

hissingnoise - 5-1-2009 at 07:20

Thanks DJF90, the penny's dropped.
Note I wasn't trying to contradict anyone, despite how it looks.
You made me remember how ice can rupture a bottle without exploding.
It makes sense now. . .

Might as well show a picture of the thing...

smuv - 7-1-2009 at 19:27

Here is the apparatus. Its not exotic or beautiful, its only purpose was to pressure test bottles of various sizes; so far it has been very successful.

Warning: I hope anyone who attempts similar work exercises due caution. Always, pressure test bottles filled with water (at the temp you wish to operate the device). Additionally, only operate experiments at half the highest tested pressure of the particular bottle. Finally, always expect that the bottle will explode and plan accordingly.







Things which have changed since the pictures were taken
*The tubing was replaced (after it yielded) w/ automotive fuel line for carburated vehicles, which is fairly cheep, tolerant of high temps and good to ++200psi (at high temps).
*The natural cork was replaced with synthetic (the solid rubbery type, not the foamy w/ plastic veneer); the natural cork leaks appreciably at almost any pressure, the synthetic did not leak.

Some details about construction
*4mm threaded rods; countersunk washered locknuts on bottom.
*Top piece is scrap oak wood flooring; it has a fancy notch cut into it (somewhat visible in both pictures) to allow the barb to fit through while still maintaining good contact w/ cork
*The stopper piece consists of a hose barb soldered to a piece of 3/8 inch (IIRC) copper tubing which has a US nickel drilled and soldered to it (the idea is the pressure pushes the stopper against the nickel to create a better seal; no idea if this helps at all).
*The gauge you see in the picture has a valve obscured from view which is nice for slowly filling the bottle.

Things I would change
*I would use the thin (but very strong) oak flooring for the bottom piece, as magnetic stirring is weakish through the thick piece of wood.
*I should have drilled through both the top and bottom pieces at the same time so they lined up a little better (not a big deal though)

nitric - 15-4-2009 at 08:39

ive had a experience when i was younger with trying to make a hydrogen torch( idiotic to the max :o ) with a peizoelectric sparker, peice of lithium, and a glass funnel. i put the peice of lithium in the bowl of water and quickly covered it with the funnel, then with a face mask and welding gloves, put the sparker end of the peizo to the flow spot of the funnel and sparked it. The funnel flashed up, then exploded with a deafening noise :o . after that i was in shell shock for about a week then back to normal.