Re: At what PSI does a plastic soda bottle explode? (home CO2 carbonation)

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Elmo

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Apr 8, 2010, 2:12:08 AM4/8/10
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On Wed, 7 Apr 2010 22:48:15 +0000 (UTC), Don Klipstein wrote:

> show soda bottles being blown up by an air compressor
> and apparently also by a bike pump.

Interestingly, the only time the cap failed was when they heat treated the
coke bottle beforehand, as shown in in these tests:
http://home.people.net.au/~aircommand/procedures.htm

Interestingly, in general, the larger the bottle, the lower the burst
pressure.

For example, while the standard 2 liter coke bottle with label burst at 168
psi, the standard 1.25 liter coke bottle burst at 185 psi.

Also interesting was the more gas (less liquid), the higher the burst
pressure; for example, that same 1.25 liter coke bottle burst at 190 psi
when it contained significant air.

In their last reported test, a 2 liter PET bottle failed at a lower psi
than you'd expect (150 psi) after simulated use (held at 130 psi for 3
minutes). This test might indicate plastique fatigue occurs with repeated
high pressurization.

So, I'd say Coke's report that all their bottles can handle 150 psi seems
reasonable as the MOP (maximum operating pressure) for PETE bottles.

BTW, those numbers are all way higher than the "guesstimates" made here:
http://www.instructables.com/answers/how_much_psi_does_a_coke_bottle2l_hold/

Elmo

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Apr 8, 2010, 3:06:54 AM4/8/10
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On Thu, 8 Apr 2010 06:12:08 +0000 (UTC), Elmo wrote:

> So, I'd say Coke's report that all their bottles can handle 150 psi seems
> reasonable as the MOP (maximum operating pressure) for PETE bottles.

Despite both Coke's statements and independent tests showing coke bottles
exploding well almost at 200 psi, the mythbusters seem to intimate they
explode at the much lower 150 psi pressure.
http://en.wikipedia.org/wiki/MythBusters_%282005_season%29

So, I'm confused.

Elmo

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Apr 8, 2010, 3:53:55 AM4/8/10
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On Wed, 7 Apr 2010 12:25:50 -0700 (PDT), harry wrote:

> If you are pressure testing bottles, on NO account use air or gas, the
> bottle will explode violently at some point.

This reference backs up the observation that the smaller bottles rupture at
higher pressures ...
http://answers.yahoo.com/question/index?qid=20070609125950AAdiFbU

5 atmospheres is about 73.5 psi. I know that 16 ounce plastic coke bottles
are rated up to 175psi(11.9 atm). 2L bottles hold somewhat less. A coke can
holds about 100 psi(6.8atm). I don't know the rating of champagne bottles
but that the thick glass can withstand a marginally greater pressure than
the thin plastic. However the plastic will begin to stretch (audiblly) as
it nears failure and the glass will just shatter and send shards
scattering. I prefer the plastic.
Source(s):
The Coca Cola people told me... and I've also test popped a few first hand
as a demonstration as to ability of expanding gas to do work using liquid
nitrogen source in the capped bottles.

The coca cola contact is :
Gina M. L'Heureux
The Coca-Cola Company
Industry and Consumer Affairs

This answer, way too conservative, at least shows a mathematical process:
http://answers.yahoo.com/question/index?qid=20061204051635AAoQDT9

Best Answer - Chosen by Voters
You would have to do a bit of research: You need to know the dimensions of
the bottle: Diameter and wall thickness.

You need to know the plastic it is made from and the corresponding tensile
strength (yield) of the material. Then you can update these calculations:

Assuming that the diameter of the bottle D=5 inches, wall thickness t =
0.025 inches, and the plastic has a yield strength of 5000 psi:

The hoop stress in the wall of the bottle = PD/2t
The longitudinal stress in the wall = PD/4t

For this pressure vessel situation, those 2 stresses are orthogonal and and
the principal stresses s1 and s2, the von mises failure theory suggests
that the stress levels are acceptable if: sqrt(s1^2 - s1*s2 +s2^2) < yield,
so:

sqrt((PD/4t)^2 - (PD/4t)*(PD/2t) + (PD/2t)^2) < 5000

expanding and collecting the LHS =>

0.433 P D / t < 5000

Filling in the example numbers, P < 57.7 psi

And ofcourse with anything safety related, a safety factor should be
applied in proportion to the risk severity. In this case an exploding
bottle probably would not cause death, but could cause serious injury - A
safety factor of 5 is likely appropriate... thus, assuming the example
numbers are about right, you should not pressurize to more than 57.7/5 =
11.5 psi (this is delta compared to 1 ATM)

But, of course, these guys are the most reliable I can find:
http://home.people.net.au/~aircommand/procedures.htm

Ecnerwal

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Apr 8, 2010, 8:47:41 AM4/8/10
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When the kiddies were into bottle rockets (water and air type, not the
pyrotechnic type) they were running 2 liters up to 160 psi regularly.
After a few trips it made a Very Loud Noise. But until then it held, and
the landings probably didn't aid structural integrity any (dents,
creases, scratches.) Then again, it may have been simple fatigue.

Your home carbonation system can benefit from the science that aids the
engineering of commercial carbonation systems - chill the liquid - it
dissolves gas better at lower pressures. Since you can keep the
pressures lower, so you are not stressing things as much. Wasting
product on the floor is messy and irritating, not to mention loud and
attractive to ants, etc.

--
Cats, coffee, chocolate...vices to live by

Tegger

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Apr 9, 2010, 8:10:31 AM4/9/10
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Elmo <dcdraf...@Use-Author-Supplied-Address.invalid> wrote in
news:hpjvad$35o$1...@tioat.net:

Explosion occurs at 150psi.

I think your confusion comes from some poor wording at that Wiki site.

This quote:
"The Build Team also found that water cooler jugs, while able to launch
higher at the standard air/water ratio for water bottle rockets, were
weaker than standard soda bottles (which are designed to hold carbonated
liquids), failing at around 60 psi (413 kPa) less than the soda bottles
(90psi (600kPa) as opposed to 150psi (1000kPa))."

might read more clearly as:
"The Build Team also found that water cooler jugs were able to launch
higher at the standard air/water ratio for water bottle rockets. However,
the jugs were weaker than standard soda bottles, failing at around 90 psi
(600 kPa), much less than the soda bottles, which fail at 150psi
(1000kPa)."

The intermixing of English and Metric also adds to the confusion of the
Wiki page's wording.


--
Tegger

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