# Implosion Risk Assesment



## Grasshopper (Mar 28, 2013)

Reading threads concerned with the risk of implosion of a carboy under vacuum, most recently the threads on vacuum degassing, I am left with the impression that some people may not be thinking about this risk correctly. Specifically, some comments suggest that implosion risk can be significantly reduced by decreasing the vacuum from 25 inches of Hg to 20 inches and that the risk can be further reduced by pulling vacuum only on a carboy full to the shoulder with liquid. With the caveat that I might not be looking at this correctly either, let me offer my thoughts.

It is not the vacuum on the inside of the carboy that can cause failure but the higher pressure on the outside pushing in. The driving force for failure is the differential pressure across the walls (the delta P). For ease of calculation, I am going to approximate the atmospheric pressure at 15 psi and full vacuum at 30 inches of Hg in construction of the following table.

.....Vacuum.............Inside Pressure............Delta P 
.... 30 (in. Hg)........... 0 (psi).................. 15(psi)
.... 25 ..................... 2.5 ..................... 12.5
.... 20 ..................... 5 ........................ 10

Thus we see that the difference in force across the walls of the carboy from 25 to 20 inches vacuum is not that large, 12.5 psi vs. 10 psi and that there is not all that much difference between full vacuum and 20 inches (15 vs. 10). Thus, if there is a significant risk of implosion at full vacuum, we shouldn’t feel all that comfortable at 20 inches. Unless we know from experimental data or reliable calculations what the failure point is likely to be, we really have no idea how comfortable/uncomfortable we should be. If the failure point turns out to be 100 psi then I would likely be comfortable even at full vacuum but if it turns out to be 20 psi, then I am going to be uncomfortable even at 20 inches knowing that flaws, scratches etc. will reduce the fail point. Personally, I think that the failure point is higher rather than lower given the lack of reports of carboy implosions on this forum (failures of thin wall demijohns not withstanding) but that is just a guess.

Filling the carboy with liquid may reduce the consequences of implosion (see below) but doesn’t change the probability of failure all that much. The increase in pressure at the bottom of a full carboy due to the liquid is about 0.7 psi (about 18 inches of water) so at 20 inches of vacuum, the delta P at the bottom is only reduced from 10 to 9.3 psi. 
Implosion implies a failure where the glass shards from the crushing failure caused by excessive external pressure are accelerated to a velocity sufficient to create a flying glass hazard. The liquid in a full carboy will dissipate the energy of the flying glass and eliminate this hazard (if not the hazards associated with spilling 6 gallons of red wine on a white rug). 

So how else can we mitigate the hazards of flying glass? In chemistry lab we used to tape the outside of vacuum receivers so that the tape would keep the glass from flying in the event of an implosion. Likewise one could tape the outside of a carboy with duct tape or clear packaging tape. Or one could put the carboy inside a bag or pillow case to stop the flying glass. I use a plastic garbage bag for this which I think is probably sufficient to minimize the hazard. I also keep the carboy in a secondary container to minimize the mess from spilled liquid.
Others may have better methods.


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## jimmyjames23 (Mar 28, 2013)

This is why I always degas my wine in outer space. Sure its pricy getting there but using a vacuum in the vacuum of space makes my wine that much better.


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## Runningwolf (Mar 28, 2013)

Grasshopper, lots of great data there. Some I understand and other I don't even try to. I like what you said about why a full carboy is safer than a partially filled one if it did implode. With all the talk out there for years about the possibility of an implosion, I have yet to hear of an actual case of a carboy imploding that was of a sound state.


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## Grasshopper (Mar 28, 2013)

Runningwolf, an implosion is caused by the higher pressure on the outside pushing on the glass and causing it to break. The broken glass starts off being pushed inward. If the carboy is empty, it encounters little resistance and continues to fly off past the other side of the carboy (or where the carboy was) and becomes shrapnel. If the carboy is full of liquid, the glass is slowed down and doesn't make it all the way to the other side. Think how much easier it is to throw something through air as opposed to through water. At least this is my thinking on the subject as I have no direct experience (and hope never to have any).

Does this help?

I haven't heard of any failed carboys either. I hope anybody who has experienced such a failure will pipe up and let us know the specifics. (again demijohns don't count as they are much weaker vessels).


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## Runningwolf (Mar 28, 2013)

Sorry I must not of worded my post good enough. The part you just explained is the part I clearly understand. Thanks for reexplaining it though as Im sure it will help others. Great job!


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## pjd (Mar 28, 2013)

You've got to love retired engineers that make wine! I don't fit that category, I'm not retired!


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## moesagoodboy (Mar 28, 2013)

I have three questions. Has anybody on this forum broken a carboy under vacuum? Has anybody on this forum been nearly injured, or injured, by an imploding carboy? To anyone who has imploded a carboy, can you please describe what you saw?


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## ibglowin (Mar 28, 2013)

As long as the carboy is full you have noting to worry about. If the carboy is empty and you pull a vacuum on it you might want to wear PPE......


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## Thig (Mar 28, 2013)

ibglowin said:


> As long as the carboy is full you have noting to worry about. If the carboy is empty and you pull a vacuum on it you might want to wear PPE......



Are you not pulling a vacuum on an empty carboy every time you rack with the Allinone? Just curious, I have had no problems so far


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## ibglowin (Mar 28, 2013)

I don't use an Allinone so can't comment. But I do use a vacuum pump to filter from a full to an empty. In that case that vacuum is distributed across the entire system and NOT a single empty carboy. BIG difference.


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## vacuumpumpman (Mar 28, 2013)

ibglowin said:


> I don't use an Allinone so can't comment. But I do use a vacuum pump to filter from a full to an empty. In that case that vacuum is distributed across the entire system and NOT a single empty carboy. BIG difference.



Yes the Allinone is doing the same thing as ibglowin explained. The Allinone is designed to pull max of 22'' in hg - but it will probably never reach it due to the LPM of flow it produces and the CO2 being released causing the vacuum pressure to stabilize or increase slowly. This process has been *proven by thousands of carboys* since it came out, several years ago- without any incidents.

Prior to starting the Allinone I did my own research and development on carboy implosions. I personally have mentioned in previous thread a while back that I tried to push the limits of a carboy and boil water using a carboy that was immersed in warm water (double broiler – otherwise) The carboy was approx ¾ full and the water temp inside was at 120 F – the vacuum pressure was a solid 29.+ in hg, and it was shaking violently for at least 4 hours and I redid the same test for several more times to make sure that a carboy can take those vacuum specs without any issues. All my documentations were recorded and witnessed.

I believe if a carboy would break under vacuum it would not fly apart as some think – as soon as a crack starts the vacuum would then decrease suddenly.

*Take for instance a light bulb* is under vacuum correct ?? When you break a light bulb does glass go flying everywhere ? no it implodes within itself.


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## winointraining (Mar 28, 2013)

it would be neat to emplode one just to see where the failure point is


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## vacuumpumpman (Mar 29, 2013)

winointraining said:


> it would be neat to emplode one just to see where the failure point is



I agree - I could not do it !! I had one of the most powerfull AC vacuum pumps while doing this test.

Now if you would tap on it while under vacuum - that is a different story, or take it from extreme temperature change. 

Now lets say if you had a carboy outside in your garage at 50 F and you put a determined amount of vacuum on it - could it possibly break or implode due to temperature change ???


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## novalou (Mar 29, 2013)

Thig said:


> Are you not pulling a vacuum on an empty carboy every time you rack with the Allinone? Just curious, I have had no problems so far



When racking, you would need an air path into the carboy to allow the liquid to leave. You with that said, there will be no vacuum during the racking process.

From the earlier comments: when degassing, with the carboy full, the area exposed to vacuum is small. Remember: force=pressure x area. So lets assume that the neck has an area of 3 sq in and full vacuum is 15psi. The resulting force is 45 lbs. With the carboy empty the area is 115 sq in and the resulting force is 1725 lbs. Big difference. 

Note: liquid is incompressible, so it reinforces the glass.


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## GreginND (Mar 29, 2013)

Glass carboys are pretty darn robust. It is difficult for them to implode. As a chemist I have used plenty of glass containers under high vacuum and have seen my share of implosions. Most of the time the implosions were the result of a weakened area of the glass. A tiny star crack that you might not even see with the visible eye can be a problem. A tiny scratch in the wrong place on a glass container can weaken it. So, one of the things to be very careful of is to make sure you do not ding or scratch your carboys. I think they are thick enough that we should never see a problem with implosion, but I wouldn't want to push it.

Also, the shape of the container has a lot to do with it's strength. A round shape is ideal and one of the strongest containers for vacuum. Carboys are, of course, not round. But they do have rounded edges, not 90 degree angles.


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## vacuumpumpman (Mar 29, 2013)

novalou said:


> When racking, you would need an air path into the carboy to allow the liquid to leave. You with that said, there will be no vacuum during the racking process.
> 
> 
> Note: liquid is incompressible, so it reinforces the glass.



Not sure where you are going here ???
When racking with vacuum - you will always have 
Vacuum in the receiving Carboy


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## Chiumanfu (Mar 29, 2013)

I think novalou means that during the racking process, the wine is constantly flowing ino the carboy to replace the air pulled out by the pump. Although there is still vacuum in the carboy, it will not be as strong as just pulling straight vacuum to degas. There is probably some equilibrium reached depending on the flow rate of the pump compared to the flow rate of the racking hose and canes but the math is way over my head.

A while back I bought a bunch of Mexican carboys off Craigslist. When I got them home and cleaned, I noticed one of them had a very large manufacturing defect in the form of a deep crack along one of the vertical seams. I figured it was garbage so I put it under 23inHg expecting to see a show but I got nothing. I even tapped the crack with a screw driver under vacuum... nothing. I still don't think it's safe to use that particular carboy but it gave me greater confidence in the vacuum process.


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## ibglowin (Mar 29, 2013)

You still have a vacuum, otherwise there would be NO flow.


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## Norske (Mar 29, 2013)

I stated in another post, and posted pics of the problem I had with a new batch of Chinese carboys. One of them cracked when I had just started up my AIP during a racking. I was standing right beside when it cracked just like if you were on a lake and heard the ice crack. I immediately hit the vacumn release and carefully placed the empty carboy into a box to take to the dumpster. I attribute this to the batch of carboys I bought. Several of them were defective.
I no longer handle carboys unless they go in a milk crate first. I also will begin to "tape" em up. As Ben used to say, a stitch in time saves nine.


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## Chiumanfu (Mar 29, 2013)

I think for all intents and purposes, we should lump the new breed of Chinese carboys with the demijohns when it comes to vacuum durability.

No offense to any demijohn users out there.


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## novalou (Mar 29, 2013)

vacuumpumpman said:


> Not sure where you are going here ???
> When racking with vacuum - you will always have
> Vacuum in the receiving Carboy



As long as there is wine flowing, there will be very little vacuum.


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## vacuumpumpman (Mar 29, 2013)

Chiumanfu said:


> I think for all intents and purposes, we should lump the new breed of Chinese carboys with the demijohns when it comes to vacuum durability.
> 
> No offense to any demijohn users out there.



I agree !! I think that they are so cheaply made that they should be recalled, I was referring to the Chinese carboys.


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## winointraining (Mar 29, 2013)

I think that other than a lab or a high volumn industrial application ,or the occasional chinese carboy, I think were flogging an expired equine.
your going to have to have a sudden and high volumn vac to emplode .


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## Grasshopper (Mar 31, 2013)

The horse might not be very active but I don't think we should pronounce it dead yet. I am sure the people that bought the defective Chinese carboys did not expect them to be defective but expected them to behave as the other carboys they have used in the past. Likewise carboys that are purchased off of Craig's List or at garage sales may look OK but have undected flaws. It is also possible that your brother-in-law dinged your carboy and "forgot" to mention it. A rare event is not necessarily less dangerous than one that is more common but likely is more dangerous because it is unexpected.

That said, it doesn't look to me that the consequences of a carboy implosion are likely to be life threatening. But you may be cut, possibly badly, plus there is a high likelihood that wine will be spilled (a tragedy in its own right). Thus some minimal precautions such as use of a secondary container and some means of catching or at least slowing down glass fragments seems prudent. 

I did a web search for glass implosions and found some interesting examples for your edification. The video clips give an indication of how energetic an implosion is likely to be. 

A Department of Energy report on implosions of glassware
http://www.hss.energy.gov/publications/esh_bulletins/BULL0078.html

A video of a Erlenmeyer flask implosion at Duke University
http://www.safety.duke.edu/OHS/media/Flask_implosion_Sands-shortened.mpg

An implosion of a TV CRT tube caused by heating it with a propane torch
[ame]http://www.youtube.com/watch?v=p3G8XYO1gmM[/ame]
A video on what not to do with a beer bottle
[ame]http://www.youtube.com/watch?v=Fm8OuvsSXp8[/ame]
and the following comments from someone who claims to work with high vacuum regarding the implosion of vacuum coffee makers (1 bar = 1 atmosphere of pressure = about 15 psi). Apparently implosions have been a problem with at least one type of coffee maker. 

"Since I work with high-vacuum and ultra-high-vacuum equipment I would like to note that the 'highest' vacuum possible still only represents a pressure of 1 bar. A vacuum is naught but the relative absence of material (e.g. air) and on our planet that means that a container that contains 'no' air is being pressed on from the OUTSIDE by atmospheric pressure of 1 bar. This does not imply that implosions necessarily are less dangerous than explosions, but it is useful to remember just what is doing the pushing and pulling. The reason I bother writing this is that most folks have a misunderstanding about the 'power' or 'strength' of a vacuum. Sucking the air out of a plastic bottle does not in itself make the bottle collapse. It is the air pressure from the outside that forces the walls of the bottle (or vacuum coffee maker) together. If you put a closed bottle of air into a vacuum chamber and then withdrew the air from the bottle it would not collapse.

"By the way, implosions are, in fact, generally less dangerous than explosions because the inrushing air tends to keep shards from flying as far as they would if the vessel exploded. The danger is directly proportional to the volume of the vessel. With hot coffee, of course, there is still a chance of getting scalded. Implosions are often highly impressive because of the sound effects. At least theoretically, a vacuum coffee maker should withstand 1 bar without problem, however, the smallest irregularity in the glass, scratches or microcracks will result in the observed, dramatic behaviour."
Full link http://www.sweetmariascoffee.com/forum/viewtopic.php?f=7&t=809


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## jimmyjames23 (Mar 31, 2013)

For those that fear implosion the safety precautions are simple. 
Place your clean carboy in a 25 gallon beer bucket. Rack your wine into this carboy. Perform the degassing while the container is in the bucket. Should it implode the wine will be caught in the bucket and not all over your floor. 
Placing a towel around the neck of the carboy will prevent flying shards of glass should it ever implode.


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## vacuumpumpman (Mar 31, 2013)

Very interesting Grasshopper

I watched the video -A video of a Erlenmeyer flask implosion at Duke University
and it appears to be an explosion, rather than an implosion - I can not make out all the details in the video. I did notice that 1 tube plugged into the wall and the other went to another container - which appeared to hear sounds of bubbling


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## Grasshopper (Mar 31, 2013)

In the Duke video I think the Erlenmeyer flask is being used as a trap for anything that might come over from the vacuum experiment (distillation?) being carried out in the fume hood. IE the same way the wine bottle in the holder of the All in One is used. My guess is that this is a restaging of an accident that occurred earlier (hence the video's focus on the flask). I am pretty sure it is an implosion.


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## vacuumpumpman (Mar 31, 2013)

Runningwolf said:


> With all the talk out there for years about the possibility of an implosion, I have yet to hear of an actual case of a carboy imploding that was of a sound state.



Dan - 
I must agree - I have looked on this forum - other forums as well as google and never could find it. I have found where people have dropped them or added hot water to a cold carboy and cracked them.


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## dangerdave (Mar 31, 2013)

Ok, I understand all the warnings, but with all of the people on this forum, we have yet to hear from a single person who experienced an implosion. I have racked and degassed under vacuum many hundreds of carboys with my Allinonewine pump without a single incident. I would venture to say, that if all were tallied, amongst all the wine makers we have here, many tens of thousands of carboys of wine have been racked, transfered, degassed, etc., using various and sundry home made or commericially bought vacuum pumps without a single noteable incident thus far.

So what's all the fuss about? The discussion is stimulating, and the science is fascinating, but in my book, one in a million odds are not worth the worry.


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## jimmyjames23 (Mar 31, 2013)

I heard one once. I was in the other room when my friend imploded a 54 L demijohn. Luckily the glass and wine was mostly contained in the Demi holder. Mind you he was using my old Gast industrial vacuum (used for carbon fiber vacuum) it pulls over a bar. I had the regulator set to -20 Hg. 
My friend said he was playing with the knob and then pop!
This was a teardrop Demi. The glass was extremely thin and it was over 40 years old.


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## dangerdave (Mar 31, 2013)

Great story, jimmy, but I don't think anyone has been talking about thin walled demi's. Anyone would advise against ever using a vacuum on them. The discussion has been about carboy implosion. While I appreciate your tale very much, I was wondering if anyone---anyone at all---has ever had a carboy implode under the conditions mentioned in this thread. I think the risk is highly overstated, and that using a vacuum pump drawing less than 25'' of Hg is perfectly safe on an undamaged carboy. Watching for cracks or flaws in one's carboys should be a regular practice for all who emply them whether you use a vacuum pump on them or not.

Can we agree on that?

I just want to address the _real_ level of risk here for those who may be just starting out in wine making and are intrested in simplifying the process with something like the Allinone, but are frightened by the extent of the engineering jargon, which they may/may not fully understand.


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## vacuumpumpman (Mar 31, 2013)

Thanks alot Dave 
I totally understand where you are coming from !! Yes everyone should always look for any stress cracks or flaws in any glass carboy - whither you vacuum rack or not 

I really like when you mentioned -
I just want to address the real level of risk here for those who may be just starting out in wine making and are interested in simplifying the process with something like the Allinone, but are frightened by the extent of the engineering jargon, which they may/may not fully understand.

Dave if you don't mind me asking - how many transfers do you think you have done with the Allinone ?


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## jimmyjames23 (Mar 31, 2013)

I don't think an implosion is possible with a regular carboy. Regular carboys are at least twice as thick as demijohns. Demijohns, especially really old blown ones like my friends are varying thickness. On my friends the wall thickness was less than a 16th" in some areas. 
If I repair my Gast. I'll remove the regulator and make a video of an implosion attempt on my oldest carboy which has micro cracks on the base. Problem is my gauge only measures 1 bar.


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## dangerdave (Mar 31, 2013)

I am currently on batch #62 using my Allinone. With 4-5 transfers per batch for rackings and degassing, that's between 240 and 300 transfers under vacuum without a failure. And that's just me!

Oh, and Steve, thanks for the very best time-saving, back-saving, and _*safe*_ method for transferring and degassing my wines. I love my Allinonewinepump!


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## sdelli (Mar 31, 2013)

Seriously people????? Yes I am sure we can calculate the probability of me dropping a carboy on my toe too! Anything is possible... But has anyone.... I repeat..... ANYONE have a circumstance of a carboy imploding at 22"... Tell you the truth I watch the level of vacuum more to protect the wine!!! Don't buy cheap carboys and play real procedures with them...


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## sdelli (Mar 31, 2013)

I am sure a home made vacuum pump that goes to to some high settings and not regulated could become dangerous.... But I have had my bung sucked in at 22" of vacuum so I doubt it will ever have the ability to build up enough to crack the glass on a carboy.....I believe there are other things that would fail first.....


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