Closed Transfer in Glass Carboy- Am I thinking about this right?

[Deadalus]

People are incompressible, air on the other hand is.
Big difference.

P.S. Where is Vale71 when you need him?

You have no idea here what you are talking about.

Pressure
Clearly division.

Ignoring the beer in the carboy, assume it's empty, the pressure is the same throughout the inside. The force has to be applied to an area and square inches is what we use as a basis. If we say the pressure is 2 psi, that's the same as 288 pounds per square foot (by dimensional analysis). The object isn't suddenly going to break because we decided to change the basis and 288 is bigger than 2. It's the same exact pressure. The units are different. What you are doing wrong is you are just calculating force and not doing the division, which is the application of the force. Now if you keep increasing the pressure, you are increasing the force as the area is the same internally. But what you seem to think is a large pressure really isn't much at all.

 

[shoengine]

This is silly. The carboy cap will go before there is any internal failure. In fact I've had carboy caps fly off routinely during normal fermentation with a three piece airlock being the only check valve.

The exploding glass meme is getting old.

 

[day_trippr]

Indeed, I actually worm-clamp the carboy cap to not lose CO2.

There's a link at the bottom of the page to one of my carboy-racking posts. This was early on in my CO2-push racking - I'm using a bit more sophisticated gear now but not that different...

https://www.homebrewtalk.com/threads/fermentation-and-closed-transfers.671400/#post-8703000
Cheers!

 

[sibelman]

For reference..
1 psi in a 5 gallon carboy is exerting a force of 800 lbs on the internal surface.
2 psi would be 1600 pounds and so forth.
Just something to consider.

Explosion sounds scary of course. Maybe we've never heard of a pressure transfer explosion because death prevented the reports? Or maybe these scary numbers just mean we should be cautious with glass.

 

[Bilsch]

All of my statements are science fact and my numbers are correct. If you want to be cautious that is wise, if not then I wish you luck. But telling new people who don’t understand the physics behind this that it’s perfectly safe is reckless.

 

[BigDave1303]

I have a GF conical & closed loop transfer into kegs using gravity rather than bottled co2.
Firstly, During fermentation I have a blow off tube from the top of the FV to the out post of a keg & vent the gas post out into a bottle containing starsan mix as an airlock. This collects & purges the keg with co2 during fermentation.
Fermentation complete. I connect the keg out post to the bottom tap on the FV & connect the blow off tube to the keg gas post. This creates a closed loop.
Then gently open the FV tap, beer flows out under gravity filling the keg, displacing the co2 back into the top of the FV. No extra pressure needed.
I have the keg standing on scales tared to zero before transferring and stop at 18kg = 18 litres. I don't like to fill to 19 litres. Then I just bottle the last 2-3 litres.

 

[Qhrumphf]

I wouldn't ever apply pressure to a glass carboy. Not ever gonna be worth the risk.

Rather than applying pressure to the carboy, remove pressure from the keg, and connect the gas post of the keg to the where you were gonna apply pressure to your carboy. You've then got a balance line and can let gravity do the work. Beer flowing into the keg will push the keg headspace back into the carboy that'll in turn displace the volume of the beer flowing out.

It'll be slower, you'll have to devise a way to start a siphon, and you'll likely get more ingress than a system under pressure, however it's the only way I can come up with using glass to safely closed transfer.

 

[BigDave1303]

I wouldn't ever apply pressure to a glass carboy. Not ever gonna be worth the risk.

Rather than applying pressure to the carboy, remove pressure from the keg, and connect the gas post of the keg to the where you were gonna apply pressure to your carboy. You've then got a balance line and can let gravity do the work. Beer flowing into the keg will push the keg headspace back into the carboy that'll in turn displace the volume of the beer flowing out.

It'll be slower, you'll have to devise a way to start a siphon, and you'll likely get more ingress than a system under pressure, however it's the only way I can come up with using glass to safely closed transfer.

Agree, getting the syphon started would be the biggest problem in the OP's situation. Perhaps filling the beer line with boiled & cooled water. Connect the co2 return line first, then connect the water filled line to the top of the liquid out on the carboy. When that is snapped onto the keg post the water should start to pull a syphon. Not tried it but I think it should work depending on the head space in the carboy. It will dilute the brew but not by much.

 

[Qhrumphf]

As far as "the carboy cap will pop off before the carboy fails", it strikes me the same as using a PRV as a spunding valve or relying on a GFCI to bail you out of bad electrical practice. A failure safety mechanism is not an excuse to use unsafe practices.

 

[shoengine]

As far as "the carboy cap will pop off before the carboy fails", it strikes me the same as using a PRV as a spunding valve or relying on a GFCI to bail you out of bad electrical practice. A failure safety mechanism is not an excuse to use unsafe practices.

Have you ever used a carboy cap before?

 

[Qhrumphf]

Have you ever used a carboy cap before?

Yes. And i am aware how easy they are to pop off. And that in no way changes the validity of what I just posted.

 

[wischwm]

I've used this set up for a few years now. I keep my pressure down around 2-3 pounds. Keep the carboy on the table and the keg on the floor. Push the racking cane into the head clearance area of the carboy to start. With your keg relief valve open or a gas connect post on, turn the gas on and purge all the way thru the keg. Then push the racking about half way into the carboy to start transferring clear beer. As the level goes down continue to push the racking cane in. Once the level gets low, you can gently tip the carboy to get the last of the beer while keeping yeast / trub / hop matter at the bottom. Quickly remove the quick connect post off the keg when you've completed transfer so you're not CO2 scrubbing your beer when you're done.

 

[shoengine]

Yes. And i am aware how easy they are to pop off. And that in no way changes the validity of what I just posted.

Yeah it does. If you think in anyway that the positive engagement of a carboy cap is similiar to that of a threaded fitting, then you are thinking of this merely from a process standpoint with no respect to reality.

This is really the same thing as using a cork and an airlock. These interfaces will fail before the glass does.

Feel free to search down a corner case.

 

[GrowleyMonster]

But you are sort of imagining a ideal theoretical yield to your carboy implosion. In reality, I believe that the failure will let air in before the thing shatters to the point of pieces parts flying all over.

I use to shoot TV picture tubes and other things that contained a vacuum with bow and arrow or rifle. It was always a let down. Nothing spectacular ever happened.

Things that had pressure in them conversely were spectacular.

This is because there is a very finite limit on the force applied by a vacuum. In a container at sea level ambient outside pressure, an absolutely perfect vacuum without a single molecule of air inside would still only have a pressure differential between inside and outside the container of one bar. On the other hand, for all practical purposes, there is no finite limit to how high you can pressurize a container. A simple aluminum scuba tank is pressurized to around 200 bar.

 

[Qhrumphf]

To me it's a matter of thinking with an approach to safety rather than the actual risk. Applying pressure to a vessel that very explicitly states not to apply pressure is bad safety practice.

An airlock is a pressure release mechanism. I wouldn't want a clogged airlock or blowoff in a carboy either (and while I phased out glass entirely some time ago, years prior to that glass was only a secondary vessel usually for sours where clogging was not going to be a risk).

The same way that botulism poisoning from non-sterile canned wort is so low risk that there are no reported cases, it is still easily avoided and accordingly not worth the risk, however low that risk may be.

 

[wischwm]

Does anyone know how much pressure 2 feet of water creates? Almost 1 psi. WOW, based on the calculations I keep reading, all these carboys should be blowing up when they're full!!! Amazingly.......they don't. There are a lot of brewers who already use this method. I'm one of them. Been using this method for years without incident. Stop speculating on what you think MIGHT happen. Let's continue to hear people who already have experience with this method. To be clear, the people commenting on their theories are not stupid, but you rely on theories in the absence of experience, not instead of it. I've even heard of brewers going as high as 10 psi, but that's unnecessary.

 

[Qhrumphf]

Obviously whomever wherever is free to abide by or disregard whatever safety practices they see fit. It's homebrewing, not commercial brewing where employee and customer safety is a factor, so any risk you choose to assume is your own to bear. And this is arguably safer than the products some breweries are sending out into market (a practice which is not only ill advised but should be flat out illegal and breweries sending out can grenades should be severely punished for it).

 

[shoengine]

To me it's a matter of thinking with an approach to safety rather than the actual risk. Applying pressure to a vessel that very explicitly states not to apply pressure is bad safety practice.

An airlock is a pressure release mechanism. I wouldn't want a clogged airlock or blowoff in a carboy either (and while I phased out glass entirely some time ago, years prior to that glass was only a secondary vessel usually for sours where clogging was not going to be a risk).

The same way that botulism poisoning from non-sterile canned wort is so low risk that there are no reported cases, it is still easily avoided and accordingly not worth the risk, however low that risk may be.

If we are going to be using false equivalencies, I take more risk driving to the store than using a glass carboy. It is a risk I accept, however, and I don't bother telling people not to drive because it is unsafe.

 

[sibelman]

I've done gravity assisted low-pressure transfers from glass carboys to kegs perhaps 20 times -- and hundreds of open transfers before I got some low-oxygen religion. Material I've read here and elsewhere claims it's safe if one uses only a little pressure. But it's always felt somewhat scary -- one of the reasons I finally bought a stainless steel fermenter that holds pressure.

It's not stupid or crazy to avoid intuitively dangerous actions, of course. We all know glass carboys can and do break, and that plastic fermenters are pretty inexpensive. Stories (and gory pictures) of carboy injuries are numerous. Though I've never heard of a carboy failing during pressure transfer, it seems clear there's some risk. People differ in their response to risk -- I've read claims that's partly genetic, fwiw.

So is careful application of, say, 2 psi to a beer-filled glass carboy a "reckless" or "unsafe practice" because of evidence, physics, materials engineering? Is avoiding this practice sensible, maybe "wise," even though driven by intuitive fear bolstered by arithmetic? Each must make their own decision.

 

[Deadalus]

All of my statements are science fact and my numbers are correct. If you want to be cautious that is wise, if not then I wish you luck. But telling new people who don’t understand the physics behind this that it’s perfectly safe is reckless.

You failed to understand the magnitude of the force being applied to the surface and expressed a complete lack of understanding of the basic pressure equation (Pressure= Force/Area). Pretending to know that you understand physics when you are in the habit of ignoring terms in simple equations, that's reckless.

 

[Qhrumphf]

If we are going to be using false equivalencies, I take more risk driving to the store than using a glass carboy. It is a risk I accept, however, and I don't bother telling people not to drive because it is unsafe.

There is no false equivalency. Every glass carboy (or its box) I've ever seen says "not for use with pressurized liquids" and as another poster has said, there are gory pictures galore from broken carboys, albeit every one I can think of from different causes.

And botulism poisoning is a perfectly equivalent comparison. Many brewers have been doing "no chill" brewing where normal boiled wort is sealed up, and often stored a significant amount of time, or simply boiled starter wort is canned. Yet no one (to my knowledge, unless it's changed since last I dug) has died from botulism. Yet the official recommendation (on HBT and elsewhere) is to only store wort that has been pressure canned to truly sterile levels.

It is an extremely low risk, that many choose to overlook.

Driving is the false equivalency. In almost every case for almost all of us, driving (or being driven) is a necessity. So is bathing/showering and a risk of slipping in the tub. When an activity is necessary and unavoidable, risk becomes more necessary. Risk for something purely voluntary like homebrewing, when easily avoidable, is a different beast. As another poster said, we each have to make that determination ourselves.

 

[day_trippr]

[...]there are gory pictures galore from broken carboys, albeit every one I can think of from different causes.

Agreed, I do not recall ever reading a post about a blown-up carboy....

Cheers!

 

[Deadalus]

Dusters, Pressurized Cleaners, Compressed Air Nozzles

GUST Spray Anyway 360° Duster "any angle" pressurized cleaner GUST 360° Spray Anyway Duster lets you spray from any angle - even upside down- without frosting. Contains Dustex 11, a 100% ozone safe, non-abrasive, inert, moisture-free, ultra clean gas for precision cleaning, no CFC's, no HCFC's. Suitable for removing dust, lint and particulates from microscopes, cameras, precision parts, electronic equipment and other delicate parts from any angle. Delivers up to 80 psi blasts. 8 oz. (187ml) canister. SDS (169KB PDF) - - Hazard Shipping Fees

I'm not saying turn your regulator up to 80 psi, just providing an example of 80 psi. (You can also mostly drive nails at that pressure, I usually have no issues when set at 90 psi, but I suspect that the nail gun itself converts that.) The air in a road bike tire is set at around 90 psi too. I'm not afraid of the letting the air out of the tire and having it blow on my hand.

A football (American) 12.5-13.5 psi (unless you are Tom Brady).
A football (American soccer) 8.5 to 15.6 psi.
Pump either one up to 5 psi and let me know how unsafe you feel.

For some reason beer bottles internal pressures are well cited on the web but I did see one saying 45 psi.

You can do all kinds of dangerous things with power tools and compressed air. I clearly remember the first time using a sawzall and a chainsaw and a nail gun. It's good to have a healthy concern about safety with these types of tools. There are safeties and cutoffs for power equipment, but they aren't guaranteed to keep you from hurting yourself. You could severely lacerate yourself with a reciprocating saw or chainsaw, but every time such a tool is mentioned do you think people say, "use a hand saw". It seems like every time that someone mentions a glass carboy though in the this forum, somebody has to mention that they can break and you can get hurt. We are aware it's made out of glass and it breaks and glass is sharp. How many times have you broken a glass in your kitchen and been cut by glass. But you still drink out of it, still use ceramic plates, and even glass baking pans. I don't know, maybe some people still drink out of sippy cups.

Putting compressed air in the vessel, yes different. Data is limited, but examples of such low pressures, pool depth for instance, don't seem to lend much weight to blowing up the carboy. People use compressed air at much higher psi than what we are talking about to dust. Just be reasonable and don't keep turning it up. It does only take a little bit of psi to push the liquid and if it doesn't stop. There is a problem. If your chainsaw gets stuck, stop get a wedge out.

I popped the cap off mine. More of a unique issue in that I had used the cane to cut a hole in silicon tubing. I had thought I got all the pieces out but one piece was sideways I guess because there was flow. So while I was using that racking cane, I wasn't getting much flow at around 3 psi. I was also getting leakage from the cap where I had to squeeze the cap and that improved things but it was taking a long time and it was late and I got really frustrated. I had no reason to believe it was clogged, I didn't put in the bottom, I didn't dry hop it, and I use a hop spider. I turned it up somewhere past 5 psi and off popped the cap. I wasn't going to go past 10, not because I expect a break at that point but simply because that's plenty to push the beer through the tubing. You can dispense beer into your glass from your taps at that pressure. I've never heard of anyone blowing up their glass while pouring either.

 

[Broothru]

You're going to need a spunding valve to relieve pressure in the keg while it's filling, or (less ideally) hold the keg's own PRV open.

I used to do closed transfers with glass carboys. To be honest, it always made me a little nervous, especially if anything clogged the racking cane and required an increase in pressure to dislodge it. It's much safer with a SS conical. And more foolproof from a low oxygen standpoint.

If you'd never had a glass carboy implode, please be aware that they can and do fail. I have, it's no fun and scary as Hell. It wasn't a positive pressure transfer, but rather a negative pressure degassing of a six gallon batch of Chardonnay. As bad a mess as it was, it could have been a whole lot worse. I always thought I was being cautious with carboys. Clearly I neglected to consider some serious safety concerns.

 

[balrog]

FWIW I use plastic big mouth bubbler fermenter sometimes. No spigot, standard airlock holding bung in single hole in the non screwed on top.

To transfer, I remove airlock+stopper, I run a hose from CO2 tank dribbling gas into stopper hole, I take hydrometer sample while co2 is dribbling in, I put in autosiphon connected to vinyl to ball lock to liquid out on keg, which was purged during fermentation, once autosiphon starts, I connect gas out from keg to tube that replaces what CO2 tank was dribbling into stopper hole, then monitor process until complete.

It is not completely O2-less of course, as there is air in both the tubing, and autosiphon, as well as ingress through top hole, and any amount I careless add when using the turkey baster to get the hydrometer sample.

PS while not required to have a spare SQL Server setup in the wood shop cum brewery, it makes for nice conversation decor.

 

[wischwm]

Has anyone had the Krausen plug up an airlock, then build pressure until the bung blew out (and hit the ceiling)? I have. My guess, is that it built up more pressure than he plans to use for his transfer. The cap he's using is sufficient to protect the carboy from exploding - it will pop off.

 

[jseyfert3]

That's what I thought you might be doing. It's pounds divided by square inches. That can be converted to pounds per square ft if you like by multiplying by the value of one, but instead of using 1, you use 144 sq in/1 sq ft as that is also like multiplying by one. You can calculate the total internal surface area and figure out the force, but that force is for the whole area. But in all cases the pressure is 2 pounds per square inch, not 2 pounds by itself.

If you blow 2 psi of air at your skin of your arm, your arm won't break, but your arm hairs might wiggle some. Your skin can withstand about 1000 psi and although glass strength varies that's also the suggested value for regular glass.

Yes, the force is for the entire area. But you cannot state that a material can "withstand" a certain pressure as a blanket statement. Being able to withstand a certain pressure is entire a topic of not only the material, but it's size and shape as well. You must do an internal force analysis to determine if the material is capible of withstanding that pressure or not.

Glass has a tensile strength of roughly 1000 psi. This absolutely, unequivocally does NOT mean that you can make a container out of glass and put 1000 psi in it! Tensile strength is how much force it takes to pull a material apart. For example, in the case of glass, if you had a glass rod with a diameter of 1.13" (cross-sectional area of 1 in^2), and were able to grip the ends of the rod in such a manner that you could pull the rod apart with a force completely in line with the axis of the rod, without the point you are gripping the rod breaking, then it would take roughly 1000 pounds of force to cause the rod to break. This is because you have reached the tensile strength of the glass, 1000 lbs/1 in^2 = 1000 psi. Make sense?

Okay, now the problem is that in a cylindrical shape, such as a carboy or beer bottle, the force is being applied not in the same way that you would when trying to pull apart a glass rod in the above example. The force of air inside the carboy is pushing outwards, which causes the glass to stretch which causes tensile stresses inside the glass that run more or less tangentially with the surface of the glass. In transition areas this gets a bit more complicated, and there are concentrations of stresses. This can all be calculated, however it's been about ten years since we covered this in one of my mechanical engineering classes, and shapes like carboys that aren't perfect spheres or cylinders get more complicated. The key takeaway though is somewhere in the carboy, a portion will reach that 1000 psi point and fail, which will cause the carboy to shatter as glass does. And this will be a point far, far lower than an internal air pressure of 1000 psi, because the tensile stresses within the glass will be much, much higher than the pressure of the air inside the glass. I'd be shocked if a carboy could hold 50 psi. (and I would be nowhere near such a theoretical carboy!)

There's roughly 2800 square inches of skin on a human. If said human dives down 10 feet, call it just 4 psi, that's 11,200 pounds of force on the skin. In your world, do people get crushed into pancakes in the deep end of the pool by that 5 and 1/2 tons of force?

People are incompressible, air on the other hand is.
Big difference.

P.S. Where is Vale71 when you need him?

People have air and other gasses in them. They are very compressible. The liquid and completely solid part of them is not compressible.

If the pressure on the inside of the skin matches that of the outside, there is no force on the skin. If you take a water balloon, fill it with water and no air, and take it to any depth the pressure of the water inside the balloon and the pressure of the water on the outside of the balloon is the same. There is therefore no force on the balloon itself.

Most of humans are effectively water, so the pressure on the inside matches that of the outside, and there is no force applied to the skin. However the lungs are full of air at a pressure of 0 psig, so they will indeed get squished quite easily when diving. This is why it would be impossible to breathe through a hose that goes to the surface if you were at ten feet, the pressure on your lungs is just too much for your muscles to expand your lungs. The squeezed lungs isn't an issue with free divers, as they aren't breathing. Scuba divers get around this issue by having a regulator that delivers air at the pressure of the surrounding water. So at 90 feet the scuba regulator is delivering air at a pressure of approximately 40 psig. Fun fact, while breathing air at 40 psig isn't an issue when the water pressure around you is 40 psig, holding your breath at this point and ascending will cause air embolisms and potentially ruptured lungs if you continue to hold your breath. In normal diving breathing normally will take care of this, but during an emergency ascent it is important to continuously exhale to allow the expanding air to escape your lungs.

All of my statements are science fact and my numbers are correct. If you want to be cautious that is wise, if not then I wish you luck. But telling new people who don’t understand the physics behind this that it’s perfectly safe is reckless.

Your numbers aren't wrong, but similarly to the case of saying "glass can withstand 1000 psi" there is a lot of nuance there. It's generally not useful to calculate a blanket total force number applied evenly across an area, even if the calculation is entirely accurate.

Caution in the pressurization (or evacuation) of glass containers not designed for such is indeed wise though.

 

[hotbeer]

I don't think we are all doing the same "experiment".

 

[Bilsch]

Your numbers aren't wrong, but similarly to the case of saying "glass can withstand 1000 psi" there is a lot of nuance there. It's generally not useful to calculate a blanket total force number applied evenly across an area, even if the calculation is entirely accurate.

Caution in the pressurization (or evacuation) of glass containers not designed for such is indeed wise though.

Thank you for taking the time to add more detail to the mechanics of this situation. Too often these threads get taken over with “I feel like” instead of “the science says” and it’s nice to have engineers stop by and clear up the dogma.

I’ve personally imploded, ruptured and otherwise destroyed a lot of glassware in the lab and therefore experienced this type of carnage first hand. Luckily this was all in a sturdy hood with thick tempered glass doors so I didn’t get hurt. Anyway.. my aim was to simply point out, using total force numbers, that pressurizing/evacuating a glass vessel may pose more unknowns than people realize and that some caution should taken.

 

[Deadalus]

Yes, the force is for the entire area. But you cannot state that a material can "withstand" a certain pressure as a blanket statement. Being able to withstand a certain pressure is entire a topic of not only the material, but it's size and shape as well. You must do an internal force analysis to determine if the material is capible of withstanding that pressure or not.

Glass has a tensile strength of roughly 1000 psi. This absolutely, unequivocally does NOT mean that you can make a container out of glass and put 1000 psi in it! Tensile strength is how much force it takes to pull a material apart. For example, in the case of glass, if you had a glass rod with a diameter of 1.13" (cross-sectional area of 1 in^2), and were able to grip the ends of the rod in such a manner that you could pull the rod apart with a force completely in line with the axis of the rod, without the point you are gripping the rod breaking, then it would take roughly 1000 pounds of force to cause the rod to break. This is because you have reached the tensile strength of the glass, 1000 lbs/1 in^2 = 1000 psi. Make sense?



Okay, now the problem is that in a cylindrical shape, such as a carboy or beer bottle, the force is being applied not in the same way that you would when trying to pull apart a glass rod in the above example. The force of air inside the carboy is pushing outwards, which causes the glass to stretch which causes tensile stresses inside the glass that run more or less tangentially with the surface of the glass. In transition areas this gets a bit more complicated, and there are concentrations of stresses. This can all be calculated, however it's been about ten years since we covered this in one of my mechanical engineering classes, and shapes like carboys that aren't perfect spheres or cylinders get more complicated. The key takeaway though is somewhere in the carboy, a portion will reach that 1000 psi point and fail, which will cause the carboy to shatter as glass does. And this will be a point far, far lower than an internal air pressure of 1000 psi, because the tensile stresses within the glass will be much, much higher than the pressure of the air inside the glass. I'd be shocked if a carboy could hold 50 psi. (and I would be nowhere near such a theoretical carboy!)
...

Yes this makes sense. And I appreciate the elaboration, I am not an engineer, nor a physicist.

To be clear, I didn't say put 1000 psi in the carboy. That was the tensile strength quoted for glass. I also understand that the carboy has thickness and a shape that is going to affect how strong it is as well as how the glass is engineered. I realize that glass may have imperfections, that temperature may affect it negatively, as does gravity. What I will point out in your explanation is that you are saying there are other forces occurring which result from the air pressure and that these will lead to tensile stresses that will exceed the 1000 psi. This can happen far, far lower than an internal air pressure of 1000 psi. I believe you. What you said though is still in agreement with what I said, that the glass could withstand a pressure of 1000 psi.

I also mentioned a quoted value of 45 psi for beer bottles.

No one is suggesting to put 50 psi in it either. Can we get back to the realm of the psi actually considered for use?