Exploding stand question

[beardedirishman]

Ok, It's not that bad...just wondering.

For those of you that have welded stands with hollow square tubing. I've got closed tubes around my burners. Not directly above, but right next to the flame, similar to most brutus builds I see. Has anyone ever wondered about the pressure build-up from heating the square tubing? Just curious if I need to drill some holes to relieve any potential pressure. I'd prefer not to, because then I'd be concerned with rust inside them.

Any insight from experience?

 

[Paulasaurus]

My buddy and I drilled small holes in the underside of the tubes around the burners. Better safe than sorry. The stands are also Brutus type clones.

 

[rdharris55]

The scientific laws of temperature and pressure of a gas say that drilling holes is a waste of time. Your tubing would need to be in a molten state before there was enough internal pressure to deform it, let alone burst.

 

[AluminumGerbil]

Why do people do it for Keggles then? I've seen pictures of those rings blowing.

 

[audger]

I've seen pictures of those rings blowing.

proof or it didnt happen.

 

[rdharris55]

I've seen 1 story with pictures where that has happened. The laws of physics leads to water or moisture trapped inside...or some other gas as a possible explanation. Air alone will not expand enough to build the pressure needed to burst the material. It just cannot happen.

 

[passedpawn]

proof or it didnt happen.

http://forum.northernbrewer.com/viewtopic.php?t=44238

While brewing ... one of the homebrewer's brew kettles (converted sankey keg) expoded with such a bang my ears are still ringing!​

Pics in that thread. I can't get over the odd assortment of brewing footwear, but I guess that's a different topic.

 

[Paulasaurus]

The scientific laws of temperature and pressure of a gas say that drilling holes is a waste of time. Your tubing would need to be in a molten state before there was enough internal pressure to deform it, let alone burst.

Well I ain't no scientist and it only took a few minutes to drill the holes.

Next time around I guess I won't worry so much about it.

 

[OneHoppyGuy]

First: The piece that blew out is not welded shut. It's a rolled edge and there is no air trapped in side.

Second: When welding additional pieces to a frame, the heat far exceeds that of propane. If the theory of exploding frames were true, I'd be dead.

 

[P-J]

proof or it didnt happen.

Are you happy now?

 

[Bernie Brewer]

I've seen 1 story with pictures where that has happened. The laws of physics leads to water or moisture trapped inside...or some other gas as a possible explanation. Air alone will not expand enough to build the pressure needed to burst the material. It just cannot happen.

Uh huh. The laws of physics also state that is impossible to throw a curveball; that it is just an optical illusion.

Just sayin'

 

[passedpawn]

Uh huh. The laws of physics also state that is impossible to throw a curveball; that it is just an optical illusion.

Just sayin'

I've got a great book call "The Physics of Baseball". If you're interested in that sort of thing, you could probably find it really cheap on amazon. OK, back to our regularly scheduled program...

 

[teal]

I'd question this - what's the HARM in poking a few holes other than the 3 minutes it takes to do so?

Why all the angst over those that want to do so? It will not hurt anything, will not cause the frame to buckle and collapse yet it MIGHT alleviate an issue.

Poke the hole and rock on - this isn't rocket science and doesn't need to be that precise.

 

[jcav]

I'm just going to drill a few holes in the frame of my Brutus clone to have peace of mind. This build of mine has given me enough worries with all the things that can go wrong and the cost of it all!!!!!!

No worries then............

John

 

[OneHoppyGuy]

Water inside the frame from drilled holes will allow corrosion. It's a waist of time.

 

[tasq]

Are you happy now?

He can't type. He's too busy putting his foot in his mouth.

 

[cwi]

Water inside the frame from drilled holes will allow corrosion. It's a waist of time.

Weep holes are often used to prevent corrosion. If a joint has a tiny crack or pore, water can build up inside over time due to thermal cycling.

There is also the issue of trying to weld a completely sealed chamber. The heated air can try to blow out the final part of the weld. There are ways around it, but many fabricators will put in a weep hole before welding.

Your welding temp vs. brewing temp and the realized pressure example is a bit flawed. Only the joint is being heated when you weld, but the whole rail gets hot during a boil. The gas (air) is also able to escape while welding the joint. It would still not be enough pressure (<200psig) from air alone to blow out brew stand size tubing.

The deadly combination would be if there were a small crack/flaw in a weld; water builds up during a non-brewing period; then during a boil, the same thing happens to the stand that happened to the keg chime. Small chance for sure, but how much time do you really "waste" drilling an 1/8" hole?

 

[mattd2]

...Small chance for sure, but how much time do you really "waste" drilling an 1/8 hole?

I agree with you 100%, Low chance x High risk = May as well do something about it. I am sure most people who have read that exploding keg article never thought that something like that could ever happen

 

[cwi]

The scientific laws of temperature and pressure of a gas say that drilling holes is a waste of time. Your tubing would need to be in a molten state before there was enough internal pressure to deform it, let alone burst.

I've seen 1 story with pictures where that has happened. The laws of physics leads to water or moisture trapped inside...or some other gas as a possible explanation. Air alone will not expand enough to build the pressure needed to burst the material. It just cannot happen.

My previous post explains exactly how a brew stand can mimic a keg chime.

The problem with using scientific laws for real world scenarios, is that the real world doesn't know that you expect all the other variables to remain ideal and perfect.

Your posts contradict themselves a bit. "I explained with science how it can't happen, but since it did, something else that science can explain must have caused it". I guess as long as all brew stands in your world are perfect, your analysis is complete.

This kind of analysis is why tradesmen hate engineers.

 

[mattd2]

My previous post explains exactly how a brew stand can mimic a keg chime.
The problem with using scientific laws for real world scenarios, is that the real world doesn't know that you expect all the other variables to remain ideal and perfect.

Your posts contradict themselves a bit. "I explained with science how it can't happen, but since it did, something else that science can explain must have caused it". I guess as long as all brew stands in your world are perfect, your analysis is complete.

This kind of analysis is why tradesmen hate engineers.

Or to simply put it, the real world doesn't give a **** about your assumptions

 

[mobilecabinworks]

As a certified and experienced welder I can tell that it is pretty much impossible to have a closed piece of tubing blow up on you. I have used an oxy/fuel torch on closed pipes and tubes and have not seen any problems. MIG welding is not the best weld process for airtight welds. I.E. I have build a couple water tanks, and when my co-worker and I pressure tested the vessels we found multiple pin holes (and not to be cocky, but we are pretty good welders). Plenty big enough for hot gas to transfer in and out. Your real issue lies in moisture and corrosion. The use of weep holes is really only necessary if there is actually a way or moisture to find a way in. I have left a small little spot about 1/8" unwelded (not on the corners) on the bottom side of light duty moisture prone joints on things like picnic tables and such.

 

[cwi]

As a certified and experienced welder I can tell that it is pretty much impossible to have a closed piece of tubing blow up on you.

I think the welders who read the OP read it literally as "for those of you that have welded stands", whereas non-welders read it as "for those of you that have a welded stand". The latter is also what the OP meant. He is referring to the tubes being heated during the boil, not during welding.

Your real issue lies in moisture and corrosion. The use of weep holes is really only necessary if there is actually a way or moisture to find a way in. I have left a small little spot about 1/8" unwelded (not on the corners) on the bottom side of light duty moisture prone joints on things like picnic tables and such.

So like a brewstand that in a best case scenario is stored in a garage?

MIG welding is not the best weld process for airtight welds.

Which is why I don't understand why plumbing the bottom rail for LPG/NG is so popular. It is a bad idea, and easily done correctly with $20 worth of pipe.

 

[DevilsCreekBrewing]

Which is why I don't understand why plumbing the bottom rail for LPG/NG is so popular. It is a bad idea, and easily done correctly with $20 worth of pipe.

I cringe when I see this as well. I have a gas ticket here in Canada, and our regs don't allow the use of seamed pipe for gas transfer, nor the use of MIG to weld the pipe. Stick or TIG only.

I can't envision any scenario where the air pressure could build up sufficiently to blow the pipe in a brew stand, but a flammable gas sure could blow it open at the seam.

 

[cwi]

I can't envision any scenario where the air pressure could build up sufficiently to blow the pipe in a brew stand

Which is why my scenario, as well as the one posted about the keg chime, involves steam.

I can't see why anyone would recommend against the OP drilling weep holes in his frame. Instead of allaying his fears of rust due to adding a weep hole, there are posts trying to prove that a tube blow out can't possibly happen, even in the face of direct photo evidence to the contrary.

His concerns about rust are unfounded, and if anything a bit misguided since weep holes are a strategy to avoid rust. A weep hole will not affect the integrity of his stand, and he would get piece of mind he can't have a tube blow out due to water intrusion, however remote that possibility is.

Instead of more arguments against weep holes simply because of the near impossibility of them being needed, how about coming up with a downside to adding them. (Besides all that time and effort that will be wasted drilling a few 1/16" holes)

 

[P-J]

My bad...

 

[mobilecabinworks]

I'm pretty sure I understood what the OP ment. My response what ment to touch on 2 parts of the issue. Pointing out what my experience is using extreme forms of heat on closed tubing have shown. Not specifically about the act of fusing the 2 parts together. More of an if no "A" then no "B" scenario. Sorry if there was any confusion.

A. If while you are welding it, there is not an explosion issue, then
B. Logic would indicate there being no explosion issue from a propane burner positioned a few inches away.

Regarding the downsides to using weep holes.
Air expands and contracts with temperature and carries with it moisture. If there is a small hole for that air to move freely through a hole in a stand (i.e. a weep hole) it is possibility for the warmed air, being heated inside your tubing from using your burner, to expand outward from the hole and upon contraction bring back moisture into the frame. That air would eventually condense and form water droplets inside the tube that would then create the occurance we know as oxidation. I did not mean to imply this WOULD cause a complete rust out of the frame. Merely wanted to say that I would be more concerned about the possibility of moisture than heat explosion.

I realise that by saying that the air would heat and expand inside the tube it may seem I am contraditing myself. I would like to point out that the air pressures regarding each situation are vastly different. A tube can hold many PSI in pressure (~100psi) depending on wall thickness and weld quality.

Hope that helps clear up any confusion I might have created.

If you are really worried about explosions, use a weep hole (1/4"). You're not really gonna cause yourself any grief. The stand will probably still out live you anyway, with or without a little corrosion. Always err on your feelings of caution, not someone elses.

 

[kevink]

Second: When welding additional pieces to a frame, the heat far exceeds that of propane. If the theory of exploding frames were true, I'd be dead.

Or your welds are $hitty and the pressure is escaping through porosity/holes.

Your example of welding additional pieces to a frame sucks... sorry. When you do that, you heat up a little air inside the frame, but virtually nothing compared to the amount of air that's in it. When you do an hour long boil, there is ample time to heat up all of the air, causing it to expand much more than when you weld a little tab or bracket to the frame in your example.

 

[chicagojimmyjames]

Maybe the original post was actually about the "blow out" (not "blow up") that can happen when you're welding a small sealed container, and the expanding gas on the inside makes it hard for you to finish the welded seam on the outside, as it pushes the puddle apart (hot gas escaping outward) when you're getting to the last little bit of the seam. You wouldn't have a problem before this last 1/2 centimeter of welding. You can't finish in one pass, that's all.

It's never happened to me, but it's possible on small containers. Not on a piece of square tubing on your brewstand.

 

[OneHoppyGuy]

You make an excellent point KevinK...
Just how many stand welds are air tight? MobileCabinWorks make a strong case that they are most likely not. In which case drilling holes remains a waist of time.

 

[cwi]

A. If while you are welding it, there is not an explosion issue, then
B. Logic would indicate there being no explosion issue from a propane burner positioned a few inches away.

I explained why another poster's earlier post that used this logic was also incorrect. When welding one joint on a 6' stand, the entire rail is nowhere near the avg temp it will be during a boil, and air is also escaping during the welding process. That said, the dry air heat expansion is not the worst case scenario, steam is.

Regarding the downsides to using weep holes.
Air expands and contracts with temperature and carries with it moisture. If there is a small hole for that air to move freely through a hole in a stand (i.e. a weep hole) it is possibility for the warmed air, being heated inside your tubing from using your burner, to expand outward from the hole and upon contraction bring back moisture into the frame. That air would eventually condense and form water droplets inside the tube that would then create the occurance we know as oxidation. I did not mean to imply this WOULD cause a complete rust out of the frame. Merely wanted to say that I would be more concerned about the possibility of moisture than heat explosion.

Your description of why not to add vent holes, is exactly why vent/drain holes are added to prevent rust. If the chamber is relatively large, and not quite air tight (typical brewstand weld or fitment), moisture moves into the chamber during thermal cycling. If the seal is very close to, but not quite air tight, this can lead to liquid water retention because it can't get back out as easy as it got in. Then the steam issue comes into play. Vent/drain holes allow any water to drain and/or evaporate.

A tube can hold many PSI in pressure (~100psi) depending on wall thickness and weld quality.

The numbers I ran for a brewstand rail during boil came in around 200PSIG, but was just a rough calc. It is probably close enough, but was only for dry air. The tubing should handle that. However, if liquid water is present in the tube, figure on up to ~3600psi. See the photos in this thread for a visual on the effects of that.

Hope that helps clear up any confusion I might have created.

?

If you are really worried about explosions, use a weep hole (1/4"). You're not really gonna cause yourself any grief. The stand will probably still out live you anyway, with or without a little corrosion. Always err on your feelings of caution, not someone elses.

This clears up the confusion.

 

[cwi]

You make an excellent point KevinK...
Just how many stand welds are air tight? MobileCabinWorks make a strong case that they are most likely not. In which case drilling holes remains a waist of time.

The fact that they are most likely not air tight, but almost so, is exactly why drilling vent/drain holes is not a "waste" of time. You do not appear to understand the difference between what is possible, and what is probable. A whole 20 sec per hole is not a lot to pay for insurance, especially when there are zero downsides to it.

What you do with your own personal stuff is your right, but giving advice to another that could endanger them is not. Winning your own Darwin award is one thing, causing someone else to win one is another. If you plan on producing stands commercially, as you appear to be, I suggest having your plans reviewed by a PE, or having a good attorney on retainer.

 

[Dan]

This blowing up brew stand sounds like a good one for Myth Busters.

Over the last couple of weeks I've read on this forum that copper counterflow chillers can posion us, even though many people use them with no ill affects; and they are sold all over the internet from reputable stores. I've read about exploding keggles that had the 90 degree spaced holes/vents on top or bottom of the keg altered. Now I hear brewstands can blow up or blow out. The last, a big difference, but anyway.

To the welders who commented, could any of you guys just build a simple 4 sided square frame, heat it hot as a brewstand gets in an houre boil to find out if it will actually rupture? Try a couple variations with some moisture inside, with/without weep holes?

This sounds like my next project, of course I need to learn to weld first But signed up for a class a few weeks ago before this thread but because of homebrewing adventures. Class will start in January.

I love this hombrew hobby!!

 

[kevink]

To the welders who commented, could any of you guys just build a simple 4 sided square frame, heat it hot as a brewstand gets in an houre boil to find out if it will actually rupture? Try a couple variations with some moisture inside, with/without weep holes?

Whether it will rupture or not may depend on the quality of the welds... I like your idea for someone who has the time, but I recommend putting a bung in it for a pressure gauge and verify that the frame is air tight first. A frame with vent holes will not blow.

 

[passedpawn]

This blowing up brew stand sounds like a good one for Myth Busters.

Did you see the post in the first page with the picture? Why do you need mythbusters when you have an actual event with pics?

I don't understand whats wrong you most of you. Drill holes and be done with this. Geesh.

 

[cwi]

This blowing up brew stand sounds like a good one for Myth Busters.

Over the last couple of weeks I've read on this forum that copper counterflow chillers can posion us, even though many people use them with no ill affects; and they are sold all over the internet from reputable stores. I've read about exploding keggles that had the 90 degree spaced holes/vents on top or bottom of the keg altered. Now I hear brewstands can blow up or blow out. The last, a big difference, but anyway.

I guess we are safe in assuming your positions on:
Leaded paint, gasoline, solder, water pipes
Seat belts, airbags
circuit breakers, gfci, grounding wires
Life jackets, life boats
Air traffic control

 

[mobilecabinworks]

The numbers I ran for a brewstand rail during boil came in around 200PSIG, but was just a rough calc. It is probably close enough, but was only for dry air. The tubing should handle that. However, if liquid water is present in the tube, figure on up to ~3600psi. See the photos in this thread for a visual on the effects of that.

I'd like to see how you did your calculations. I'd be interested in welding in a threaded fitting and a pressure guage and testing this.

 

[cwi]

I'd like to see how you did your calculations. I'd be interested in welding in a threaded fitting and a pressure guage and testing this.

What you need are called combined gas law equations- Charles' and Boyle's laws. I am not going to try to do ASCII equation writing art.
I used room temp to 300 or 400C (can't remember), but should be close, if not a bit conservative.
Sea level for beginning pressure.

Edit: looks like I forgot temp is in Kelvin for that. I just went off memory that it was proportional to temp, and knew it may be in K. I couldn't remember the conversion factor, and didn't want to look up a C to K. I figured it would balance out with the conservative temp estimate. Pressure would only be a little more than double at 400C, so ~35psig. Still doesn't change anything for me. I never said dry air would blow up the tube. I have always said the danger was if water built up in a semi-airtight rail. Steam = scary.

No need to go to the trouble of welding in a fitting and pressure gauge, the equations will give you that reliably. The unknown is what a max temp for a rail could be. 2000C seems a bit much, and 400C a bit low.

 

[kladue]

ROLFLMAO, this is as about as humorous as any thread has been, the chances of anyone welding a frame gas tight, and then being able to heat enough surface area hot enough to cause material failure is as remote as the chances of being struck by lightning. Review Charles law and apply it to the small percentage of the actual tubing being heated in the burner area( 15-20%) versus the unheated areas dissapating the heat through convection and then solve for the actual pressure rise, not much.

 

[mobilecabinworks]

I'm just going to step aside and agree with kladue. This is getting a little too serious. I didn't realize this would be such a heated topic. Cheers.

 

[Dan]

I guess we are safe in assuming your positions on:
Leaded paint, gasoline, solder, water pipes
Seat belts, airbags
circuit breakers, gfci, grounding wires
Life jackets, life boats
Air traffic control

Look man, I'm not looking for a fight. You made some good points; like lead paint and grounding wires. I work a job that demands air traffic awareness.

I just don't believe a brew stand will blow up during brewing.. HBT is all about admitting our conquest and failings. If exploding keggles were one of our failures it would be spread throughout the threads.

There woud be many posts about the disastors. I have not seen them.

Drink to the foam friend.