Building an Air Tank

[Blowndakrt]

Hey guys, I am still fairly new to welding, but this work will be done by a professional to ensure safety.

I am looking at building an air tank for my air bag suspension. Right now I have a 5 gallon tank that is cyclindrical. I would like to build a tank that is more of a rectangular box shape. This will allow me to get more air into a smaller place by using alot of unused space in my trunk.

The tank will need to hold around 200 psi. I think a safety factor of around 300 psi should be enough. I will use a relief valve rated at 250psi max.

Can a square tank be made that will stand up to these kinds of pressures? I have always been told that air tanks are cyclindrical for a reason. I was also told that if the tanks is rectangular shaped that the pressure will want to push it outward to a round tank shape. LOL.

Is there any way to figure out how thick of steel I will need to use? If I need to have bolted stays welded in? How far apart these will need to be? And any special welding technique that should be used?

Any info would be appreciated. The less legwork and design work I can do myself will save me alot when I take it to the shop.

Thanks

Shawn

[zapster]

IMHO

for what you want to do...
a cylindrical vessel is for you...

and there is a reason for that...

square "tanks" will balloon at 75 psi. even with .125 stock..and for the volume you want to store??
unless they're gussetted from the inside there's no way around it..

may not be much at the start but repeated ballooning will eventually lead to failure...

you dont want that..:nono:

stay away from that kind of danger...
its not good for spectators..:realmad:

(chect the "air tank bumper" thread in general welding questions....)
...zap!

[Blowndakrt]

Well I know it can be done. I have personally seen it. The problem with cyclindrical vessels is the fact they take up too much room to get the same volume.

As far as gussets, wouldn't that be the same as the bolted stays?

I was just reading through the bumper air tank thread when you replied. Some very good concepts and ideas in there but all can be over come with proper engineering. Thats why I am trying to figure out. How to go about engineering one to work?

I mean techinically, the perfect air tank would be perfectly round, since that is the direction that pressure exerts against its walls. But they figured out how to do it with a cyclinder, which is not perfectly round, so there has to be a way. LOL.

Thanks

Shawn

[zapster]

you could always build a square tube "cage" for it...
one in the middle and one on each end... about 1 or 2 inches from each end?maybe 3/4" sq tubing?

...zap!

[WelderDaddy]

Spherical pressure tanks have the same tension stress in all directions: stress = (p*r)/(2t) where p is the pressure, r the radius and t the wall thickness.

Cylindrical tanks have the above pressure in the spherical end caps. In the middle cylinder section, the longitudinal stress is the above value but the hoop stress (in the circumferential direction) is double the above value.

The problem with rectangular tanks is the stress gets quite complicated especially at corners which are stress concentration sites.

[Blowndakrt]

you could always build a square tube "cage" for it...
one in the middle and one on each end... about 1 or 2 inches from each end?maybe 3/4" sq tubing?

...zap!

Hmm, not sure what you mean. Are you saying this would be inside the tank, or on the outside? Or is this something that would attach to the tank to add the extra volume?

Shawn

[Blowndakrt]

Spherical pressure tanks have the same tension stress in all directions: stress = (p*r)/(2t) where p is the pressure, r the radius and t the wall thickness.

Cylindrical tanks have the above pressure in the spherical end caps. In the middle cylinder section, the longitudinal stress is the above value but the hoop stress (in the circumferential direction) is double the above value.

The problem with rectangular tanks is the stress gets quite complicated especially at corners which are stress concentration sites.

So you are saying that the pressure is equally distributed in a cylindrical tank? What about the tanks that don't have the domed shaped ends on them. Would that be the highest stress point since it is not domed?

Could I possibly make a oval shaped tank? Something that would allow more air capacity but still keep its rounded shape? Rounding the corners on a square tank probably wouldn't alleviate enough pressure to be work in my favor, is my quess.

I am very limited on space, hence why I would like to build something to take up as much unused space in my spare tire well area.

Thanks

Shawn

[littlefuzz]

How big is this gonna be? I think if ya used thick material it wouldn't be a problem

[calweld]

For safety, cost, and weight, consider a 12v on-board air compressor, coupled with a small cylindrical air tank.

[Blowndakrt]

How big is this gonna be? I think if ya used thick material it wouldn't be a problem

Well I would like to double my current air capacity. I have a 5 gallon tank now. So if I could get 10 gallons or more, I would be happy.

A rough measurement gives me something that is 36"X24"x4".

Shawn

[Blowndakrt]

For safety, cost, and weight, consider a 12v on-board air compressor, coupled with a small cylindrical air tank.

Well right now I have a 5 gallon tank and 2 12v compressors. Problem is 5 gallons is not quite enough air to completely lift my car. It will raise up enough to drive it, but it will sometimes rub at that height. I am having to lift the car, wait a few minutes for the tank to fill up, and lift again.

Thanks

Shawn

[enlpck]

(As I step out into the firing line again)
All I can say is don't. Don't make one. Buy one that is certified.

Failure of the tank can be deadly to you and to others. If you don't know what you are doing, failure becomes much more likely.

Some principle reasons tanks fail in service (excluding overpressure): Bad material; Poor design; poor fabrication; poor maintainance.

Bad material: you need to be fully aware of the material and its limitations. There are a lot of options out there, but the material used in the real world comes with certifications for the standards it meets, chemical analysis, and often test reports for NDE done during manufacture. If you don't know your material, you won't have a basis or being confident that the material is good. Generally, material is purchased to a particular standard (such as SA516 or A53 or...) that covers most of this, but once you get to nonstandard designs, it gets more critical.

Poor design: Even happens in the commercial world among the experts. bad joint design that leads to cracking in the HAZ from fatigue, underthickness material, improper spec for penetrations, poor mount design (mounts that tear off the vessel from vibration, loading, or from the movement of the vessel wall), walls that move excessively under load, and a pile of other things.

Poor fabrication: All I can say is that there is a reason why the real world requires that the people welding on ANY pressure vessel meet fairly strict requirements, the primary one being that they demonstrate that they can follow a procedure designed for the job and make a satisfactory weld. It isn't rocket science, but if you don't know what you are doing you can get a lot of surprises later.

Poor maintainance: Worst is not keeping the tank interior clean and dry. Oil buildup in the tank can lead to detonation (don't believe it? http://www.cdc.gov/NIOSH/FACE/stateface/ca/05ca010.html )and rust from water will weaken the walls. The rust USUALLY leads to pinhole leaks from pits rusting through, but can lead to a complete seperation of the wall, often with small chunks flying. Add to this, any physical abuse that may embrittle the material or outright tear it. Often, there will be little if any warning that the material will fail, and some types of failure are for all intents NEVER predicatble. Everything seems fine, then th tank is pumping up and lets go, right where that rock whacked it a month ago.

What you are talking about ( a rectangular tank 36"X24"X4" at 200PSI) is about the worst design you could come up with. The big flat sides will try to balloon out from the 175000 pounds pushing on each of them. The corners will twist and stretch. Rough calculation gives about 4" bow with 1/2" thick material. This is real rough, since the parameters are well beyond the point whhere the software is accurate. Likely, the material won't fail at this point (steel is more like gum than it is like rock) but I wouldn't bet my life on it. If you stay the faces (Without doing all of the calculations, you would be looking at about 35 stay rods, using 3/8 plate for the box, based on ASME, with each stay rod being at least 3/4"dia) you and up with more potential problems.

Also note that in most states, it is illegal to make this yourself. You are required to have appropriate crtifications from the state, National Board, ASME, and/or other relevant agencies. If it is going on a vehicle that may ever see the road, throw in DOT. If the tank will be in other than a protected industrial/commercial environment where only those qualified will ever be able to get past appropriate gaurding and containment, other agencies also get involved. And lets not forget the insurance companies, either. See why these things cost so much? $20 for material, $40 for labor, $200 for paperwork.

As a side not, in many states, air tanks of any size must be certified to mount on a vehicle, and even tanks that are certified may b prohibited in some cases. New Jersey, for example, doesn't permit tanks with flat sides.

One of my jobs is looking at worst case scenarios and doing everything possible to avoid them. Your concept, as desirable as it may be, is a whole slew of worst case scenarios waiting to happen. I (obviously) could go on, but I need another cup of coffee.

(steps back from the firing line to visit the coffee pot)

[awright]

Dear Darwin Award Applicant:

Thank you for your fine submission. Even though you are applying in the last few days of the year, I have no doubt that the committee will award you first place and GRAND PRIZE for 2006. I just hope you are still around to receive it.

----------

OK. Sorry, but it is extremely important to get your attention before you start fabricating something and doing your own proof testing in your garage.

Actually, enlpck and others have given you just about all the information you need. DO NOT DO IT! STOP THINKING ABOUT IT! There are excellent engineering reasons that ALL pressure vessels have circular cross-section. Not oval. Not rounded corners. Circular! They are explained by other posters here.

Assuming you have researched the legal and insurance aspects of putting your own pressure vessel in a vehicle, you might consider packing in multiple, certified, circular pressure vessels manifolded together to improve the "packing factor," that is, the amount of air storage in the space available. Draw up the cross-section of the available space and see how you can fit in one large cylinder and four or more small cylinders to use the space most effectively.

awright

[steve45]

As a mechanical engineer, I have to say that enlpck & awright have given you excellent advice. I square pressure vessel is a disaster looking for a place to happen. Your safety factor isn't nearly enough, either.

[MoonRise]

As some other folks have stated, and I'll state it also

DO _NOT_ DO IT!!!!!!!!!!!! (I'll skip the blinking and flashing text fonts for now, but only if you pay attention to what multiple folks are telling you.)

Pressure vessels are circular for a reason. Because they are SAFER that way.

And your supposed safety factor is waaaaaaaay too low. For a vehicle mounted pressure tank, you would be looking at a SF of at LEAST 2x or 3x.

You don't have enough air with your current set-up? Get more or bigger compressors and more CERTIFIED storage volume. Your 5 gallon tank doesn't store enough air for your application, then add another 5 gallon tank or a 10 gallon tank. Or multiple 5 gallon tanks.

Don't want to or can't get a licensed PE (Professional Engineer) to design your tank, an ASME-certified pressure vessel welder to weld it, and a certified testing facility to hydrostatically pressure test your custom cylindrical tanks(s)? Then just BUY some cylindrical pressure tanks of whatever size you want or need.

[Blowndakrt]

I guess I will reply to all as a blanket statement. Easier than clogging up the forum with quotes from each reply.

I am not looking to re-invent the wheel here. I understand that there are lots of things to consider. This is not something I will build myself. I was looking more to do the legwork and calculations myself to save the cost of having an ASME engineer do it.

I completely understand all the dangers involved in such an endeavor. But there will be risk with anything you attempt to have done custom.

I can't simply just start adding more tanks because of the size limitations of free space I have to work with. A larger compressor will not solve my issues. A larger compressor will simply allow me to refill my already low capacity of air faster.

As far as a saftey factor, I can't see the reason to build this container with a saftey factor of 3 or greater. The tank will never be beyond that amount of pressure. I am not sure they even make a 12v compressor that would push up to 600 psi. And a pressure increase due to temperature is minimal unless you are reaching temps over 240 degree F. So why build it so high? A relief valve will be installed along with proper water drains on an automated system.

I can see and understand everyone's concern. But what other options are out there? Besides the "add more tanks" because this is not possible on my setup. Running more compressors or even bigger compressors will only fill the tank faster, it will not give me more capacity.

If need be, I can have an ASME certified engineer design my tank. Which is probably what I will end up doing. My father is an inspector for boilers and pressure vessels for several states. So he runs into guys that do this work on a daily basis. I was mainly looking to be able to cut down some of the middle man work and have my basic design done. You can't just tell an engineer you want this and that, and not even have a design plan of some sort.

Thanks all for your concern and insightful knowledge.

Shawn

[Blowndakrt]

Dear Darwin Award Applicant:

Thank you for your fine submission. Even though you are applying in the last few days of the year, I have no doubt that the committee will award you first place and GRAND PRIZE for 2006. I just hope you are still around to receive it.

----------

OK. Sorry, but it is extremely important to get your attention before you start fabricating something and doing your own proof testing in your garage.

Actually, enlpck and others have given you just about all the information you need. DO NOT DO IT! STOP THINKING ABOUT IT! There are excellent engineering reasons that ALL pressure vessels have circular cross-section. Not oval. Not rounded corners. Circular! They are explained by other posters here.

Assuming you have researched the legal and insurance aspects of putting your own pressure vessel in a vehicle, you might consider packing in multiple, certified, circular pressure vessels manifolded together to improve the "packing factor," that is, the amount of air storage in the space available. Draw up the cross-section of the available space and see how you can fit in one large cylinder and four or more small cylinders to use the space most effectively.

awright

Darwin Award??? You are kidding right? As stated already, this will not be built by me. I will have a shop fabricate and build this tank.

I have personally seen air tanks that are not cylindrical and made to hold pressure far exceeding what I am looking to do. Actually some of these "darwin award" tanks are in hospitals, churches, schools, etc. Albeit they are super thick and designed be to used under exact tolerances but they do exist.

All I wanted to do was find out how they build these tanks and adapt my ideas and WAY lower pressures to work in my situation.

Thanks

Shawn

[zapster]

Just be safe...thats all....in all reality we care..:waving:

we just dont wanna have to type "we told you so" down the road somewhere..

because we will...
if your around to read it

just be safe...stranger things have happened..

...zap!

[Blowndakrt]

Just be safe...thats all....in all reality we care..:waving:

we just dont wanna have to type "we told you so" down the road somewhere..

because we will...
if your around to read it

just be safe...stranger things have happened..

...zap!

And I do appreciate that. I really do. Thats why I figured I would ask here. I know there are alot of people that know more and have done more than I have, or possibly ever will have.

I do understand the dangers. Not gonna build this with spare pop cans I have laying around. LOL. This will be built by someone that builds air tanks for a licensed company. Just didn't want to walk into his office and be dumbfounded by all the parameters he will need to know. So getting some of that legwork out now will help.

I guess it just gets to me when people throw up the "add more tanks" or "get more compressors" responses. When you can't do it the simple ways, you need to be inventive and come up with (scary 2 say but) NEW ideas. I know these types of tanks are possible to be built because I have seen them. Just looking to see how they were built. I didn't know if anyone on here might have had experience with building air tanks or not.

So sorry if I am ruffling anyones feathers, but blanket statements of "don't do it" or the other possible fixes to my problem that I have already stated are not possible with my setup doesn't help the end product.

I am hoping I won't have to hear I told you so's. Hell, I'm hoping I can come back in here with the I told you so's. LOL.

Shawn

[zapster]

I am hoping I won't have to hear I told you so's. Hell, I'm hoping I can come back in here with the I told you so's. LOL.




deal...

but there is a catch..
you have to post pics of whatever you come up with...
if you take our collective advise or not...
post pics of what you end up with..

its only fair...


..zap!

[awright]

No, I wasn't kidding, Shawn. I was trying to get your attention. In vain, it seems, so it must be time to escalate the rhetoric before you win the prize.

Now, please don't be insulted. You asked, and we are all trying to give you feedback to keep you (and your friends and neighbors) alive. Virtually every sentance of your posts reveals a profound lack of understanding of the legal and technical aspects of what you are trying to do.

By the way, before I forget to ask, please post pictures or drawings or names of manufacturers of rectangular parallelopiped pressure vessels. In 50 years of poking around industrial equipment I have never seen such a beast. Aside from the serious safety aspects of such a piece of equipment, it would be an extreme waste of material and would be many times heavier than the same volume and pressure rating as a cylindrical vessel. No one in his right mind would install a non-circular cylindrical high pressure vessel in schools, hospitals, churches, etc. Why would they do it? But, still, I could be convinced by a photograph of the vessel and it's nameplate.

You propose ("I was looking more to do the legwork and calculations myself to save the cost of having an ASME engineer do it") to bypass the pressure vessel engineer and ask a bunch of hobbiests, welders, even certified pressure vessel welders, none of whom you know the qualifications of, how such a pressure vessel should be designed. What can I add to that?

You say, "As far as a saftey factor, I can't see the reason to build this container with a saftey factor of 3 or greater. The tank will never be beyond that amount of pressure. I am not sure they even make a 12v compressor that would push up to 600 psi." This reveals a lack of understanding of what a safety factor is for.

Got to go now. I'm holding up dinner. We'll carry on later, if others haven't gotten your attention by the time I return.

awright

[Blowndakrt]

deal...

but there is a catch..
you have to post pics of whatever you come up with...
if you take our collective advise or not...
post pics of what you end up with..

its only fair...


..zap!

If I ever figure out how to attach pics, I can do that. If I make the file size under 150kb the picture is too small to even see.

Here are some links to old photos I took. Its a pic of the car and the other is of the trunk area where I am tight for room.

http://img.photobucket.com/albums/v255/barkleyfan/7-2-06017.jpg

http://img.photobucket.com/albums/v255/barkleyfan/7-2-06022.jpg


Shawn

[Engloid]

I am not looking to re-invent the wheel here. I understand that there are lots of things to consider. This is not something I will build myself. I was looking more to do the legwork and calculations myself to save the cost of having an ASME engineer do it.
I see what you mean, but if you find a welder that's willing to do this for you, he likely doesn't know the risks HE is taking on by doing it...and likely doesn't have the skills necessary to do this successfully either.
I completely understand all the dangers involved in such an endeavor. But there will be risk with anything you attempt to have done custom.
You do understand that you are risking your LIFE by doing this? Is it worth that to raise a vehicle up and down, while saving the space that you would use with a cylindrical tank? nope.
I can't simply just start adding more tanks because of the size limitations of free space I have to work with. A larger compressor will not solve my issues. A larger compressor will simply allow me to refill my already low capacity of air faster.
Check the pressure ratings of your tank, and maybe you can just put more pressure in it.



As far as a saftey factor, I can't see the reason to build this container with a saftey factor of 3 or greater.
That will probably be 1/2" plate and full penetration welds.
I can see and understand everyone's concern. But what other options are out there? Besides the "add more tanks" because this is not possible on my setup.
It's been possible for everybody else to do. I can't see why your setup is going to be so different.

If need be, I can have an ASME certified engineer design my tank. Which is probably what I will end up doing. My father is an inspector for boilers and pressure vessels for several states.
The cost of doing this will likely be $5000 minimum. You're probably looking at about $15k for this tank, when all is said and done.
So he runs into guys that do this work on a daily basis. I was mainly looking to be able to cut down some of the middle man work and have my basic design done. You can't just tell an engineer you want this and that, and not even have a design plan of some sort.
You probably won't get very far telling an engineer that you want a pressure vessel out of flat plate either.

I agree on the square tank comments others had....don't do it. The flexing will eventually cause failure, unless you're going with something like 1/2" steel.

I think you need to check into what it's going to cost you to get this thing inspecte and stamped FIRST. I'd bet that you will then decide it's already more money than it's worth...without even considering the cost of production.

[Blowndakrt]

No, I wasn't kidding, Shawn. I was trying to get your attention. In vain, it seems, so it must be time to escalate the rhetoric before you win the prize.


Now, please don't be insulted. You asked, and we are all trying to give you feedback to keep you (and your friends and neighbors) alive. Virtually every sentance of your posts reveals a profound lack of understanding of the legal and technical aspects of what you are trying to do.
I have a perfect understanding of the legal and technical aspects of what I am trying to do. The tank will have to be ASME and DOT approved. Dot approval is rated for a saftey factor of 3.5 and the vessel will have to inspected by a certified state inspector. All welds will also have to be inspected by either that inspector or a pressure vessel weld inspector.


By the way, before I forget to ask, please post pictures or drawings or names of manufacturers of rectangular parallelopiped pressure vessels. In 50 years of poking around industrial equipment I have never seen such a beast. Aside from the serious safety aspects of such a piece of equipment, it would be an extreme waste of material and would be many times heavier than the same volume and pressure rating as a cylindrical vessel. No one in his right mind would install a non-circular cylindrical high pressure vessel in schools, hospitals, churches, etc. Why would they do it? But, still, I could be convinced by a photograph of the vessel and it's nameplate.
I don't have pictures of these air tanks. Some schools, churches, and hospitals that have revamped their pressure vessel needs that did not have ample room have had these tanks made. Having these tanks made usually run around $4-6K depending on size, but is still cheaper than digging up more basement/boiler room areas. I have seen tanks that have flat sides, although haven't seen any with corners, but even you guys are saying the flat sides is dangerous. I have actually seen an air tank that looked like the shape of a spare tire. Not like the pancake tanks that are being sold. This one was probably 30" in diameter, and had completely flat sides on the top and bottom. They were not domed at all. It has one welded stay in it and help pressure above 1000 psi. This tank was actually in a hospital and was designed to slide into a small crawl space between the boiler and its related piping.

I also know we have equipment at work and the frame work is built from square stainless steel tubing. All the air supply runs through this frame work. And I know this tubing holds 400 psi. I do realize that square tubing is quite a bit stronger than building a square, but still square none the less. Then ends of the tubing are not domed or rounded. In fact it is either a mitered corner or capped off.


You propose ("I was looking more to do the legwork and calculations myself to save the cost of having an ASME engineer do it") to bypass the pressure vessel engineer and ask a bunch of hobbiests, welders, even certified pressure vessel welders, none of whom you know the qualifications of, how such a pressure vessel should be designed. What can I add to that?

I am not asking them to design and blueprint my tank for me. I asked for recommendations. Advice is usually free. I don't know if you even own a welder, but take your advice the same as the next guy. Common sense comes into play with some of these statements. I am well aware that just because someone talks big on the computer doesn't mean they know what they are talking about. But at the same time, he could be a guy that builds tanks everyday. All knowledge is learned. Whether its taught and told to you or learned from experience. I was asking because if I know some of the calculations that will need to be made may greatly alter my design. If I know that I will need a certain number of stays in a given area, I can calculate and figure out if this number of stays will affect my overall design. I have never said I want to bypass the engineer. I just wanted to do some of the legwork. If I can narrow down a design, or even an idea, for that matter, it saves time when speaking with the engineer. Time is money.


You say, "As far as a saftey factor, I can't see the reason to build this container with a saftey factor of 3 or greater. The tank will never be beyond that amount of pressure. I am not sure they even make a 12v compressor that would push up to 600 psi." This reveals a lack of understanding of what a safety factor is for.

I know what a saftey factor is for. Saftey factor is bascially a worse case scenario. You do not want to build a tank to hold 100 psi but rupture and 105psi. What I was saying was my compressors, or any in the 12v market, that I know of will even push a tank to a level that it would need anything more than a saftey factor of 3. Knowing what the DOT requires, I know it will need to be at at least a saftey factor of 3.5. It is bascially there as a saftey margin in case something fails. I know a pressure switch can go bad. I know a relief valve could fail and not function properly at a set pressure. The reason I stated that I don't see why I would need a safety factor above 3 is that is 600psi. No matter what fails in the system, it is not possible to reach 600 psi with any of the 12v compressors that I know of or will use. So where will this extra pressure come from?


Got to go now. I'm holding up dinner. We'll carry on later, if others haven't gotten your attention by the time I return.

awright[/QUOTE]

Everyone has my attention here. I do understand what you are trying to say. But like all things, just because its not the normal way of doing things, or the cheapest way, doesn't mean its the only way. Thats really what I am trying to find out. Cost isn't really a huge issue, its the free space I have to work with that is the main issue.

Thanks

Shawn

[Blowndakrt]

I see what you mean, but if you find a welder that's willing to do this for you, he likely doesn't know the risks HE is taking on by doing it...and likely doesn't have the skills necessary to do this successfully either.

You do understand that you are risking your LIFE by doing this? Is it worth that to raise a vehicle up and down, while saving the space that you would use with a cylindrical tank? nope..

Well the risk of life is all in the eye of the beholder. Look at drag racers. It is worth it to risk your life to run the shortest time? Depends on how that person feels. Granted they also employ certain saftey measure to help ensure that this is not the outcome. All of which I am willing to do to acheive a functional, safe product. I am not looking to slap something together to make this work. This will be very carefully planned and designed to limit the amount of failures.


Check the pressure ratings of your tank, and maybe you can just put more pressure in it..

I am looking into that as well. I am checking to see what the tanks are rated at and see what kind of pressure I can actually run saftely in their tanks. I am not sure how much I will gain by a certain pressure increase. Is there a way to calculate that out?




That will probably be 1/2" plate and full penetration welds.

It's been possible for everybody else to do. I can't see why your setup is going to be so different..

Look at the pictures I posted above. I simply don't have room for what I would like to do. The trunk will be full of stereo equipment, a full size spare, and possibly 2 more compressors. As much room as I have is gonna be where the spare tire used to reside.


The cost of doing this will likely be $5000 minimum. You're probably looking at about $15k for this tank, when all is said and done..

$15K is not out of the ballpark for me as of yet. I am fully aware of what customs costs. I have a truck that they do not offer many aftermarket parts for, so most of it has been custom one of parts for it as well. So I am well versed on spending alot to get a little. Hahaha


You probably won't get very far telling an engineer that you want a pressure vessel out of flat plate either.

I agree on the square tank comments others had....don't do it. The flexing will eventually cause failure, unless you're going with something like 1/2" steel..

Well the 1/2" steel would not be out of the question. I know it will be heavy once it is said and done. Just don't know how much actual weight that would add. The weight is probably the only real concern I have as to having this built.

I think you need to check into what it's going to cost you to get this thing inspecte and stamped FIRST. I'd bet that you will then decide it's already more money than it's worth...without even considering the cost of production.

Thanks

Shawn

[lotechman]

The only safe way I can see is to use multiple small tanks stacked to fill the space. Have you considered some large pipe say three inch diameter capped on the ends, fairily long, placed in a stratigic location?

[Engloid]

I have a perfect understanding of the legal and technical aspects of what I am trying to do. The tank will have to be ASME and DOT approved. Dot approval is rated for a saftey factor of 3.5 and the vessel will have to inspected by a certified state inspector. All welds will also have to be inspected by either that inspector or a pressure vessel weld inspector.
Have you checked to see what the inspection and stamping will cost you?
I have seen tanks that have flat sides, although haven't seen any with corners, but even you guys are saying the flat sides is dangerous. I have actually seen an air tank that looked like the shape of a spare tire. Not like the pancake tanks that are being sold. This one was probably 30" in diameter, and had completely flat sides on the top and bottom. They were not domed at all. It has one welded stay in it and help pressure above 1000 psi.
What was the material thickness, and what was it used for?
This tank was actually in a hospital and was designed to slide into a small crawl space between the boiler and its related piping.
Are you sure that this wasn't on the water side of the boiler, where pressure is needed, yet is low?
I also know we have equipment at work and the frame work is built from square stainless steel tubing. All the air supply runs through this frame work. And I know this tubing holds 400 psi. I do realize that square tubing is quite a bit stronger than building a square, but still square none the less. Then ends of the tubing are not domed or rounded. In fact it is either a mitered corner or capped off.
Look at the difference in dimensions of the flat sides. You're probably talking about 1" square tube, versus a tank that has sides of several inches, at least. That allows a LOT more flexing.
I was asking because if I know some of the calculations that will need to be made may greatly alter my design. If I know that I will need a certain number of stays in a given area, I can calculate and figure out if this number of stays will affect my overall design.
What you're asking for is information that is "tried and true"....such as equations. What we're giving you is advice that's "tried and true."... such as the downfalls of using flat sides for a pressure vessel.
The reason I stated that I don't see why I would need a safety factor above 3 is that is 600psi. No matter what fails in the system, it is not possible to reach 600 psi with any of the 12v compressors that I know of or will use. So where will this extra pressure come from?
It doesn't matter. As far as I know, the codes don't even consider the maximum that your compressor will put out. In other words, if you are going to run this at 50psi, and the compressor maxes out at 100psi, then you may need to build it to hold 150psi (3x normal operational pressure). Sure, the pump may never be able to put out 150psi...but the tank is not stamped with any information that designates the size or ability of the pump. What happens if you sell this truck and somebody else pulls off the tank and uses it for another purpose? It's your *** on the line. You may never plan to sell it, and may even remove it before selling it. Fine... lets say you do that and then you died. If that tank ever gets used and fails, what's the welder's liability in this?
Everyone has my attention here. I do understand what you are trying to say. But like all things, just because its not the normal way of doing things, or the cheapest way, doesn't mean its the only way. [quote]
It's not so much a matter of easy, cheap, or normal...just a matter of safe.
[QUOTE=Blowndakrt]Thats really what I am trying to find out. Cost isn't really a huge issue, its the free space I have to work with that is the main issue.
If cost isn't important, then just get an engineer to design it from scratch. There's not a lot you could do to help out an experienced pressure vessel designer than to give him the volume you want and the space limitations. The things you could do to help will take you hours..and save him about 5 minutes.

[Blowndakrt]

The only safe way I can see is to use multiple small tanks stacked to fill the space. Have you considered some large pipe say three inch diameter capped on the ends, fairily long, placed in a stratigic location?


I have actually thought of this. Haven't ruled it out completely, but I was told that if I weld onto an already finished tank, that it will have to be reinspected. I thought of just using a bunch of 3 gallon tanks, cutting the little mounting legs off of them and welding some small pieces to each one to hold it in a cluster form. Just didn't know if it would help me if I have to have it all reinspected and go through all the legal stuff of getting it certified again or just building one and having to do that anyways.

Shawn

[Engloid]

I am checking to see what the tanks are rated at and see what kind of pressure I can actually run saftely in their tanks. I am not sure how much I will gain by a certain pressure increase. Is there a way to calculate that out?
Not that I'm aware of. I can only suggest that you contact the manufacturer. It seems that they'd have told you or put it in manuals or something, what the max pressure is...in order to help limit their liability. I dunno...maybe you bought it used or something.
Look at the pictures I posted above. I simply don't have room for what I would like to do. The trunk will be full of stereo equipment, a full size spare, and possibly 2 more compressors. As much room as I have is gonna be where the spare tire used to reside.
You have room for subs, I guess...but no room for a round tank?
Well the 1/2" steel would not be out of the question. I know it will be heavy once it is said and done. Just don't know how much actual weight that would add. The weight is probably the only real concern I have as to having this built.
No offense, but it sounds like safety is last on your list...behind weight and space usage. I think I'd have safety on top of my list and work on the space savings when it comes to the stereo stuff.

[Engloid]

I was told that if I weld onto an already finished tank, that it will have to be reinspected.
That is correct... yet I THINK you can weld ON the tank without reinspecting, but if you weld any pressure boundaries (weld in bungs, etc) that it has to be inspected again.

[Blowndakrt]

What was the material thickness, and what was it used for?

I am not sure that exact thickness. It was used to hold air pressure for some piece of equipment on the main floor. The compressor was mounted next to in the crawl space. Then it had hard line that went up through the floor to the machine. I never went up and looked at the machine or what it was being used for.


Are you sure that this wasn't on the water side of the boiler, where pressure is needed, yet is low?

No this was for machine that I mentioned above. The compressor was mounted next to it in the crawl space. There was not enough room to mount the compressor directly to the air tank.


Look at the difference in dimensions of the flat sides. You're probably talking about 1" square tube, versus a tank that has sides of several inches, at least. That allows a LOT more flexing.
The square tubing on the machines at work vary. The base is made out of 5 inch square tubing. The supporting tubes that run upward from the base and actually build the frame work to hold the machine is either 3 or 4 inch tubing. These all hold air because they all have small press in fittings for air lines.




It doesn't matter. As far as I know, the codes don't even consider the maximum that your compressor will put out. In other words, if you are going to run this at 50psi, and the compressor maxes out at 100psi, then you may need to build it to hold 150psi (3x normal operational pressure). Sure, the pump may never be able to put out 150psi...but the tank is not stamped with any information that designates the size or ability of the pump. What happens if you sell this truck and somebody else pulls off the tank and uses it for another purpose? It's your *** on the line. You may never plan to sell it, and may even remove it before selling it. Fine... lets say you do that and then you died. If that tank ever gets used and fails, what's the welder's liability in this?

Actually, looking at my tank, I don't see a stamping anywhere on it. To be honest, I have no clue if its even DOT approved or not. I am not gonna talk about the company I bought it from to avoid possible legal action. But from what I have been able to see, I can't see any stamping on the tank at all. No max pressure stampings, no operation pressure, etc.


Shawn

[Blowndakrt]

You have room for subs, I guess...but no room for a round tank?

No offense, but it sounds like safety is last on your list...behind weight and space usage. I think I'd have safety on top of my list and work on the space savings when it comes to the stereo stuff.

You could not be further from the truth. Just because you do something different doesn't mean you aren't wanting it to be safe. I have never said I want an air tank that is not going to be safe. I just don't feel that there is one way, and only one way of being safe with an air tank. Actually, no tank is truly safe. No matter what all you do, there will be risked involved. I am looking to see how I could go about having a tank built that would be safe and still give me the extra room needed for the stereo equipment. I work for a stereo shop, so to show off what all our shop can do requires the use of the most space that we can get. The more inventive we can get with space and the use of it, the more apt you are in the business world. Its all about being different than the car next to you. Going above and beyond the norm is not only expected, it almost required to get noticed in the automotive world.

Shawn

[Sober_Pollock]

Blowndakrt:

Here is some specific help rather than the "blanket statements" as you call them.

You mentioned using relief valves or safety valves.....

You DO realize that when choosing a relief valve, you must not only consider what pressure rating to use, but also what volume?

Different types of vessels (such as steam, air, compressed gas, etc.) have different requirements.

The relief valve is required to flow some specified volume in relation to the compressor or compressors volume.

In other words it would sound like this:

"If the compressor is rated to deliver 10 cubic feet per minute, the relief valve must be rated at twice as much (20 cubic feet per minute)" (This is not a real standard, just an example)

Let me put it to you this way: If you have a compressor capable of delivering 10 cubic feet per minute pumping into a tank with a pressure relief valve that can only flow 5 cubic feet per minute, it would still explode even after the relief valve opened in the case of a malfunction!

The relief valve MUST be sized PROPERLY!

I don't want to discourage you, on the contrary, I encourage you to learn everything there is to know about this.

But.....Using this relief valve volume as an example.....If this is something you were not aware of or never thought of.....How many other things are there about this topic that you are not aware of or never thought of?

IF you want to know this, you have to study this subject from beginning to end because there is no way for anyone here to know what it is you need to hear.

None of us knows what you have a good grasp of and what you don't have a good grasp of. So, there is no way for any of us to know what to tell you.

This is why you are getting these "blanket statements" as you call them!

[Blowndakrt]

Blowndakrt:

Here is some specific help rather than the "blanket statements" as you call them.

You mentioned using relief valves or safety valves.....

You DO realize that when choosing a relief valve, you must not only consider what pressure rating to use, but also what volume?

Different types of vessels (such as steam, air, compressed gas, etc.) have different requirements.

The relief valve is required to flow some specified volume in relation to the compressor or compressors volume.

In other words it would sound like this:

"If the compressor is rated to deliver 10 cubic feet per minute, the relief valve must be rated at twice as much (20 cubic feet per minute)" (This is not a real standard, just an example)

Let me put it to you this way: If you have a compressor capable of delivering 10 cubic feet per minute pumping into a tank with a pressure relief valve that can only flow 5 cubic feet per minute, it would still explode even after the relief valve opened in the case of a malfunction!

The relief valve MUST be sized PROPERLY!

I don't want to discourage you, on the contrary, I encourage you to learn everything there is to know about this.

But.....Using this relief valve volume as an example.....If this is something you were not aware of or never thought of.....How many other things are there about this topic that you are not aware of or never thought of?

IF you want to know this, you have to study this subject from beginning to end because there is no way for anyone here to know what it is you need to hear.

None of us knows what you have a good grasp of and what you don't have a good grasp of. So, there is no way for any of us to know what to tell you.

This is why you are getting these "blanket statements" as you call them!

The relief valve I was aware of. If the compressor is capable of outflowing the relief valve it can't very well release enough pressure in time to avoid a failure. Similiar to filling up a bucket with a garden hose. If the hole in the bucket isn't big enough to let the water out just as fast the hose fills it, the bucket will still overflow.

I realize not everyone knows my knowlege base or what else I still need to take into consideration. Thats why I was asking. What don't I know about and air tank that I need to consider in my endeavor.

That was not my reasoning for the "blanket statement" comment. My reasoning was that I was getting replies as to not to do it, or it wasn't safe. But the issues they gave for it not being safe could be overcome with proper engineering or small design changes.

I am not getting upset with anyone with their comments. The only thing that got under my skin was the "darwin award" comment. Especially when that would imply that this was something stupid to do. Its not stupid if all the parameters for failure are looked at and adjusted accordingly. Hell to me, making an air tank that is not the typical shape to what everyone considers as standard might be a smart thing. Opens lot of possibilities for others in similiar situations.

I am pretty much done on the subject though. I will speak to a pressure vessel engineer to get a better idea of what all needs to be done to make something like this work.

I was mainly looking for some insight into things I should consider or possible problems in an air tank design.

Thanks

Shawn

[awright]

Shawn, I apologze for the "Darwin Award" statement. It was way outside my normal mode of discourse here. It was, however, not said to insult or hurt, but to get your attention. As acknowledged here, none of us really know much about the technical sophistication of other posters, so we sometimes have to assume that we are starting with the basics. I see that there has been a lot of discussion since my last post, so I have nothing to add.

I think we have all had our say, delivered out caveats, had a lively dialogue. I (you'll be glad to hear) have nothing more to say except to request that you keep us informed of progress made on the project, let us know what the engineer says, and show us pictures of the finished tank.

Good luck.

awright

[littlefuzz]

I think as long as your material is thick enough you'd be fine, as I stated before. 1/2" should be a good safety margin, but the way I figure it's gonna be a little over 300lbs. That might would be the deal breaker. Please post pics if ya get one built.

[steve45]

I completely understand all the dangers involved in such an endeavor. But there will be risk with anything you attempt to have done custom.

As far as a saftey factor, I can't see the reason to build this container with a saftey factor of 3 or greater. The tank will never be beyond that amount of pressure. I am not sure they even make a 12v compressor that would push up to 600 psi. And a pressure increase due to temperature is minimal unless you are reaching temps over 240 degree F. So why build it so high? A relief valve will be installed along with proper water drains on an automated system.

Shawn

Well, it's pretty obvious that you DON'T understand the dangers involved. The reason you have a safety factor is to protect you from defects, corrosion, unexpected loads, etc. The safety factor in public buildings, bridges, etc. is 10!

I don't understand your comment about 240 degrees F. Pressure increases linearly with increases in absolute temperature, NOT Farenheit temperature.

You don't understand the difference between pressure and stress. Pressure in a vessel will be uniform throughout, but the stress will be a function of it's shape and thickness. When you use a square corner, the stress will theoretically approach infinity. In reality, it won't because the material will fail. You MUST use radiused corners.

If you weld on a pressure vessel, you void it's pressure rating. It MUST be retested and re-certified (I think it would need to be stress-relieved, too). The reason is that you don't know how deep your weld penetrated, and how the grain structure has been affected.

Put it this way: there are few outfits that are more concerned about saving space and weight than NASA when they design a spacecraft. Guess what they use.

[JTMcC]

I think as long as your material is thick enough you'd be fine, as I stated before. 1/2" should be a good safety margin,



Those that think 1/2" plate will work in a 24" X 36" X 4" vessel @200psi need to spend the money to buy Section VIII of the ASME B&PV Code, and turn to Division 1, Appendix 13 and read up on non circular pressure vessels. The calculations are extreeeemly tediuos, and exceeeedingly long, and beyond the capabilities of most non geeeek math enthusiasts but the answer lies there for anyone interested.

Like several people have already said, to build that vessel legally will require cubic dollars.

JTMcC.

[Engloid]

Those that think 1/2" plate will work in a 24" X 36" X 4" vessel @200psi need to spend the money to buy Section VIII of the ASME B&PV Code
Wouldn't it be cheaper to just pay somebody to do this, than to buy that code? I hear it cost more than just a few bucks.

[JTMcC]

Wouldn't it be cheaper to just pay somebody to do this, than to buy that code? I hear it cost more than just a few bucks.


You missed the point. But that's my fault I'm sure as the point was rather subtle, and somewhat dry.

JTMcC.:)

[enlpck]

This is an... interesting... discussion.

JT: You weren't that subtle

I ran the stated dimentions yesterday for 1/2" plate, unstayed, 200PSI. THere is a reason that I have spreadsheets set up for these calculations: I hate doing them by hand if I can avoid it. 1/2" will no be sufficiant by a long shot.

Yes, there are a lot of pressure vessels around with flat faces, and ASME allows (in some circumstances) square corners. As said, it usually isn't worth it unless absolutely necessary. Many of these vessels are NOT certified or built to code. People get away with it in a lot of cases because they are in a jurisdiction where inspections arn't done, or no one knows about the vessels, or there is an inspector that is willing to let it go (sometimes without sufficient analysis) or the though 'it's only air' comes up, or.....


What jurisdiction do you reside in? This makes a difference in terms of the regs.


For some practical advice, if this were to show up in front of me for a design (note: I do not hold a PE and this is NOT to be construed in any way as a design suitable for construction or that this information reflects best design practice or legal practice in any jurisdiction. It is provided as an incomplete concept, and evaluation and analysis is the responsibility of the reader. Any statements here have no connection to my employers) I would suggest going round perimeter, not rectangular (the analysys is a LOT easier, and it is structurally much better. 24" dia, 4"thick gives about 1CuFt, or just under 8gal). Put a 2" radius flange on the edge of two disks of the appropriate steel, circumferential full penetration weld all around, then stay the faces appropriately. This could probably be done with 3/8" material, if the stay pattern was designed correctly. As I recall, 3/8" is the minimum thickness for stayed flat surfaces, but I could be incorrect. Nozzles would need to be commercial engineered nozzle welded into the shell to provide proper reinforcement. Details? Up to you, or better yet, a PE willing to put his stamp on the design. NDE? Up to the inspector.


Now go read SecVIII (and for good measure, SecIX, I, and V. You might find SecX interesting for a different option. "I have one word for you: plastics"). As a side note, I wish I had the kind of money that I could even consider paying for something like this. A Lot cheaper and easier to manifold several lengths of pipe.

[zapster]

I Think i'll just sit here and watch..:cool:

...zap!

[littlefuzz]

Those that think 1/2" plate will work in a 24" X 36" X 4" vessel @200psi need to spend the money to buy Section VIII of the ASME B&PV Code, and turn to Division 1, Appendix 13 and read up on non circular pressure vessels. The calculations are extreeeemly tediuos, and exceeeedingly long, and beyond the capabilities of most non geeeek math enthusiasts but the answer lies there for anyone interested.

Like several people have already said, to build that vessel legally will require cubic dollars.

JTMcC.

I never said anything about legalities, I just said I think it would work. I'm sure there are things that I do that some of you guys wouldn't approve of either but works for me. Whatever. I'm outta this one, can't argue with logic.

[Rojodiablo]

I have an idea that will circumnavigate the rect. issue. Use mutiple cylinders, stacked next to each other. You can make a template to hold 2,3,4 cylinders next to each other, with mounting brackets for the whole assembly. Plumb them from one to the next, put drains in each, and bolt it in the truck and go. You would lose a little volume, but it would work well.

[GWallace]

I just read the entire post. Have you looked into using an aircraft hydraulic accumulator tank. I know there is a bladder in most of them but they are always at 3000 PSI. Because they are in aircraft they are typically small. They can be had probably pretty cheap from a salvage yard. Just a thought.

Your car looks great. Your installation looks great. Be careful and have fun.

[JBFab]

I just read this entire post, and although I am not a PE nor do I mean to construe myself as one, I think I have an idea that would both suit your space needs, and make for more practical engineering(and look pretty cool to boot.). Since money is not much of an object, try a toroidial shaped tank that would fit in the desired space, make it out of large diameter pipe, if need be, make it oblong. if more volume is needed, add cross members inside the main torus.

[Rick Moran]

I guess I am out of the loop on this one. In our day, we just used to torch the springs until it dropped to the desired height and then use a tape measure to even it up. Later on we made shackle bars to raise the rear end up enough to clear our huge rear tires that we'd smoke the rubber off of at every green light. After that we put curtins in our jacked up vans with quadraphonic sound systems and a red light. :cool2: Eventually, we sold the race car, van and lowrider to build a 4X4 higher than anyone else, even though we lived in the city and seldom went off-road. Now they are using hydraulics to bounce the car in the air or jack the truck bed over to the left side or some darn thing.

I guess this leads me to the question, just so as to keep up with the times, why not just use hydraulics and forget air pressure? You have enough room for an adaquate size tank, and pump, and maybe even mounted under the car. That way, you can have your trunk back for luggage, groceries, a baby car seat or some other silly thing like that.

Don't even think about building or desiging an air tank. As you said, you are having a hard enough time trying to upload pics.

[mlmonte]

NO NO NO!!! NO square pressure vessels!

Think about it.
Coffins are sort of elongated squares...

[Blowndakrt]

Wow, this was actually still going. Didn't stop in to check for a long time.

I have spoken to a PV engineer. He didn't act surprised when I mentioned what I would like to do. He said he will work up some calculations in his free time to keep my cost at a minimum. Bascially a favor to me since he has worked with my father on several occasions. He did say I would be better off not having the square corners. But a box shaped tank is not uncommon. Using a radiused corner will help any pressure issues I would have in the corners.


Steve45: I am not sure where you are getting your information from, but the saftey factor for a pressure vessel in any public building is 3.5. That is an ASME standard. A bridge? Can't comment on the saftey factor of the concrete, but I don't see many pressure vessels being needed in the bridge.

Rojodiablo: The issues is the actual amount of space I have to mount these tanks. Multiple tanks would take up more room that one single tank. Since I am limited on space I am trying to use up as much negative space that I have.

GWallace: I am not familiar with this type of tank. I don't know what compressor I would need to get up to 3000psi. If it is smaller than my current tank, and I fill it to 200psi, I won't be gaining much with using that type of tank.

JBFab: I am not sure what you mean by using that type of tank. I will bring it up to the PV engineer that is working the numbers for me.

Rick Moran: There are several reasons that I didn't want to use hydraulics on this car. For one, the ride is not very comfortable. You can add accumulators to help "soften" the ride, but its nothing compared to an air ride setup. Another reason is the weight added by all the extra batteries. Plus I don't have to charge these batteries every night. Some people still use hydraulics. I have owned vehicles with hydraulics. Just don't like the added problems associated with them. And not sure on your "Don't even think about building or desiging an air tank. As you said, you are having a hard enough time trying to upload pics." comment. What does uploading pics to a forum have to do with having an air tank built?

Like I said, I didn't realize this was even still being talked about guys. So sorry for the late replys. Just was checking back in to get some answers for another welding project that I seen posted on here a while back.

Thanks

Shawn

[steve45]

Steve45: I am not sure where you are getting your information from, but the saftey factor for a pressure vessel in any public building is 3.5. That is an ASME standard. A bridge? Can't comment on the saftey factor of the concrete, but I don't see many pressure vessels being needed in the bridge.


Guess I didn't make myself clear. The safety factor of 10 is not for a pressure vessel in a building, but for the structure of the building itself.

[Blowndakrt]

Guess I didn't make myself clear. The safety factor of 10 is not for a pressure vessel in a building, but for the structure of the building itself.

Ahh gotcha. We were talking about air tanks and pressure vessels and then you posted that. So I thought you were saying that pressure vessels in public buildings needed a saftey factor of 10. Just getting clarification.

Thanks

Shawn

[DaveHath]

O.K. everyone.....let's step back and look at the real problem here. The lack of space in the spare tire well where all of this hardware is mounted. I may be cralzy here......But having been an auto body tech for the last 18 years, maybe all we have to do is relocate the compressors,and batteries. then instal a second cylinder maybe not even to gal or 5 perhaps 3 will do it. First I would determine how much air capacity is needed. then go from there. You could always make the spare tire well bigger.....and if your good no one will even be able to tell how you did it....you will have to take the location of the fuel tank and rear suspension into account.....but once you go custom......I am just thinking outside the box.....the idea of a square or rectangular tank in the trunk of a passenger car just makes me a little less than happy. I hate to think what could happen in a nasty rear end collision......

Best of luck
Dave

[Steve.Carson]

Use nitrogen in your tank and get rid of all the compressors all together. Maybe keep one for a spare in case you run out. Thats what all the true ballers are doing.

[PrecisionSystems]

Buy a saw-zall and make more trunk space? I think I would exaust that option before getting crazy with a pressure vessel. I had to cover an opening on a pressure vessel for hydro... I wanted to save some money and make my own blind flange. You wouldn't believe the amount of reinforcement I had to put on the flat plate to rate it for the 900 lbs I was testing at! 1/2 plate reinforced by 1"X6" flar bar on 2.5" centers.

[Supe]

Even though these last posts are coming in late, I just can't help but find it outright silly that someone is trying to go through the expense and engineering of a square pressure vessel to fit an airtank in a car, after claiming there is no room for it. Trunks, walls, dashboards, inner fenders, heck, even a full frame midsize sedan average about 15 cubic feet of empty space inside the inner frame rails where multiple cylinders can go, and you're saying there's no way you can fit a cylindrical 5 gallon tank? Even the little details, like welding tabs onto pressure vessels and being concerned about having them re-certed. Why? Every nitrous bottle, CO2 bottle, nitrogen tank, etc you will ever see in an automobile is clamped on! Few hundred bucks in nice billet clamps vs thousands worth of R&D in a poor design any way you look at it. This is just overeengineering a problem solution to a problem that was never really there in the first place.

[Hammack_Welding]

Here is an option, if you want to go in the neighborhood of 24x36x4. I think my math is right here. Have you thought about taking 4" pipe, and cut 8 pieces and cap them to be 22 1/2" long. If you measure the volume that gives you 282.6 cubic inches per pipe, or a total of 2260.8 cubic inches in all the pipes. This comes to 9.78 gallons or air volume. Then have them put a 1/2" pipe coupling in the ends, and make a manifold to screw all the pipes to. Would i do it for someone in my shop? no, but it would be better than a flat sided pressure vessel. I have seen lots of "homemade" flat pressure tanks NEVER have I seen one that would be certified or that I would want to be riding around with in my trunk. just my 2 cents.....

[Stuckwldr]

I am curious, could you use a much smaller cylinder set up for much higher cu ft of air or higher presure and run it through a regulator?

[aametalmaster]

I don't screw up much but when i make a mistake i will tell about it to save someone else a headache. Zap is right on the "pillow" tank. I built a tank 24x24x3" and got about 50 lbs of air in it and it rounded out to 5" thick like a pillow and stayed there, but it didn't leak :)
I also had an air bumper on my truck from 4" sq tube 6' long and it worked great. It was factory made with all the pressure stamps on it, but i can't remember the company...Bob

[eburgblue]

Have you ever considered using a spare tire as a receiver? I've seen that done for painting and since you already have one it could be utilized along with your existing tank. Just need to figure out some valving.

[t_oad01]

error

[William McCormick Jr]

Well I would like to double my current air capacity. I have a 5 gallon tank now. So if I could get 10 gallons or more, I would be happy.

A rough measurement gives me something that is 36"X24"x4".

Shawn


By my calculations six, 3 3/4 O.D. round tanks totalling a width of 24 inches, with a quarter inch between them, for clamping. With valves and piping fitting into a 36" space will yield just over 7 gallons of volume. With no pressure.

You could make the tanks 4" leave a quarter inch between them and have just over nine gallons of volume and have a width of 25 1/4" x 36".

You could make the WAK ends or the oriental hat for the tank ends to cut down on space and get ten gallons out of the 4" round tanks.

I have welded up something like this for an airgun bus.

http://www.Rockwelder.com/EastWood/bus/bus1.jpg
http://www.Rockwelder.com/EastWood/bus/bus3.jpg

Sincerely,



William McCormick

[Steven DeMars]

Have you considered going to a 5 gallon high pressure tank with a high volume regulator. This would be a lot cheaper . . . . I can assure you that the volume held in a scuba tank a far more than you will pack in a 20 gallon tank at 150 PSI.

Steve

[Brad Blazer]

Use CO2. Since it is a liquid in the tank, you get a huge amount of gas for the volume consumed.
http://www.micromatic.com/beer-questions/how-many-beer-kegs-dispensed-out-co2-tank-aid-89.html
Caveot: the tank(s) will have to be mounted vertically since it is a liquid.

[GrantH]

Well right now I have a 5 gallon tank and 2 12v compressors. Problem is 5 gallons is not quite enough air to completely lift my car. It will raise up enough to drive it, but it will sometimes rub at that height. I am having to lift the car, wait a few minutes for the tank to fill up, and lift again.

Thanks

Shawn

A buddy of mine that I have known through a forum for a little bit now has 2 rectangular tanks. He works at the IF Custom shop, but I don't believe he is employed there, could be wrong. 200 psi is quite a lot of pressure, and should be enough volume to lift your car/truck fully more than once.

Another buddy of mine here in town has a 2000 chevy 1500 regular cab, short bed. He can play with his truck a good bit without needing more air, with a 5 gallon tank. I don't want to doubt your setup, or work quality, but you may want to go through your system, and check for underlying problems. 200PSI should at the very least pop your front to full lock and your rear off the ground enough to drive with a 5 gallon tank...

[millman52]

I have seen the aftermath of an air tank explosion I wouldn't build one if my life depended on it because it does.

The damage I see from an 80 gal tank going off was an entire 2 car brick garage literally blown apart as if a bomb went off.

It also took out the partition wall between the garage & the kitchen of the house & pretty much destroyed that too.

[txfireguy2003]

If I ever figure out how to attach pics, I can do that. If I make the file size under 150kb the picture is too small to even see.

Here are some links to old photos I took. Its a pic of the car and the other is of the trunk area where I am tight for room.

http://img.photobucket.com/albums/v255/barkleyfan/7-2-06017.jpg

http://img.photobucket.com/albums/v255/barkleyfan/7-2-06022.jpg


Shawn


I don't know if this has been suggested yet, and don't have time to read the entire 3 pages of responses, BUT, from your pic, I see plenty of room to add another tank of equal size to the one you have. Find a different place to mount those compressors and put another tank right next to the one you have. Of course, you know that more volume just means that once you exhaust those tanks, it's going to take longer to refill them.

[joethemechanic]

My vote is for rearranging the sheet metal to fit the tank you need. Seems kind of silly to fabricate a heavy, expensive, and possibly dangerous tank to fit a spare tire well, when you can just make a bigger spare tire well.

My other thought is get some aluminum medical oxygen cylinders (they come in all sizes) and hide them somewhere else in the car (maybe underneath or somewhere) and manifold them together.

I think that the design factor of them running at 200PSI would be enough to make everyone happy. H*ll you could even polish them so they would look cool.

http://www.americanairworks.com/images/Cylinder-Selector.jpg

[wrench]

I would consider switching to hydraulics for my lift medium

[eyepoppin customs]

as a shop that installs air ride from my experience you can add more tanks if you think outside the box (or trunk if you will). you should be able to install 3, 3 gallon tanks in that spare tire well and move your compressors up next to the back wall of your back seat. yes i have seen air tank frames on trucks, but i will not build one. if you have 200 psi in the frame of your vehicle and you get in a wreck the frame could blow out. just my opinion so take it for what its worth but think about it.

[zbounce]

i have a small volume tank i fabracated out of sqare tubing.........6 years ago. that doesnt make it ok though. it has a constant 110 psi on it. When i did build this little tank i was aware about vessels need to be round. long story short i am going to do an inspection of said tank and design something a little.........rounder. no need to take chances when not needed. I take enough already.

[Timberwolf]

Guys, it's a simple solution it can be built square, cheap, light and easily and will withstand thousands of PSI.

It can even be welded up with a hundred dollar 110 volt 80 amp flux core wire feed.

It just needs to be fabricated out of unobtanium.

[Joker11]

I want to know what happened to this project!!!

[daddy]

BOOM!

[Joker11]

Hey McCormick, that bus is sick!
But there is a concern...you are driving that thing around with no valve protection while in transport!!!
So that can't really be to safe either. I doubt anyone would stop you for it, but doesn't that directly violate a DOT law?

[drivethruboy54]

i thought i was the only guy who knew of the unobtainable unobtanium?

[Nitesky]

LOL. Works for a stereo shop and wants to stuff the trunk with more stereo equipment and you can understand why he can't HEAR you. http://new.arboristsite.com/images/smilies/popcorn.gif

[Nitesky]

Hmm, now I understand how to display a smilie from another source