Limitations of air tanks?

[Blitzkrieg]

Hello everyone, I am doing research in an attempt to build something that I had thought of. And one of the things that is troubling me is the pressures the system is going to have to endure. The operating pressures are around 10,000 psi but if it is shut down pressures will accumulate to slightly over 20,000 psi and it should be able to do this safetly.

 

The only problem is I can't find any information on air tanks that have operating pressures of over 6,000 psi. I've concluded that I will most likely have to build the "containers" myself. But I still often ask myself is 20,000 psi too much to handle? I want this thing to be able to last a long time, but with moving mechanical parts and that much pressure pushing on everything from the inside is that even possible?

 

I'd like your thoughts and oppinions if you were trying to accomplish the same feat.

 

I was thinking of tig welding thick high strength steel together, and just hoping it will hold together. But I don't think I really want this thing blowing up in my face when I put it into action. I don't think safety glasses or a face shield will protect you from that. Lol

 

Thanks everyone

Blitz

[John Cuthber]

" is 20,000 psi too much to handle? "

Yes.

You are, essentially, building a bomb. The remaining question is how big a bomb?

[Endy0816]

^The more important question is where are you building this bomb.

 

Link below should give you an idea of the minimum mass needed.

 

http://en.wikipedia.org/wiki/Pressure_vessel#Scaling

 

All kinds of regulations associated and cost would be high. If you can give some specifics we might be able to get the pressure down to something safer to work with.

[Enthalpy]

(1) 138MPa = 1380 bar is perfectly feasible by an engineer. I made hydraulic dampers and hydraulic springs up to 1500 bar. Good steel and proper design permit that.

 

(2) The design is not obvious. Especially, the deformations induce leaks or block pistons.

(2b) I did it with liquids and solids. Gas leaks are much more difficult. Tank explosions are much more dangerous with a gas.

(2c) How much do you know about seals? Some exist up to 1500 bar, but only for hydraulics. It's a job for a specialized company, not for an individual. I learnt it the hard way.

 

(3) I don't see at all what 1380 bar shall bring with air. Such a pressure is well within the bad compressibility region, that is, it costs much tank mass for little air energy. In addition, air exansion brings nothing more if starting from that pressure. Why should you want such a pressure? Did you compute with the proper compressibility, or were you fooled by perfect gas' law?

 

(4) Very few high strength steels can be welded. Especially tempered steel can't be welded by normal means.

(4b) But screws can do that. They must be computed to press the parts together more strongly than the pressure separates them. It takes many big strong screws, which uses to define the size of the parts.

 

(5) Are you sure your design is the best possible? Air is never used at this pressure, for excellent reasons. Pneumatics uses to work with <10 bar. Hydraulics uses commonly 210 or 350 bar, uncommonly 700 bar - and very few seals exist for 1500 bar. Can you tell more about the function?

 

(6) Do you believe to have the necessary knowledge? Without the proper design it will guaranteed not work. With air at 1380 bar, not work means deadly.

[Blitzkrieg]

I'm not currently building it,so there is not danger currently present... yet and 20,000 psi would just be the most 'efficient' in terms of size for the type of element that it is being used in accordance with. It could operate with lower pressures but the lower the pressure the larger it would be and more materials would have to be used, not only making it heavier but making it so it occupies more space. I have thought of a design around that is A LOT more complicated but still functions the same and does operate at a much lower pressure, but would take much more time to build. and probably result in higher manufacturing costs.

 

Sorry for the lack of information I am giving, this project is kind of secret to me and I feel like I've already given too much information.

 

Does anyone know of the highest PSI pressure vessel ever created for curiosities sake? I read the link you posted endy0816 and in the history part it does make it appear that even making a 10,000 psi vessel is a bit too dangerous. I guess I will ultimately have to do the design around, mathematically it would run more smoothly anyways.

 

Thanks guys.

 

@enthalpy

 

Thanks for the additional information as well, you posted while i was writing this. It seems my design around is most necessary.

Edited January 26, 2014 by Blitzkrieg

[Enthalpy]

If you found that a gas at 700 or 1400 bar is most efficient or compact, then you probably made a mistake, especially with the compressibility of gasses, and with the work that can be extracted from them as a function of the expansion ratio.

 

3000 bar, and a little more, is feasible and still resembles a tank. This pressure is much more than any kind of optimum, especially for gasses. It's already a bit more than the optimum for a liquid spring (they exploit the compressibility of liquids).

 

Higher pressures use a diamond anvil, but these are big apparatusses for a tiny volume whose aim is to study the properties of materials at high pressure, not to store a fluid and use its pressure energy.

[Externet]

From curiosity, Say you have the perfect holding tanks for your project; what compressor is meant to be used to bring air to 20,000 psi ?

 

And what volume is the tank meant to hold ?