# multiple wall, pressurized gas pressure vessel

I was thinking about interesting powder metallurgy method, hot isostatic pressing. Often thick steel walled vessel is required increasing costs and decreasing the prevalence of this technology.

This led me to consider say several metal spherical concentric tanks. I wonder if the inner most tank is at very high pressure more so than the metal wall could handle but was counter acted mostly by a second concentric tank pressurized nearly to the same pressure but slightly less, and so on so forth until finally the outer most tank was low enough pressure to be contained.

I'm not really sure of the net forces? Would there just be large compression forces on the tanks? Would there be a large net force inwards or outwards? I ask because it would be interesting if say I had two balloons and everything worked out such that say I had a 99% chance of rupturing balloon A at pressure P_1 but it balloon B had less than 1% chance of rupturing at pressure P_2 and I found both had low chance of rupturing at respective pressures with balloon A contained inside balloon B. Maybe this help to understand the idea I wonder about, perhaps it is a fallacy I'm not sure.

• No imagine the scenario where you gradually make the concentric tanks closer to one another, making the gap between gradually thinner and thinner until the amount of gas between each one tends to zero... You're just describing a thick walled tank, with many more potential leak patha! – Jonathan R Swift May 31 '18 at 12:13
• @JonathanRSwift this is not true, because for a single thick tank the internal stress field is continuous, but for multiple shells with small gaps between them the circumferential (hoop) stress can be discontinuous between the different shells. However making such a structure with small enough geometric tolerances so that it worked as the OP would hope would be a very hard problem. With "large" gaps between the shells, the OP also needs to think about how the pressurized fluid in the "gaps" will be contained! – alephzero May 31 '18 at 12:34
• A better version of your idea would be to shrink-fit the shells around each other somehow, so that with no internal pressure, the inner shell is in compression. – alephzero May 31 '18 at 12:36
• @alephzero best idea, in fact a technology already used in larger gun barrels for range and accuracy. – Solar Mike May 31 '18 at 13:50
• @Jonathan R Smith, I had wondered if perhaps by some conservation requirement that the best case would simply be matching the pressure loads of a single homogeneous shell, but I think perhaps the mass, kinetic energy adds something from a chemical or continuum dynamical perspective? Any ways thanks all for taking time to entertain this concept, which is probably only fully explained in much more technical terms than I have made. It does seem open to empirical testing and experimentation though? – user10585 May 31 '18 at 15:26