Blast Loading on Pressure Vessels Mounting Structure

[Aerograce]

Hi all,

Do you have any idea on how to securely mount a compressed air tank to make the structure blast-resistance? i.e. it doesnt fail even the tank explodes. The tank is rated at 4500 psi, 50cu. From what perspectives I can improve my design to secure the tank and analyze the loading in the case of explosion? Thanks a lot if anyone can provide any advice

 

[gr2vessels]

If the blast is the only external load on the compressed air tank, you'd be better off putting an explosion proof enclosure around it. Thick, solid, impervious to any impact of explosion that the exclosure was designed for.
Cheers,
gr2vessels

 

[Aerograce]

Hey @gr2vessels! Actually I mean how do I mount this tank to make the tank blast-resistant? i.e. it doesnt fail even when the tank explodes so there wont be flying fragments and all that. The tank doesnt create flying fragments btw, its made out of carbon fibre

 

[racookpe1978]

No. The blast 'container' will - like a pipe bomb's pressure vessel - only let the internal pressure go even higher before catastrophically yielding. And causing even more damage.

The violent release of pressure from the 4500 psig tank must be either gradually relieved (through the relief valve to a vent pipe best of all away from the tank itself and the fire (??) around the tank;
or
the tank and its square plate must be surrounded by a very, very thick wall "blast shield" with an "open roof" so the explosive force (the vented energy from the compressed or flammable fluid as it heats up from fire) goes "up" into the air above the tank. Assumes an outdoor location obviously. This vented enclosure has been used for explosive factories since before DuPont.

The square plate now used is sufficient to prevent the tank from falling over - unless run into by a vehicle of some kind.

Looking at the image above again:

The steel PLATE at the bottom won't be likely to fall over, but the two little bitty sheetmetal angles are only mounted with two screws each to the small (wood?) square, then those angles are mounted by two more screws to the skinny sheetmetal (al ?) vertical members, which are then tie-wrapped to the other vertical.

So that total assembly as a whole is very, very weak against side loads, impact loads, or being kicked over by a passing pedestrian.

As above, you cannot put the PV into a bigger PV and expect to improve safety. You CAN direct the vented gasses from the relief valve somewhere else that is safer, and you can direct the "blast" fragments and pressure wave safely "up" towards free space if outdoors. You should improve the physical mounting with something more than sheet metal bands and wood screws.

 

[gr2vessels]

Haha, we might have a problem with blast resistance definition;- an explosion in vicinity might affect the integrity of your tank, hence you need measures to strengthen the tank or build around it a protective structure. That is blast resistant.
Cheers,
gr2vessels

 

[Aerograce]

@racookpe1978, Yeah I know the physical mounting is pretty weak. What kind of structure would you suggest for me to securely mount this thing? Or at least, more secure than this?

 

[racookpe1978]

1. You're aerospace engineering. Do you care about weight (or corrosive atmospheres) - in this specific instance?

2. What is the diameter and height of the "50 cu" tank?

 

[racookpe1978]

it's still not clear if the blast is external - coming from an assumed side or direction, or internal as the PV blows up.

 

[SnTMan]

"A problem well stated is a problem half solved"

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[Aerograce]

Dear all,

Thanks for the kind input. The tank is basically a 50 cubic inch carbon fibre tank charged to 4500 psi, 12 cm in diameter and 20cm in height including the regulator. The tank carries compressed air and I have converted its internal energy to TNT equivalent, it is 15g TNT after conversion. The compressed air tank will be used to supply air flow in a space propulsion ground test facility. My supervisor has informed me about the safety precautions and one of the important precaution is, the tank must be properly mounted so even in the case of tank explosion, the mounting structure will not become flying fragments.

In the drawing above, I secure it with a bent that can be easily bought in hardware shop, and a thin bar with ring hose clamp. I didnt work out the specific dimension but Im trying to look up blast theory to determine the material and dimension. But apparently the mounting structure is not well designed. For example, its better to have a one whole piece of bent instead of a bent plus a thin bar in terms of structural integrity. Apart from that, i have no idea how to improve the mounting structure design though. So could you give me some advice on that?

 

[gr2vessels]

I think you got all the wrong way around;- apparently you are not concerned that the tank itself will become a missile in case of failure and you are looking for a solid mount. Don't use any mount, get rid of that timber base and glue on a thick block of concrete a piece of polystyrene foam with a hole in it to sink the 'tank' in it. In case of tank rupture, the bits of foam will spread on the background but the tank will penetrate anything that stays against it (missile). Those bits you try to use are not suited for clamping anything that stores energy. Best thing to use the tank to its MAWP, do not exceed that and you don't need to worry about explosion.
Cheers,
gr2vessels