Imploding paint aerosol!! Why??
Discussion
I may regret posting this, but given PH's illustrious history of solving the great physics problems of our time, thought I'd give it a go...
Tidying the garage yesterday, sorting through long obsolete paint aerosols. Gave each a quick shake to assess the amount remaining and a light squeeze to check the can was still pressurised. Keep or discard based on the above.
Got to the one pictured below, a little paint remaining, squeezed gently and it imploded in on itself as pictured - very rapidly in my hand! It scared the bejesus out of me - it was violent enough to make me drop the can like a hot potato!!
Now I understand that clearly a significant vacuum had built up in the can and when I squeezed it the slight deformation to the cylindrical shape was enough to allow it to start deforming under that vacuum.
My question is how does a previously highly pressurised can end up with enough vacuum in it to cause this?? Certainly a new one on me...
Tidying the garage yesterday, sorting through long obsolete paint aerosols. Gave each a quick shake to assess the amount remaining and a light squeeze to check the can was still pressurised. Keep or discard based on the above.
Got to the one pictured below, a little paint remaining, squeezed gently and it imploded in on itself as pictured - very rapidly in my hand! It scared the bejesus out of me - it was violent enough to make me drop the can like a hot potato!!
Now I understand that clearly a significant vacuum had built up in the can and when I squeezed it the slight deformation to the cylindrical shape was enough to allow it to start deforming under that vacuum.
My question is how does a previously highly pressurised can end up with enough vacuum in it to cause this?? Certainly a new one on me...
If you emptied it on a hot day, then left it to cool you'd get a pretty damn strong vacuum built up.
The strength of a cylinder is in maintaining the wall shape - as soon as you flatten it the strength is lost, hence crushing itself as soon as you deformed it.
Cool to have it right on that balance point though.
The strength of a cylinder is in maintaining the wall shape - as soon as you flatten it the strength is lost, hence crushing itself as soon as you deformed it.
Cool to have it right on that balance point though.
Krikkit said:
If you emptied it on a hot day, then left it to cool you'd get a pretty damn strong vacuum built up.
The strength of a cylinder is in maintaining the wall shape - as soon as you flatten it the strength is lost, hence crushing itself as soon as you deformed it.
Cool to have it right on that balance point though.
Certainly feasable! The strength of a cylinder is in maintaining the wall shape - as soon as you flatten it the strength is lost, hence crushing itself as soon as you deformed it.
Cool to have it right on that balance point though.
Sounds like thats whats gone on!
Bet that would be ace to watch, like the video of a coke being shaken and freezing up instantly. (Youtube it)
mythbusters did a similar thing recently. They tested the idea of those large tanks that trains lug around. the idea was that when the insides get steam cleaned and afterwards it rains the cooling down would make a vaccum and cause it to implode, they tested it on a small scale using oil drums and it worked.
Sort of related but on a hot day last summer I pumped up a football and off we went to the park for a picnic and a kick about.
After about 30mins the ball spontaneously exploded with enough force to make a damn good impression of some sort of terrorist attack. People within a 500yd radius ducked.
The opposite effect of temperature vs expansion/contraction.
After about 30mins the ball spontaneously exploded with enough force to make a damn good impression of some sort of terrorist attack. People within a 500yd radius ducked.
The opposite effect of temperature vs expansion/contraction.
ambuletz said:
mythbusters did a similar thing recently. They tested the idea of those large tanks that trains lug around. the idea was that when the insides get steam cleaned and afterwards it rains the cooling down would make a vaccum and cause it to implode, they tested it on a small scale using oil drums and it worked.
Well obviously...This is how the very early steam engines worked. They didn't work on steam pressure forcing the cylinder out, they worked on the depressurisation of the cylinder volume as the steam inside was cooled by a jet of cold water, pulling the piston down. These were very low power, but on the plus side, didn't rely on a high pressure cylinder, so build and reliability were much easier.
I'm just thinking back, and the only time I can think of when the can might have been subjected to any sort of temperature extreme might have been the previous time I sorted the garage?
I would have been mid-summer '14 and I did leave a load of cans outside for a few hours - quite possibly in the full sun whilst re-organising some shelves. Guess if the (already old and mostly used) can had leaked pressure down to atmospheric prior to that, the heat of the sun would have warmed it up and maybe forced more gas out.
It was pretty cool in the garage when it collapsed so after cooling it must have held a decent vacuum for at least 18 months, just waiting for someone to give it a little squeeze!!
Cheers for the comments and link.
I would have been mid-summer '14 and I did leave a load of cans outside for a few hours - quite possibly in the full sun whilst re-organising some shelves. Guess if the (already old and mostly used) can had leaked pressure down to atmospheric prior to that, the heat of the sun would have warmed it up and maybe forced more gas out.
It was pretty cool in the garage when it collapsed so after cooling it must have held a decent vacuum for at least 18 months, just waiting for someone to give it a little squeeze!!
Cheers for the comments and link.
ambuletz said:
mythbusters did a similar thing recently. They tested the idea of those large tanks that trains lug around. the idea was that when the insides get steam cleaned and afterwards it rains the cooling down would make a vaccum and cause it to implode, they tested it on a small scale using oil drums and it worked.
It was on Discovery this morning. First thing I though of, when reading the thread title.Gassing Station | The Lounge | Top of Page | What's New | My Stuff