Flying and fizzy drink cans

I suppose that a can of fizzy drink in the hold of an aircraft could explode as a result of the reduced air pressure during the flight, but has it actually happened, or is it just a theoretical possibility?

A plastic 2L pop bottle will hold 100psi. At 30,000 ft the pressure is about 4psi

I once brought a giant pack of Lays crisps back from the USA in hand luggage and it blew up into a very tight large balloon.

The difference in pressure between seal evel and 40,000 feet is about 12 PSI so within the tolerance of the can design. In the cabin or hold of a passenger aircraft it's only about 3-4 PSI so insignificent compared to the typical 30-50 PSI canning pressure.

I have seen a can of coke bulged impressively after being ing the cargo bay of a general aviation aircraft but that was because it froze. Even then it didn't burst.

Robert.

Conversely, I saw somebody overturn a trolley load of fizzy drinks cans onto the tarmac outside a supermarket. A whole load of them burst, which was a most impressive, but short lived fountain.

Coclusion - the design safety margin is pretty small.

Martin

I did have a can of fizzy pop dish out the ends one very hot summer's day in the Landrover, where it was sitting above the hot transmission tunnel; it retained the contents, but looked more like a model compressed air receiver.

This can however decided to self open in the kitchen beer cupboard.
It didn't just leak; the end blew off completely, with a very loud bang.

The only other times I've heard such a bang in the house was when an electric drill battery exploded, blowing one cell out to make a dent in the bedroom ceiling. The other was when Jane left a butane cigarette lighter in front of the gas fire; I found some bits from that when we were clearing up whilst moving house.



Bill

Explode, very unlikely. Might go pop and gush if the can was both hot and high in the air, which is an unlikely combination. This website gives numbers for various soft drinks. Coca Cola containing 3.7 volumes of CO₂ quotes the highest pressure, 380kPa at 75°F (24°C), about 55psi. And this paper says: 'Where carbonated drinks are being packed – soft drinks or beer for example - the pack acts as a pressure vessel to contain the internal pressure generated by the carbon dioxide. So cans for carbonated drinks are typically designed to withstand internal pressures of 90 psi or more and the light weight and thin-bodied metal can is well able to meet such a demanding specification.

I'd expect a drinks can to have a safety factor of 2 so one might burst at 180psi or so. Putting the can in a perfect vacuum only increases the effective internal pressure by 14.7psi, and 70psi is less than the '90psi or more' design pressure.

When it comes to explosions, pressure is only part of the story. An proper explosion requires lots of energy as well; a high pressure pulse driven by a large amount of energy within a very short time. Supersonic.

Consider bursting a model locomotive boiler:

• If the boiler is filled with water, the pressure can be raised almost as high as you like with a simple hand operated ram pump. However, although the pressure can be taken sky high, the amount of energy in the boiler is low. Consequently, it fails slowly at the weak points, and doesn't go bang. As the amount of energy available is tiny, injuries are extremely unlikely.
• If the boiler is filled with air instead, the pressure can also be raised by a simple piston pump, but there's an importance difference. The air compresses like a spring and stores energy, rather a lot of it. When the boiler fails, it does so at a weak point, but this time there's plenty of energy in the spring available to tear the structure, like a dam breaking, with a loud bang and good chance of lumps of metal being flung around. Quite dangerous, especially if the boiler fails inside a small room, which further concentrates the energy. A 3psi overpressure is likely to damage ear drums. Although the chance of getting away without serious injury is fairly good, I wouldn't risk it, not even on a small boiler. Eyes are very delicate. This type of explosion is in a different league to a soft-drink can.
• If the boiler is half-filled with water and heated with a fire, a large amount of thermal energy is stored in the boiler. Much more than compressed air. The pressure is the same, but now when the boiler breaks, enough energy is available to do serious damage, not just the bang, but also by violently scattering scalding water, bits of metal, and burning fuel at high speed. Strictly speaking this is just inching into the world of real explosions. It's "only" a BLEVE, or "Boiling Liquid Evaporating Vapour Explosion", not as violent as "the real thing", ho ho! Whilst small model loco sized boilers contain much less energy than a domestic water heater, this one is likely to require an ambulance. Don't do it!
• How about detonating a boiler full of Nitroglycerin? Now we're talking! Weight for weight Nitroglycerin contains less energy than super-heated water, but its chemical disintegration releases energy far faster and hotter than mere steam. The pressure inside the boiler would rise to a few million psi in microseconds, shattering it and anything else nearby. If the boiler were placed on a 3" mild-steel sheet, the plate would be dished and spalled on the 'safe' side. Thinner plates are punctured or shredded. Not sure what the minimum safe difference is, at least 100 metres away, ideally in a bunker, because large lumps of debris are often hurled long distances. Very nasty.

Drink cans barely qualify as explosive. Unless you know different!!!

Dave

As a can of pop has now been escalated to a boiler.

I wonder if anyone has lit a fire under a sealed, water filled and written off boiler with a remote pressure gauge just to see at what pressure and just how a bad one would let go.

There was an article in me or Eim a while back where from (distant memory) a 2” dia 1/16 copper tube had flat plates sil soldered on. It was put in a pit and remotely pumped up. I think it got to over 2000 psi before the joint failed. Our boilers are a lot stronger than we believe, but ……..

I think it was the Reading Society of Model Engineers who did just that. The result was unspectacular. Sadly, I cant find a link to it.

Rod

The Mythbusters TV program have done a number of features with water heaters - the resulting explosions WERE spectacular, the average American water heater being far larger than a model loco boiler.

Rob

As a teenager I had some fun exploding plastic bottles using a fridge compressor. Large 2l PET bottles made an impressive bang. More interesting, and suprising, were the then current white Fairy Liquid washing up detergent bottles. These, much loved by Blue Peter, were made from PVC. They expanded gently at first, like a balloon, as the polymer chains aligned and streached. The then held to about 200PSI before bursting.

A nasty BELVE, which has killed more than once, is a liquified gas can in a bonfire.

I was curious to see just how strong these bottles were, so I parked my van on top of one

I was impressed

There was such an explosion of a brand new boiler in Tasmania in the 1970s. Newly installed steam boiler in the laundry of a convent was hydostatically tested late in the day and the gags left on the safety valves, pressure gauge and high pressure cut out switch. Next day it was fired up by someone who did not know this, and left to come up to pressure. It exploded killing 8 people and injuring dozens, wiping the laundry off the face of the Earth. Estimated pressure at explosion was 600 to 800 psi. Story here LINK

PS ISTR the design factor is usually four times the working pressure. So that would be 600psi on a 150psi boiler. From distant memory, inititial hydrostatic test was twice working pressure. Thence at 1.5 times working pressure at annual inspections.

Thanks for all the interest - I was really only interested in a Coke can type container.

You would have to think the change in pressure differential would be greater with a can left out in the summer sun where pressure inside the can could reach what? 50 psi? 80psi? Maybe even 100psi, when you judge by the spray that comes out of a hot can when opening.

The 12psi difference in atmospheric pressure between sea level and 30,000 feet pales into insignificance by comparison.

Still, I don't think I would risk packing one in my suitcase on a long haul flight. Just in case!

The Newspaper report is more damning than 'Next day it was fired up by someone who did not know...' It starts:

I think that strictly speaking, a BLEVE is where you rapidly vaporise a flammable liquid and then ignite the vapour cloud. They are a particularly nasty form of ordnance.

Neil

Not according to Wikipedia, M'lud.

Dave