Scuba tank explodes in St Pete

[luis]

Just keep in mind the gas in a 3000 psi pressure vessel will expand 204 times its volume when released
(3000 psi = 204 atms),
also 3,000 psi = 432,000 pounds per square foot or 216 tons per square foot.

I am sure this was obvious, but it is a good reminder to show some numbers.

[antique diver]

I suspect it would not launch one if it went off underneath one as the gas would dissipate in every direction. The point is there is enough potential energy that it could do it if it is harnessed properly.

I have had a shotgun with an automatic ejector kick out a loaded paper shot shell of #8 birdshot one time on a gravelled road. The primer was dented by a rock and exploded harmlessly as the explosion was not contained in a chamber or barrel. The shell split and the crimping opened up some. If it had been chambered and fired it could a lot of serious damage downrange.

I have used Scott airpack SCBA bottles to inflate rescue lift bags used in vehicle extrications or other rescues that can easily lift train box cars. I regularly use an inflatable jack that will lift your car by placing a hose over your tailpipe exhaust. Expanding gas has a lot of power. It just depends on how the energy is contained or dissipated.

Crimediver,
That is a good point and changes the whole concept of how much energy is actually available! I probably should prepare to eat my previous words... ugh!
Thanks!
Bill

[crimediver]

Bill,
I became a believer in the power of exploding tanks when I was working on my 71 VW Camper windshield washer bottle. Instead of an electric pump to squirt fluid on the windshield, VW used an approximately 1 gallon heavy duty plastic tank that was presurized by air. It had a valve that you used a tire chuck on it to put around 30 psi of air in it. The tank had rounded ends and the thickness of the walls were about 1/4 inch thick. It looked like it was made of polypropolene plastic or something similar.

A hose running from it had gotten a split in it and I unbolted the tank to replace it. I changed the hose and put 10 psi of air in the tank and decided to let it sit for about ten minutes. I wanted to gauge it before bolting it back into place to make sure there were no leaks and that it was holding pressure. For some reason I left it sitting on my lap. About 5 mintes later there was a tremendous explosion that sounded like a grenade going off and the tops of my thighs felt like they had been clobbered by a baseball bat. I was stunned and shell shocked for a minute and did not know what happened.

When I finally got my act together and quit drooling on myself I realized the bottle had ruptured. It did not fragment but a large flap about 3" X 10" had opened up on the tank. My ears were ringing and the tops of my thighs were stinging pretty good. My first order of business was to check the boys to make sure they had not gotten vaporized.

I did not realize that ten psi could make such a commotion. It made a hell of an impression on me, especially since it was on my lap. I can not conceive of something larger going off in near proximity of me as it would really ring your bell. I was glad I had only put 10 psi in it instead of 30 psi.

It scared the hell out of me. I have trained with flash bang grenades and have had them go off near me and they are pretty dramatic but this washer bottle explosion was much worse. But then again I have not had a flash bang go off in my lap either...

[8dust]

...Expanding gas has a lot of power. It just depends on how the energy is contained or dissipated.

the point i was trying to make. I believe Newton's 3rd law may figure in there somewhere.

[captain]

One of the practical jokes we did at work was to put a bit of dry ice and water in a plastic soda bottle, cap it up and roll it under some one's desk. Makes quit a bank.

[crimediver]

I used to work at the shipyard every summer in college as a shipfitter. I would take empty waxed cardboard drink cartons and fill them with about a 50/50 mix of acetylene and O2 from my torch and make a fuse out of an old rag and close up the spout. It would smoulder down into the carton and make a big bang and scare the hell out of everyone. One day I was getting reaady to do the same thing with a plastic bread bag. I had filled it up and tied it off and was getting ready to touch it off when I saw the bossman coming down a catwalk on a big oil tanker I was on. I stashed the bag inside an empty welding rod can so the wind would not blow it away. I forgot about it but a while later a red hot ball of slag from my torch bounced into the can and melted right through the platic bag. When it exploded I thought the tanker had blown up. I believe the welding rod can is some of the debris they talk about orbiting in outer space.

[antique diver]

Crimediver,
The exploding plastic tank story gave me FSW! I'm glad you don't have some body parts in orbit somewhere!

Let's all be ultra careful with high pressure!

[swimjim]

Expanding gas has a lot of power

Just ask my wife. I've been known to clear a room.

[YankDownUnder]

Recently, here in Australia a diving tank was being filled at a dive shop and it exploded. The tank was an older aluminum model, but it was "in test". The fill station pressure was set to the correct pressure. The exploding tank tore off the store employee's arm. These tanks can be recognized by only one letter at the start of the serial number. There is no recall on the tanks.

The test stations have decided not to test tanks in this series. Tanks must be tested annually, so there won't be many in service for very long. I took a pick up truck filled with them to a scrap metal dealer a few weeks ago. The stations simply decided that the owners had enough use for their money and they did not want to take the risk. An individual has less of a risk than a shop which fills tanks all day long.

Some divers get angry, saying the shop is just trying to sell them another tank, so they make a practice of not offering to sell them another tank. They just say the test station won't test them, so they won't fill them.

Steel 72 cu ft tanks do not seem to have such a history. An early German tank used on the Australian Porpoise exploded many years ago. They had a destruction point of 17,000 psi. The problem was traced to water being pumped into them by a faulty compressor. The tank had rusted inside. Tests were rare back then and inspections were rarer.

Divers often switch valves in their tanks and a HP burst disc in an LP tank can be a problem. The disc orifice and disc thickness combination give the correct burst. While servicing valves I have found two discs installed. European valves such as Drager and La Spirotechnique do not have burst discs installed. To meet Australian standards we have to fit them. It is just as about as cheap to buy a new valve because of the labor involved.

I have a set of Broxton triples which once had a blow through type burst plug. When it blew in my car, the tanks flipped over and I had to re-solder the manifold. My windows were slightly open, so I did not loose my windshield from the pressure. It's best to put modern burst devices in your early valves to prevent this. Steve

[scubasteve59]

This is sad. Word for the wise- don't overfill, especially if you own a compressor.

[eskimo3883]

I had my hand on the door about to enter a dive shop when there was a loud explosion. The 8 foot wide store front window was blown out and the entire store turned into a black fog. I opened the door expecting bad news to see the owner come out of the back room with his eyes opened wide by the adrenalin. Turns out the carbon filter housing on his compressor ruptured during a fill. No one was hurt probably because of the small volume of the filter housing. Still, pretty exciting overall. Something to think about if anyone wants to customize compressor filtration.

[Automan]

In the dive shop I often go they had a tank fail which of course was investigated by the health & Safety Executive.

Someone had managed to screw a tank valve into a steel tank which had a different thread.

It put someone in hospital and blew out vent fans and some windows.

I must admit I used to enjoy filling tanks but now every-time I do one it always crosses my mind will it go off bang?

We also tend to pump our tanks to just over 300 bar / 4410 psi (when rated for that pressure) and some dive centres have air banks at 400 bar / 5880 psi to save compressor operation when filling 300 bar tanks.

Our tanks don't have those safety blow out disc gadgets.