Scuba Tank Explosion - Myth or Reality?

[Drewski]

Well no, they didn't just "say so." They tried. Repeatedly. The video evidence is easily obtainable.

Respectfully, did you read my previous post and do you understand what it means?

The tank that failed hydro had significant metal fatigue that resulted in major volume expansion on testing. It was most likely caused by a lengthy high pressure state (8 HRS or more at near 5000+ psi) prior to burst disc failure. That's not video evidence.

My point is that the tank would have failed during filling or use at some point in the future if not removed from service. You CAN cause a tank to fail if exposed to the right conditions. While shooting one with a rifle (which I've actually done, BTW, both steel and aluminum when full) might be dramatic, it's unrealistic.

Realism is this.

Guess Myth Busters missed one, huh?

 

[Fish in a Barrel]

Guess Myth Busters missed one, huh?

If it's the episode I saw, not really. The Mythbusters were taking on the tank shot from "Jaws". Shooting a perfectly good tank with a rifle is a much different failure mode than a fatigued tank bursting. I don't think what they did is really relevant to this discussion.

 

[ubp_sanity]

REALLY? Because the guys on Myth Busters said so? C'mon, now.

I've got 2 friends who would question everything Mythbusters do. 1 who had a can/bottle of pop explode in his car on a very hot day. And the other who had to pay the cleaning expenses. But Mythbusters said it wouldn't happen.

 

[fjpatrum]

Most of Mythbusters' methods are crap. They do things for dramatic effect and make a lot of false assumptions to base their tests upon. Sometimes they are accurate but mostly they're just entertaining.

 

[Emparo821]

ok i wasn't saying that because the mythbusters had to work hard to make it happen that it WOULDNT happen i just said the likelyhood is very slim. even i know the show is made for entertainment and scientific proof. i've had a can of coke explode in my car too, so it was more of a its a fun episode, and it goes to show that the likely hood is rare, though if it does happen its dangerous.

 

[dave2063]

if your tank did explode in your trunk, then you have probably solved the A/C problem..........

seriously though, possibility of damage caused by jostling, neck o-ring going, burst disk, or even just the valve opening up, let alone overheating......is enough to have me running for cover. IMO, it would always be prudent to keep cylinders out of the sun if possible, and secure, you never know when its going to happen.

 

[badadious]

A friend of mine who is an avid cave diver and experienced technical Instructor was in a Station wagon with a collection of tanks in the back. It was a hot summer day in North Florida and he and another diver were on their way to a site. While they were having lunch at a nearby restaurant they thought they heard an explosion and glass breaking nearby. It was one of the tanks in the car. They thought first that it had exploded because of the damage it did. Upon closer examination it was a burst disc that had let go. The back windsheid was shattered. A back side window also and a large outward dent on the inside of the car where the tank rammed into it. If either of the two guys had been in the car they would likely have been seriously injured or killed.

My thought is even a burst disc letting go is not somewhere you want to be!

The only cases I have heard of tanks actually exploding appeared to be casued by cracks or some other failure in the structure if the tank. Tanks that should not have been in service anyway most likely.

Great discussion by the way!

 

[METCALFD2]

Burst disks are designed to "burst" in order to prevent an overpressurization that would lead to tank explosion. In order for a tank to "explode" a bleve would have to occur (boiling liquid expanding vapor explosion). In other words, the tank would have to be heated to the point that the vapor inside the tank would be expanding at a rate greater than being released through the burst disk resulting in a rapid overpressurization of the tank. The amount of heat inside a vehicle (or in the sun, on a boat, etc.) cannot reach a high enough tempurature quickly enough to accomplish a bleve. The exploding tanks mentioned here were all a result in metal fatigue due to either defects not found in visuals or corrosion not a bleve. I strap similar tanks to my back and run into burning buildings for a living and have never had a bleve or ever heard of anyone else having one. Hmmm............

 

[kbwscuba]

I have had a tank overheat in the back of a truck where the tank was left exposed to the sun. The burst disc did its job and burst. The force from the rapid release of gas caused the 120CF Steel tank to fly across the back of the truck and then spin around for approx 10 minutes. If the burst disc had blown inside the vehicle it could have done significant damage to the vehicle and any passengers that may have been in there. The purpose of the burst disc is to prevent the tank from reaching the tank burst pressure. Remember that tanks are hydostatically tested at 5/3's their working pressure to ensure that the tank will not burst. If a tank is VIP'd annually and Hydorstatic tested every 5 years there is minimal chance of a tank failure due to temprature, but a ruptured burst disc can still do significant damage so keeping tanks in a cool place is still recommended. PS your math is correct.

 

[RonR]

In 40 years of diving, I've seen a number of burst disks go from sitting in the sun- lending credence to the argument that they are not very accurate, as none of these tanks ever got anywhere near the theoretical burst disk pressure. There was lots of noise, but no great danger. However, many years ago, but definitely in this galaxy, I witnessed a fairly dramatic tank failure that just shows how weird things can get:

In a dive shop, with the tank standing upright in the back room on a counter. Sunlight streaming in through the window. Sunlight moves around to shine on the tank- heating it a bit beyond the pressure its particular burst disc could handle. Burst disc goes off, blowing air out sideways and tipping the tank over, off the counter and onto the concrete floor. The valve fractured off as it hit, leading to a VERY LOUD NOISE and the rapid exit from the room of a great deal of dust and paper. It took what seemed like forever for the tank to empty fully- though it was probably much less than a minute. Fortunately there was no one inside the room at the time. Subsequent inspection revealed that the tank had moved little from where it hit the floor, but the valve had knocked a pretty good dent in the opposite wall. :amazed:

The lesson I took away was that if a tank broke at the valve- certainly a potential weak point- I'd rather be in front of the tank than the valve. The valve at a few pounds made a much better projectile than the 30 pound tank.