Scuba Tank Explosion - Myth or Reality?

[wetfox]

Well, I'm late to the thread but I offer a few tidbits. The purpose of the burst disc is to prevent cylinder rupture by giving way well before the burst point of the cylinder. There is nothing that can happen to the burst disc that can make it stronger and theoretically not burst soon enough. Corrosion, metal fatigue, etc., can only weaken the disc leading to the disc bursting at a lower than intended pressure. One possible concern is installation of an incorrect disc, that is, one rated for a different cylinder service pressure. It is not uncommon to see valves set up with discs intended for 3,000 psi service (standard 80s) put onto older steel 72s, which have a service pressure (after the first hydro--unless once again + stamped) of 2,250 psi.

Cheers,

Arnie

 

[branon]

I had two burst discs go in two different tanks (out of 3) that were stored in a storage closet at my old house in North Carolina. The temperature was unlikely to have reached 170F, but certainly got over 100F. Current hydro/VIP.

One of my dive buddies had a burst disk blow in a tank sitting in his parked SUV here in Florida during Summer - the burst disk actually blew out the back window. Current hydro/VIP.

Oddly enough, in speaking to a local dive shop this week, they've had a number of burst disks blow during fills, but never had a tank explode - they don't submerge the tanks in water during fills.

The whole point of the burst disk is to blow before the tank does. While they shouldn't blow during regular conditions, common sense should always be used when using any pressurized container - tank or otherwise.

 

[Rhone Man]

I worked as a DM for about 9 months before I went to college, and we used to have quite a few burst disks go in the Caribbean sun. Not like an every day thing, but probably every month or so we would have one. I never saw one blow during a tank fill though - only ever when they were left out in the sun.

I have only ever heard of two catastrophic tank failures in my life though, both during hydrostatic testing. I am sure that there has been one somewhere in the world at some point outside of a hydrostatic test, but it must be an awfully rare event.

However, when I was in Truk a number of their tanks looked decidedly old and rusty and not particularly recently hydro-ed, and they used to give "hot fills" to about 120% of normal working pressure (so it would cool back to about 110%). Just to be on the safe side, I usually absented myself to the sun deck during fills.

 

[Rhone Man]

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!

I think part of that is because the station wagon is an enclosed environment. I have been relatively close to a burst disk that blew (say 10 feet or so?) in an open air environment, and the only damage was to the inside of my shorts.

 

[MartynCC]

Just wondering if scuba tank explosion due to tank overheating is a reality. I had students ask that question as it relates to transporting tanks in a car. For years I've given them a standard answer that was given to me years ago by my instructor: "well, yeah, it could happen, so shield the tanks from the sun in the back of your SUV, etc. etc." Now that I have done a bit of research into the topic, I feel kind of dumb...

1. Through my research I found out that the highest temperature ever recorded inside a vehicle sitting in the sun was 170F.

2. According to my son's High School physics book, gas laws would dictate that for every 1F temp rise inside a closed container filled with air, you can expect a 5PSI pressure increase.

3. Assuming the tank is put into the vehicle at room temp 70F, and the temp rises to 170F, the temp rise is equal to 100F. This causes the pressure to rise by 500PSI.

4. OK so now my 3000 PSI tank is, at the most, at 3500PSI.

5. Burst discs are rated at 140% of rated pressure so on a 3000PSI tank they would not blow until 4200PSI.

That leads me to a conclusion that even a burst disc blow is a very unlikely event at 3500PSI (170F) not to mention the actual tank exploding.

Am I wrong here. What am I missing? Can you guys and ladies shed some light on this. I searched the SB but could not find any info on this topic. Thanks.

well I am sat here in the Philippines and was studying about hydrostatic tank testing and according to the PADI book the tanks are tested to 5/3 of their normal operating pressure.Put another way thats add 66% to a cylinder of normal operating pressure of 3,000 meaning it will be taken up to 5,000....so I would think an increase of 500 under temperature would have no effect on a health cylinder or am I missing something?

 

[Wet Whiskers]

It appears that the "explosion myth" has been sufficiently answered for you. As an Instructor and an Equipment Repair Tech may I suggest a tid-bit to add to your students education? When discussing cylinders, VIPs, & hydro testing in the Equipment chapter I add that at the very least a new burst disk should be requested when taking the cylinder in for 5 year hydro testing. Preferably, have the valve overhauled to put in fresh o-rings, packings, and a new burst disk. This will reduce the chances of a 10-15 year old disk finally weakened enough, letting loose at an inopportune time.

 

[scubaH2O]

Just reading this thread for the first time. Here in the Northeast USA, I do recall a number of burst disk failures all resulting from leaving them in a hot trunk. Like many of you stated, the only damage was the nerves of the driver and passengers. I was surprised to read in some of your posts that damage occurred from disk failure. My understanding of the multi-port expansion disks is that they release in such a way as to not cause traveling of the tank.

 

[Jimmer]

A shop I occassionally deal with was using their water bath full of simple green to O2 clean tanks one night. A customer came in and requested an air fill. They hooked up the whip, tossed it in the water bath tank full of simple green or whatever detergent they were using, and had the burst disc blow in the water. The story goes that they lost the fill panel under all the bubbles. Wish I had been there to see that one!

 

[Dewit2it]

Here's what will happen if one catastrophically fails. I had one of these back in the 80's.

About the Scuba Tank that Exploded

 

[Dewit2it]

I have also found that keeping the cylinders on the bottom of the trunk with dive gear on top keeps them quite cool. My wetsuit might be toasty warm, but my cylinders aren't!