Burst Disc Blew! 2 -Questions?

[moneysavr]

OK Guy's need some help,
make a long story as short as I can,Just had a AL 80 tank of mine NITROX Cleaned and cert at my local LDS,It had a new Hydro,and a vis,but now a valve-NITROX and tank cleaned,the valve is a Sherwood ,I had the tank filled with EAN 36,and had it with my other dive stuff in cool basement,ready for our vacation in a few days,
Wife came home from work and a few moments it sounded like we had a v-12 rocket in our basement it scared the CRAP out of her,im at work and get the call.
No the tank was not near the furnace!,I store all my dive stuff in a cool part of basement,
Tank was a short fill 2900 PSI the LDS owner told me at the time of the pick up,it was fine by me do to I was going to do some equipment and weight changes fresh to salt,7mm to 3mm .
1. if this would happen at depth,seems like with one tank your screwed? I would think the surge or pressure drop would cause your reg to freeze with the mass air drop,also the air shooting out of the ports would seem to me like cutting nozzles ouch that would feel real good on your back! and just to think now you have no air! and all this blast of air would give you a spin?
Well I look forward to some help on this,and know that it is a one in a million chance, that this would blow at depth,but not takin a chance on a copper disck and my life!
but now I know im going to some type of a pony set up,before I stick a toe in he water!
Brad

 

[liberato]

Well, there would be less chance of it happening at depth (less pressure differential) but your story is another data point that the "one in a million" events sometimes happen. Thank goodness it is a story you get to tell.

 

[Quarrior]

Think of it this way. Take a balloon and keep adding air to it until it pops. That's what a burst disk does for you, it pops when your tank is being filled or stored in the hot sun. It is a safefty valve of sorts.

Now, take the same balloon which is full of air and start letting air out of it. Will it pop without being poked with a pin? Nope. Same thing with the burst disk. Your tank is continually losing pressure as you dive. How can an over-pressure safety valve let go as the tank is being depressurized?

 

[NEWreckDiver]

That is why you practice your CESA for shallow dives. Anything deeper, I carry a pony bottle or dive doubles. Anything can happen, a burst disk fails, a hose gets cut, a o-ring fails.

If you are diving deeper with a single tank, consider taking a pony. More than likely you will never need it, but as you can see, it is nice to have just in case.

Good Luck to you.

 

[DA Aquamaster]

It's a good idea to replace the burst disc when you do the VIP. Cost is normally $4 to $7 depending on the shop but it is cheap insurance.

The burst disc flexes a bit with every cycle and over time they get tend to weaken. Add a little salt water corrosion to the outside of the disc and eventually they will fail at well below their rated pressure.

If you look at an old burst disc, they are usually pretty cupped where the disc is trying to extrude through the center hole in the retaining screw.

Normally a burst disc will fail during a fill or less frequently, shortly after a fill (a few minutes to a few days).

 

[PvilleStang]

Think of it this way. Take a balloon and keep adding air to it until it pops. That's what a burst disk does for you, it pops when your tank is being filled or stored in the hot sun. It is a safefty valve of sorts.

Now, take the same balloon which is full of air and start letting air out of it. Will it pop without being poked with a pin? Nope. Same thing with the burst disk. Your tank is continually losing pressure as you dive. How can an over-pressure safety valve let go as the tank is being depressurized?

Hate to call BS, but yeah... Burst disks are metal, and thin, and have great amounts of pressure on little surface area. They wear over time, and again, the salt water will do a number on them. Also, if you store it in a humid place, your burst disk may take on slight bits of corrosion. When you take in all possible variables, a disk is a piece of equipment that really should be taken care of (switch them out annually). And by the way, blow up a balloon and sometimes you will notice a small pinhole in it. It may not do much full, but sometimes when you release pressure, the hole can cause an explosion... Put that into context, and you might find something!

 

[Diesel298]

It's a good idea to replace the burst disc when you do the VIP. Cost is normally $4 to $7 depending on the shop but it is cheap insurance.

The burst disc flexes a bit with every cycle and over time they get tend to weaken. Add a little salt water corrosion to the outside of the disc and eventually they will fail at well below their rated pressure.

If you look at an old burst disc, they are usually pretty cupped where the disc is trying to extrude through the center hole in the retaining screw.

Normally a burst disc will fail during a fill or less frequently, shortly after a fill (a few minutes to a few days).

wow thats a expensive burst disc
you can get them for about .40 at home depot , and ive never seen one of theres fail

 

[in_cavediver]

OK Guy's need some help,
make a long story as short as I can,Just had a AL 80 tank of mine NITROX Cleaned and cert at my local LDS,It had a new Hydro,and a vis,but now a valve-NITROX and tank cleaned,the valve is a Sherwood ,I had the tank filled with EAN 36,and had it with my other dive stuff in cool basement,ready for our vacation in a few days,
Wife came home from work and a few moments it sounded like we had a v-12 rocket in our basement it scared the CRAP out of her,im at work and get the call.
No the tank was not near the furnace!,I store all my dive stuff in a cool part of basement,
Tank was a short fill 2900 PSI the LDS owner told me at the time of the pick up,it was fine by me do to I was going to do some equipment and weight changes fresh to salt,7mm to 3mm .
1. if this would happen at depth,seems like with one tank your screwed? I would think the surge or pressure drop would cause your reg to freeze with the mass air drop,also the air shooting out of the ports would seem to me like cutting nozzles ouch that would feel real good on your back! and just to think now you have no air! and all this blast of air would give you a spin?
Well I look forward to some help on this,and know that it is a one in a million chance, that this would blow at depth,but not takin a chance on a copper disck and my life!
but now I know im going to some type of a pony set up,before I stick a toe in he water!
Brad

First, I'd take this back to the LDS as its likely a poorly installed burst disc. (I saw one fail that way). Either way, I want the tank re-cleaned due to condensation inside and since he just did the clean, he ought to do it for nothing.

The second part about the jets/nozzle effect is nothing to worry about. The burst disks are designed to vent without applying force in any direction to the tank. If they did not, then the tank to topple over and cause even more damage.

Lastly, if it went underwater, it would ruin your day. You should get another air source or to the surface and close your tank valve as soon as safely possible. If you can't get the tank off prior to losing all pressue, you should consider rebuilding your reg in case of water entering the first stage via the second stage.

 

[pt40fathoms]

Burst disk replacement "should" be part of the annual VIP. If you paid to get the tank and valve cleaned for Nitrox use, the replacement of the burst disk should not even be debated and simply should have been done...period! The moment you remove the burst disk from the valve in order to clean the valve you cause damage to the burst disk. The damage done by simply twisting the retaining nut loose on a torqued down burst disk may seem small, but it is enough to make it unreliable for reinstallation.

You are owed a new burst disk, a refill, and an apology at the very least.