I feel stupid having to ask, but...

Cephlah · Post by **Cephlah** » Mon Nov 06, 2006 12:30 am

So I was diving yesterday at 3tree with a few people from NWDC, and we got on the topic of how devasatating a scuba tank explosion can be. Sounder suggested I take a look on the internet at some of the photos of blown tanks, which I had never done before, but finally did today.

Aside from increasing my awareness tenfold about not leaving my tank unattended while upright, it made me wonder if I have been safely storing my tanks between dives.

Normally, we take our tanks to the shop immediately after diving and have them filled, then store them (on their sides) in the garage until next dive...the philosopy being that the tanks are ready to go the next time we dive. However, after reading several tank explosion stories, I am wondering if it is safe to store full tanks over a period of days or weeks, or if they should be stored with only minimal pressure in them (to keep moisture out)??

Thanks for your advice!

Grateful Diver · Post by **Grateful Diver** » Mon Nov 06, 2006 7:04 am

I always fill my tanks directly after use, and keep them in the garage ready to go. There are currently about 20 tanks in my garage.

I'm not particularly worried about it.

... Bob (Grateful Diver)

diver-dad · Post by **diver-dad** » Mon Nov 06, 2006 7:31 am

There was a problem with a particular make of Al tank that had been made from a material that got brittle and failed catastrophically.

I'm sure someone has more details on this than I, but My understanding is that these are being pulled from service as they have come up for inspection.

This is a rare event.

Also, on MythBusters, they tried to reproduce the Jaws scene where the tank exploded when shot. ... Didn't work (Al tank). Poked a good hole in it, though with a 30.06.

Sounder · Post by **Sounder** » Mon Nov 06, 2006 8:25 am

I too fill tanks soon after I use them so they're ready to go again. I keep them in the garage. If you think about your LDS, they've got several large supply bottles and rental tanks kept full indoors.

CaptnJack · Post by **CaptnJack** » Mon Nov 06, 2006 8:33 am

Yes, the older (mostly) Luxfer aluminum alloy (6351) is susceptible to sustained load cracking (SLC). Basically this alloy has too much lead in it and under load the grains gradually seperate (molecularly) and a crack forms. These cracks are fairly easy to see visually before catastrophic failure. They are also detectable by eddy current inspection, which is now required by federal law on these cylinders.

These cylinders are legal for use, but there have been about 12 to 20 explosions - mostly during filling. This is out of over a million tanks made. These explosions have gotten a fair amount of internet press and now most shops refuse to inspect or fill 6351 alloy tanks.

If you bought an AL tank made after 1989 or any type of Catalina tank you don't have to worry about SLC. These pop up used from time to time, buyer beware. A Luxfer would have the marks "SP6498" on the crown. PM me if you are concerned about the stamps on your particular AL tank.

Store your tanks upright. If there is a tiny amount of water inside you want that on the bottom, which is thicker. Feel free to store any non-6351 tank either full or with ~50psi. Try not to store tanks half full (although I do sometimes) in case of fire the burst disk will not release before the tank ruptures.

Richard
PSI inspector #17040

lamont · Post by **lamont** » Mon Nov 06, 2006 8:34 am

its fill cycles which cause cracks more than storage under pressure.

Sounder · Post by **Sounder** » Mon Nov 06, 2006 8:42 am

Sounds to me like if your tank explodes (and you live to tell about it), you should buy a lottery ticket... if you can win with a 12 in 1,000,000 odds, you're in good shape to play the lotto. $\:D/$

Tangfish · Post by **Tangfish** » Mon Nov 06, 2006 10:46 am

Myth Busters had a pretty cool episode on blowing up a scuba tank to re-enact the scene from Jaws. In the end, the tanks didn't explode, but were propelled around by the hole in the tank.

diver-dad · Post by **diver-dad** » Mon Nov 06, 2006 1:41 pm

Sounder wrote:Sounds to me like if your tank explodes (and you live to tell about it), you should buy a lottery ticket... if you can win with a 12 in 1,000,000 odds, you're in good shape to play the lotto. $\:D/$

Seems to me that wouldn't work - you'll already have used up your luck surviving the explosion in the first place!

sparky · Post by **sparky** » Mon Nov 06, 2006 6:28 pm

i fill my tanks and store them in the bed room closet up right I have been told not to leave them on there sides for any llong peiord of time

besides they fit in the closet better that way I actuly stoe all me rear in the closet on my side of corse

Sparky

Sounder · Post by **Sounder** » Mon Nov 06, 2006 7:53 pm

Good point - don't push your luck. I'd probably get in a car accident on the way to buy the lottery ticket.

If your tank explodes while you're home... change your pants, thank your lucky stars, take a picture, and post it here!!!

Maverick · Post by **Maverick** » Mon Nov 06, 2006 10:20 pm

First off Sparky if you are keeping your gear in your bedroom closet you are not diving enough, because your geear should be wet still from the previous dive when you set off to go diving. My gear is always wet cause I dive so much, well did before I opened my shop.

Ok so back to tanks. I keep all my tanks full and have an AL80 luxfer with 6351 aluminum, i have no problems with crack it was just hydroed to months ago. there have been 16 reported failures and all were at the dive shop while filling them. And lets keep in mind they don't blow up, they just crack at the neck where the valve threads in and air leaks out. at worst the tank will fly around on the fill whip. One failure did cause a death, not by explosion but the employee filling the tank got hit with the tank when it was leaking air.

i did research on this 6351 alloy because I was given the tank and told from the shop it was no good. BS i said it passed hydro so its still good. plus I was certified thru naui and had ony used these 6351 tanks in my six month long course and my instructor had 150 tanks and we filled them all day many times so the chances of one failing are there but come on the odd are in our favor.

the reason I would steer clear of them is because some shops won't fill them and that sucks when you go for air and the won't give it to you.

happy diving

Burntchef · Post by **Burntchef** » Tue Nov 07, 2006 10:10 am

if your tanks are current on there vip and hydro its not something to worry about, i store my tanks upright in the basement full plus i have a 125cft oxygen and a 75 cft aceytelene tank in the garage for welding, the welding tanks i keep a chain around that is bolted to the wall to prevent from falling , if your worried about youthat just get a lashing strap and hook them to the wall.

CaptnJack · Post by **CaptnJack** » Tue Nov 07, 2006 12:22 pm

Avoid buying Luxfer tanks older than 1989 since many places will not fill them regardless of VIP or hydro. You can very well waste your money.

They turn up locally and on ebay quite frequently. Stamped "SP6498". If they have been hydroed at all recently they should also have the stamp "3AL" directly above the SP6498

Otherwise don't worry about this issue. Get annual or more frequent visuals and hydros every 5 years.

dsteding · Post by **dsteding** » Tue Nov 07, 2006 1:14 pm

CaptnJack wrote:Avoid buying Luxfer tanks older than 1998 since many places will not fill them regardless of VIP or hydro. .

Shouldn't that read 1988 (when they stopped using the bad alloy, IIRC)?

CaptnJack · Post by **CaptnJack** » Tue Nov 07, 2006 1:18 pm

Yes sir 1988 and earlier, I'll edit my post.

To stop talking in the negative...

The "good aluminum" tanks are marked "AL3000" on the crown. Stick to those if shopping for tanks.

If you have the old ones, good luck getting local shops to fill them. I think discount divers is the only place.

Tangfish · Post by **Tangfish** » Wed Nov 08, 2006 10:22 am

Posted on Grateful Diver's behalf: Tank Propulsion

Cephlah · Post by **Cephlah** » Wed Nov 08, 2006 9:08 pm

Calvin...TOOO FUNNY - where did you get that?

Also, where did you get your avatar photo - that's suit's a crackup (or should I say an up-crack?)