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Derrick · 06-20-2003, 02:26 PM,

What should a burst disk be rated for on a 3400 psi HP tanks? 4000? 5000?

Derrick

ccuda · 06-20-2003, 04:47 PM,

3500 psi

JoelW · 06-20-2003, 06:07 PM,

Having at one point in my career done product development on burst discs, not for scuba tanks though, the burst pressure is not the rated working pressure of the tank. Or even close to it in a lot of cases. The discs that are used in scuba tanks are about the least complicated and as a result the least forgiving for getting close to their rated pressure. Flat discs don't like operating at more than somewhere around 60%-80% of rated burst if the owner of the disc wants them to last. I think that for a 3500 psi working pressure the disc rating will be somewhere over 5000. That should still put the disc burst well below the failure rating of the HP tank.

JoelWl

06-21-2003, 09:25 AM,

Just get SS shims instead of burst disks and eliminate the failure point. Your tank o-ring will blow anyway before the tank blows...

Derrick · 06-21-2003, 06:39 PM,

Is replacing the burst disks with SS shims ok DOT?

06-21-2003, 08:11 PM,

Nope, but the DOT is the least of your concerns. It's only diveshops who'll start making a fuss about it if they know (or rather, if they don't know any better). SS shims just replace burstdisks - I wouldn't recommend them for AL, but especially for LP steels they're great. Depending on what type valve you have, you can probably get them from .

06-22-2003, 09:02 AM,

duh, whats an SS shim?

06-22-2003, 10:08 AM,

It's a small Stainless Steel disk, which replaces the copper burst disk. It's much tougher so you won't have to worry about it blowing. I've heard of a couple of recent incidents of burstdisks blowing during a dive, so it can and does happen. Why have this failure point?

Also, I know of people using plugs instead of burstdisk assemblies. They're just bolts that screw into the burstdisk threaded part of the valve. Although this is the best way to go in terms of safety, diveshops can tell they're not a burstdisk assembly and might refuse to fill your tank.

BTW, all valves and manifolds sold in Europe do not have a burstdisk, yet they've never had any problems with tanks exploding because of this. I wonder why?

Inspirationdiver · 06-23-2003, 08:46 AM,

DRE is right about the European standards. The bottles that are for my Inspiration have valves in them made and distributed in England. These valves have no burst disc assemblies in them. The tanks are also rated to higher pressure than the identical Faber 20 cu ft tanks sold in the US market.

**freedivernd** · 06-25-2003, 09:37 PM,

DRE posted earlier:

Quote:\"Nope, (insert)as per Derrick asking about it being o.k. with the DOT (end insert),but the DOT is the least of your concerns. It's only diveshops who'll start making a fuss about it if they know (or rather, if they don't know any better). SS shims just replace burstdisks - I wouldn't recommend them for AL, but especially for LP steels they're great. Depending on what type valve you have, you can probably get them from .\"

Now, I'm just asking...and this only sounds so harsh because I believe there is a safety issue here but..
DRE, do you suppose the dive shops might make a fuss because you're talking about tampering with THEIR safety? or MINE? Or isn't safety an issue here? DOT might be the least of a divers concerns but might also be one of the bigger concerns of a dive filling station (right up there with the tank exploding, which if a tank is going to explode.. that's where it's going to happen almost everytime). DOT specifies that during every 5 year hydro the burst disk has to meet certain specifications and because those specs are hard to measure they generally just get replaced at that time by the place doing the hydro. Think there's a reason for this, or no reason? -- and no, you can't get ss burst disks from (at least not on their site I didn't find them)
From what I understand, a burst disk going into relief stage during a dive is about as common as getting struck by lightning and the type of thing that would increase the odds are things like occasionally over filling the tank and that a burst disk will more likely fail (a misnomer, read "work") during filling, which is also, as I stated above...if a tank is going to explode.. that's when it's going to happen. Do you stand by your tank when it's getting filled? I guess I'd prefer not to.

Fred