Grrrr . . . (old style, 3 piece burst disks!)

[OMyMyOHellYes]

That makes the last two valves rurnt.

Last one was a Themo that had rupturated and somebody just slipped in a new disk on top of the rupturated one and torqued it back down, but I couldn't get the ring-remnants of the oldest disk out period (did not apply oxyacetylene solution).

This one was a newish, in great shape Blue Steel valve, just going to replace the burst disk assembly because it was fresh out of hydro (actually 11 years old). Copper plate was a pain to fish out, but the nylon washer was welded in place, it seemed. got it out but at the cost of the valve (marred surface under the washer with the hook/probe it finally took to get the blasted thing out...... which I'm gonna assume the surface will not be no bueno for sealing going forward).

I suppose that the cost of a new valve at $45-50 is not horrible, just the seat, o-rings, nylon washers and burst disk would have cost to O/H valve would be a lot less!

The pre-assembled assemblies are so much more betterer.

Grrrr . . .

Oh, well.

 

[Angelo Farina]

Burst discs are a problem and a possible danger. They are forbidden all around the world, except in US...
Here in EU we have 300-bar tanks with DIN-300 valves (usually dual valves) which are much safer.
And no burst disc!
It is really a pity that US does not allow using these tanks.

 

[rhwestfall]

I'll run a screw through the center of the stuck copper disc to pull it out with a hammer claw or similar rather than trying to pick it out at the edges...

 

[Gone for diving]

Definitely not correct...
But a bit of anaerobic sealant on the surface......

 

[OMyMyOHellYes]

I'll run a screw through the center of the stuck copper disc to pull it out with a hammer claw or similar rather than trying to pick it out at the edges...

The metallic disk itself, I like the screw solution.

But it was a washer in both of these instances (one was the nylon washer and the last was the edges of the old burst disk (when the center went, it made the outer edge nto a copper washer). Nothing to grab. Just the inside edge to try and capture. I had applied some pressure that actually popped the disk itself loose.

 

[Tracy]

If the disc is stuck, I usually just hook it to the fill whip and blow it out.

 

[Bob DBF]

It is really a pity that US does not allow using these tanks.

Has nothing to do with the tank, if we had your 300 bar tanks, it would still have to have a burst disc.

 

[Angelo Farina]

Has nothing to do with the tank, if we had your 300 bar tanks, it would still have to have a burst disc.

There are no 300 bars DIN valves with a burst disk I know of...
I think that these 300 bars tanks are not widely employed in US because the lack of suitable valves. Of course the tank itself is not the problem...

 

[tmassey]

There are no 300 bars DIN valves with a burst disk I know of...
I think that these 300 bars tanks are not widely employed in US because the lack of suitable valves. Of course the tank itself is not the problem...

No, the tank itself is the problem. The valve is also a problem, but that’s a separate problem.

In the United States, in order to be filled in a commercial setting, meaning from a dive shop, a tank must have a DOT certification. European tanks don’t have DOT certifications.

There is a UN certification for tanks. I have seen them here in the United States as bank bottles, but never as SCUBA bottles. Even if a tank has a UN certification, it must be marked with USA in order for that certification to be valid within the United States.

If you’re interested, here’s a small PDF that talks about using UN certified bottles in the United States. It’s mainly focused on bank type bottles and other large vessels, but the law is the same for scuba tanks.

https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/docs/PHH50_0078_0706_UN_Cylinders.pdf

Now if you want to ask the question of why no one has built a 300 bar/4500 psi scuba tank valid for use in the United States, that is one I can’t answer. It has nothing to do with whether it is possible to add a burst disk or not. I have 5000 psi bank bottles that have valves with a burst disk. There’s nothing magical that prevents that.

To maybe possibly bring this thread back on topic: thank you very much for describing your trials and tribulations with three-piece burst discs. I have not had the misfortune of having to replace one yet, so I appreciate the wisdom being shared. Regardless of anyone’s thoughts about the wisdom of burst disc on scuba tanks in the first place, here in the United States we have to deal with it whether we’d like to or not.

 

[happy-diver]

So you scratched up your brass trying to save a washer you can punch from a plastic bottle