Question for those who plug their burst disks

[justinthedeeps]

For those of us late arriving to the government conspiracy, can someone explain what is wrong with a 5250 (or whatever) burst disc vs. 'deleting' ?

 

[speleo]

My understanding from a long time ago is the requirement for a burst disk on compressed gas cylinders is a US Federal Dept of Transportation rule that makes it illegal to transport plugged tanks across state lines.

Many years ago certain well-known names in cave diving, pushing the records & limits, would double the burst disks in the plug, and later had custom thick disks made to defeat the burst function completely. All my tanks at that time were set up this way. Also at one point we could buy Subsalve DIN valves from Italy that had no hole drilled in them or burst disk functionality. We never knew if they were unfinished and should have had the burst feature, or they simply didn't require them.

 

[JHumbert15]

For those of us late arriving to the government conspiracy

lol, thanks for the laugh.

I guess technically speaking, using an incorrect burst disk (like a 5250 or 7250) on an LP for example is illegal becuase the disk doesn't match the correct pressure at which it should relieve cylinder pressure (5/3 for AL and LP steels "standard" rated pressure, or 3/2 from the +10% overfill on LP, you end up at the same number either way, 3/2 for HP as they have a special DOT exemption). Over time, these can deteriorate and can end up bursting early when you don't want it to, simply becuase it's old and worn out if you have filled your tank a lot. However, in a fire situation where the cylinder heats up, a higher # burst disk could still relieve the pressure depending on temps and tank pressure. Deleting/plugging means that in a fire situation, if the cylinder heated up too much, it could relieve the pressure by exploding, althought there are arguments that the heat would deform the valve o-ring and allow air to gradually escape out the neck.

 

[Umuntu]

a US Federal Dept of Transportation rule that makes it illegal to transport plugged tanks across state lines.

The US Federal Government has limited jurisdiction … and to invoke jurisdiction in this area they have to reference “the means of interstate commerce.”

The formulation of the requirement in the regulations for burst disks is simply invoking the means of interstate commerce. Unless the state that you live in (or where you keep your cylinders) has an analogous requirement, if your cylinder never crosses state lines, the regulation would not apply.

Good luck explaining that to the LDS or service technician doing your fills …

 

[nadwidny]

Fair enough. Any more info on this? How do you know it was plugged? I found a post you made about this in another thread and did a quick google search but couldn’t come up with much.

I would still bet there was an underlying cause. Out of VIP or hydro, or an old un-taken care of tank. That’s my speculation, because if it was reported to have exploded at 5000 PSI, that’s around test pressure for HPs, and 1000 ish over for LPs. I would not expect an explosion there. Without any more info I guess all we can do is speculate.

The owner of the shop I worked with at the time was the one who examined the gear for the inquest. So I heard about what was up directly from the guy who checked the tanks and compressor for the RCMP. Compressor also had no OPV. Because it happened in 1994 links are very few. I could only find this one - Waterton-Glacier Views (August 24, 1994)

LP Steel 72s. The underlying cause was that it was overpressured.

 

[JHumbert15]

The owner of the shop I worked with at the time was the one who examined the gear for the inquest. So I heard about what was up directly from the guy who checked the tanks and compressor for the RCMP. Compressor also had no OPV. Because it happened in 1994 links are very few. I could only find this one - Waterton-Glacier Views (August 24, 1994)

LP Steel 72s. The underlying cause was that it was overpressured.

Cool, thanks for the info. I guess there wasn’t an “extraneous” cause, but LP72s make sense seeing as they’re known to have thinner walls than modern LPs and can’t take as much overpressurization, so I’d chalk it up to that. Plus, their hydro pressure would be 3750. Them going at 5000 makes sense. Not a concern with the modern LPs that aren’t 1250 over their hydro pressure.

 

[rjack321]

Cool, thanks for the info. I guess there wasn’t an “extraneous” cause, but LP72s make sense seeing as they’re known to have thinner walls than modern LPs and can’t take as much overpressurization, so I’d chalk it up to that. Plus, their hydro pressure would be 3750. Them going at 5000 makes sense. Not a concern with the modern LPs that aren’t 1250 over their hydro pressure.

You're really doubling down on your "opinions" here despite evidence to the contrary.

 

[Tim Clark Diving]

They come as a single unit with different release pressure ratings up to 7250 psi. Pick your poison.

PRD Safety Assembly (Burst Disk Kit)

This PRD Safety Assembly (Burst Disk) eliminates the possibility of mismatched components.

www.divegearexpress.com

 

[runsongas]

the hypothetical issue is liability. i would not want to be in the situation where your house catches fire and one of your plugged tanks explodes injuring a firefighter or your neighbor that is checking if anyone is trapped in the house rather than releasing through the PRD as designed.

 

[justinthedeeps]

Is this "an old burst disc could spontaneously fail" thing actually happening? How many have seen this happen?

How old was the disc?
Was it a disc that was under five years old and/or had been replaced at the last hydro (or not?)