The Isolation Manifold, lessons not learned and a small defence of the IUCRR

[Russjstewart]

Sure. It could be those things.

It almost certainly won't be, though. A neck o-ring isn't going to randomly explode underwater (though I have seen that once). I've seen burst discs go, of course. During filling.

But valve handles, the mechanisms under them, I've seen them go on a meagre handful of occasions.

Being able to isolate was pretty useful.

Off topic, but I have personally experienced a burst disc failing, weeks after being filled, in the middle of the night after an average day temperature wise. It was like something out of the exorcist.

 

[Celt]

Off topic, but I have personally experienced a burst disc failing, weeks after being filled, in the middle of the night after an average day temperature wise. It was like something out of the exorcist.

It's definitely something to watch out for and have checked, I personally wouldn't have them on my twinsets, if they came with burst discs I'd plug them.

 

[cerich]

It's definitely something to watch out for and have checked, I personally wouldn't have them on my twinsets, if they came with burst discs I'd plug them.

Interesting enough, burst discs are regulated to be there in the states(and many countries) but not in Europe. Different conclusions as to are they a solution to a problem, or a problem in search of a solution.

 

[boulderjohn]

Interesting enough, burst discs are regulated to be there in the states(and many countries) but not in Europe. Different conclusions as to are they a solution to a problem, or a problem in search of a solution.

Years ago, I had my twin LP 108s filled at a South Florida dive shop in preparation for an ocean deco dive. Since it was not going to be a seriously long dive, I was happy with the typical LP fill. When I picked up the tanks, the tech told me he had detected a tiny leak in one of my burst disks and fixed it. I assumed he meant that he had put a wrench to it and given it a tiny turn, and I thanked him.

Then I went north to Marianna and had them filled for a cave dive with a typical cave fill. It was then that I realized he had replaced my high pressure burst disk with a low pressure burst disk. I am sure everyone who was at the shop that day will remember it.

 

[Akimbo]

Interesting enough, burst discs are regulated to be there in the states(and many countries) but not in Europe.

Which is another one of those "safety" additions that introduce additional risk. Nothing is free.

One of the most important lessons of my life was that piling on safety and backup systems introduces more failure modes and conspire to make rapid problem diagnosis difficult.

I was on the US Navy's Mark II Deep Dive (saturation) System that was built to support the Sealab III experiments. It was mind-numbingly complex and designed by a committee of government employees and sailors with very little actual experience — which to be fair, nobody had in the mid 1960s. Sure enough, someone died and the program was cancelled. I came onboard after 3 years of overhaul and helped to Band-Aid the many design and human factors flaws.

Example for Newer Divers​

No doubt, SPGs (Submersible Pressure Gauges) are a net improvement to diver safety, until they read higher than actual pressure. I don't think that many people will argue that the net effect of SPGs are not positive, but they are not without added risk and complexity.

Fortunately they quickly figured out how to negate the risk of an SPG hose failure. The first SPGs had a full diameter/flow orifice on the hoses and first stages plus they used the same port size as the LP hoses.

 

[Celt]

Interesting enough, burst discs are regulated to be there in the states(and many countries) but not in Europe. Different conclusions as to are they a solution to a problem, or a problem in search of a solution.

I believe the approach taken in Europe is the accidental release of a dangerous gas because of a faulty burst disc would be a greater danger.

 

[Celt]

Years ago, I had my twin LP 108s filled at a South Florida dive shop in preparation for an ocean deco dive. Since it was not going to be a seriously long dive, I was happy with the typical LP fill. When I picked up the tanks, the tech told me he had detected a tiny leak in one of my burst disks and fixed it. I assumed he meant that he had put a wrench to it and given it a tiny turn, and I thanked him.

Then I went north to Marianna and had them filled for a cave dive with a typical cave fill. It was then that I realized he had replaced my high pressure burst disk with a low pressure burst disk. I am sure everyone who was at the shop that day will remember it.

In the US what happens when a tank is sent in for a hydro, isn't the disc burst pressure matching the hydro test pressure, is the disk replaced after the test?

 

[Akimbo]

In the US what happens when a tank is sent in for a hydro, isn't the disc burst pressure matching the hydro test pressure, is the disk replaced after the test?

Valves are removed before hydro so are not hydrostatically tested. A good dive shop would visually inspect the outside and recommend servicing the valve if there are indicators like corrosion or the valve stem is not running smooth.

 

[Akimbo]

For new divers and divers where blowout discs are not used, they are usually on the side or back of the valve. They are just a thin metal disc held in a socket and designed to burst above the working pressure and below the pressure the cylinder is expected to fail. They are intended to protect from accidental over-filling and gas expansion in very hot conditions, like a fire or in a trunk (boot) parked in the desert.

Industrial cylinder valves with blowout discs look like this:

 

[PfcAJ]

I think burst disks are a vestige of when scuba tanks had tapered thread valves. O ring sealed valves aren’t the same and burst disks don’t make a lot of sense in them, imo.