What has changed since early 80’s?

[Sam Miller III]

K MAG YO YO

 

[rhwestfall]

modular/segmented learning, and no more militaristic torture...

 

[Angelo Farina]

We had safe seconds with NASDS in 1981.

True, I and my wife did buy our safe seconds in 1979, after a bad episode requiring "buddy breathing". But at the time the concept of Octopus was unknown or simply considered "not safe enough", so we got two complete regs, first and second stage, to be mounted on the second post of our Aralu twin tanks...
Here in Europe the Octopus did spread quickly only a few years later, associated with DIN valves, which make the risk of an O-ring failure extremely rare. Still today, I do not consider an Octopus a safe setup, if employed with a yoke reg...
I have seen too many O-ring failures at depth...

 

[tursiops]

I have seen too many O-ring failures at depth...

You have said this several times, and I still find it amazing. In all my dives, all over the world over many years, many of them with groups of recreational divers using yoke regs, I have never even seen ONE o-ring failure!
This is probably more indicative of the lack of value of such personal anecdotes, than anything useful about yoke regs or o-rings.

 

[Bigbella]

I've seen plenty of leaks from yokes -- furious cascades of bubbles, on occasion -- though, knock on wood, no outright failures at depth, since the late 1970s. I've also seen leaks with DiN systems, with similarly damaged or poorly seated o-rings.

All of the outright failures that I have ever witnessed, occurred upon that initial pressurization . . .

 

[tursiops]

All of the outright failures that I have ever witnessed, occurred upon that initial pressurization . . .

Agreed.

 

[Angelo Farina]

You have said this several times, and I still find it amazing. In all my dives, all over the world over many years, many of them with groups of recreational divers using yoke regs, I have never even seen ONE o-ring failure!
This is probably more indicative of the lack of value of such personal anecdotes, than anything useful about yoke regs or o-rings.

I think the cause was a systematic problem with the O-rings employed.
I did work 5 years as a professional instructor at Club Vacanze, and all the failures occurred during those 5 years.
Yes, most of them on the boat, when pressurizing the reg. But at least 5 times (over more than 100 O-ring failures) occurred after splash down: and at Maldives the technique was to go down immediately, so the O-ring failure did cause the immediate interruption of the dive for the whole group.
The cylinders were equipped with Cressi valves with double post and reserve. These valves used a slightly different O-ring than the Technisub valves, which at the time were the most employed here in Italy, thanks to their spring-loaded reserve, which you cannot pull by error before the reserve mechanism cuts air.
Almost everywhere the Technisub O-rings were available, but they did not fit well in the Cressi valves. Also customers did carry spare O-rings, often of the wrong size... By naked eye it was impossible to distinguish between the two O-rings...

 

[Scuba Lawyer]

The only tank valve yoke o-ring failure at depth I have ever experienced (or seen) was in about 1979 or 1980 at about 110' inside the cargo hold of a recently sunk (within 2 years or so) freighter in Curacao. It was a rental tank and I'm sure I never checked its o-ring before the dive. Fortunately, I had a 15 cu ft pony and that was ample to get me back up to the deco tanks hanging on the down-line at 10 or 20 feet (yeah, that's how we did deco dives back then. ). It was a really big BOOM and scared the [___________ insert body contents of your choice] out of me.

 

[tursiops]

I think the cause was a systematic problem with the O-rings employed.
I did work 5 years as a professional instructor at Club Vacanze, and all the failures occurred during those 5 years.
Yes, most of them on the boat, when pressurizing the reg. But at least 5 times (over more than 100 O-ring failures) occurred after splash down: and at Maldives the technique was to go down immediately, so the O-ring failure did cause the immediate interruption of the dive for the whole group.
The cylinders were equipped with Cressi valves with double post and reserve. These valves used a slightly different O-ring than the Technisub valves, which at the time were the most employed here in Italy, thanks to their spring-loaded reserve, which you cannot pull by error before the reserve mechanism cuts air.
Almost everywhere the Technisub O-rings were available, but they did not fit well in the Cressi valves. Also customers did carry spare O-rings, often of the wrong size... By naked eye it was impossible to distinguish between the two O-rings...

Well, this additional information is helpful, but now I'm not sure it is fair to call it an o-ring failure, or a yoke failure.

 

[Bob DBF]

cylinders were equipped with Cressi valves with double post and reserve. These valves used a slightly different O-ring than the Technisub valves...

I found a difference in o-ring size causing the same issue between normal US valve o-rings and the old Scubapro branded valves on the Scubapro branded MP Faber tanks. If the wrong o-ring pressurized, it worked on the dive fine, they just failed much more often. Once I started carrying the slightly larger o-rings for those valves I never had another one blow when pressurizing a reg. And yes, visually they looked the same.