Plastic second stage failures

[KeithG]

I was unclear - i was referring to tighthening the host mount onto the housing. Since it is a sealing surface and has an o ring, removal and replacement of the metal hose mount will be part of normal service.

And to clarify - i am using the term "hose mount" when maybe I should be using "orifice" as per AMS511 post above?

 

[ams511]

And to clarify - i am using the term "hose mount" when maybe I should be using "orifice" as per AMS511 post above?

I believe AL / USD calls it an inlet fitting. I looked at the schematic of the Conshelf XIV, it appears to be identical to the SE-2 diagram. I suspect that A.L. just changed the case from metal to plastic and did not redesign the components. I looked at the schematic for a newer model Titan and it is redesigned so it should not become separated.

 

[ScubaSteve85]

There is an interesting article in the Spring 2017 issue of Alert Diver Magazine: A Free-Flowing Failure

The plastic housing of the second stage failed and caused a freeflow. It isn't clear to me if the plastic housing was exposed to full IP pressure or not. Does anyone know what regulator this is?

Here is a related article that shows how long it takes for various failures to empty a single 80 that appeared in Advanced Diver Magazine:
Life Ending Seconds, 3000 to Zero in 72 Seconds

View attachment 417605

Those numbers for burst disc failure are terrifying. I know they're supposed to be replaced at a certain service interval, but the idea that one could prematurely fail and empty a tank in a minute is enough to make me always want a completely redundant backup.

 

[halocline]

It's extremely unlikely that a burst disc would fail at depth. It's much more likely (still VERY rare) that it would fail either during filling, or when the tank is completely filled and hot.