possible? 2nd stage failing & supplying air above ambient?

[knotical]

... search for that thread and we would all know the real truth.

http://www.scubaboard.com/forums/ad...nk-valve-feathering-modulation-technique.html

 

[fire_diver]

I think the reason was that this is not part of any current teachings. And hence deemed dangerous.

Just because it has been written out of the curriculum doesn't make it dangerous. Teaching people to scuba dive used to be about teaching how to deal with problems underwater and be totally comfortable with themselves and their gear. I say it's much more dangerous to be handing out C-cards to people who are still terrified of diving and unsure how to do anything but sit on the bottom of a pool and breath.

 

[EastEndDiver]

Just because it has been written out of the curriculum doesn't make it dangerous. Teaching people to scuba dive used to be about teaching how to deal with problems underwater and be totally comfortable with themselves and their gear. I say it's much more dangerous to be handing out C-cards to people who are still terrified of diving and unsure how to do anything but sit on the bottom of a pool and breath.

I couldn't agree more with this statement.Just look at how the "clearing mask" exercise has been dumbed down also I cringe when someone is certified who CAN'T swim.

 

[2cold4california]

Impossible because of the crimping effect of the connection points in the 2nd stage itself. The air would have to somehow pass through those restrictions into your mouth while maintaining a (dangerous) overpressure. The reasons for this are complicated but vortices are induced where airflow is constricted at each point where the LP valve, hose, demand valve and finally into the purge or mouthpiece.


So no it can't blow up in your mouth and a total failure would just result in freeflow.

 

[flots am]

Impossible because of the crimping effect of the connection points in the 2nd stage itself. The air would have to somehow pass through those restrictions into your mouth while maintaining a (dangerous) overpressure. The reasons for this are complicated but vortices are induced where airflow is constricted at each point where the LP valve, hose, demand valve and finally into the purge or mouthpiece.


So no it can't blow up in your mouth and a total failure would just result in freeflow.

I might just have my "stupid" hat on, but that made no sense to me. Could you try explaining that in English?

 

[2cold4california]

I might just have my "stupid" hat on, but that made no sense to me. Could you try explaining that in English?

What happens when you unscrew your tank valve when it's connected to nothing? The air doesn't just all come out at once. The air in the 1st stage goes from tank valve pressure (3000psi) to LP hose/ reg hose pressure (I believe 125psi?) then the demand valve releases at ambient pressure. Should the first stage fail, the hose will fail and then the demand valve will fail into freeflow. Same as it you took a tank underwater and opened it.

 

[Jim Lapenta]

Jibber jabber. My brain just went into shock. Enough of this. Time to eat.

 

[Rhyno]

Just because it has been written out of the curriculum doesn't make it dangerous. Teaching people to scuba dive used to be about teaching how to deal with problems underwater and be totally comfortable with themselves and their gear. I say it's much more dangerous to be handing out C-cards to people who are still terrified of diving and unsure how to do anything but sit on the bottom of a pool and breath.

Total agreement. I'd rather the scuba police come looking for me on the surface than search for me beneath it.
I did my OW roughly 2 years ago. At that point I believe the PADI coursework mentioned it, and it is something we tested in the pool. The big difference is that we were taught to breath directly from the tank, completely bypassing the 1st stage. You do this by placing your hand over the tank outlet and cracking the valve. You're to breath from this bubble "across" the flow of the air.

Where the previous link differs is they're wanting you to modulate the valve on the tank while still on your back through faulty equipment.
I don't know about you but I feel it's an extremely different scenario. I wouldn't want to attempt what that post was describing. At a very minimum get it off your back to allow you to safely modulate the valve.