737 destroyed by O2 explosion

[rsingler]

The needle valve opens all the way with no flow restriction. And yes, I believe that it has a finer thread pitch like the DGX valve. More to follow on that when mine arrives.
With a needle valve, even assuming the same thread pitch as the DGX, the curve of the pressure rise will be much different due to the increasing area for gas delivery as the needle retracts. In contrast, a flat face valve gets to max area much more quickly.
I'm not sure that there's an advantage to taking 2 minutes to full pressure, compared with 20 sec. What's important to me is the initial slope of the curve in limiting adiabatic heating, since not much volume is moving. Same principle with regard to impact ignition.

But this isn't a huge deal, given the rarity of the problem. IF you're careful to just barely crack any oxygen valve, and just wait, you're probably half way to what AP has done. IF you are meticulous about keeping your gear oxygen clean, you're gonna be fine. Probably. Still, for me, amortizing an extra $70 over five years of diving with a $2k-$8k CCR is smart money. That example above - I'll bet that even if he could have gotten to it quickly, the guy might really have hesitated before throwing his burning expensive toy over the side. As it was, a lot more was lost than a $2k breather, when that boat went up.

 

[stuartv]

The needle valve opens all the way with no flow restriction. And yes, I believe that it has a finer thread pitch like the DGX valve. More to follow on that when mine arrives.
With a needle valve, even assuming the same thread pitch as the DGX, the curve of the pressure rise will be much different due to the increasing area for gas delivery as the needle retracts. In contrast, a flat face valve gets to max area much more quickly.
I'm not sure that there's an advantage to taking 2 minute to full pressure, compared with 20 sec. What's important to me is the initial slope of the curve in limiting adiabatic heating, since not much volume is moving. Same principle with regard to impact ignition.

But this isn't a huge deal, given the rarity of the problem. IF you're careful to just barely crack any oxygen valve, and just wait, you're probably half way to what AP has done. IF you are meticulous about keeping your gear oxygen clean, you're gonna be fine. Probably. Still, for me, amortizing an extra $70 over five years of diving with a $2k-$8k CCR is smart money. That example above - I'll bet that even if he could have gotten to it quickly, the guy might really have hesitated before throwing his expensive toy over the side. As it was, a lot more was lost than a $2k breather.

I will wait to purchase any new valves until you report back on the AP valve.

My problem is that some (all?) of my O2 cylinder valves have a VERY narrow window of going from 0 to full pressure in the line. I am pretty darn good about remembering to attempt to open slowly. But, even when I really try, it seems like my gauge goes from 0 to full pressure in about 1 second. If the DGX valve "fixed" that, it would be worth it (to me) to upgrade.

If the AP valves have the needle AND finer threads to slow down the opening, that might be worth the even greater expense. But, if they go to fully open in the same number of turns that a "normal" valve does, I'm not sure they would be worth it (to me).

I am more concerned about forgetting and turning the handwheel quickly than I am about exactly how it behaves when I remember to do it slowly. When I remember to do it slowly, I am *probably* okay no matter which valve I have.

 

[rsingler]

My new valves and some extra service kits are on the way. I'll take one apart and post what I find.

I am more concerned about forgetting and turning the handwheel quickly than I am about exactly how it behaves when I remember to do it slowly. When I remember to do it slowly, I am *probably* okay no matter which valve I have.

Yep! This.

 

[jadairiii]

I remember that picture of the club dive boat that Phi Le was on and posted the writeup of the accident on The Deco Stop.
Phi was a cave buddy of mine back when we were members of Odin Tech Divers around 2000.

Michael

Wow, that is a name from the past! My dive buddy trained Phi on the original Halcyon SCR (late 90's?) and I had the opportunity to dive with him a few times.

 

[rsingler]

While we're waiting to see what the AP valve brings to the plate, here is the DGX O2 valve thread on the top, and standard thread on the bottom.
It takes 3 3/4 full turns to fully open/close the DGX O2 valve, while only ~2 full turns for a standard DGX valve.

 

[michael-fisch]

Wow, that is a name from the past! My dive buddy trained Phi on the original Halcyon SCR (late 90's?) and I had the opportunity to dive with him a few times.

That must have been the fridge, since Buchaly let Halcyon copy the RB2000 renamed as the RB80 around 2001. The first few RB2000s were made by Klaus Reizig for Buchaly around 2000.

Michael

 

[abnfrog]

@rslingler I agree im not sure 13 seconds vrs 2 min, but im in for paying out 70 per valve if it stops a potential fire , its cheap at twice that cost , I try of stress to my students on the blender courses how really deadly o2 can be and not to get complacent with it when you get your valves im in for some

 

[2airishuman]

Why not just create some kind of adapter and use regular medical o2 valves?

Or CGA540, which is physically stronger than medical post.

I think it's crazy that we use the same valves for O2 and air. I understand the history. Understand that there are rich mixes that aren't 100% that have to be taken into consideration. Understand that there are procedures that are widely believed to provide equivalent safety. Understand that there aren't readily available regs and valves in CGA540 that are suitable for diving.

All solvable problems and lives would be saved.

 

[stuartv]

@rslingler I agree im not sure 13 seconds vrs 2 min, but im in for paying out 70 per valve if it stops a potential fire , its cheap at twice that cost , I try of stress to my students on the blender courses how really deadly o2 can be and not to get complacent with it when you get your valves im in for some

But, they're $150 per valve (from SilentDiving.com). I hope we end up getting a much better deal via @rsingler. But, I will be pretty dang shocked if he is able to offer them to us for anywhere near $70 each.

 

[grf88]

I think the $70 refers to these:
DGX Premium O2 Pro Valve, Right (Typical Side) | Dive Gear Express®