Why not go to 100' ?

[CuzzA]

Non environmentally sealed reg? Icing?

 

[Eric T Lewis]

In short, 'feeling' narcosis is an absolutely unreliable method of gauging your true state of mental impairment.

That's pretty wild. I'm not going to argue with an eeg or the study, all I can say is it really felt like it was over. In dive school did a quick ten minute dive to 200'. Was narced out of my skull. Had a great time.
Two water stops before surface. Once on deck I felt perfectly normal. Not at all what I felt at 200'. If this study existed back then I would have tried some of those field sobriety tests. Maybe in the future I can try that.

 

[halocline]

Is there anything other than extreme abuse and neglect that would cause a complete HP seat failure?

A number of years ago scubapro had problems with the MK15 external IP adjustment, and the HP seat material. It occasionally resulted in the piston knife edge basically cutting the seat to shreds or getting imbedded in it. Either air flow was immediately stopped or there was nothing stopping tank pressure. They quickly recalled those regs and ditched the external IP adjustment.

The point is, while it's very rare for a reg to simply stop working, they are mechanical devices and can fail at any time. Anyone who dives in such a way that this would be life threatening is not a safe diver.

 

[halocline]

In dive school did a quick ten minute dive to 200'. Was narced out of my skull. Had a great time.

What dive school was that, and if you don't mind me asking? Did you use doubles, any stages, and did you have any deco training?

 

[Eric T Lewis]

Divers Institute Technology, Seattle, Washington. This is a commercial diving school. We learned deep heliox, surface decompression using o2 (surdo2. )
I was using a KIrby Morgan Superlight 17 surface supplied air.

I did many surdo2 dives in my commercial diving career. Offshore if we were going to 200' or deeper we used heliox. Not safe to perform construction while narced.

 

[mi000ke]

Great discussion and thanks to all for the advice. I tried to summarize the key points:

1. How conservative a diver you want to be? (or to quote that famous American: “You've gotta ask yourself one question: ‘Do I feel lucky?’ Well, do ya, punk?”)
2. Considerations: your skill level and experience, ease of dive, visibility, current, water temps, dive profile, number and skill level of other divers (My deep diving will be in the Grand Cayman with a well-regarded operator that I’ve used before in warm, high-visibility, low current water with a DM and maybe one or two other divers – if I don’t hire an instructor just for me, or do a course – on a wall with a profile descending to 100’ for 10 minutes, then ascend to top of wall at about 50-60’ with total dive time about 35 minutes, so not huge risk, but …)
3. Important deep dive skills to have and practice: air sharing, what to do if you exceed an NDL, free flow breathing, rectifying fixable equipment problems at depth
4. Need to know SAC rate and create appropriate dive plan with safety buffer (mine for the few relatively easy dives I measured it was about .45-.50. As I mentioned before, I’m a sax player and have been working on controlled breathing for many years and that’s helped with my SAC rate). Need to have enough cylinder air volume to cover an emergency contingency at depth (which in the discussion thread was recommended to be about 1000-1500 psi with an AL80 depending on one’s SAC rate)
5. Need to calibrate the narcosis effect under supervision
6. Need to check NDL frequently
7. CESA from depth is a very last resort (like one step short of drowning)

Recommendations

1. Get experience at greater depth under the care of an instructor who is specifically there for you, not with DM guide, or
2. Take the AOW course, or
3. Take rescue diver course

Based on the advice here, I am pretty sure I am going to do the AOW course when I visit Grand Cayman in October, which will give me the deep dive plus the instruction - or at least hire an instructor for a few deep dives. I have the good fortune of spending the winter months on GC starting this winter (going down in October to set up our digs), so will have lots of time in the future to work on deep diving. No need to rush it. Thanks again to all.

 

[antattack]

Nothing bad happened, just a stream of bubbles from the side of the regulator were the reg attached to the LP hose. I could still breathe the reg.

Yes, the O-ring was fine before the dive. It was fine at the surface. It was fine on descent. But it was pinched.

What I learned is that a small scuff on an O-ring gets worse as a stream of bubbles scrub the weak spot, making the damage worse quite quickly.

It was a bit of a problem for vision at when we called the dive, but by the time I was on the surface, it was a complete failure.

Did you check your O-gind before the dive? Walls it already damaged?

What exactly happened after the O ring burst?

 

[MXGratefulDiver]

One thing to be aware of is the Dunning-Kruger effect. It's worth 'Googling'....

Hmmm ... that peak on the left is what I used to call the "50-dive expert" ... because it seems common that at about 50 dives, people tend to start getting pretty confident with what they know without realizing how much there is yet to learn ...

... Bob (Grateful Diver)

 

[MXGratefulDiver]

I witnessed a high pressure hose that goes to SPG exploded on my dive buddy's reg, POW!, right after he opened the air valve, before we geared up for the dive.

I just had that happen to me at depth last month while diving the Thistlegorm in the Red Sea ... HP hose bubbled and burst right above the swage on the SPG end. But I was on sidemount at the time, so all I had to do was switch to the other tank and turn that one off. When I needed/wanted to use air out of that tank to add gas to my BCD I would open the valve, add gas, and close it again. For regular backmount rigs you wouldn't have that option unless you're carrying a redundant air source, and it's more difficult to manipulate the valve, but you can still orally inflate.

A failure of high pressure hose is a lot less catastrophic than the same type of failure in a low pressure hose. The size of the hole through the hose limits the amount of gas that will escape, and if you don't have the option of turning off your tank it buys you a lot more time to do an ascent to the surface.

... Bob (Grateful Diver)

 

[MXGratefulDiver]

So I'll preface this by saying I received the hose kinking tip from my instructor who is a full cave, CCR, tech instructor.

I tested it by hopping in my pool and while purging the reg I kinked my hose and it completely stopped the flow of gas.

Some clarification questions. What type of hose was it ... rubber or braided? Did you visibly damage the hose by kinking it? And if so (or even if not) did you consider replacing the hose after you kinked it?

I would think that such a demonstration would result in some question about the integrity of the hose, since they're not designed to be kinked like that.

... Bob (Grateful Diver)