PADI Deep Diver course- gas management

[tursiops]

I'm saying there could be an industry standard for calculating it, not for the answer to the calculation.

Why do you think that your calculation is NOT essentially the same as that being used within the industry? The only difference I can see is whether you use two divers or one, or a bit more than one if in a team of several, or extra challenging conditions causing quite variable safety factors....oh yeah, that's what I said originally. It depends on the dive. PADI says ascend with an appropriate reserve. So do you.

 

[lowwall]

Head up when first diver hits 800psi isn't good enough for ya'?

 

[divezonescuba]

This might help someone understand the different approaches.

 

[tursiops]

This might help someone understand the different approaches.

Remarkable how simple ideas can be presented so as to make them complicated.
Given this video, what do YOU teach for gas management on an NDL dive?

 

[MarkA]

Head up when first diver hits 800psi isn't good enough for ya'?

From 40m for 2 divers in an AL80? Possibly not.

But. This being a 40m course, maybe there is redundancy. Twinset or decent sized pony?

When I was doing 40m diving it was 100bar in 2x10l, but did include light deco on back gas. Interestingly this also meant being on the surface with 1/3 remaining.

 

[passeparici]

What we mostly do in France nowadays if we dive a bit deep (between 30 to 50 meters for instance) : we fix a TTS (time to surface) between buddies (for instance 13 minutes if we go to 40 meters so we know our deco time should be around 9 minutes if we go up at 10 meters per minutes), then if you use a 15 liters tank you multiply 13 X 3 (a sac rate of 20 liters per minutes is taken for this coefficient. I don't have the calculation with me be but this coefficient changes if you have a lower or higher sac rate but even if you have a lower sac rate it is safe to take 20 l/mn. It also changes if you have a different tank but 3 is good for a the configuration I gave). So 13 X 3 = 39 (we round it to 40). It will be the number of bars you will use on average to go from 40 meters to the surface with the deco time. You add that to the 50 bars reserve for safety and you know that you have enough for 2 persons to go up if 1 has a problem (40 is quite close to 50 in this case : you might add 10 for more safety). So at 13 TTS or 40+50+10=100 bars, whatever comes first for anyone, we go up. Obviously we communicate before we arrive at those numbers... If we use a pony for deco we don't take it into account for the calculation in case we can't use the pony for any reason

 

[chrisjur]

I recall that I was taught much more about gas management and various strategies/calculations in the PADI Self-Reliant Diver course than in the Deep specialty course.

 

[lowwall]

From 40m for 2 divers in an AL80? Possibly not.

But. This being a 40m course, maybe there is redundancy. Twinset or decent sized pony?

When I was doing 40m diving it was 100bar in 2x10l, but did include light deco on back gas. Interestingly this also meant being on the surface with 1/3 remaining.

The wink was because "leave the bottom at 800psi" is very common in DM briefings for warm water vacation diving.

Whether it would work for a deep class would depend on whether it was a multi-level dive. I would guess they usually are as doing a square profile to 40m is likely going to run you out of NDL time before you run out of gas.

 

[Centrals]

"Gas management" was never taught in PADI Deep Dive speciality course that I took in 1998.
PADI did not endorse "Tec dive" at that time.
First came across that in IANTD Advanced nitrox.

 

[tursiops]

"Gas management" was never taught in PADI Deep Dive speciality course that I took in 1998.

I can easily believe that you never learned anything about gas management in your Deep class in 1998.