Tech Diving and Air Integration

[mdwypro]

I dive with air integration on tech dives but not without a spg. I also use the same 6 inch hose to hook up my transmitter as on my deco tank. One reason is it is a little easier for me to glance at my wrist than pick up my spg especially with deco tanks. The other reason is I can download and track my sac rate accurately. I know we are told there is no benefit to have two spg on doubles and it is just another point of failure. I think with a spindle and a 6 inch hose it would be rare occurrence. I do not use air integration on deco tanks. My regs only have one high pressure port. Plus I think it would be in the way on your deco tanks. I also feel you do not have to monitor your deco tanks as closely as your back gas. At least in the type of bottom time I am putting in.
Recently on a shallow cave dive in Akumal, without my air integration, I saw my spg stuck on 2000 for about 7 minutes. I called the dive. On the way back the spg started dropping properly. With air integration I would have been able to verify my gauge. Also the small changes in consumption are sometimes seen more easily with an electronic reading.

 

[SOCAL_CELT]

I am really new to Tech Diving & as such I only have a rough estimate for my SAC rate, as I used an analog SPG to calculate it & as you know it's difficult to get an accurate reading this way.

Having read through this thread I am undecided on whether having an AI computer w/ sensor is a good idea for Tech diving in non-overhead environments, but I do know I need to start working out my own SAC rate & in order to do this I need AI, I will use this on rec dives & on Tech training dives before taking it on a real Tech dive (if I decide that's a good idea).

As I don't currently have AI even on my Rec gear I need to purchase this, is it possible to get a wrist mounted SPG with Air Sensor (i.e. not a computer but just SPG)? I am looking for a way to see a digital read out of my Air Pressure without spending the money on a 2nd rec computer...

 

[DevonDiver]

I do know I need to start working out my own SAC rate & in order to do this I need AI

I'd disagree with that assumption. On your tech course/s weren't you taught how to calculate your SAC (resting, normal and accelerated)?

Divers can get a bit obsessive over precision SAC... a figure that varies indeterminably any time conditions and circumstances alter. Have some broad strokes... and know the worst cases... and use improved situational awareness on your dives to increase familiarity with what your (analogue) SPG does..

 

[SOCAL_CELT]

I'd disagree with that assumption. On your tech course/s weren't you taught how to calculate your SAC (resting, normal and accelerated)?

Divers can get a bit obsessive over precision SAC... a figure that varies indeterminably any time conditions and circumstances alter. Have some broad strokes... and know the worst cases... and use improved situational awareness on your dives to increase familiarity with what your (analogue) SPG does..

We did run some numbers on the course (I just completed Tech 40 last weekend so I am very new to Tech diving!) for SAC rates, e.g. I calculated that during a 10 minute surface swim I used 100psi (on a small brass & glass SPG this is really hard to determine accurately & could have been anything from 50 to 200psi). I guess I just need to take readings over a much longer space of time, i.e. a 1 hour swim at the surface or similar at specific depths, no doubt this would be easier with AI but I take your point it is not necessary.

 

[DevonDiver]

It can take a while to get a good handle on your consumption - because it will vary. That variability means a lot... both for dive planning and where you have to crunch numbers in a lost gas scenario.

I dive metric, but I tend to add conservatism to the SAC by keeping things simple. If I dive double AL80s, I'll calculate consumption based on 2x10L capacity (they're actually 11.3L). My consumption is around 16L per minute, but I calculate at 20Lpm. 2000L @ 20Lpm x ATA... easy, especially under stress. That makes the maths very simple and provides a greater reserve.

From experience, my SAC can vary a lot depending on the individual dive; penetration vs no-penetration, current vs no-current, student buddies vs peer buddies, whether I take a crow-bar, a camera or just Mk1 eyeball.. 20L nicely covers all contingencies for a non-eventful dive.

 

[rjack321]

We did run some numbers on the course (I just completed Tech 40 last weekend so I am very new to Tech diving!) for SAC rates, e.g. I calculated that during a 10 minute surface swim I used 100psi (on a small brass & glass SPG this is really hard to determine accurately & could have been anything from 50 to 200psi). I guess I just need to take readings over a much longer space of time, i.e. a 1 hour swim at the surface or similar at specific depths, no doubt this would be easier with AI but I take your point it is not necessary.

Swimming on the surface is not really a great way to calculate this. Better is to just do a recreational dive in your deco diving gear confirguration to 100ft/30m for say 10mins. Figure your consumption during those 10mins at 4 ata and then have a benchmark for future planning. Typical planning SACs are often 0.5, 0.6 or 0.75 cfm depnding on the diver, water temp, experience, conditions, etc. I use 0.6 cfm for most dives, seem to be reasonable enough for me and on the conservative side. My actual consumption locally comes out around 0.45-0.5 cfm

 

[beaverdivers]

Another way to get your SAC would be to do the 100' dive for 10 mins. bottom time ( BT ), then slowly ascend doing a multi-level dive w/ a total BT of an hour.

Use an Air Integrated Dive Computer ( AIDC ). Then download your AIDC, it will show your average SAC. Also, it will show your SAC every 4 seconds during your dive.

We use this technique to analyze all of our students from their beginning pool sessions thru tech.

We use the Scubapro Galileo Sol hoseless AIDC with a heart rate monitor. It gives us the ability to show the students their SAC & workload based on respiration & heart rate.

 

[ajduplessis]

Using AI for tec dives is like blind dates without condoms. It's looking for trouble!!

 

[beaverdivers]

Using AI for tec dives is like blind dates without condoms. It's looking for trouble!!

That is why you always want to use at least two in both situations!