Recommended depths/times - Shutdowns!

[Mr_Brown]

i have been meaning to swap masks in the cold. will have to try it next time.
Thanks for the advice.

[Garf]

Originally Posted by neilh

That's always assuming that the rest of the team went in the same direction and the instructor didn't just sit at the same smegging depth being a smug git

(Ooops, ignore that last bit )

Paging Mr Walker. Will a Mr Rich Walker please attend this thread

[neilh]

Originally Posted by Garf

Paging Mr Walker. Will a Mr Rich Walker please attend this thread

I have a feeling he doesn't need any extra encouragement

[Johnny Boy]

6m for tdi adv nitrox/deco procs and iantd adv rec tx. i practise on every dive since at varying depths

[Garf]

We have done them at 1 metre depth in vobster, but that was just ridiculous as even the slightest change in breathing rate puts you on the surface. My recommendation is 6 metres. With regards to the speed, don't get hung up on this. Make the drill slow and smooth, and if you do it often enough, it will get quicker and quicker on its own accord.

[Rod Abbotson]

My recommendation is 6 metres. With regards to the speed, don't get hung up on this. Make the drill slow and smooth, and if you do it often enough, it will get quicker and quicker on its own accord.

Excellent advice - the speed will come and in a real emergenccy you will unlikely be running the whole drill just shutting down the problem. I personally find it easier when in a horizontal position which is of course better for of gassing.....

OK now as regards shallow practice and buoyancy etc try not to screw it up on required stops especially after a trimix dive...

Then again in real life you would be on your deco tanks and a low O2 backgas useless at shallower stops..

make sure you can do the full drill quickly at max depth were narcosis becomes a factor.

[Garf]

Originally Posted by Rod Abbotson

Then again in real life you would be on your deco tanks and a low O2 backgas useless at shallower stops..

:

unless you having a break from the O2 of course.

I would not recommend valve drills at the end of a dive. you have tired, cold hands, and you can't afford to fuck it up and end of the surface. Do them at the start of training dives. On real dives, I just do a flow check at the bottom of the shotline to ensure I havent rolled anything off on the way down. I take the same time to check my gas, calculate minimum and available gas, etc. This only takes maybe 30 seconds. Then, when we're all done, off we swim

[Rod Abbotson]

unless you having a break from the O2 of course.

I switch to a lower O2 deco gas for a break from high 02 when using hypoxic back gas. Saving the back gas for a reblend! Also use 80% max on deco allowing a greater margin for error and making little difference on deco time. (they actually do this in the hospitals now!)

[Mark Chase]

Originally Posted by Mr_Brown

I have been practicing shutdowns recently at the NDAC. Mostly doing them at 10-15m, after a 40 min dive in about 8 degrees, when your hands are starting to feel the cold, am now looking to increase the depth.

Is this advised when looking to do the TDI advanced Trimix... (what depth do they have you, do your shutdowns and within what timescales. 30 sec's 1 min? )

I suppose you should be compedent at doing them at any stage during the dive but just want to know what YOU all think.

Realistically you need to be shutting down or isolating in under five seconds.


Personally I went for isolation first and I only had the central isolator open two turns. I used a slob knob as manual shut downs were too slow. On average id have the isolator closed in close to two seconds.

Some schools of thought have the isolator fully open but they also tend to go for the primary reg post first rather than the isolator. Which is cool assuming the fault is on the primary reg and you can reach it OK.

I could reach back with my left hand better than my right, so I ran my main reg off the left post. Id isolate with two turns on the slob knob (using my right hand) then at the same time id reach back with my left to isolate the primary reg.

I have always found this very hard to do. So having isolated meant I at least saved half my gas. Primary reg shut downs some times didn't happen at all or took 10-20 seconds which is way too long.

Time how long it takes you to get to and shut down the primary reg. Then hit the purge button on your reg for the same period of time so as to see how much gas it would have cost you. Once you have that number you can plan your gas strategy accordingly.

ATB

Mark

[Timbobaggins]

Get a Rebreather, then you don't have to worry about all this cr****p