Drysuit inflation with O2

Gilles

I thought this subject should have a dedicated thread.

I yet know nothing about DS diving, but I'll soon need to learn (heading to the colder climes of Northern Europe).

Quoting from jmurba "I want less gear, not more gear", I'm thinking through ways I can use a DS without a separate inflation bottle, reg, etc.

Use of offboard rich gas seems obvious, but I can imagine a number of scenarios where an offboard rich won't be needed, and all there is, is dil and offboard Tmx. It seems advantageous, and simple to utilize some O2 as an optional DS inflation gas.

What are people's and actual practitioners thoughts on this subject?

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Gilles
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Dsix36

In my learning curve there were several connections and different gases used.

I tried onboard dil but don't like to waste my dil on suit inflation. I have plumbed to offboard BO tanks and this works fine with the exception of what gas is in the tank. I now use a seperate 6cf suit inflation bottle (filled with air) mounted to my wing and have LP hoses on all BO tanks for emergencies.

I have inflated with air, 32%, 50%, 80%, 100%, and 21/35. The only difference that I can feel in the warmth difference is that the 21/35 is just a little tiny bit cooler if hanging for a long deco.

I am new to drysuits also. This may not be the best advice, but it is what seems best for me.

More info here:
http://www.rebreatherworld.com/rebre...tor-hoses.html

http://www.rebreatherworld.com/gener...iving-dry.html

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Long debate here

My opinion is thats interesting to know that its possible if you have to choose between trimix and o2 as backup solution on a long deco ( without electric heater in your drysuit )

jradomski

I always use a seperate DS inflation system.. its usually a 6cuft bottle thats not even noticable, but on deeper dives I'll use a 13 cuft bottle..

I rather not waste bailout gas, its there for a reason, and on deep dives between filling the loop, wing a DS there probably is not enough gas on the onboard diluent cylinder..

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nigelh

100% in a drysuit sounds unhealthy unless you O2 clean the occupant.

I don't want more gear or less gear I want safer gear. The most significant thing I take diving is me and so I will use the kit that ensures that I bring me back every time.

Hence for a dry suit it is a separate inflate tank. Green thing behind my left shoulder in the avatar. It is nice and simple and it means that I have a buoyancy system that is totally independent of my other breathing gas systems. I normally dive with buoyancy control on the wing but I can do it on the suit so if something goes wrong with my DIL, into which the wing is plumbed, I can carry on holding my profile while I fix it. I have only had to do this once so far but when the AutoAir free flowed (grit) I just shut off the DIL.

In the winter I stuff Argon in it. Yes, I know it isn't much better and when tested on fit young navy divers didn't make a difference to their body temperature but I'm talking about an old man's comfort here. After 2 hours in the water and discovering it's snowing when I surface I do feel noticeably better on Argon.

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nigelh

lizardland

I worked on the design of some hyperbaric facilities years ago, IIRC the breakpoint for designing hyperbaric habitats is any atmosphere containing 23% or more O2 should be treated as an O2 habitat for fire risk. And combustion is based on %O2, not PO2. Now that contradicts what most of the recreational (i.e. not commercial) diving agencies teach whcih is generally 40%+. However, chamber fires are invariably fatal so the risk is far more onerous. I've used bailout gases for drysuit inflation up to EAN50, but that's where I'd draw the line, I would never consider O2 as an inflation gas unless it was an emergency like having to pass a sump -- I remember one in particular where the breeze block walls were charred to about 2" deep. I've seen the aftermath of industrial O2 accidents so maybe I'm just paranoid. I've tried suit inflation using 18/40 and I was freezing in 15degC water after only 40min (i.e. shivering).

Using bailout gas for inflation isn't a major problem. I run my wing and BOV from my deep bailout, allow a few bar for it and plan your bailout gas accordingly. A couple of dives is enough to get a feel for how much you need. Downside is that you end up having to top up deep bailout cylinders every now and again. For open water diving, I've got a 0.4l suit inflation bottle which has been fine for square profile dives to 70m, don't think I'd like to rely on it any deeper.

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EBT

Its never black and white in the real world. My personal grey area is to use a suit bottle if theres enough room in what Im diving to squeeze through with it.

I dont like driving off O2 since thats my breathing gas and Im not a fun of adding more demand on it, or more connections to it.

Bailout gas is out too, since I like my bailouts to be full when I goto them... and I also like not having to reblend them etc to keep them at full pressure (and Im tight, air in the suit bottle costs bugger all).

In the real world though I've used a bailout bottle to drive the drysuit in a tight cave.

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Hanssing

Well I'm still app. 9hrs away from my gentelmans-agreement of modifying the rEvo, so I'm only talking abou planned modifications below.
The thing is I allways dive in a drysuit, and I dive a lot of dives real shallow. The remainder is for the most part within Mod1 ranges, and the future dives withing mod2.

So how to avoid to much clutter while diving real shallow or with only one BO-tank (7l. EAN32) or perhaps two (7l. Trimix + 7l.EAN50).

It then becomes mission specific, and within those parameters I am still planning for the following:

• Wing is never used during dive, but if needed is drivin from onboard O2, with a POS regulator/inflator wich also gives OC access to OC if needed. The inflator-combo is placed on right-hand side, and also acts as OPV.
• Drysuit is allways driven form Onboard, with either Air or EAN50'ish.
• BOV, ADV and MAV is driven form either onboard-Dil or offboard-Dil, but they allways see same gas-source.

The system has the following dis/advantages:

• + OC access to all gas onboard and offboard.
• + NOrmal Mod1-dives runs from onboard sources only, so I only have to top onbaord air and O2. BO-stage is practically untouched. Today I run drysuit from BO-stage, Dil/Wing form onboard, and then O2 form onboard. I allways have to top 3 bottles.
• + Keeps totally redundant boyancy-supply for Wing/Drysiut.
• + Drysuit is driven by Air (EAN32 today - wastefull).
• + No reconfiguring needed if bailing out.
• + Shallow dives wihtout bailout possible.
• + Using the same QCs means you have some options shoudl a reg fail to deliver the gas needed - but only needed if a reg fails during normal deployment of the BO-system.
• - Added failurepoints in added hoses.
• - Possible to grab O2-reg at depth. Though bloody unlikely and then you should not dive RBs....
• - Possible to f**k up selected diluent, but then you should not be diving with multiple diluents, or offboard connectors anyway.
• - Adds a reg to O2-side, but since I dive rEvo, the chance of freeflow DECREASES with depth, since its constant absolute pressure. If it does freeflow, disconnect it.

For further info you could see Dave S ramblings in the rEvo-forum, its practically an exact copy of his system, but it is usable on most CCRs.
Again it is specific for Drysuit dives in MOD2 ranges and less. My 2x3lx300bar onboard is still a significant amount of gas if bailing. I dont plan with them included, but want access should I bail for real. When working with a single BO-cylinder with a lowish EAN-mix the pure O2 will help on that last deco-stop....

Nicolai - not yet modifying anything.

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OceanOpportunity

I use 2 approaches:

1. for 'easy dives' with just onboard O2 & dil, I run dil as my primary means of inlfation. This means to my drysuit if diving dry, or my wing/BC if diving wet. O2 would feed a 2ndary means of inflation. This would be my wing if diving dry.

2. for 'more complex dives', in general I like to consider the rebreather as a stand alone unit. It lets me recycle breathing gas. period. And the onboard gasses are well matched to meet mission specific reqs. In this case, I could seperate entirely from the rig and still have a means to make it home. this effectively means a seperate inflation bottle feeding my suit and wing, and my offboard bottles are equipped 2nd stages and with inflator whips (CEJN fittings) to match up with my BOV or suit (also has CEJN nipple) in a pinch.

Generally speaking, I'd save the O2 altogether for rebreathing or your precious OC shallow deco gas if shit hit the fan. BUT, I see no problem with running it through to your suit or wing. Most issues with O2 handling are with HP systems...one its in your bottle and regulated through your 1st stage your fine. I work as a commercial diver, and once you see a Broco torch blowing O2 in and near water saturated with various hydrocarbons, you won't sweat the little rubber o-rings in your suit and throughout your rig.

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