Where should I start to approach the rebreather world

[BlueTrin]

OC prep is two discrete phases, days apart. First is to get the gas fills: driving to the gas shop and waiting. Half a day! The build takes minutes in the boot/trunk of the car.

Oh the misery of the wrong gas for a change of plans.


On CCR the gas mixing and top up is done in my garage using three twinsets of air, oxygen and 10/75. I’ve a couple of sets of 3litre tins. From those banks I can mix pretty much any gas.

As that mixing is simple, it’s left to the night before when I know the dive profile. The CCR build still needs an hour in case of problems.

Do you have use a compressor at home to do the mixing from the banks?

 

[Tassi Devil Diver]

I wish people would just be honest about the time it takes to prep a rebreather. There is no way you are filling both scrubbers, analyzing all your gases, checking your batteries, flow check on your MAV if a mCCR, doing a stereo check, build, positive-negative, calibrate etc in 30mins on any CCR. A full 5mins each at positive and negative alone are minimum 10mins

I stand by the fact it takes me nowhere near two hours to prep my rEvo before a dive, 30min could be as long as 45. I like to be organised, my 3L bottles bailouts are all prepped and filled well before (I have my own fill station I have premixed in old twin sets 18/45, 14/60 and 10/70 and 4 sets if dill cylinders 3 sets of oxygen cylinders), I am not filling sorb canisters I grab a set of canisters with a level of use appropriate for the dive (I have four sets, at anyone time two have a level of use two are fresh), I am not on the night before a dive filling cylinders, filling scrubber canisters, occasionally if I am caught out I might need to fill a canister and that takes minutes. I build the unit and run through the build check that takes 30 min 45 at the most, it might take longer if I run into issues. I often do a partial build once everything has dried out mid week put the loop together and internals, that is when dump and fill any sorb canisters if I need to and top up dil oxygen etc if needed.

There are other things I need to do of course like get the scooter ready, get other gear together, build and prep my camera.

Clearly we all have own systems but I am not spending two hours or anywhere near that putting my unit together the night before a dive which was the nature of the question.

 

[Wibble]

Do you have use a compressor at home to do the mixing from the banks?

No compressor nor booster. I get the 2x12 litre twinsets cave filled, circa 270 bar. Am happy to dive with 160 bar in the CCR 3 litre tins — ok, not for really big dives. A dive tends to use about 60 bar, so loads left on surfacing.

From this I can pretty much mix for any MOD2 dive, probably 10 days or more of dives before needing the banks topping off. Isolators are closed, so cascading to keep the pressures up.


Regarding prep time, I’d be nervous about allowing less than two hours even though it’ll take less than that.

 

[PfcAJ]

OC prep is two discrete phases, days apart. First is to get the gas fills: driving to the gas shop and waiting. Half a day! The build takes minutes in the boot/trunk of the car.

Oh the misery of the wrong gas for a change of plans.


On CCR the gas mixing and top up is done in my garage using three twinsets of air, oxygen and 10/75. I’ve a couple of sets of 3litre tins. From those banks I can mix pretty much any gas.

As that mixing is simple, it’s left to the night before when I know the dive profile. The CCR build still needs an hour in case of problems.

Aight oc isn’t that big of a deal. Anyone doin any trimix diving with any frequency has a few sets of doubles and stages.

Also, let’s not act like mixing trimix is some voodoo. Most places that can support trimix bank Nitrox. Put in helium, top with nitrox 32. Super easy to make the GUE standard gases this way. Spots with good volume of trimix divers pre-mix the usual gases.

And how much misery really is there for a change of plans? Standard gases are at a 50’ interval, and you don’t have to go to the bottom of a wreck if you end up on something a little deeper.

 

[Wibble]

Aight oc isn’t that big of a deal. Anyone doin any trimix diving with any frequency has a few sets of doubles and stages.

Also, let’s not act like mixing trimix is some voodoo. Most places that can support trimix bank Nitrox. Put in helium, top with nitrox 32. Super easy to make the GUE standard gases this way. Spots with good volume of trimix divers pre-mix the usual gases.

And how much misery really is there for a change of plans? Standard gases are at a 50’ interval, and you don’t have to go to the bottom of a wreck if you end up on something a little deeper.

Gassed up for a 50m/165' dive, weather changes it to a 30m/100' dive. NP on CCR. Damn expensive for OC

Nothing hard about mixing trimix provided you have the helium.

Have never seen standard mixes banked for OC, it’s generally mixed to order. You need a booster to get decent pressures and you’ll still be constantly mixing top-offs for the banks, especially if doing OC fills. Obviously with the smaller cylinders and low gas usage on CCR, banking is so much more practical.

When mixing trimix, the oxygen content is generally critical but the helium content is approximate; nobody cares if you’ve ordered 35% He and you get 30% or 40% (and pay accordingly!).

 

[wetb4igetinthewater]

I wish people would just be honest about the time it takes to prep a rebreather. There is no way you are filling both scrubbers, analyzing all your gases, checking your batteries, flow check on your MAV if a mCCR, doing a stereo check, build, positive-negative, calibrate etc in 30mins on any CCR. A full 5mins each at positive and negative alone are minimum 10mins

If you have a bunch of stuff done ahead of time or you skip steps, then sure you can get it down to under an hour. But from scratch let's not mislead people. 60mins is fast, 90mins is normal, 2 hours isnt anything to be ashamed of.

I'm at 2 hours plus, as I recheck everything at least through my head (i.e., I don't calibrate my sensors mulitple times, that'd be stupid). Probably not necessary, but I want to memorize things despite the fact that I will ALWAYS use a checklist.

 

[Wibble]

The head to toe check. The imaginary laser line from head down: hood, mask, regs, computers…

Always before driving off

 

[PfcAJ]

Gassed up for a 50m/165' dive, weather changes it to a 30m/100' dive. NP on CCR. Damn expensive for OC

Nothing hard about mixing trimix provided you have the helium.

Have never seen standard mixes banked for OC, it’s generally mixed to order. You need a booster to get decent pressures and you’ll still be constantly mixing top-offs for the banks, especially if doing OC fills. Obviously with the smaller cylinders and low gas usage on CCR, banking is so much more practical.

When mixing trimix, the oxygen content is generally critical but the helium content is approximate; nobody cares if you’ve ordered 35% He and you get 30% or 40% (and pay accordingly!).

100’? Lol grab a single tank and enjoy your day. Also, you can check the weather before showing up

I can think of 3 shops in north Florida that bank mix, and at least 2 in south Florida. There’s for sure more. Heck, I know dudes with garage fill stations that have banks. It’s really not a big deal.

 

[tbone1004]

100’? Lol grab a single tank and enjoy your day. Also, you can check the weather before showing up

I can think of 3 shops in north Florida that bank mix, and at least 2 in south Florida. There’s for sure more. Heck, I know dudes with garage fill stations that have banks. It’s really not a big deal.

I can't think of 3 that bank trimix anymore, but my garage has 10/70 and 18/45 banked along with a bunch of 32% :-D
Not terribly common to bank trimix, but not difficult to get it though since basically everyone in cave country has a booster

 

[KenGordon]

I have done a pool dive with an AP CCR but it was only a 1m deep pool at a dive show so you couldn’t get a feeling of how CCR works with buoyancy and the unit was already assembled.

I’ll look into this, thanks. Would be useful to do the prep so I know what I am getting into before to pay anything.

You can see Friday evening or Saturday afternoon depending on how long we spend under the pier on Friday. On just a random day at Wraysbury or following a Brighton trip.