YBOD first stages

dave t

Dont use an eviromental seal on the apex first stage, they cause the IP to creep up a bit with depth and it may interfere with your battery warnings or even stop the solenoid from firing. If you talk to AP they will tell you the same.

best

Dave

decoweenie

Why is that Dave ?

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jhaaja

Shouldn`t it be the same if water is directly pushing the diaphragm or the plastic piece inside the dry seal? Pressure is just pressure or am I missing something here?

The 1st stage is the same as the ones that are being supplied by AP now (US4). The difference is the turret and the dry seal that can be removed if I want (DST).

JH
Finland

dave t

As far as I understand it the IP does not stay at 8 bar (example) above ambient but creeps a little as depth increases this is due to the plastic disc that touches on the diafragm being too big and pressure increase is not linear, As far as I am aware apex Know about this and leave in as a "feature" cos on an OC reg it will make the second stage breathe better at depth. On the rebreather of course it will upset the needed IP and interfere with Batt warnings

best

Dave

jukkao

I have no shield against ice in either first stages in my Inspiration and no freezing experiences. Diving mostly in 1...4 C.

Is there anybody who has had some icing? Many friends here has a shielded diluent side.

Jukka

decoweenie

I didn't know this since all of my eCCR regs have been US-4 in the past. Thanks Dave!

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jradomski

the inspiration solenoid isn't as robust as something like a snaptite and isn't very good with higher IPs.. If you want to use a sealed reg, you really have to back the initial ip off a bit.. I use the same regs when using my HH or standard lid.. since the weaker of the 2 is the inspiration I set it to 7bar (normally I would set it to 7.5 bar), with this setting I havent has any problems as deep as 130m (insp head - have used HH head deepr without problems).. the one good thing about setting it a bit lower (regardless of if its sealed or not) is the po2 spikes past the setpoint (when deep) are a bit smaller. remember as IP pressure increases so does flow, and the inspiration doesnt change its firing length based on depth (where it should be getting shorter as you go deeper).

I use DST regs on my RBs because I have had my non sealed regs freeze on me in cold fresh water.. (never any problems in salt water)

BTW I have tested the snaptite solenoid and was able to fire it at 300 psi (~20 bar, its normal working pressure is 150psi) with only 4.2 volts driving it (below 4.2 it would not engage reliably) .. Kevin J told me he was able to fire it at 450 psi..

I have a chart somewhere on the amount the ip rises with pressure on the sealed units, its not that much over a non sealed regs (at least to reasonable depths)

The inspiration solenoids require a higher voltage and current to reliably engage..

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Joe Radomski
CCR Trimix Instructor Trainer
ANDI Instructor Trainer Director #10

All posts are personal opinions and DO NOT reflect any affiliated agency unless specifically stated.

jhaaja

Thanks everyone for the info.

I think I will leave the dry seal on and set the IP to 7bar.

I don`t think that the 1st stage will freeze even here in Finland under water but on the surface between 1st and 2nd dive during winter time.

JH
Finland

dave t

I set my IP at 7bar as well not because I use sealed regs but as Joe says it helps minimise overshoot, but dont set the IP too low. A while ago I experimented with very low IP's 3-4bar and it resulted in stuck open solenoids. I think not enough back pressure to close the solenoid under certain conditions!!!

Not sure I agree with the Snaptite being more robust to different IP's the tests I did on my HH showed the snaptite to be just as sensitve to battery duration verses IP as the inspo one

best

Dave

Doorduijn, Niels

JH,

If I may ask, why bother with the environmental seal at all? The volume of gas going through the first stages on both the diluent and the O2 site is very minimal, so I would think that the risk of the first stages free flowing due to freezing is minimal. Knock wood, but I only had a free flow on the unit once and that was when the bail-out regulator (Apeks TX 50 instead of the standard Air II) hit the water when jumping in mid winter. Since then, I put a gas flow stopper on the bail out regulator, hopefully avoiding free flows in the future.

So I guess I am wondering whether the risk of an increased IP pressure with a potentially failing solenoid outweights the benefits of the environmental seal. Mind you, I have consider putting environmental seals in the unit (the seals would in any event keep the first stages cleaner), but was told in no uncertain terms by APD not to do so for the reasons already outlined in various postings above.

I assume that the possibility of using a lower IP pressure in combination with seals has occured to APD but thay they rejected it as not the best option.

Rgs,

Niels