B2 breathes "funny"

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unwantedsn

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Here’s a fun one… I’ve got an Atomic B2 that sometimes breathes funny. It doesn’t do it on every dive, and it doesn’t do it at a certain depth or tank pressure. Sometimes it acts up at the start of the dive other times it’s mid dive or even when coming up the mooring line. It acts up at a constant depth or with depth changes.

What’s it doing? Well that’s hard to describe. If I sip the reg it breathes just fine. If I breathe hard from the reg its fine. If I take a medium breath from it, it will supply air, make a pop sound, air feels like it’s being interrupted, then give a brief rush of air and then go back to normal. What I’m not sure of is when it pops, and you feel the resistance, is if I’m thinking the rush of air that follows is more than normal, or if I’m assuming it is since it lacked pressure for that split second.

I’ve had 3 different techs look at the reg, none of them can duplicate the issue (like I mentioned it will be fine for 10+ dives, then randomly act up then be fine on the next dive). This all seems to have happened over the winter break, which would be from December to March. The 1st stage was overhauled last May of 2020 and a new piston was installed and it was environmentally sealed. They just overhauled the 2nd stage in attempts to fix this issues. They put in a new poppet, spring, and balance chamber. IP is good, cracking pressure is good, no IP creep. They are at a loss. What’s weird is I can be in the pool, get the reg to mess up, and then turn off the tank, depressurize / turn back on and it will be fine. I’ve attached a sound clip of it making the pop / crack sound. This is on the surface but it sounds same under water.

Does anyone have any ideas what this could be? The shop has pretty much determined that they don’t know what’s causing. The reg still “works” but it is a little unsettling that they can’t seem to figure out what’s wrong.

here is the audio file:
AA B2 breathe.m4a
 
Since they have hit the first place I would look(poppet, spring, chamber) I would ask them to next pull the orifice out and check the seat spring and shuttle piece (not sure of the name atomic uses but the nylon piece that lets the seat disengage) for damage, the shuttle can crack and cause odd issues.
 
Your B2 would like some more information about your statement that it breathes funny:

You mean, let me understand this … cuz I … maybe it's me, maybe I’m a little f***ed up maybe. I’m funny how? I mean funny, like I’m a clown? I amuse you? I make you laugh? I’m here to f***in’ amuse you? Whattya you mean funny? Funny how? How am I funny?

--Your Atomic B2
 
In an attempt to eliminate variables, have you changed out the LP hose and/or LP port you connect to on your first stage?
 
My 2 psi - First the suggestion above to is isolate it to the first or second stage. That is does your oct do the same?

If the second stage I would look at the AFC (automatic flow control). Why? when you sip it probably has little effect, when you breath hard it goes into full effect. But medium breath is just not enough to get it to kick in. My analogy is a faucet, turn it on low, water comes out slowly, turn it on full blast water blasts out, turn it on medium and the damn pipes chatter.

Also why the AFC, the chamber can accumulate sand and other material such that the diaphragm and plunger can become damaged/impaired. Also it is something that some tech do not take apart and inspect during service.
 
Since they have hit the first place I would look(poppet, spring, chamber) I would ask them to next pull the orifice out and check the seat spring and shuttle piece (not sure of the name atomic uses but the nylon piece that lets the seat disengage) for damage, the shuttle can crack and cause odd issues.

Thanks for the insight. I'll let them know to check that the next time I take it to them to have them look at it.

In an attempt to eliminate variables, have you changed out the LP hose and/or LP port you connect to on your first stage?

I haven't done that yet. The crappy thing is, since this doesn't do it on any dive, it will take some time to see if the port/hose is the actual issue, or if it's just not acting up.

I would change to a different second stage first. Is your octo an atomic too?

I'm going to take some flack for this on on SB, but I dive with an air2 (i'll go hide now). That being said, I could always see if I could get a rental from them and put the 2nd stage on there and see if it acts up.

My 2 psi - First the suggestion above to is isolate it to the first or second stage. That is does your oct do the same?

If the second stage I would look at the AFC (automatic flow control). Why? when you sip it probably has little effect, when you breath hard it goes into full effect. But medium breath is just not enough to get it to kick in. My analogy is a faucet, turn it on low, water comes out slowly, turn it on full blast water blasts out, turn it on medium and the damn pipes chatter.

Also why the AFC, the chamber can accumulate sand and other material such that the diaphragm and plunger can become damaged/impaired. Also it is something that some tech do not take apart and inspect during service.

I was thinking about the AFC, but they assured me that it couldn't be it. I'll try and get another atomic 2nd stage for an octo, and then maybe i can determine whether or not its the 1st or 2nd stage.
 
Your audio clip sounds like a second stage issue, not first.
I believe the issue is in the lever linkage.
If the back of the diaphragm disc is not scratched, have your tech replace the lever and the plastic fulcrum called the lever sleeve (PN 020004-00) that the lever pivots on, where it clips to the barrel. I don't think it's a poppet/shuttle issue.

Only other possibility is a diaphragm sticking issue. I'm trying to remember a recent thread here that discussed a very similar problem, and it turned out to be the diaphragm sticking to the faceplate. Seems unlikely with Atomic's design, but possible, I guess. EDIT: @halocline and @couv discussed it here:
Rough inhalation SP balanced/adjustable
 
If anyone would know its rsingler
 
Okay, I’ve never even seen this B2 regulator by Atomic. But I followed their website to their patent, and apparently there is a piston inside the second stage which automatically changes the Venturi vane depending upon the demand and depth. What I suppose, and take this with a grain of salt, is that something has happened to this mechanism to cause your regulator to behave as it does. It doesn’t affect the function of the regulator in providing air, but could simply be cause by something interferring with this piston’s functioning. Here’s the patent explanation:
Abstract
A second stage breathing regulator especially suited for use in scuba diving comprises an automatically adjustable air flow deflector or vane to redirect a portion of inlet high velocity air of a venturi-initiated vacuum assist-type regulator configuration. At greater depths the flow vane increasingly interrupts and redirects a selected portion of the air stream to increase the venturi effect. As a result, the diver's inhalation effort requirements can be relatively constant throughout the breathing cycle at any depth or can be tailored to a desired non-constant profile as a function of depth. A piston responsive to ambient water pressure by extension proportional to depth, places the flow vane to increasingly redirect the air flow at greater depths thereby increasing the venturi effect. The diver is thus freed of having to make manual adjustments to the second stage under water.

US5678541A - Breathing regulator apparatus having automatic flow control - Google Patents
Be sure to read the entire patent so as to understand this unique regulator’s Venturi function.

Good luck,

SeaRat
 
https://www.shearwater.com/products/perdix-ai/

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