Regulators with Flow Adjustable Knobs

[docmartin]

they also tell you to store the reg with the knob all the way out ie soak with knob all the way in, store with knob all the way out. definitely no seat saver feature.

Apeks seconds do not have a seat saver feature.

 

[LeadTurn_SD]

..... Is there "a right way" to reduce SAC? .

Bob DBF knows the answer and his question was rhetorical, and this reply is tongue-in-cheek, but yes there is a "right way" to reduce SAC.

1. Dive more.
2. Relax and breath.
3. Go slowly, it is not a race underwater. Don't flap your arms.
4. Don't worry about your SAC, it will improve.
5. Repeat.

That is actually serious advice.

Best wishes.

 

[Bob DBF]

Bob DBF knows the answer and his question was rhetorical, and this reply is tongue-in-cheek, but yes there is a "right way" to reduce SAC.

1. Dive more.
2. Relax and breath.
3. Go slowly, it is not a race underwater. Don't flap your arms.
4. Don't worry about your SAC, it will improve.
5. Repeat.

That is actually serious advice.

Best wishes.

Of course you are right, but I knew some oldtimers that would detune their new regs because they would use too much air if the reg breathed easier than their old regs. I think that the easier breathing resistance just upset their breathing pattern, using more air.

SAC is dependent on your body, your mental attitude (relax), and how much work you do underwater. If I am going to move around a lot or work, I just grab a bigger tank, it's all about planning. SAC is a tool not a Quest.




Bob
------------------------------------------------------
"This is scuba board, where problems are imagined or overstated......and chests get thumped about what some would do about those "problems" "- PullMyFinger

 

[WrmBluH2O]

Scubatoys wrote, "...that regulators are designed to breathe as easily as possible at all times regardless of what depth." That makes perfect sense to me.

I'm a newbie. My dumb question is that if the rapid adjustment knob on an Atomic ST1 had been turned wholly inward would one even perceive a difference at a depth of only 50-60 feet? I know the ST1 is an awesome, easy breathing regulator.

On one of my first few OW cert dives, somewhere between 50-60 ft, I felt a subtle change as though I were sucking through a straw. (I do not have asthma.) I chalked it up to likely a bit of anxiety. It resolved at shallower depths. The next two times at 50-60 ft again that sucking through a straw feeling. (Minimal current, great visibility, going very slow, Caribbean wall dives for all three.)

So, is it possible that more effort for inhalation could be required at the relatively shallow depths of 50-60 ft due to a fully inward adjusted knob, or is this much more likely to have been a psychological issue?

I look forward to getting back in the water, adjusting the knob outward, and leaving it alone (unless I encounter current or a free flow sitch.) I am simply curious...

Thanks!

 

[scubatoys]

This is a post listed directly on Atomic Aquatics webpage that pretty much sums the efforts at top and the bottom. "All Atomic regulators breathe with a natural and controlled air delivery sensation at any depth or breathing rate. Inhalation on the surface will feel the same as it does during your deepest dive. This is in part due to the AFC (Automatic Flow Control) employed in our second stages. This patented innovation is a simple device that adjusts the airflow automatically to compensate for the effects of depth." From my knowledge of the Atomic regulators if you adjust the knob inwards you are cutting down on the supply of air therefore increasing breathing effort but the difference in effort at depth versus close to the surface should not change. The air is more dense at depths but at those depths it really isn't too much at 50-60 ft and I wouldn't think it would be that noticeable. Do you know how long it has been since its last service interval? Sometimes you can notice increase of effort in inhalation when the spring in the 2nd stage starts to gather builds up on it if the regulator hasn't been serviced in a while or if it has been dove in an excessive amount outside the recommended amount of dives between service intervals. Of course this would need to be a lot of dives as they recommend 2 years or 300 dives which ever comes first.

 

[The Chairman]

All the adjusting knobs on all the regs I have serviced increase the cracking pressure of the second stage. Any flow restriction is secondary, but it can be substanstial. Some regs more than others.

It's all about comfort. Set it so that you are most comfortable for you during the dive. I usually set my necklaced reg at the max and the one I'm breathing off at the easyest setting that stops any bubbling.

 

[WrmBluH2O]

...Inhalation on the surface will feel the same as it does during your deepest dive. This is in part due to the AFC (Automatic Flow Control) employed in our second stages. This patented innovation is a simple device that adjusts the airflow automatically to compensate for the effects of depth."

Yes, I had previously read this which had me leaning toward the issue is with me not the gear.

From my knowledge of the Atomic regulators if you adjust the knob inwards you are cutting down on the supply of air therefore increasing breathing effort but the difference in effort at depth versus close to the surface should not change. The air is more dense at depths but at those depths it really isn't too much at 50-60 ft and I wouldn't think it would be that noticeable.

I tend to be hyper-aware of bodily sensations, but I'm grateful to hear you feel it wouldn't be noticeable. Again, that would make me think anxiety...

Do you know how long it has been since its last service interval?

The ST1 I had been using was brand spankin' new.

I really appreciate you taking the time to chime in, thank you. It was a subtle change but was there. Had me wondering if that sensation was "normal". But, my husband also uses the ST1 and said he doesn't experience what I did.

 

[WrmBluH2O]

All the adjusting knobs on all the regs I have serviced increase the cracking pressure of the second stage. Any flow restriction is secondary, but it can be substanstial. Some regs more than others...

NetDoc,

Thank you for giving input especially as you've serviced regs. So...are you saying there is a chance (however small) that it could be a flow restriction I could feel?

I get your larger point about setting it where it's most comfortable. If it can actually be perceived, I'd be tempted to set the octo at the easiest setting (that doesn't allow bubbling) as well. For my buddy's benefit and for me. People seem to go both ways on that one, don't they?

Of course it was likely distressingly loud coral that set off these anxiety spirals for moi...

 

[The Chairman]

I leave the octo (necklaced) reg cranked down unless I go for it. Then, I make it easy to breathe for me.

Most regs have a cracking pressure of about 1.5" of water. That means, if you put a dry reg face down into the water, the inch or 1.5 inch distance between the diaphragm and the mouthpiece shouldn't cause a free flow. Push it down a bit too fast, the resultant pressure with the added venturi effect through the mouthpiece and the resulting free flow can be almost distressing as the "not so silent world" we dive in on the reef.

Work of breathing is a combination of many factors. The lever arm, the size of the diaphragm, how the two interface, the IP (intermediate pressure), the pressure of the spring on the seat, the strength of the spring causing that pressure, the various venturis in the system, back pressure from the escaping gas and I'm sure I've missed a few. If any of these are out of range, even a tiny bit, it can really affect how easy/hard a reg is to breathe. It's easy to tilt the system so that you feel air is being rammed down your throat at the slightest provocation or that it takes considerable effort to get any air out. Compounding this, is a second stage's ability to handle an attitude change. Flip on your back some time and see how your reg breathes.

Here's the kicker: what's good for you may be horrible for me. It's my opinion that there are no really crappy regs being produced anymore. There are certainly differences in strategies, materials and breathing characteristics, but there is no one reg that will please every one. My favorite reg is the one I am breathing on. I have a high tolerance to variance in breathing characteristics. Sure, I've breathed on a buddy's reg and had to wonder how they can survive on such a crappy reg, but for the most part I simply breathe in, then out and repeat. I'll play with the screw a bit and bring it out to where it just bubbles and then screw it back an eighth of a turn or so, but I think that's more habit than anything.

To answer your question (finally, right?), cracking pressure has probably more effect on work of breathing than anything else. You have to work harder for the same air.

 

[halocline]

On one of my first few OW cert dives, somewhere between 50-60 ft, I felt a subtle change as though I were sucking through a straw. (I do not have asthma.) I chalked it up to likely a bit of anxiety. It resolved at shallower depths. The next two times at 50-60 ft again that sucking through a straw feeling. (Minimal current, great visibility, going very slow, Caribbean wall dives for all three.)

Thanks!

Second stages perform pretty much the same regardless of depth, although there are some caveats. If you feel increased inhalation effort at depth, it's due to the increased workload on the first stage. In your case, if you had a very high quality first stage (like an atomic) and you really did experience increased WOB at 50-60 feet, it means something was wrong with either the 1st stage or the tank valve. Maybe a restriction in the filter or the tank valve was only partially open, could be any number of things.

More likely what you experienced was psychological, considering it was one of your first dives. But occasionally tank valves do get clogged or left mostly shut by well meaning DMs. That will definitely cause increased breathing effort at depth.

The reason 2nd stages function more-or-less the same at all depths is because the 1st stage compensates for depth by increasing the air pressure to the 2nd stage at the same rate ambient pressure increases at depth. Thus, 2nd stages always function with the same pressure gradiant. The caveat is that higher pressure air does have a slightly higher friction coefficient, but that's only noticeable at VERY deep depths, usually well beyond what anyone would breathe air. Helium blends for very deep diving lower the friction coefficient.