Regulators with Flow Adjustable Knobs

[mikeycanuk]

I've found on my XTX200 that I keep the knob all the way in. I've been actively working to get my SAC down and having some resistance helps slow down my inhalation to the point I easily beat my wife's air consumption.

 

[Colliam7]

What's everyone's experiences with regulators that allow you to adjust the flow of air with a knob mid-dive? I've just started diving Hollis D212s, and it's a very new experience compared to normal regulators. I like the idea, but not sure what the possible drawbacks are...although for switching regs I am finding it tricky at first; when not in use I have my backup set on the lowest setting to prevent freeflow, which means I barely get any air when I switch to it at first. Then I would accidentally set it too high when in use, and during a switch it would violently freeflow if I forgot to adjust it back down before removing from my mouth. . . . Ideas on these regs?

Interesting questions. Hard, for me at least, to comment on whether your second stages are properly tuned. However, keep in mind that you are experiencing several changes, not only from a) a second stage without UAB to one with it, but b) a different brand / model, and probably c) a switch from 'service adjustment' to 'factory adjustment'. It also sounds like you are quite possibly making too many adjustments. Maybe a lighter touch on the knob is in order.

I personally prefer second stages with both a venturi control (lever), and user-adjustable breathing (knob). The only time I experience a free-flow is when the second stage needs to be serviced, outside of periodic service. And, I have only had that (freeflow) happen once in the past 8 years, and after servicing the reg, it was resolved. I never figured out what the problem was (e.g. sand / grit in the second stage / whatever).

When a second stage is not in use, I keep the venturi control in the pre-dive position. I don't make any change in the UAB knob - the venturi control is all I need. In general I seldom use the UAB, anyway. I have it set on the majority of my second stages in a position midway between relatively 'open' and 'closed', At times, I open the knob all the way, but that is usually on dives below 160 ft. Above that, I get plenty of air with a mid-range position.

So, try using only the venturi control lever, after finding a comfortable setting for the UAB. It might make things easier.

 

[eelnoraa]

I've found on my XTX200 that I keep the knob all the way in. I've been actively working to get my SAC down and having some resistance helps slow down my inhalation to the point I easily beat my wife's air consumption.

hmm, off topic, but I don't think this is the right way to reduce SAC. If you body needs the air, and you restrict the breathing by making it harder, it result in C02 retention, which can result in much worse situation.

 

[docmartin]

I use a HOG and tune it so it creeps slightly at the knobs least restrictive setting.
While diving, I will adjust it so that it is the least restrictive without creep.

When getting gear ready for a dive, I will keep it in the most restrictive setting to prevent free flow, and adjust as needed once in water.

And, when the reg is packed, I store it with the knob in the least restrictive position to help minimize LP seat imprint.

for those that set it at a slight creep: make sure you turn the knob all the way in before soaking your 2nd stage post dive.

 

[redacted]

for those that set it at a slight creep: make sure you turn the knob all the way in before soaking your 2nd stage post dive.

Unnecessary.

Try a vacuum test to prove it.

 

[tbone1004]

for those that set it at a slight creep: make sure you turn the knob all the way in before soaking your 2nd stage post dive.

agreed with awap. The slight freeflow is a function of the spring pressure being ever so slightly less than the IP, not the fact that it isn't sealing properly. The UAB adjusts the spring pressure, so if the IP is higher than the spring pressure it freeflows. This is why downstream second stages don't require OPV's on the hose or first stage, if the IP exceeds spring pressure, it freeflows. It's still sealed perfectly tight when the IP goes back down though during soaking, though I will agree that if you are soaking while pressurized you should turn it back so it doesn't freeflow.

 

[Got2Go]

for those that set it at a slight creep: make sure you turn the knob all the way in before soaking your 2nd stage post dive.

Not necessary...spring still applies more than enough pressure to maintain the LP seat sealed closed.

Unnecessary.
Try a vacuum test to prove it.

This...

agreed with awap. The slight freeflow is a function of the spring pressure being ever so slightly less than the IP, not the fact that it isn't sealing properly. The UAB adjusts the spring pressure, so if the IP is higher than the spring pressure it freeflows. This is why downstream second stages don't require OPV's on the hose or first stage, if the IP exceeds spring pressure, it freeflows. It's still sealed perfectly tight when the IP goes back down though during soaking, though I will agree that if you are soaking while pressurized you should turn it back so it doesn't freeflow.

And this...

 

[scubatoys]

Hi guys. Thought I might chime in here. It has been my belief that regulators are designed to breathe as easily as possible at all times regardless of what depth. Why would you ever want to make it breathe worse? There are many theories as for what to do with the adjustments but this is what I do with them and what I tell most of my customers that ask about them in the store. You have two adjustments. One is the Venturi adjustment and the other is the inhalation adjustment knob. The Venturi knob has two settings. Dive and Pre-Dive. This is designed to be turned to the Pre-Dive position when the regulator is above the surface or out of the mouth. It prevents the regulator from accidentally cracking open and free flowing. I dive the Atomic B2, which doesn't have the Dive/Pre-Dive switch. It is done automatically with the AFC (automatic Flow Control) It can sense pressure from depth and turns automatically opens as soon as it reaches that pressure. The inhalation adjustment knob is designed to adjust the pressure applied to the spring that holds the seat firmly against the internal air supply barrel, holding back the pressure from the 1st stage. By adjusting it inwards, you are pushing the seat tighter up again the barrel therefore making the regulator require more effort for inhalation. Adjusting it outwards will release pressure off of the seat and allow the regulator to breathe easier. If you roll it open all the way then some regulators will have a slight free flow. In my opinion there is no reason to make your regulator require more effort to breathe at any point. I simply tune the adjustment knob so that it is on its easiest possible setting without free flowing. The adjustment knob doesn't get touched again until the regulator requires it. Over time the constant open and close of the regulator will cause small nicks, creases or (imprint) to form in the seat which causes it to no longer be able to hold back air until you apply more pressure on that spring again. I look at it as a tool allowing optimal breathing while still getting the most longevity out of your regulator due to not having so much pressure against the seat all the time. It will buy you time between services. Some might be experiencing a few issues of free flowing due to constant re-adjusting of this knob. As every time you apply more pressure on the spring you are forcing the air supply barrel to pierce further and further into the seat. Once you have gone so far into seat, it makes it hard to seal due to the deep crease that you just pressed into it.

 

[rhwestfall]

Few things that an adj. offers: A slight turn saves a dive where it begins to pi$$ a bit. Maybe a current condition might want you to "stiffen' it up a bit, or if you have a good tune (stage/pony) and want to lower (not eliminate) risk of gas loss by not turning off the first stage, risking damage.....

I've been diving 109's & 156's since 1988. Along with them, I now own G250v's, S600's and HOG Zeniths. Absolutely sold on an an adjustable stage, but I don't frequently utilize the adjustment knob on every dive....

 

[docmartin]

awap, tbone, got2go - that sounds logical. So why does the Apeks manual state that you should turn the knob in all the way when soaking?