Regulator Shut-off

[King Kong Matt]

Mike made clear why he tunes them that way...he is following the manufacturers' specs.

So, either get the manufacturers specs and tell him where he is wrong, or show us your own M.D. so that your own opinions on positive pressure breathing are something other than a typical Genesis rant. It's the VERY least you could do if you are going to expect that from Mike.

Why is the onus always on someone else to prove a point, Genesis? Hold yourself to the same standard of reasoning and argumentation that you hold others to and it might sound a little less like ranting and raving...

 

[Genesis]

prove his assertion.

He claims to HAVE something that tells him to tune these in a way that I believe is dangerous.

I claim he's full of it.

Its his claim to prove.

Never mind that Rodales Scubalab and the CE standards BOTH state that positive-pressure breathing is undesirable and, in the case of the CE standards, there is a threshold value for it beyond which the reg does not meet specs.

Next you're going to tell me that logic doesn't matter and neither does preference (which, when we're talking about the preferred position of an EXTERNAL ADJUSTMENT, is just that - PREFERENCE!) when it comes to where one believes that a particular user adjustment should be set?

 

[MikeFerrara]

When the reg is in your mouth and you stop the inhale the air stops flowing. It does not push air at you. The reg will not sustain a free flow when in the mouth. There is no danger. When the reg is out of the mouth the is the only time the venturi causes enough of a presure drop to hold the diaghram open.

IMO Genesis one of the first things you want to do for your diving career is to stop listening to Rodale's (reference all the pictures of divers with dangly gear and lousy trim). They don't seem to understand the basics yet.

Besise I think they have given great reviews to Zeagle and Apeks regs over the years regs haven't they? They have been testers choices over and over if my mem serves right.

 

[MikeFerrara]

Genesis once bubbled...
prove his assertion.

He claims to HAVE something that tells him to tune these in a way that I believe is dangerous.

I claim he's full of it.

I haven't heard of these regs hurting anyone have you? How am I full of it? I didn't design the thing I just use it and really like it.

 

[Genesis]

When the reg is in your mouth and you stop the inhale the air stops flowing. It does not push air at you. The reg will not sustain a free flow when in the mouth. There is no danger. When the reg is out of the mouth the is the only time the venturi causes enough of a presure drop to hold the diaghram open.

Yes it does Mike, if its tuned that way.

That you don't detect it as "pushing air at you" doesn't mean its not happening.

The difference between that and not, if you can't detect it as air being shoved down your throat, is probably less than 1/4" of water. This is immaterial to your work of breathing at depth, considering that the cracking pressure is typically set somewhere between 1/2" and 1" of w.c. on most regulators.

So why tune it to that kind of hair trigger sensitivity? It makes no sense. It means that if you manage to get a blast of current in the purge you get a freeflow that you then have to mess with, or you have to diddle the adjustments when diving to avoid that, and by twidding the settings will you get it in exactly the same place it was originally? Perhaps in a cave or quarry you might get away with that, but around here, where its not at all uncommon to run into a 1/2 knot current at the surface, it would be a MAJOR hassle, even with your backup bungied around your neck.

Never mind that we tend to do a giant stride around here, not walk into the water. You WILL initiate that freeflow on your backup (unless you've detuned it and are diddling the settings) on entry if you're set this way.

IMHO, far better to turn down the venturi just a touch so that a freeflow will not sustain itself. There is no material work-of-breathing difference between the two settings, yet it avoids a potential risk to loss of gas at depth, and removes the need to play with diver adjustments underwater as well.

 

[MikeFerrara]

I don't know where you get this stuff. I dive in high flow caves and don't have a problem with free flows. I do giant strides in the great lakes and don't have a problem with free flows. I sometimes do a dozen or more gas swithches on a dive and sometimes bump a purge on one reg or the other and I don't have a problem with free flows. If you were correct I would be out of gas and dead 100 times over. Sorry but besides caves I dive the great lakes, gulf and east cost often in current and have never experienced the problems you say exist.

 

[yknot]

Mike- perhaps big problem for me with my regs is that the owners manual doesn't offer any usefull info (IMHO) as to how the reg should be set up so I have been forced to rely on the selling LDS. Some of their past comments have led me to believe that they didn't do much more than assemble the gear. If it was out of tune and/or defective I wouldn't know it, other than assuming that the performance of the regs so far doesn't seem normal. These regs have also been prone to free flowing on shore after a very minor bump to the purge. Those free flows were in warm weather and at least easy to stop.

 

[Genesis]

isn't how you are actually setting your regs.

If a purge will not produce a freeflow, then your venturi is not set sufficiently advanced to produce positive-pressure breathing.

Yknot - here's a couple of tests you can do that require NO tools and make NO non-diver adjustments. Try 'em and see if you like the way the reg breathes and performs better - there's no "risk" in this, in that you're not monkeying around with the internal adjustments - just the one(s) you have available...

1. Hook it up to a tank near a sink. Fill the sink.

2. SLOWLY submerge the reg, mouthpiece up (diaphram down). Note the point where it JUST starts to flow air. The amount of water you are under is (roughly - the diaphram might be slightly recessed behind the cover) the cracking pressure.

If you have a "breathing resistance" adjustment, set it (if you can) so that the regulator "cracks" at between 1/2" and 1" of water. The more sensitive you make this adjustment, the greater the risk of current and such causing transient (self-limiting) freeflows. If you bungee your backup (as opposed to a "traditional" octo setup) you can set the cracking pressure lower, as the reg is in your slipstream and less subject to external pressure on the diaphram while you're swimming.

If you cannot get the cracking resistance set this low, then the reg may need to be internally adjusted or serviced. If you have no external adjustment for "breathing resistance", as long as the cracking pressure is at or below 1.5" of water its probably "acceptable" (but I believe your reg DOES have such an adjustment.)

3. Remove the reg from the water. Advance the venturi adjust FULLY. Perform a hard PURGE and release. The reg will probably freeflow. As it is freeflowing, SLOWLY retard the venturi adjustment until it JUST stops. Re-check by purging again - the reg should NOT freeflow.

Without opening the reg, you have now set up the regulator for pretty close to the best performance you can achieve without opening the case or doing internal adjustments. You should not need to monkey with any dive/pre-dive switches with the reg set this way. If you do a giant-stride entry you may get a short burst of air as the reg goes underwater if it goes in mouthpiece-up, but as soon as the mouthpiece submerges and floods it should STOP - all on its own.

This will not correct an incorrect lever height or bad poppet pressure setting (or balance chamber misadjustment, if you have one), or wear that throws those adjustments off; those require internal adjustments.

Set this way your reg should NOT freeflow either on the surface or underwater if the purge is hit.

None of this violates any "warranty" or requires "technical ability", as none of this touches anything that is not user-accessible and intended to be diddled by the diver.

 

[yknot]

Genesis-I assume by positive pressure breathing you are referring to how I understand something like an Interspiro full face mask COULD work. They offer them as demand or pos. pressure, with pos. pressure requiring something beyond ambient pressure to shut them down. To my knowledge the intent of Zeagle regs is not to tune them to a positive pressure setting but instead leave them as a demand valve. I did have one tech at an LDS tell me he liked to tune his Zeagles to within a hair of permanent free flow. Perhaps mine are not tuned where they should be.

 

[Genesis]

Its a bit like the full-face-mask stuff, but not quite.

The purpose of a venturi is to provide a "hold-open" assist to the demand valve.

When gas passes through a venturi the pressure is lowered. This lower pressure sucks in the diaphram, which tends to hold the demand valve open.

The adjustment changes the position of a "paddle" in the air stream, which inhibits the venturi effect as it is turned down by interfering with the laminar flow of air through the mouthpiece and/or redirecting a small amount of it back towards the diaphram.

Basically, the setting of the control can range anywhere from a dynamic INCREASE in breathing resistance as flow increases, through no increase or decrease, through a dynamic DECREASE.

The latter produces freeflow and positive pressure breathing.

The former produces hard breathing under high demand, but has no effect on low demand (!)

Both are undesirable. The former can result in the freeflow that you experienced, the latter can contribute to CO2 build-up at depth, especially if you get stressed and really start sucking on the reg. Set too far down it can produce a reg that can be overbreathed at high stress levels. Set too far up and you get freeflows and the reg becomes unstable, as you experienced, and/or it feels like its shoving air down your throat (because it is!)

The ideal setting is, from my perspective, where the venturi effect is NEUTRAL. That is, the demand valve's dynamic performance - its inhalation resistance - is identical at all levels of flow from the first crack of air through and exceeding your maximum inhalation effort.

Due to the fact that regulators are dynamic devices, you probably can't get quite to that ideal, but better regulators can be tuned darn close to it. Regs that breathe "evenly" and subjectively are "even" breathers both at the surface and at depth have this characteristic.

See my post directly above yours for a no-tools, no-opening-of-the-case, no-void-yer-warranty and no-screaming-from-the-techie-only-should-touch-your-reg folks to check and set the reg this way.

Go ahead and try it and see if you like it. If not you can always go back to Mike's "factory" recommendations