Super High Performance Regs

[rescuediver009]

I recently read an article that was written by a fairly notable author. In this article I noticed that he explained several principles (mentioned below) that I have not usually agreed with. I was wondering what others think. I am particularly looking for opinions from the guys who really know how regs work. Not the ones who have dove one reg only and have never touched the inside of a reg for anything outside of pure curiosity. Please keep in mind that this gentleman has over 3000 apparent dives and I am not looking to find fault or agree with him, just the concepts mentioned below in the article and their justification not simply what you think:

Environmental seals
Second stage construction (material and venturi controls)
Hose diameter
Upstream (servo-assisted) vs. demand design.

Article can be viewed here.


.

 

[darylm74]

I read this. I'm not that familiar with the inside workings of regulators yet, at least not directly. I went to school for Chemical Engineering, before opting for MIS, and many of the same equipment we learned on for pressurized gas and so forth were the same as scuba regulators, at least in concept. I am going to pull out my old books and look at some of the concepts he brings about. At the very least it will allow me to relate my Chem-E knowledge to my hobby, which I have not tried to do before.

 

[msandler]

Not the opinion your looking for but... What's not to agree with? Metal is better, downstream is smarter and Env. seals DO raise IP. Also, I larger diameter hose whether beneficial as described (which I believe it is) is definitely not a negative.

This is why I own two MR22/Abyss regs, one has an env seal. I have the IP lower on that one for the very reason the article states. even with the lowered IP it still breathes ever-so-slightly more forcefully than the non-sealed unit. Both have performed phenominally below 250'.

I also have SP's MK15/G250 (the original G250 is Metal) and a new Zeagle Flathead 6 /ZX (and IST), the Mares is my fav by a long shot.

Discaimer: I am not a Reg. tech.

 

[Doc Intrepid]

...he explained several principles (mentioned below) that I have not usually agreed with. I was wondering what others think. I am particularly looking for opinions from the guys who really know how regs work.

I think that what Ellyat is saying about regulator design is 'correct' (as far as it goes). I also think its important to place what Ellyat says in context.

As Mike noted, the points Ellyat made are no doubt technically valid. In fact, while I haven't seen a study lately, I suspect they could be empirically proven. But I question how applicable they are for the majority of divers.

This forum, for example, has over 33,000 registered divers globally. Of that total population, what percentage of divers would you think are -
* regularly and consistently
* conducting open circuit (not rebreather) scuba dives
* to depths between 300' to 450' (fsw) or deeper (yikes!)?

For what percentage of this forum, which I suspect is fairly representative of the majority of divers globally, do these facts matter?

In my opinion, Ellyat's observations are not invalid so much as they are irrelevant for all but perhaps a fraction of 1% of the divers on SB.

(Now if you happen to be one of the divers for whom these facts are relevant, then I suspect they are quite important indeed! )

Disclaimer: I'm certified to work on Sherwood Regulators, and I believe I know how regs work, but I'm not a real reg tech either.

 

[WarmWaterDiver]

I am a 'working' (currently employed) degreed Chemical Engineer, but not a regulator tech nor someone who's investigated going beyond 165 FSW depth on open circuit (my in-progress training certification level).

However, there is a lot of discussion here that doesn't take into account the effect of breathing gas quality on the inside workings of a regulator. I did post regarding this months ago, with a vigorous back-and-forth with Pufferfish in Canada. I would say this factor is not something to ignore.

And, I have a bit of trouble following the discussion - makes me wonder if the original text was in a language other than English. I've never heard the term 'reverse adiabatic compression' used for 'adiabatic expansion' before. But, as noted in the previous post I made on this topic, the designs are done so as to render as close as possible isothermal rather than adiabatic process.

The discussions on hose fitting size is relevant only if the ID of the port results in choked flow - my guess is the number of times a single first stage with many second stages attached supplied sufficient breathing gas for more than one diver weren't included in the author's research for this article.

 

[rescuediver009]

Thanks for the replies.
Interesting about the size of a hose's internal diameter. I realize that the hose has an obviously bigger inlet, however, take a look down that inlet and you will find that it tapers down immediately which kind of eliminates the principle of the theory.
As for the Mares reg praise received, undoubtedly they are great regs, but I don't know that I would agree that you are better off in cold water with a reg withuot an environmental seal unless it is specially engineered to perform in ice without one. i.e. poseidon xstream.

 

[Greg Barlow]

Thanks for the replies.
Interesting about the size of a hose's internal diameter. I realize that the hose has an obviously bigger inlet, however, take a look down that inlet and you will find that it tapers down immediately which kind of eliminates the principle of the theory.
As for the Mares reg praise received, undoubtedly they are great regs, but I don't know that I would agree that you are better off in cold water with a reg withuot an environmental seal unless it is specially engineered to perform in ice without one. i.e. poseidon xstream.

The taper in the first stage port is actually an extension tube and is designed to generate a high pressure flow, which creates a vacuum drawing a large amount of gas into the second stage hose. From a scientific standpoint, it relies on Bernoulli's Principle, and is quite effective.

It is akin to the venturi assist that is found on many second stages.

Greg

 

[Paul Evans]

I think that what Ellyat is saying about regulator design is 'correct' (as far as it goes). I also think its important to place what Ellyat says in context.

Mark Ellyat is (or was) sponsered by Mares....................Same guy did 313m on an Abyss.

 

[darylm74]

I am a 'working' (currently employed) degreed Chemical Engineer, but not a regulator tech nor someone who's investigated going beyond 165 FSW depth on open circuit (my in-progress training certification level).

However, there is a lot of discussion here that doesn't take into account the effect of breathing gas quality on the inside workings of a regulator. I did post regarding this months ago, with a vigorous back-and-forth with Pufferfish in Canada. I would say this factor is not something to ignore.

And, I have a bit of trouble following the discussion - makes me wonder if the original text was in a language other than English. I've never heard the term 'reverse adiabatic compression' used for 'adiabatic expansion' before. But, as noted in the previous post I made on this topic, the designs are done so as to render as close as possible isothermal rather than adiabatic process.

The discussions on hose fitting size is relevant only if the ID of the port results in choked flow - my guess is the number of times a single first stage with many second stages attached supplied sufficient breathing gas for more than one diver weren't included in the author's research for this article.

I think they are making reference to the Carnot Cycle with respect to reverse adiabatic compression (there is also reference to reverse adiabatic expansion, which to me seems more relevant to what he was saying). As you know, definitely much better than me, the Carnot cycle goes in 4 steps and between the cycle from step 4 back to step 1, a reversible adiabatic compression process increases the working fluid temperature from T(low) to T(high). This is strictly out of the text book and I can't state how this relates exactly (I haven't touched this stuff in 8 or so years), but just stating what I found and thought this might ring a few bells. I'm sure that terminology in textbooks and terminology in the real world is probably very different as I find that in my own job quite often.


Sorry if I went out on a tangent from this thread....

 

[Scuba]

Pressure drop reduces gas flow.

All other things being equal, hose length, pressure, turbulence, temperature, fluid viscocity, etc. the pressure drop that occurs upon breathing demand can be minimized with two factors: increasing upstream pressure or increasing hose diameter. Both result in increased gas flow volume. My layman’s understanding.

Does the larger hose diameter reduce turbulence?