Phoenix/HPR/DBE's ready to go again!

[ScubaLawyer]

I have been spending my time productively. I tuned up both of my Phoenix/HPR/DBE regs so I'm ready to go when the diving conditions get good around here.

The USD has a cracking effort of .3" water and the Voit .5" water. Venturi increased on both. Stable 135 psi IP. Massively awesome breathers!

[luis]

They look very nice.


If you actually have a cracking effort of 0.3inWC, you will get a slight free flow when you are in the vertical position (or just about any position other than the horizontal swimming position).

The exhaust valve has a radius of 0.5 inches. That means that in a vertical position the top edge of the valve will be 0.5 inches higher in the water column than the center of the diaphragm. In other words, the pressure on the top edge of the valve will be 0.5 in WC lower than the pressure on the center of the diaphragm. That pressure differential will tend open the demand valve that is set to open at 0.3 inWC.

It is not hard to set a regulator with a HPR or an Argonaut to 0.3 in WC or even a bit lower, but I would recommend not setting it less than 0.6 inWC, for the obvious reasons (as I already explained).


Note: you can try them like they are before you de-tune them. If they don't free flow, then you know that your instrumentation (or how you are taking your measurements) are inaccurate.


Have fun.

[ScubaLawyer]

Hi Luis, thanks for the info.

Here I go showing my ignorance again, but exactly at what point is cracking pressure measured on a magnahelic? I always thought it was the point where you have created a vacuum in the supply hose and then air just starts to flow. Or is it measured when you first have sustained full flow of air. In other words, my USD Phoenix starts to flow at .3 inches WC but doesn't open fully until .6 inches WC. Guess I always just assumed it was the former. Happy to be shown otherwise. Mark

[luis]

Correct.

The "cracking effort" is the vacuum (or pressure differential) required to initiate the opening of the demand valve. At that point there is zero flow, therefore there is no venturi assistance or any other flow dynamic effect.

The water column differential between the top of the exhaust and the center of the demand valve diaphragm can be (and will be) what provides the pressure differential even if the diver is not inhaling. You can actually test this in a pool (or any comfortable calm body of water, even a big tub) with a DSV in the closed position and turn the regulator so that the exhaust is in a position higher than the demand valve diaphragm.


BTW, in single hose regulators they commonly call this issue: "case fault geometry". The "case fault geometry" describes the distance between the center of the demand valve diaphragm and the top of the exhaust valve when the diver is either up-side-down or in any position that places the exhaust valve edge at the highest possible (vertical) distance from the center of the demand valve diaphragm.

The significance of the "case fault geometry" is that it dictates the minimum cracking effort a single hose can be adjusted without getting into a free-flow condition in some diver position. Most single hose regulator cannot be adjusted to have a cracking effort to less than 1 inWC due to the "case fault geometry".

Scubapro went to a lot of trouble with the Pilot and later the Air-1 and the D series (D-300, D-350, D-400) regulators to have an exhaust valve concentric with the demand valve diaphragm (just like a double hose regulator with DBE or the Argonaut). Even when the diaphragm and exhaust are concentric you still have to deal the the radius of the valve and the distance to the top edge of the valve.


I hope this is clear and it makes sense.

[ScubaLawyer]

Thank you Luis. You may have just solved the mystery of my freeflowing 2nd stage on my Calypso IV in certain positions. I recall the cracking pressure was very very low. Gonna check that out. Mark

[h2operations]

Luis,
it added light to a question that I had along the sames lines to an old SH issue I occasionally saw.

[antique diver]

Luis, that's some serious good technical information that I never considered. Thanks!

[ScubaLawyer]

Tomorrow is the day! I'm finally getting my boat out into the Pacific Ocean again for a dive! It has been a while. Taking my Voit NAVY (HPR, Phoenix, DBE....) out for a spin. We are going to look for Halibut on a deeper reef system than we usually dive so I set up my LP steel 95 with an 18lb wing and made sure all systems were go. Thought it looked kinda shiny and all pretty like so I took a pic. Off to slay Halibut, fingers crossed.

[luis]

Wow, those hoses look white. Is that just the picture?

Have a good dive.

[ScubaLawyer]

Wow, those hoses look white. Is that just the picture?

Have a good dive.

Thanks Luis!

The hoses are actually neoprene gray hoses I got about 10 years ago. They are in excellent condition but have faded from too much sun out on the boat. I like silicone hoses too and have them on many regs, but there is something about neoprene hoses that just feel more authentic.

Mark

[ScubaLawyer]

2020 is just getting better and better. Both of my boat partners woke up this morning (separately) with fever, cough, shortness of breath, diarrhea.... So no diving today for me and now I'm worried for them. Argh!

I even had my tank configured just the way I like it. Oh well, for another day.

[luis]

I am sorry to hear about your dive buddy's.



I notice your BC inflator is attached to the bottom. Is there a vent on the top? And how do you open that vent?

[ScubaLawyer]

I notice your BC inflator is attached to the bottom. Is there a vent on the top? And how do you open that vent?

PVC hose parts, TV coaxial cable and duct tape. I've been plumbing my wings that way for decades.

Isn't that how everyone does it?

[luis]

I notice your BC inflator is attached to the bottom. Is there a vent on the top? And how do you open that vent?

PVC hose parts, TV coaxial cable and duct tape. I've been plumbing my wings that way for decades.

Isn't that how everyone does it?

If you are referring about the duct -tape, maybe.

TV coaxial cable...

Are you using this as a push-pull cable? Like bicycle break cables? Or are you just pulling on it?


That is an old Oxycheck wing with no internal bladder. Those are great wings. That is what Christine uses and I think I may have one spare of those wings in reserve.


Is the coax cable for internet access?

[ScubaLawyer]

I notice your BC inflator is attached to the bottom. Is there a vent on the top? And how do you open that vent?

PVC hose parts, TV coaxial cable and duct tape. I've been plumbing my wings that way for decades.

Isn't that how everyone does it?

If you are referring about the duct -tape, maybe.

TV coaxial cable...

Are you using this as a push-pull cable? Like bicycle break cables? Or are you just pulling on it?


That is an old Oxycheck wing with no internal bladder. Those are great wings. That is what Christine uses and I think I may have one spare of those wings in reserve.


Is the coax cable for internet access?

Just yanking on it as a dump valve. I used to run polypropylene line through aquarium air tubing to stiffen it up. This time I tried the coaxial cable. Seems to work just fine. I end up replacing the line inside the dump valve every few years anyway so don't care if it rusts out.

I always hated a BC hose coming over my shoulder. This way it is nice and streamlined.

Love that OxyCheq wing. Very small and compact.

Mark