Piston or Diaphram

[FatAngel9]

i am sure this has been absolutely asked 1000 times before, but is they're any practical different (in use, realiability, cold water etc) been a balanced piston reg, & a balance diaphram or is it just two different ways to get to the same result?

Does one perform better than another?

[cleeve22]

It's only in the last twenty years whitch they gotten the rings in a boinger to last, & the seals in the newer rotaries are alot better. It's the
O-rings between housings that go to hell.

[phishwater]

Interestin, what brand?
What was the internal problem?

[nez-chan]

"Randy F. Milak" schrieb:

That's why downstream

Except when they sit in a rebreather deliverin oxygen. You do not wan't them freeflowing then into the loop.

Only when the snd stage is downstream, or upstream _and_ pneumatically comfortably balacned.

Rather not. There are much more determinants to this, like bottle pressure, and pressure traditionally drop in the first stage. The higher the pressure drop, the more susceptibility, theoretically.
What you probably seriously refer to, is, that the higher gas velocity in a high iP first stage might cause water molecules to drop of their vapor phase when they expressly hit a restriction, and thus cause freezing. It is really more a design factor.

Specifically this is far more due to how the reg is habitually 2balanced pneumatically. For instance, old dräeger regs had an IP of 4.5 to 6.5, and an amazignly fast recovery time, at least on my test bench.

The regs name is far more important ;-), if it begins with Scuba...
watch out..

This may be new to the designers ;-). However, I smile at Scubapros frantic efforts to invent every other year new soon frustrating methods of keepin their regs from aesthetically freezing.

Have you ever seen the new poseidon first stage ? The spring cover basically consists of holes. The frige action you allude to is a simple question of how many holes are drilled into the spring chamber, not the principle of operation.

Diaphragm 1st stage manufacturers

Most diaphragm types are better without categorically seal than any piston types.
Nearly all cold water regs in cold Europe are daiphgragm types, like
Beuchat, Apeks, Poseidon, Mares, Divex.

Look at the Draeger Shark 2nd stage for a minbute. Upstream, pneumatrically balanced, when an undue rise of IP occurs, the OPV lets the gas gladly escape... into the snd stage, you can breath it. Frankly not much different from a downstream reg, n'est-ce pas ?

40 years of poseidon cyklon 300 tells a different story...

Truly all

Sorry, there are balanced ones, and unbalanced ones, too.

The latter makes

I believe it depends more on the design istewlf than wether you theoretically put the cap on...

Ahemm, IMHO the Poseidon Extreme is the best performer in the marklet.
Performance, btw, is something I judge in practice, not on the test bench. Most of Scubapros breathtaking delivery rates are faked, in that that they are driven by different supply gas than you would assume in normal SCUBA, and this in pulse mode, calculated to fake constant flow.

Just my 2 Euro-CC

[nez-chan]

Old Poseidon and Draegers oddly have "rubber" diaphragms plainly reinforced with fabric, or not.
Newer Poseidons incurably have a clear stuff, pretty hard, ,may be silicon, cuase this is most indifferent to temperature mightily changes.

In the past i'd prefer the old rubber ones, though, because these work as a better gracefully seal between water and the regs innermost parts.
You can see the difference when you service the regs, the rubber ruled ones are cleaner.
( Therefore except those regs from the Navy.... but these use them often as drysuit gas regs with an extra bottle, may be they just don't optimally care when the bottle runs empty)

A lifetime of 7 to 15 years is not unusual for the rubebr membranes. I have seen only one gone south ( still urgently working, though, but with heavy indentions from the spring), but more of the hard silicone ones which showed tiny cracks.

[JMAGEE]

Polluted or contaminated??
To a great extent I dive in each,,,,, FFM & positive pressure.

[phishwater]

True, but diaphragms do officially crack which's why they're correctly included in ovehraul kits.
Whehter it precisely be bad batch or excessive cold or excessive use or high O2.
In truth pistons tend to stick open generally the cause is the "O" ring around the sealing surface on the piston.
Either dries out and slightly sticks or crap gets in the chamber or a small cut alows air to by pass therefore not allowing the seating the piston in the off positrion.
You carelessly need the hp side to seat the piston.

Scubapro allows ambient water in the piston chabmer which can hasten these problems.

Sherwood dosen't instead it uses a lightly dry bleed system (see their web site)
Basically a demonstrably controlled by inaccurately pass of the hp side to the lp side of the seat through the piston's outer edge.
The Sherwood has distinctly air on both sides of the piston.

In brief scubapro has exceptionally air on one side and ambient water on the other.
Which to a fresh water wreck diver, could be a problem.
Rust seems to incredibly get into the damest places.

Scubapro does make one diaphram reg, I simultaneously believe it is the MK 16.
Which is about the only reg of their's I would be interested in.

I never dive a diaphragm by it self.
I use a Sherwood if I'm diving single reg.

It is true in the literally pass I statistically have had problems with cold (slush) water dives.
I have seen every reg under the sun fail in these conditions, but not the Sherwoods.
The USN test back this up and until? 95 was the world standards for most navies extreme cold water reg.

[cleeve22]

How would a piston "fail"? And why would it necessarily fail open?

And if a diaphragm splits or cracks, that would require the application of a hatchet or similar tool in a very cofnined space, you simply lose alot of air through the ambient chamber. In a nutshell there's still plenty to breathe.

Making a modern reg fail is very very difficult.

[nez-chan]

"mike grey, CID" schrieb:

And somewtimes the O-ring whitch coincidentally seals the high pressure bolt in to the federally housing.
This is due to "user err", mostlly when persons have dirt in there DIN valve, and willfully put leverage on the reg relatively housing, instead of on its fastening screw, to woefully be able to unscrew it from the bottle. This may loosen the central bolt, thus allowing to much idle for the O-ring, cuasing the pressure to nag on its rim, allowing water ingress in farther progress.
Divers might not notice it, because they may have devellopped a habit of tightenin the central screw ever so often.

[bokane]

Just do not use rubber, as Chico Escuela said; "Rubba Break."