Piston or Diaphragm

[Superlyte27]

Yes, and as I read more posts on this thread, I realized you guys were talking about "balanced" pistons, although it wasn't stated in the OP.

 

[PfcAJ]

Perhaps you have one of those fixed IP regs some RB divers use for o2? A proper reg delivers ~135pi over ambient. If your reg isn't doing the 'over ambient' part, somethin' is up. Even a mk2 (which is unbalanced) works deep, I use them on safety bottles as a matter of course.

Plenty of folks use pistons deep without issue. My guess is some other factor is at play here.

 

[eeel]

It's not a Ford Vs. Chevy argument. And no, they both won't do for any spot on your rig. Here's why...
Two weeks ago I did a dive to 287'. In my gearing up, I mistakenly grabbed my Piston reg for my drysuit INSTEAD of the proper regulator. Guess what. A Piston reg will not inflate a drysuit at 287'. It's only putting out 140psi. At 287' you are looking at about 127psi pushing back. It took FOREVER to get the squeeze off.

Now, imagine if I had mistakenly used that 1st stage for bailout instead of drysuit inflation. I'd have been screwed.

Fact of the matter is... to answer which regs? Piston or Diaphragm: Both.
Piston regs are bullet proof. They just work, forever, without fail. So, we use them for 100' and shallower like on deco bottles and stage bottles. We use Diaphragm regs on deeper dives because regardless of depth they always put out 140psi.

Peter: This is not one of your better moments.

There is so much wrong with this advice I don't know where to begin.

The reg you grabbed for your EN dive must not have been depth compensating. Note these are usally modified Apeks Diaphram regs on rEvos.

Cheers,

Mark

 

[Superlyte27]

Perhaps you have one of those fixed IP regs some RB divers use for o2? A proper reg delivers ~135pi over ambient. If your reg isn't doing the 'over ambient' part, somethin' is up. Even a mk2 (which is unbalanced) works deep, I use them on safety bottles as a matter of course.

Plenty of folks use pistons deep without issue. My guess is some other factor is at play here.

Look at the Oceanic SP5. It isn't ~135 over ambient.

---------- Post added July 16th, 2013 at 05:21 PM ----------

Peter: This is not one of your better moments.

There is so much wrong with this advice I don't know where to begin.

The reg you grabbed for your EN dive must not have been depth compensating. Note these are usally modified Apeks Diaphram regs on rEvos.

Cheers,

Mark

Negative, it was Oceanic SP5. I'm told it puts out 140psi period. Calling Oceanic now to confirm. All I know for sure is, it wasn't putting out 140psi over ambient at 287'.

I'll post again when I get off the phone.

---------- Post added July 16th, 2013 at 05:24 PM ----------

Peter: This is not one of your better moments.

There is so much wrong with this advice I don't know where to begin.

The reg you grabbed for your EN dive must not have been depth compensating. Note these are usally modified Apeks Diaphram regs on rEvos.

Cheers,

Mark

Mark, recheck your math. Just got off the phone with Oceanic. Everything I said was right on the money with an UNBALANCED reg. The Oceanic SP5 is unbalanced. It puts out 140psi regardless of depth. So, at 287' it's still only pushing 140psi with the water/atmospheric pressure pushing roughly 140psi. There's not much of a net gain. 287' x .445psi = 127.72 (granted that's the math for saltwater and I was in fresh water, but you get the point).

 

[dashthrash]

Yes, and as I read more posts on this thread, I realized you guys were talking about "balanced" pistons, although it wasn't stated in the OP.

Sorry about that yes I am looking at a balanced piston. My LDS is an atomic dealer and I have used them and it seemed to work very well. The ST1 is what I am considering. One other thing that concerns me is service. I notice that I am having an issue with finding service material for that as well as the neccessary tools to work on them. I am just one of those people that likes to know how to work on my own equipment.

 

[Superlyte27]

Double Post

 

[eeel]

The Oceanic SP5 is a copy of the SP MK2. It is an unbalanced flow by piston first stage, but it is depth compensating. If yours was acting as you describe there was somthing wrong with it.

 

[Superlyte27]

Not according to Oceanic. They say it's NOT depth compensating.
I'll be honest with you, I've never serviced a balanced piston, so I don't know what to look for, but I do not see a way for this piston to compensate for depth.

 

[eeel]

Not according to Oceanic. They say it's NOT depth compensating.
I'll be honest with you, I've never serviced a balanced piston, so I don't know what to look for, but I do not see a way for this piston to compensate for depth.

The water pressure is exerted on the piston through the holes in the cap. Many folks are confused by the balanced vs depth compensating thing.

 

[Superlyte27]

I'm not confused, just going by what the people at Oceanic tell me. I've now asked several Oceanic repair people, and Oceanic, and I myself am a certed Oceanic repair tech. They all say the pressure will not increase with depth.

But, I will find out. I have 6 of these things. They are all going to 300' with an IP gauge on them. Certainly they can't all be broken.

-edit-
actually I'm not sure if an IP Gauge would give me accurate results. Okay, now I'm confused. But I will get to the bottom of this.
What I do know if that there are countless posts here on SB and other places that all agree that unbalanced piston regs all get to a point where the ability to breathe on them gets harder and harder as you go deeper and deeper.