Piston vs diaphragm... Balanced??

[Nemrod]

Not too sure I agree with you on the reliability Nem.

I am not so sure I agree with myself Herman but the diaphragm type does have an upstream seat. The piston does not. I was not talking reliability, I said failure mode. However, as I said, not sure I agree with myself.

 

[spectrum]

Why do dive shops try to over compensate for this then? I'm really starting to just not like dive shops at all.

You will find that in diving darned few things are absolutes, there are usually numerous options. Meanwhile divers, instructors and dealers develop an affinity for things (that bring them home alive) and it can soon escalate to dogma.

Once you add the commercial aspects of "selling up" or "selling the rack" you need to realize that your best safety net is your own homework and knowledge. Some sellesr really don't even know what they are talking about but they figure they know more than you.

Continue reading and asking, there is a wealth of knowledge here in the prior threads and members.

Pete

 

[Nemrod]

Why do dive shops try to over compensate for this then? I'm really starting to just not like dive shops at all.

Over compensate, I am not following your thought?

N

 

[captainhook426]

My LDS wouldn't even talk about the second stage regulator until he talked about how overbalanced first stages are the only good regulators (holding a $1200 atomic regulator).

 

[FM1520]

They are not trying to educate you they are trying to sell you the regulators they have on the self. Its like going to a car dealer and trying to have a discussion on the pros and cons of different cars and expecting unbiased discussion.

 

[captainhook426]

So if someone has a balanced first stage, why would they need to have an adjustable second stage? Isn't that a little redundant, or counter productive?

 

[herman]

My LDS wouldn't even talk about the second stage regulator until he talked about how overbalanced first stages are the only good regulators (holding a $1200 atomic regulator).

Anyone else’s BS meter peg on that one?
First off - and I did some digging- I can find no place where Atomic makes such a statement. If it was on official sales point it should show up some where in their literature. I know I am going to irritate some Atomic fans but they are more hype than fact. No doubt they are good regs but they are no where near as superior to other regs as their fans claim. That said, the purpose of "overbalancing", which is technically not overbalancing but actually over depth compensating, is to increase the IP over ambient as depth increases to compensate for the increased density of the air at depth...and it does do that, the problem is the effect of that density increase at rec depths is minimal where the reg is concerned. In addition, these first are almost always coupled with a balanced second stage which compensates for the increased IP - compensating for changing IP is how a balanced second stage works, keeping cracking pressure (think of it as the work required to open the valve and start air flowing) the same.

The next thing you need to understand is the first stage has little to do with the performance of a reg. The manufactures and dealers will tell you different but the physics of it say otherwise. Remember that they need "better" models and " improvements" to sell you a new or more expensive reg. The key here is to understand the internal workings of a reg as opposed to it's outer skin. For example, the internal parts of an Aqualung Conshelf is the same as the Titan which is the same as the Legend, the only difference is in their outer appearance. As long as a first stage supplies a reasonably constant IP at a sufficient flow rate to keep up with diver demand- (and ALL modern regs from the late 60s on are quite capable of doing that) then first stage performance has little to do with overall performance of the reg assembly. Granted if you combine a balanced first stage with a unbalanced second stage you will get better performance out of the second stage but you will get even better performance out of a simple unbalanced first stage and a good quality balanced second stage. Balancing both has no real benefit since doing so is redundant, remember the purpose of balancing is to keep the second stage performance constant as tank pressure changes so as long as one or the other is doing that, the other has no significant effect. But again, balanced second stages do tend to be higher performance stages so adding one to either a balanced or unbalance first stage will give you the same performance increase.
I got interested in the whole balanced vs. unbalanced vs. overbalanced thing a few years ago and spent a good deal of time learning about the subject.

---------- Post added May 27th, 2013 at 12:12 PM ----------

Adjustable features on a second stage have nothing to do with it being balanced or not. THe classis Scubapro 109 is not balanced but has a cracking pressure adjustment (one of the best second stage of all time) while many newer seconds are balanced but do not have a cracking pressure adjustment....then there is the venturi adjustment with is a totally different adjustment and subject most diver have no clue about.

 

[Fishpie]

I equate the Atomic 1st stage to the Scubapro MK10.
And with the Jet piston and seat the MK10+.
All are fine regs.

 

[uncfnp]

So guys, can you mix and match first and second stages? Or is it best to put same brands together, ie. aqualung first and second stage? And if I have a Calypso first, do I need a calypso octo?

 

[redacted]

So if someone has a balanced first stage, why would they need to have an adjustable second stage? Isn't that a little redundant, or counter productive?

A little redundant - maybe. Counter productive - defiantly not.


All of my main gas rigs use an older model Scubapro balanced piston 1st stage. They perform well but there is some IP drop as tank pressure falls and a little IP rise as the seat ages and the groove gets deeper. And, over the 3 to 5+ years I normally go between service. I do see some IP creep, but withing specs. All of my primary 2nds are balanced. With a balanced 2nd, such IP changes are mostly self compensating so performance does not change noticeably. Adjustable is different from balanced. Most of my alternates are adjustable (and unbalanced). This give me the capability to detune them when they are just hanging from the bungee to prevent freeflows and still turn them up for easiest breathing when they are in my mouth. Strong currents, surf, river flow, and entries will occasionally induce freeflows if they are not de-tuned.

With very few exceptions, the only real problem with mixing and matching is finding a tech who will service the set-up. Some shops will not service gear that they do not carry.