Apeks DS4 alternatives for rebreathers

[formernuke]

I think you are confusing depth-balanced with tank-pressure balanced.
As we already discussed, for feeding an orifice with constant flow you need to eliminate the depth-balancing (which is better known as depth-compensation), ensuring the IP stay constant at the same absolute pressure independently from the ambient pressure.
This is obtained closing the holes which allow to the ambient pressure to act on the piston.
The fact that the reg is balanced relatively to the tank pressure, instead, is a good thing even when the ambient pressure compensation is disabled.

I was keeping it simple.

 

[rddvet]

I was keeping it simple.

But that made your statement fairly inaccurate and misinformative. There is a huge difference between a balanced reg and a reg that is plugged for constant flow at depth.
Mind you, I use both. I typically always dive a blocked oxygen reg on my unit, but I have dove it many times with a standard reg. At typical depths its not a big deal, though I dive with a needle valve. Obviously at significant depths its not ideal.

 

[formernuke]

But that made your statement fairly inaccurate and misinformative. There is a huge difference between a balanced reg and a reg that is plugged for constant flow at depth.
Mind you, I use both. I typically always dive a blocked oxygen reg on my unit, but I have dove it many times with a standard reg. At typical depths its not a big deal, though I dive with a needle valve. Obviously at significant depths its not ideal.

Not at all when inaccurate. Manufacturers refer to balanced as environmentally balanced. This feature is dangerous on a revo O2 reg. It is that simple.

 

[inquis]

Manufacturers refer to balanced as environmentally balanced.

Can't say I've heard that term. "Balanced", sure. "Environmentally sealed", sure. Do you have an example from a mainstream manufacturer?

Regardless of any marketing errors, in a normal/non-blocked first stage with an unbalanced design, the IP closes the valve when force from the intermediate chamber side matches that of the spring + ambient + tank force (on the HP seat). The intermediate force differential from ambient is therefore spring+tank. If the spring doesn't break and the tank pressure doesn't change, the differential from ambient doesn't change as the depth increases. (Yes, I'm ignoring the miniscule tank pressure change from increasing the IP.)

ETA: a balanced design has a force differential from ambient of just the spring. So yes, a normal (non-blocked), balanced reg would be dangerous for an mCCR.

Blocking off the reg = preventing ambient chamber pressure increases. Blocking a balanced reg yields an intermediate force that is always equal to the spring force (i.e. constant). This is actually the best option for an mCCR.

Blocking an unbalanced reg yields an intermediate force equal to the spring+tank forces. However, because of the small area of the HP seat, the impact of the tank pressure change on IP is small. This is still fine for an mCCR. More importantly, IP slowly decreases as the tank pressure drops, so there is still no danger of increased O2 flow (regardless of depth).

 

[formernuke]

It's a term thing. Remember these regs are being advertised for use in OC, not CCR. So we are using blocked or unblocked the manufacturers are saying balanced so depth will not effect the gas flow and WOB is not effected.

Problem is those regs on a revo o2 will result in to much oxygen at depth so the reg needs to able to be blocked. Most regs don't have this option.

 

[inquis]

Problem is those regs on a revo o2 will result in to much oxygen at depth so the reg needs to able to be blocked.

Failing to block any reg -- both balanced and unbalanced designs -- will result in greater O2 flow at depth.

 

[Angelo Farina]

Scubapro calls the MK2 "unbalanced" and the MK25 "balanced".
Both increase the absolute IP with depth, so are depth-compensated (hence not suited for an mCCR).
In my understanding, they call "balanced" those regs which are not affected by tank pressure.

 

[berndo]

... the manufacturers are saying balanced so depth will not effect the gas flow and WOB is not effected.

You keep confusing 'balanced/unbalanced' with depth compensation. All first stages have depth compensation unless they're capped/blocked with an aftermarket part for use as an O2 stage on a mCCRs.

 

[BlueTrin]

Just on the kick Apeks theme; have several Apeks regs needing repairs and servicing. Most of my regulators are Apeks (about 10 1st stages and 12 second stages) as they are generally have been very reliable, but now seeing too many failures for my liking.

This past year I've had at least 3 second stages leaking with one doing a full-on free-flow. One cost me around 70 bar of rich mix.
For first stages, a Tek3 needs the seat re-reaming, basically it's scrap until I get a new body which will cost more than a new Tek3 -- that really annoys as they're sold as pukka pro kit. Had a DS4 used for suit inflation literally blow the OPV, thankfully before blowing the hose apart and on the boat before jumping in. Now have another DS4 with IP creep which shagged my digital IP gauge (replacement coming tomorrow).

Not very happy with Apeks and their piss-taking pricing.

Oh, whilst at it, Apeks cylinder valves are crap. People used to rave about them a while back. I regret changing many of my cylinders to Apeks as they get very tight and aren't very resilient to picking the cylinders up by the valve handles where they can leak --- that's what we do for goodness sake.

What’s a good cylinder valve for my stages?

 

[berndo]

ETA: a balanced design has a force differential from ambient of just the spring. So yes, a normal (non-blocked), balanced reg would be dangerous for an mCCR.

I think the pelagian comes or came with an unblocked stage. Not sure though but apparently you can run needle valves with standard stages... might be annoying though.