New Halcyon Rebreather?

[sea_ledford]

I assume its something like this......
In fact it kinda seems similar to a dolphin...

That is exactly what I was thinking! Or a LAR V.

This (should) massively improve the work of breathing (WOB) which is the effort required to suck gas through the scrubber. This gets quite important the deeper you go as the gas is more dense.

Years ago, I had thought about modifying a LAR V as a chest mounted bailout CCR (or a Draeger Dolphin more likely). Problems I came up with:
1- I had no use for a bailout CCR.
2- "Bailout CCR" isn't really a thing, it's just a dual CCR since you can't just ignore it and hope it works when you need it.
3- the WOB on a LAR V is apparently complete garbage deeper than the 20 feet they are supposed to operate at. I don't know if it was the scrubber or the general design, or even if it was true. I only played around with one in a pool a few times.

I still think this is a super weird direction for Halcyon to go in, given its ties to GUE, and GUE's historical reluctance to embrace rapid change. Especially to jump right into SS sensors, wireless transmitters, wireless connectivity to scooters (??).

Waiting for the April 1 update...

 

[grantmac]

Definitely reminds me of the LAR scrubber. I do wonder if the LAR WOB (which is my only RB experience so far) is due to having only one fairly small counterlung rather than the scrubber?

Could this Halcyon actually be a collaboration between the two companies since Draeger hasn't had much success in the civilian realm?

 

[Stefan E]

I'm not sure what a CO2 hit does to impact using the BOV. When you switch the BOV to OC, it closes off and seals the loop so any CO2 in there is out of the picture. The mushroom valves could have flown the coop entirely and the BOV in OC mode is going to work just fine.

That said, my Hollis BOV on my KISS has a piece of crap unbalanced 2nd stage. It's perfectly fine to quickly get off the loop. If I had to stay off the loop for an extended period, I would switch to my S600 strapped to the offboard dil/bailout.

Looking at the patent (assuming it's the one implemented in Symbios), the unit can be divided into two parts - an "outer loop" consisting of the DSV, inhale hose, exhale hose and the gas block. And an "inner loop" with CLs and Scrubber (incl. sensor head). The gas block contains a OPV, combined ADV/BOV and valves in the gas block that can isolate the outer loop from the inner loop.

In OC mode the inner and outer loop are isolated from each other, which means gas can only come from the BOV/ADV, pass through the DSV, and exit via the OPV in the gas block. Btw, when you switch to OC, the spring pressure on the OPV exit valve is removed and it will work like any 2nd stage regulator exit valve.

In other word, regardless if the one-way valves are defect (or even missing) and provided the outer loop is not leaking, inhalation gas can only come from the BOV demand valve. While exhale gas can only exit via the OPV exit valve. Since the inner loop is blocked the volume is constant. The only re-inhaled gas will be in the DSV - more or less the same volume as any 2nd stage regulator.

To me it looks very ingenious, and implemented right it should breath very well in OC, with a slight extra effort to exhale (you will have to push gas down to the gas block to exit).

But there is one thing that bugs me. Both the valves isolating the inner and outer loops close outside-in. This means that negative ambient pressure (-0.1 bar to -1 bar) in the inner loop will force the valves open. In other words, if you descend in OC mode (BOV closed, DSV open) they will act as internal OPV between outer and inner loop and equalize pressure between the loops. All well and fine.

However, if you ascend with BOV closed (DSV open or closed does not matter) the pressure in the inner loop will increase with no way to exit. Since the valves between inner and outer loops will seal shut if the pressure in the inner loop is higher that the outer loop, this means it might be impossible to return to CC and vent any over-pressure. Eventually the inner loop will rupture.

Solution could be a separate OPV in the inner loop. A better solution would be if the exhale valve could close from the inside-out (instead of outside-in). The exhale valve could then act as OPV if the inner loop pressure is significantly higher than ambient pressure, while the inhale valve would act as OPV if the inner loop is significantly lower than ambient pressure. The latter solution would not require any additional components.

 

[justinthedeeps]

Cool that someone designed/built another solution to having an OC gas accessible without change of mouthpieces...

Some say (or hear) that existing BOVs are bulky and restrictive. But there are a lot of people diving BOVs who don't mind. We're using BOVs together with cameras, NERDs, DPVs, drygloves, no problem. It is exactly like integrating a necklace reg into the DSV. Standard BOVs cannot really flood, easy to purge. Can connect directly to offboard gases via QC6, and do your whole ascent on the BOV if you want to.

Se here they put a BOV/second stage kind of solution right on the chest(?) Ok. Looks lite and streamlined. Bubbles would go up between the arms and body near the armpits? Fine.

Does the DSV lever operate the chest BOV? How?
If the loop hoses flood, you have to purge them out before getting breaths--even on open circuit?
If a hole, tear, leak occurs in the loop hose, it continues to affects open circuit breathing?
Does it have an LPI for the dilout input? Is it a high-flow connection? How visible is it for verification?

For divers adding on chest CCRs to their open circuit twinsets--possibly now a large demographic?--how many are even going to bother with onboard OC bailout features? Many of them already don't believe in/have never used BOVs.

 

[Stefan E]

Cool that someone designed/built another solution to having an OC gas accessible without change of mouthpieces...

Some say (or hear) that existing BOVs are bulky and restrictive. But there are a lot of people diving BOVs who don't mind. We're using BOVs together with cameras, NERDs, DPVs, drygloves, no problem. It is exactly like integrating a necklace reg into the DSV. Standard BOVs cannot really flood, easy to purge. Can connect directly to offboard gases via QC6, and do your whole ascent on the BOV if you want to.

Se here they put a BOV/second stage kind of solution right on the chest(?) Ok. Looks lite and streamlined. Bubbles would go up between the arms and body near the armpits? Fine.

Does the DSV lever operate the chest BOV? How?
If the loop hoses flood, you have to purge them out before getting breaths--even on open circuit?
If a hole, tear, leak occurs in the loop hose, it continues to affects open circuit breathing?
Does it have an LPI for the dilout input? Is it a high-flow connection? How visible is it for verification?

For divers adding on chest CCRs to their open circuit twinsets--possibly now a large demographic?--how many are even going to bother with onboard OC bailout features? Many of them already don't believe in/have never used BOVs.

The BOV (gas block) and DSV are independent of each other. The gas block isolates the "inner loop" (CLs, scrubber) and "outer loop" (DSV, gas block), while the DSV lever closes the mouthpiece.

If the DSV is closed and is BOV open, there is no problem ascending. The BOV will act as an ADV, while the OPV will vent gas as required.

The problem I described in my earlier post only arises if you ascend with the BOV in OC mode (irrespectively of DSV lever position), isolating the inner and outer loop. However, since the Halcyon dive computer will sense if you are in OC or CC and change mode accordingly, divers with a Halcyon dive computer will likely close the BOV to quickly change dive mode when they ascend on OC.

If you have a flooded unit, you could close the BOV to isolate the outer loop and press the purge button. This would force water from inhale to exhale side, exiting via the OPV - similar to a 2nd stage regulator, albeit with added volume for hoses and gas block.

The gas block should act as a water trap (for small amounts of water) and it should be possible to clear water (or other fluids) in the breathing hoses through the OPV by using the BOV purge or manually compressing the unit,

Obviously any leaks the outer loop will mean that the volume of the OC loop is no longer static - water will enter on inhale and prevent the gas from coming in via BOV and exit via OPV. In that scenario you would have to BO. Leaks and issues with inner loop (CL, Scrubber) should not impact OC.

With the BOV / ADV integrated in the gas block, you can only examine the BOV from the outside. The LPI attaches directly to the gas block and is hidden inside the cover. I expect most will have a short hose with a QC6 to attach to diluent.

 

[justinthedeeps]

@Stefan E thanks for the info!

I guess loop floods and leak damage to hoses are pretty rare during a dive.
The flexibility/mobility of a simple DSV at the mouth will certainly appeal to many.

Seems like the capability to get full-flow, safe, isolated open circuit gas from the chest valve without (or before) changing mouthpieces to a different regulator adds an option of safety and convenience to this rig that does not exist in other non-BOV rebreathers.

 

[tostr]

It seems that there are divers already certified on the device:

GUE Instructor resumé | GUE

www.gue.com

 

[Heat Miser]

It seems that there are divers already certified on the device:

GUE Instructor resumé | GUE

www.gue.com

wonder what agency?

Waiting for the April 1 update...

where is the April1 update referred to?

 

[Wibble]

Any more news about the Halcyon Symbios rebreather?

When? How's the CE approval going? Etc.