Drager Half fill adapter

[Diver Mike]

Anyone ever use one of the half fill plugs for your Drager.

A friend of mine has a Dragar Dolphin and was asking me about the adapter, but as I have sold the Drager, and never used the adapter, I was not a good source for him.

Mike..

 

[mstudley]

I don't own a rebreather however I have heard that they work just fine. I think there's one on ebay right now.... What did you want to know about them?

 

[Diver Mike]

I was just wondering if they really work of if they are another of those "not so good" ideas.

I had the extend air in my Dolphin so I never messed with the canister.

Now if I could only get one for my CCR. Oh well, cannot have it all.

 

[nl_carey]

Only have about 6 hours on the unit, but have been using the half-fill adaptor quite a lot. Works well, lower WOB, but the lower dwell time bothers me a little bit under heavy workload. For your average recreational dive, I have no hesitation using it - makes it easier to throw away old sorb.

 

[Camerone]

I have one on my Dolphin, and probably have around 75 dives on the unit since I got it. I almost always use the half-fill adapter when diving; probably 50+ of those dives are on the half fill unit...

Generally, I figure a half fill of sorb if I'm diving the normal steel 28 cf cylinder, using the 60% flow on about a 44% fill, and a full scrubber for anything larger. However, my average workload is pretty low at around 0.8 or so, so I don't tax the scrubber particularly heavily. Most of the boats up here in WA like you to be up in an hour anyway (too many bubble-blower types on board...) so two hours on a half cansister isn't really pushing anything in the least.

This gives me two rebreather dives at about the same cost my girlfriend gets two open circuit nitrox dives, and that's really nice

 

[gaschef]

Anyone ever use one of the half fill plugs for your Drager.

A friend of mine has a Dragar Dolphin and was asking me about the adapter, but as I have sold the Drager, and never used the adapter, I was not a good source for him.

Mike..

If you still require one I obtain and sell them on a regular basis from DRager

Tim "gaschef" Stevens BEER DIVERS DEVON UK 01297 22458

 

[diverdB]

I have one on my Dolphin, and probably have around 75 dives on the unit since I got it. I almost always use the half-fill adapter when diving; probably 50+ of those dives are on the half fill unit...

Generally, I figure a half fill of sorb if I'm diving the normal steel 28 cf cylinder, using the 60% flow on about a 44% fill, and a full scrubber for anything larger. However, my average workload is pretty low at around 0.8 or so, so I don't tax the scrubber particularly heavily. Most of the boats up here in WA like you to be up in an hour anyway (too many bubble-blower types on board...) so two hours on a half cansister isn't really pushing anything in the least.

This gives me two rebreather dives at about the same cost my girlfriend gets two open circuit nitrox dives, and that's really nice

What is your MOD At 44% with 60% Nozzel do you just figure mod for 44%?

 

[Camerone]

What is your MOD At 44% with 60% Nozzel do you just figure mod for 44%?

100 feet at MY normal workload; YMMV, depending on how large or small, or in-shape or out that you are. Strictly speaking, the MOD is 72 feet with any workload (ppO2 of 1.4) or 87 at rest (1.6). This assumes, however, that you're breathing pure cylinder gas, which would never happen under normal conditions; those conditions that might cause this situation should have been discovered well before you hit 72 feet. The agencies tell you that this is your MOD, but, of course, they are erring on the side of caution. If you don't know your realtime ppO2, I wouldn't stray too far from 72.

That said, 100 feet is where I'd take the unit, with some caution exercised below 87, and a cautious eye on my ppO2 gauge. Diving this unit without a way of measuring your ppO2 is both a reckless and foolish choice, and I personally make it a rule that I won't dive with people who don't at least sport a Drager Oxygauge, if not an Air Z O2 or VR2/VR3.

These calculations are straight out of Appendix A of the TDI manual to figure this out; any competent organization should have the equations in their guides as well (as I know that there are now other orgs certifying users of this rebreather.) Understanding these fiO2 calculations are absolutely crucial to safe operation of the unit; if your instructor, for whatever reason, did not teach you how to work out these numbers, you have every right to loudly, publicly, and vociferously complain to him and all around him about the quality of training. If you're diving the unit, you need to know how to work this out...your life may depend on it.

For the record, on a constant mass flow SCR, fiO2 = [(fsO2 * Qs) - VO2] / [Qs - VO2]
where:
- fsO2 is source gas oxygen fraction
- Qs is source gas flow rate
- VO2 is oxygen metabolic rate

As I'm sure your high school chemistry teacher always told you - watch your units when you do the calculations I might add to also watch your flow rate - use the actual measured rate for the orifice you choose, as there is a good deal of tolerance and variation amongst the Drager orifices.