Drager Dolphin:

[caveseeker7]

jepuskar once bubbled...
To further add to my virtual dolphin price....I have already mentally figured in the cost of the Oxygauge and the Uwatec setup.

The oxygauge connects directly to the new breathing bag, but the Uwatec is inline with the breathing bag and hose....is this correct?

2 PO2 monitors...seems like an excellent idea.

Three sensors, actually, with two readouts. One in the bag for the Oxygauge, two in the Oxy2 hose connector.
Of course, you can always use the bag connector to hook up a VR3 or HS Explorer, so you have back-up computing, too. Will leave you with a vacuum in your wallet, though ...

 

[Scuba Chip]

I have about 125 dives now on the Drager SCR units (Atlantis/Dolphin, I have never used a Ray). It might be 123 dives, maybe 128 dives, but my total is in that area. I find the greatest advantage to be when diving in the 60' - 120' range. You get so much more bottom time than with OC. You can easily get a one hour bottom time at these depths and still have plenty of gas for any necessary deco. With SCR, You don't have to worry about staying out of deco, IF You have been properly trained. You can't imagine how much closer You can get to sea life (the big stuff) when You are without sight and sound (bubbles).
I liken the difference between OC and SCR to the difference between driving a car and flying a plane, respectfully. You have to pay attention to the DETAILS with SCR. You have to have enough self discipline to establish a routine for each and every dive. As long as you are willing to do this, then SCR's are safe, effective and fun. But, if you dive with a buddy who is on OC, You lose all the benefits of SCR, 'cept the warm, moist breathing gas.

 

[jepuskar]

Hey ScubaChip,

Very impressive usage..hopefully I'll be there one day.

Without looking at any materials...isnt the dolphin much better closer to the 60 foot range than the 120?

Ok, I'm not trying to tell you anything you dont obviously know, but let me explain what I know....

The deeper you go the leaner the mix you need, which means a higher flow rate which intern means more bubbling of the unit. Your gas will be used up quicker. Another important aspect is your no deco time....using EANx32 your no deco max limit is 20 minutes at 120ft..we know the air in your breathing bag will be less than that so this will be even less. Also your PO2 will be around 1.50 at 120ft.

I'm not sure I agree with you on the deeper aspect.....in my opinion 20-80ft is the prime range to use this unit in....then again, your the one with the experience..not me!

Can you explain how you get 1hr bottom time below 100ft on this unit..even if you went to a larger cylinder, your still going beyond the no-deco limit..I am ofcourse assuming you want to stay within no-deco. Also, I am assuming a goal PO2 of 1.4 - 1.6.

Thanks,

Jason

 

[Scuba Chip]

Hey Jepuskar (Jason),

With the Drager SCR's (Atlantis/Dolphin) there is no need to fear going into deco. More often than not, I have a deco obligation diving these units. And, I am very comfortable doing so.

I always use the middle of the three orifices for flow rate selection. This simplifies procedures, standardizing pre-dive protocols for me. This easily gives me a one hour bottom time, PLUS any necessary deco, whether I dive to 60' or 100'. You DON'T want a leaner mixture at depth. Nitrogen is still an enemy.

The O2 level actually inspired, in your lungs, is less than what comes out of the EAN tank. Using EAN32 is almost useless in these units, 'cause the actual inspired O2 level, in your lungs, from a tank of EAN32, is about EAN26, which isn't much of an advantage over EAN21 (Air). On the other hand, a tank mix of EAN40, will result in an inspired O2 level, in your lungs, of about EAN32. You ALWAYS have to be mindful of Your MOD (Max Operating Depth) remember. This is a limiting factor.

You plan for "Inspired" O2 levels, not tank EAN levels. Using a richer mix, deco times are reduced as well.

Hope You find this helpful

 

[jepuskar]

I understand everything mentioned, but I am still a little confused on why you dive your unit like this.

The middle of the three orifices is the 50% orifice...if I remember dont they come in 40,50, and 60, with an option for 32?

Ok, lets say you ARE using EANx50 which might turn out to be 40%. Doesn't this put your PO2 value at 120ft to 1.85?

I'm not going to go any further because I am speculating...could you please give me more specifics...I am really trying to understand your methodology and learn something here.

If you could answer these questions for me I would appreciate it.

What is the EANx fill in your tank?
Which orifice do you use..40,50, or 60?
How deep will you go on this combination?
What do you plan your workload to be? Light, moderate, heavy? etc?

Do you dive with a PO2 monitor and if so, what does it say at 120ft?

Thanks in advance for answering these questions....I'm not trying to be a pain, I just think this is good stuff to know and your input would help me and I'm sure others.

Thanks,

Jason

 

[fins wake]

... Jepuskar! You've actually posted the right questions.

You ALWAYS have to be mindful of Your MOD (Max Operating Depth) remember. This is a limiting factor.

It is not the only limiting factor, however. Again, we're talking only about the fear of hyperoxia, and not the fear of hypoxia, which most mass constant flow SCR users should fear more.

Using the inspired oxygen fraction (FO2) equation that you will learn when doing the course (and which all CMF SCR users should know off by heart), and assuming manufacturer's recommended flow rates, we find that Scuba Chip has calculated on a steady oxygen metabolism (VO2) of 1,2 (and a 4 litre Dräger tank).

This metabolism, however, can fluctuate greatly depending on exertion (e.g. currents, CO2 buildup etc)!

Fortunately, Dräger has counted on all of this, and with a metabolism of 1,9 (which I've experienced myself at depth) you'll be closer to EANX27, with a metabolism of 2,5 (very high and unusual but by no means impossible!) you'll still be diving air ...

The risk of hypoxia is very low if you follow manufacturer's guidelines on flow rates - which Scuba Chip has done - but you should NEVER change these rates to a lower value than specified without knowing what you're doing, without using an oxygauge or similar O2 measuring device, and without calculating likely FO2:s beforehand.

You plan for "Inspired" O2 levels, not tank EAN levels.

Not entirely correct. You plan for inspired O2 levels as far as decompression is concerned, but with tank pre-mix as far as MOD is concerned.

Using a richer mix, deco times are reduced as well.

Don't get too hooked on the 'Nitrogen is still an enemy' way of thinking. As we have seen, if the VO2 changes due to unforeseen circumstances, you will be diving lower FO2:s anyway and therefore you should not attempt minimal decompression times. This is actually easier to calculate on many CCR:s!

Due to other unforeseen circumstances (nose breathing, loss bail-out scenarios etc.) the Dolphin is IN NO WAY an ideal decompression diving scuba device! In fact, Dräger themselves strongly advice against decompression diving on the Dolphin SCR.

If I wanted to dive the Dolphin on decompression dives, I'd rework it to a KISS-Dolphin type CCR (and then it's purely on your own liability!). If - as Scuba Chip is - one is of the opinion that 'Nitrogen is the enemy', it is helpful to know that a KISS-Dolphin is quite easy to keep a constant ppO2 on at depth, actually easier than on the SCR! Or one can get an ECCR such as the Inspiration or Prism Topaz. Of course, a CCR has other risks, a KISS-Dolphin CCR will definitely kill you if you don't know what you're doing.

I would strongly advice against using the Dolphin as Scuba Chip is using it, however. Wrong tool for the job. Sorry, mate!

Now I'll step off my box ... :box:

Oh, and you've made good points, Jepuskar! You're not a pain, you'll make a fine Dräger diver! Keep those questions flowing.

 

[padiscubapro]

I would also like to add, if the person has a PO2 monitor the loop can be adjusted simply by exhaling out the side of the moutpiece or nose and forcing the demand valve to add fresh gas..
the greatest liklihood of high po2 occurs while the diver is decending while using a gas thad has an MOD deeper than the dive depth or a diver being worked considerably less than planned.. in this case other than a gas switch block or a bailout bottle with a lower fo2, the diver has to endure this higher po2 or ascend to a shallower depth.


The use of non standard gases (with respect to the nozzle) is a simple concept but is not taught in many drager classes..

 

[fins wake]

The use of non standard gases (with respect to the nozzle) is a simple concept but is not taught in many drager classes..

Actually, some Dräger instructors do teach you things that are 'outside the envelope'. Things like shutting off your valves to check the ppO2 drop (gotta have an Oxygauge! Don't try this at home, kids!), or things like diving deep to an absolute setpoint of ppO6 =1,6 (which, remember is always more in real life by a factor of 0,045 per bar, i.e. often close to ppO2 1,8 due to the placement of the sensor, not a lot of people know this ...).

I think all these exercises are good under (competent) instructor supervision. Have I ever done them? Well, I had a competent instructor ... :tease:

Also, one can do SCR decompression courses on a Dolphin, e.g. with ANDI ...

Would I ever recommend any of these exercises on an open scuba board to newbies? Nope. It's strictly manufacturer's guidelines only. Besides, I reallydo believe that it's better with a CCR for decompression dives.

 

[padiscubapro]

fins wake once bubbled...
Actually, some Dräger instructors do teach you things that are 'outside the envelope'. Things like shutting off your valves to check the ppO2 drop (gotta have an Oxygauge! Don't try this at home, kids!), or things like diving deep to an absolute setpoint of ppO6 =1,6 (which, remember is always more in real life by a factor of 0,045 per bar, i.e. often close to ppO2 1,8 due to the placement of the sensor, not a lot of people know this ...).

I think all these exercises are good under (competent) instructor supervision. Have I ever done them? Well, I had a competent instructor ... :tease:

Also, one can do SCR decompression courses on a Dolphin, e.g. with ANDI ...

Would I ever recommend any of these exercises on an open scuba board to newbies? Nope. It's strictly manufacturer's guidelines only. Besides, I reallydo believe that it's better with a CCR for decompression dives.

I was trying not to put down the most agencies drager programs.. The ANDI programs do teach alot of other stuff including a decompression class..
What many people don't know is the FIRST non military drager class was written by ANDI and was done in germany many years ago.. this was the basis for most of the programs nowadays, while ANDI continued to add extra material and make the classes longer other agenicoes got involved and did the opposite..

ANDI is just about ready to release its 4th (or 5th dont remember) revision of its text...

but the key thing is the only way to really do deco on a drager is to be overly conservative and have po2 monitoring...

 

[jepuskar]

This is some really good stuff guys. I think I have pretty much accomplished what I set out to do and that was to really understand the concepts behind this unit. I understand everything being said.....surprises me..hehehe

I just wanted to add that although one can dive the drager to 130 feet, I really think it is just not worth it considering the tradeoffs. I really think 20-80 feet is a real good range to get the most out of this unit.


Than again, I am a reef diver. I'm happy at 20 feet or 80 feet, as long as their is some kind of reef around me. The thought of diving the dolphin at 30 feet using EANX60 is really appealing to me because of the lack of bubbles, really no worries about deco, and a bottom time of 2 hours+ with the right supply tank and scrubber time, plus no dry mouth and your PO2 levels would not be near hypoxia because of the rich blend and not near hyperoxia because your roughly at 2atm which would put your PO2 at 1.20 right after a system flush, but it would most likely be around the 1.00 range most of the dive.

Then again, diving to 80 feet still is appealing because of the bottom time achieved, but you still would have to becareful and plan a little better.

I am not going to question a person who has 125 dives on the unit to my zero.....but I do know how I would feel comfortable diving this unit..so each to their own.

Jason