wedivebc's Dolphin CCR convertion

schford

This thread is to discuss daves convertion article.

Great article - thanks Dave.

Stuart

Scuba_Vixen

Looks like a nice job you've done there!

I was liking that mounting setup from Ron myself when I saw it on his site.

Since I'm in the planning stages of the same project, (dolphin to ccr) I had a couple questions.

Did you add a second P port for the backup PO2 display? ... I was thinking of using the HSE PO2 monitor ( http://www.oxycheq.com/HS_Explorer_PPO2.html )
with a second P port added as backup, along with my Explorer in the existing P port for monitoring and deco. Are you using an over pressure valve on the O2 supply reg, or is that one of those tiny pony gages I see in the photo?

Is there any down side to using the drager 1st stage for the O2 supply? It's already non compensated, and you can get the conversion DIN fitting so it works with standard DIN tank valves. I know it comes with a higher IP than the DS4, but I would assume that it can be backed down.

I've looked at most of the sites I could find for dolphin conversions, and several seem to push the idea of injecting the O2 seperate from where the diluent is added by the ADV. ..... One guy adds O2 at the inlet to the scrubber, nice fitting he has for using a bc connector for the O2 addition. .... Another adds thru what appears to be a second ADV (it would have to be non functional in demand mode) in the exhale bag. ... The reasoning is that it gives a more stable PO2 within the loop, less prone to spikes.

While adding the O2 thru the ADV seems like the easiest way to do it, do you think these guys who are doing it differently are onto something?

Lastly, is there anyone in the states that would have P ports and the adapters I see on the tecme site in stock?

Seems the Europeans are wayyy ahead of the states on Rebreather stuff.

Again, Nice Job Dave


Darlene

sensor330

Hello,

Techme (http://www.tecme.de/) is the best place to go for all your conversion needs.

I personally would try to inject the O2 on the exhale side of the loop. Lots of conversions have been done putting it in the inhale side, nothing wrong with that but in my opinion it would be safer on the exhale side. I know somebody who have had grand mal seisure caused from O2, and its not pretty. I would save yourself the hassle and get a Apek DS4, its super simple and a lot easier to adjust the IP.

Scott

wedivebc

Thanks for the kind words. Let's see if I can address most of your questions.
I considered the HSE ppo2 but only opted for Mark Monro's kit because it was less than half the cost and I'm fairly handy with a soldering iron. Either setup will require an extra p-port.
Don't use the dolphin 1st stage, many have tried many have failed. Apeks ds4 is my choice for OC and CC diving. Yes I have a overpressure valve on the o2 side and a button gauge. I don't use one on the diluent side because I have an airII (gasp)
I don't agree with sensor330 about the O2 injection. It is a matter of technique. If I need to bunp my po2 I inject a series of short injections, like inject, breath,check, repeat as needed. The only time I do long injects is at shallow stops when it is harder to get the po2 up.
Non-North Americans are way ahead. When you see the price of HE down under, you'll see why. I recently was on a charter boat with some OC divers. They had double 130s of trimix I had a single 20 of trimix. Same BT, I went a little deeper

__________________
Cheers,

Dave....

Man is the only animal burdened with the knowledge he will eventually die

sensor330

I believe there would be no difference under normal operating conditions injecting into the inhale C/L or exhale C/L, but I strongly believe that if the KISS valve were to malfunction and injection is in the inhale C/L the chances are higer that one would suffer one or more O2 toxicity symtoms. Although both theories are not tested as to which is better, logic tells me to inject O2 as far away as possible.


BTW are you up for a dive tomorrow?

Scott

wedivebc

My son got engaged today I am taking him out for dinner. Hows next week for you?

__________________
Cheers,

Dave....

Man is the only animal burdened with the knowledge he will eventually die

Scuba_Vixen

It looks like it's nearly unanimous for the DS4's. Seems the KISS valve is built with an IP of about 130psi expected. Going with what has a proven track record of success is always a wise choice.

I can see Scott's point of injecting the O2 at the exhale side to increase dwell time in the system. Seems that benefit has to be weighed against adding a fitting where one was never intended to be, which could more easily become a failure point than using the ADV which is designed for fittings.


Aren't projects fun!


Darlene

sensor330

Dolphin were never meant be be CCR's either. LOL If i were to build another I would buy the adapter to add O2 into the scrubber from Martin at Tecme.

Scott

Scuba_Vixen

I saw that on the tecme site, it looked like a solid way to add a fitting there. I'm kind of leaning that way myself at this time.

Since the IP on the DS4's is considerably lower than the Drager's IP, is there anything in the demand valve that needs to be changed? Seems a lighter spring might be a plus.

Pondering at midnight,

Darlene

sensor330

No, there is no need to play with it. A properly serviced 1st stage will work great. I used a Posiden (for dil) and had no problems.


Scott