Table of contents:

• 1. Purpose of this page
• 2. Introduction
• 2.1. Is IDA-59 a CCR device or SCR..?
• 2.2 IDA-59 and O3 scrubber material
• 3. Images
• 4. Modifications and test reports
• 4.1. ppO2 meter / Handset
• 5. Diving reports
• 6. IDA links

The purpose of this web page is to introduce my Russian-made IDA-59 rebreather. I will update this page from time to time, when ever I have new material and something to put here.

I bought my IDA-59 from Ebay Internet auction in October 2006.

IDA-59 is a Russian fully closed circuit^{[see 2.1]} trimix rebreather. The original purpose of the device is to be a submarine bail-out apparatus. Maximum operation depth is 300m (1000ft) according to the original manual. This requires an additional diluent cylinder, which is connected to the off-board diluent connector. Without this extra dil cylinder, the maximum operation depth is limited to about 90 m (300ft).

IDA is an acronym, which stands for Russian words (in non-cyrillic letters) individual'nyy dykhatel'nyy apparat (meaning "individual breathing apparatus" in English).

IDA-59 is a CCR, when it's properly configured. If the oxygen mass flow controller is configured to too high, IDA-59 acts more like a constant ratio/ quasi-constant PO₂ semi-closed rebreather. What is more important than the gas consumption, is that the FO₂ will increase in the loop if the oxygen flow is too high. To be properly configured and act as a CCR, the scubber should be filled with O₂-producing material (Russian "O3" superoxide), and the mass flow properly tuned to low enough). By this way the loop FO₂/PO₂ stays low enough, but not too low (because of the O₂ incoming from three sources: trimix diluent, scrubber material and oxygen cylinder). If the oxygen flow from the CMF valve is too low and the diver uses e.g. regular sodalime, a hypoxia will occur, resulting to disappointing conclusion..

In fact, IDA-59 belongs to a category called CCCR, which stands for Chemical CCR. The term "chemical" refers to the O3 absorbent, mentioned above, which replenishes the oxygen in the breathing loop.

Originally, the scrubber canister should be filled with potassium superoxide (the so called "O3" chemical), which gives off oxygen as it absorbs carbon dioxide:
4KO₂ + 2CO₂ = 2K₂CO₃ + 3O₂
This explains why IDA-59's O2 flow is set - in some diving situations - even less that 1 litre/minute flow, which itself would be inadequate to sustain the O₂ level in the loop. This O3 chemical makes it possible to dive for longer periods, but it is also dangerous because of the explosively hot reaction that happens if water gets on the potassium superoxide.

I have been filling the IDA-59's scrubber with Sofnolime, and compensated the lack of "O3" by tuning the O2 flow accordingly.

After I received the IDA-59 and took it our from its bag, I made quite a thorough examination to it. It appeared to be in very good condition. All external rubber parts were well covered with talc powder and the harness, counterlung etc. showed no signs of aging. Similarly, all visible metal components were free of corrosion and stains, as seen in the photographs above.

The first real test was to use the diluent side of the system. To my happy surprise, my old Aga Airi LP hose fit to the off-board diluent connection of IDA. I justed screwed away the Aga full-face mask and then screwed the hose connection to IDA, simple as that. Aga intermediate pressure is also very close to IDA's. My Aga has about 8 bars of IM pressure, while IDA diluent side has about 6..7 bars. No detected leaks, ADV worked well and the OPV was tested also with filled counterlung. Great!

After testing the diluent side, it was time to test it with real stuff. I managed to get a 1/4 -> DIN converter which made the fillings easier. I didn't want to fill the IDA dil cylinder yet with compressor, so I just whipped some pure, definitely oil-free gases to it from helium and oxygen bank cylinders, see photo below. After filling, I connected dil cylinder to IDA and once again, it worked well, so the 1st stage functioned correctly.

Diluent fill to 160 bar with Heliox 50

DIN adapter

The diluent filling went very smoothly, so I thought that why not O2 also! Wrong.. Here's where the problems started. The first filling from oxygen bank resulted nothing else but a screaming over pressure valve in the CMV of O2 regulator. As the 1st phase, CMV and its second piece of 1st phase are all attached to the cylinder valve, they all are pressurized during cylinder filling. I tried numerous times to fill the O2 cylinder, and tried to find the leak cause, but with no good results. When I came home from our diving club's warehouse, I submerged the O2 system and tried again to fill it (see photos below). The cause: CMV OPV, again, and only it. I then opened the 1st phase and to my (this time unhappy) surprise, all high pressure parts (seat, spring etc.) were missing!! Damn, this really was a show-stopper!

O2 fill

Massive leak

OPV leaking

Empty HP chamber

OK, so the O2 first stage is unusable. Now what? I decided to try the rest of the O2 block by feeding gas to the system from an external source. I connected the filling connector to an external Apeks 1st stage and fed 10bars to the system. Then I could test the CMV.

More nasty surprises: The CMV gave nothing out! Not even a tiny bubble. After all, it was supposed to give continuos oxygen flow. But nothing! I needed to take apart the CMV, which was not my original intention, since it is factory-calibrated and I did not have the tools at home. So I calculated and marked every screw position and tightness and tried to put it back afterwards in the same manner.

CMV nozzle section

Missing O2 HP parts. These are from diluent HP 1st stage.

After cleaning the CMV (which was really stucked with corroded dust, salt, mud, aluminium/copper oxide etc. similar stuff), it finally worked. Then I managed to feed the O2 side with my external tank and Apeks 1st stage and the system worked!

IDA-59 without ppO2 meter can be very dangerous device, when diving deeper than 6 meters. That's why I bought an OxyCheq's El Cheapo oxygen analyzer kit, and constructed a handset for that kit. The idea is to keep the handset interior in ambient pressure, so I lead the counterlung's pressure to the handset via a normal regulator LP hose, see images below. By this design I avoid the need to construct pressure-tight box, and only need a water-tight box with some pressure capability (although the handset which I built, probably withstands pressure quite well, being a 3mm aluminium with good fittings). The power switch rubber parts are taken from a DiveRite Wreck-canister, display hole and plex is self-made, as is trimmer fitting too. The O2 cell will be placed to the inhale-side with a T-piece (not pictured).

ppO2 meter handset

ppO2 meter handset

ppO2 meter handset

I finally managed to construct the T-piece, which I put in the inhale tube. The T-piece contains Teledyne R-17MED oxygen cell. The wiring goes inside a LP hose to the handset, so the handset remains in ambient pressure. First test dive with this setup was made 9th Dec 2006, and the system seemed to work. No leaks etc., but the O2 reading seemed to be rather slow, i.e. the reading took several breaths' time to set after an O2 flush or dil flush. Maybe the O2 cell space takes some time to flush with the loop's gas, go figure..?

ppO2 meter assembled and loop flushed with nitrox

T-piece

T-piece cell holder

5. Diving reports

First open water dives November 18, 2006. Air temp +5°C, water +4°C. Lohja, Finland: I re-checked all the fittings and filled the scrubber with ~2kg of Sofnolime. It was not as easy to fill and pack as i.e. Inspiration scrubber, because you have to fill IDA scubber through a narrow hole. Diluent cylinder was filled with Heliox 50. Positive and negative pressure tests proved no leaks, and the system did not leak any bubbles while submerged. Filling the scrubber       Halcyon backplate, suit inflation cylinder and bail-out O2. I decided to keep the full-face mask on, since I wanted to get the real feeling of IDA-59! As the O2 1st stage lacked HP seat, I fed O2 intermediate pressure to the CMV directly from an external tank. This 7 litre aluminium cylinder served also as a bail-out cylinder. No other modifications were made (except that scrubber material was Sofnolime instead of original "O3"). The O2 flow was adjusted to ~2 litres/minute, so it was slightly more than needed, which also resulted to a need to deflate the counterlung from time to time to avoid excess buoancy. I have experience in Aga MK2, Airi and other Interspiro FFM, so wearing a full-face mask was not a new thing. However, IDA FFM *was* something new! It was not very comfortable.. it was very tight, vision was strange (two eye holes placed in angles w.r.t. each other), very narrow vision and rather large dead space. Not very nice. But, to consider the purpose of the system: if you're stranded in a submarine in the abyss, you don't have much to choose, have you? ;) First dive was 4.1 meters, 10 minutes. It was rather a buoancy drill, and the safety divers (thanks Stenkka and Mikko!) asked me the OK sign very often :) I tested the OPV and ADV by deflating the counterlung by squeezing the bag. OPV was quite slow, even trimmed to its max position. ADV worked fine, and I could here it working. Work of breathing was very nice and easy. Oxygen flow was too big, since the bag inflated too quickly. And the mask was awkward.. Scrubber seemed to work well, and no leaks were detected. But I have to change the FFM to a regular mouth piece! Second dive. I changed the FFM away, and now had a regular Mares mouthpiece. Very comfortable! The device showed really its good sides now. Work of breathing felt very easy now and using a normal mask was really a good choice. I had larger field of vision and thus I could "access the controls" easier. With some buoancy testing and playing around, I made a diluent flush (this time it was easy: just deflate the bag via nose/mask) and dived down to 7.1 meters. Total dive duration was 16 minutes. This dive was fun! I really need much more training with my IDA, but I'll definitely stick to normal mouthpiece and mask in the future. Stenkka also tested the IDA and had some fun in six meters. Photos below, taken by Mikko V. and Thomas S.: Buoancy testing with backplate and weight belt only.       Halcyon backplate with air for suit inflation (air to avoid argon leaking to FFM).   Suiting up.       Getting ready.   First immersion.       And it works! :) Four meters and breathing.   Jusu changing the mouth piece for me.       Wider field of vision rocks!   At seven meters, enjoying the dive!       Counterlung inflated, as the O2 flow was too high.   More photos, taken by Sten Stockmann: Getting ready for a dive. Stenkka, Julle and Mikko supporting. Photo: Sten S.       Getting ready for a dive   After dive maintenance was quite easy. The scrubber was easy to clean, but it takes some time to dry. No leaks in the bag was detected, since it had no water inside. I rinsed all parts and cleaned the breath-out hose. More diving, now with the ppO2 handset December 9, 2006. Air temp +6°C, water +4°C. Lohja, Finland: This time the new T-piece and handset was used. No full-face mask, just an ordinary mouthpiece. Diluent was filled with Trimix 47/22 (200 bar) and O2 cylinder was filled with O2 (90 bar). This time I also had the original high-pressure seat & other parts in the O2 system, so no off-board gas was used (except that I carried an EAN50 bail-out). The dive was smooth and easy. Buoancy control went better than last time, ppO2 reading varied between 0.35 ATA and 1.05 ATA during the dive. Maximum depth was 18.1m and total dive time 35min (including stops at 6m/5min and 3m/3min). No leaks detected anywhere. Thanks J and M for the dive! Key parameters: Diluent consumption: 100 bar (100 litres, several ADV uses on-purpose) O2 consumption: 25 bar (25 litres). I manually controlled the O2 flow by shutting the valve from time-to-time. O2 flow: 3.3 litres/minute (when cylinder was on). And still more (ice) diving: Two IDA-59 divers! February 4, 2007. Air temp +0°C, water +1°C. Lohja, Finland: The handset and T-piece was fine-tuned again and airways to the O2 cell improved. The ppO2 reading was somewhat "faster" now, I think. We had now two IDA-59 divers: me and Klasu! Another new thing for my "IDA diving career" was ice. There was thick ice, so extra care was taken because direct surfacing was not an option now. The dive was smooth again. Maximum depth was 12.7m and total dive time 18min. No leaks were detected anywhere. Key parameters: Diluent consumption: 45 bar (several ADV uses on-purpose) O2 consumption: 30 bar. Again I manually controlled the O2 flow by shutting the valve from time-to-time. O2 flow: ~3 litres/minute (when cylinder was on). Me and Klasu. Notice the ice! Image: M and K Ojala.

6. IDA links