ИДА 64
The IDA 64 is a Russian military oxygen rebreather developed in the mid 60s and in use for decades as the standard-issue Russian Navy combat swimmers/commando rebreather. These pages consists of pictures taken as I prepared it for use after some 28 years in stores. They are my notes and I hope they aren't going to be used so you can say "Poor Nigel. So that's what he did wrong."

Mine, apparently, dates from May 1976 when it was newly placed into stores with all the stamps and test approvals. There is no way I can tell if it was refurbished for re-issue or brand new but I suspect new based on the manufacturers date stamps matching the issue documentation.

The original specification reads a bit scary, remembering that this is a pure oxygen device:
Working depth20m
Working time4-6 hours
ScrubberO3 (Superoxide) or HP-I (2 x 1.8 litres)
Weight16 kg
Counterlung volume7 liters
Neutral buoyancy
OK. Let me start with a quick reprise of oxygen rebreathers so we know we are using the same words for things:
An active human being consumes roughly 1 litre of oxygen per minute and less if at rest. However to flush out the carbon-dioxide produced by our bodies we need to pass somewhere between 10 and 25 litres per minute of gas through our lungs. Hence just breathing from a cylinder and letting the exhaled gas bubble away into the water is a very inefficient way to go diving. Recirculating the breathing gas and removing the carbon dioxide chemically means a much greater efficiency and, significant to the military, almost no tell tale bubbles.

So, in its simplest form, a diving rebreather consists of a loop, gas flow is constrained by one-way valves to circulate through the chemical 'scrubber' and there must be some provision to replenish the oxygen consumed. One further device required to facilitate a practical rebreather is flexible bag so the loop can change volume to accommodate the divers inhale/exhale cycle. The diver's lungs then take as much oxygen as they require and release carbon dioxide. This exhaled gas passes into the scrubber and then into the flexible 'counterlung' ready to be inhaled again. When enough oxygen has been consumed so that the counterlung can no longer supply a full breath a valve from the oxygen cylinder opens to top up the loop. Hence the operation is normally independent of the diver. Provided he has set it up correctly if he can breathe all is well.

Oxygen addition can be performed in several ways. Oxygen sensors and computer electronics driving valves is a possibility, a chemical system where CO2 removal causes oxygen release works, a constant flow system where a fraction of the loop gas is being replaced all the time is an alternative but the simplest trick of all is to only have only oxygen in the loop so if the loop has gas in it you are OK.

However you never get something for nothing and oxygen, despite the fact that we need it minute by minute to live, is a very reactive, even dangerous, gas. Oxygen as 100% of your atmosphere is unhealthy long term and rapidly becomes worse under pressure. Current theory proposes that the maximum pressure of pure O2 that you want to breathe is 1.6bar, the pressure you would get breathing pure Oxygen six meters under the water. This means the pure oxygen rebreather is seriously depth limited.

Right. Let's unpack the box.

Firstly a warning. Clicking any of the pictures takes you to the original master I scaled it from. They are all about 900K+ raw files from my 4M Olympus so don't grab them all or we both get a big bandwidth hit.

The crate is timber, 79 x 50 x 32 cms, has going to sea type handles, catches, hinges and brass corners. The rebreather comes packed in its rubber lined fabric rucksack with a set of documents wrapped and placed on top.
Underneath is a pair of scrubber canisters and an oxygen tank complete with first stage, valve, contents gauge, a set of tools and a set of spares.
The scrubbers and the tank are spares as there are units installed in the rebreather. Most parts of the system come packed in paper and I removed some before I took these pictures. That is what is stuffed at the right hand end of the case.
The scrubbers appear to be axial flow units. They are filled through a screw plug at the bottom and flow gas through the ports at the top. They are symmetrical so they could be installed either way round but the two units when I received it were mounted with the seam on the top so the exhale side feeds down to the bottom of the stack and the scrubbed gas leaves from the top. The words ВДОХ and ВЫОХ probably tell me that (four different on-line translators convert them to English as 'Breath' and 'Vyokh' but if Vyokh is English it's not the English I'm familiar with).

They weigh 1.6Kgs each and I managed to jiggle 1.95Kgs of 1.0 to 2.5mm Inspiration Sofnolime into each of them. Since the Inspiration takes about 3Kgs perhaps the quoted 4-8 hour duration isn't too far fetched.
The tanks have various stamps and appear to be Aluminium. Two values of 200Att and 300Att I guess are working and test pressure, 1.73Kt probably its weight (I will check this) and 1.02 perhaps its capacity. At 31cms end to end I could believe more than one litre but it will do for a first guess. КИСЛОРОД (Kaislorod), by the way, just means Oxygen.

Incidentally I have not discovered anything yet, except the spanners in the toolkit, that a magnet sticks too. Since it is made mostly of conductive aluminium it is not undetectable to active magnetic sensors but to passive systems it should be virtually invisible.
The valve is a combined first stage, over pressure valve, on/off switch and fill adapter with a high pressure contents gauge take off.
Push the lever down to switch off and the little thumb plate clicks forward. To turn on press the lever to release the thumb plate, hold the plate back while releaseing the lever. It takes a very deliberate, but still one handed operation to turn things on.
This is the filling point. It is a quarter inch BSP thread like so much scuba gear world wide but not a standard shape. I sent one of the bits from the spares kit to Subaqua Products and, as usual, they fixed it for me. This is a 300bar DIN female, to match my filing whips, with a quarter inch BSP female with a set of custom cut PTFE washers down the bottom. They made me several washers.
The contents gauge is only 4cms in diameter and clips to the chest of the system.
Here is the main case. No I haven't worked out what the red elastic is for but it is attached in several places. You couldn't reach anything there...
The lid has two clips/hinges. The one at the top is a big pin that pushes through the hinge and the one at the other end pulls out a bit to release the cover. Neither of them work well as hinges as the case wants to go together straight but I can't see why they are different.
The back of the case shows the OPV, the over pressure valve, that dumps oxygen from the loop as you ascend. Since this is conventionally used with full face masks the old trick of dumping round your mouth-piece doesn't work. You can also see the valve control down by the diver's right hip.
Here are close-ups of the OPV and the demand valve. More details on the detailed tear down page.
This is the counterlung. The documents say it is 7 litres and only on the inhale side. The exhale feed actually passes through pipes inside the bag to the two scrubbers (in parallel). The scrubber outlets go into the flexible bag which is also connected to the OPV and the demand valve.
text
This is the mouthpiece. Notice the weights on the hose as it comes over the shoulders. The switch on the front is either rebreathing or external feed. Remember that this is conventionally used with a full face mask.
Isn't it beautiful? That is a spring pressing on a mica disk. Quite the most exquisite one way valve imaginable. Clearly built on a defence budget where we were the baddies.
This is the tool kit. The lumps of metal at the bottom perplexed me until I offered one up to a valve. As you can see the kit is comprehensive and, in fact, fits some of the things I have here that I haven't got spanners for.
Can you guess what it is? I couldn't. Thanks to Dave Sutton (see links) for an explanation. Apparently I have box one of two. The suit, mask, fins and stuff were shipped separately in a second, standard navy sized crate and this is the suit inflation bottle. At most it is 800ccs and it is marked 150att so not much volume. I can only assume the curve is so it can fit in a body hugging pocket.
The mask, since it came in the other box, was missing. This was a chance find on Ebay. A diver in Hawaii had it and was getting asked questions about dimensions by a Canadian because there are two slightly different variants. However when it came right down to it he didn't want it as much as I did.
It measures right as it fits my rebreather.
Clearly I am going to have to learn some of the hands off methods for clearing my ears.
Finally a drawing. It looks a bit primitive but actually it diagrams all the parts and how they work so it's quite handy.
  1. Over pressure dump valve
  2. Counterlung (inhale only)
  3. Dump pipe to bubble supressor
  4. Exhale hose
  5. Exhale one way valve
  6. Surface/Loop switch
  7. Inhale one way valve
  8. Oxygen Addition Valve
  9. OAV diaphram
  10. Inhale hose
  11. Oxygen addition mechanism
  12. Oxygen feed pipe
  13. First scrubber canister
  14. Second scrubber canister
  15. Oxygen pressure reducer valve
  16. tank contenst gauge
  17. Tank shutoff valve
  18. Oxygen cylinder
Other IDA 64 links
Diver Dave's Rebreather Site
Valeri's Rebreather Pages
Jan Bech's oxygen rebreather database
Michael Brant's IDA64 pages
Russian military rebreathers
Other Russian rebreathers
I have used information from all these people in my work to dive this unit and I would like to thank them for sharing the information without cost on the web