CCR Technology's Ouroboros

CCR Technology's Ouroboros
By Martin Smith



Background

I’ve been diving since 1983 and first started using mixed gas in 1992, completing one of Rob Palmers’ early courses in order to be able to dive the deeper Channel wrecks and remember where I’d been. After a lot of experimentation, our group arrived at an open circuit configuration of twin 12’s and side mounted twin 10’s which would give us around 20 minutes bottom time in the 80m range while sticking to the rule of thirds. Much deeper than this entailed carrying more and bigger cylinders and really the dive became “mission-based”.

I dived early rebreather units, such as the Cis-Lunar Mk IV, Peter Ready’s Prism, an early Draeger, and waited hopefully for the stillborn Oceanic CCR or one of the other high profile units that were exhibited at the Tek shows in the early to mid 90’s to make it to market. It wasn’t until 2001 however, that I took a year out from deep diving to get to grips with the by then fairly well proven APD Inspiration. I’ve been using this for diving UK wrecks down to the 100m mark as well as some deep wall diving abroad. It took me a couple of years (and, in honesty, a level 3 gas course with Richie Stevenson) to get my “open-circuit” head off and think like a closed circuit diver. The biggest advantage of the CCR for me is the removal of time-pressures afforded by the extended gas duration – on open circuit, a couple of minutes extra on the bottom could throw the gas planning calculations out and eat into safety margins with CCR this is less crucial giving time to resolve any issues.

The Inspiration is a practical and robust piece of kit and has brought rebreather diving to the masses. Despite the fact it has been used successfully on a number of extreme missions, I felt that there were some intrinsic issues – single processor, single power source ( I know it’s two batteries but they are in the same box), no back up PPO2 display, no ADV (at the time) and the possibility to breach the loop since the none of it is armoured and the chest mounted counter lungs could be damaged - I know of a couple of people who have had this happen. Some of this can be mitigated (a Delta P Vr3 with a 4th cell, an OC/DSV to get off the loop quickly, the excellent Bob Howells’s ADV) but after talking to Kevin Gurr in 2003 about his design philosophy for his new, as yet un-named rebreather and having known and dived with Kevin since the early days of Michael Menduno’s US Tek conferences, I asked him to put me on the list for the first commercial batch available. And so, in June 2005, I took delivery of the new, streamlined, carbon fibre, very black Ouroboros.

The Ouroboros

The unit arrives packed in a robust foam rubber lined wheeled case, designed for rough airport handling, which adds to the first impression of quality when the case is opened and the carbon fibre clam-shell is revealed. A quick glance at the solid machined Delrin components, the short lengths of flexible braided steel-sheathed high-pressure hose, the hard microbore internal piping confirms that this is designed up to a specification and not down to a cost. However, it still has a hand-made look about it, not surprising as at the moment the unit’s are made by hand in the Poole, Dorset facility. As an analogy, think of TVR, turned out in small numbers in Blackpool and with tactile hand-machined aluminium switch-gear that puts Jaguar and Ferrari to shame with their re-used mass market components.

I’ve heard people say the Ouroboros is a big rebreather – in fact, it’s dimensions (30cm deep, 40cm wide, 60 cm high approximately) are not dissimilar to the Inspiration (34cm deep, 42 cm wide, 62cm high, taking into account the chest mounted counterlungs).

Design Philosophy

Kevin believes above all in maintaining the integrity of the breathing loop and only coming off the loop onto open circuit bail-out as a last resort, and the Ouroboros is designed around this principle. I won’t go into a full technical specification here (this is available on the CCR Technology website) but here are the key points.

Breathing Loop

The vulnerable parts of the loop are either armoured or hidden. The back mounted counterlungs sit underneath the Delrin stack in close to the diver’s back (and therefore lungs), and are made of a very robust material. The loop itself is made of armoured and uncrushable in normal use, the fittings are Delrin with double o-rings protected from ingress of dirt and grit. Although corrugated externally the loop is smooth on the inside to reduce work of breathing. Physical breach of the loop is therefore very unlikely – provided that the unit passes it’s pressure checks on the surface, it should stay that way. In the event of water getting in via the mouthpiece if this is accidentally knocked out of the mouth then the design of the stack housing is such that it’s unlikely to get into the stack itself, and water can be blown out of the loop via the exhale counter lung - on the course, I flooded the loop, cleared it and carried on diving for another hour.

Use of narrow bore hard-wired gas piping keeps the loop volume to a minimum, the volume is around 6-8 litres compared with over 10 litres on the Inspiration.

Stack

The canister is a radial rather than axial design with curved vanes to Kevin’s design, which give CE stack life of 3.5 hours. APD recommend changing the stack after a 3 hour duration, with additional conditions, but one chamber test showed the Inspiration breaking through at 40m after 1hour 40 minutes and another chamber test showed breakthrough times at 100m for the Ouroboros are much higher that for the Inspiration. It would really help if manufacturers would publish the graphs of depth/breathing rate/temperature and CO2 breakthrough rather than the spot CE test figures that are given. The result is that we all experiment, and it seems that Ouroboros divers are comfortable with diving over 4 hours on a fill, I’ve certainly run it frequently to 6 hours. The canister is sealed inside a Delrin dome with double O-ring seal on the inner and outer edge of the stack. Work on a 20kg tub of Sofnolime to give 6 fills of the canister.

Electronics and Displays

The electronics pod is in a sealed and potted compartment together with an independent power supply. Three C cell batteries give a working life of 10-12 hours and the electronics have fail-safe built in to switch out less essential functions and to switch to the battery with the most power remaining in the event of battery failure. Because these are cheap and readily available cells, Kevin recommends switching all out at the same time. All cables into the electronics are potted so flooding any of the display will not result in an electronics flood. The cells all have jack-plug style, which are much less vulnerable to water damage, and the wiring is again potted.

There are 3 independent displays. The primary display is housed in a Vr3 casing hard wired and potted into the electronics. This sets the rebreather parameters and then manages decompression, summary screen’s, PPO2 displays, alarms and is the main way to interact with the unit. It uses Vr3 functionality extensively and in fact, it seems as though the Ouroboros functionality has been layered over the top of the CCR version of the Vr3. The passive O2 display, again in a casing derived from the Vr3 shows direct readings from each cell without using any electronics and is therefore available in case of complete electronic failure. The passive display uses it’s own separate and independent power supply, a AA cell located in the passive unit itself. The HUD, again potted, runs from the electronics pod and indicates solenoid functioning, PPO2 high or low and decompression, as well as an alarm buzzer for parameter violations. The unit can be flown pretty much on the HUD once you’re used to it. There is also a large display on the back of the unit giving PPO2 in 5cm characters to allow your buddy to monitor your PPO2.

Peripherals

The whole unit is housed in a black carbon fibre clamshell. 2 steel offboard 2l cylinders are mounted with Kent Tooling brackets into a sculpted niche in the backplate, connected to inboard Poseidon Xtreme regulators by flexible braided hosing. The adjustable ADV again uses an Xtreme regulator. Two custom made sliders, accessible from a slot in the bottom of the clamshell, allow isolation of the oxygen and diluent supply. Manual O2 and diluent addition is by 2 valve units, mounted flexible braided hose and which are attached to the harness straps.

The harness and wing are Custom Diver, and there is a specially made stainless back plate, which is somewhat thinner gauge than normal, probably to help the unit get under the crucial 32kg packed weight for airline baggage. Both the crossover harness and the wing have a proliferation of dragon-headed snake logo’s, just in case you (or anyone else!) forget where the name came from. I’m reserving judgement on the wing and the harness – I don’t normally like cross-over style, and the build quality of these items doesn’t seem in keeping with the rest of the unit.

There is deliberately no OC/DSV, nor is there any facility to run inflation whips or regulators from anywhere on the breathing loop, in keeping with the philosophy that the rebreather is the rebreather, and all bailouts and alternative gas supplies are managed separately on the standard unit. There is an upgrade, which allows offboard gas to be plugged into the manual gas addition valves – it would in theory be possible to run gas out from these also to allow safe access to onboard gas supplies.

Preparing the Unit

The first task is to take the breathing loop out of it’s nice padded bag, check the mushroom valves and the mouthpiece purge valve with the usual sucking and blowing and fit the colour coded opposite-threaded ends on to the unit. There is no way to get this wrong, and virtually no chance of leaks originating here. Once connected up, loosen the Delrin dome covering the stack and unseat it by inflating the split counter lungs, which live underneath the stack. Lift off the dome, remove the scrubber unit and pack the radial, doughnut shaped scrubber unit with Sofnolime. The stack is billed as “self-packing” due to the spring loaded top plate which holds the Delrin retaining plate on top of the sorb. In fact, it’s quite fiddly to pack. The correct amount of Sofnolime must be poured in (the sticker marking the fill level fell off instantly), and must then be spread evenly around the stack, ensuring there are no fills gaps around the vanes and ensuring uniform height. This can be tricky, even with the small tool supplied (and instantly lost) to help with this. Unlike the Inspiration scrubber, tapping the sides doesn’t ensure even distribution of absorbent. The large knurled retaining nut, which holds the spring plate in place, can be difficult to screw down, the technique is to lean on the plate, screw down a quarter turn, and repeat lots of times. It gets easier as technique improves and the unit beds down a little, but that’s the hardest part done. The stack is placed back into the unit, checking that the cells all look OK before fitting, the Delrin dome with a cunning and easy to use locking ring fits over the top, and the whole is seated in place by pulling a negative pressure from the mouthpiece, and the unit then stays on negative while you continue preparation. There’s no rummaging about the unit trying to trace pesky leaks, because (generally) there aren’t any – everything is hard wired in. On the one occasion, I did have a leak, easy to detect with a failed negative test, it was easily traced to a grain of Sofnolime in the exhale counterlung overpressure valve, which was removed in a few moments.

Pre-dive Checks

Once the unit is physically prepared, the next step is the pre dive checks. The unit is started up in the same way as the Vr3 with a press off the master handset buttons followed by a long press. This then takes you into the Ouroboros start-up screen. There are a number of pre-dive checks dictated by the handset, covering pressure checks, cell health and calibration, functioning of ADV, slide valves, solenoid, a five minute pre-breathe and also covering testing the functioning of bail out. Deliberately, you can’t short-circuit these checks other than just by stepping through and checking everything OK on the handset. If a calibration is required, then you have to come out of the start up checks, calibrate and then start again. Kevin’s philosophy is “break a drill, re-make a drill”. You can either regard this as a pain in the arse, or as a way to stay alive – up to you. If you really go through the checks before getting in the water then I can’t think of a scenario whereby you could get in with a rebreather that’s about to fail. The quickest way to get in the water is to perform some of the external checks whilst on the five minute pre-breathe. The pre-breath display features a temperature indicator to indicate the sorb is getting activated but no PPO2 display, so you must check PPO2 on the passive display.

The last check is suit/wing inflation, and then if everything is OK the unit moves into a pre-dive screen and shows system OK. If it’s not OK, it indicates what the problem is with an alarm and a handset display.

Annoyingly, the alarms can’t be turned off during the checks and so lights flash and buzzers buzz on the HUD as the parameters come into range.


Diving the Unit

Work of Breathing and Trim

This is what it’s all about. Although the Inspiration is undoubtedly an excellent unit, one of my main issues with was that, after spending some years streamlining my open circuit gear to give an uncluttered chest area, the Inspiration sticks its oversized counterlungs in the area I wanted kept free. So with it’s back mounted lungs, this is what you get with the Ouroboros. Of course, one of the penalties of this, so I had heard, was the increased Work of Breathing (WoB). On the first dive, it certainly felt different, but not harder to breathe, than the Inspiration. Lying on your back does make it harder to breath and causes “hamster cheeks”. Overall, such attention has been paid to the resistive WoB that after one or two dives it’s completely unnoticeable. Briefly, the resistive WoB is that characterised by the resistance to breathing inherent in the design, such as the size of the pipes, restrictions in the loop such as corrugations, mushroom valve and mouthpiece design, and a great deal of attention has been paid to this in the Ouroboros in order to overcome the inherent issues with back mounted counterlungs in the form of increased hydrostatic work of breathing, which refers to the position of the counterlungs in relation to the divers lungs. The counterlungs are, however, mounted high up on the back and this can lead to a slightly head up position until trim is sorted out. Using an O’Three crushed neoprene suit on my course, in freshwater I started with about 12kg of lead (compared with 4 mounted on the unit on the Inspiration). I now dive, even in the sea, with just two 2kg weights mounted on the straps provided at the top of the unit and this weight trims me out nicely. In use, the mouthpiece sits balanced nicely in the mouth, chest area is uncluttered, and with the top weights, trim is fine. During the dive, it’s very easy to get used to diving the unit completely on the HUD, looking at handsets less frequently for confirmation or in case of alarms.

Handsets and Electronics

The cables for main handset, fitted into a modified Vr3 case, the HUD and the passive display exit the case via a slot cut into the middle of the case, just behind the backplate. The main handset is wrist mounted, the passive has a clip and the HUD is mounted onto the mouthpiece with a Delrin bracket. I run the handset on my left wrist, back up Vr3 on my right wrist, passive display clipped across my chest with a piece of shock cord between the case and the p-clip so I can stretch it out for viewing. In use, the main display is as per a Vr3 with 4th cell, defaulting to a screen saver showing PPO2 in big letters, depth, and time to surface. Pushing any button brings in the normal Vr3 dive screen. Change gases, bail out to open circuit, play games, exactly as you would on the Vr3. An additional screen accessed from the main menu takes you into an alarm summary, and this is the first place to go if an alarm is indicated. In here the cause of the alarm can be viewed, and they be turned off in certain circumstances.

Now, alarms. There are lots. There are alarms, indicated by flashing handset lights, by HUD lights and by the buzzer mounted in the HUD for everything from low on-board gas pressures, high gas flow rates, PPO2 out of range, deco ceiling, and ascent rates, battery warnings and other stuff I’ve almost certainly forgotten. On early software, this was a pain but it has improved steadily and the latest release makes this much more user friendly, with the ability to switch off certain alarms permanently and with some additional buffering in the alarm parameters. But in general once you’re into the dive these are not seen much. Certainly, it’s true to say that the PPO2 is very stable, with almost no drift even on dives of several hours.

Gas

O2 and addition is carried out via a manual inject mounted on the right shoulder on the gas block. Due to the very low volumes of gas on the medium pressure side of the circuit, manually maintaining PPO2 is very accurate. Emptying the whole of the dead volume from the O2 circuit causes a rise in PPO2 of no more than 0.1-0.2 bar. Diluent is added by a similar manual inject on the left hand side, and by the ADV. Both are controlled by the slide shut-off mentioned earlier. When new, having hands like a gorilla helps with manual addition (so Phill Short has no problem) but they do ease up. Offboard gas is a plugged in via (extra cost but essential) Swagelock adaptors. These can be used one handed, under pressure and whilst not up to the standard of the excellent Parker fittings on the Cis-Lunar Mk V are very good.

Harness and Mounting Stuff

As with all new systems, there is fiddling around to do with harness (more on this later) and finding where to mount bailout, torches, and the other essentials we need to take with us. Something to take into account with the “keep the rebreather separate” philosophy is that there is no option to run any external devices like the wing or suit direct feeds from the unit, so a bail out bottle must always be carried, with a regulator mounted on a necklace. Some people inflate their suits from bail-out but I’m not a fan of this in case I need to hand the bottle off to someone else, but also because it continually takes the top of the bail-out requiring it to be re-filled. Therefore, I carry a 1.5l aluminium suit inflation tank clipped onto the back plate. Because the wing is rarely used in drysuit diving, some Ouroboros owners don’t bother to plug a direct feed in to it, and just unplug the drysuit inflator and plug it into the wing when required, usually only at the surface. I’m not keen on this either, and so I run a n additional direct feed of the suit inflation bottle. In general, it’s not easy to mount things onto the clamshell (on the Inspiration I drilled the back of the clamshell to mounted spare O2 and suit inflation on G-snaps) so this is why the suit bottle is mounted where it is. My Sartek HID battery back is mounted via bungee cords on the opposite side through eyelets in the wing. Reels are mounted at the back on the crotch strap (aaarggghh – sound a bit like DIR!). Spare torch, a nice little Greenforce LED is mounted on a harness strap, Remora knife on an LP suit hose. EPIRB, spare mask, small Co2 inflate yellow SMB in a waist pocket, spare main SMB in a leg pocket on the suit.

Bail-out, usually in the form of two 7 litre aluminium tanks, is easily carried side slung with that nice clear chest area and the obligatory Poseidon regulators have both second stages, Swagelock fittings for offboard gas and a spare low pressure inflator on the 30% Nitrox. I like to carry additional offboard O2, just a 1 litre aluminium tank and so far I’ve mounted this onto the existing onboard 2 litre steel O2 bottle.

Tools Needed in the Field

A Leatherman and maybe a small adjustable.

Problems and Modifications

The unit has been back to the factory a several times. I’ve had a problem getting it to hold a negative test (there’s no real way of doing a positive pressure check) which has been due to holes in the counterlungs, complete mystery how they got there and rapidly replaced, and a leaking mouthpiece, which has no o-rings and which was rectified by fitting new springs. Early on, the electronics pod cracked and flooded, which was due a design issue that’s now been rectified. Even then, I was still able to ascend and complete deco by using the passive display. A couple of oxygen cells disintegrated and were very quickly changed under warranty. Due to the scrubber design, it’s possible to get a lot of Sofnolime dust under the scrubber dome. If this gets wet in there. (like with a holey counterlung) a nasty caustic mouthwash can ensue. Last time it was in, Kevin fitted a prototype hydrophobic membrane around the stack, which has pretty much eliminated this. Usefully, if you’re a complete donkey and let the unit fall onto a concrete floor from a bench, whilst it’s in pieces, and thus entirely breaking off one of the 4 bolts which locate the dome over the scrubber to keep it watertight, you can use it with only 3 in place. Kevin told me this when I called him on his mobile in the USA in a big panic as I didn’t think I’d be able to get spares in the Cayman Islands. Thanks, Kev, for not calling me a donkey at the time (although I know you wanted to…).

The CD wing isn’t much cop. I’ve chucked the crap corrugated hose and inflator away and replaced it with a Halcyon one (these are beautiful bits of kit) and I’ll fit the Halcyon wing too, once I’ve cut the holes in it to allow the handsets through it. I’ve also replaced the backplate and CD harness with my old OMS one, which works much better, helping with trim too. I’ve also lowered the unit on the backplate to help the trim.

Also, although it’s about the same height as the Inspiration in use it comes up short, so that you can’t rest it sitting down on a normal height bench. A couple of people tried fitting steel cages to the bottom, with less than total success (you know who you are), and there is allegedly a better modification coming to resolve this.

Overall, it’s pretty strong. While trying to dive off Northern Ireland onboard Al Wright’s Salutay in rather too much wind and swell, I shot straight off the end of the bench I was sat on and landed rather heavily tangled in a big heap of rebreather and stage tanks. Nothing broke! Except me, actually – it hurt.

After Sales Service

Service has been excellent. Any faults have been corrected quickly, and turnaround times have usually been within a week. Jason in the factory is knowledgeable and very helpful. There is a also a dedicated Ouroboros users forum.

Until now machining has been outsourced, but before Christmas CCR took over a new unit and will now manage the machining in-house, which will make it easier next time I break off a vital part of the unit.

The Future

There are already some modifications and upgrades that I want to do, mostly around the Vr3. Later in the year a colour version of the handset will be available, and also the VPM option. And of course the bail-out rebreather….
This year sees some interesting diving planned to around 125m, which although modest by some Ouroboros owners standards (176m deep in a cave, anyone?) is still pretty deep and I’m looking forward to it.

© 2005 Martin Smith



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