The Ouroboros Rebreather

 

One of the benefits of dive trips is exposure to other divers and seeing their gear. My recent trip to Grand Cayman was no exception.  The trip, actually more of an event, was called Zero Gravity and it was put on by Sunset House dive resort in Georgetown, Grand Cayman.  The folks there, most notably Reg Creighton and Erika Leigh-Haley, did an awesome job of putting this all together.  Sponsored by IANTD, ISC, Jetsam, Delta P, Advanced Diver magazine, Dive Rite, and Sunset House, the trip was a showcase of Rebreather diving.  I will be writing a short article on the trip itself and posting it later, so look for that on the site.  One component of ZG is the technical seminars, put on by the sponsors, and the first one was a description/show and tell of the new Ouroboros Rebreather being developed by Delta P Technologies and Kevin Gurr.  Naturally, I was present, in the front row, with my trusty Canon D-60 and a notepad.  Here is what I learned.

 

Photo by Kurt Bowen of Advanced Diver magazine. Thanks for the great UW pics Kurt!!

 

Here is a pic of Kevin diving the Ouroboros.  This unit is the military prototype, the consumer unit will be 4 inches shorter and minus the back cover. The backup display, powered by one AA battery and is backlit, which reads PPO2 or millivolt output of the 3 Teledyne R-17 oxygen sensors, is the highest, most right display in the pic, it has 3 individual digital displays and the RB may be run in manual using only these readouts, the output of the sensors are isolated and sent here and also to the setpoint controller.  The display on Kevin’s right hand is the main display, and incorporates a fully functional VR3 dive computer with additional menus for the RB controls.

 

At first glance, the unit is quite large, but when placed along with all the other units being dived here at ZG, it really is not overly big.  One thing about the prototype that might need to be addressed is that it wont sit vertical on its own. The prototype is quite heavy but will be weight trimmed for production units, no specific production weight numbers yet.  The machining work inside this unit is super clean and neat, its obvious that many hours were spent making the unit elegant, some very neat engineering went into this RB.  This unit has been in development for about 5 years, there are currently 6 units in trials and two of these were here at ZG, Kevin was diving one and Gary the other.

 

Some of the features are labeled in the pic below, such as…

 

Back of the unit minus the cover.

 

Snap in mounts for the gas cylinders, this is a great idea, the body of the cylinder snaps in to the top (labeled) mounts and the neck of the cylinder snaps into the lower mount, no fumbling with hose clamps, Velcro or cam bands.  The regulators, which are both Poseidon X-Streams and are fitted with overpressure relief valves, are in the base of the snap mounts and high pressure SS braided lines connect to the DIN valves of the cylinders, keeping the regs well protected.

The central round pod is the setpoint electronics, on the top is a set of wet contacts that will turn the unit on when they hit the water, the unit will also automatically turn on at 1.5 meters as measured by the depth sensor, there is no master power switch, so no jumping in with the unit turned off, of course you must crack the valve for the oxygen, but there is a pre-dive menu that covers that, more on that later.  Also on the electronics pod is a buddy display with a PPP2 readout in large digits, great if your buddy is above or behind you, but not much use if you are diving side by side.  The pod also has two Fischer ports, one will allow connection of a stainless steel depth transducer, required for saturation diving, and another port for data download or telemetry to send RB health info to the surface or a diver tender.

The unit is provided with an ADV shutoff, reachable through a cutout in the shell, see illustration.

The solenoid is mounted in its own enclosure, not in the breathing loop and is user replaceable.

 

The surrounding philosophy that Kevin has in his design is “no tools required”.  The time he has spent in very far away places working on rebreathers has ingrained this important point into this RB.  He dismantled the unit to its components with his bare hands, all hoses are threaded to their connections, the scrubber has clips that allow its removal, batteries can be changed easily.  All connections requiring a seal are done with double O-rings.  One exception to that is the DSV/mouth piece, which is designed without O-rings and also comes apart easily, the DSV is similar to the Draeger DSV and has a post you rotate toward your chin, or away from it for open or close.  The breathing hose attachments are designed to swivel allowing easy adjustment anytime.  The breathing hoses are armored for crush resistance and have a smooth internal bore, similar to the Mk 15/16 series of RB’s.

 

 Another perspective of the unit minus the outer shell, photo by Stefan Besier at DEMA ’03.  Thanks Stefan for providing the pics I didn’t get.

 

DSV/mouthpiece, notice the threaded hose attachments.

 

DSV/mouthpiece in circuit.

 

A shot showing the mushroom valves and spider.

 

The ability to plumb off board gas into the loop is a mark of an expedition level rebreather and the Ouroboros is no exception.  The unit is fitted with a gas block and outboard connection for the Diluent and Oxygen.  The stem on top of this pic is the off board connection, these blocks hang down on the divers left and right sides near the shoulder straps.

 

The scrubber is a radial design and has 2 sizes with a possible 3rd . 3 and 4.4 kg are the current designs.  The scrubber also requires no tools to load, the top lid is spring loaded by 8 springs and is designed to not require any tamping to fill properly, wont that be a time saver?  If there is any settling of scrubber it will be at the top of the unit and still not allow any channels to form.  The design of the scrubber bed is such that it will maintain a gas path even if mostly flooded.  Other flood resistant features include “one way” moisture drains around the sensor pod, that help prevent moisture from finding the sensors even if the diver goes inverted, and an over pressure/water drain valve in the bottom of the exhale counterlung.  The counter lungs are back mounted, just inside the housing, very close to the divers back, and in front of the scrubber canister. I haven’t dived the unit so I'm not sure how diver position will affect the work of breathing.

 

  Sensor pod, with 4 th position for backup computer or future development of a CO2 sensor.  Quickly removable to keep in a kinder environment between dives.

 

The unit has 3 batteries, all C cells and any C size cell will work, including rechargeable, alkaline or lithium.  One of these is tasked to the main electronics, the other two for the solenoid, but there is a power share circuit that will divert power where it is needed.  Expected battery life is 60 dive hours.

 

 HUD

 

Now here is a nice, easy to understand HUD.

 

The A is a general alarm, when it flashes, there will be a corresponding message on the main display, as well as a vibrating alarm, which can be shut off via the menu, if the fault is corrected, the vib off resets so if that same alarm returns the vib will return too, no forgetting that you shut off the vib alarm, a very nice feature.  A critical design parameter includes alarms, and menus for shutting them off, so if you decide to dive with something out of normal, like, for example, an empty diluent cylinder and are in a cave where you can’t very well fill it, you may shut off the alarm so it doesn’t drive you crazy.  Uwatec could learn something here, nothing more frustrating than a divers computer beeping incessantly.  The general alarm will flash/vib for all faults, as well as HP dil or Oxygen being low, or leaking.  The deco LED has four modes, off for no deco, slow flash for below deco stop, solid for at stop depth and fast flash for above stop depth.  There is a blue LED to show when the solenoid is firing, it is wired to a  transducer so it will light only when the solenoid has actually fired, not just show when power is sent to the solenoid.  The last LED is a set point LED to show when the unit is at, below or above the setpoint, based on the sensor readings.

 

Display, looks a bit like a VR3, go figure.

 

There is a pre dive menu that includes turning on gasses and then verifying them with pressure readings on the display screen,  also a scrubber stack timer to show how much time you have remaining.  The usual calibrating menus are in the pre dive check also.  One nice feature of the main display is that it mirrors the VR3 computer functions but just has additional menus for the rebreather functions, so a short learning curve for existing VR3 users.  The system logs everything its hooked up to, including the pre dive menu, so if a diver skips the menu, and you have the option to do that, that info is logged, just like the VR3, this system will never lock you out of diving, the diver always has the final say.

 

A pic of the buddy display and wet contacts on the top of the electronics pod, which has a cutout In the rear cover of the unit.  Pic taken by Stefan Besier at DEMA ’03.

 

There are quite a few design features pulled from earlier RB designs, most notably the Cis-Lunar and the Mk 15/16 series of RB’s, but all good designers look to the past for things that work and things that don’t.  Those who fail to study history are doomed to repeat it.  Kevin has used many of the best features to incorporate into his design and has done an admirable job.  One major issue that Kevin has had to deal with in the development of this unit is making sure it will pass CE testing.  This, of course requires compromise on some things and lots of frustration on others.  I’m sure Kevin could spend hours discussing just this aspect of development, but I wont get into those issues here.

 

The planned release dates will depend on CE testing, which is supposed to begin soon and be complete by the end of the year, but the unit will be at DEMA ‘04 and is expected to be available for sale by around the second quarter of 2005.  Cost is expected to be around 8000 British pounds.  Not cheap by anyone’s standard, but for an expedition level breather, on par with the Cis-Lunar and Mk 15/16, which Kevin is aiming at, there will certainly be some folks out there who want the best and care little how much it costs.

 

Complete specifications for the unit are available here.  CCRTECHNOLOGIES

 

Thank you very much, Kevin, for sponsoring ZG and taking your time to show and tell your excellent Rebreather.

 

Ron Micjan

2 September 2004

 

At last chat with Kevin on 30 Sep 04 the RB had passed most of the CE testing and is slated to be on the market by March, 05.