The D⁶™

Description

The D⁶™ is a chestmounted rebreather designed for cave diving. It incorporates a constant O₂ gas feed through a restrictor with manual bypass and manual diluent injection to a port on the exhalation side of the mouthpiece. Gas flows through the horizontally mounted axial scrubber to an inhalation counterlung (4 l) and back to the mouthpice. An overpressure valve is located on inlet side of the scrubber and a P-Port for an oxygen monitor is on the outlet side of the scrubber. A 2 l cylinder of oxygen is mounted beneath the scrubber with diluent being provided from one the diver's sidemounted cylinders. The whole unit is very compact and is worn over a sidemount diving rig.

Details

* Mouthpiece
* Counterlung
* Scrubber
* Gas Feed
* Chassis
* Assembled

Mouthpiece

A stock Draeger Ray mouthpiece and hoses which terminate in adapters to connect to 22 mm PolyPlumb fittings.

Counterlung

The counterlung is a plain 4 l Ortlieb water bag. Some spiral hose wrap is used to prevent the bag fully collapsing. The cap is attached to a T-piece by an interference fit to a length of 22 mm pipe inside the cap..

Scrubber

The scrubber is made from a length of 6" OD polyolefin gas pipe (5" ID) with end caps held down by latches. One end cap has a P-port (on the inhalation side of the loop) to allow an oxygen monitor to be connected and the other cap (on the exhalation side of the loop) has an overpressure valve to allow dumping excess (unscrubbed) gas. In the event of a flood, water can be blown out of the dump vavle and the rebreather recovered. Also shown are the two perforated end baffles for the sorbent bed with scrims. The inlet and exhaust for the scrubber are two 22 mm tank connectors let into threaded holes in the side of the tube.

The sequence of filling the scrubber. The scrubber is filled from the dump valve end. The loop attached to the end baffle enables it to be removed easily.

Gas Feed

The gas feed was designed by Dave Sutton using a gas snubber as an orifice to restrict the flow of oxygen (this is equivalent to using an orifice). The oxygen goes through a filter (to protect the snubber) and then either leaks through the snubber or can be bypassed by a manual addition valve. Rather than using a non-compensated first stage, I have chosen to use an unmodified first stage with the interstage pressure turned down to deliver the correct amount of oxygen between about 20-30 m. Deeper than this and the ppO₂ slowly creeps up and when shallow it slowly decays.

Chassis

This picture shows the scrubber attached to the chassis of the rebreather - front and back views of the bare chassis are also available.

Assembled

All assembled without ppO₂ meter(s) and off-board diluent.