The D.S.S.C.C.D.

Posted: September 25, 2006 in Uncategorized
Tags: ,

Words by Aaron Bruce, photos by Sarah Woodford

B&W10 Anyone that read Ron Micjan’s excellent article on the CUMA Rebreather, might be interested in hearing about another military rebreather; the D.S.S.C.C.D. Although out of date and no longer in use, this is still a superb piece of diving kit which can be found for sale at certain websites and antique shops if you look hard enough. For those into Rebreather history or with some spare space in their downstairs bar, one of these units would make an ideal conversation starter!!
The DSSCCD stands for Diving Set Self Contained Clearance Diving and has been in use in the Royal Navy in one form or another since the Second World War. The design criteria was for a Rebreather that was acoustically and magnetically safe so that the diver could RMS (render mines safe) without getting himself blown up. Originally, the Navy stole ideas from the Sladen suit, the Davis escape apparatus and a Rebreather salvaged from one of the Italian Charioteers of the Decima Mas fame found near Gibraltar, they came up with the CDBA (clearance divers breathing apparatus). This unit was an O2 Rebreather that had great success even with its limited depth rating. Over the years things slowly improved until the introduction of mixed gas (nitrox), when the unit was reconfigured to allow it’s use and increase the working depth to 54m. The name then changed to the DSSCCD.
The picture below shows how the suit looked before its demise from the Royal Navy in 1999 and is the one I managed to acquire for personal use. As most of the fittings are non standard it has taken me a few weeks to get adaptors made so the unit can be dived. This unit is now a fully functioning rebreather and works a treat!!

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The unit is a fairly robust and easy to assemble rebreather. The front harness houses the single counterlung, the scrubber, full face mask and the twin emergency O2 cylinders.

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The rear harness houses the weight pouch and quick release system, the twin mixed gas cylinders and the reducer.

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The scrubber holds 1Kg of 797 grade sofnolime. There is a wire mesh filter top and bottom to keep it all in place. One of these is held down by a cover that turns 90 degrees to secure it. The scrubber then sits inside the single counterlung and is sealed by a hand tightened jubilee clip. There is a single hose that comes from the FF mask and this screws directly on to the scrubber. The counterlung also houses the over pressure blow off valve and the pepper pot valve. The over pressure valve is mainly used to vent gas when leaving the surface and also as a safety device if the diver falls unconscious and floats to the surface. The pepper pot valve is used to control the loop volume by venting off gas as a fine mist that is acoustically safe.

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Below the counterlung is the Emergency twin O2 cylinder pouch. The cylinders are 0.38ltr each at 200 bar. A hose is connected from the cylinder valve to the counterlung so the gas can be used in an emergency or, if needed to run as anO2 rebreather.

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The weight pouch is designed like an envelope so when the weight release mechanism is pulled, the whole thing pops open and the weights are discarded. The unit is designed to be used with 12oz ball weights that come in the Rebreather’s storage container. The weight release handle is situated on the right hand side of the diver on his posterior. Unfortunately due to excess weight allowance with UK tour operators, these had to be left behind until a later date. The twin mixed gas cylinders are 2.2ltr each at 200 bar. They are held in a cradle that is secured to the unit via a metal bar and then the belt of the unit slides through an opening on each side to make sure it sits low on the divers back.

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The reducer is of a constant mass flow design that can be fitted with either an O2 jet or a mix jet. Depending on what jet you have, you need to screw down on the setting screw to adjust the flow. The chart below details the relevant information.

Mixture code Flow LPM Max Depth Co2 Life Colour
O2
60/40
40/60
32 ½ /67 ½
1.5
6
12
13
7
24
42
54
60
60
40
40
Oxygen
Red
Blue
Yellow

Once the Reducer is set up and fitted to the rest of the rebreather, a pre-dive card must be filled in so that other divers can view the state of the unit.
There is no form of buoyancy control on the unit other than the counterlung itself. As most of the diving was done in UK waters a dry suit with a small inflation cylinder was used as the main form of buoyancy. When diving in a wetsuit, the diver had to weight himself according to the task at hand. If the job was situated on the sea bed, a lot of divers would be slightly negatively buoyant so they could kneel on the bottom and survey the mine. If they were doing a ships bottom search they tended to slightly over inflate the suit, enabling them to get right up against the hull without having to fin to stay in place. This meant that more effort could be made looking for any limpet mines that could have been placed.
I managed to take the unit for a shallow dive the other day to make sure I remembered how to dive it and to make sure it actually worked. The first thing I remembered was how uncomfortable a nose clip was!! After eight years of “normal” diving my nose had either grown or I was unaccustomed to the pain that I was receiving. After 40 minutes of swimming around and drills practice, my nose felt like it was in a vice and I was ready to call it quits. For the next dive I used the less harsh brass clip and managed to stay down for a complete hour. This time I actually enjoyed the dive and started feeling what the rebreather was doing. The work of breathing is really good, even for a front mounted pendulum rebreather as the swimming position keep you in a slightly heads up stance. The rear harness section curves with the shape of your back and after an hour in the water no back pain was evident. The only real issue is the complete lack of any form of bailout. In the navy, there is a standby diver that can reach the working depth of the diver in case of a problem. There is also a chamber on site for diving operations and divers are trained in “surface decompression” in case the unit floods and they have to come straight up to the surface, having missed their deco obligation. In the works will be some kind of bailout option when I start taking it through Thomas canyon!!!

So the next time any of you are in the Red Sea and are brave enough to have a go, pop in and we will get you looking like Buster Crabb!!

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Comments
  1. ALVIN MIRABAL says:

    Great article! I am very interested in this type of oxygen re breather! Alvin Mirabal

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