 A Davis Submerged Escape Apparatus | |
| Acronym | DSEA |
|---|---|
| Uses | Oxygenrebreather for submarine emergency escape and diving |
| Inventor | Sir Robert Davis, 1910 |
| Related items | Escape set |
TheDavis Submerged Escape Apparatus (also referred to asDSEA), was an early type ofoxygenrebreather invented in 1910 bySir Robert Davis, head ofSiebe Gorman and Co. Ltd., inspired by the earlierFleuss system,[1][2] and adopted by theRoyal Navy after further development by Davis in 1927. While intended primarily as an emergency escape apparatus forsubmarine crews, it was soon also used fordiving, being a handy shallow water diving apparatus with a thirty-minute endurance,[2] and as anindustrial breathing set.
The DSEA rig chiefly addressed the problem ofanoxia threatening a person ascending through water, by providing oxygen; and the associated risk oflung over-pressure injury as underwater pressure reduces with reducing depth, which it addressed by managing oxygen pressures. It also provided assistance with buoyancy, both in the ascent and after reaching the surface. The risk ofdecompression illness due to ascending too fast could be addressed by associated equipment; any other escape requirements, such as means of summoning help once the surface was reached, were not considered.
The apparatus itself comprises a rubber breathing/buoyancy bag, which contains a canister ofbarium hydroxide to scrub exhaledCO2 and, in a pocket at the lower end of the bag, a steel pressure cylinder holding approximately 56 litres ofoxygen at a pressure of 120 bar. The cylinder is equipped with a control valve and is connected to thebreathing bag. Opening the cylinder's valve admits oxygen to the bag and charges it to the pressure of the surrounding water.
The canister of CO2 absorbent inside the breathing bag is connected to a mouthpiece by a flexible corrugated tube; breathing is through the mouth only, the nose being closed by a clip. Goggles are also provided as a standard part of the apparatus.
The breathing/buoyancy bag is fitted with a non-return release valve which allows air to escape from the bag as the user ascends towards the surface and the water pressure decreases. The wearer can close this valve on reaching the surface, the air in the breathing/buoyancy bag then serving as a life preserver. If the bag becomes deflated while the wearer is on the surface awaiting rescue, it can be refilled (for use as alifejacket) by opening the non-return valve and blowing through the mouthpiece.
The usualRoyal Navy DSEA rig also included an emergency buoyancy bag on the front of the main breathing/buoyancy bag to help keep the wearer afloat after reaching the surface even if he had exhausted the air in the breathing/buoyancy bag. This emergency bag was inflated by an "Oxylet" canister inside it - a small steel oxygen cylinder which was opened by breaking its weakened neck and wrenching sharply.[citation needed]
It also had a speed-retardingdrogue, which was a rubber apron unrolled and held out horizontally by the wearer as he ascended, dramatically reducing his speed of ascent through water resistance to avoiddecompression illness.
Adopted by the Royal Navy in 1929, DSEA was used with limited success to assist crew members to escape from several sunken submarines, for exampleHMSPoseidon in 1931,[3]HMSThetis in 1939[4] andHMSPerseus in 1941.[5]
A small version of the DSEA, theAmphibious Tank Escape Apparatus (ATEA) was produced for use by the crews of amphibiousDD tanks such as those used during theNormandy landings.
There were instances, mostly duringWWII, of the DSEA being used for swimming down from the surface, i.e. for earlyscuba diving. In WWII it was also notably used by the Underwater Working Party at Gibraltar led by Lt.Lionel "Buster" Crabb, and worn at times by frogmen piloting 'Sleeping Beauty'Motorised Submersible Canoes.[citation needed]
