Diving rescuers

German diving rescuer from World War II

Exercise of an emergency exit with a Davis diving rescuer in a test tank (1944)

The diving rescuer is a breathing apparatus that enables its wearer to survive for a certain time in an environment without (sufficient) breathable air, especially in water.

Naming

Diving rescuer from U-701

While diving in today's linguistic usage only refers to being under water, this term also included staying in a non- breathable atmosphere until around the middle of the 20th century . Around 1900, for example, a water-cooled fire protection hood with air supply for firefighters was called fire diver and in the 1940s, wearers of breathing apparatus were also known as gas divers .

The diving rescuer was developed from such breathing apparatus and was also found on land, e.g. B. Use in mining . With the increasing spread of diving rescuers as a means of rescue from wrecked submarines and as a light diving device, the importance of the underwater air supply decreased. Occasionally, it was also used to extend the diving time of a submarine when the air supplies were running low, but surfacing was out of the question for technical or military reasons.

functionality

Chemically

Normal breathing air contains 21% oxygen . With one breath , approx. 4% oxygen is withdrawn from the inhaled air and replaced by a corresponding amount of exhaled carbon dioxide (CO ₂ ). In principle, a certain volume of air can be "breathed through" several times until its oxygen content is exhausted, but the exhaled CO ₂ accumulates in the air. Since a healthy organism controls breathing by “measuring” the CO ₂ content in the blood , an increase in the CO ₂ content in the air quickly causes an almost unbearable feeling of shortness of breath . In addition, there are physiological dangers from too much carbon dioxide in the inhaled air: from 5% it leads to unconsciousness , from 8% to death over a longer period of time .

As a result, the accumulating CO _{2 in} the air must be removed from the breathing circuit. For this purpose, the exhaled air flows through soda lime , in which the CO _{2 is} first bound to sodium hydroxide , which is then regenerated by the calcium hydroxide also contained , also known as slaked lime. In the past , freshly burnt lime (CaO) was used in diving rescuers in addition to other hydroxides . This binds the CO ₂ directly, it creates calcium carbonate (CaCO ₃ ) and a lot of heat, which counteracts the cooling in the water . However, there was a risk that water could react violently with the burnt lime, which could lead to severe lung burns. In addition, the quicklime could bind moisture unnoticed and thereby become slaked lime , which alone cannot bind the CO ₂ quickly enough.

The volume of air lost by binding CO ₂ is replaced by supplied oxygen.

For diving rescuers, substances are also used that bind CO ₂ from the breath in a chemical reaction and at the same time release O ₂ . Potassium hyperoxide , for example , has this property , which also binds water vapor from the air we breathe:

${\ displaystyle \ mathrm {4 \ KO_ {2} +4 \ CO_ {2} +2 \ H_ {2} O \ longrightarrow 4 \ KHCO_ {3} +3 \ O_ {2}}}$

Another compound that is used in this context is sodium peroxide :

${\ displaystyle \ mathrm {Na_ {2} O_ {2} + CO_ {2} \ longrightarrow Na_ {2} CO_ {3} +1/2 \ O_ {2}}}$

Technically

The diving rescuer is a so-called pendulum breath , that is, the same air is repeatedly inhaled and exhaled, the cartridge with soda lime and an oxygen supply prevent suffocation.

The person wearing the diving rescuer puts a mouthpiece in his mouth, to which two short hoses are attached. A hose leads into the lime cartridge. Here the CO ₂ is filtered out of the air as you exhale . The remaining air flows further into a breathing bag (counterlung). The volume of the withdrawn CO ₂ is replaced by oxygen from a small high-pressure bottle, as otherwise the volume of the available breathing air would decrease more and more (see above "Chemical functionality"). Now the wearer breathes in again and the air flows back through the second tube from the breathing bag to the mouthpiece. To prevent the wearer from breathing through their nose, they put on a nose clip. The operating time of a diving rescuer was between 15 and 45 minutes, depending on the depth of action.

Use in submarine rescue

If an emergency made it necessary to get out of a submarine, it was initially waited if possible until the water had compressed the air in the boat so much that the pressure in the remaining air bubble corresponded to the pressure of the water depth (see Boyle-Mariotte ). The lower end of the exit shaft had to be lower than the ceiling of the hull so that the air could not escape when the hatch was opened (air trap). The hatch could then be opened when the internal and external pressure were equalized. The crew of the boat could disembark.

The journalist, author and head of the literary department of the Drägerwerk Lübeck Wilhelm Haase-Lampe gave an impression of a diving rescue mission in 1913 :

“Immediately after the accident occurred, the command“ Clear to the rescue team! ”Prompted the crew to equip themselves with the rescue apparatus ... Escape from the wreck is only possible if the pressure difference inside the boat is eliminated. There is no alternative but to let the whole boat fill up. The teams take a deep breath, bring the breathing piece of the 'diving rescuer' to their mouths, open the mouthpiece tap and put on the nose clip. The valve of the oxygen cylinder is opened until the breathing bag is taut on the back. Another 'Hurray!' To the emperor. The last way to save will open up. It's heavy, scary for some, but it's the only one. The bottom valve is loosened and the water gurgling, rustling, rises into the room, laps the feet of those waiting, crawls up their bodies and closes over their heads. What is it! The rescuer oxygen receives them. ... But the light has gone out. The arms touch each other. The right hand is on the valve of the oxygen cylinder, triggering the flow of nutrient gas at intervals; the left includes the valve of the compressed air cylinder in order to paralyze the pressure differences in the apparatus. After a few minutes the room is full of water except for a layer of compressed gases. The companionways are opened ... Man by man emerges from the hatches ... The first strives towards the day with a rapid surge. The air expanding in the ›diving rescuer‹ escapes in a bubbling manner from a finely organized, excellently proven pressure relief valve. ... The person who has emerged has now reached a depth of 15 m, remains there for 2 minutes ... Another 5 minute break in the ascent at a depth of 6 m, and then the ascent to the light and to comrades who are ready to be rescued may be completed. In a vertical swimming position, the liberated float on the surface of the water. ... The swimmer can free himself from the breathing apparatus by using a safely functioning ejection device; the upper body remains covered by the life jacket. ... There can be no doubt that the rescue in the ›diving rescuer‹ requires the highest degree of cold bloodedness and discipline ... "

history

With the development of the first militarily usable submarines shortly before the First World War, the question of rescue options in the event of an accident also arose . The first, often fatal, attempts were made with simple "breathing bags" that were useful as a buoyancy aid, but often did not contain enough oxygen to enable the person appearing to complete the entire ascent .

Robert Henry Davis and Henry A. Fleuss developed from 1903 at Siebe Gorman in England a closed loop breathing apparatus that could be used underwater and in mining; it has been improved in the following years and later as Davis Tauchretter known (ger .: Davis Escape Set). The most important innovations were metering valves for a controlled supply of additional oxygen in 1906, which were also adopted early on by the other companies that manufactured diving rescuers.

The Drägerwerk in Lübeck invented the submarine saver in 1907 . Both systems were based on the principle of oxygen supply from a high-pressure cylinder with simultaneous absorption of the carbon dioxide by an intermediate cartridge with sodium hydroxide .

The Dräger diving rescuer delivered oxygen to the ascent via an oral breathing apparatus for about 30 minutes. Once on the surface of the water, the breathing apparatus could be separated from the life jacket belonging to the diving rescuer . Before and during the First World War, Dräger manufactured two models of the diving rescuer, which were named DM 1 and DM 2. After the sinking of the submarine SM U 3 in the Kiel Bay, the Dräger diving rescuer was offered to the Imperial Navy as a rescue device and was used on German submarines from 1912.

In 1913, Dräger introduced a bath diving rescuer. While the previous devices were only used for surfacing and were therefore also designed to develop buoyancy so that the wearer could reach the surface without swimming movements, the bathing diving rescuer was provided with weights that also made it possible to dive down in order to search for victims and to recover.

In addition to submarine and bathing diving rescuers, from 1913 Dräger also offered diving rescuers for pilots of damaged seaplanes , who could also use them as an oxygen source at high altitudes.

From 1939 onwards, Hans Hass developed the immediate forerunner of today's swim diving equipment based on the diving rescuer.

Further developed forms of the diving rescuer

Modern diving rescuer ( Royal Navy Submarine Museum )

In later developments, the pressure vessels contained a suitable gas mixture instead of oxygen or compressed air. This was automatically dosed via a valve , which enables the use of the diving reserve even at greater depths.

In addition, the devices developed further into the oxygen cycle device , the models of which absorb the CO ₂ formed with each breath and refill the consumed amount of oxygen manually or automatically. Oxygen circulation devices are technically simpler than mixed devices, but their use is biologically limited to shallow diving depths. Oxygen circulation devices are very popular with combat divers and underwater photographers because, unlike a regulator, no bubbles escape that could give the diver away. Another area of application is corporate fire protection, for example in chemical plants or rescue in mining, where long periods of use prohibit the use of compressed air breathing apparatus .

Further developments of the oxygen cycle devices with special, differently complex gas metering and monitoring devices enable the use even at great depths and over longer periods of time; they are used by professional divers , as emergency breathing apparatus and for technical diving .

Today's diving rescuers are combined with life jackets and protective hoods that protect the head and respiratory organs from overflowing water. It is used with thermal protection suits , comparable to the well-known dry suits . The use is nevertheless limited to comparatively shallow depths, life capsules and rescue submarines as well as emergency buoyancy devices and ballast that can be dropped are intended to ensure safety at greater depths.

The German master model of the diving rescuer from the Second World War is still used today, identically constructed, in Leopard 2 tanks as emergency protection during river diving trips.

The escape capsule designs of the space shuttle represented a special form of the diving rescuer . In the spherical, internal pressure-maintaining and insulating textile cover, one astronaut , equipped with a breathing apparatus very similar to the diving rescuer, could survive and through a second astronaut in a space suit through the vacuum to a suitable rescue spacecraft be transported.

Diving rescuer in the film

In the key scene of the submarine film Morgenrot (1932), the crew discusses who should stay on board, since there are too few diving rescuers to enable everyone to escape from the “iron coffin”.

The films show the deployment of diving rescuers:

The boat (four inserts of the "potash cartridges"):

After a fire on board deleted (indirectly caused by depth charges ) Kalipatronen be used for ventilation ( " LI : Ventilate By Kalipatronen")
Johann "the ghost" stops a water ingress under a diesel engine,
The chief engineer works in a chlorine gas atmosphere on bridging destroyed battery cells,
Use of diving rescuers while sleeping in the bunks to save breathing air and to gain time for repairs when you are stuck at a depth of 280 m off Gibraltar

Sharks and small fish (controlled exit from sunken submarine),
U-Boat (protection of breathing air against meningitis ),
U 47 - Kapitänleutnant Prien (save oxygen),
Dawn (controlled exit from sunken submarine in WW I. Two diving rescuers too few to save all crew members)
The Wolf's Call - decision in the depths (controlled exit from a sinking submarine).

literature

Hermann Stelzner: diving technique - manual for divers / textbook for diver aspirants. Charles Coleman Publishing House, Lübeck 1943
Michael Seydel: The history of development and use of the diving rescuers of the Drägerwerk Dissertation University of Lübeck 2010
Michael Kamp: Bernhard Dräger: inventor, entrepreneur, citizen. 1870 to 1928. Wachholtz Verlag GmbH, 2017, ISBN 978-3-52906-369-5 .

Web links

Wiktionary: Tauchretter - explanations of meanings, word origins, synonyms, translations

The history of development and use of the Drägerwerk's diving rescuers

Individual evidence

^ Michael Kamp : Bernhard Dräger : Inventor, Entrepreneur, Citizen. 1870 to 1928. Wachholtz Verlag GmbH, 2017, ISBN 978-3-52906-369-5 , p. 300 f.
^ Michael Kamp: Bernhard Dräger: Inventor, Entrepreneur, Citizen. 1870 to 1928. Wachholtz Verlag GmbH, 2017, ISBN 978-3-52906-369-5 , pp. 298-301.
^ Michael Kamp: Bernhard Dräger: Inventor, Entrepreneur, Citizen. 1870 to 1928. Wachholtz Verlag GmbH, 2017, ISBN 978-3-52906-369-5 , p. 301.
^ Michael Kamp: Bernhard Dräger: Inventor, Entrepreneur, Citizen. 1870 to 1928. Wachholtz Verlag GmbH, 2017, ISBN 978-3-52906-369-5 , pp. 301 f.

[1] Michael Kamp : Bernhard Dräger : Inventor, Entrepreneur, Citizen. 1870 to 1928. Wachholtz Verlag GmbH, 2017, ISBN 978-3-52906-369-5 , p. 300 f.

[2] Michael Kamp: Bernhard Dräger: Inventor, Entrepreneur, Citizen. 1870 to 1928. Wachholtz Verlag GmbH, 2017, ISBN 978-3-52906-369-5 , pp. 298-301.

[3] Michael Kamp: Bernhard Dräger: Inventor, Entrepreneur, Citizen. 1870 to 1928. Wachholtz Verlag GmbH, 2017, ISBN 978-3-52906-369-5 , p. 301.

[4] Michael Kamp: Bernhard Dräger: Inventor, Entrepreneur, Citizen. 1870 to 1928. Wachholtz Verlag GmbH, 2017, ISBN 978-3-52906-369-5 , pp. 301 f.