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Russian special forces will receive a double-medium breathing apparatus. Closed-circuit breathing apparatus ap "alpha" Closed-circuit diving apparatus for diving

The enemy will not pass! Even underwater


Operation diagram and controls of the “Inspiration” rebreather

Nevertheless, the scale of the tasks he performed was enormous. On Day X, Soviet naval special forces were supposed to land from numerous submarines, airplanes, helicopters, and from commercial and fishing ships under foreign flags. Black ghosts that suddenly appeared from under the water were supposed to disable the entire anti-submarine defense system in the Atlantic, Pacific Ocean and the Mediterranean Sea, destroy the control and communications centers of NATO naval formations, blockade forward bases, capture important strategic objects and hold them until the main landing. Naval special forces prepared very seriously, participating in numerous military operations around the world - Angola, Vietnam, Egypt, Nicaragua, Ethiopia, making “cruises” to foreign ports for reconnaissance purposes and constantly training on ships of the USSR Academy of Sciences and in secret compartments of floating fish canneries. factories. According to NATO, Soviet underwater special forces illegally landed on the coasts of Sweden and Norway alone more than 150 times. Most of the attacks went unnoticed. The saboteurs left no traces behind them. Even something as ephemeral as water bubbles.

Footprints on the water

Bubbles in the water are the first thing that attracts the eye of an outside observer when he watches amateur scuba diving. No bubbles - warning sign and is usually accompanied by active efforts to prepare and initiate a rescue operation. However, there is one exception - diving with rebreathers. A diver with a rebreather in the water is practically silent, like the inhabitants of the underwater kingdom - he does not release gurgling bubbles, and waterfowl take him as “one of their own”.

Widespread

As the main equipment for diving, the scuba gear designed by Cousteau-Gagnan is an open-circuit breathing apparatus: the diver inhales air from a cylinder and exhales it into the water. At the same time, the inhaled air contains 21% oxygen, and the exhaled air contains about 16% (at normal atmospheric pressure, that is, on the surface of the water). Thus, most of the air is simply wasted. If the exhaled air is cleaned of carbon dioxide and enriched with oxygen, it can be reused. This is done by chemical absorbers and the addition of small portions of oxygen (in general, with increasing depth, the need for oxygen decreases due to an increase in its partial pressure). Partial pressure is the pressure that a component of a gas mixture would exert if it alone occupied the volume of the entire mixture.

A little history

Closed or semi-closed cycle breathing apparatus - rebreathers - are based on these principles. Don't think that this is an achievement modern technologies. The first rebreather was developed by the Englishman Henry Fleuss back in 1876. The Fleuss rebreather consisted of a rubberized fabric shell, a breathing bag, and a copper cylinder with oxygen and a carbon dioxide absorber. Hemp soaked in caustic soda (sodium hydroxide) was used as an absorber. If necessary, oxygen was added manually. Although this device now seems primitive, for those times it worked quite well, allowing you to spend up to 3 hours under water. The depth of the dive with the Fleuss apparatus was limited due to the use of pure oxygen (pure oxygen is toxic even when diving to 5-7 m, but this fact was not known at that time). However, in 1880, the famous English diver Alexander Lambert dived in Fleuss's apparatus to seal a hatch in a flooded tunnel. The hatch was located 300 m from the entrance to the tunnel at a depth of 20 m!

In 1907 German company Draeger introduced a rebreather to rescue people from sinking submarines. This rebreather, like the Fleuss apparatus, largely served as the basis for the development in 1911 by the Englishman Robert Davis, director of the Siebe Gorman company, of a device of his own design, called the “Davis False Lung”. In 1915, the crew of the first underwater film, based on Jules Verne’s book “Twenty Thousand Leagues Under the Sea,” used modified Fleuss-Davis rebreathers during filming.

With the outbreak of World War II, the need for covert underwater operations emerged and rebreathers firmly occupied a leading place among the underwater equipment of the navies of many countries.

In 1968, Dr. Walter Stark develops the Electrolung, the first breathing apparatus. closed loop, controlled electronically. This was a qualitative step forward in technology, which until then had remained traditional and was based on mechanical dosing of gases.

Until the mid-1990s, the main users of rebreathers were the military, researchers and professional divers. The military appreciated stealth and noiselessness in closed-circuit devices (the presence of combat divers is not indicated by bubbles), and non-magneticity (the rebreather can be made of non-magnetic materials). Researchers underwater world— absence of bubbles (the inhabitants of the underwater world are not afraid, they are easier to photograph and study). Rebreathers gave divers the opportunity to dive to greater depths and spend more time there, increasing their work efficiency.

Since the mid-1990s, rebreathers using gas mixtures began to slowly conquer the recreational diving market. There are now quite a few models of rebreathers for amateur diving, and although their cost is quite high (from $2-5 thousand for semi-closed systems to $8-15 thousand for closed-circuit systems), they are becoming increasingly popular.

Closed breathing system

Breathe-helping machine A completely closed cycle consists of two small cylinders and a carbon dioxide absorption system. One cylinder contains oxygen, the second contains diluent gas. There are systems that operate on pure oxygen (without diluent), but the diving depth with them is limited to 5-7 m (due to the toxicity of pure oxygen), mainly the old military systems.

Sodium hydroxide (caustic soda) or calcium hydroxide (caustic soda) are usually used as absorbents. slaked lime), or a mixture of them. The exhaled air is passed through the absorber and enters the breathing bag (counterlung - counterlung). Inhalation is carried out from the breathing bag. Sometimes it is divided into two parts - for inhalation and exhalation. Pressure sensors and oxygen and carbon dioxide content give signals electronic system, which, using solenoid valves, adds oxygen and diluent gas if necessary (the control system tries to maintain the partial pressure of oxygen within safe limits in all conditions).

If necessary, you can manually supply oxygen from one cylinder or diluent gas from another. Depending on the task at hand, air, nitrox (a mixture of oxygen and nitrogen with more than 21% oxygen content), or special mixtures can be used as a diluent gas (for example, for ultra-deep diving they use Trimix (“trimix”) - a mixture consisting of helium, nitrogen and low oxygen content).

The closed loop system does not release any bubbles when kept at a constant depth. As the depth decreases, the volume of the breathing mixture in the breathing bag increases and the excess is released through the valve. As the depth increases, the breathing bag is automatically or manually refilled with diluent gas to maintain a constant volume.

Semi-closed breathing system

It differs from a closed one in the presence of only one cylinder with a breathing mixture. Typically, nitrox is used as such a mixture (a mixture of oxygen and nitrogen with an oxygen content greater than 21%). To compensate for oxygen consumption (nitrogen is not consumed during breathing), in semi-closed systems, part of the mixture is released into water when exhaling (up to 25% of the exhalation volume). To reduce noise, before release, the mixture is passed through a special filter, which “splits” the bubbles into smaller ones and disperses them behind the diver’s back.

Reliability

Failure of any rebreather component underwater can result in the death of the diver. Therefore, manufacturers take all possible measures to increase their reliability. Sensors, indicators and solenoid valves are duplicated many times. In addition, the rebreather usually has an independent emergency system in case of complete failure. The emergency system is usually an open-cycle apparatus (more precisely, a reducer-regulator) connected to a rebreather cylinder with a respiratory mixture or an independent small cylinder. This allows the diver to complete refusal or a rebreather accident float to the surface.

Advantages

The first main advantage of a rebreather is its long dive time. One charge of the rebreather is enough, depending on the model, diving depth and breathing intensity, for 2-5 hours of diving.

Rebreathers also significantly increase no-decompression limits. Some of the more sophisticated closed oxygen-controlled systems can even optimize the breathing oxygen content of the gas mixture according to the dive profile.

Another advantage of rebreathers is heat and moisture retention. In systems with an open breathing circuit, especially in conditions cold water, heat is consumed to warm the inhaled air and enrich it with water vapor. In rebreathers, when carbon dioxide is absorbed, heat is released. Since exhalation does not occur into the water, heat and water vapor are maintained within a closed cycle.

As mentioned above, rebreathers produce significantly less noise and bubbles, which allows you to get closer to even the most timid inhabitants of the deep sea and observe their life (with conventional scuba gear this is often simply impossible).

Flaws

The benefits of rebreathers come at a high price. First of all, in the literal sense of the word. The cost of semi-closed systems ranges from $2 to $8 thousand, completely closed - from $8 to $15 thousand. And there is little hope that they will become cheaper in the near future.

Rebreathers require regular Maintenance after each dive - more or less simple for semi-closed systems (checking and replacing the carbon dioxide absorber, cleaning hoses) and more complex for closed ones. Electronic oxygen partial pressure sensors must be checked regularly and periodically calibrated.

Training in rebreather swimming is also still in its infancy, although the situation is changing quite quickly. All manufacturers of such devices have their own preparation requirements. There are currently 4 organizations (IANTD, TDI, PSA, ANDI) that have standardized training courses. Now closed-cycle devices are quite accessible. After several hours of instruction, you can make just one dive or take a full deep-sea course with certification (3-7 days, $500-1500, the cost of training is often included in the price of the device).

An underwater breathing apparatus belongs to the field of diving technology, namely underwater breathing apparatus, and can be used during diving descents, underwater rescue operations, and underwater technical work. The purpose of the utility model is to expand the possibilities of using an open-circuit underwater breathing apparatus, increase the safety of diving descents, simplify the conversion of the underwater breathing apparatus and, as a result, reduce its cost. The technical result from the use of the utility model is the mobility of the placement of the absorption cartridge and cylinders in the design of an open-circuit underwater breathing apparatus.


The utility model relates to the field of diving technology, namely underwater breathing apparatus, and can be used when carrying out diving descents, underwater rescue operations, and underwater technical work.

An open-circuit underwater breathing apparatus is known (Underwater Diver's Memo. Resource "Black Sea Swimmer's Library" http://divinginfo.narod.ru/library/Rukovodstvo_dlia_plovtsov_kmas.doc), which includes a cylinder with a locking device, a reducer that reduces the pressure of the gas mixture in balloon; the main design elements of this device are modular in nature and, as a result, can be placed in various places provisions necessary for specific task for underwater descents, namely, they can be placed on the back, side or chest of the diver, and can also be attached to the main breathing apparatus as a reserve. This device is accepted as the closest analogue of the claimed utility model. The disadvantage of the device is that it has a short protective action time due to the open breathing cycle.

Known underwater closed-circuit breathing apparatus APDiving Vision (Inspiration. Closed Circuit Rebreather. User Instruction Manual. http://www.apdiving.com/, http://www.smrebreathers.ru/rebreathers/review/Inspiration_Evolution.htm), containing cylinders with shut-off devices, a reducer, a suspension system, an absorption cartridge, a housing, a valve box, breathing bags, a buoyancy compensation tank, a spare lung demand valve, and an external pressure gauge. The advantages of this device include: high physiology - a diver, breathing from this device with a moist, warm, oxygenated gas mixture, gets tired, cold and dehydrated much less than a diver in similar conditions, breathing from an open-circuit apparatus with cold, dry air; longer protective action time with comparable underwater vehicles open cycle breathing size and weight; reducing the cost of descents by saving expensive gas mixtures; increasing the no-decompression limit; ensuring the possibility of conducting deep-sea autonomous diving descents; ensuring high dive secrecy necessary to perform military missions.

The disadvantage of this device is the location of the absorption cartridge and cylinders by fixing them in a rigid body, which is specified during the manufacture of the device. The rigid body makes it impossible to use cylinders with dimensions larger than those used in the standard configuration of the device. Thus, the design of the apparatus cannot be changed by the user to provide specific conditions for the diving descent.

Analysis of known patented solutions revealed the developer’s desire to increase the autonomy of the device (patent for invention No. SU 1722222 dated July 23, 1986), improve the characteristics of regenerative substances in a diving breathing apparatus (patent for invention No. RU 2225322 dated 30.08.2001), to increasing the safety of using a closed-cycle device due to the number of regenerative cartridges included in its composition (patent No. RU 2302973 dated December 31, 2002), improving control of the formation of the respiratory mixture entering the device (patent No. RU 2236983 dated 11.04. 2002), simplifying the procedure for reloading a regenerative product (patent for invention No. RU 2254263 dated 05/07/2004).

The purpose of the utility model is to expand the possibilities of using an open-circuit underwater breathing apparatus, increase the safety of diving descents, simplify the conversion of the underwater breathing apparatus and, as a result, reduce its cost.

The technical result from the use of the utility model is the mobility of the placement of the absorption cartridge and cylinders in the design of an open-circuit underwater breathing apparatus.

Also, the technical result is to provide mechanical and thermal protection for the absorption cartridge used in the design of the underwater breathing apparatus.

The problem is solved using the design of an underwater breathing apparatus of an open breathing cycle, containing a cylinder with a locking device, a reducer, characterized in that it contains an absorption cartridge, at least one, a breathing bag, a valve box, and low-pressure connecting hoses.

The problem is also solved by the fact that the device contains a cover for the absorption cartridge.

The problem is also solved by placing the cylinder on the cover of the absorption cartridge.

The problem is also solved by the fact that the device contains belts for fastening the cylinders, a sling, clamps that attract the sling to the cartridge body, and straps on the breathing bags.

The problem is also solved by the fact that the device contains a pulmonary valve.

The problem is also solved by the fact that the device contains a suspension system.

The problem is also solved by placing an absorption cartridge on the suspension system.

The problem is also solved by the fact that the device contains a pressure gauge.

The problem is also solved by the fact that the device contains a buoyancy compensator capacity.

The problem is also solved by placing an absorption cartridge at the location of the cylinder.

The problem is also solved by placing an absorption cartridge on the cylinder.

The problem is also solved by placing the absorption cartridge on the side of the cylinder.

Proposed utility model illustrated by the following drawings:

Fig.1 General scheme underwater breathing apparatus;

Figure 2 Underwater breathing apparatus using a cover;

Figure 3 Underwater breathing apparatus using a sling and clamps.

The underwater breathing apparatus consists of the following components and parts:

Suspension system 1, designed for mounting the apparatus components on it and attaching it to the diver’s body;

Valve box 2 with corrugated inhalation and exhalation hoses - providing the ability to breathe the gas mixture from the device, as well as atmospheric air when on the surface;

A set of breathing bags: inhalation 3 - to supply the required volume of the gas mixture during inhalation used for breathing by the diver, exhalation 4 - to collect exhaled air;

Cylinder with a shut-off device 5 or two cylinders with shut-off devices designed to hold a supply of gas mixtures;

Reducer 6 - to reduce the pressure of the respiratory mixture coming from the cylinder;

Buoyancy compensator, “wing” 7, designed to compensate for the negative buoyancy of the diver, both at the time of immersion and while on the surface;

A lung demand valve with a hose 8 - for the diver to breathe directly from the apparatus cylinder in an emergency;

Remote pressure gauge 9 - for visual monitoring of the pressure of the gas mixture in the cylinder;

Oxygen indicator 10 - for visual monitoring of oxygen partial pressure;

Absorption cartridge 11 - for cleaning exhaled gas from CO2 contained in it;

12 hoses for inhalation and exhalation of the cartridge;

T-connectors 13;

Inflator hose 14;

Inhalation bag inflating hose 15;

Exhalation bag inflator hose 16;

Gas supply hose from the reducer to the manifold 17;

Hose for supplying breathing mixture to cartridge 18;

Belts 19;

Covers 20 (for versions with a cover).

To place the absorption cartridge 11 on the diver's back, it is secured to the buoyancy compensator 7, the standard compensator straps are threaded through the loops on the side surface of the cover 20 so that the cartridge is pulled in similarly to the cylinder of an apparatus with an open breathing circuit. Unlike the latter, thanks to the presence of the cover, there is no need to attract the cartridge with a force similar to the force required to securely fasten the cylinder - thanks to the presence of loops, the absorption cartridge is securely fastened.

To fix the small-volume cylinder 5 to the absorption cartridge 11, mounted on the buoyancy compensator, straps for attaching cylinders are threaded into the loops of the absorption cartridge cover, which cover the small-volume cylinder so that the absorption cartridge remains outside the belt loop.

To secure the absorbent cartridge to a cylinder with a breathing mixture, located either on the buoyancy compensator on the diver's back or on the side suspension, straps of the same type are used as for securing the cylinder to the buoyancy compensator. To do this, the belts are threaded through the loops of the absorption cartridge cover so that they cover the cylinder to which the cartridge will be attached, and the cartridge itself remains outside the belt loop.

To directly secure the absorption cartridge on the side suspension, carabiners are tied to the loops of the cover using ropes, which are attached to the buoyancy compensator attachment points.

The absorbent cartridge case consists of a fabric bag, the dimensions of which exactly correspond to the dimensions of the absorbent cartridge and elements that ensure its docking with other elements of equipment. The neck of the bag, through which the cartridge is inserted inside, has a device for tightening, consisting of a rope and a clamp. To securely fix the cartridge inside the case, the neck of the case also has straps with locks.

For fastening to other elements of equipment, the cover of the absorption cartridge has loops made of slings on the side and bottom end surfaces (the bottom of the “bag”).

To transfer the device from an open cycle to a closed or semi-closed breathing cycle, without using a special cover in the design of the device, three steel clamps are located on the absorption cartridge 11, attracting the sling to the cartridge body, so that it forms two loops into which there can be The cylinder fastening straps are threaded. On the covers of the breathing bags 3 there are several pairs of straps with fastenings for encircling the shoulder straps of the suspension system of the open-circuit apparatus. A sling with fastex buckles ensures tight fixation of the breathing bags on the diver’s body.

The absorption cartridge is attached to the apparatus in two ways:

Installing the cartridge on the side of the back balloon. This is achieved by threading the balloon belts of the suspension system into the loops on the absorption cartridge;

Installing the cartridge in place of the back balloon. In this case, the cylinder belts are also threaded through the loops, but the belts cover the cartridge, similar to how this is done when installing a cylinder.

Offered as a utility model technical solution, used in the design of an underwater breathing apparatus, allows you to place the absorption cartridge of the apparatus in various places of the equipment, namely:

On the diver’s back, by fixing it on the buoyancy compensator;

On the diver’s back or on a side sling, when fixed to a cylinder with a breathing mixture;

On the side of the diver, by attaching the buoyancy compensator directly to the mounting components of the suspension system.

In addition, when using lightweight fabric materials, the solution makes it possible to attach small-volume cylinders directly to the cover of the absorption cartridge, reducing the size and weight of the connecting unit of the device, and providing mechanical and thermal protection of the absorption cartridge.

The ability to convert open-cycle devices to closed and semi-closed cycles increases the protective action time of the device, while to perform simple tasks it is possible to transfer the device back to open-cycle operation by removing the expansion module.

Breathing apparatus manufactured by JSC KAMPO were manufactured and put into operation, in which the technical solution claimed as a utility model is implemented. The device can be manufactured in serial machine-building production using equipment general use without additional capital investments.


Utility model formula

1. An open-circuit underwater breathing apparatus containing a cylinder with a shut-off device, a reducer, characterized in that it contains an absorption cartridge, at least one breathing bag, a valve box, and low-pressure connecting hoses.

2. The device according to claim 1, characterized in that it contains a cover for the absorption cartridge.

3. The device according to claim 2, characterized in that the cylinder is placed on the cover of the absorption cartridge.

4. The device according to claim 1, characterized in that it contains belts for fastening cylinders, a sling, clamps that attract the sling to the cartridge body, straps on breathing bags.

5. The device according to claim 1, characterized in that it contains a buoyancy compensator tank.

6. The device according to claim 1, characterized in that it contains a lung demand valve.

7. The device according to claim 1, characterized in that it contains a suspension system.

8. The device according to claim 7, characterized in that the absorption cartridge is placed on the suspension system.

9. The device according to claim 1, characterized in that it contains a pressure gauge.

10. The device according to claim 1, characterized in that the absorption cartridge is placed on the cylinder.

11. The device according to claim 1, characterized in that the absorption cartridge is placed at the location of the cylinder.

12. The device according to claim 1, characterized in that the absorption cartridge is located on the side of the cylinder.

Self-contained breathing apparatus IDA-59M(Fig. 9) is a self-contained breathing apparatus of a regenerative type with a closed breathing cycle. The device isolates the submariner’s respiratory organs from environment and is designed to ensure the submariner’s breathing when exiting the submarine, as well as to temporarily support life in the emergency compartments. The main components of the IDA-59M apparatus are shown in Fig. 9:

1. Bib 1 with a sewn lower brace 6 and a waist belt 16.

3. Nitrogen-helium-oxygen cylinder 3 with a reducer 5 and a cross 4.

4. Oxygen cylinder 14 with reducer 13 and switch 12.

5. Valve box 9 with corrugated inhalation and exhalation tubes.

6. Ring breathing bag 10, on which the breathing machine 8 and safety valve 11 are located.

A breastplate with a waist belt and a lower brace is used to mount the apparatus components and secure them to the submariner’s body. Regenerative cartridge (Fig. 10). Its double-walled body holds 1.7…1.8 kg of granular regenerative substance O-3. On top cover there are fittings 1, 2 for connection to the breathing bag, on the bottom there is a charging fitting with a cap nut 8. The bottoms of the inner housing 6 are equipped with grids 3, 7. Ring shelves 5 prevent the passage of the exhaled mixture along the walls of the cartridge. The exhaled gas mixture enters the cartridge through exhalation fitting 2, passes through grille 3 through a layer of substance O-3, where it is freed from carbon dioxide and enriched with oxygen, then through the lower grille 7 enters the gap between the inner and outer walls and then through inhalation fitting 1 into the breathing bag. A nitrogen-helium-oxygen cylinder (Fig. 9) with a capacity of 1 liter is used to store an artificially prepared gas mixture containing 60% nitrogen, 15% helium and 25% oxygen at a pressure of 180...200 kgf/cm2 (during training descents, a pressure of at least 100 kgf/cm2). The cylinder has a three-color color: black with the letter “A” (nitrogen), brown with the letter “G” (helium) and blue with the letter “K” (oxygen). A reducer 5 and a cross 4 are connected to the cylinder using threaded connections. The nitrogen-helium-oxygen reducer 5 is designed to reduce the pressure of the nitrogen-helium-oxygen mixture located in the cylinder to a pressure of 5.3 ¸ 6.6 kgf/cm2 greater than ambient pressure.


Rice. 9. Self-contained breathing apparatus IDA-59M

1 – bib; 2 – regenerative cartridge; 3 – nitrogen-helium-oxygen cylinder; 4 – cross; 5 – gearbox; 6 – shoulder strap; 7 – belt with carabiner; 8 – breathing machine; 9 – valve box; 10 – breathing bag; 11 – safety valve; 12 – switch; 13 -gearbox; 14 – oxygen cylinder; 15 – carabiner; 16 – waist belt

Fig. 10. Regenerative cartridge

1 – inhalation fitting; 2 – exhalation fitting; 3, 7 – gratings; 4 – outer casing; 5 – ring shelf; 6 – inner body; 8 – cap nut

Nitrogen-helium-oxygen reducer

The nitrogen-helium-oxygen reducer consists of a shut-off valve and a reducer housed in one housing. A low torque shut-off valve opens by rotating counterclockwise and closes clockwise. There are two fittings on the gearbox housing: fitting high pressure, closed with a cap nut and used to charge the AGK cylinder with the mixture, and a low pressure fitting, which is connected to the connecting tube of the breathing machine. The gearbox works as follows (Fig. 17). Through the open valve valve, the gas mixture from the AGK cylinder enters under the reducer valve and through the hole in the valve seat fills the low-pressure chamber 2. The reducer chamber is closed from above with a rubber membrane 6, above which an adjusting spring 7 and a metal cap with holes are placed. As the low-pressure chamber is filled, the rubber membrane 6 bends and compresses the adjusting spring 7, releasing the valve pusher, which in turn allows the gearbox valve 3 to move upward under the action of the spring until the hole in the gearbox valve seat is completely closed. The flow of gas into the low pressure chamber stops if the gas from the low pressure chamber is not consumed. When the gas flows out, the membrane 6 bends down, the valve 3 of the reducer, under the action of the pusher, opens again and passes the gas into the low-pressure chamber. From the low-pressure chamber, through the channel and filter, the gas enters the crosspiece 1. The crosspiece serves to connect the low-pressure chamber of the nitrogen-helium-oxygen reducer with the starter 4 DGB and the breathing (pulmonary) machine 13, for which a connecting tube of the breathing machine and a hose are attached to the crosspiece 10 with bayonet lock nipple 9 from DGB (see Fig. 16). In one of the fittings of the cross there is a safety valve that bleeds the nitrogen-helium-oxygen mixture from the low pressure chamber of the AGK reducer at a pressure of 14...17 kgf/cm2 more than the ambient one. An oxygen cylinder with a capacity of 1 liter is used to store medical oxygen (99%, no more than 1% nitrogen) at a pressure of 180...200 kgf/cm2 (during training descents, a pressure of at least 100 kgf/cm2 is allowed). The cylinder has a reducer 23 with a shut-off valve and a switch 20 (see Fig. 17). The oxygen reducer is similar in design to the nitrogen-helium-oxygen reducer, but unlike it, it has a sealed cap. Therefore, under the cap at any depth it is preserved Atmosphere pressure in 1 kgf/cm2. In this regard, the pressure in the low pressure chamber of the oxygen reducer also remains constant - 5.5 ¸ 6.5 kgf/cm2 - during the entire period of operation of the reducer and does not depend on the ambient pressure. At a depth of 55...65 m, when the ambient pressure becomes equal to the pressure in the reducer chamber, the flow of oxygen into the breathing bag completely stops.

The valve box (Fig. 11) with corrugated inhalation and exhalation tubes is used for:

– connecting the breathing apparatus to the diving suit;

– ensuring circulation of the gas mixture in the apparatus in a closed cycle during breathing;

– to switch on breathing into the apparatus and switch to breathing into the atmosphere.

The valve box consists of a body, mica valves for inhalation 5 and exhalation 3, pressed by springs, and a plug valve 8.


Fig. 11. Valve box:

1 – exhalation pipe; 2 – valve guide; 3 – exhalation valve; 4 – gasket; 5 – inhalation valve; 6 – inhalation pipe; 7 – fitting; 8 – plug valve

The valve box is connected to the breathing bag by an inhalation tube with pipe 6, and by an exhalation tube with pipe 1 with a regenerative cartridge. When you inhale, a vacuum is created in the valve box, as a result of which the exhalation valve 3 closes, and the inhalation valve 5 opens and the respiratory mixture enters the lungs. When you exhale, the pressure in the valve box increases, the inhalation valve 5 closes, and the exhalation valve 3 opens and passes the exhaled gas mixture into the regenerative cartridge. Using plug valve 8, the device is switched on (the valve handle is turned towards the oxygen cylinder) or switched to breathing into the atmosphere (the valve handle is turned towards the AGK cylinder). The valve box has a fitting 7 for connection to a mask with an intercom or SGP-K wetsuit using a union nut.

The breathing bag (Fig. 12) has a ring shape and is made in the form of a collar that fits the submariner’s neck. This shape of the breathing bag improves stability, which is especially important during free ascent, and supports the diver’s head above the surface of the water after ascent. The capacity of the breathing bag is 6…8 liters. It is made of soft rubberized fabric and is attached to the bib using belt loops. In the upper part of the breathing bag (on the back wall) there is an automatic starter (breathing machine) 3. In the lower part there are corrugated exhalation tubes 5 and inhalation 1, a safety valve 6, two fittings 8 with union nuts for connecting a regenerative cartridge, fittings 7 and 9 for connecting oxygen and nitrogen-helium-oxygen cylinders. Inside the bag there is a tee 10 connecting the inhalation tube 1 with a piece of tube from the regenerative cartridge and the breathing tube 4, which has side holes along its entire length. These holes ensure that the gas mixture is inhaled from the bag in any position of the submariner. Connecting tube 2 supplies the gas mixture from the AGC cylinder under the valve of the breathing machine. The breathing machine (automatic starter) (Fig. 13) provides automatic replenishment of the breathing bag with a nitrogen-helium-oxygen mixture during immersion or equalization of pressure with the surrounding pressure in the volume necessary for the submariner’s breathing.

Rice. 12. Breathing bag:

1 – inhalation tube; 2 – connecting tube; 3 – breathing machine; 4 – breathing tube; 5 – exhalation tube; 6 – safety valve; 7, 8, 9 – fittings; 10 – tee

The internal cavity of the breathing machine is isolated from the environment by an elastic membrane 1, pressed to the body by a protective cover 2 with a threaded ring 3. The gas mixture through fitting 6 with filter 7 is supplied to valve 5, which is pressed to the seat by spring 8. The force on the valve stem is transmitted by levers 11 and 12, the height of which is adjusted by screw 4 and nut 13. The opening force is adjusted by screw 9, which compresses spring 10. The gas mixture enters the breathing bag through cutouts in the bottom of the housing. The breathing machine bypasses the gas mixture when the vacuum in the bag is 110...160 mm water column. The safety valve (Fig. 14) ensures the release of excess gas mixture from the breathing bag of the apparatus both during its use and during storage on a submarine.

Fig. 13. Breathing machine:

1– membrane; 2 – cover; 3 – threaded ring; 4, 9 – screws; 5 – valve; 6 – fitting; 7 – filter; 8, 10 – springs; 11, 12 – levers; 13 – nut

Fig. 14. Safety valve

1 – cover; 2, 3 – springs; 4 – rod; 5 – valve-membrane; 6 – check valve; 7 – body; 8, 9 – nuts

It is installed in the lower part of the breathing bag and secured with a union nut 8. Structurally, it is a combination of two valves: the main one - the membrane valve 5 and the rubber check valve 6. When the pressure in the breathing bag increases, the membrane 5, overcoming the forces of springs 2, 3, moves away from the seat and opens the exit of the excess gas mixture through the side holes in the housing 7. The submariner’s breathing in the apparatus (see Fig. 9) is carried out through the valve box 9, which is connected to the helmet nipple of the SGP-K diving suit. The composition of gases in the breathing bag 10 necessary for breathing is ensured by the absorption of carbon dioxide and the release of oxygen chemical regenerative cartridge 2, oxygen supply through oxygen switch 12, as well as supply of nitrogen-helium-oxygen mixture through lung demand valve 8. All components of the IDA-59M apparatus are mounted on the bib 1, with the help of which the apparatus is secured to the submariner’s torso over the SGP-K diving suit. A belt with a carbine 7 is attached to the chest strap 6 of the bib, which serves to hold the submariner in the submarine hatch during the locking process when exiting by free ascent through rescue hatches equipped with an air supply unit. The carabiner of apparatus 15 is designed to hold the submariner when exiting the submarine on a buoy rope near the musing. The carbine belt 15 is attached to the waist belt 16 of the device. Using the crosspiece fitting 4, the IDA-59M device is connected to the DGB (see Fig. 16). First, the cap nut is unscrewed from the fitting.

The apparatus includes a mask (Fig. 15), intended for use of the IDA-59M apparatus without SGP-K diving suit in dry and partially flooded compartments of a submarine. The mask allows you to breathe in the device and provides isolation of the respiratory organs and eyes from the surrounding gas or aqueous environment.


Rice. 15. Mask:

1 – straps; 2 – glasses; 3 – intercom; 4 – square; 5 – union nut; 6 – gasket

Using an angle 4 and a union nut 5 with a gasket 6, the mask is attached to the valve box of the device. To fasten and tightly fit the mask along the contour of the face, it has straps 1, which allow you to adjust the mask to the size of your head. The mask is available in three sizes:

1 – small,

2 – average,

3 – big.

An additional helium balloon (Fig. 16) is used in conjunction with the IDA-59M apparatus to allow submariners to exit from depths of more than 100 m while providing forces. Navy Search and Rescue Service. DGB cylinders are supplied assembled with a reducer, starter, connecting hoses and fittings. The helium cylinder 1 is enclosed in a case 7. In the pocket 6 of the case there is a starter connected by a hose 5 to a tee 3 of the gearbox. Hose 10 with bayonet lock 9 and union nut 8

Rice. 16. Additional helium balloon:

1 – balloon; 2 – gearbox; 3 – tee; 4 – carbine; 5, 10 – hoses; 6 – cover pocket; 7 – cover; 8 – union nut; 9 – bayonet lock

The DGB cylinder is connected to the crosspiece of the nitrogen-helium-oxygen cylinder. Reducer 2 with a shut-off valve is screwed into the neck of the cylinder. Carabiner 4 attaches the cylinder to the waist belt of the device. dimensions DGB and its assembled parts do not exceed 330×160×110 mm, cylinder weight 3.2 kg, capacity 1.3 l, operating pressure 20 MPa (200 kgf/cm2). The helium cylinder reducer is similar in design and operating principle to the nitrogen-helium-oxygen cylinder reducer, but unlike it, it is adjusted to a set pressure of 1...1.2 MPa (10...12 kgf/cm2).

Schematic diagram of action

When inhaling (Fig. 17), the gas mixture from the breathing bag 17 through the corrugated tube 8 and the inhalation valve 9 enters the respiratory organs. Upon exit, the gas mixture through the exhalation valve 14 and the corrugated tube 16 enters the regenerative cartridge 27 with the chemical substance O-3. The gas mixture purified from carbon dioxide and enriched with oxygen enters the breathing bag 17, where it is mixed with gases coming from the cylinders of the apparatus and the gas pump through the gas mixture supply mechanisms 13 and 20. Oxygen reducer 23 and switch 20 at depths from 0 to 55...65 m provide a continuous supply of oxygen to the breathing bag 17 from an oxygen cylinder. The oxygen supply depends on the depth and operating modes of the “dive-ascent” apparatus. During the period of increasing ambient pressure at depths from 0 to 20 m, switch valve 21 is open, seat 24 is covered with membrane 26, oxygen enters the breathing bag through nozzles D1, D2 and D3. The oxygen supply is determined by the calibration of nozzle D1 and is 0.3...0.6 l/min. At a depth of 20...24 m, the pressure in the cavity acts on the membrane 19 and bends it, overcoming the force of the spring 18, as a result of which the valve 21 closes under the influence of the spring 22, oxygen is supplied through nozzles D1 and D3 (about 1 l). At depths of 25...30 m, the membrane 26, under the influence of this pressure, overcoming the force of the spring 25, opens the seat 24, oxygen from the gearbox enters through the hole of the seat 24. Since the flow area of ​​the seat hole 24 is much larger than the flow area of ​​the nozzles D2 and D3, the pressure acting on the membrane 26 increases to the oxygen pressure at the outlet of the reducer. The force from the influence of pressure on the surface of the membrane 26 becomes significantly greater than the force of the spring 25, and the seat 24 remains open during further immersion and ascent. When rising to the surface, the oxygen supply from the oxygen cylinder is resumed at a depth of 55...65 m. The oxygen supply is carried out through the D3 nozzle (about 1 l/min). As you climb, the oxygen supply increases. At a depth of 20...24 m, the force of the spring 18 overcomes the gas pressure on the membrane 19, valve 21 opens, and oxygen begins to flow into the breathing bag through nozzles D2 and D3 (3.0...4.4 l/min). This supply of oxygen remains even after rising to the surface. When the ambient pressure increases or when a vacuum occurs in the breathing bag 17, the membrane 2 of the breathing machine 3, bending, opens the valve 11 through a system of levers and ensures the flow of the gas mixture into the breathing bag. Thus, when exiting from depths of less than 100 m with compression in the airlock device, the breathing bag 17 is replenished with a 25% nitrogen-helium-oxygen mixture coming from the AGK cylinder through the reducer, tee 1 and valve 11 of the breathing machine 13. In the event of exit from depths of more than 100 m, the breathing apparatus works in conjunction with the DGB. In this case, the breathing bag 17 is supplied with helium coming from the DGB through the reducer 5, the starter 4 and the breathing machine 13. Since the pressure at the outlet of the reducer 5 (10...11 gs/cm2) is greater than the pressure created by the reducer of the AGC cylinder (5 ,3...6.6 kgf/cm2), then the membrane 6, under the influence of the pressure of the incoming helium, overcoming the force of the spring 7, bends and ensures the closure of the valve 3. The supply of the nitrogen-helium-oxygen mixture to the breathing machine 13 stops at depths of 75...90 m , and instead of it, helium is supplied to the breathing bag.


Rice. 17. Schematic diagram actions of the IDA-59M device:

1 – cross; 2 – gearbox chamber; 3,11,21 – valves; 4 – DGB starter; 5.23 – gearboxes; 6,12,19,26 – membranes; 7,18,22,25 – springs; 8 – inhalation tube; 9 – inhalation valve; 10 – valve box; 13 – breathing machine; 14 – exhalation valve; 15 – safety valve; 16 – exhalation tube; 17 – breathing bag; 20 – oxygen switch; 24 – valve seat; 27 – regenerative cartridge

Characteristics of regenerative substances and gases used for breathing in the IDA-59M apparatus

To regenerate the gas environment in the IDA-59M self-contained breathing apparatus, a granular regenerative substance is used O-3 based on potassium superoxide K 2 O 4. The chemical reaction of absorbing carbon dioxide and moisture from the gas mixture exhaled by the submariner and saturating it with oxygen can be presented in the following form:

Regenerative substances containing oxygen not less than 130 l/kg and carbon dioxide - not more than 15 l/kg are allowed to equip regenerative cartridges. A chemical lime absorber (CLA) is used as a carbon dioxide absorber. The substance KhPI is used mainly during training by personnel educational tasks in the conditions of training stations and complexes. The process of carbon dioxide absorption can be represented as:

An absorber with a carbon dioxide content of no more than 20 l/kg is allowed to be used. Substance O-3 is chemically active. It reacts violently with water, oil, alcohol and liquid fuel. Therefore, when working with the O-3 substance, as well as when storing charged devices on a submarine, the strictest precautions should be observed to avoid explosions and fires. A calcimeter is used to analyze the regenerative substance O-3 for the content of oxygen and carbon dioxide and the absorbent CPI for the content of carbon dioxide. Samples for analysis of a granular regenerative substance or chemical absorbent are taken from each newly opened drum (a container for transporting and storing a substance). At least three samples are taken from three different places in the drum. For breathing, the IDA-59M apparatus uses medical gaseous oxygen (99% O2 and 1% N2), GOST 5583−78. The use of technical oxygen for breathing by divers is prohibited. Oxygen is received from the factory and delivered in transport cylinders to training stations and complexes, where it is filled oxygen cylinders IDA-59M devices. To fill AGC cylinders, a 25% nitrogen-helium-oxygen mixture is used, which contains 25% oxygen, 15% helium and 60% nitrogen. At the same time, the maximum partial pressure of oxygen used when rescuing submariners from an emergency submarine is slightly higher than that established for diving descents (1.3...1.8 ata). Therefore, the duration of stay at depths of 80...100 m while breathing a 25% nitrogen-helium-oxygen mixture to prevent oxygen poisoning is limited to 15...20 minutes. The use of a 25% AHA mixture, due to the increased partial pressure of oxygen, provides a slight increase in the duration of stay under water at the highest pressure when leaving depths up to 100 m inclusive, without the risk of decompression sickness in submariners. At the same time, the exit of personnel from a damaged submarine using this mixture using the buoy-up method makes it possible to use shorter modes. When leaving a depth of more than 100 m, this mixture is unsuitable for breathing due to the danger of oxygen poisoning and must be diluted in the breathing bag of the apparatus with pure helium from the DGB. Air tests for the content of harmful substances and checking the composition of gas mixtures for oxygen are carried out every three months of operation of compressor units, before the start of operation of newly installed or repaired compressors, air lines and cylinders. A conclusion on the suitability of regenerative substances, a chemical absorbent, gas mixtures and air for breathing by divers, regardless of the place where the tests are performed, is given by a special physiologist (doctor) of the ship (Navy organization) or a person providing medical support for diving descents.

Inspiration is the first EU-certified closed-circuit breathing apparatus. Application depth - up to 50 m (recommended - up to 40 m) with air as a diluting gas and up to 100 m with heliox

The acronym SCUBA stands for Self-Contained Underwater Breathing Apparatus. Breathe-helping machine). When using an open circuit breathing system most We simply exhale the inhaled oxygen into the water.

Left. A diver prepares to use a rebreather during the Try-a-Rebreather course at the UK's BS-AC.
In the center. The Drager Dolphin Rebreather is a semi-closed cycle recreational rebreather on Nitrox that is easier to use than closed cycle devices.
On right. This is what's hidden under the futuristic body of the Ambient Pressure (Buddy) Inspiration closed-loop regenerator

Some companies have transformed closed and semi-closed cycle regenerators to meet the needs recreational diving. Exhaled by a diver carbon dioxide chemically is extracted from exhaled gas by passing the latter through a lime-soda scrubber, releasing a mixture of calcium and sodium hydroxides. A certain amount of oxygen is added to the gas thus purified, and the resulting mixture is inhaled again.

Scuba open breathing cycle
1. Breathing gas cylinder
2. Cylinder valve
3. First stage of the regulator
4. Second stage of the regulator
5. Pressure gauge
Breathe-helping machine semi-closed cycle
1. Mouthpiece
2. Mouthpiece shut-off valve
3. Bottom check valve
4. Upper check valve
5. CO2 absorber
6. Counterlang
7. Safety valve
8. Breathing gas cylinder
9. Cylinder valve
10. Regulator
11. Manually adjustable breathing gas supply bypass
12. Pressure gauge
Breathe-helping machine closed loop
1. Mouthpiece
2. Mouthpiece shut-off valve
3. Bottom check valve
4. Upper check valve
5. CO2 absorber
6. Counterlang
7. Dilution gas supply valve
8. Safety valve
9. Cylinder with diluting gas
10. Shut-off valve
11. Diluting gas regulator
12. Bypass for diluting gas supply with manual adjustment
13. Diluting gas pressure gauge
14. Oxygen cylinder
15. Shut-off valve
16. Oxygen regulator
17. Oxygen supply bypass with manual adjustment
18. Oxygen pressure gauge
19. Oxygen sensors
20. Oxygen sensor cables
21. Electronic unit
22. Oxygen solenoid valve
23. Main display
24. Auxiliary display

Because the chemical reaction, as a result of which carbon dioxide is absorbed, is exothermic, releases heat and moisture, the inhaled gas is warm and humid. Closed cycle regenerators do not release any gas into the water. Semi-closed cycle regenerators emit a small portion of exhaled gas with each exhalation. As a result, divers can remain underwater for a long time with only a small volume of breathing gas. Regenerators can run on nitrox, and for deeper dives- on grimeix or heliox.

Breathing apparatus This type requires careful preparation and performance testing. They need quite difficult maintenance, require constant monitoring of the readings of measuring instruments.

Advantages of using a regenerator

  • Gas efficiency, which is essential when it comes to expensive gases, especially helium.
  • Better visibility in confined spaces due to less suspended solids in the water.
  • Quiet operation, allowing the diver to get closer to particularly wary marine life.

Flaws

  • High cost - regenerators are generally more expensive than conventional scuba gear.
  • The complexity of operation requires additional training and strict attention to detail, since the devices include a large number of components that can fail. The warm, humid environment inside the hoses and counter-lung is ideal for the development of bacteria - these elements must be disassembled and cleaned after each day of diving.
  • Most manufacturers refuse to sell theme regenerators. who has not completed a special training course for the operation of such devices.

Closed Type Oxygen Rebreather

This is the ancestor of rebreathers in general. The first such apparatus was created and used by the British inventor Henry Fluss in the mid-19th century while working in a flooded mine. A closed-cycle oxygen rebreather has all the basic parts typical for any type of rebreather: a breathing bag, a canister with a chemical absorbent, breathing hoses with a valve box, a bypass valve (manual or automatic), a bleed valve and a cylinder with a high-pressure reducer. The operating principle is as follows: oxygen from the breathing bag enters through a non-return valve into the diver’s lungs, from there, through another non-return valve, oxygen and carbon dioxide formed during breathing enter the chemical absorbent canister, where the carbon dioxide is bound by caustic soda, and the remaining oxygen is returned to the breathing bag. The oxygen consumed by the diver is supplied to the breathing bag through a calibrated nozzle at a rate of approximately 1 - 1.5 liters per minute or is added by the diver using a manual valve. During a dive, compression of the breathing bag is compensated either by the operation of an automatic bypass valve or by a manual valve controlled by the diver himself. It should be noted that, despite the name “closed”, any closed-circuit rebreather releases breathing gas bubbles through an etching valve during ascent. To get rid of bubbles, caps made of fine mesh or foam rubber are installed on the etching valves. This simple device is very effective and reduces the diameter of the bubbles to 0.5 mm. Such bubbles completely dissolve in water after just half a meter and do not unmask the diver on the surface.

The limitations inherent in closed-cycle oxygen rebreathers are primarily due to the fact that these devices use pure oxygen, the partial pressure of which is the limiting factor in the depth of immersion. So in sports (recreational and technical) training systems this limit is 1.6 ata, which limits the depth of immersion to 6 meters in warm water with minimal physical activity. In the German Navy, this limit is 8 meters, and in the USSR Navy - 22 meters.

Closed-circuit chemical rebreather with premix

There is only one such model in the world and it is called IDA-71 ( Russian IDA71 military and naval rebreather, its further development is called IDA-85, but little is known about this rebreather). Made in USSR . The parts of this apparatus are the same as those of a closed cycle oxygen rebreather, but with two differences. Firstly, there is an automatic washing machine. This mechanical device, which, when a depth of 18-20 meters is reached (it cannot be adjusted more precisely), stops the supply of pure oxygen to the breathing bag and begins supplying a mixture consisting of 40% oxygen and 60% nitrogen (that is, Nitrox). The second (and main) feature is that the IDA-71 has two chemical absorbent canisters. The first is charged with a conventional chemical absorbent based on caustic soda, and the second with an O3 (o-tri) substance created on the basis of sodium peroxide. Substance O3 is capable of not only absorbing carbon dioxide, but also releasing oxygen. The operating principle of IDA-71 is that the diver’s oxygen consumption is compensated not only by supplying fresh breathing mixture, but also by releasing oxygen with the O3 substance. Thus, there is no (at least theoretically) excess of the breathing mixture and the device does not release gas bubbles, earning the right to be called “closed”.

Since the rate of oxygen release by the O3 substance is not constant and depends on many factors that cannot be taken into account, such as, for example, water temperature, it is impossible to accurately determine the oxygen content in the breathing bag of a rebreather, but this task is not set. The diver simply must covertly complete a combat mission. The limitations for this device are inherent in its very design and, in addition to the unpredictability of the oxygen content in the breathing gas, are also due to the use of extremely dangerous substance O3. If water gets on the substance, a violent reaction begins with the release of oxygen, which, if the apparatus leaks, will mean death from oxygen poisoning at depth. Not a single country has launched a similar device into series or experimented with it due to its extreme unpredictability and danger.

To plan dives, decompression tables are used, calculated for this device on the assumption that the partial pressure of oxygen of 3.2 ata is quite safe.

Closed cycle rebreather with manual oxygen supply

This system is also called K.I.S.S. (Keep It Simple Stupid) and was invented by Canadian Gordon Smith. This is a closed-cycle rebreather with mixture preparation “on the fly” (selfmixer), but to the maximum simple design. The operating principle of the device is that 2 gases are used. The first, called diluent, is supplied to the breathing bag of the apparatus through an automatic bypass valve to compensate for the compression of the breathing bag during immersion. The second gas (oxygen) is supplied to the breathing bag through a calibrated nozzle with constant speed, however, less than the rate of oxygen consumption by the diver (approximately 0.8-1.0 liters per minute). When diving, the diver must himself monitor the partial pressure of oxygen in the breathing bag according to the readings of electrolytic oxygen partial pressure sensors and add the missing oxygen using a manual valve. In practice, it looks like this: before diving, the diver adds a certain amount of oxygen to the breathing bag, setting the required partial pressure of oxygen using sensors (within 0.4-0.7 ata). During the dive, a diluent gas is automatically added to the breathing bag to compensate for depth, reducing the oxygen concentration in the bag, but the partial pressure of oxygen remains relatively stable due to the increase in water column pressure. Having reached the planned depth, the diver uses a manual valve to set any partial pressure of oxygen (usually 1.3) and works on the ground, monitoring the readings of the oxygen partial pressure sensors every 10-15 minutes and adding oxygen, if necessary, to maintain the required partial pressure. Typically, within 10-15 minutes, the partial pressure of oxygen decreases by 0.2-0.5 ata, depending on physical activity.

Theoretically, not only air, but also trimix can be used as a diluent gas, which allows diving with such a device to very decent depths, however, the relative variability of the partial pressure of oxygen in the breathing circuit makes it difficult to accurately calculate decompression. Typically, such devices are used to dive no deeper than 40 meters, although there are cases of successful use of trimix as a diluent gas and diving to depths of 50-70 meters. The deepest dive with a device of this type can be considered the trick of Matthias Pfizer, who dived to 160 (one hundred and sixty) meters in Hurghada. In addition to oxygen partial pressure sensors, Mathias also used a VR-3 computer with an oxygen sensor, which monitored the partial pressure of oxygen in the mixture and calculated decompression taking into account all changes in the breathing gas. In general, everything was quite safe, but Matthias did not recommend anyone to repeat this feat. And he did the right thing.

There are a great many conversions of commercial, military and sports rebreathers to the K.I.S.S. system, but all this, of course, is unofficial and under the personal responsibility of the diver converting and using them.

Electronically controlled closed circuit rebreather

Inspiration - rebreather with electronically controlled

Actually a real closed-cycle rebreather (electronically controlled selfmixer). The first such device in history was invented by Walter Starck and was called Electrolung. The principle of operation is that a diluent gas (air or Trimix or HeliOx) is supplied by a manual or automatic bypass valve to compensate for the compression of the breathing bag during diving, and oxygen is supplied using a microprocessor-controlled solenoid valve. The microprocessor interrogates 3 oxygen sensors, compares their readings and, averaging the two closest ones, issues a signal to the solenoid valve. The readings of the third sensor, which differ most from the other two, are ignored. Typically the solenoid valve is activated once every 3-6 seconds depending on the diver's oxygen consumption.

The dive looks something like this: the diver enters two oxygen partial pressure values ​​into the microprocessor, which the electronics will maintain for different stages dives. Typically this is 0.7 ata to exit from the surface to the working depth and 1.3 ata to stay at depth, undergo decompression and ascent to 3 meters. Switching is carried out using a toggle switch on the rebreather console. During the dive, the diver must monitor the operation of the microprocessor to identify possible problems with electronics and sensors.

Structurally, electronically controlled closed-cycle rebreathers have virtually no restrictions on depth, and the actual depth at which they can be used is determined mainly by the error of the oxygen sensors and the strength of the microprocessor housing. Usually the maximum depth is 150-200 meters. Electronic closed-cycle rebreathers have no other limitations. The main disadvantage of these rebreathers, which significantly limits their distribution, is high price the device itself and Supplies. It is important to remember that conventional computers and decompression tables are not suitable for diving with electronic rebreathers, since the partial pressure of oxygen remains constant throughout almost the entire dive. With rebreathers of this type, either special computers (VR-3, HS Explorer) must be used, or the dive must be calculated in advance using programs such as Z-Plan or V-Planer. Both programs are free and recommended for use by manufacturers and creators of all electronic rebreathers.

Semi-closed cycle rebreathers

Semi-closed cycle rebreather with active feed

Simplified diagram of a semi-closed cycle rebreather

This is the most common type of rebreather in sport diving. The principle of its operation is that the breathing mixture EANx Nitrox is supplied into the breathing bag at a constant speed through a calibrated nozzle. The feed rate depends only on the oxygen concentration in the mixture, but does not depend on the depth of immersion and physical activity. Thus, the oxygen concentration in the breathing circuit remains constant during constant physical activity. Obviously, with this method of supplying breathing gas, excess gas appears, which is removed into the water through the etching valve. As a result, a semi-closed cycle rebreather releases several bubbles of the breathing mixture not only upon ascent, but also with each exhalation of the diver. Approximately 1/5 of the exhaled gas is released. To increase secrecy, deflector caps, similar to those used in closed-cycle oxygen rebreathers, can be installed on the bleed valves.

Depending on the oxygen concentration in the breathing mixture, EANx (Nitrox) can vary from 7 to 17 liters per minute, thus the time spent at depth when using a semi-closed cycle rebreather depends on the volume of the breathing gas cylinder. Immersion depth is limited partial pressure oxygen in the breathing bag (should not exceed 1.6 ata) and the set pressure of the reducer. The fact is that the flow of gas through a calibrated nozzle has a supersonic speed, which allows the flow to remain unchanged as long as the set pressure of the reducer is two or more times higher than the ambient pressure.

Semi-closed cycle rebreather with passive feed

A very rare type of rebreather, currently represented only by the Halcyon RB-80 device, which has a safety certificate for the USA and Europe. The operating principle of the device is that from 1/7 to 1/5 of the exhaled gas is forcibly released into the water, and the volume of the breathing bag is obviously less than the volume of the diver’s lungs. Due to this, a fresh portion of breathing gas is supplied to the breathing circuit for each breath. This principle allows you to use any gases other than air as a breathing mixture and very accurately maintain the oxygen concentration in the breathing circuit, regardless of physical activity and depth. Since the supply of breathing gas is carried out only on inspiration, and not constantly, as is the case with active feed rebreathers, the semi-closed cycle rebreather with active feed is limited in depth only by the partial pressure of oxygen in the breathing circuit. A significant negative point in the design of semi-closed cycle rebreathers with passive supply is that the automation is driven by breathing movements diver. Of the devices using a similar principle, the French rebreather Interspiro and the German CoRa are known. The first has not been produced since the mid-60s of the last century, and the second exists in single copies, although it is a relatively recent development.

Mechanical self mixer

A very rare design of a semi-closed cycle rebreather. The first such device was created and tested by Draeger in 1914. The principle of operation is as follows: there are 2 gases (oxygen and diluent), which are supplied through calibrated nozzles into the breathing bag, as in a semi-closed cycle rebreather with an active feed. Moreover, oxygen is supplied at a constant volumetric rate, as in closed rebreather with manual supply, and the diluent enters through the nozzle at a subsonic flow rate, and the amount of supplied diluent increases with increasing depth. Compensation for compression of the breathing bag is carried out by supplying diluent through an automatic bypass valve, and excess breathing mixture is released into the water in the same way as in the case of a semi-closed cycle rebreather with an active supply. Thus, only due to changes in water pressure during the dive, the parameters of the breathing mixture change, and in the direction of decreasing oxygen concentration with increasing depth. Mechanical self-mixers tend to change the oxygen concentration in the breathing bag when physical activity changes, and this is a direct consequence of the fact that their principle of operation is very similar to the principle on which semi-closed rebreathers with active feed are built.

The depth restrictions for a mechanical self-mixer are the same as for a semi-closed cycle rebreather with an active feed, with the exception that only the set pressure of the oxygen reducer must exceed the ambient pressure by 2 or more times. In terms of time, the selfmixer is mainly limited by the volume of diluent gas, the supply rate of which increases with depth. Air, Trimix and HeliOx can be used as diluent gases.

Literature

  • Andrey Yashin. Review of rebreathers. (Retrieved October 7, 2007). Permission to use the article is on the talk page.