Carrying out a working check does not take much time and does not require much effort. A properly performed working check of equipment will allow you to avoid many troubles.
1. Check the pressure in the cylinders.
To do this, instead of the reducer, it is necessary to attach a high pressure control pressure gauge. Close the tap on the manometer. Open the main and reserve air supply valves. Read the readings on the manometer. Then close the valve, open the valve on the high pressure gauge (bleed air from the gauge), remove the pressure gauge.
2. External examination.
A) Check the completeness and correct assembly of the scuba gear (fastening of the gearbox, lung machine, clamps, belts, etc.), you can take the scuba by the straps and shake it easily.
B) Adjust the belts
3. Leak test
A) dry.
With the valves closed, try to inhale from the lung machine. At the same time, the tightness of the membrane, exhalation valves, and connections is checked. Everything is fine if you can not take a breath.
B) Wet.
Open all valves. Place the lung machine under the cylinder, and lower the cylinder into the water. If there are air bubbles from under the connections, the scuba gear is defective.
4. Checking the operation of the bypass valve (reserve).
Open the valve of the main air supply, using the forced air supply button of the lung governed demand valve, bleed some air (approximately 20-30 seconds). Next, open the reserve air supply valve. At the same time, you should hear the characteristic noise of air flowing from the cylinder into the cylinder.
This test does not determine the amount of bypass valve actuation. After completing all the steps, you make sure that you have a working bypass valve in your scuba gear and, as a result, there is a reserve.
Scuba gear AVM-5
1. Regulator set pressure adjustment
2. Adjusting the actuation of the pressure relief valve
3. Adjustment of the lung machine
4. Adjusting the operation of the bypass valve (reserve)
Adjustment of the setting pressure of the reducer (8-10 ati)
1. Measurement of the value of the set pressure.
Disconnect the lung machine.
Attach a control pressure gauge (0-16 ati) to the hose.
Close the valve on the control pressure gauge.
Open the main air supply valve.
Measure the pressure (8-10 ati).
Close the main air supply valve.
Open the valve on the control pressure gauge (bleed air)
2. Adjustment.
Unscrew the gearbox cover (1) fig.4
Pull out the piston (2) fig.4. To do this, screw a puller (or pick up a screw) into the threaded hole in the upper part of the piston and pull the puller. Then the piston can be easily pulled out. It is not recommended to use a screwdriver and try to pick up the piston by the edge.
To increase the set pressure, it is necessary to compress the reducer spring (3) fig.4
To reduce - the spring must be weakened.
Two types of gearboxes were produced.
In the first case, to adjust the setting pressure, it is necessary to place or remove special adjusting washers under the spring (3).
In the second case, it is necessary to move the adjusting nut (7) along the thread of the bushing (8) Fig.4.
In both cases, the meaning of all actions is to compress or decompress the spring (3)
Next, the reducer is assembled and the set pressure is again measured.
Manipulations for adjustment and measurement are carried out until the value of the set pressure is equal to 8-10 atm.
Safety valve actuation adjustment (10-12 ati)
All operating instructions for AVM scuba gear recommend adjusting the operation of the safety valve at the repair and control unit (RCU).
The safety valve is screwed onto a special fitting on the RCU. Pressure is applied to the valve, and by means of the compression force of the spring (11) Fig. 5, the valve is adjusted to the required pressure.
In practice, the adjustment is performed in a slightly different way.
1. Adjust reducer to set pressure
2. Loosen the locknut on the safety valve
3. Slowly rotate the valve body (12) fig. 5 counterclockwise to reach the position at which the valve starts to operate.
4. Screw in the valve body (12) half a turn clockwise until the valve stops drawing air.
5. Tighten the locknut.
Thus, we will adjust the valve to an opening pressure that will be slightly higher than the set pressure (by 0.5-2 ati)
Lung valve adjustment
The instruction manual for the scuba gear says that the lung machine cannot be adjusted.
In practice, the ease of breathing (inspiratory resistance) can be adjusted by bending the lever (5) Fig.6. When the lever is bent, the distance between the membrane (4) and the lever (5) fig. 6 changes, the greater the distance, the greater the resistance when inhaling. It should be noted that if the pulmonary valve is adjusted correctly, then when it is placed in water, air will randomly escape with the mouthpiece up. If the lung machine is turned down with the mouthpiece (as shown in Fig. 6), the air stops escaping.
Bypass valve adjustment (reserve)
1. Measurement of the pressure adjustment of the bypass valve.
When measuring this value, it is necessary to charge the device to a pressure of at least 80 atm.
Unscrew the gearbox and lung machine.
With the reserve air supply valve closed, open the main air supply valve.
Bleed the air.
When the air stops coming out, screw a high pressure control pressure gauge (0-250 ati) to the fitting (instead of the reducer).
Close the tap on the manometer.
The pressure gauge should show 0 ati.
Next, open the reserve air supply valve, and wait until the pressure in the cylinders equalizes (the characteristic noise of flowing air will be heard).
The pressure that the pressure gauge will show will correspond to the pressure of the reserve air supply.
Multiplying the obtained value by 2, we get the response pressure of the bypass valve.
The pressure of the reserve air supply should be within 20-30 atm, respectively, the pressure of the bypass valve operation should be within 40-60 atm.
2. Adjustment
If the results of the measurement show the need for adjustment.
Bleed the remaining air from the cylinders.
Loosen clamps
Loosen the union nuts of the adapter (you can use a gas wrench).
Extend the cylinders and remove the adapter (3)
At the point of attachment of the adapter (3) to the cylinder with valves, access to the adjusting nut of the bypass valve will open.
By compressing or unclenching the bypass valve spring, use the adjusting nut to change the setting. If it is necessary to increase the adjustment pressure, then compress the spring (turn the nut clockwise), if it is necessary to reduce it, decompress the spring.
3. Collect the balloon.
4. Charge up to 80 ati.
5. Take a measurement.
6. Repeat adjustment if necessary.
O-rings and machine lubrication
To ensure the tightness of the connections, the device uses rubber sealing rings of various diameters.
To prevent "drying", the rings must be lubricated. For lubrication, technical vaseline (CIATIM 221), or its substitutes, is used.
The lubricated ring must be placed in the lubricant, held for some time (5-10 minutes), then cleaned of excess lubricant and installed in place.
In addition, the rubbing parts of the gearbox (piston) are lubricated in the apparatus. Lubricant is applied and then excess is removed.
The frequency of device checks.
Operation check - before each descent
Small check (check of all adjustments, lubrication of O-rings) - before the start of the season
Full check (small check + complete disassembly and assembly) - upon receipt from the warehouse, in case of doubt about serviceability, after long-term storage
translates as "water lungs". The creation of the components of scuba gear occurred gradually. First, the surface air regulator was patented, then it was adapted for scuba use. The first successful underwater breathing apparatus using pure oxygen was invented in 1878. The first scuba gear was created in 1943 by Frenchmen Jacques-Yves Cousteau and Emile Gagnan.
Scuba diving can be one-, two- or three-cylinder with air under pressure of 150-200 atmospheres. Usually cylinders with a capacity of 5 and 7 liters are used, but if necessary, cylinders of 10 and even 14 liters can be used. They have a cylindrical shape with an elongated neck, which is equipped with an internal thread for fastening a nozzle or high pressure pipe. Cylinders are made of aluminum or steel. Steel cylinders must be covered with a protective layer, without which their outer part is subject to corrosion. Zinc is used as such a coating. Steel cylinders are stronger and less buoyant. Cylinders are filled with compressed and filtered air or gas mixture. Modern cylinders have overfill protection. The scuba gear is equipped with a lung machine and straps for attaching to the human body.
All scuba gears are divided into three types according to the type of breathing pattern: with open, semi-closed and closed circuit.
If scuba gear works on the principle of pulsating air supply for breathing (only for inhalation) with exhalation into the water, then this is an open circuit. At the same time, the exhaled air does not mix with the inhaled air and its reuse is excluded, unlike devices with a closed cycle.
In scuba gear closed circuit breathing carbon dioxide is removed from the air exhaled by the diver and oxygen is added as needed. In this case, the same volume of air is used for breathing several times. Using this type of scuba, the diver is less noticeable to the inhabitants of the underwater world and does not frighten them, since there are no bubbles of exhaled air.
At semi-closed scheme part of the exhaled air goes to regeneration, and part goes to the water.
Breathing in an open-type scuba gear is carried out as follows: compressed air enters the lungs through a mouthpiece from a breathing machine, and exhalation is made directly into the water. Air is supplied by a regulator connected to the outlet of the balloon block. From each cylinder, air flows into the regulator in turn through the stopcocks. Using the pressure gauge connected to the regulator, you can make sure that the cylinder is filled with air in accordance with the working pressure, and by stretching your hand back and turning the stopcocks, you can find out how much air you have left in the cylinders.
The second stage of the regulator is a pulmonary (respiratory) automaton, which converts the air leaving the first stage of the regulator to ambient pressure and supplies it to the human respiratory organs in the required amount. Breathing machines are divided into two groups - with flow and counterflow valve mechanism. In most modern scuba tanks, a breathing apparatus with a flow valve mechanism is installed. The valve is opened by the air flow coming from the first foot during inhalation and closes the exhalation tube, and during exhalation - the inhalation tube. Thus, in closed-circuit scuba, the loss of clean air and the inhalation of already used air is prevented.
According to their device, scuba gears are single-stage and two-stage, without separation of air reduction stages and with separation. Nowadays, two-stage automata with separated reduction stages are used.
Kit #1 is commonly referred to as the set of equipment most commonly used for non-scuba diving and includes a mask, snorkel and fins.
masks
Almost all of us have tried to open our eyes underwater. As mentioned above, the difference in the refractive indices of water and air is not corrected by the eyes, and the picture of the underwater world consists of blurry spots that do not have clear boundaries. For full-fledged vision under water, the presence of an air gap in front of the eyes is sufficient. The simplest device for this is swimming goggles. However, one should not dive into them to a depth of more than 1 - 2 m: the pressure under the glasses becomes noticeably less than the pressure of the environment and tissues of our body, the glasses begin to work like suction cups. The result is a network of hemorrhages in and around the eyes, and at greater depths more serious troubles are possible (for more details, see chapter 3.3). Therefore, for scuba diving, it is necessary to use a mask that allows, by exhaling through the nose, to equalize the pressure in the space under the mask with the pressure of the environment. We remind you that, according to the international codes of all underwater federations, being in the water with scuba gear without a mask is considered a distress signal.
According to the generally accepted opinion, the mask is the number one item in the personal equipment of a diver. To select a mask, it is necessary to have knowledge about the variety of existing designs and their features. Any mask consists of a soft body, a rigid rim, into which one or more portholes (lenses) are inserted, and a mounting strap.
materials
Most modern masks have a silicone body. However, rubber-bodied masks remain in service and continue to be produced. Silicone is softer and more elastic than rubber, although inferior to it in strength, it is less susceptible to the damaging effects of sunlight and is more durable. Silicone can be transparent, matte, or black. The choice here is a matter of taste. Through the transparent silicone, the outlines of objects are distinguished, which partly increases the field of view. Side beams passing through the transparent silicone body brighten the overall picture of the world, but can create slight glare on the viewing port. Black silicone eliminates glare on the glass, which is important for underwater photo and video shooting.
The rim can be made of impact-resistant plastic or metal. Various materials are used to make lenses. The window of the mask must be durable, and when broken, it must not form pieces with sharp edges. The window of an underwater mask, in comparison with the lenses of "land" goggles, is much more susceptible to the action of various unfavorable factors. This includes both the abrasive action of sand and suspension, and the chemical action of sea water. Some plastics and tempered glass meet the necessary requirements. The first, very expensive, are mainly used for the manufacture of professional masks. The vast majority of masks used by recreational divers have tempered glass lenses. In any case, the porthole must be marked "TEMPERED" or "SAFETY". The mask strap can be made from either rubber or silicone. The latter option is preferable due to the properties of silicone already described above.
^ Mask space volume
Undermask is the space bounded by the mask on one side and the face of the submariner on the other. If the volume under the mask is filled with air - and this is exactly what the design assumes - then the mask has some positive buoyancy, the force of which is directed upwards. This force is noticeable (with the head in a vertical position) for masks with a large submask volume (300 - 400 ml) and hardly noticeable for masks with a small volume (about 200 ml).
^ Viewing Angle
The wider the field of view, the better. Characterizing the mask, it is necessary to evaluate the viewing angle vertically and horizontally. The larger the glass and the closer it is to the eyes, the wider the field of view. The viewing angle is inextricably linked to the design and size of the mask (see below).
^ Hydrodynamic resistance
Hydrodynamic resistance depends on the size and shape of the mask. The smaller this value, the more comfortable the mask.
^ General form
Everyone is familiar with the traditional oval-shaped masks. The lower part of their body has two recesses, allowing you to pinch your nose to blow out your ears. When diving in the first set, it is enough to pinch your nose with the fingers of one hand. If you have a lung machine mouthpiece in your mouth, the dimensions of the latter will not allow you to approach the nose with one hand, and you must use the index or thumbs of both hands to blow out your ears. Several generations of submariners dived in such masks. However, recently they have been almost completely replaced by masks with a separately made protrusion for the nose (photo 2.1). This design allows you to blow with one hand in any situation. Obvious advantages also include a reduction in mask volume, an increase in the angle of vision due to the glass approaching the diver's eyes, and a decrease in hydrodynamic resistance.
^ Masks with one and two lenses
The minimum distance from the sight glass to the eyes of a diver in a traditional oval mask is determined by the size of the nose. In a mask with a separate protrusion for the nose, the bridge of the nose becomes a natural limiter. Further approach of the viewing glass to the eyes is possible by dividing it into two lenses. The angle of view is increased by several degrees; however, many divers prefer single-lens goggles without a vertical baffle in the middle.
^ Ability to compensate for vision
Until recently, submariners in our country were forced to show miracles of ingenuity to correct vision underwater. The simplest at first glance method - the use of contact lenses - has serious drawbacks: in addition to the fact that for any deep diving, special lenses with micro-holes are needed to allow air bubbles to escape from under the lenses, contact lenses of any design easily fly off the eye when hit water under the mask. Experienced divers also remember another trick: medium-sized goggles with the temples removed can easily be placed under the glass of a standard domestic oval-shaped mask and fit into the rubber casing. After spending a little more time, you can glue the lenses of the glasses to the inner surface of the glass of the mask. If the glue is transparent, and the lenses are selected and oriented correctly, then such a mask will be quite comfortable. The most reasonable solution to the problem of underwater vision correction is special two-lens masks with replaceable lenses. Diopter glasses are selected separately for the right and left eyes. So, for example, for the Technisub "Look" mask (photo 2.2), lenses with diopters from - 1 to - 10 and from + 1.5 to + 3.5 are produced in increments of 0.5 diopters. At the factory, all masks are equipped with ordinary glasses, which within a few minutes can be replaced with diopter lenses, matched to your eyes.
^ Anti-fogging glasses
For masks with interchangeable lenses, lenses with an anti-fog coating are available. A layer of material applied on the inside of the glass prevents individual drops of moisture from falling out - it forms a uniform layer that does not affect the clarity of the image.
^ Side and bottom windows
The presence of additional side windows increases the field of view. Under water, the image is shifted in the side windows of the mask due to the refraction of light rays. This, on the one hand, further increases the field of view, on the other hand, expands the "dead zones" formed by the vertical posts. The lower glasses in six-glass masks have the same effect. Masks with additional lenses have a larger volume under the mask than single or double lens masks.
^ Masks with valves
The valve built into the lower part of the mask allows you to blow it out of the water without the help of hands: it is enough to exhale through the nose under the mask. The only necessary condition - that the valve is located at the bottom of the mask - is performed with the usual position of the head (vertical or tilted forward).
^ Fastening strap should provide reliable fastening of the mask and have a convenient adjustment mechanism. The straps of most modern masks have an extension with one or three windows in the back of the head for a better fit to the head. The strap can be adjusted using conventional movable buckles, but a quick adjustment mechanism is much more convenient, allowing you to tighten or loosen the strap without removing the mask. Swivel buckles allow you to choose the optimal angle of the fastening belt.
The size
Masks of one model have a standard size. Some companies produce special children's masks in a smaller size.
^ Mask selection largely determined by the challenges facing you. So, for example, for diving in the first set, masks with a minimum mask volume are especially convenient, since your air supply for inflating the mask when diving is very limited, and if you dive with scuba gear, this is no longer so important. When choosing between a transparent and opaque body material, most divers tend to favor the first, but for professional photography and video shooting, masks with a black body are preferable, as they bring the picture of the world as close as possible to the view through the camera lens. The shape, size, number of lenses are largely determined by your taste.
When choosing a mask, be sure to attach it to your face and try to inhale through your nose. A well-fitted mask will press against your face and make it impossible to breathe. If air passes somewhere, the following options are possible:
1. Hair got under the top flange of the mask. Remove them from the forehead and from the temples back and try again. For better control, you can stand in front of a mirror.
2. Men who wear mustaches will either be forced to part with them or put up with the slow but inevitable leakage of the mask. There is nothing wrong with this - periodically blowing out the mask from the water will soon become familiar to you.
3. You smile too widely during the fitting and air flows through the resulting folds under the mask. Think about something serious and try again.
4. The mask passes air through the connection of the body with the sight glass or has a perforation in the soft body. Change the mask.
5. The shape and quality of the material of the soft body do not provide a hermetic fit of the mask to the face. Try a mask of a different model.
^ Mask care
After diving in sea water, rinse the mask with clean fresh water. Try not to leave the mask in direct sunlight for a long time, do not put it near heating devices. Protect glass (glasses) from contact with hard objects, and soft body - from excessive and prolonged deformation. For transportation of masks, it is preferable to use special plastic boxes.
A tube
Using a snorkel allows you to breathe calmly while lying on the surface of the water and not expend effort on raising your head. The snorkel is very convenient for diving in the first set and is absolutely necessary for a scuba diver. In the latter case, it is used when moving along the surface to save air in the apparatus. The opinion that it is possible to dive without a tube, and, if necessary, to swim the required distance on the surface on the back, is a consequence of a lack of literacy and experience. Who at least once was forced to swim a hundred meters with an empty scuba gear and not in complete calm - he is unlikely to ever neglect the pipe.
For use in combination with scuba, the snorkel is attached to the mask strap on the left side, since the lung machine hose runs on the right side. If you need to switch from breathing from the apparatus to breathing through a tube, you must remove the scuba mouthpiece from your mouth with your right hand, and insert the tube mouthpiece with your left hand - then exhale sharply to clear the tube of water and start breathing atmospheric air. The tube must have a special fastening system to the mask in the form of a plastic clip or rubber ring. Inserting the snorkel under the mask strap without additional fastening is acceptable when swimming in the first set, when you keep the snorkel in your mouth all the time, but when scuba diving, it can lead to its loss.
Breathing through a snorkel is comfortable and safe just below the surface of the water. Immersion even by 20 - 30 cm makes breathing difficult, since the lungs are affected by increasing water pressure, and the pressure of the inhaled air remains atmospheric. Therefore, the length of the tubes is designed for use near the surface. Of course, the longer the tube, the higher it rises above the water and the less it is flooded with waves and spray. But the greater the volume of water must be blown out of it when emerging. The thicker the tube, the lower its resistance to air flow, but also the greater the volume of water to be removed. During normal breathing, a certain volume of air, called dead air, remains in the lungs and airways during exhalation. In this air, compared with the surrounding air, the concentration of carbon dioxide is increased. The volume of the breathing tube increases the dead volume. Thus, the larger it is, the higher will be the concentration of carbon dioxide in the lungs of a diver. Therefore, using a tube that is too long and too wide can lead to carbon dioxide poisoning. All of these factors determined the optimal dimensions of the diving tubes: their length from the bend to the end is approximately 40 cm, and the inner diameter is about 2.5 cm.
Most convenient for scuba divers tubing with flexible segment
(photo 2.3 A), allowing you to quickly and conveniently switch from the device to the handset.
^ Placement of Poppet Valves in the lower and middle parts of the tube (photo 2.3 C, D) reduces the effort required to clear it of water. Valves release water and air from the tube, but do not let it back in. When you rise to the surface, part of the water leaves the tube by gravity, obeying the law of communicating vessels:
The water level in the tube drops to the level of the surrounding water. The remaining volume is about a third of the initial volume and is easily removed partly through the valves, partly through the top opening of the tube.
^ ball valve, placed at the top of the tube, prevents the penetration of water into it during diving (photo 2.3 D). Such pipes are called dry.
The use of tubes with valves is fully justified when diving in the first set (for example, when spearfishing), when the tube is always in the mouth and is continuously filled with water and blown. However, this is not so important for scuba divers: as a rule, you have to switch to the tube no more than two or three times during the dive. When using a tube with a valve, be aware that when immersed in the valve, a grain of sand or other particle may accidentally enter (especially when working in muddy water or algae thickets), which will disrupt the normal operation of the valve. After surfacing after a tedious dive and switching to a snorkel, you rely on a slight blowing force and a normal air supply after it, but you get a continuous filling of the snorkel with water. Many scuba divers are happy to use tubes with valves without encountering the described troubles.
When using a tube consisting of several segments, check the integrity of the connections. You will find yourself in a very unpleasant situation when you find out when you switch to the handset that it was left without a mouthpiece.
Flippers
Can you swim without fins? Undoubtedly. A good swimmer easily spends several hours in the water, covering a considerable distance during this time. You can dive with a mask and without fins, enjoying the beauty of the underwater world. But everything changes when we put on scuba gear. Its weight in water is small, but the mass, i.e. a measure of inertia remains the same as on land - about 20 kg. Rigid balloons behind the back reduce the flexibility of the body and restrict freedom of movement. The use of fins compensates for the difficulties that have arisen. Properly selected, comfortable and efficient fins largely determine the comfort of a scuba diver under water. The choice of the most suitable fin model depends on your tasks and your individual characteristics. To assess the suitability of fins, we single out two parameters:
1. ease of fastening to the leg;
2. swimming efficiency.
The first is determined by the design of the foot pocket, the second by the design of the blade and the overall shape of the fin.
The variety of designs of galoshes comes down to two fundamental options: with closed and open heels. The former are very comfortable when put on on bare feet and provide the tightest connection between the fins and the foot. For putting on wetsuit boots, it is more convenient to use fins with an open heel, equipped with a strap. They are also called adjustable. Modern models of adjustable fins allow you to tighten and loosen the strap right on your foot.
The variety of designs of fin blades is very large. For fins, as for any engine, the efficiency is extremely important, i.e. the ratio of useful work to energy expended. Under water, everything is measured by air: the more energetic the physical work, the greater its consumption. The more efficient the fins, the less air is needed to overcome a certain distance. Ceteris paribus, the efficiency of the fins and their suitability to your individual characteristics can change the air flow rate by 20 - 30%. Accordingly, the time spent under water will change by the same amount.
Everyone is familiar with simple rubber fins with a classic-shaped blade with two stiffeners on the sides. In the initial phase of the stroke, part of the energy is accumulated by the bending blade of the fin and then given off in the final phase with the extension of the blade. One of the possible ways to increase the efficiency of the fins is to increase the area of the rowing surface. However, after a certain limit, it becomes unjustified. For rubber fins, the limit of reasonable length is 60 - 70 cm from the heel to the top of the blade. Fins with a width of more than 20 - 22 cm touch each other when swimming.
Another way to increase the efficiency of fins is to use materials with greater elasticity. This increases both the possibility of energy accumulation in the initial phase of the stroke, and the allowable length of the blade. Excellent hydrodynamic properties are possessed by long fins with blades made of thin, elastic and rather rigid plastic and rubber galoshes. In terms of speed, such fins surpass the vast majority of other models and are optimal for swimming without scuba gear. It is no coincidence that underwater hunters all over the world prefer fins of this design. Scuba divers, on the contrary, rarely use them, as they lose to smaller fins in maneuverability. For swimming with the apparatus, fins with shorter blades made of a similar material are produced.
Another way to increase efficiency is fins with windows (photo 2.4 A). What is their meaning? During the stroke, a zone of increased pressure is created on one side of the rowing surface, and a zone of reduced pressure is created on the other. The resulting eddy currents along the edges of the fin create additional drag. Slots in the base of the blade allow water to pass through, reduce the pressure difference and thereby weaken the vortex flows. This design does not increase the speed reported by the fins, but reduces the effort during the stroke.
The efficiency of fins increases significantly when using the tunnel effect (photo 2.4 B-F). During the stroke, a certain amount of water inevitably rolls to the sides, not participating in the creation of the forward movement of the submariner. If the inside of the fin blade is made of a softer material than the sides, then the fin flexes during the stroke, forming a groove that orients the flow of water in the right direction, thereby reducing the amount of water that rolls down empty. Another way to create a tunnel effect is to divide the plastic blade with 2 - 4 longitudinal rubber grooves that allow transverse bending. A variation of the tunnel effect is the effect of a spoon or ladle, achieved by a wedge-shaped insert of softer material (photo 2.5) or rubber grooves of different lengths. Today, tunnel effect fins are the most popular among scuba divers.
How to choose fins? First, you need to make a choice between closed or open heel fins. For classes in the pool, speed swimming or spearfishing, it makes sense to stop at the first option. If you are serious about scuba diving, we recommend getting open heel fins with adjustable straps and getting neoprene socks or boots, as without them swimming with adjustable fins is extremely uncomfortable and often leads to blisters.
Now about the choice of a specific model. The overall design and color variations are important, but the hydrodynamic properties of the fins are more important. Depending on your physique and physical capabilities, one or another fin will be most comfortable for you. We offer the following test to help you make the right choice. All you need is a swimming pool or an open body of water. Put on your mask and fins, calm your breath and dive a fixed distance on one breath, close to your limit. For someone it will be 25 m, for someone - 50 or more. Relax and repeat the experiment with other fins. Choose those with which this exercise is given to you the easiest. They do not necessarily develop maximum speed, thereby reducing the time of diving, but they most advantageously convert your energy into forward movement, which means they will be the best way to save air when diving.
If the fins do not have metal parts, it is not necessary to rinse them with fresh water after each sea dive, but it is advisable to do this before a long break in operation. Do not leave them for a long time in direct sunlight, do not dry on the stove or other heating device, avoid deformation during transportation and storage. For the latter, do not neglect the use of plastic inserts in the galosh included in the delivery. To remove adjustable fins, it is very convenient to unfasten the clasps on the strap. The part of the lock remaining on the flipper may come off the seat in case of an unsuccessful movement or hitting another object (piece of equipment, side of the vessel). Pay attention to this and try to fasten the strap as soon as possible after removing the fin.
If you follow these simple rules, the fins will serve you for many years.
^ Chapter 2.2. breathing apparatus
Breathing underwater
Whether a person occurred in the process of evolution or was the result of Divine Creation - in any case, the ability to swim came to people in ancient times or was inherited from wild ancestors. The ability to dive under water, apparently, appeared a little later. There are references to underwater divers in chronicles dating long before the birth of Christ. The hero of Mesopotamian myths, King Gilgamesh, descended to the bottom of the sea for a plant that contained the secret of eternal life. In ancient Greece, divers carried goat furs filled with air underwater.
According to ancient manuscripts, Alexander the Great descended into the water in a specially designed glass box - this was probably the first prototype of a diving bell. The principle of its operation is very simple: if we take any vessel with one hole (for example, an ordinary glass), turn it upside down and lower it into water, the air will remain in the vessel, and its pressure will be equal to the pressure of the surrounding water. Recall the Boyle-Mariotte law: air is compressed as many times as its pressure increases. Thus, at a depth of 10 m, where the water pressure is 2 atm. (see chapter 1.1), the glass or diving bell will be half filled with water. There are references to underwater bells from the Middle Ages. One of these designs belongs to the famous scientist Halley, whose name is the well-known comet. Nowadays, diving bells are used for the descent and recovery of professional divers and for other technical tasks. Compressed air from cylinders or supplied from the surface through a hose allows you to "blow" the habitable space of the bell during immersion and thus maintain its volume.
The work of the human respiratory system, as you remember from chapter 1.2, is possible only if the pressure of the inhaled air is equal (almost equal) to the pressure of the external environment acting on the chest. Therefore, breathing underwater from a tube connecting a swimmer to surface air is possible only at a very shallow depth, measured in centimeters. Already at a depth of 20 - 30 cm, such an activity, in addition to rapid fatigue, can also bring unpleasant consequences for health (for more details, see chapter 3.2). The first equipment using compressed air supplied to a diver at a pressure equal to ambient pressure was proposed in 1865 by Rouquayrol and Denayrouze.
From the beginning of the 20th century to the present, ventilated equipment has been used to perform various underwater technical tasks - a spacious overall made of durable rubber, hermetically connected to a metal helmet. Such a suit completely isolates the diver's body from contact with water. A hose is connected to the helmet, through which a constant supply of air from the surface is made, for example, using a manual or automatic pump. At the back of the helmet there is a bleed valve that is activated by light pressure on it with the head. The principle of operation is simple: by bleeding the required amount of air, the diver changes the volume of the suit, thereby adjusting his own buoyancy. The air pressure inside the suit naturally equals the pressure of the surrounding water. If the diver stops depressing the bleed valve, the diver's buoyancy increases along with the inflation of the suit, which can lead to a resurfacing.
Ventilated equipment provides unparalleled comfort for tasks that do not require active movement under water. Its disadvantages are low mobility, the need for a bulky material base (pump, hose, etc.), the obligatory connection of the diver with the shore or ship, and the presence of several qualified assistants.
A new era in the development of diving began with the invention of scuba diving. E. Gagnan and J. - I. Cousteau created an underwater vehicle, convenient and practical to use, allowing a person to autonomously move under water, having a sufficiently large supply of air with him. The word "Aqualung" (Aqualung) literally translates as water (aqua) light (lung). That was the name of the first underwater vehicle. This word has taken root and is used to refer to all subsequent designs of a similar type. Another popular name for scuba diving has become English - SCUBA - Self-Contained Underwater Breathing Apparatus (autonomous underwater breathing apparatus).
Today, there are various designs of underwater equipment and ways to classify it according to various criteria. For example, all types of diving equipment can be divided according to the type of breathing pattern: open, semi-closed and closed. With an open breathing scheme, the exhaled gas is discharged into the environment, with a closed one, it is sent to a special device that cleans it from carbon dioxide and enriches it with oxygen, from where it is again taken for inhalation. This renewal of exhaled gas is called regeneration. With a semi-closed scheme, part of the exhaled gas goes into the environment, part - for regeneration. If the entire supply of air is in cylinders carried by the diver himself, such equipment is called autonomous. For many technical jobs, hose equipment is more convenient. The main amount of air is supplied to the diver through a hose from the surface, and behind the shoulders of the submariner there is only a small reserve.
In this book, we consider the technique most commonly used by recreational divers, namely, self-contained equipment with an open breathing pattern, i.e. scuba. Outside of this book also remains equipment adapted to work on gas mixtures, and not on compressed air, since this topic belongs to a more professional field of knowledge than this edition implies.
^ General scuba device
Any scuba gear consists of cylinder block and regulator
(Fig. 2.4 A). The cylinder block has one or two (very rarely three) compressed air cylinders equipped with a valve. Cylinders designed for 150, 200, 230 and 300 atm are widely used. The pressure in the cylinders is called high pressure. As you remember (chapter 1.2), a person can inhale if the air he inhales is at the same pressure as the chest. To supply air to the diver under ambient pressure is used regulator, connected to the outlet of the cylinder block. The vast majority of regulators consist of two elements, in which the reduction (reduction) of air pressure occurs in stages. This reduction scheme is called two-stage. The device called reducer, carries out first step reduction - reduces air pressure to a value exceeding the ambient pressure by 5-10 atm. This pressure is called intermediate or average. Pulmonary automat (pulmonary) carries out the second stage of reduction - equalizing the pressure of compressed air to the ambient pressure, which is called low pressure*.
* sometimes the pressure at the outlet of the reducer is called low pressure, then the pressure at the outlet of the lung can be called ambient pressure
Chapter 2.3. Cylinders and balloon blocks
Scuba tanks have a cylindrical shape with a rounded bottom on one side and an elongated neck on the other side (photo 2.6 A). The neck is equipped with an internal thread, conical for Russian models and cylindrical for foreign ones. A short branch pipe with one or two valves is screwed into this thread in the case of a one-cylinder block (photo 2.6 B) and a high-pressure pipe leading to the valve (s) in the case of a two- or three-cylinder variant.
^ Cylinder material
Modern industry produces steel and aluminum cylinders. The former are more common. The main advantage of steel over aluminum is its significantly greater strength. The disadvantage of steel is its susceptibility to corrosion. In order to slow down corrosion processes, various methods are used:
the use of alloy steels, i.e. with additives of other metals, mainly chromium and molybdenum;
coating the inner and outer surfaces of the cylinder with a thin layer of zinc;
coating the outer surface with polymer paint, and sometimes with plastic;
coating the inner surface with special vaseline-like lubricants.
The susceptibility to corrosion of products made of aluminum and aluminum alloys is much lower. This is due to the ability of aluminum to form an oxide film on the surface, which protects the deeper layers of the metal from further oxidation. Since the strength of aluminum is much lower than steel, the walls of the cylinder must be thicker than steel, designed for the same pressure. However, aluminum is almost three times lighter than iron, the main component of steel. As a result, the specific gravity of aluminum or alloy cylinders is lower than that of steel cylinders of the same volume and strength.
In general, steel tanks are more practical than aluminum tanks and are preferred by most scuba divers. But let's not forget about one more property of aluminum. It is not magnetized, does not affect the direction of the magnetic compass needle and the readings of other magnetic devices. Therefore, if you need to get through minefields with magnetic traps, use aluminum cylinders.
^ Accessories
For ease of storage and transportation, the lower part of the cylinders is usually inserted into a rubber shoe. Carry a single-cylinder by grasping the plastic handle, much more convenient than for the valve mechanism. Handles are solid and folding. Nylon protective nets protect the outer coating of the cylinders from damage, which is especially important when using cylinders in salt water, where any scratch on the paint leads to corrosion.
^ High, working and test pressure. stigma
Recall that the air pressure in the cylinders is called high. The maximum allowable high pressure during operation for a given cylinder block is called working pressure. Before being released from the factory, any cylinder is subjected to a pressure test one and a half times higher than the working one - the so-called verification. Each cylinder is provided with a stamp containing its main characteristics. The brand is stamped on the neck and must contain the following information:
name or trade mark of the manufacturer;
serial number of the cylinder;
operating pressure;
test pressure;
month and year of manufacture and inspection;
cylinder weight (without valve);
balloon volume.
On domestic cylinders, the date of manufacture followed by a hyphen is the year of the next proper inspection. On foreign cylinders, the type of cylinder is usually stamped, i.e. for what purposes it is intended.
Cylinders must be re-inspected five years after manufacture. It is carried out by licensed organizations. The test includes a number of actions: first of all, weighing the cylinder, inspecting its outer and inner surfaces and hydraulic testing with test pressure. If the cylinder has passed the test and is recognized as fit for further operation, the testing organization puts a stamp on it, which must contain its own name or brand name, the month and year of the test and the value of the test pressure.
^ Number, shape and size of cylinders
The most popular among divers all over the world are single-cylinder sets with a capacity of 12 - 15 liters. They are easy to handle, and the air supply at a pressure of about 200 atm. sufficient for non-decopressive dives, which are most often made by lovers of the underwater world. The domestic industry mainly produces two-balloon devices with a cylinder capacity of 7 liters each. Thus, the most common Russian scuba gear is a two-cylinder tank with a total capacity of 14 liters. Scuba diving AVM - 5 allows the separation of cylinders, and then one of them, equipped with a valve, can be used in a single version, however, 7 liters. at a pressure of 150 or 200 atmospheres - not too much air for diving in open water. It is convenient to use similar cylinders for employment in the pool. On the one hand, a 15 liter single tank is slightly lighter than a 14 liter double tank, on the other hand, the center of gravity of the double tank is located a few centimeters closer to the center of gravity of the swimmer, which reduces the inertia of its rotation in the water. The question of preference for a one- or two-cylinder version of scuba gear with their approximately equal volume is not unambiguous and is a matter of taste.
If you are experienced enough to go on a deep dive with decompression breaks on ascent (see chapter 3.4), have a mission to dive under ice, plan to explore underwater caves or search for treasure inside sunken ships, you might want to consider increasing your air supply. For this you can:
Use cylinders with higher air pressure. Today, cylinders with a working pressure of 230 and 300 atm are widely used;
Use larger containers. The maximum volume remaining within reasonable limits is 18 liters;
Increase the number of balloons. The most common option, in addition to the domestic 7 + 7, is 10 + 10 and 12 + 12;
^ Cylinder shape
It is quite standard, but allows a number of variations with the same volume. So, for example, 12-liter cylinders are available in several modifications. The advantages of an elongated balloon are better hydrodynamics and a closer location of its center of gravity to the center of gravity of the swimmer, which, as already mentioned, reduces the turning inertia in the water. True, such a balloon can create inconvenience for people of short stature - they are better suited for more compact balloons.
Thus, the choice of the size, number and shape of cylinders is determined by the tasks facing you and, in many respects, by your taste. The latter also applies to the colors of the balloons, which are usually bright and easily visible in the water.
^ valve mechanism
By itself, a high-pressure cylinder, of course, cannot serve as a source of breathing air. The first device on the way of air from the cylinder - valve mechanism, often referred to simply valve(photo 2.6 B). The latter term seems less correct, since sometimes this mechanism consists of several valves, includes additional devices, and in the case of a two- or three-cylinder block, an extensive system of high-pressure pipes. The inlet pipe of the valve mechanism has an external thread, which is screwed into the internal thread of the cylinder neck. The domestic industry produces cylinders and valves with tapered threads, which are sealed with special seals (for example, lead oppression), evenly applied to the entire surface of the thread. Foreign cylinders and valves have cylindrical threads and are sealed with an annular plastic gasket. Valves from cylinders are unscrewed only during the technical examination of the latter and only by qualified professionals. Inside the cylinder, the valve mechanism faces a tube several centimeters long, which has one or more holes, sometimes covered with a fine metal mesh. Such a device significantly reduces the likelihood of rust particles penetrating the scuba airways, which, as a rule, spill over the walls of the cylinder. Shut-off valves have a right-hand thread, i.e. open in the same way as a water tap, counterclockwise.
One of the key points in the structure of the valve mechanism is the air outlet device. It must be adapted for convenient, quick and reliable fastening. gearbox - first steps regulator. Today there are two international standards for such fastening:
Mounting by means of a clamp is called YOKE (English - bracket, clamp) or INT.
Fastening by means of a carving with a diameter of 5/8 inch - DIN. In both cases, sealing is achieved by an annular rubber gasket.
The vast majority of modern foreign-made cylinders are adapted for use in both YOKE and DIN versions. The mechanism is simple: the cylinder has an outlet with a DIN thread, into which a sleeve is hermetically screwed, the outer surface of which corresponds to the YOKE standard (photo 2.6 B).
In addition to international connections, there is a Russian standard for mounting a gearbox on cylinders - a thread with a diameter of 24 mm. Recently, some manufacturers have launched the production of adapters that allow you to combine domestic and foreign cylinders and gearboxes. The latest development of the domestic industry - the device ABM-12-1 has a connection of the international DIN standard.
The shape of valve mechanisms can be very diverse. The simplest single-cylinder block has a single valve and a single outlet (photo 2.6 B). In this case, differences in the location of the valve and the outlet are possible, which do not play a fundamental role. There are the following options for complicating the design:
4- Additional outlet with a separate valve for attaching a second regulator. Two regulators are often used for greater reliability in advanced dives such as caves, flooded areas, under ice, or simply in cold water where there is a risk of freezing of the gearbox or lung governed demand valve (see below). In the event of any malfunction with the regulator, you can switch to a spare. An additional outlet with a valve can be removable - then the valve mechanism is equipped with a plug that closes the connection point.
Outlet for connecting a second cylinder. When using a single-cylinder block, it is tightly closed; to add a second cylinder, unscrew the plug and connect the adapter.
In a two-cylinder block, it is possible to supply each cylinder with a separate valve; sometimes there is a third - common - valve.
Domestic scuba gear has a backup mechanism of a different device: in the high-pressure tube connecting the two cylinders, there is a valve that shuts off the air supply from the right cylinder when the pressure in it drops to about 60 atm. When the air in the left cylinder runs out, it is necessary to open the reserve valve, which releases the remaining air from the right cylinder. The opening of the reserve in this design is accompanied by a characteristic sound heard both in air and in water - the sound of air bypassing from the right cylinder to the left one until the pressure between them equalizes. Thus, after the opening of the reserve, approximately 30 atm remains in both cylinders. The reserve valves in domestic cylinders have the same working stroke as the main supply valves - a little more than one turn - and a left-hand thread, i.e. unlike main flow valves, they open clockwise. In the widely used devices AVM - 5 and AVM - 7, the reserve valve is actuated by a cable wound around the flywheel. The cable goes down along the cylinder inside the protective casing and ends with a pear-shaped handle with spring clips (photo 2.7 A). To open the reserve, it is necessary to release the handle by pressing the latches and pull it down until it stops. Such a mechanism, due to its complexity, requires careful regular maintenance in the form of bulkheads and lubrication. In the devices of the "Submariner" series, another design solution was used: the scuba gear is "upside down", i.e. its normal operating position is with the valves down;
The reserve valve is located under the submariner's right hand and opens without any additional mechanisms. The obvious inconvenience of this design is the need to use a longer hose connecting the reducer to the pulmonary valve, and to turn the balloon over each time it is put on.
How much reserve air is needed? Its presence is mandatory in the absence of a remote pressure gauge showing the pressure in the cylinders. If there is such a pressure gauge, the reserve mechanism becomes a backup device informing the diver that the air is running out. You can admire the beauty of the underwater world and forget to look at the pressure gauge in time, but you can't help but notice the end of the main air supply. On the other hand, any mechanism occupies volume, has weight and requires maintenance. Today, there is a worldwide trend towards abandoning the reserve mechanism, at least when diving under normal conditions.
^ Cylinder mounting
In the vast majority of cases, scuba gear is worn behind the back like backpacks. There are other options: for example, in scuba diving or underwater orientation, the only cylinder is held by the athlete by the valve in front with outstretched arms. When attaching the balloon behind the back, three types of design are possible:
1. One or two cylinders are fastened with a belt (sometimes two belts) to a compensator vest. This is the most common method of fastening in world practice. In the case of a two-cylinder block, a pair of mounting bolts is often used. These mechanisms are discussed in more detail in the chapter on buoyancy compensators,
2. One or two cylinders are attached in the same way to a special anatomical back, equipped with shoulder and waist belts.
3. The straps are attached to metal ties around the cylinder block. This method of fastening is used in most domestic scuba gear. They, as a rule, in addition to shoulder and waist belts, have crotch straps - going between the legs of the submariner. The purpose of the crotch strap is to prevent the scuba gear from moving upward; inconvenience - the need for preliminary unfastening when removing or emergency dropping the weight belt. A well-fitted waist belt makes a crotch strap optional. Modern amateur equipment of the international standard, as a rule, does not provide for its availability.
Before you start filming underwater, it is absolutely necessary to have a good understanding of the theory and practical exercises in the technique of underwater sports. After the scuba gear, mask, fins and breathing tube become so familiar and natural that you stop feeling them, you can also take on an underwater movie camera.
DIVING SUITABILITY
Speaking of scuba diving, it is immediately necessary to distinguish between swimming and diving with a breathing tube from scuba diving. The first case is simpler and more accessible, but in the second case, the operator, having turned into an amphibious man, gets immeasurably better opportunities for shooting.
Any person with healthy ears and heart is fit for scuba diving. Sometimes two circumstances interfere with the rapid mastery of this art: some hydrophobia, as well as difficulty breathing through the mouth that occurs in some people (when diving, they breathe only through their mouths). These obstacles can be overcome (the first one very easily) by practicing snorkelling. The sight glass of the mask gives a person confidence in the water, as it makes it possible to see the bottom and all surrounding objects. Since the mask also acts as a float, the beginner is quite surprised that he does not sink even when he does not make the slightest movement, and this gives him a feeling of confidence and security (Fig. 16).
Difficulty breathing through the mouth (which is quite rare) is explained. a purely nervous condition caused by the fear of suffocation, since breathing in this case is not quite free. Approximately the same is experienced by some in a gas mask. A few snorkel exercises should dispel the fear. After that, the swimmer will feel good in the water when diving and breathe normally through the scuba mouthpiece. In domestic diving practice, another name for the breathing mouthpiece is common - a mouthpiece. This name comes from the fact that the rubber mouthpiece is inserted into the mouth and held by the teeth and lips.
Snorkel, mask, fins
The breathing tube provides breathing while swimming when the swimmer's face is under water. Moving with the help of fins, he has the ability to view objects in the water through the glass of the mask. If necessary, the swimmer dives for a pause between inhalation and exhalation.
The simplest breathing tube consists of two parts: an aluminum, plastic or rubber (elastic) curved tube and a mouthpiece, i.e., an elastic mouthpiece articulated with the lower end of the tube to hold it in the teeth.
Typically, the length of the tube does not exceed 450 mm with an inner diameter of 15-22 mm and has a volume of 100-200 cm3. The weight of the tube ranges from 80 to 300 g (Fig. 17).
Rice. 17. Valveless breathing tube: 1 - tube; 2 - mouthpiece front shield; 3 - mouthpiece; 4 - "snacks" for holding the mouthpiece with your teeth; 5 - lips; 6 - teeth; 7 - language
The device of the tube is so simple that it is easy to make it yourself.
The simplest snorkel is preferred by experienced divers, by everyone else, and is the main sport type of snorkel.
More complex in design are breathing tubes with automatic ball or float valves that prevent water from entering the tube (Fig. 18). The action of automatic valves is that a light cylindrical ball, or float, emerges and blocks the access of water to the inside of the tube. Such tubes are used by beginners who do not yet have the skill to use a more convenient, simple tube.
There are breathing tubes in combination with a mask. The principle of their device is the same as that of tubes with an automatic valve, but when used, the breath is taken through the nose, since the mouth is outside the mask. Such tubes are less convenient, and we do not recommend them for underwater film enthusiasts.
The importance of breathing tubes in underwater sports cannot be overestimated. In addition to simplicity and ease of use, they make it possible to set your own breathing regimen under various loads, acquire a conditioned reflex in closing the airways when water enters the tube.
The breathing tube must be behind the belt and the scuba diver. It may not be needed on ten, fifteen, or even twenty dives, but on the twenty-first dive, the breathing tube will save his life.
Under water, a scuba diver feels calm and confident. But when he comes to the surface, he is nothing more than a swimmer loaded with heavy equipment. If he emerges far from his base (boat or shore), having used up all the air in his cylinders, and if, in addition, there is a slight wave on the sea, the situation may be threatening. In this case, the diver begins to tire quickly, especially since, due to the equipment, he is not as free in the water as an ordinary swimmer. Therefore, he is forced to use a breathing tube instead of scuba gear, which rises sufficiently above the water. Then the swimmer is not in danger of drowning, and he calmly returns to his base, not fearing that he will be exhausted.
Therefore, one of the basic rules of scuba diving is the obligatory presence of a breathing tube, regardless of whether you are going to dive to deep or shallow depths, close or far from the coast.
The second very essential accessory of a swimmer is the mask (Fig. 19). It serves to protect the eyes from the surrounding water and thereby provides the swimmer with the ability to see in clear water. The separate device for breathing and vision is a reliable guarantee of safety. If the mask falls or fills with water, the swimmer will continue to breathe normally through the mouthpiece. He can either float up, pinching his nose (if the mask was asleep or the glass broke, which has not happened in practice yet), or, if the mask is in place, but filled with water, calmly remove the water.
The device of the mask is simple: it consists of an oval or round viewing glass, a rubber base, a metal tie-down rim and an occipital strap, or headband, which is fixed in the upper part of the face.
A conventional mask has a flat safety glass window that changes the perception of distance and increases the size of objects. This is due to the higher refractive index of water (1.33) compared to air. Therefore, under water, the bottom usually seems closer than it really is. In reality, such an increase in objects does not really matter, since you stop noticing it after the first attempt to swim with a mask.
An increase in objects is felt only when a familiar object (for example, a bottle, a can) enters the field of view.
In order to have a normal image under water, in a number of countries a special corrective mask is used with two windows, each of which has a convex and a concave lens (Fig. 20). Lenses eliminate distortion of shape, distance and increase the field of view. A corrective mask makes it possible to see life-size objects underwater, but in the air it distances and distorts objects. Therefore, this distortion should be taken into account when entering and exiting the water.
The mask allows you to dive to any depth and swim on the surface. This explains its versatility and widespread use among athletes. The mask, like the breathing tube, is easy to make yourself.
Fins are the third essential element for scuba diving. They serve to increase swimming speed and maneuverability underwater. In addition, fins are extremely energy-saving for the swimmer.
At this time, several dozen varieties of flippers are known, but they all have, in principle, one device and one purpose. However, the degree of elasticity of caresses is the main criterion for assessing their quality and allows all fins to be divided into three types: elastic, normal and rigid.
Practice has established that the efficiency of elastic fins is significantly inferior to normal and even more rigid ones. It is good to use normal fins for long swimming and for long distances, since in this case the swimmer's forces are more advantageously spent.
Athletes prefer rigid fins when swimming for short distances at maximum speed, as well as when it is necessary to increase maneuverability.
In this case, the athlete's strength is most fully spent in a short time.
Well-chosen fins make it easier for the swimmer to maneuver in the water, increase the speed of movement, and free their hands for filming.
SCUBA
The most remarkable quality of scuba gear is that it allows a person to swim underwater at various depths and in any position without any additional adjustment. The device automatically adjusts the amount of air supplied to the lungs depending on the depth of the dive. Thanks to scuba diving, a person under water, as it were, acquires second lungs, specially adapted for breathing in water, and does not feel bound by anything.
The body is freed from the need to be only in an upright position, as it happens on earth. At will, a person can dive deep or float to the surface.
With such equipment available for development and relatively safe, we can talk about its widespread use in underwater filming.
A feature of this apparatus is that it is filled not with oxygen, but with compressed air. Scuba diving uses an open breathing system: the air exhaled by a person, without lingering anywhere, comes out (Fig. 21).
Thus, fresh air is constantly supplied to the human lungs from the cylinders. The use of compressed air completely eliminates the possibility of oxygen starvation, carbon dioxide poisoning or oxygen poisoning. The advantage of scuba gear over other diving apparatus is the ease of construction and operation, as well as readiness for immediate action? immediately after opening the cylinder valves.
How is scuba gear?
Its main parts are: a lung machine, steel cylinders for storing compressed air up to 150-200 atm, two corrugated rubber hoses, a mouthpiece and a system of belts for attaching the device to the body.
The lung machine is the main and most critical part of the apparatus. Its task is to lower the pressure of the air in the cylinders to the pressure of the external environment and supply it to the human lungs in a timely manner and in the required quantity. The lung machine is actuated by the lungs of a person, due to which its work is automatically coordinated with the rhythm of breathing: air is supplied to the lungs only during inhalation, and during exhalation the supply stops. The lung machine is connected to the cylinders and to the mouthpiece by means of two corrugated hoses, one of which is used when inhaling, and the other when exhaling.
The most common domestic scuba gear is "Submariner-1" (factory brand AVM-1), manufactured by the "Respirator" plant of the Mosoblsovnarkhoz (Fig. 22).
Rice. 22. General view of the scuba "Submariner-1"
In this apparatus, air compressed up to 150 atm is stored in two cylinders fastened into a cassette with two clamps. The capacity of each cylinder is 7 liters. Thus, the total air supply at full pressure is about 2100 liters.
A two-stage lung machine is attached to the cylinders.
The device is mounted on the diver's back with a set of straps - two shoulder, waist and lower, which, when put on, are connected to each other with one easily detachable buckle. The set of equipment for the device includes a mask and a weight belt.
The weight belt is a belt with an easily detachable buckle to which lead weights are attached. The amount of weight can be different (the kit includes 14 weights of 0.5 kg each) and is selected in such a way that the athlete is in a state of neutral (zero) buoyancy or slowly sinks. Usually, weights have to be used only when swimming in wetsuits.
The weight of the "Submariner-1" with filled cylinders is 23.5 kg, and under water - 3.5 kg, i.e. the device pulls the swimmer to the bottom. To avoid this, a piece of styrofoam, a rubber football bladder, or other object lighter than water can be attached to the apparatus. In the modernized "Submarine-1" (factory brand AVM-1M), this drawback is eliminated, and to compensate for the weight, foam plastic is attached to the cylinders in the factory.
The maximum diving depth for scuba diving is 40 m. Diving deeper* is not recommended to avoid possible impairment of vital functions known as nitrogen intoxication. Is this why it's not recommended? dive several times a day and consume more than two cylinders per day.
It is known that the amount of air consumed varies depending on the pressure of the medium: as you dive for every 10 m, it increases by approximately 1 atm. Therefore, the duration of diving depends on the depth of the dive.
On the surface or at a depth of up to 1 m, the average duration of stay under water in the Scuba Diver-1 is practically about 70 minutes, at a depth of 5 m - 50 minutes, at 10 m - 30 minutes, at 20 m - 20 minutes and, finally , at a depth of 40 m - about 3-10 min.
These time norms should not be taken literally, as they depend on the following two factors:
1) on the amount of air absorbed during breathing, which is not the same for different people; many divers, after some training, learn to regulate their breathing and at the same time show miracles of economy, using to the end every cubic centimeter of air;
2) on the number of muscular movements during scuba diving; a stationary or slow moving diver consumes less air than someone who is active in the water or doing hard work.
Schematic diagram of the scuba "Submarine-1" is shown in fig. 23. It consists of two systems: high and low pressure.
The high pressure system includes cylinders, connecting air ducts, a minimum pressure indicator 17 and a pressure gauge 16. The low pressure system starts from the lung machine valve 7 and ends with a mouthpiece through which breathing is performed.
When inhaling through the mouthpiece, a vacuum is created in the chamber of the lung machine. The difference between the outside pressure and the pressure in the chamber of the lung machine causes the membrane 1 to bend down. In this case, the membrane rotates lever 2 clockwise about axis 5. Lever 2 rotates lever 4 about axis 5 counterclockwise. The lever 4, when moving, presses the screw 6 screwed into it onto the valve stem 7 with a rubber cushion. Valve 7 moves away from the seat of the lung machine, and the air, passing from the reducer chamber into the chamber of the lung machine, is throttled to external pressure and enters the respiratory organs through the inhalation hose.
After completion of inhalation, the vacuum in the lung machine chamber stops and membrane 1 stops pressing on levers 2 and 4. Valve 7, under the force of spring 8 and air pressure under the valve, will close the opening of the lung machine seat. The pressure in the submembrane cavity will become equal to the external pressure, and the access of air from the reducer to the lung machine will stop.
Exhalation is carried out through a hose that ends with a petal valve. Air, passing through the slots of the petal, rushes into the supra-membrane space of the pulmonary automaton and then, through the holes in its cover, goes into the water, rising in the form of bubbles to the surface.
Simultaneously with the operation of the lung machine comes into action and the gearbox.
Rice. 23. Scheme of scuba diving "Submariner-1"
Through an open valve, compressed air from the cylinders enters through the high-pressure pipeline system under the reducer valve 9, lifts it and follows into the reducer chamber. In this case, the pressure in the reducer chamber increases. As soon as it reaches a value of 5-7 atm (the so-called set pressure), the membrane 14 bends upward, drags the rod along with it and turns the lever 11 associated with it clockwise around the axis 12. In this case, one shoulder compresses the spring 10, and the other presses through the pusher 13 to the reducer valve 9 and presses it to the seat, thereby stopping the flow of air into the reducer chamber.
This cycle is repeated in accordance with the rhythm of breathing.
In the reduction chamber, and consequently, in front of the lung machine valve, the excess air pressure in relation to the outside air pressure is automatically maintained in the range of 5-7 atm.
To prevent an increase in air pressure in the reducer chamber above the set value, a safety valve 25 is provided, which releases excess pressure to the outside. The safety valve comes into operation when the hermetic seal of the reducer valve 9 to the seat is broken, which can happen both during operation and during storage of the device.
Simultaneously with the supply of compressed air under the reducer valve 9, it also enters the pressure gauge 16 and the minimum pressure indicator 77, which serves to warn the scuba diver about the need to go to the surface. Under water, it is possible to control the air pressure in the cylinders using a manometer (in clear water) or by probing the minimum pressure indicator rod (in muddy water). If the air pressure in the cylinders has dropped to 30 atm and the indicator rod 18, under the action of the spring, takes the extended position with a characteristic click, the scuba diver must go to the surface, since the air in the cylinders remains for several minutes of the apparatus operation. To bring the minimum pressure indicator 17 into working condition, it is necessary to press the stem button 18 to the full and only then open the cylinder valves.
In addition to this method, there are sound indicators of minimum pressure to notify the scuba diver about the need to rise to the surface. Such an indicator in the form of a whistle is used in the scuba gear "Ukraine" produced by the workshops of mountain rescue equipment in the city of Lugansk. This device is also based on the principle of pulmonary-automatic action with an open breathing system. The supply of compressed air up to 200 atm in the scuba "Ukraine" is contained in two cylinders with a capacity of 4 liters each and thus amounts to 1600 liters.
The scheme of scuba "Ukraine" is shown in fig. 24. In one block with a lung machine, a minimum pressure indicator is combined. His work is as follows. When inhaling, compressed air from the cylinders enters the chamber of the lung machine and at the same time under the diaphragm 1 of the minimum pressure indicator. The spring 2 is in the Compressed position, and the stem 3 occupies the maximum height, holding the connecting tube 4 on the platoon.
Rice. 24. Scheme of scuba "Ukraine"
As air is consumed, the pressure in the cylinders, and consequently, on the diaphragm 1, decreases. At the same time, the rod 3 under the influence of the spring 2 goes down and, at a pressure in the cylinders of 35-40 atm, releases the tube 4, which connects the outlet of the lung machine with the whistle 5.
In this position, every breath of the diver will be accompanied by a sound signal - this means that it is time to go to the surface.
CHARGING SCUBA WITH AIR
The device can be charged with air either directly from a high-pressure compressor (150-200 atm) equipped with a filter, or from transport (40-liter) cylinders, previously pumped through a filter. Since a special compressor has not yet been created for underwater sports, in practice a field carbon dioxide charging station (FCS) is used to charge scuba cylinders. This is a relatively bulky portable compressor unit with an AK-150 high-pressure compressor (Fig. 25). With such a compressor unit, it is possible to charge the Scuba Diver-1 with two cylinders with a capacity of 7 liters each up to 150 atm in 50-60 minutes with air.
It is expedient to charge transport cylinders with compressed air from high-pressure compressors of higher productivity. For this purpose, compressor stations AKS-2 or AKS-8 can be used, which are towed by a truck on a special two-axle trailer.
The scuba cylinders are charged with air from transport cylinders according to the scheme shown in fig. 26. In this case, three transport cylinders are usually used in order to make fuller use of the air contained in them.
Transport cylinders charged with air up to 150 atmu are connected using spiral tubes to an oxygen pump of the KN type, which, in turn, is connected to a filter, in this case OKN-1.
After the circuit is mounted and tested, for charging it is necessary to open the valves on the cylinders of the apparatus, the first transport cylinder, the compressor star and the filter outlet star. In this case, the air in the transport cylinder at a pressure of 150 atm, after passing through the compressor, goes through the filter coil-refrigerator to the dehumidifier, then to the adsorber and ceramic filter. After the ceramic filter, the air enters the filled cylinders of the apparatus through the outlet star until the pressure in the entire system is equalized. The onset of this moment must be monitored by the pressure gauge on the compressor star and filter star. The cessation of bypass air hiss is also a sign that the pressure in the cylinders of the device has become the same as the pressure in the transport cylinders and will be below 150 atm. The increase in air pressure in scuba cylinders up to 150 atm is carried out by an oxygen compressor of the KN type or by a PZUS installation.
It should be noted that with the help of a compressor of the KH type, it is possible to increase the pressure by no more than two times in comparison with the pressure remaining in the transport cylinder.
If it was not possible to bring the scuba pressure up to 150 atm from the first transport cylinder, you should switch to the second transport cylinder, and then to the third. In this case, transport cylinders with high pressure are used last. After the pressure in the transport cylinders has decreased so much that it makes no sense to carry out further pumping from them, you need to replace them with full ones. By the end of charging, scuba cylinders heat up somewhat, but after a while they cool down, as a result of which the pressure in them decreases by about 10%.
Subsequently, if necessary, the cylinders of the apparatus can be recharged to a full pressure of 150 atm.
To clean the air from mechanical impurities, water and oil, an oil separator is provided on the compressor unit. It is a steel cylinder with a drain valve.
The principle of operation of the oil separator is as follows: air, entering the oil separator bottle, changes its direction, as a result of which oil particles and other particles contained in the air settle to the bottom of the bottle and, as they accumulate, are removed through the tap. The purified air exits through the opposite fitting.
In addition to such a filter, an activated carbon filter is needed to purify the air from foreign gases.
It should be remembered that scuba cylinders must be filled with absolutely clean air, that is, free from any impurities (carbon oxides, lubricating oil vapors, their oxidation products, foul-smelling substances, etc.).
The most dangerous is the content of carbon monoxide (carbon monoxide) in the air, which is found in large quantities in the exhaust gases of engines that drive the compressor. The presence of even a small amount of carbon monoxide in the air can cause swimmer poisoning. Therefore, air quality should be given special attention.
To purify air from impurities, a portable filter OKN-1 is successfully used, designed to purify and dry oxygen from moisture (Fig. 27).
To do this, alumina (drying agent) in the filter adsorber is replaced with ordinary activated carbon, which is used in gas masks. The OKN-1 unit has dimensions of 480x500x240 mm and consists of a dehumidifier, an adsorber, a ceramic filter and an output star.
Moisture Separator is designed to release air from dripping moisture. It works on the same principle as the PZUS oil separator.
The adsorber serves to purify the air from gases and is a small-capacity cylinder4 filled with activated carbon.
The ceramic filter is used to purify the air from activated carbon dust. Its body is made in the form of a glass into which a ceramic cylinder is inserted.
The OKN-1 filter reliably cleans the air from harmful impurities, except for carbon monoxide.
Some athletes also successfully use a homemade filter (Fig. 28).
Rice. 28. Scheme and dimensions of homemade
filters: 1 - activated carbon; 2 - adsorber; 3 - mesh
AUXILIARY EQUIPMENT
A handheld depth gauge is required when diving to great depths or when the dive site is completely unfamiliar. It is very important that the depth gauge has divisions over 40 m. If the divisions end at 40 m, then in this case it is not clear whether you have dived 40 m or much deeper.
There are two types of depth gauges: mechanical and pneumatic. A mechanical depth gauge is similar in design to a conventional pressure gauge and is based on the principle of water pressure in a curved tube of the instrument connected to a manometric needle.
The pneumatic depth gauge is based on the principle of elasticity and incompressibility of water. Water, entering the narrow channel (capillary) of the depth gauge, compresses the air in it in proportion to the depth of immersion. The border of air and water stands out well against the black background of the scale and shows the depth in meters.
The watch is necessary for a swimmer, as the subjective sensations of time under water are different from usual ones - time goes faster under water. In addition, the watch helps to determine the time spent under water and the time before rising to the surface. In addition to specially made underwater watches, ordinary wristwatches enclosed in a sealed case are used for diving.
The knife is not a weapon of defense, since, according to veterans of underwater sports, not a single sea creature attacks a person, but just in case, it is necessary to have it. A knife is needed, for example, in order to quickly cut off a tangled signal end, a cable or a fishing net that a swimmer can fall into, as well as for many other unforeseen accidents under water.
The knife can be floating. Such a knife is convenient for a diver with a mask, who, in case of loss, can easily find it on the surface of the water. But for a scuba diver, this is completely unprofitable, since when a knife floats to the surface, you need to follow it and then dive again. And for a diver, such frequent pressure changes are harmful.
Immersion suit serves to protect the swimmer's body from the effects of the surrounding aquatic environment, mainly from low temperatures. In the southern seas at the height of summer, you can briefly dive without a protective suit even to 40 m.
But already at a depth of 20 m, the cold is rather difficult to bear, especially for thin people. And despite the fact that protective clothing to a certain extent restricts the movement of an athlete, it significantly lengthens the season of stay under water in the southern reservoirs and ensures immersion in northern reservoirs at a water temperature of +6 ... + 8 °. To do this, a set of warm (woolen) underwear, fur socks, a woolen hat and gloves are usually put on under the wetsuit.
The main requirements for protective clothing are: reliable isolation of the body from water cooling; freedom of action under water of the arms, legs and body; ease of dressing and undressing; the absence of coarse seams, fasteners, buttons and other details that can cause abrasions of the body when moving underwater; small weight and volume.
The athlete must wear thermal protective clothing that strictly corresponds to his height. Wetsuits that restrict movement or are too spacious should not be worn, as air will be trapped in their folds, which will make it difficult to go to depth.
The correct fit of the suit determines the success of the dive.
Known suits made of sponge rubber and worn on the naked body. Although they are not waterproof, water does not enter the suit or only a small amount does.
Some costumes are made up of two pieces; others take the form of long or short sleeved jumpsuits with zippered trousers. These costumes are easy to put on yourself, without outside help.
Good waterproof suits made of thin rubber (Fig. 29), under which they put on warm underwear. The suit may consist of a shirt and trousers, connected at the waist, or be a one-piece jumpsuit with an elastic collar through which you have to get into the suit. Such impervious suits are very good protective equipment, but they are pressure sensitive and can squeeze the swimmer unpleasantly at depth.
VEHICLES UNDERWATER
An underwater aquaplane (underwater plane) is a light board 60-70 cm wide and 20-25 cm long with a handle, which the athlete holds while in a horizontal position. An underwater aquaplane is towed by a boat (Fig. 30).
An underwater aquaplane is both a rudder and a rudder. Starting from the minimum speed of the boat and ending with 4-5 km / h, a swimmer, when moving behind a hydroplane, can develop strength, agility and orientation under water. By attaching a movie camera to the aquaplane and pulling out the control stick, the underwater swimmer will be able to shoot in an influx.
Underwater sleds are used to tow a scuba diver with a movie camera along the bottom, which has a flat relief. In order to avoid sharp shaking, the sled must be massive enough.
An underwater bicycle (aquaped) is used to move an athlete under water. It is a comfortable sports apparatus and has a buoyancy close to zero. Two propellers with a diameter of about 500 mm, rotating in different directions, or one propeller with a diameter of 700 mm is driven by pedaling. On fig. 31 shows one of these devices.
The underwater scooter among other means of transportation under water has become the most widespread. In appearance, it resembles a small torpedo with one or two propellers driven by an electric motor. Batteries serve as a power source. Propellers can be located both in the stern and in the bow of the scooter with a corresponding change in the direction of rotation. The swimmer holds on to the frame in the stern and by turning his body, and especially his legs with fins, gives the scooter the desired direction of movement. The scooter can carry film equipment, as well as underwater lights.
In this sense, the underwater scooter designed by the cameraman A.F. Leontovich is interesting (Fig. 32 and 33). The scooter has a length of 235 cm, a diameter of 40 cm and a weight of 150 kg. Its underwater speed is from 2 to 6 km/h. Motor power 800 watts. The power source is a dual block of silver-zinc accumulators STs-45, which provides a total capacity of 90 Ah. The tightness of the housing at the exit of the propeller shaft is provided by stuffing box seals. The design uses standard ball bearings. The speed switch has five positions and is brought out in the form of a lever on a common handle. Case material - steel. The scooter has a negative buoyancy of about 200-300g. To ensure an emergency ascent, a safety weight is used, which is separated using a handle.
One of the following equipment can be mounted on the scooter: a) a spotlight for search work or for illumination when filming with a movie camera from another scooter; b) film cameras "Konvas-avtomat" with 60 cassettes; c) a container with accumulators and two lighting lamps with their inclusion brought to a common control knob. A flat mirror can be mounted in the bow of the scooter for passing through.
Several modifications of the scooter are known abroad, named after its designer (Rebikov's film torpedo - Fig. 34), and a number of designs of large scooters capable of carrying several swimmers in addition to film equipment.
Underwater car (akvakeb) - midget sports submarine with a waterproof hull. Its crew is in underwater sports equipment. The underwater car allows you to move at speeds up to 3-5 km / h with a pedal drive and up to 7 km / h with an electric motor. All control of this unit is located on the steering wheel. The necessary stability and buoyancy of an underwater vehicle is achieved using solid ballast. The swimmer's head is protected from counter water resistance by a folding plexiglass shield (Fig. 35).
Floating base - this is how the operator F. A. Leontovich called another design, which he created together with a team of designers led by engineer D. M. Brylin.
In appearance, the floating base resembles a double boat - a catamaran (Fig. 36) and consists of two streamlined aluminum pontoons, between which there is a cargo area. To ensure unsinkability, the pontoons are divided into sealed compartments.
The dimensions of the floating base are: length 5 m, width 3 m, pontoon height 65 cm, draft 25 cm. The total weight of the base is 150 kg, the carrying capacity is about 2 tons. The Moskva motor is suspended from the base platform. The floating base has a ladder for descending the scuba diver into the water, as well as a suspended underwater platform from which the survey is made. To raise and lower the camera overboard, the base is equipped with a special lifting boom.
BASIC RULES FOR SWIMMING UNDERWATER
The ability of a cameraman underwater is largely determined by his equipment.
With a snorkel, mask and fins, the swimmer can shoot down while moving on the surface of the water.
A cameraman equipped with scuba gear can stay under water for a long time and swim in any direction. Equipped with weights for stability, it can move on the ground.
How to put on equipment? Lightly wipe the mask glasses from the inside. Then rinse the mask in water and put it on. The fins must first be moistened so that they can be easily put on the feet. If you are wearing wetsuits, wet the inside of the fins with soapy water. Soapy water will also help with pulling the tight rubber cuffs of the wetsuit over your arms.
Put on the wetsuit slowly, trying to avoid the formation of wrinkles and cavities with air.
Scuba gear on the back should be fastened tightly, without sagging, the straps should be well tightened. The presence of the lower (breast) strap during swimming is mandatory, as it reliably holds the device from distortions.
Descent into the water. For descent into the water, it is best to have a convenient portable ladder (ladder), which could be used both from the pier and from the side of the boat. However, you often have to do without a ladder.
In any case, it is not safe to jump into the water, because when hitting the water, the cylinders can move, and the diver risks being hit by a lung machine in the back of the head. In addition, during a sharp entry into the water, the mask can be shifted from the face.
When descending from an open boat, sit on board with your back to the water, tilt your head to your bent knees (i.e., curl up) and gently tip back with your hands on your mask. This fast and safe way of diving has been proven in many underwater expeditions. Plunging from a pier or from a steep bank, you should do otherwise. Sit facing the water, dangle your legs, and then turn around, transfer your weight to both hands and lower yourself into the water as smoothly as possible.
Don't forget to put a mouthpiece in your mouth before diving into the water. Many beginners forget to do this. If you went into the water, forgetting about the mouthpiece, do not be alarmed. Staying on the surface, remove water from the corrugated tubes by vigorously blowing air into the mouthpiece.
No matter how many swimmers will accompany you in the water, someone must always remain on the shore or in the boat as a belayer. It is he who must pass you an underwater movie camera or illuminator into the water.
Take the equipment only after you are in the water, make sure that everything is in order and the scuba gear is working properly. Before the start of systematic dives, the group should distribute all scuba gear for each diver in order to properly adjust, care for and know the features of each device.
If the camera has removable planes - wings and under water you will have to move at high speed in tow (behind an underwater aquaplane or towing vehicle, behind a fishing trawl, etc.), then the wings should be removed in advance, since at the slightest angle of inclination of the camera they will create large hydrodynamic resistance, the force of which the device will twist out of the hands. For work at high speed (up to 6 km/h), cinema cameras enclosed in streamlined spherical boxes, mounted on a towing vehicle before filming, are convenient.
Towing a scuba diver in ordinary equipment at a speed of more than 6 km/h is not recommended, since the increased resistance of the water environment makes it impossible to control the underwater movie camera, pulls the mouthpiece out of the mouth, squeezes the corrugated breathing tubes, or simply rips the swimmer off the aquaplan or trawl.
Movement under water. You don't have to be a good swimmer to move underwater. A mask, fins, and even more so aqualung give an extraordinary feeling of safety in the water, and a person feels like a fish. To move around, a slow movement of the legs in a crawl style is enough.
Swimming with a mask on the surface and breathing through a tube, you should carefully observe what is happening in the water. As soon as something interesting appears in the field of view, you need to pick up speed, while breathing quickly and very deeply, so that the blood is saturated with oxygen. Then, during one of the exhalations, which should not be done to the end (it is necessary to leave a little air in the lungs in order to blow out the water that has entered the tube when ascending), you need to dive head down, continuing to work with your feet. In this case, you need to try to make gentle movements and shake the water as little as possible.
By training, you can bring the diving depth to 7-8 m. You should not go deeper without scuba gear.
When scuba diving, movements should also be slow. Remember that you are inhaling and exhaling through the same small hole in the mouthpiece. Therefore, it is necessary to avoid a sharp transition to rapid breathing, because it can lead to suffocation. Moreover, one should train to remain motionless under water for as long as possible, which is necessary to improve filming conditions.
It is desirable that the film camera in the water has zero buoyancy. In this case, it will be quite easy to manage it. However, small deviations in one direction or another do not matter much.
For shooting underwater, it is best to look for places with a rocky bottom, as they are the most expressive and the water in them is more transparent.
When you are exploring a sunken ship or a cramped underwater cave with a movie camera, always be aware of the presence of corrugated breathing tubes that are located behind your head. Sharp contact with sharp protruding parts can damage them.
Before entering any narrow passage, it must be carefully examined. Such surveys should be done at least together.
Exit from the water. First, pass a movie camera on board the boat or into the hands of a comrade standing on the gangway. Then, having previously removed from the belt and passed the breathing tube, remove the scuba, holding the mouthpiece in your mouth. Fins do not need to be removed, they make it easier to get out of the water. The mask is removed last.
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