Buoyancy compensator
The buoyancy compensator , also known as a jacket or BC (Buoyancy Compensator) or BCD (Buoyancy Control Device), is part of the diving equipment . With their help, by blowing in or releasing air , the diver can regulate his buoyancy and balance it out at any depth . The buoyancy compensator also serves as a carrying frame for the compressed air cylinder . On the surface of the water, the inflated buoyancy compensator helps the diver to stay afloat, but the majority of buoyancy compensators are not life jackets , which reliably prevent injured or unconscious people from drowning.
Structure of the BC
A buoyancy compensator consists of different components: The buoyancy body takes on the main function, buoyancy of the diver in order to keep him at the desired depth or so that he can sink and climb. The straps are used to attach and adapt the jacket to the body of the diver. The jacket is also the carrying unit: the breathing system, consisting of a regulator and a diving bottle, is attached to the back of the jacket .
Floats
The buoyancy body of a buoyancy compensator is made up of two layers: the outside is usually made of sturdy nylon fabric (Cordura), and inside there is an air bubble. This can be filled and emptied, depending on the type of BC, it has a volume of 15 to 45 liters . The designation vest best describes the design of this piece of equipment: When worn like a sleeveless vest, it encloses the diver's upper body and is closed in the front area of the diver.
Certain designs such as the ADV jacket or the hybrid jacket not only have a bladder in the back area, as is the case with the wing jacket , but also have side areas that are also filled with air as part of the float. Often jacket pockets are integrated in these, which are closed with Velcro or zip . In the shoulder area, on the side panels and also on the lower edge of the buoyancy compensator there are mostly D-rings - depending on the features of the respective jacket ; These are larger and smaller eyelets in the shape of the letter D made of metal or plastic for attaching equipment such as diving torches , underwater cameras , octopus and much more.
Belting
All jackets are attached to the diver's abdomen in the abdominal area; this hip or abdominal belt is often carried out twice: Two wide, mostly flexible textile flaps, called cummerbunds , run close to the abdomen and are connected with Velcro . In addition, an adjustable strap with a quick release buckle secures the connection. Some jacket models do without the fixation by means of a 'cummerbund', mostly for reasons of weight, but this does not entail any disadvantage in terms of safety or comfort. In the chest area, adjustable chest straps are also mounted on some models to hold the buoyancy compensator together in the upper area. Adjustable shoulder straps lead from the shoulder to the side panels, with which the buoyancy compensator can be adjusted to the size of the diver. In some models, but especially in designs such as the Wing Jackets or Tec Jackets, there is also a crotch strap that is attached to the lower back area and leads to the front, where it is connected to the hip belt. This prevents the equipment from slipping in the upside down diving position.
Back shell, back carrier
The carrying shell forms the back of the BC. This is either rigidly made of plastic or metal, in the case of particularly light jackets, mostly travel jackets, made relatively flexible from padded fabric. With a bottle strap , a special form of a tensioning strap, the diving bottle is attached to the backpack and thus to the jacket. Some models also have two of these bottle straps. The support surface of the bottle facing the diver is often padded to make carrying the heavy device a little more comfortable.
Corrugated hose / inlet valve / inflator system
In conventional systems, the inflator hose is connected to the air bladder on the left shoulder . It is a corrugated hose, at the outer end of which there is a connection for the medium pressure hose coming from the first stage of the regulator, an inlet valve that controls the air supply from the regulator to the buoyancy compensator, a drain valve for venting the Buoyancy compensator and a mouthpiece for inflating the buoyancy compensator with your mouth. The corrugated tube enables the diver to hold the drain valve above himself when deflating the buoyancy compensator so that the air, which is constantly rising, can escape unhindered.
Drain valves
As mentioned, air always rises. Therefore, the highest vent valve always allows air to be vented and the diver's position under water must comply with this physical law. For this reason there are several drain valves on jackets: Some buoyancy compensators have a quick drain integrated in the corrugated tube. By pulling on the inflator hose, the drain valve on the left shoulder is operated via a pull rope, which allows the BC to be vented. On the lower back of the buoyancy compensator there is another drain valve that allows venting with the head down when diving. A third drain valve sits on the right shoulder and, like the back valve, is usually operated directly. These valves also function as pressure relief valves so that the air bubble cannot be damaged if too much air is let in. This can be done through human error, but also if the filling unit, the inflator, is defective and does not interrupt the air supply.
Inlet valve / indeflator system
Some newly developed buoyancy compensators do not have the corrugated tube and are replaced by integrated inlet and outlet valves. This system is also known as the indeflator system , although this designation has not yet been standardized. There are currently three forms of integrated control of the valves on the market: mechanically via rods, hydraulically via oil-filled hose connections and pneumatically using compressed air.
The main argument for this inflator-free valve control is that the annoying, hanging corrugated hose is no longer necessary and the control unit can always be found in the same place - in contrast to the dangling inflator hose. The float can be vented in almost any diving position; the diver does not need to stand upright, as is necessary, for example, for venting via an inflator hose .
The main argument against this integrated valve control is that the inflator unit can no longer be brought to the mouth as with the corrugated hose, in order to manually fill the jacket if the diving cylinder loses pressure. For this emergency, however, indeflator systems have a small tube that can be filled with air by mouth. However, the practical suitability is clearly limited compared to the corrugated tube. Against this, the fact that the operation of the corrugated hose is a standardized learning procedure in diving training and that a helping diving partner is very likely to be familiar in an emergency is also an argument. The operation of the indeflator, on the other hand, should be explicitly discussed prior to the dive.
Corrugated tubes in general
Corrugated tubes are used in the diving area on buoyancy compensators as described above. But corrugated hoses were also used on the two-hose machines that were used in the past. A corrugated tube, although flexible, should not be subjected to excessive loads or kinked during transport.
Types
There are four types of construction:
ADV jacket
The most common form of the BC is the Adjustable Divers Vest (ADV; 'adjustable diving vest'). ADV jackets have a stable, mostly plastic back carrier on the back, to which the bottle is attached with the help of one or more straps. Most of the buoyancy bladder is located under the arms in the diver's hip area, a small part around the back carrier in the back of the jacket up to the shoulders. There are many models of this type of jacket, some of which differ considerably in terms of their features. ADV jackets can be easily adjusted individually; the buoyancy is less than with stabilizing jackets.
Wing jacket
Wings only have a float on the back, which makes diving in a horizontal position easier. This can be detrimental on the surface, as the diver's face (in the prone position) is pushed into the water. Due to the mostly large air bubble, the buoyancy that is usually superior to other types of construction, as well as the free upper body on the front and sides, wings are often preferred by divers who carry a lot of equipment with them, e.g. B. Tec divers . However, the term "wing jacket" in the narrower sense is only used when the buoyancy bladder, back plate and harness are connected to form a monolithic unit.
Hybrid jacket
Combines the advantages of both previous designs. It offers a larger volume than the ADV jacket, but usually cannot achieve the superior buoyancy of the wing jacket. The swimming position under water is just as stable and optimal as with the wing, but without sacrificing the comfort of an ADV jacket (especially on the surface). Hybrid jackets tend to be a bit larger and heavier overall and are therefore not necessarily ideal for small luggage - but the diving industry tries to offer solutions here too.
Stabilizer jacket
Has continuous buoyancy compensator tubes on the shoulders and behaves similarly to the ADV jacket when diving. Some models of this type are said to be "faint-proof" and accordingly meet certain safety requirements. In the field of sport and recreational diving, however, stabilizer jackets are rarely found, as their disadvantages (among other things, voluminous, sometimes more complex harnessing and restricted freedom of movement) usually predominate. Another major disadvantage of this type of jacket is that it is very difficult to put on and take off. You really have to be able to bend to get into the jacket, as you can't fully open the straps. In addition, the available size range is very narrow. It has to fit almost 100 percent when you buy it; and with a greater weight gain, e.g. B. after pregnancy, the jacket often has to be taken out of service.
General
The jackets can also have built-in weight pockets that hold the ballast instead of the weight belt . This can reduce the stress on the spine. Basically, weight pouches are now designed in such a way that they can be thrown off quickly in an emergency.
A jacket should always be the right size for the respective user. A jacket that is too large does not fit well, so that the bottle does not lie firmly against the body and the diver can tilt. If the jacket is too small, the weight pockets do not sit optimally and buoyancy is usually lost. In case of doubt, such as when the user is between two sizes in terms of body measurements, the smaller jacket should be chosen, as the disadvantages are not as serious as those of the too large.
In addition, there are special jackets with two independent air chambers, which are intended to provide additional safety, especially for more demanding dives. In practice, however, most divers rely on a dry suit which can (to a limited extent) also take over the taring function of the air chamber.
Individual evidence
- ↑ a b Thomas Kromp , Hans J. Roggenbach , Peter Brede Busch : practice of diving. 3rd edition, Delius Klasing Verlag, Bielefeld 2008, ISBN 978-3-7688-1816-2 , pp. 244–246.
- ^ Jacket types , Lothar Seveke, accessed February 6, 2012