Twin, sidemount cylinder, rebel cylinder, stage, bailout, poniak, spairair, argon cylinder
In addition to the single cylinders typical in recreational diving, divers sometimes use cylinder sets consisting of several cylinders. The goal is to take more breathing gas underwater, duplicate cylinders in case of an emergency, take different gases underwater during technical dives.
Twin
The set, popularly known as a twine, consists of two cylinders, most often 12 liters, connected by a so-called manifold, a connector that allows both the collection of gas, by any of the two automats connected to the valve of one of the cylinders of the twine, or their full separation allowing the preservation of gas from at least one cylinder in the event of failure and escape of gas from the other cylinder.
Twins come in versions with cylinders ranging from 6 to 18 liters, depending on the needs of the diver, but the most popular are the 12-liter ones.
Twins can be based on cylinders with working pressures of 200 atm – the most popular, and with working pressures of 300 atm to take more gas – this is more common for kits consisting of smaller cylinders; 6 to 10 liters.
A twin provides more gas underwater by taking two connected cylinders, but the primary purpose of using a twin is the diver’s need to ensure that the breathing gas delivery system is duplicated, which is especially important in deep dives and in dives where quick access to the surface is not possible, such as decompression dives, cave dives, wreck dives with interior penetration of wrecks. The idea of a typical Twin, as opposed to two independent cylinders, is a separation manifold that allows the two cylinders to be separated on the one hand, but at the same time gives the possibility to use the gas in both cylinders with the valve on one of them closed. At the same time, relative to the two independent cylinders, the manifold has two features that can be disadvantages under certain conditions. In the very unlikely event of a separator failure, it can deprive us of gas from both cylinders, so manifolds are better for partner diving where we can rely on a partner for support as a last resort. If you are diving alone two completely independent cylinders will be a more reliable solution.
The second feature of the twine is that the cylinders are connected permanently, so they must be carried together which increases the load when transporting, hauling to the boat, transporting to a more distant water entry point. In such situations, sidemount cylinders may be a better option.
To ensure that the diver operates at least one automatic, during a failure of the automatic or the valve on the second cylinder of the twine, requires turning the knob of the separator located at the back at neck level. This requires a certain degree of skill trained in technical courses. In addition, because the manifold gives you the ability to turn off the valve at the automaton that has failed, the ability to turn off the valve on the cylinder behind you needs an even better stretch than to turn off the manifold separator. Ideally, manifold valves require fewer turns of the valve knob to close them. Good manifolds with properly made valves allow the valve to close in 2.5-3 turns. Also important is the resistance of turning the valve knobs – this should be checked with the twine inflated, as the resistance of some valves increases strongly as the pressure increases.
The two cylinders of the twine are connected by hoops, which should be made of fairly wide stainless steel strip. These hoops are connected by screws whose standard distance between each other allows the twine to be attached to the diver’s plate and harness.
The kit described here had the cylinder valves facing up. In recreational or technical diving, this is standard. However, in military, firefighting or underwater applications, it is more common to see cylinder sets attached to the diver’s back so that the cylinders face down with their valves. This makes it easier for the diver to access the valves for it makes it more difficult to place the kit when dressing it.
Sidemount Cylinders
Sidemount cylinders are two cylinders adapted for diving in a sidemount harness. Apart from the harness, the only feature that distinguishes them from normal cylinders is the symmetry of the valves. One of the cylinders (left) has the valve knob facing left as seen from the DIN thread side, the other cylinder (right) has the valve knob facing right as seen from the DIN thread side. This makes it easy for divers to operate the right valve with the right hand and the left valve with the left hand after hanging the cylinder on the harness rubbers. In addition, for easier hooking of harness rubbers around the valve, sidemount cylinder valves have a special protrusion on the opposite side than the valve knob, In practice, these are blinded on one side of the jumper for the twine’s manifold (only without the manifold).
Sidemount cylinders are made of aluminum or steel, and this choice has certain consequences. Steel cylinders have negative buoyancy all the time regardless of the amount of gas consumed during the dive, so they always lay similarly on the harness and do not need to be rewired. However, if the diver takes into account their negative weight when balancing them, he cannot remove them from the harness during the dive.
Aluminum cylinders full sink and empty ones float. Therefore, in order for them to align similarly along the diver’s body throughout the dive, it is necessary to rewire their attachment from the foot side of the cylinder during the dive, which is a certain additional activity. However, since they are not involved in balancing the diver, the diver can completely unhook them underwater, maintaining neutral buoyancy.
Reb cylinder
A rebowa cylinder is usually a 2-3 liter cylinder or actually a set of two such cylinders for oxygen and diluent. Clearly, usually permanently marked and labeled. Right oxygen cylinder labeled Oxygen (Oxygen) left cylinder labeled Diluent and additionally labeled with the current mixture composition and MOD.
Stage
Stages are cylinders whose purpose is to take on a dive, additional bottom, decompression or emergency gas. The word “Stage” is taken from the cylinders left for the diver’s return, but in practice most often stages are “carried” by the diver all the time. There may be bottom gas in the stage for extended bottom diving time. There may also be gas that we do not plan to use in practice unless the failure of other cylinders or the reba forces us to use emergency (bailout) gas. However, there is usually gas in the stega’s for decompression. These cylinders are clipped to the dering of the harness, so they are generally equipped with their own harness with carabiners.
Bailout
Bailout is a stage used by rebreather divers, to take the gas needed for ascent and decompression in case of rebreather failure. In non-decompression diving, it’s one cylinder of bottom gas. In decompression diving, it’s a set of several cylinders of bottom gas and decompression gases in quantities that allow for a safe ascent and decompression.
Poniak
A poniak is an additional small cylinder (2-3 liters) usually attached to the main cylinder by a separate strap. It has its own separate automatic and acts as an escape cylinder, that is, for emergency ascent. Once a very popular solution, now since stages are readily available, it is less frequently used as is Spai air.
SpairAir
An additional tiny cylinder (0.25-0.4 liters) with an automatic device integrated into the cylinder valve. Cylinder attached, for example, to the leg or belt of the Jacket. It allows you to take several breaths during a smooth emergency ascent.
Argonics
An argon tube is usually an air-filled small bottle designed for blowing a dry suit. Its name came from the fact that some divers, in order to increase the heating properties of the dry suit, filled it with argon gas rather than air from the main cylinder. Argon tubes are usually 0.75 to 1.5 liters in capacity, which allows for one to three dives. Nowadays when electric heating has virtually completely supplanted the use of argon; argon ki is experiencing a second youth in trimix diving. Most divers don’t want to fill dry suits with trimix from the main cylinders so they fill them with air from “argon tubes.” Since the dive sites to which one flies by airplane usually have twins and sidemount but rarely argon ki cylinders at dive bases; then the transport of argon ki through airport security systems is a separate modern “urban legend” so much so that diving.
