zngmqk19
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 Posted: Sun 19:22, 20 Mar 2011 Post subject: dry suit has an air exhaust valve ed hardy [...] |
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A typical diving dry suit has an air exhaust valve, which lets the diver vent gas from the suit during the ascent.[link widoczny dla zalogowanych] This is necessary because when the diver ascends, the air in the suit expands,[link widoczny dla zalogowanych], balloons out the suit, and hinders movement. The air in a ballooned suit can overcome the diver's neutral buoyancy, and can cause a sudden uncontrolled ascent to the surface, resulting in decompression sickness and loss of consciousness.
Vent valves can be automatic, operating as pressure relief valves, or manual, where the diver must raise the valve to vent.[10] Automatic vents are generally at the shoulder, and manual vents are at the wrist. Some older dry suits have no vents, but the diver must lift one of the wrist seals or the neck seal open to vent the dry suit. Surface dry suits are not inflated, and must be vented to remove most of the gas inside.
Because the air inside the suit is compressed as the diver descends, a modern diving dry suit also has a gas inflation valve, which lets the diver control the buoyancy of the suit by injecting gas from a diving cylinder to avoid the suit from being squeezed tightly and painfully onto the diver's body during descent.[link widoczny dla zalogowanych] The sensation is similar to being pinched, but all over the body. Suit squeeze can also hinder the diver's movement and make swimming more difficult.
Some old-type frogman's dry suits had a small "jack cylinder" from which they could be inflated. Otherwise the frogman (who was using an oxygen rebreather, and so limited to about 30 feet (9.144 m) depth), had to put up with the suit squeeze.
Normally, the gas used for dry suit inflation for diving is air from the primary breathing cylinder. When divers breathe helium-based gas mixes such as trimix, they often avoid inflating their suits with the helium-based gas due to its high thermal conductivity. They often carry a separate cylinder for this purpose; generally it contains air, although sometimes argon, which has lower thermal conductivity, is used.[11][12] Alternatively, some trimix divers inflate their suits from adecompression cylinder containing a nitrox blend (all such decompression blends, including pure oxyten, have essentially the same thermal conductivity as air).
In surface dry suits,[link widoczny dla zalogowanych] the wearer normally never dives deeply underwater, and is not concerned about neutral buoyancy, so there are no air valves on a surface dry suit.
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