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Diving Suit. A diving suit is a garment or device designed to protect a diver from the underwater environment.Modern diving suits can be divided into two kinds: "soft" or ambient pressure diving suits - examples are wetsuits, drysuits, semi-dry suits and dive skins "hard" or atmospheric pressure diving suits - an armored suit that permits a diver to remain at atmospheric pressure whilst operating at depth where the water pressure is high. Standard diving dress is now obsolete but is historically interesting. Ambient pressure suits:There are five main types of ambient pressure diving suits: wetsuitsdrysuitssemi-dry suitsdive skins Apart from hot water suits, these types of suit are not exclusively used by divers but are often used for thermal protection, by people engaged in other water activities such as surfing, sailing, powerboating, windsurfing, waterskiing, cavingswimming. Ambient pressure suits are a form of exposure protection protecting the wearer from the cold. They also provide some defence from abrasive and sharp objects as well as potentially harmful underwater life. They do not protect divers from the pressure of the surrounding water or resulting barotrauma and decompression sickness. The suits are often made from Neoprene, heavy-duty fabric coated with rubber, or PVC.Added buoyancy, created by the volume of the suit, is a side effect of diving suits. Sometimes a weightbelt must be worn to counteract this buoyancy. Some drysuits have controls allowing the suit to be inflated to reduce "squeeze" caused by increasing pressure; they also have vents allowing the excess air to be removed from the suit on ascent. Wetsuits are relatively inexpensive, simple, Neoprene suits that are typically used where the water temperature is between 10 and 25 °C (50 to 80 °F). Drysuits are used typically where the water temperature is between -2 and 15°C (28 to 60°F). Types:There are two types of drysuit: Membrane dry suits are made from thin materials, with a consequent poor thermal insulation,
such as vulcanised rubber or from laminated layers of nylon, butyl rubber and nylon. The diver must wear an insulating undersuit. Membrane drysuits are comfortable to put on, get off and wear. They can be unreliable because the suit’s buoyancy and insulation depends on the gas trapped in the under suit: if the suit is punctured the buoyancy and insulation is lost. In warm waters some divers wear a membrane drysuit without an undersuit. Some divers wear a wetsuit under the drysuit instead. Membrane drysuits may also be constructed with a waterproof and breathable membrane to enable comfortable wear for periods out of water. Neoprene dry suits are constructed from Neoprene, a buoyant and thermally insulating material.
This built-in buoyancy and thermal protection makes them safer to wear than membrane dry suits when punctured because they keep some of those properties when flooded. Being made of a fairly rigid heavy material, they are difficult to get on and off, and their buoyancy and thermal protection decreases with depth as the Neoprene is compressed. Neoprene also tends to shrink over the years. An alternative is crushed Neoprene, which is less susceptible to volume changes when under pressure and shrinks less. Parts of a drysuit:Normally, the gas used for drysuit inflation 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. Pure argon cannot be used as a breathing gas.
Alternatively, some trimix divers inflate their suits from a decompression cylinder containing a nitrox blend. Seals at the wrists and neck prevent water entering the suit. Even so, the diver will be damp after a dive in a drysuit due to sweat and condensation.
The seals are either made from latex rubber or Neoprene. Latex seals are supple but survive for a maximum of about two years before they must be removed from the suit and replaced.
Neoprene seals last longer but let more water enter because, being stiffer, they do not make effective seals in the contours of the wrist and neck.A modern diving drysuit has a gas inflation valve,
which lets the diver control the buoyancy of the suit by injecting gas from a diving cylinder to avoid "squeeze" during descent.
Some old-type frogman's drysuits had a small "jack cylinder" to be inflated from, or the frogman
(who was using an oxygen rebreather and so limited to about 30 feet (10 m) depth) had to put up with the suit squeeze.
A typical drysuit has an air vent valve, which lets the diver vent off higher pressure gas from the suit during the ascent.
Vent valves can be automatic, operating as pressure relief valves, or manual, where the diver must raise the valve to vent.
Automatic vents are generally located at the shoulder and manual vents are located at the wrist.
Some drysuits have no vents, but the diver must pull one of the wrist or neck seals open to vent the drysuit.
Modern drysuits have a waterproof zipper, for entry and exit, across the back of the shoulders, or diagonally across the front of the torso,
- or straight down the middle of the front. Before the invention of waterproof zips other methods had to be devised;
- at least one make of old-type British frogman's drysuit was one-piece with a wide neck hole for entry;
- the bottom of the hood and the edge of the suit's neck hole were clamped together by a large circular steel clamp around his neck;
- there was a watertight seal in the bottom of the hood.Most drysuits have built-in boots, but some have ankle seals instead.
Semi-dry suits:Semi-dry suits are used typically where the water temperature is between 10 and 20°C (50 to 70°F).
- They are effectively a thick wetsuit with better-than-usual seals at wrist, neck and ankles.
The seals limit the volume of water entering and leaving the suit.
The wearer gets wet in a semi-dry suit but the water that enters is soon warmed up and does not leave the suit readily, so the wearer remains warm.
The trapped layer of water does not add to the suit's insulating ability.
Any residual water circulation past the seals still causes heat loss. But semi-dry suits are cheap and simple compared to dry suits.
They are made from thick Neoprene, which provides good thermal protection.
They lose buoyancy and thermal protection as the trapped gas bubbles in the Neoprene compress at depth.
Semi-dry suits can come in various configurations including a single piece or two pieces, made of 'long johns' and a separate 'jacket'.
Semi dry suits do not usually include boots, so a separate pair of insulating boots are worn. - Dive skins:Dive skins are used when diving in water temperatures above 25°C, 77°F.
They are made from Spandex and provide little thermal protection, but protect the skin from stings and abrasion.
This kind of suit is also known as a 'Stinger Suit'.
Hot water suits are used in cold water commercial surface supplied diving.
An insulated pipe in the umbilical line, which links the diver to the surface support, carries the hot water down to the suit.
The diver controls the flow rate of the water from a valve near the diver's waist. Pipes inside the suit transport the water to the limbs,
front of the torso and back of the torso. - Diving suit combinations:
- Some divers wear a wetsuit under a membrane drysuit.
- Some divers wear a thin "shorty" wetsuit under a full wetsuit.
- Some divers wear a "skins" under a wetsuit. This practice started with divers (of both sexes)
- wearing women's body tights under a wetsuit to get a bit of extra warmth.
PADI 5 Star National Geographic Instructor Development Center. 198/12 Rat-U-Thit Road, Patong, Phuket, Thailand. Phone: (+66) 076292052 Fax: (+66) 076293034
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