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A dry suit or drysuit provides the wearer with environmental protection by way of thermal insulation and exclusion of water, and is worn by divers, boaters, water sports enthusiasts, and others who work or play in or near cold or contaminated water. A dry suit normally protects the whole body except the head, hands, and possibly the feet. In hazmat configurations, however, all of these are covered as well.
The main difference between dry suits and wetsuits is that dry suits are designed to prevent water entering. This generally allows better insulation making them more suitable for use in cold water. Dry suits can be uncomfortably hot in warm or hot air, and are typically more expensive and more complex to don. For divers, they add some degree of operational complexity as the suit must be inflated and deflated with changes in depth in order to minimize "squeeze" on descent or uncontrolled rapid ascent due to excessive buoyancy.
Dry suits provide passive thermal protection: They insulate against heat transfer to the environment. When this is insufficient, active warming or cooling may be provided, usually by a hot-water suit, which is a wetsuit with a supply of heated or chilled water from the surface, but it is also possible to provide chemical or electrically powered heating accessories to dry suits.
- 1 Components
- 1.1 Essential components
- 1.2 Accessories
- 2 Applications
- 3 Manufacture
- 4 Care of suit
- 5 Hazards of use
- 6 History
- 7 See also
- 8 References
The essential components include a shell of watertight material, sufficiently flexible to allow the wearer to function adequately, seals where parts of the body pass through the suit while in use, and a method of sealing the access opening while the suit is worn. Insulation may be provided in part by the suit shell, but is usually largely provided by thermal insulation clothing worn under the suit, which relies to a large extent on trapped air for it's insulating properties.
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Membrane dry suits are made from thin materials which have little thermal insulation. They are commonly made of vulcanized rubber, or laminated layers of nylon and butyl rubber. Membrane dry suits typically do not stretch, so they need to be made oversized and baggy to allow flexibility at the joints through the wearer's range of motion. This makes membrane dry suits easy to put on and take off, provides a good range of motion for the wearer when sufficiently inflated, and makes them comfortable to wear for long periods out of the water, as the wearer does not have to pull against rubber elasticity.
To stay warm in a membrane suit, the wearer must wear an insulating undersuit, today typically made with polyester or other synthetic fiber batting. Polyester and other synthetics are preferred over natural materials, since synthetic materials have better insulating properties when damp or wet from sweat, seepage, or a leak. (Except for wool, which is an effective insulator when damp, albeit bulky.)
Reasonable care must be taken not to puncture or tear membrane dry suits, because buoyancy and insulation depend entirely on the air space in the undersuit, (whereas a wetsuit normally allows water to enter, and retains its insulation despite it). The dry suit material offers essentially no buoyancy or insulation itself, so if the dry suit leaks or is torn, water can soak the undersuit, with a corresponding loss of buoyancy and insulation.
In warmer waters, some wearers wear specially designed membrane dry suits without an undersuit. These are different in design, materials, and construction from dry suits made for cold water diving.[clarification needed]
Membrane dry suits may also be made of a waterproof but breathable material to enable comfortable wear when out of the water for long periods of time. Sailors and boaters who intend to stay out of the water prefer this type of suit.
Neoprene is a type of synthetic rubber. Neoprene can be foamed during manufacture to contain millions of tiny enclosed gas bubbles, forming a buoyant and thermally-insulating material, called "foamed neoprene", "foam-neoprene" or "expanded neoprene". Foamed neoprene may be used as the fabric of a drysuit, providing some insulation due to the gas within the material, as in a standard wetsuit. If torn or punctured, leading to flooding, a foam-neoprene suit retains the insulation and buoyancy of the gas bubbles, in the same manner as in a foamed-neoprene wet suit.
Neoprene dry suits are not as easy to put on and remove as are membrane dry suits, largely due to a closer fit which is possible due to the inherent elasticity of the material, and partly due to greater weight. As with wet suits, their buoyancy and thermal protection decreases with depth as the air bubbles in the neoprene are compressed. The air or other gas in the dry fabric undergarments providing insulation under a dry suit is also compressed, but can be restored to an effective volume by inflating the drysuit at depth through an inflator valve, thus preventing "suit squeeze" and compacting of the air-filled dry fabric beneath.
Foam-neoprene also tends to shrink over the years as it outgases and slowly becomes less flexible as it ages. An alternative is crushed or compressed foam neoprene, which is less susceptible to volume changes when under pressure, and shrinks less, while retaining the elasticity which allows freedom of movement.
Foamed-neoprene dry suits provide some insulation by themselves, but even with foam drysuits, thermal under-suits are usually worn. With a thicker foamed neoprene suit, less insulation is needed underneath. The undersuits vary from a standard wet suit (worn dry), to polyester fabrics used in mountaineering and other cold weather uses (these may also be in pieces, including vests and sleeveless vests). Such fabrics also ultimately insulate in the same way as foam, using air in which convection is retarded by the small sizes of the air spaces. However, per volume and weight of fabric, the best-insulating dry polyester fabrics are more effective than foam, because their air pockets are smaller.
The combination of neoprene suit and polyester undergarment often reduces the amount of ballast needed to counteract the total buoyancy of the diver, since the total amount of air is usually less than needed for the same insulation in a membrane suit with a thicker undersuit. Notwithstanding the greater insulating power of dry fabrics, membrane suits with undersuits are a combination which usually uses the total volume of insulating air less efficiently[clarification needed] (hence uses more air for the same insulation). This is because such suits cause larger volumes of air to be present as large bubbles and spaces, and the phenomena of convection and poor distribution causes such air to be "wasted" in its value as insulator.
Hybrid suits combine the features of both types, with a membrane top attached to a neoprene bottom near the waist. The neoprene part is usually configured as a sleeveless "farmer-john" that covers the torso as well. This style is often used for surface water sports, especially in very cold water. The tight fitting lower part lets the wearer kick while swimming, and the loose fitting top allows easy arm movement. The torso covering also provides additional self-rescue or survival time if the suit leaks.
Seals at the wrists and neck prevent water entering the suit by a close contact fit against the skin around the wrists and neck. The seals are not absolutely watertight, however, and the wearer may experience some seepage during use. The wearer will also get damp due to sweat and condensation. The seals are typically made from latex rubber or foam neoprene, but are also available in silicone rubber. Latex seals are supple but easily damaged and deteriorate with exposure to oils, oxygen, and other materials, so they must be replaced periodically, every two years or more often. Latex also causes an allergic reaction in some users. Neoprene seals last longer and are non-allergenic, but, being less elastic, let more water enter because they do not seal as effectively as latex seals to the contours of wrist and neck. They are also typically glued and sewn together to form a tube, and may leak along that seam.
A recent innovation is the silicone seal, which is claimed to be as supple as latex, more flexible, yet far more durable. These are now available as original equipment on some makes of dry suit. Silicone seals are hypoallergenic, but can not be glued to the suit, and must be attached using clip-on rings. The silicone seals are similar in mechanical strength to latex seals but do not deteriorate as rapidly from oxidation and chemical attack. They are initially relatively expensive, but can be replaced without tools by the user which reduces cost of replacement.
Modern dry suits have a watertight zipper for entry and exit. The original brass-toothed version was developed by NASA to hold air inside space suits. This complex and special zipper is one of the most expensive parts of the suit. Heavy duty. medium and lightweight versions are made. A later design uses injection moulded plastic teeth, and these are lighter, more flexible and less costly. The zipper is commonly installed across the back of the shoulders, since this placement compromises overall flexibility the least—but this design normally means the wearer requires assistance to close and open the zipper. The other common zipper placement is diagonally across the torso, which allows self-donning. Other designs place the zipper on the side, straight down the middle of the back (early Poseidon Unisuit), Up one side of the front, around the back of the neck and partway back down the front (later model Poseidon Unisuit) or on a wide tubular chest entry opening which is folded down and clipped round the waist after sealing the zip (some Typhoon suits).
The waterproof-zipper is very stiff, and cannot stretch at all, which can make it difficult for a user to get into and out of the suit.[clarification needed] The zipper opening is often quite small, since a large zipper makes the suit stiffer and more difficult to use. Some complex zipper arrangements that wrap around the neck or chest let the suit swing open with a flap or hinge point. Some snug-fitting suits may also use wrap-around expansion zippers that allow the suit to expand or contract to fit different size people.[clarification needed]
Dry suits may also be fitted with an extra waterproof zipper "fly" to let the user urinate when out of the water when the suit is worn for long periods.
Before truly watertight zippers were invented, other methods of keeping the suit waterproof at the entry point were used, with the most common being a long rubber entry tunnel which would be folded shut, then rolled together from the sides and finally folded and clamped with a metal clip. An early example was the Sladen suit, where the entry tunnel was at the front of the torso. The Louisiana-based dry suit company Aquala makes a "historical" diving suit of that kind.
Another type of entry featured a rubber tunnel that protruded through a non-watertight zipper. The tunnel would be rolled shut and the zipper closed to hold the roll in place.
Some types did not use a zipper at all. At least one make of early British frogman's dry suit 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 held together by a large circular steel clamp around the neck; there was a watertight seal in the bottom of the hood. Two-piece dry suit designs in full length for year-round use and "shorty" styles for summer-season use were also common in the 1950s and early 1960s. Two-piece suits of the period include the American-made Spearfisherman frogman suit, U.S. Divers Seal Suit and the So Lo Marx Skooba Totes suit, the Italian-made Pirelli suit and the UK-made Heinke Delta suit and Siebe-Heinke Dip suit. These suits were sealed at the waist by rolling together the excess material at the bottom of the shirt and the top of the pants. A cummerbund, rail, or surgical tubing was sometimes provided to make the seal more waterproof. A modern version of the two-piece dry suit is manufactured by Customworks of Idaho. Though lacking such features as valves and zippers, these suits still have certain advantages over their modern counterparts. For example, they are cheaper, less bulky, more easily repaired and the footed pants could also be used as fishing waders.
Most drysuits do not provide sufficient insulation without suitable undergarments. The type of undergarment selected will depend on the water temperature, type of suit and dive plan. The purpose of the undergarment is to maintain the diver in comfortable thermal balance, where the heat lost is balanced by the heat generated by the diver. More insulation is needed for colder conditions and for less energetic diving activity.
The principle of layering can be used to provide a wider range of insulation possibilities from a relatively small range of underwear items, however this can only be done before entering the water. Most dry suit underwear insulates by a trapped layer of air in the garment, and this is largely lost if the air is replaced by water in a flooded suit, so as a general rule, insulation is proportional to the combined thickness of the undergarments. The layering principle shows that the option of two layers of undergarment in two thicknesses allows three levels of insulation to be selected. Thin only, thick only, and both layers.
Some materials have better insulating properties than other when wet, and will keep the diver warmer if the suit leaks or floods. The best dry suit undergarment is the thinnest material that will provide the required insulation, by trapping air in the smallest spaces. These will require less air in the suit and thus less excess buoyancy for which weighting will be required.
The moisture given off by the human body, even when not exercising and sweating, will condense against the inside of the dry duit, and the way this condensate is handled by the underwear material will influence the comfort of the diver. If the underwear soaks up this moisture it will feel cold and clammy, particularly if this layer is against the skin. Materials which wick the moisture away from the skin and do not soak up the condensate will be more comfortable.
Underwear which is flexible and stretches, particularly at the joints, will allow the diver more freedom of movement, and is less likely to chafe, and materials which resist compaction under light pressure will maintain a more even thickness in use, which will provide better insulation for the same overall volume.
Early thermal undersuits for drysuits were commonly made from wool, as it retains its insulating properties better than most other natural fibres.
For cold-water use, especially diving under ice, the user will usually wear a thick undersuit in a membrane dry suit. The thickness of undersuits varies and can be chosen by the wearer according to the water temperature. Thinsulate is one of the preferred fabrics for undersuits. The hydrophobic qualities of Thinsulate help prevent water absorption which hetps to maintain the insulating airspace even in the presence of free water. More recently, aerogel material is being added to conventional undergarments to increase the insulating properties of those garments. Polartec fleece is a good insulator with good stretch, is lightweight, and dries quickly if it gets wet. It is also hypoallergenic and comfortable against the skin. Polyester liners can add to the insulation and will wick perspiration away from the skin. Cotton is not recommended as it absorbs moisture and saturates easily, and will then rapidly conduct heat away from the body. Most dry-suit underwear is full length, either as a one piece or jacket and trousers, but a vest may be added for extra insulation on the torso.
Neoprene dry suits are made from a foam-rubber sheet containing tiny air bubbles, which provide insulation by themselves, and can eliminate the need for an under-suit, or greatly reduce the thickness needed for the under-fabric, but the bubbles in the neoprene are compressed and the insulation of the suit decreases with depth in the same way as for a wetsuit. Crushed neoprene provides the flexibility of neoprene with the consistent buoyancy and insulation of membrane suits. A neoprene wet suit can also be worn under a membrane dry suit for extra protection against condensation and leaks.
Some dry suits are provided with internall attached suspenders which when hooked over the shoulders, will hold the trouser section up when the top part of the suit has not yet been fully dressed into by the diver, this is also convenient if the suit is partly removed between dives for comfort. The suspenders also help to keep the trousers fully lifted if the torso of a membrane suit is a little long to provide enough space for the diver to bend the torso comfortably when in use. If the crotch hangs too low it encumbers the legs when finning, and increases the risk of the feet pulling out of the boots in an inversion.
Gloves, mitts, and three-finger mitts
Dry suits may have wrist seals, permanently attached gloves/mitts, or a third option known as the attachment ring (described below).
If it is not important to have exposed bare hands, permanently attached heavy rubber gloves or mitts can help make getting in and out of the suit much easier since there is no need for the suit to tightly seal around the wrists. Instead, the wearer can slip into the attached gloves as if they were a loose-fitting coat sleeve.
Full-hand diving mitts can be sometimes useful in extreme environments such as ice diving.
Three-finger mitts are a midpoint between gloves and mittens. In the three-finger mitts, the fingers are arranged with the index finger in a separate pocket to the other three fingers. This provides slightly better hand-grasping dexterity while still permitting heavy insulation around the hands.
The dry suit may also have an integrated hood, which seals water out around the wearer's face, and helps keep the wearer's head warm. The integrated hood is often latex rubber that fits tightly around the head, but can also be made from neoprene or membrane to allow an insulating cap to be worn under the hood. Care must be taken to avoid the hood making a waterproof seal around either of the ears, as this would risk an eardrum bursting outwards at depth.
Separate (non integral) hoods are of two types: one which extends only to the base of the neck, and the other a standard wetsuit hood with a large flange. Hoods are never tucked into the neck seal as they would be tucked into a wetsuit, as this would compromise the watertight integrity of the seal. Some suits are designed with a second (non-watertight) "warm neck collar" around the neck seal, which allows the flange of a standard wetsuit hood to tuck in around the outside of the seal. This can keep the neck significantly warmer, since the seal itself provides little insulation.
When a diver needs to be underwater for long periods day after day, a snug-fitting elastic hood can cause uncomfortable pressure sores on the ears, face, and jaw. To alleviate this and to permit easy communication with the surface and between divers, a rigid metal or fibre-reinforced plastic diving helmet may be worn with the dry suit. This can be separate from the dry suit with its own watertight neck seal, or it can be clamped onto a neck ring attached to the suit, so that air can flow between the helmet and the suit.
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Most commercial diving dry suits have heavy duty integral boots. Sport diving suits may have lightweight integral boots or soft neoprene booties. Rock boots or heavy working boots may also be worn over integral neoprene socks. Boots which are stiff at the ankle make finning inefficient and are unsuitable for many diving applications where mobility is important. If the suit will be used by a diver who needs to fin efficiently on some dives and to walk on sharp surfaces on other dives, it is more effective to wear boots suited to the dive over a dry suit with integral socks.
Surface dry suits may have socks or ankle seals fitted. Socks are normally made from latex rubber or from a breathable material similar to the rest of the suit. An outer boot or shoe would normally be worn over these socks to protect them from wear and the risk of puncture. The outer boot also provides more warmth than the thin layer of latex. A regular sock (e.g. a woollen sock) would normally be worn inside the drysuit sock for comfort. Latex rubber ankle seals are sometimes fitted in place of socks and can allow better foot control of water skis and surfboards. Survival suits may have neoprene socks of the same material as the suit, with tougher soles and ankle ties to keep them on the feet, as the "one-size fits all" socks must be too big for most users.
For a commercial environment where the option of interchangeable boots for different sizes of feet is desired, the legs of the dry suit can also be fitted with attachment rings. Some commercial divers order their suits without boots and install rubber work boots such as those used by miners or firefighters.[clarification needed]
Attachment rings allow separate neck seals, gloves, and (less commonly) boots to be joined to the suit with a watertight seal. The older style attachment ring system uses a support ring inside the suit and a clamping band outside the suit to tightly hold the suit and the separate hood/boot/glove together. They were also used with the neck seals of some old British frogman-type dry suits.
The support ring can optionally be slipped into the sleeve of a regular dry suit that has wrist seals, to temporarily put watertight rubber gloves on the suit, or the wrist seals can be removed and the inner support ring is permanently attached inside the sleeve. The support ring may be a large one-piece unit that can be slipped over the head/hands/feet, or it may be split into halves that can be directly installed up close around the neck/wrists/ankles.[clarification needed]
More recently, on both commercial and recreational suits, "quick-change" rings have become increasingly common. These are permanently glued to the suit and accessories, either during manufacture or as a retrofit. These systems form a watertight seal between the suit and components using soft rings on both pieces that comprise a series of interlocking channels, similar in principle to a common food storage bag. Quick-change rings allow a diver to easily replace a damaged seal on the surface with no tools or adhesives, or to change attachments depending on conditions–for example, choosing between dry gloves and standard wrist seals. Different manufacturers' ring systems are generally incompatible, so the diver must choose accessories that are designed for the ring system on his or her suit.
A typical diving dry suit has an air exhaust valve, which lets the diver vent gas from the suit during the ascent. This is necessary because when the diver ascends, the air in the suit expands and inflates the suit, and hinders movement. The air in an over-inflated suit will make the diver excessively buoyant, and can cause an uncontrolled ascent to the surface or any solid obstruction above the diver, which may result in decompression sickness from missed decompression stops, arterial gas embolism, or other barotrauma of ascent from over-expansion of the lungs.
Exhaust valves can be automatic, operating as pressure relief valves, or manual, where the diver must actuate the valve to vent. Most dry suits have an adjustable exhaust on the shoulder which can be set to release at varying pressures or operated manually at any setting. In most situations, the diver can leave the valve at a constant setting throughout the dive so that it releases with a small amount of over-pressure, and needs only to raise the arm while in a near-vertical position in order to vent the suit. With this technique, the suit will vent as needed automatically as the diver ascends. Automatic vents are generally at the left shoulder, and manual vents are at the wrist. Some older dry suits may have no vents, and the diver must lift one of the wrist seals or the neck seal open to vent the dry suit. Environmentally sealed suits used for diving in contaminated water have no dump valve, but are clamped to the helmet with a watertight seal, so the exhaust valve of the helmet functions as a dump valve. Surface dry suits do not normally have exhaust valves, but the wearer may vent excess air by crouching down, "hugging" his legs, and slipping a finger under the neck seal.
The air inside the suit is compressed as the diver descends, so a diving dry suit also has an inflation valve, which lets the diver control the buoyancy of the suit by injecting gas from a diving cylinder or the umbilical to prevent the suit from being squeezed tightly and painfully onto the diver's body during descent. The sensation is similar to being pinched wherever the suit forms a fold. Suit squeeze also compresses insulating garments and thus reduces thermal protection, and can hinder the diver's freedom of movement and make swimming more difficult. Environmentally sealed suits which are sealed to the helmet automatically equalize from the breathing gas. 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 (9.1 m) depth), had to put up with the suit squeeze.
Suit inflation gas supply
Normally, the gas used for dry suit inflation for scuba diving is air from the primary breathing cylinder, but when divers breathe helium-based gas mixes such as trimix or heliox, they usually 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. Using argon increases the insulation value of a given suit by approximately 20%, without adding any additional bulk or weight. To gain the full benefit, the user must flush the suit with argon before the dive. Argon cylinders should always be clearly marked so that a diver does not accidentally attach a breathing regulator; this is a potential hazard especially for technical divers, who often carry several independent cylinders and regulators. Breathing pure argon will result in rapid unconsciousness. Alternatively, some trimix divers inflate their suits from a decompression cylinder containing a nitrox blend, as all nitrox blends have essentially the same thermal conductivity as air). The use of high oxygen fraction mixtures for suit inflation constitutes a severe fire hazard when out of the water after a dive.
In surface dry suits, the wearer normally never dives deeply underwater, and is not concerned about suit squeeze or neutral buoyancy, so there are no air valves on a surface dry suit.
There are two types of low-pressure hose commonly used for suit inflation: The standard Seatec style quick release couple, fitted with an internal Schrader valve, as also used on most buoyancy compensators, and the CEJN connector which allows a higher flow rate due to a larger bore through the connector. This valve can allow a dangerously fast inflation rate if it jams open, and is also more likely to free-flow when disconnected. These hoses use incompatible valve nipples, but it is usually possible to swap the fitting on the inflator valve to accept the alternative hose. Both types of BCD and dry suit inflator hoses are supplied with an O-ring sealed 3/8” male UNF thread for connection to a low-pressure first stage port.
Zipper protection flaps
Some suits are provided with a flap which can be closed over the outside of the zipper to protect it from being damaged by contact with the diver's equipment or the environment. these flaps may be held in place by velcro or a non-watertight outer zipper.
For commercial divers or technical divers who may spend many hours in a dry suit underwater, it is not practical to have to climb back on board the ship in order to open a waterproof relief zipper and urinate. The P-valve is a urinal built into the suit, which enables a diver to urinate at any time without having to get out of the water, while keeping him or her dry and clean inside the suit.
Before putting on the dry suit, the male diver puts on a condom catheter, which is similar to a condom except that it is made of thicker material with a cuff or adhesive ring to prevent it from slipping off, and its end connects to a built-on drain tube. After putting it on, he attaches the end of the tube to a drain hose in the crotch of the suit. This drain hose leads to a vent opening just above a knee, and may also have a one-way valve (P-valve) to prevent ocean water from flowing back in if the hose gets disconnected. The female diver puts on an external catching device in the form of a wide-rimmed, low-profile, elongated cup. The rim is affixed onto the skin surrounding the labia with medical grade glue. The cup's drain hose connects to the drain hose.
For applications where passive heating is insufficient, active heating can be used. One of the earliest systems was the tube suit, a set of underwear with a complicated labyrinth of tubes which carried heated water supplied from the surface or the lockout submersible through an additional hose in the diver's umbilical. Other active heating systems use electrical heating elements in an undersuit layer, or internal pockets containing hot-packs, sealed plastic bags containing materials which emit latent heat during a phase change.
Use of dry suits can conveniently be divided into surface and underwater applications, as the construction of the suit may be optimized for either.
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Dry suits are often worn for boating, especially sailing, and on personal water craft in the winter months. The primary uses are for protection from spray, and in case of accidental short-term immersion in cold water if the user falls overboard. These dry suits, which are only intended for temporary immersion, are less rugged than diving dry suits. They are usually made of a breathable membrane material to let sweat permeate, keeping the wearer dry and comfortable all day. Membrane type surface dry suits only keep the user dry, and have little thermal insulating properties. Most users will wear a thin thermal undersuit, or street clothes, for warmth; but wearing ordinary fabrics can be dangerous if the suit leaks in cold water because they will lose all insulating properties.
Dry suits are used for windsurfing, kitesurfing, kayaking, water skiing and other surface water sports where the user is frequently immersed in cold water. These suits are often made from very lightweight material for high flexibility. Membrane type suits are commonly used in the spring and autumn with moderate water temperatures, but Neoprene and hybrid dry suits for surface sports are preferred in cold water. These provide greater thermal protection in the event of a leak. The ability to swim for self-rescue in these types of suits is important to water sports users that do not use a boat. A neoprene bottom also is less likely to allow trapped air to collect in the legs, causing the wearer to tend to float head down in the water.
Crew members who must work on the decks of commercial ships wear a type of dry suit also known as an immersion survival work suit. Single engine aircraft ferry pilots flying between North America and Europe, and helicopter pilots that must fly over the open ocean, must wear a survival suit in the cockpit, so they can continue to fly the aircraft, then exit immediately if the aircraft is ditched in cold water after an engine failure. These suits are also used on shore when working on docks, bridges, or other areas where cold water immersion is a safety risk. They are usually a three-part system consisting of:
- A warm undersuit made of synthetic fabric designed to wick moisture from sweat generated by physical exertion away from the user’s skin.
- A dry suit made with a waterproof breathable membrane to let moisture permeate out of the suit.
- A durable outer shell, designed to protect the dry suit, and to carry tools and survival gear. The outer shell may also be equipped with an inflatable bladder to give the wearer additional flotation and freeboard when immersed.
Immersion survival suits are dry suits carried for use by ship and aircraft crew who will be immersed in cold water if the craft must be abandoned. Unlike immersion survival work suits, these are not intended to be worn all the time, and are only to be used in an emergency. Survival suits will typically be a one-piece design made of fire-retardant neoprene, optimized with quick donning features, and produced in high visibility colours with reflective tape patches.
Dry suits are also worn by rescue personnel who must enter, or may accidentally enter, cold water. Features of dry suits designed for rescue may be a hybrid of the immersion survival and work suits, since the wearer is not expected to be working in the suit for an extended time. They may also be optimized for a specific task such as ice rescue, or helicopter rescue swimmer.
Dry suits are typically used where the water temperature is below 15 °C (60 °F), and for extended immersion in water above 15 °C (60 °F), where discomfort would be experienced by a wet suit user. They are also used with an integral helmet, boots, and gloves for personal protection when working in and around hazardous liquids.
Dry suits for recreational diving are made in both membrane and neoprene, and primarily differ from surface dry suits in that they have inflation and deflation air valves to maintain neutral buoyancy, and may be slightly more durable.
Dry suits for commercial and military diving tend to be heavier and more durable than recreational diving dry suits because they will endure a harsh and abrasive environment, especially if being used for heavy labor such as underwater welding. Some commercial dry suits are rated for contaminated environment diving, and when combined with a suitably rated diving helmet can completely isolate and protect the diver from hazardous environments such as sewage pits and chemical storage tanks. These "hazmat suits" are most often made of vulcanized rubber laminated to a cloth liner, which is easier to decontaminate because of its slick surface, than other, dry suit materials.
Manufacturing processes mainly depend on the material of the shell. Most suit shells are currently assembled by stitching the seams, which in the case of neoprene suits are first butt-glued, and are then waterproofed by glued seam tape. DUI use a liquid polyurethane sealing compound over the seams on the inside of the suit instead of tape, and the rubber-coated Viking suits are dipped and heat cured for a seamless waterproof layer. DUI crushed neoprene suit shells are assembled before crushing the bubbles by hydrostatic pressure, then adding seals, zippers and accessories.
Care of suit
Some components are inherently susceptible to damage if not treated with due care.
Latex and silicone seals are easily pierced by sharp objects. Gripping the seal with long fingernails to pull it on or off can cut through the material, while long toenails can damage thin rubber booties when the foot is pushed inside tight-fitting fins.
Latex is subject to rubber perishing, or "dry rot," where ozone normally present in the air deteriorates the material over time, regardless of use. A latex seal is generally expected to last 1–2 years. The useful life can be extended by coating the seals with a special protective compound,[clarification needed] and (in suits with removable seals) detaching the seals when not in use and keeping them in airtight containers. They should also be kept in a cool, dark environment.
Silicone seals are similar in strength and elasticity to latex, but do not perish in the same way.
Neoprene seals are a tougher and more tear resistant alternative, though they must be correctly sized for the user, as they cannot be adjusted much. These are much more resistant to perishing than latex. Use of a lubricating liquid is suggested for donning neoprene wrist seals.[clarification needed]
Metal toothed watertight zippers rely on pressure between the two rubberized contact surfaces of the zipper tapes alongside the teeth for sealing. To get this pressure, the slider needs to press the two faces together while closing, and this increases friction between the slider and the teeth, so the zipper requires more force to close than regular zippers. If the two rows of open teeth are lined up and close together in front of the pull it will prevent misalignment which can permanently damage the sealing edge, and allow the zipper to be closed with less effort. Friction can be reduced by suitable lubrication which is usually done with a waterproof wax or grease which remains on the zipper when wet. There should not be an excessive buildup of lubricant which would stick to particles of grit and cause wear and additional friction. The plastic tooth zippers have less friction than the metal teeth and need less force to close.
On metal toothed zippers, the cut edges of the rubberized fabric of the zipper tapes are susceptible to fraying along the exposed weave. if not trimmed, the frayed edges can accelerate damage to the weave and eventually delaminate the edge. The moulded plastic zippers do not have an exposed cut edge, so do not have this weakness.
Hazards of use
Hyperthermia on deck before a dive
Dressing into a dry suit is usually more time-consuming than a wet suit, and may require the assistance of another person to check the neck seal and close the zipper. In situations where the air is warm but the water cold, a prolonged time on the deck of a boat donning a dry suit and other gear can present a risk of overheating to the diver. This is a particular problem to relatively inexperienced divers, who may require more time to dress in. This problem can be mitigated by preparing all other equipment as far as possible before fully donning the suit and to wet the outside of the suit, and the hair and face after closing the zipper, to provide some evaporative cooling while on deck. Professional stand-by divers may have a similar problem, as they are required to be ready for deployment at all times while the working diver is in the water, which may involve waiting on deck for several hours. Wetting the outside of the suit, and seating the diver in shade and a breeze are the usual solution to this problem.
During descent the air in the suit is compressed and unless more is added, the folds may be pressed together so tightly by water pressure that they pinch the skin, which is painful and may cause local bruising. The suit may also become so tight that movement is restricted, particularly in a membrane suit. This problem is managed by suit inflation from a low pressure gas supply.
Dry suits pose their own unique problems compared to wet suit diving, due to the complex construction and since a diver needs to constantly manage and adjust the air volume inside the suit. During descent, air must be added to maintain constant volume. This prevents suit squeeze, loss of neutral buoyancy, and potential uncontrolled descent. During ascent, the air added at depth must be removed again, in order to prevent over-inflation, excessive buoyancy, and potential uncontrolled ascent. Most modern dry suits are equipped with adjustable spring-loaded automatic exhaust valves, which can assist with this problem when properly set.
Damage to the lower part of the suit can cause a sudden inrush of very cold water for winter users, or an inrush of contaminated water or chemicals for hazmat divers.
Damage to the upper part of the suit can cause a sudden venting of the air, resulting in a loss of buoyancy and possible uncontrolled descent, followed by flooding with water and loss of thermal insulation, and possible exposure to hazardous materials if the water is contaminated.
A flooded suit may contain so much water that the diver cannot climb out of the water because of the weight and inertia. In this case it may be necessary to cut a small slit in the lower part of the leg to let water drain out as the diver rises out of the water. This will take some time, and agility will be seriously compromised. The damage should not be difficult to repair if the slit is cut with reasonable care.
Diving without a BCD
Since the dry suit contains a variable volume of air, some divers control their buoyancy with the dry suit and dive without the buoyancy control device that is generally worn by scuba divers wearing wet suits. Although it is possible to dive like this, the risks are higher than when using a buoyancy compensator. A diver should be able to survive failure of any single piece of equipment, so there must be a backup system available in case of loss of dry suit buoyancy. Release of the diving weights may not be sufficient to compensate for a flooded dry suit if the scuba cylinders are very negatively buoyant.
Although quite tough and reliable, dry suits are more prone to catastrophic failure than wet-suits as they can completely flood when a seal tears or a zip breaks, so the buoyancy provided is less reliable than buoyancy compensators. Wrist and neck seals can vent accidentally; a trivial problem during normal diving but more serious in an emergency or with an incapacitated diver.
If the diver is over-weighted, the suit may contain additional air to offset the extra weight, and migration of this air to the legs when the diver is trimmed level can cause the diver to "invert" to a legs-up position that makes venting the dry suit difficult. If this position causes the diver's feet to pull out of the boots, the fins will be compromised and it may not be possible to fin back into a position where the excess air can be vented.
Maintaining horizontal trim in an over-inflated dry suit can be difficult as the excess air tends to gather at a local high point in the suit, which will usually not be suitably aligned with the centre of gravity. Rotation of the diver due to the moment exerted by this offset will generally tend to move the air pocket further from the centre of gravity, making the air move further towards the extremities, so that stability is reached with the diver upright or inverted, neither of which is desirable for efficient swimming.
The air bladders of buoyancy compensators are generally more robust and reliable than dry suits.[clarification needed] They are designed for providing buoyancy both at the surface and underwater. They provide buoyancy only at the torso, near the centre of gravity, where it can help the diver trim correctly. Also, the vent valves of a BCD are more secure, requiring the diver to press a button or pull a cord to release buoyancy gas.
An over-tight neck seal can put pressure on the carotid artery, causing a reflex which slows the heart, resulting in poor oxygen delivery to the brain, light-headedness and eventual unconsciousness. For this reason, neck seals should be stretched or trimmed to the correct size.
Accidental body-inversion hazards
If there is more air in the dry suit than is needed to counteract "squeeze" on the undersuit, that excess air creates a "bubble" which moves to the highest point of the suit; in an upright diver this is the shoulders. In such cases, divers wearing loose baggy suits need to keep their legs at level or below their waist. Otherwise the bubble quickly moves to the highest point, and if the legs are above the waist, the bubble moves into the legs and feet, causing the legs to rise, and "inverting" the diver's body into a head-down position.
The movement of such a large bubble to the legs can be a problem for a number of reasons: It balloons the legs, and it may inflate thin rubber booties enough to cause fins to pop off; a diver without fins has more restricted ability to move and become upright, and also loses the ability to kick downward to maintain depth, so that the bubble expansion problem does not grow worse. Movement of gas into the legs and feet may also cause special difficulties in drysuits that have air exhaust values only at the shoulders or wrists, because the air in the legs and booties cannot be evacuated while the diver is inverted, and such a diver may be moving toward the surface, causing the problem of expanding air in the suit to grow worse with each meter of lost depth. (Some low-quality buoyancy control devices also cannot vent air, when inverted). If the diver is positively buoyant and rising, the buoyancy of the dry suit becomes uncontrollable after rising though a certain fraction of depth, and there is then an increased risk of a rapid ascent which grows more rapid, as the distance to the surface decrease. The final result of such a run-away inversion is a diver rising all the way to the surface, feet first, in an uncontrolled ascent that is too rapid for decompression safety.
When the suit is being used correctly, the bubble inside it is relatively small, and its movement is not important. The bubble may be large for a variety of reasons: if a diver has ascended without venting the suit; if the valve supplying gas to dry suit fails in the open position; or if the diver is over-weighted, and extra air has been added to the suit at some point to make the diver neutrally buoyant. The size of the bubble can be minimised by being correctly weighted and venting excess gas from the suit on ascent. Some divers ensure that the bubble remains at the top of their body by using the buoyancy compensator to counteract any excess weighting, keeping only the minimum gas necessary to avoid squeeze inside the drysuit.
The recommended solution in all such "inversion accidents," is for the wearer to bend at the knees and powerfully flap the arms to do a backward or forward roll to the upright position and then vent the suit, if needed, by manually opening the neck seal (sometimes called "burping the suit") by breaking the seal-neck contact with a finger.
Surface dry suit users can face a similar inversion problem. The problem is more acute when not wearing a personal flotation device (life vest) over the dry suit. For surface dry suit users, the inversion can be much more critical if no one is nearby to assist, since the wearer may be held upside down and unable to breathe, and may also have water run down into their nose while inverted.
It is not a problem for close-fitting neoprene suits, or hybrid suits with neoprene bottoms, which prevent air from easily moving into the legs of the suit. Wearers of baggy surface dry suits can mitigate the problem by venting out as much excess air as possible before entering the water. This is typically done by crouching down and leaning forward, wrapping the arms around the knees, and then having an assistant zip the suit shut while it is stretched out tightly. Excess air can also be "burped" out of the neck seal.
Gaiters and ankle weights
Most suits have relatively baggy trouser legs to allow passage of the feet to the boots. This can hold a large volume of air when inverted, which may pull the boots off the feet. Elastic or tailored "gaiters" can be pulled snug around the lower legs to reduce the potential airspace to help prevent an inversion event and help maintain horizontal trim. Gaiters may also reduce hydrodynamic drag when finning, reduce the risk of the feet pulling out of the boots when inverted, and can be used effectively on membrane and neoprene suits. Small ankle-weights (typically one or two pounds) can also be used with any dry suit, both to provide trim weight at the bottom of the suit, and function as short gaiters to constrict the ankle region of suit once the foot is in the boot. Ankle-weights have to be accelerated and decelerated along with the fins during every kick, which requires more energy from the diver. Gaiters do not have this drawback as they are typically very light and approximately neutral buoyancy.
The Pirelli dry suit was designed in the 1930s and used by Italian frogmen during World War II. It became available for recreational divers after war the and was patented (US Pat. No. 2,570,019) in 1951 for Pirelli by Eugenio Wolk, listed as the inventor. This two piece suit was made from thin and elastic rubber, optionally bonded to a knit fabric reinforcement liner except at the sealing areas at the neck, wrists and waist. The waist seal was achieved by overlapping the jacket and trousers and folding the overlap down more than once before securing it in place over a profiled heavy rubber waistband using an elastic belt which pulls the rolled part into a groove in the waistband. Neck and cuff seals were the forerunners of the latex seals still used for this application. The patent claims this to be the first application of thin and flexible form-fitting rubber for the manufacture of dry suits, and also patents the waist seal system. The suits were intended to be worn over woolen underwear for thermal protection. There was no facility to inject air during a dive. These suits were available in four sizes and five styles, three of which were full length two-piece suits with integral boots, one of which was lined with cloth, and two of which had an optional integral hood on the jacket. The other two models were a two-piece with short sleeves and legs, and a one piece short trouser unit with suspenders which sealed on the chest and thighs.
British frogmen of World War II and for some time afterwards used a similar one or two piece rubberized knit fabric suit by Siebe Gorman. They produced the one-piece front-entry Sladen suit with integral rubber helmet, developed by the British Admiralty for use with manned torpedoes, and in the late 1950s also the Essjee two-piece swim suit, based on the Sladen suit. The Essjee suit consisted of a jacket with rubber hood and lightweight wrist cuffs, and trousers shod with moulded rubber soles. The two parts were sealed by rolling the overlapped rubber skirts of the jacket and trousers together and these were held in place by a separate rubber cummerbund. Soft sponge-rubber pads inside the hood covered the ears and allowed them to be equalised. There was space under the suit for plenty of woollen underclothes. The suit was available in proofed gabardine or rubberised stockinette, with the cloth on the outside and the rubber inside, to protect the rubber from sunlight while in use.
In 1945 the Spearfisherman Company, owned by Arthur Brown, of Huntington Beach, California was approached by the US Navy to produce a rubber suit. These were advertised in the first issue of the Skin Diver magazine in December 1951, as “seamless, one-piece, pure gum rubber, nude freedom frogman suits”. These were entered by a chute which was folded and clamped to seal, and were available as full length or shortie suits with integral hood. Later versions had a neck level entry chute and a nape valve to purge trapped air. The shortie version was also rebranded as Kellys 7-seas suit.
A seamless dipped latex two-piece suit by an unidentified manufacturer, apparently marketed exclusively for women. was catalogued by Palley's of California in the early 1950s. The suit was made in two sections, connected by a rolled overlap similar to the Pirelli suits, and were available in long or short leg versions and long or short sleeved versions, all with integral neck, and cuff or arm and thigh seals. A separate hood was also available, and optional boots for the long leg version.
Waterwear of Newport Beach, California, produced the natural gum-rubber Seal suit for US Divers from 1953 or earlier. Several versions were available, including one piece and two piece suits. The one piece suits were available with long or short legs and sleeves, and with front, neck or back entry. Neck entry suits were sealed by overlapping the neck opening and the hood over a grooved neck ring, and clamping with a large elastic O-ring. The two piece suit shirt and pants were also available separately and could be sealed together at the waist by a system similar to the neck entry suit.
By the mid-1950s, C.E. Heinke & Co. Ltd., an established manufacturer of Standard diving equipment, had diversified into recreational underwater swimming equipment, including the Delta dry suit, made from natural rubber on a stockinette base. The basic Delta was a two piece suit made up of a jacket with neck seal and trousers with ankle seals which could be worn over woolen undergarments. The full suit included integral hood and feet. The overlapped and rolled waist seal was held in place by a cummerbund.
For a few years after C.E. Heinke & Co. Ltd. was taken over by Siebe-Gorman and Company in 1961, dry suits were marketed under the Siebe-Heinke label. The Siebe-Heinke Dip Suit for recreational diving, swimming, yachting and fishing, was advertised in Lillywhites’ 1964 underwater catalogue. The standard Dip Suit was a set of seamless black dipped-latex jacket with neck and cuff seals, and trousers with separate yellow latex waist-seal cummerbund. A yellow hood and black protective over-bootees were optional extras. Small, medium and large sizes were available. The Siebe-Heinke Frogman dry suit for professional and recreational use was introduced in 1963. It was available in stockinette proofed with black rubber, or proofed fawn twill. The suit consisted of a set of booted trousers with reinforced soles or optional ankle seals, and a jacket with cuff seals and an option between a neck seal or integral hood. The two parts were connected by a rolled waist seal held in place by a rubber cummerbund. Sizes available were small, medium, large short and large.
In 1955, Healthways retailed Carib drysuits, made of 3-ply translucent gum rubber, and available in long and short versions. Entry was by a front chute with rubber band closure. The full version included an integral hood and covered the feet. In 1957, they added the Aqua King and Aqua Flite dry suits to their product range. The Aqua King suit was a full-length waist entry suit, comprising hood, long sleeved shirt, booted pants and waistline sealing ring, and was made of seamless latex rubber. All these suits were available in small medium and large sizes.
W.J. Voit Rubber Corporation of New York, Danville and Los Angeles mamufactured the one-piece front-entry VDS10 and two-piece waist-entry VDS11 full dry suits in two ply lightweight gum rubber with integral boots and hood. These were available completed or as kits for home assembly.
Bel-Aqua Water Sports Company of Los Angeles (later Aquala Sports Manufacturing Company) marketed dry suits designed and manufactured by Bill Barada from 1954 or earlier. These were front entry one-piece or waist entry two piece suits with optional hood in 3-ply rubber, with optional integral hood, intended to be worn over insulating underwear suited to the water temperature. The front entry was sealed by binding the entry chute with a length of surgical rubber, and waist entry was sealed by rolling the overlap over a rubber ring. Boots, cuff and collar were moulded rubber. These were available in small, mediun or large and were also available in kit form.
So-Lo Marx Rubber Company produced Skooba-"totes" dry suits from the late 1950s. These two piece seamless rubber suits with "ring and rail" waist seal, reinforced feet and optional hood were available in several colours over the years including green, brown, yellow and red. Sizes ranged from extra small to extra large.
The Dolphin Manufacturing Company of California designed and manufactured rubber spearfishing suits in the 1950s. Trading as Dolphin Enterprises, it sold the original front-entry Dolphin suits in ready-made and kit forms, before launching a new design 2-ply pocket entry suit. The Dolphin suit was available in four sizes and at least three colours (green, kelp and sand) with a tie-off sealed front-entry chute, hood and moulded boots. The company appears to have changed its name again to “Penguin Suits” after moving to Long Beach, California with the pocket entry suit as its leading product. Penguin suits marketed the one piece P1 suit with pocket entry, and the two-piece P2 suit with waist entry and roll seal, in red, blue or black including seamless moulded boots with scuff soles and an optional hood.
Introduction of the watertight zipper
Variable volume dry suits
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