Personal flotation device

A man wearing a life vest, with another life vest hanging at the lower left.

A personal flotation device (abbreviated as PFD; also referred to as, lifejacket, life preserver, Mae West, life vest, life saver, cork jacket, buoyancy aid, flotation suit, etc.) is a device designed to assist a wearer, either conscious or unconscious, to keep afloat.

Devices designed and approved by authorities for use by civilians (recreational boaters, sailors, canoeists, kayakers, etc.) differ from those designed for use by passengers and crew of aircraft (helicopters, airplanes) and of commercial vessels (tugs, passenger ferries, cargo ships). Devices used by military (army, air force, special forces, marines, navy, coast guard) and police and enforcement agencies generally have features not found on civilian or commercial models, for example compatibility with other worn kit (e.g. survival vest, bulletproof vest/body armor, equipment harness, rappelling harness, parachute) and use of ballistic nylon cloth to protect pressurized carbon dioxide (CO2) canisters used for inflating the vest from injuring the wearer if struck by a round from a firearm. The ballistic cloth keeps the fragments from the canister from becoming shrapnel injurious to the user.

PFDs are available in different sizes and different designs purposed for various levels of protection.

Contents

Design(s)

Lifejackets or life vests are mandatory on airplanes travelling over water (in which case they consist of a pair of air cells (bladders) that can be inflated by triggering the release of carbon dioxide gas from a canister—one canister for each separate cell. Or the cells can be inflated "orally" that is by blowing into a flexible tube with a one-way valve to seal the air in the cell). Lifejackets must also be supplied on commercial seafaring vessels, accessible to all crew and passengers and to be donned in an emergency. Not only people wear any type of personal flotation devices, but some are available for dogs to wear.

Flotation devices are also found in near water-edges and at swimming pools. They may take the form of a simple vest, a jacket, a full-body suit (one piece coverall), or their variations suited for particular purposes. They are most commonly made of a tough synthetic fiber material encapsulating a source of buoyancy, such as foam or a chamber of air, and are often brightly colored as yellow or orange to maximize visibility for rescues. Some devices consist of a combination of both buoyancy foam and an air chamber. Retroreflective "SOLAS" tape is often sewn to the fabric used to construct lifejackets and PFDs to facilitate a person being spotted in darkness when a search light is shone towards the wearer. Per federal regulations all persons under the age of 13 are required to a life jacket (PFD) when in a watercraft under 12 meters.State regulations may raise or lower this number and must be followed when in that states jurisdiction.

Types

Buoyancy aid (Foam Core)

A buoyancy aid (with a foam core)

The simplest and least buoyant type of PFD comes in the form of nylon-lined foam vests, used predominantly in watersports such as kayaking, canoeing and dinghy sailing.

Buoyancy aids are designed to allow freedom of movement while providing necessary buoyancy to a user. They are also designed for minimal maintenance and as they are only constructed from foam, can be mass-produced inexpensively making them one of the most commonly seen form of PFDs.

Buoyancy aids also come designed especially for children. These vests feature crotch straps designed to be worn between the legs of the wearer and also a headrest flap.

The crotch straps are designed to keep the vest from riding up when worn in the water, and possibly the wearer from completely slipping out of the life vest. The strap is adjustable and should be sized to fit snugly between the wearer's legs, tight enough to hold the vest low on the wearer so they are not choked by the vest rising up because of its buoyancy, but loose enough so the wearer may swim comfortably, not feeling constrained by the vest. This strap is included life vests designed to be worn by 30–60-pound (14–27 kg) children and on some vests designed to be worn by people 60–90 pounds (27–41 kg) as well. This strap should be worn at all times to eliminate the chance of the wearer slipping out of the vest.

The headrest flap is designed to help support the head and keep it out of the water. A grab handle is attached to the headrest to, if needed, rescue or lift the wearer up, or simply to carry the vest itself.

Lifejacket

The person on the right wearing an example of an air chamber lifejacket.

Lifejackets for outfitting large commercial transport in potentially dangerous waters, such as coastal cruises and offshore passages, and overwater air flights, are either a single air chamber or a pair of (twin or double) sealed air chambers constructed of coated nylon (sometimes with a protective outer encasing of heavier, tougher material such as vinyl), joined together (but can also be constructed of foam aboard ships). Twin air chambers provide for redundancy in the event of one of the air chambers leaking or failing to "fire", for example if the thin air cell fabric is sliced open by sharp metal fragments during emergency evacuation and egress. The majority of lifejackets found in leisure use will be single air chamber type.

Aircraft devices for crew and passengers are always inflatable since it may be necessary to swim down and away from a ditched or submerged aircraft: inflated or foam filled devices would significantly impede a person from swimming downward in order to escape a vehicle cabin. Upon surfacing, the person would then inflate the device, orally or by triggering the gas canister release mechanism.

"True" lifejackets always provide more buoyancy than buoyancy aids[1] and the positioning of the buoyancy on the wearer's torso is such that a righting moment (rotational force) is developed that will eventually float most persons (for example unconscious) who are face down into a FACE UP attitude with their bodies inclined backward, unlike common foam buoyancy vests (which are simply swimmers' aids, really since they don't generate re-righting moment forces.) Self righting devices are best for non-swimmers, who may not be able to orient themselves face up in the water, for example due to panic arising from finding themselves in deep, open water.

Today these air chamber vests are commonly referred to as "inflatable lifejackets or vests" and are available not only for commercial applications but also for recreational boating, fishing, sailing, as well as kayaking and canoeing. They are available in a variety of styles and are generally more comfortable and less bulky than traditional foam vests.

The air chambers are always located over the breast, across the shoulders and encircling the back of the head. They may be inflated by either self-contained carbon dioxide cartridges activated by the pulling of a cord, or blow tubes with a one-way valve for inflation by exhalation. Some of the inflatable lifejackets also react with the salt/fresh water, inflating them. The latest generation of self triggering inflation devices, however, respond to water pressure when submerged and incorporate an actuator known as a "hydrostatic release". Regardless of whether manually (pull cord) or automatically triggered, a pin punctures the cartridge/canister and the CO2 gas escapes into the sealed air chamber. However, there is a chance that these water pressure activated inflation devices do not inflate the lifejacket if a person is wearing waterproof clothing and falls into the water face-down. In these cases the buoyancy of the clothing can hold a person on the water surface and avoids the hydrostatic release. As a result a person can drown although the lifejacket is fully functional. To be on the safe side, a pill activated inflation device should be preferred. A little pill that dissolves with water contact is in fact the safest option as it also works in shallow waters where the hydrostatic activator fails. This type of jacket is called an automatic. As it is more sensitive it used to be the case that this style of automatic system was more likely to activate during very heavy rain or spray. However, with modern cup/bobbin mechanisms this is now a rarity and some mechanisms such as the Halkey Roberts Pro firing system have all but eliminated this accidental firing.. Spare re-arming kits should always be carried for any lifejacket you have onboard.

Drifting in open seas and international waters, as encountered by long sea voyages and military forces, require prolonged survival in water. The lifejackets suited for this purpose are often attached to a vest with pockets and attachment points for distress signaling and survival aids, for example: a handheld two-way radio (walkie-talkie), emergency beacon (406 MHz frequency), signal mirror, sea marker dye, smoke or light signal flares, strobe light, first-aid supplies, concentrated nutritional items, water purification supplies, shark repellent, knife, pistol.

Offshore sailors and others can utilize accessories such as leg straps to keep the inflated chambers in position for floating in a stable attitude and splash or face shields constructed of clear see-through vinyl which covers the head and face to ward off water from waves inundating the face (nasal and mouth entries to the airway).

Survival suit

An example of a Survival suit on a dummy.

Some formats of PFDs are intended for long term immersion in cold water in that they provide insulation as well as buoyancy. While a wetsuit of neoprene rubber and divers' drysuits provide a degree of flotation, they are not formally considered by regulatory agencies as approved lifesaving devices or as PFDs, in most maritime countries.

Note that it is possible for an incapacitated person in the water to float face-down while wearing simply a wet suit or a dry suit since they are not designed to serve as lifesaving devices in the normal use of that term.

The Mark 10 Submarine Escape Immersion Equipment (SEIE) suit is intended to allow submariners to escape from much deeper depths than currently possible with the Steinke hood. Some United States Navy submarines already have the system, with an ambitious installation and training schedule in place for the remainder of the fleet.

Because it is a full-body suit, the Mark 10 provides thermal protection once the wearer reaches the surface, and the Royal Navy has successfully tested it at 180 m (600 foot) depths. (see Submarines in the United States Navy#Pressure and escape training and Steinke hood)

Buoyancy compensator

SCUBA divers commonly wear a "BC" or buoyancy compensator, which involves an inflatable gas chamber. The amount of gas can be increased or decreased to enable the diver to ascend, descend or maintain neutral buoyancy at a given water depth and to provide positive buoyancy in an emergency to bring them to the surface or keep them at the surface.

Specialized

Specialized life jackets can also be seen used in a myriad of environments. Shorter-profile vests are commonly used for kayaking (especially playboating), and high-buoyant types for river outfitters and other whitewater professionals. PFDs which include harnesses for tethered rescue work ('live-bait rescue') and pockets or daisy-chains (a series of loops created by sewing flat nylon webbing at regular intervals) for the attachment of rescue gear are made for swiftwater rescue technicians.

PFD's for pets

Critter's Inflatable life jacket uninflated

While the USCG does not approve personal floatation devices for animals, many manufactures produce lifejackets for dogs and cats. Every year dogs and cat die from downing; either they don’t know how to swim, too dense, tire out from over exposure or old age, or from a medical complication such as a seizure. They also could be knocked into the water and simultaneously knocked unconscious. It is important to protect your pets by providing them the same safety equipment you would give to a child or elderly person.

Most lifejackets on the market are designed around foam that wraps around the body and some also go around the neck. These provide a basic amount of buoyancy for a dog but do not provide a lot of support for the head and are not especially good with very dense dogs like bull dogs.

There is one item on the market that is an automatically inflatable lifejacket for pets made by Critter’s Inflatable, LLC. This device is more expensive than a traditional foam lifejacket, but like the ones designed for people are much less bulky and more comfortable to wear when uninflated and when inflated provide more buoyancy than the foam counter parts. These lifejackets are very popular in the bull dog community and also for water therapy where a lot of support is needed under the head.

History

A "Mae West" life preserver.

The most ancient examples of "primitive life jackets" can be traced back to inflated bladders of animal skins or hollow, sealed gourds, for support when crossing deeper streams and rivers.

Personal flotation devices were not part of the equipment issued to naval sailors up to the early 19th century, for example at the Napoleonic Battle of Trafalgar. Seamen who were press-ganged into naval service might have used such devices to jump ship and swim to freedom. It wasn't until lifesaving services were formed that personal safety of boat crews heading out in pulling boats generally in horrific sea conditions was addressed.

Purpose-designed buoyant safety devices consisting of simple blocks of wood or cork were used by Norwegian seamen. The modern lifejacket is generally credited to one Captain Ward, a Royal National Lifeboat Institution inspector in the United Kingdom, who, in 1854, created a cork vest to be worn by lifeboat crews for both weather protection and buoyancy.

The rigid cork material eventually came to be supplanted by pouches containing watertight cells filled with kapok, a vegetal material. These soft cells were much more flexible and more comfortable to wear compared with devices utilizing hard cork pieces. Kapok buoyancy was used in many navies fighting in the Second World War. Foam eventually supplanted kapok for "inherently buoyant" (vs. inflated and therefore not inherently buoyant) flotation.

Reference: Built for Life: the history of lifejackets; Dr. Christopher Brookes, Defence and Civil Institute for Environmental Medicine (Downsview , Ontario, Canada; Canadian Navy); Survival Systems (Halifax, Nova Scotia, Canada) [apparently the only authoritative text on the subject in the English language with a comprehensive account of lifejackets; the only others are in German] in 1878 they were called life belts.

The University of Victoria in British Columbia pioneered research and development into the "Floater Coat" (patented UVic Thermo Float PFD), which provides superior protection from cold water immersion (immersion hypothermia) through the incorporation of a neoprene rubber "diaper" that seals the user's upper thigh/groin region from otherwise cold, flushing and debilitating water.

Mae West

The Mae West was a common nickname for the first inflatable life preserver, which was invented in 1928 by Peter Markus (1885–1974) (US Patent 1694714) with his subsequent improvements in 1930 and 1931. The nickname was originated because someone wearing the inflated life preserver often appeared to be as physically endowed as the actress Mae West as well as rhyming slang for breast.[2] It was popular during the World War II with U.S. Army Air Forces and Royal Air Force servicemen, who were issued inflatable Mae Wests as part of their flight gear. Air crew members whose lives were saved by use of the Mae West (and other personal flotation devices) were eligible for membership in the Goldfish Club.

During the war, research to improve the design of life jackets was also conducted in the UK by Edgar Pask OBE, the first Professor of Anaesthesia at the Newcastle University. Some of his research involved self-administered anaesthesia as a means of simulating unconsciousness in freezing sea-water. Pask's work earned him the OBE and the description of "The bravest man in the RAF never to have flown an aeroplane".[3]

See also

References

  1. ^ Ten newtons equals 1 kg of flotation
  2. ^ http://en.wikipedia.org/wiki/Mae_West#In_popular_culture
  3. ^ The bravest man in the RAF never to have flown an aeroplane at ncl.ac.uk

External links


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Look at other dictionaries:

  • personal flotation device — noun A life vest or other device or article of clothing designed to be used by one person as an aid to remaining safely afloat in water, especially in a emergency situation. Under the new personal flotation device regulations, boats 16 feet and… …   Wiktionary

  • personal flotation device — a life preserver, life jacket, or other device for keeping a person afloat in the water: esp. in Coast Guard use. Abbr.: PFD [1970 75] * * * personal flotation device, U.S. any device to keep a person afloat in the water; life preserver …   Useful english dictionary

  • personal flotation device — a life preserver, life jacket, or other device for keeping a person afloat in the water: esp. in Coast Guard use. Abbr.: PFD [1970 75] * * * …   Universalium

  • personal flotation device — a life jacket or life vest used to support a person in the water and prevent drowning. Abbreviated as PFD …   Dictionary of ichthyology

  • personal flotation device — noun → life jacket. Abbrev.: PFD …   Australian English dictionary

  • PFD — personal flotation device …   Military dictionary

  • PFD — personal flotation device …   Dictionary of ichthyology

  • PFD — • Personal Flotation Device • Position Fixing Device • process flow diagram …   Maritime acronyms and abbreviations

  • PFD — ˌpē(ˌ)efˈdē abbreviation or noun ( s) : a personal flotation device * * * See personal flotation device. * * * abbrev Personal flotation device * * * pfd., preferred. PFD (no periods), personal flotation device, such as a life jacket. * * * abbr …   Useful english dictionary

  • pfd — abbreviation preferred * * * See personal flotation device. * * * abbrev Personal flotation device * * * pfd., preferred. PFD (no periods), personal flotation device, such as a life jacket. * * * abbr. personal flotation device, a life jacket or… …   Useful english dictionary


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