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A lifeboat or liferaft is a small, rigid or inflatable boat carried for emergency evacuation in the event of a disaster aboard a ship. are required by law on larger commercial ships. Rafts (raft) are also used. In the military, a lifeboat may double as a whaleboat, dinghy, or gig. The ship's tenders of often double as lifeboats. Recreational sailors usually carry inflatable liferafts, though a few prefer small proactive lifeboats that are harder to sink and can be sailed to safety.
Inflatable lifeboats may be equipped with auto-inflation (carbon dioxide or nitrogen) canisters or mechanical pumps. A quick release and pressure release mechanism is fitted on ships so that the canister or pump automatically inflates the lifeboat, and the lifeboat breaks free of the sinking vessel. Commercial aircraft are also required to carry auto-inflating liferafts in case of an emergency water landing; offshore oil platforms also have liferafts.
Ship-launched lifeboats are lowered from on a ship's deck, and are hard to sink in normal circumstances. The cover serves as protection from sun, wind and rain, can be used to collect rainwater, and is normally made of a reflective or fluorescent material that is highly visible. Lifeboats have oars, flares and mirrors for signaling, first aid supplies, and food and water for several days. Some lifeboats are more capably equipped to permit self-rescue, with supplies such as a radio, an engine and sail, heater, navigational equipment, solar water stills, rainwater catchments and fishing equipment.
The International Convention for the Safety of Life at Sea (SOLAS) and the International Life-Saving Appliance Code (LSA) requires certain emergency equipment be carried on each lifeboat and liferaft used on international voyages. Modern lifeboats carry an Emergency Position-Indicating Radio Beacon (EPIRB) and either a radar reflector or Search and Rescue Transponder (SART).
In March 1870, answering a question at the House of Commons of the United Kingdom about the sinking of , George Shaw-Lefevre said that
In the late 1880s, Maria Beasley improved the design of life rafts. She patented a life-saving raft in both the United States and England in 1880.
It was not until after the sinking of on April 15, 1912, that a broader movement began to require a sufficient number of lifeboats on passenger ships for all people on board. Titanic's gross tonnage of 46,000 tonnes was almost five times that which the Board of Trade lifeboat regulations were based on. Even though the 1,178 person capacity of its 20 lifeboats slightly exceeded the required 1,060, it still fell over 2,000 shy of the ship's maximum carrying load of 3,330 people.
The need for so many more lifeboats on the decks of passenger ships after 1912 led to the use of most of the deck space available even on the large ships, creating the problem of restricted passageways. This attempted to be addressed by creating (or adding) separate lifeboat decks, and the wider use of folding boat, a number of which had been carried on Titanic.
In 1943 the US developed a balsa wood liferaft that would not sink, irrespective of the number of holes (from enemy fire) in it. These balsa liferafts were designed to hold five to ten men on a platform suspended on the inside or fifteen to twenty-five hanging lines placed on the outsides. They were inexpensive, and during the war thousands were stored in any space possible on US warships and merchant ships. These liferafts were intended only for use during a short term before lifeboats or another ship in the convoy or group could bring them aboard. When , a cruiser operating alone, was sunk on 30 July 1945, none of its larger lifeboats were launched, and the survivors had to rely on balsa liferafts automatically released as the ship sank; many of the crew perished, but the balsa liferafts saved others; ultimately 316 of 1,196 crew survived.
Merchant Vessels whose keels were laid on or before 1 January 1986 are required to have 200% evacuation capacity with one lifeboat fitted on the port side and one on the starboard side, so that a lifeboat is always available even if the ship is listing to one side. Lifeboat capacity is specified and listed on the ship's "safety equipment certificate". Further details of the boats are found in "Form E" of this certificate.
Ships fitted with "free fall" lifeboats are an exception – they have only one boat, at the stern.
Modern lifeboats have a motor; liferafts usually do not. Large lifeboats use a davit or launching system (there might be multiple lifeboats on one), that requires a human to launch. Lifeboat launching takes longer and has higher risk of failure due to human factors. However lifeboats do not suffer from inflation system failures as inflatable liferafts do.
Since 2006 smaller self-rescue lifeboats have been introduced for use by boats with fewer people aboard: these are rigid dinghies with carbon dioxide-inflated exposure canopies and other safety equipment. Like the lifeboats used before the advent of the petrol engine, these self-rescue dinghies are designed to let the passengers propel themselves to safety by sailing or rowing. In addition to their use as proactive lifeboats, these self-rescue dinghies are also designed to function as unsinkable yacht tenders. An example of a self-rescue dinghy/lifeboat is the Portland Pudgy.
The International Convention for the Safety of Life at Sea (SOLAS) makes it a requirement for merchant ships to have liferafts on each side of the ship, sufficient for all the people on board (the stated capacity of the lifeboat, irrespective of the fact that there may actually be fewer people on board). However, if the lifeboats are "easily transferable" (i.e. have an open deck between port and starboard lifeboat decks), the number of liferafts may be reduced to a total sufficient for the ship's capacity.
The equipment carried in a liferaft is much less than a lifeboat. Unlike lifeboats, liferafts are not self-righting and have no motor.
Tankers are required to carry fireproof lifeboats, tested to survive a flaming oil or petroleum product spill from the tanker. Fire protection of such boats is provided by insulation and a sprinkler system which has a pipe system on top, through which water is pumped and sprayed to cool the surface while the boat is driven clear of the flames. This system, while not failsafe against engine failure, allows fireproof lifeboats to be built of fiberglass.
Vessels that house saturation divers carry hyperbaric lifeboats which incorporate a hyperbaric chamber to allow the divers to escape without undergoing decompression. Self Propelled Hyperbaric Lifeboats, thrustm.com
The United States Navy (USN) uses five types of custom inflatable liferafts as well as a number of commercially available Coast Guard approved liferafts. The 25-person MK-6 and MK-7 are used on surface ships, the 50-person MK-8 on and LRU-13A and LRU-12A on aircraft and respectively. Smaller combatant craft often use 6, 10 or 15-person commercial liferafts. The number of liferafts carried on USN ships is determined based on the maximum number of personnel carried aboard plus 10% as a safety margin. Aircraft carriers carry either 254 MK7 liferafts or 127 MK8 life rafts. While both are similar to heavy-duty commercial liferafts, USN liferafts use breathable air as the inflation gas rather than carbon dioxide to ensure full inflation within 30 seconds in Arctic environments.
Base material used on MK7 life rafts is polyurethane coated fabric which has very high durability. Old MK6 and a few MK8 life rafts are manufactured of neoprene-coated fabric, however, the majority of MK8 liferafts are also manufactured of polyurethane fabric. The lifeboat is compact and made of separate compartments, or "tubes", as a redundancy against puncture. Two Gas cylinder containing dry, breathable compressed air provide initial inflation. Depending on the model liferaft, each cylinder may contain up to 5000 psi of compressed air. Each liferaft is equipped with an external, automatically actuated light beacon and internal lighting. Power is provided by lithium battery.
USN liferafts are stowed in heavy-duty fiberglass canisters and can be launched manually or automatically should the ship begin to sink. Automatic launching and inflation is actuated by a change in pressure sensed by a hydrostatic release device should the ship begin to sink. A hand pump is provided to "top-off" pressure at night when temperatures drop and internal air pressure decreases. Relief valves are installed in each tube to prevent overpressure. Repairs to holes or rips up to six inches in length can be made using special sealing clamps. Occupants in USN liferafts are protected from wind, rain and sun by built-in canopies which automatically inflate. Hatches are sealable to prevent rain and seawater from entering the liferafts. Survival equipment includes: manual reverse osmosis Desalination (MROD), bottles of fresh water, individual food packets, Fishing gear, signaling mirror, rocket and smoke flares, flashlight, spare sea anchor, first aid kit, Oar, spare batteries and bulbs, and aluminized mylar sheets ("") to aid in caring for victims of hypothermia.
USN inflatable liferafts are serviced every five years. Each liferaft is test inflated before repacking. The USN liferafts have a high reliability rate of inflation.
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