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The SEFA is a make of backpack industrial breathing set formerly made by Sabre Safety. It is an oxygen rebreather. "SEFA" is an acronym for "selected elevated flow apparatus".
| | This article needs additional citations for verification .(October 2022) |
The SEFA is a make of backpack industrial breathing set formerly made by Sabre Safety. It is an oxygen rebreather. "SEFA" is an acronym for "selected elevated flow apparatus".
It is in a shiny backpack stainless steel sheet casing with rounded corners and edges, 16 inches wide, 21½ inches high, 6½ inches front to back. It has two wide corrugated breathing tubes leading to a fullface mask which has an inner orinasal mask and a front panel for talking through. Its breathing tubes are 22 inches long, and face forward as they come off the backpack casing. [1] [2]
Its full duration on a filling is 2 hours. It does not have a demand valve or electronic parts, and in theory this would be fewer parts to suffer from failures. It is not designed for scuba diving, but can be used for short shallow submersion such as going through short flooded sections of underground passages. Its casing, to keep grit and stones out of its working, is completely sealed, except for a large vent panel covered with metal mesh, and holes for the oxygen cylinder's on/off valve and the cylinder pressure gauge. Its oxygen flow can be set to 5 or 10 liters/minute. Its intended absorbent is a special make called SefaSorb, which is mostly calcium hydroxide.
As usual, the absorbent makes the breathing gas in circuit hot as it absorbs carbon dioxide. This would be welcome while scuba diving in cold water, but in warm air in a deep mine would be unwelcome. To try to get rid of that heat, the breathing gas is passed through a damp chamber, so the damp will absorb some heat as it evaporates, as in some air conditioning units. It is not very effective, in normal use the breathing air temperature of the SEFA will rapidly exceed 45 °C, and more under heavy work. Being made almost entirely from metal, the SEFA does dissipate its thermal load relatively easily.
The SEFA was not a spectacular success, being exported to very few countries. It was a case of "too little too late", a 2-hour duration set entering a market already mainly dominated by the German Draeger BG174 (with a 4 hour duration). The SEFA was difficult to service, most parts could only be removed with special tools, and reassembly could be problematic. Testing a SEFA often caused extra work for the operator, as several small leaks in the breathing loop would inevitably arise after servicing and need troubleshooting before the set could be put back in use. Compared to the modern day Draeger PSS BG4 sets, and the American BioPak. which can all be completely stripped and reassembled by hand without using tools, the SEFA is less convenient to maintain.
The SEFA is still in use in the mining industry in India, and up until 2006 was still being used at the Porgera Gold Mine in Papua New Guinea.[ citation needed ]
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It was being designed from 1985 onwards in response to demands from the British coal mining industry for a new make of mines rescue breathing set with longer duration for bulk than an open-circuit set. They were made from 1989 to 2004. Production ceased because of declining demand due to the decline of the British coal mining industry. They are no longer official issue because of lack of availability of spare parts. The British coal industry, when needing rebreathers, now uses a German rebreather made by Draeger.
When photographed these sets were being used without their internal parts during a demonstration of rescue techniques in open air without any gas hazard in the area.
A scuba set is any breathing apparatus that is carried entirely by an underwater diver and provides the diver with breathing gas at the ambient pressure. Scuba is an anacronym for self-contained underwater breathing apparatus. Although strictly speaking the scuba set is only the diving equipment that is required for providing breathing gas to the diver, general usage includes the harness by which it is carried, and those accessories which are integral parts of the harness and breathing apparatus assembly, such as a jacket or wing style buoyancy compensator and instruments mounted in a combined housing with the pressure gauge, and in the looser sense, it has been used to refer to any diving equipment used by the scuba diver, though this would more commonly and accurately be termed scuba equipment or scuba gear. Scuba is overwhelmingly the most common underwater breathing system used by recreational divers and is also used in professional diving when it provides advantages, usually of mobility and range, over surface supplied diving systems, and is allowed by the relevant code of practice.
The timeline of underwater diving technology is a chronological list of notable events in the history of the development of underwater diving equipment. With the partial exception of breath-hold diving, the development of underwater diving capacity, scope, and popularity, has been closely linked to available technology, and the physiological constraints of the underwater environment.
A self-contained breathing apparatus (SCBA), sometimes referred to as a compressed air breathing apparatus (CABA) or simply breathing apparatus (BA), is a device worn to provide breathable air in an atmosphere that is immediately dangerous to life or health. They are typically used in firefighting and industry. The term self-contained means that the SCBA is not dependent on a remote supply of breathing gas. If designed for use under water, it is also known as a Scuba set. When not used underwater, they are sometimes called industrial breathing sets. Unofficial names include air pack, air tank, oxygen cylinder or simply pack, which are mostly used in firefighting.
A rebreather is a breathing apparatus that absorbs the carbon dioxide of a user's exhaled breath to permit the rebreathing (recycling) of the substantially unused oxygen content, and unused inert content when present, of each breath. Oxygen is added to replenish the amount metabolised by the user. This differs from open-circuit breathing apparatus, where the exhaled gas is discharged directly into the environment. The purpose is to extend the breathing endurance of a limited gas supply, and, for covert military use by frogmen or observation of underwater life, eliminating the bubbles produced by an open circuit system. A rebreather is generally understood to be a portable unit carried by the user. The same technology on a vehicle or non-mobile installation is more likely to be referred to as a life-support system.
The Soviet, later Russian IDA71 military and naval rebreather is an oxygen rebreather intended for use by naval and military divers including Russian commando frogmen. As supplied it is in a plain backpack harness with no buoyancy aid. The casing is pressed aluminium with a hinged cover. It has a small optional nitrox cylinder which can be clipped on its outside to convert it to nitrox mode. It contains one oxygen cylinder and two absorbent canisters. In the bottom of its casing is an empty space which is intended for an underwater communications set.
The Clearance Divers Breathing Apparatus (CDBA) is a type of rebreather made by Siebe Gorman in England.
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Scuba diving is a mode of underwater diving whereby divers use breathing equipment that is completely independent of a surface air supply. The name "scuba", an acronym for "Self-Contained Underwater Breathing Apparatus", was coined by Christian J. Lambertsen in a patent submitted in 1952. Scuba divers carry their own source of breathing gas, usually compressed air, affording them greater independence and movement than surface-supplied divers, and more time underwater than free divers. Although the use of compressed air is common, a gas blend with a higher oxygen content, known as enriched air or nitrox, has become popular due to the reduced nitrogen intake during long and/or repetitive dives. Also, breathing gas diluted with helium may be used to reduce the likelihood and effects of nitrogen narcosis during deeper dives.
Dräger is a German company based in Lübeck which makes breathing and protection equipment, gas detection and analysis systems, and noninvasive patient monitoring technologies. Customers include hospitals, fire departments and diving companies.
Mine Safety Appliances, or MSA Safety Incorporated, is an American manufacturer of safety products and special equipment to protect workers exposed to a variety of hazardous conditions in industries such as construction, the military, fire service, and chemical, oil, and gas production.
Porpoise is a tradename for scuba developed by Ted Eldred in Australia and made there from the late 1940s onwards. The first Porpoise was a closed circuit oxygen rebreather, and the following models were all single hose open circuit regulators.
Mine rescue or mines rescue is the specialised job of rescuing miners and others who have become trapped or injured in underground mines because of mining accidents, roof falls or floods and disasters such as explosions.
The Proto is a type of rebreather that was made by Siebe Gorman. It was an industrial breathing set and not suitable for diving. It was made from 1914 or earlier to the 1960s or later.. Also known as proto suits.
An escape set is a breathing set that allows its wearer to survive for a time in an environment without (sufficiently) breathable air.
Vintage scuba is scuba equipment dating from 1975 and earlier, and the practice of diving using such equipment.
CUMA is a make of rebreather underwater breathing set designed and made in Canada for the Canadian Armed Forces by Fullerton Sherwood Engineering Ltd to replace the Royal Navy CDBA.
The Lambertsen Amphibious Respiratory Unit (LARU) is an early model of closed circuit oxygen rebreather used by military frogmen. Christian J. Lambertsen designed a series of them in the US in 1940 and in 1944.
Underwater breathing apparatus is equipment which allows the user to breathe underwater. The three major categories of ambient pressure underwater breathing apparatus are:
Rebreather diving is underwater diving using diving rebreathers, a class of underwater breathing apparatus which recirculate the breathing gas exhaled by the diver after replacing the oxygen used and removing the carbon dioxide metabolic product. Rebreather diving is practiced by recreational, military and scientific divers in applications where it has advantages over open circuit scuba, and surface supply of breathing gas is impracticable. The main advantages of rebreather diving are extended gas endurance, low noise levels, and lack of bubbles.
A Diving rebreather is an underwater breathing apparatus that absorbs the carbon dioxide of a diver's exhaled breath to permit the rebreathing (recycling) of the substantially unused oxygen content, and unused inert content when present, of each breath. Oxygen is added to replenish the amount metabolised by the diver. This differs from open-circuit breathing apparatus, where the exhaled gas is discharged directly into the environment. The purpose is to extend the breathing endurance of a limited gas supply, and, for covert military use by frogmen or observation of underwater life, to eliminate the bubbles produced by an open circuit system. A diving rebreather is generally understood to be a portable unit carried by the user, and is therefore a type of self-contained underwater breathing apparatus (scuba). A semi-closed rebreather carried by the diver may also be known as a gas extender. The same technology on a submersible or surface installation is more likely to be referred to as a life-support system.