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50-519: Aith Lifeboat Station is located at the village of Aith , on the island of Shetland , and is the most northerly of the 238 Royal National Lifeboat Institution Lifeboat Stations. A lifeboat was first stationed here by the RNLI in 1933. Since 1998, the station has operated a Severn-class All-weather lifeboat, 17-14 Charles Lidbury (ON 1232), only the fifth lifeboat to have served at Aith. Despite valiant attempts by Lerwick Life-Saving Company, and even

100-604: A 80 h.p. engine delivering a speed of 8kts. She had previously served for seven years at Longhope , and was named K. T. J. S. (ON 698), in reference to her benefactors, Mr King, Mr Turnball, Mr Jesset and Mrs Sandford. After a year, the RNLI announced that the Aith station was permanent, and a house was constructed for the Mechanic. A new boat was provided to Aith in 1935, a 51-foot Barnett-class lifeboat, constructed at Groves and Guttridge, of Cowes, and costing just over £9000. She

150-519: A detonation wave because they are not capable of closing before the wave passes around the gate. For that reason a flashback arrestor is needed. It is designed to operate before the detonation wave makes it from the hose side to the supply side. Between the regulator and hose, and ideally between hose and torch on both oxygen and fuel lines, a flashback arrestor and/or non-return valve (check valve) should be installed to prevent flame or oxygen-fuel mixture being pushed back into either cylinder and damaging

200-493: A jarl squad and displays by the Shetland Coastguard among other activities. The modern settlement occupies an area originally named Aithsting during the period of Norse occupation. The surrounding parish is still known as Aithsting. On 20 February 2008 several houses in Aith were evacuated due to a fire in the local garage prompting fears that oxyacetylene canisters stored there might explode. The garage

250-413: A large area needs to be heated. It is so-called because the flame at the end looks like a rose bud . A welding torch can also be used to heat small areas such as rusted nuts and bolts. A typical oxy-fuel torch, called an equal-pressure torch, merely mixes the two gases. In an injector torch, high-pressure oxygen comes out of a small nozzle inside the torch head which drags the fuel gas along with it, using

300-427: A mainstay heat source for manual brazing , as well as metal forming , preparation, and localized heat treating. In addition, oxy-fuel cutting is still widely used, both in heavy industry and light industrial and repair operations. In oxy-fuel welding , a welding torch is used to weld metals. Welding metal results when two pieces are heated to a temperature that produces a shared pool of molten metal. The molten pool

350-433: A pressure roughly equivalent to 33 ft (10 m) underwater, water-submerged cutting and welding is reserved for hydrogen rather than acetylene. Tests showed that an oxy-gasoline torch can cut steel plate up to 0.5 in (13 mm) thick at the same rate as oxy-acetylene. In plate thicknesses greater than 0.5 in (13 mm) the cutting rate was better than that of oxy-acetylene; at 4.5 in (110 mm) it

400-562: A single tank (oxy-fuel cutting requires two isolated supplies, fuel and oxygen). Most metals cannot be melted with a single-tank torch. Consequently, single-tank torches are typically suitable for soldering and brazing but not for welding. Oxy-fuel torches are or have been used for: In short, oxy-fuel equipment is quite versatile, not only because it is preferred for some sorts of iron or steel welding but also because it lends itself to brazing, braze-welding, metal heating (for annealing or tempering, bending or forming), rust, or scale removal,

450-531: A special wheeled trolley . There have been examples of oxyhydrogen cutting sets with small ( scuba -sized) gas cylinders worn on the user's back in a backpack harness, for rescue work, and similar. There are also examples of both non-pressurized and pressurized liquid fuel cutting torches, usually using gasoline (petrol). These are used for their increased cutting power over gaseous fuel systems and also greater portability compared to systems requiring two high pressure tanks. The regulator ensures that pressure of

500-412: A spring. Gas flow one way pushes the ball out of the way, and a lack of flow or a reverse flow allows the spring to push the ball into the inlet, blocking it. Not to be confused with a flashback arrestor, a check valve is not designed to block a shock wave. The shock wave could occur while the ball is so far from the inlet that the wave will get past the ball before it can reach its off position. The torch

550-400: Is unstable and may explode . There is about 1,700 kPa (247 psi) pressure in the tank when full. When combined with oxygen , acetyline burns at 3,200 to 3,500 degrees Celsius (5,790 to 6,330 degrees Fahrenheit ), the highest among commonly used gaseous fuels. As a fuel, acetylene's primary disadvantage in comparison to other fuels is its high price. As acetylene is unstable at

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600-403: Is first heated by the flame until it is cherry red. Once this temperature is attained, oxygen is supplied to the heated parts by pressing the oxygen-blast trigger. This oxygen reacts with the metal, producing more heat and forming an oxide which is then blasted out of the cut. It is the heat that continues the cutting process. The cutting torch only heats the metal to start the process; further heat

650-481: Is generally supplied with additional metal called filler. Filler material selection depends upon the metals to be welded. In oxy-fuel cutting , a torch is used to heat metal to its kindling temperature . A stream of oxygen is then trained on the metal, burning it into a metal oxide that flows out of the kerf as dross . Torches that do not mix fuel with oxygen (combining, instead, atmospheric air) are not considered oxy-fuel torches and can typically be identified by

700-471: Is green and the fuel hose is red. In the UK and other countries, the oxygen hose is blue (black hoses may still be found on old equipment), and the acetylene (fuel) hose is red. If liquefied petroleum gas (LPG) fuel, such as propane , is used, the fuel hose should be orange, indicating that it is compatible with LPG. LPG will damage an incompatible hose, including most acetylene hoses. The threaded connectors on

750-418: Is high, about 2,000 °C for hydrogen gas in air at atmospheric pressure, and up to 2800 °C when pre-mixed in a 2:1 ratio with pure oxygen (oxyhydrogen). Hydrogen is not used for welding steels and other ferrous materials, because it causes hydrogen embrittlement . For some oxyhydrogen torches the oxygen and hydrogen are produced by electrolysis of water in an apparatus which is connected directly to

800-492: Is more volatile, with a boiling point of -42 °C. Vaporization is rapid at temperatures above the boiling points. The calorific (heat) values of the two are almost equal. Both are thus mixed to attain the vapor pressure that is required by the end user and depending on the ambient conditions. If the ambient temperature is very low, propane is preferred to achieve higher vapor pressure at the given temperature. Propane does not burn as hot as acetylene in its inner cone, and so it

850-473: Is not recommended for cutting applications, because beads of molten metal given off by the process can become lodged between the hoses where they are held together, and burn through, releasing the pressurized gas inside, which in the case of fuel gas usually ignites. The hoses are color-coded for visual identification. The color of the hoses varies between countries. In the United States, the oxygen hose

900-439: Is often a substantial advantage to cutting with an injector torch (see the propane section) rather than an equal-pressure torch when using propylene. Quite a few North American suppliers have begun selling propylene under proprietary trademarks such as FG2 and Fuel-Max. Butane , like propane , is a saturated hydrocarbon. Butane and propane do not react with each other and are regularly mixed. Butane boils at 0.6 °C. Propane

950-432: Is provided by the burning metal. The melting point of the iron oxide is around half that of the metal being cut. As the metal burns, it immediately turns to liquid iron oxide and flows away from the cutting zone. However, some of the iron oxide remains on the workpiece, forming a hard "slag" which can be removed by gentle tapping and/or grinding. A rose bud torch is used to heat metals for bending, straightening, etc. where

1000-446: Is rarely used for welding. Propane, however, has a very high number of BTUs per cubic foot in its outer cone, and so with the right torch ( injector style ) can make a faster and cleaner cut than acetylene, and is much more useful for heating and bending than acetylene. The maximum neutral flame temperature of propane in oxygen is 2,822 °C (5,112 °F). Propane is cheaper than acetylene and easier to transport. The following

1050-426: Is specifically forbidden in the UK and other countries. Acetylene is not just flammable; in certain conditions it is explosive . Although it has an upper flammability limit in air of 81%, acetylene's explosive decomposition behaviour makes this irrelevant. If a detonation wave enters the acetylene tank, the tank will be blown apart by the decomposition. Ordinary check valves that normally prevent backflow cannot stop

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1100-474: Is the fuel of choice for repair work and general cutting and welding. Acetylene gas is shipped in special cylinders designed to keep the gas dissolved. The cylinders are packed with porous materials (e.g. kapok fibre, diatomaceous earth , or (formerly) asbestos ), then filled to around 50% capacity with acetone , as acetylene is soluble in acetone. This method is necessary because above 207 kilopascals (30 pounds per square inch ) (absolute pressure), acetylene

1150-411: Is the tool that the welder holds and manipulates to make the weld. It has a connection and valve for the fuel gas and a connection and valve for the oxygen, a handle for the welder to grasp, and a mixing chamber (set at an angle) where the fuel gas and oxygen mix, with a tip where the flame forms. Two basic types of torches are positive pressure type and low pressure or injector type. A welding torch head

1200-612: Is therefore much less dangerous than acetylene. Further, more of it can be stored in a single place at one time, as the increased compressibility allows for more gas to be put into a tank. MAPP gas can be used at much higher pressures than acetylene, sometimes up to 40 or 50 psi in high-volume oxy-fuel cutting torches which can cut up to 12-inch-thick (300 mm) steel. Other welding gases that develop comparable temperatures need special procedures for safe shipping and handling. MPS and MAPP are recommended for cutting applications in particular, rather than welding applications. On 30 April 2008

1250-408: Is used to weld metals. It can be identified by having only one or two pipes running to the nozzle, no oxygen-blast trigger, and two valve knobs at the bottom of the handle letting the operator adjust the oxygen and fuel flow respectively. A cutting torch head is used to cut materials. It is similar to a welding torch, but can be identified by the oxygen blast trigger or lever. When cutting, the metal

1300-467: Is using air bubbled through a gasoline container by a foot-operated air pump, and burning the fuel-air mixture in a specialized welding torch. Diesel is a new option in the liquid fuel cutting torch market. Diesel torches claim several advantages over gaseous fuels and gasoline. Diesel is inherently safer and more powerful than gasoline or gaseous fuel such as acetylene and propane, and will cut steel faster and cheaper than either of those gases. In addition,

1350-623: The Stromness lifeboat stationed 120 miles away, wrecks such as that of the Aberdeen fishing trawler Ben Doran in March 1930, with the loss of all 9 crew, prompted the RNLI to station a lifeboat in Lerwick , and to look for a location to station a second lifeboat on the west of Shetland. It was decided to station a boat at Aith, as the village could provide sufficient crew, and because Aith Voe

1400-492: The Venturi effect . Oxy-fuel processes may use a variety of fuel gases (or combustible liquids), the most common being acetylene . Other gases that may be used are propylene , liquified petroleum gas (LPG), propane, natural gas , hydrogen , and MAPP gas . Liquid fuel cutting systems use such fuels as Gasoline (Petrol) Diesel, Kerosene and possibly some aviation fuels. Acetylene is the primary fuel for oxy-fuel welding and

1450-656: The 1967 Maud Smith Award. The following are awards made at Aith Aith Aith , ( Shetland dialect : Eid, Old Norse : Eið , meaning Isthmus, cf Eday ), is a village on the Northern coast of the West Shetland Mainland , Scotland at the southern end of Aith Voe, some 21 miles (34 kilometres) west of Lerwick . Aith lies on the B9071 that runs south to the junction with the A971 (which links Lerwick to

1500-555: The Petromont Varennes plant closed its methylacetylene/propadiene crackers. As it was the only North American plant making MAPP gas, many substitutes were introduced by companies that had repackaged the Dow and Varennes product(s) - most of these substitutes are propylene, see below. Propylene is used in production welding and cutting. It cuts similarly to propane. When propylene is used, the torch rarely needs tip cleaning. There

1550-498: The calibration of the adjustment knob. The cheaper single-stage regulators may sometimes omit the cylinder contents gauge, or replace the accurate dial gauge with a cheaper and less precise "rising button" gauge. The hoses are designed for use in welding and cutting metal. A double-hose or twinned design can be used, meaning that the oxygen and fuel hoses are joined. If separate hoses are used, they should be clipped together at intervals approximately 3 feet (1 m) apart, although that

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1600-405: The case of gas tungsten arc welding , the capability of welding very reactive metals such as titanium . Oxy-acetylene welding is still used for metal-based artwork and in smaller home-based shops, as well as situations where accessing electricity (e.g., via an extension cord or portable generator) would present difficulties. The oxy-acetylene (and other oxy-fuel gas mixtures) welding torch remains

1650-492: The cylinder falling as the gas in it is consumed. This is similar to the first stage of a scuba-diving regulator . The adjustable second stage of the regulator controls the pressure reduction from the intermediate pressure to the low outlet pressure. The regulator has two pressure gauges, one indicating cylinder pressure, the other indicating hose pressure. The adjustment knob of the regulator is sometimes roughly calibrated for pressure, but an accurate setting requires observation of

1700-556: The early 20th century, before the development and availability of coated arc welding electrodes in the late 1920s that were capable of making sound welds in steel, oxy-acetylene welding was the only process capable of making welds of exceptionally high quality in virtually all metals in commercial use at the time. These included not only carbon steel but also alloy steels, cast iron , aluminium , and magnesium . In recent decades it has been superseded in almost all industrial uses by various arc welding methods offering greater speed and, in

1750-428: The equipment or causing a cylinder to explode. European practice is to fit flashback arrestors at the regulator and check valves at the torch. US practice is to fit both at the regulator. The flashback arrestor prevents shock waves from downstream coming back up the hoses and entering the cylinder, possibly rupturing it, as there are quantities of fuel/oxygen mixtures inside parts of the equipment (specifically within

1800-407: The gas from the tanks matches the required pressure in the hose. The flow rate is then adjusted by the operator using needle valves on the torch. Accurate flow control with a needle valve relies on a constant inlet pressure. Most regulators have two stages. The first stage is a fixed-pressure regulator, which releases gas from the cylinder at a constant intermediate pressure, despite the pressure in

1850-433: The gauge. Some simpler or cheaper oxygen-fuel regulators have only a single-stage regulator, or only a single gauge. A single-stage regulator will tend to allow a reduction in outlet pressure as the cylinder is emptied, requiring manual readjustment. For low-volume users, this is an acceptable simplification. Welding regulators, unlike simpler LPG heating regulators, retain their outlet (hose) pressure gauge and do not rely on

1900-471: The hoses are handed to avoid accidental mis-connection: the thread on the oxygen hose is right-handed (as normal), while the fuel gas hose has a left-handed thread. The left-handed threads also have an identifying groove cut into their nuts. Gas-tight connections between the flexible hoses and rigid fittings are made by using crimped hose clips or ferrules , often referred to as 'O' clips, over barbed spigots. The use of worm-drive hose clips or Jubilee Clips

1950-479: The liquid fuel vapor is about 5 times the density of a gaseous fuel, providing much greater "punch". A high velocity cutting flame is produced by the huge volume expansion when the liquid transitions to a vapor, so the cutting flame will easily cut across air voids between plates. A diesel/oxygen torch can cut through paint, dirt, rust and other surface contaminants on steel. This system provides almost 100% oxidation during cutting so it leaves virtually no molten steel in

2000-416: The loosening of corroded nuts and bolts, and is a ubiquitous means of cutting ferrous metals. The apparatus used in gas welding consists basically of an oxygen source and a fuel gas source (usually contained in cylinders ), two pressure regulators and two flexible hoses (one for each cylinder), and a torch. This sort of torch can also be used for soldering and brazing . The cylinders are often carried in

2050-421: The mixer and blowpipe/nozzle) that may explode if the equipment is incorrectly shut down, and acetylene decomposes at excessive pressures or temperatures. In case the pressure wave has created a leak downstream of the flashback arrestor, it will remain switched off until someone resets it. A check valve lets gas flow in one direction only. It is usually a chamber containing a ball that is pressed against one end by

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2100-513: The slag to prevent "sticking" together cut material. Operating cost for a gasoline torch is typically 75-90% less than using propane or Acetylene. The gasoline can be fed either from a pressurized tank (whose pressure can be hand-pumped or fed from a gas cylinder) or a non-pressurized tank, with the fuel being drawn into the torch by a venturi action created by the pressurized oxygen flow. Another low cost approach commonly used by jewelry makers in Asia

2150-484: The slag, preventing the "sticking together" of the cut materials. The operating cost for a diesel torch is typically 75-90% less than using propane or acetylene. Growing use in the demolition or scrap industries Hydrogen has a clean flame and is good for use on aluminium . It can be used at a higher pressure than acetylene and is therefore useful for underwater welding and cutting. It is a good type of flame to use when heating large amounts of material. The flame temperature

2200-531: The torch. Types of this sort of torch: Methylacetylene-propadiene (MAPP) gas and LPG gas are similar fuels, because LPG gas is liquefied petroleum gas mixed with MPS. It has the storage and shipping characteristics of LPG and has a heat value a little lower than that of acetylene. Because it can be shipped in small containers for sale at retail stores, it is used by hobbyists and large industrial companies and shipyards because it does not polymerize at high pressures — above 15 psi or so (as acetylene does) and

2250-664: The west of Shetland) at the village of Bixter and North East via East Burrafirth to the junction with the A970 (which links Lerwick to the North) at the village of Voe . A single track road leads north from Aith along the west shoreline of Aith Voe to Vementry . Every year in early June the Aith Lifeboat Gala is held to raise money for the Royal National Lifeboat Institution , featuring

2300-703: The west side of Papa Stour . Considerable skill, navigation and seamanship in force 8 conditions was required to bring the lifeboat to the side of Juniper , and to effect the rescue of the 12 crew. The lifeboat, crew and survivors landed in Aith at 9:35am. For this service, Coxswain John R. Nicholson was awarded the RNLI Silver Medal , the rest of the crew being awarded "The Thanks of the Institution inscribed on Vellum". Coxswain Nicholson would later receive

2350-418: Was destroyed and the site later cleared. Oxyacetylene A common propane /air flame burns at about 2,250 K (1,980 °C; 3,590 °F), a propane/oxygen flame burns at about 2,526 K (2,253 °C; 4,087 °F), an oxyhydrogen flame burns at 3,073 K (2,800 °C; 5,072 °F) and an acetylene /oxygen flame burns at about 3,773 K (3,500 °C; 6,332 °F). During

2400-523: Was one of the most sheltered mooring locations on the west coast. James Tait, DSM, was appointed Coxswain, another James Tait appointed Second Coxswain, and William Tait appointed Bowman. Charles Mowat, Assistant Mechanic at Lerwick, was appointed to be Aith Mechanic. The first boat on station in January 1933, and was a 45ft 6in Watson-class lifeboat, built in 1926 by S. E. Saunders of Cowes, with

2450-614: Was the gift of Miss Maggie Rankin, made in memory of her brothers, both Marine Engineers from Greenock, and was named The Rankin (ON 776) on 12 May 1935. In 25 years of service, she was launched 52 times, and saved 61 lives. Just before 6:00am on the morning of 19 February 1967, the James and Frances Macfarlane (ON 956) was launched to the aid of the Aberdeen trawler Juniper , which had run aground in Lyra Sound, between Lyra Skerry and

2500-501: Was three times faster. Additionally the liquid fuel vapour is about 4x the density of a gaseous fuel. A high velocity cutting flame is produced by the huge volume expansion while the liquid transitions to a vapour so the cutting flame can cut across voids (air space between plates). Oxy-gasoline torches can also cut through paint, dirt, rust and other contaminating surface materials coating old steel. This system provides almost 100% oxidation during cutting, leaving almost no molten steel in

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