Oxy-fuel welding (commonly called oxyacetylene welding, oxy welding, or gas welding in the U.S.) and oxy-fuel cutting are processes that use fuel gases (or liquid fuels such as gasoline) and oxygen to weld or cut metals. French engineers Edmond Fouché and Charles Picard became the first to develop oxygen-acetylene welding in 1903. Pure oxygen, instead of air, is used to increase the flame temperature to allow localized melting of the workpiece material (e.g. steel) in a room environment. 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 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, aluminum, and magnesium. In recent decades it has been superseded in almost all industrial uses by various arc welding methods offering greater speed and, in the case of gas tungsten arc welding, the capability of welding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 a mainstay heat source for manual brazing and braze welding, 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. (See Oxy Gasoline Cutting )
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 is generally supplied with additional metal called filler. Filler material depends upon the metals to be welded.
Torches that do not mix fuel with oxygen (combining, instead, atmospheric air) are not considered oxy-fuel torches and can typically be identified by 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, 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 a special wheeled trolley.
There are also examples of pressurized liquid fuel cutting torches, usually using gasoline. These are used for their increased portability.
The regulator ensures that pressure of 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 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 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 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 together. If separate hoses are used, they should be clipped together at intervals approximately 3 feet (1 m) apart, although that 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 pressurised 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 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 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 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 back flow cannot stop 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 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 (not to be confused with a check valve) 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 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 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 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 is used to weld metals those are difficult to weld by using electrode. 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 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, forming an oxide and producing heat. It is the heat that continues the cutting process. The cutting torch only heats the metal to start the process; further heat 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 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 the venturi effect.
Oxy-fuel processes may use a variety of fuel gases, the most common being acetylene. Other gases that may be used are propylene, liquified petroleum gas (LPG), propane, natural gas, hydrogen, and MAPP gas. Many brands use different kinds of gases in their mixes.
Acetylene is the primary fuel for oxy-fuel welding and 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 kPa (30 lbf/in²) (absolute pressure) acetylene is unstable and may explode.
There is about 1700 kPa (250 psi) pressure in the tank when full. Acetylene when combined with oxygen burns at 3200 °C to 3500 °C (5800 °F to 6300 °F), highest among commonly used gaseous fuels. As a fuel acetylene's primary disadvantage, in comparison to other fuels, is high cost.
As acetylene is unstable at a pressure roughly equivalent to 33 feet/10 meters underwater, water-submerged cutting and welding is reserved for hydrogen rather than acetylene.
Oxy-gasoline, also known as oxy-petrol, torches have been found to perform very well, especially where bottled gas fuel is not available or difficult to transport to the worksite. 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 was three times faster.
The gasoline is fed either from a pressurised tank (whose pressure can be hand-pumped or fed from a gas cylinder). OR from a non pressurised tank with the fuel being drawn into the torch by venturi action by the pressurised oxygen flow. Another low cost approach commonly used by jewelry makers in Asia 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.
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 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 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 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 31 April 2008 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 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 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 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.
Oxygen is not the fuel. It is what chemically combines with the fuel to produce the heat for welding. This is called 'oxidation', but the more specific and more commonly used term in this context is 'combustion'. In the case of hydrogen, the product of combustion is simply water. For the other hydrocarbon fuels, water and carbon dioxide are produced. The heat is released because the molecules of the products of combustion have a lower energy state than the molecules of the fuel and oxygen. In oxy-fuel cutting, oxidation of the metal being cut (typically iron) produces nearly all of the heat required to "burn" through the workpiece.
Oxygen is usually produced elsewhere by distillation of liquefied air and shipped to the welding site in high-pressure vessels (commonly called "tanks" or "cylinders") at a pressure of about 21,000 kPa (3,000 lbf/in² = 200 atmospheres). It is also shipped as a liquid in Dewar type vessels (like a large Thermos jar) to places that use large amounts of oxygen.
It is also possible to separate oxygen from air by passing the air, under pressure, through a zeolite sieve that selectively adsorbs the nitrogen and lets the oxygen (and argon) pass. This gives a purity of oxygen of about 93%. This method works well for brazing, but higher-purity oxygen is necessary to produce a clean, slag-free kerf when cutting.
The welder can adjust the oxy-acetylene flame to be carbonizing (aka reducing), neutral, or oxidizing. Adjustment is made by adding more or less oxygen to the acetylene flame. The neutral flame is the flame most generally used when welding or cutting. The welder uses the neutral flame as the starting point for all other flame adjustments because it is so easily defined. This flame is attained when welders, as they slowly open the oxygen valve on the torch body, first see only two flame zones. At that point, the acetylene is being completely burned in the welding oxygen and surrounding air. The flame is chemically neutral. The two parts of this flame are the light blue inner cone and the darker blue to colorless outer cone. The inner cone is where the acetylene and the oxygen combine. The tip of this inner cone is the hottest part of the flame. It is approximately 6,000 °F (3,300 °C) and provides enough heat to easily melt steel. In the inner cone the acetylene breaks down and partly burns to hydrogen and carbon monoxide, which in the outer cone combine with more oxygen from the surrounding air and burn.
An excess of acetylene creates a carbonizing flame. This flame is characterized by three flame zones; the hot inner cone, a white-hot "acetylene feather", and the blue-colored outer cone. This is the type of flame observed when oxygen is first added to the burning acetylene. The feather is adjusted and made ever smaller by adding increasing amounts of oxygen to the flame. A welding feather is measured as 2X or 3X, with X being the length of the inner flame cone. The unburned carbon insulates the flame and drops the temperature to approximately 5,000 °F (2,800 °C). The reducing flame is typically used for hard facing operations or backhand pipe welding techniques. The feather is caused by incomplete combustion of the acetylene to cause an excess of carbon in the flame. Some of this carbon is dissolved by the molten metal to carbonize it. The carbonizing flame will tend to remove the oxygen from iron oxides which may be present, a fact which has caused the flame to be known as a "reducing flame".
The oxidizing flame is the third possible flame adjustment. It occurs when the ratio of oxygen to acetylene required for a neutral flame has been changed to give an excess of oxygen. This flame type is observed when welders add more oxygen to the neutral flame. This flame is hotter than the other two flames because the combustible gases will not have to search so far to find the necessary amount of oxygen, nor heat up as much thermally inert carbon. It is called an oxidizing flame because of its effect on metal. This flame adjustment is generally not preferred. The oxidizing flame creates undesirable oxides to the structural and mechanical detriment of most metals. In an oxidizing flame, the inner cone acquires a purplish tinge and gets pinched and smaller at the tip, and the sound of the flame gets harsh. A slightly oxidizing flame is used in braze-welding and bronze-surfacing while a more strongly oxidizing flame is used in fusion welding certain brasses and bronzes
The size of the flame can be adjusted to a limited extent by the valves on the torch and by the regulator settings, but in the main it depends on the size of the orifice in the tip. In fact, the tip should be chosen first according to the job at hand, and then the regulators set accordingly.
The flame is applied to the base metal and held until a small puddle of molten metal is formed. The puddle is moved along the path where the weld bead is desired. Usually, more metal is added to the puddle as it is moved along by dipping metal from a welding rod or filler rod into the molten metal puddle. The metal puddle will travel towards where the metal is the hottest. This is accomplished through torch manipulation by the welder.
The amount of heat applied to the metal is a function of the welding tip size, the speed of travel, and the welding position. The flame size is determined by the welding tip size. The proper tip size is determined by the metal thickness and the joint design.
Welding gas pressures using oxy-acetylene are set in accordance with the manufacturer's recommendations. The welder will modify the speed of welding travel to maintain a uniform bead width. Uniformity is a quality attribute indicating good workmanship. Trained welders are taught to keep the bead the same size at the beginning of the weld as at the end. If the bead gets too wide, the welder increases the speed of welding travel. If the bead gets too narrow or if the weld puddle is lost, the welder slows down the speed of travel. Welding in the vertical or overhead positions is typically slower than welding in the flat or horizontal positions.
The welder must add the filler rod to the molten puddle. The welder must also keep the filler metal in the hot outer flame zone when not adding it to the puddle to protect filler metal from oxidation. Do not let the welding flame burn off the filler metal. The metal will not wet into the base metal and will look like a series of cold dots on the base metal. There is very little strength in a cold weld. When the filler metal is properly added to the molten puddle, the resulting weld will be stronger than the original base metal.
Welding lead or 'lead burning' was much more common in the 19th century to make some pipe connections and tanks. Great skill is required but can be quickly learned. In building construction today some lead flashing is welded but soldered copper flashing is much more common in America. In the automotive body collision industry before the 1980s, oxyacetylene gas torch welding was seldom used to weld sheetmetal, since warpage was a byproduct besides the excess heat. Automotive body repair methods at the time were crude and yielded improprieties until MIG welding became the industry standard. Since the 1970s, when high strength steel became the standard for automotive manufacturing, electric welding became the preferred method. After the 1980s, the oxyacetylene torch fell out of use for sheetmetal welding in the industrialized world.
For cutting, the setup is a little different. A cutting torch has a 60- or 90-degree angled head with orifices placed around a central jet. The outer jets are for preheat flames of oxygen and acetylene. The central jet carries only oxygen for cutting. The use of several preheating flames rather than a single flame makes it possible to change the direction of the cut as desired without changing the position of the nozzle or the angle which the torch makes with the direction of the cut, as well as giving a better preheat balance. Manufacturers have developed custom tips for Mapp, propane, and propylene gases to optimize the flames from these alternate fuel gases.
The flame is not intended to melt the metal, but to bring it to its ignition temperature.
The torch's trigger blows extra oxygen at higher pressures down the torch's third tube out of the central jet into the workpiece, causing the metal to burn and blowing the resulting molten oxide through to the other side. The ideal kerf is a narrow gap with a sharp edge on either side of the workpiece; overheating the workpiece and thus melting through it causes a rounded edge.
Cutting is initiated by heating the edge or leading face (as in cutting shapes such as round rod) of the steel to the ignition temperature (approximately bright cherry red heat) using the pre-heat jets only, then using the separate cutting oxygen valve to release the oxygen from the central jet. The oxygen chemically combines with the iron in the ferrous material to oxidize the iron quickly into molten iron oxide, producing the cut. Initiating a cut in the middle of a workpiece is known as piercing.
It is worth noting several things at this point:
For a basic oxy-acetylene rig, the cutting speed in light steel section will usually be nearly twice as fast as a petrol-driven cut-off grinder. The advantages when cutting large sections are obvious: an oxy-fuel torch is light, small and quiet and needs very little effort to use, whereas a cut-off grinder is heavy and noisy and needs considerable operator exertion and may vibrate severely, leading to stiff hands and possible long-term vibration white finger. Oxy-acetylene torches can easily cut through ferrous materials in excess of 200 mm (8 inches). Oxygen lances are used in scrapping operations and cut sections thicker than 200 mm (8 inches). Cut-off grinders are useless for these kinds of application.
Robotic oxy-fuel cutters sometimes use a high-speed divergent nozzle. This uses an oxygen jet that opens slightly along its passage. This allows the compressed oxygen to expand as it leaves, forming a high-velocity jet that spreads less than a parallel-bore nozzle, allowing a cleaner cut. These are not used for cutting by hand since they need very accurate positioning above the work. Their ability to produce almost any shape from large steel plates gives them a secure future in shipbuilding and in many other industries.
Oxy-propane torches are usually used for cutting up scrap to save money, as LPG is far cheaper joule for joule than acetylene, although propane does not produce acetylene's very neat cut profile. Propane also finds a place in production, for cutting very large sections.
Oxy-acetylene can cut only low- to medium-carbon steels and wrought iron. High-carbon steels are difficult to cut because the melting point of the slag is closer to the melting point of the parent metal, so that the slag from the cutting action does not eject as sparks but rather mixes with the clean melt near the cut. This keeps the oxygen from reaching the clean metal and burning it. In the case of cast iron, graphite between the grains and the shape of the grains themselves interfere with the cutting action of the torch. Stainless steels cannot be cut either because the material does not burn readily.
Oxyacetylene welding/cutting is not difficult, but there are a good number of subtle safety points that should be learned such as:
Proper protection such as welding goggles should be worn at all times, including to protect the eyes against glare and flying sparks. Special safety eyewear must be used—both to protect the welder and to provide a clear view through the yellow-orange flare given off by the incandescing flux. In the 1940s cobalt melters’ glasses were borrowed from steel foundries and were still available until the 1980s. However, the lack of protection from impact, ultra-violet, infrared and blue light caused severe eyestrain and eye damage. Didymium eyewear, developed for glassblowers in the 1960s, was also borrowed—until many complained of eye problems from excessive infrared, blue light, and insufficient shading. Today very good eye protection can be found designed especially for gas-welding aluminum that cuts the sodium orange flare completely and provides the necessary protection from ultraviolet, infrared, blue light and impact, according to ANSI Z87-1989 safety standards for a Special Purpose Lens.
Fuel and oxygen tanks should be fastened securely and upright to a wall, post, or portable cart. An oxygen tank is especially dangerous because the gas is stored at a pressure of 21 MPa (3000 lbf/in² = 200 atmospheres) when full. If the tank falls over and damages the valve, the tank can be jettisoned by the compressed oxygen escaping the cylinder at high speed. Tanks in this state are capable of breaking through a brick wall. For this reason, never move an oxygen tank around without its valve cap screwed in place.
On an oxyacetylene torch system there are three types of valves: the tank valve, the regulator valve, and the torch valve. Each gas in the system will have each of these three valves. The regulator converts the high pressure gas inside of the tanks to a low pressure stream suitable for welding. Acetylene cylinders must be maintained in an upright position to prevent the internal acetone and acetylene from separating in the filler material.
A less obvious hazard of welding is exposure to harmful chemicals. Exposure to certain metals, metal oxides, or carbon monoxide can often lead to severe medical conditions. Damaging chemicals can be produced from the fuel, from the work-piece, or from a protective coating on the work-piece. By increasing ventilation around the welding environment, the welders will have much less exposure to harmful chemicals from any source.
The most common fuel used in welding is acetylene, which has a two-stage reaction. The primary chemical reaction involves the acetylene disassociating in the presence of oxygen to produce heat, carbon monoxide, and hydrogen gas: C2H2 + O2 → 2CO + H2. A secondary reaction follows where the carbon monoxide and hydrogen combine with more oxygen to produce carbon dioxide and water vapor. When the secondary reaction does not burn all of the reactants from the primary reaction, the welding process can produce large amounts of carbon monoxide, and it often does. Carbon monoxide is also the byproduct of many other incomplete fuel reactions.
Almost every piece of metal is an alloy of one type or another. Copper, aluminium, and other base metals are occasionally alloyed with beryllium, which is a highly toxic metal. When a metal like this is welded or cut, high concentrations of toxic beryllium fumes are released. Long-term exposure to beryllium may result in shortness of breath, chronic cough, and significant weight loss, accompanied by fatigue and general weakness. Other alloying elements such as arsenic, manganese, silver, and aluminium can cause sickness to those who are exposed.
More common are the anti-rust coatings on many manufactured metal components. Zinc, cadmium, and fluorides are often used to protect irons and steels from oxidizing. Galvanized metals have a very heavy zinc coating. Exposure to zinc oxide fumes can lead to a sickness named "metal fume fever". This condition rarely lasts longer than 24 hours, but severe cases can be fatal. Not unlike common influenza, fevers, chills, nausea, cough, and fatigue are common effects of high zinc oxide exposure.
Flashback is the condition of the flame propagating down the hoses of an oxy-fuel welding and cutting system. To prevent such a situation a flashback arrestor is usually employed. The flame burns backwards into the hose, causing a popping or squealing noise. It can cause an explosion in the hose with the potential to injure or kill the operator. Using a lower pressure than recommended can cause a flashback.
The term blowpipe refers to one of several tools used to direct streams of gases into any of several working media.Blowtorch
A blowtorch (U.S. and Australia), or blowlamp (UK), is a fuel-burning tool used for applying flame and heat to various applications, usually metalworking.
Early blowtorches used liquid fuel, carried in a refillable reservoir attached to the lamp. Modern blowtorches are mostly gas-fuelled. Their fuel reservoir is disposable or refillable by exchange. The term "blowlamp" usually refers to liquid-fuelled torches still used in the UK. Liquid-fuelled torches are pressurized by a piston hand pump, while gas torches are self-pressurized by the fuel evaporation.
Fuel torches are available in a vast range of size and output power. The term blowtorch applies to the smaller and lower temperature range of these. Blowtorches are typically a single hand-held unit, with their draught supplied by a natural draught of air. The larger torches may have a heavy fuel reservoir placed on the ground, connected by a hose. This is common for butane- or propane-fuelled gas torches, but also applies to the older, large liquid paraffin (kerosene) torches such as the Wells light.
Many torches now use a hose-supplied gas feed, which is often mains gas. They may also have a forced-air supply, from either an air blower or an oxygen cylinder. Both of these larger and more powerful designs are less commonly described as blowtorches, while the term blowtorch is usually reserved for the smaller and less powerful self-contained torches. The archaic term "blowpipe" is sometimes still used in relation to oxy-acetylene welding torches.
(British English uses the word "blowtorch" to mean a cutting torch as used for cutting metal, often any oxy-fuel welding and cutting torch.)Butane torch
A butane torch is a tool which creates an intensely hot flame using butane, a flammable gas.
Consumer air butane torches are often claimed to develop flame temperatures up to approximately 1,430 °C (2,610 °F). This temperature is high enough to melt many common metals, such as aluminum and copper, and hot enough to vaporize many organic compounds as well.Flashback
Flashback or flashbacks may refer to:
Flashback (narrative), in literature and dramatic media, an interjected scene or point that takes the narrative back in time from the current point
Flashback episode, an episode of a television series that consists primarily of excerpts from previous episodes
Flashback (psychology), in which a memory is suddenly and unexpectedly revisited
Acid flashback, a reported psychological phenomenon in which an individual experiences an episode of some of LSD's subjective effects long after the drug has worn off
Flashback (welding), a dangerous hazard of using an oxyacetylene torch
Flashback arrestor, a device most commonly used in oxy-fuel welding and cutting to stop the flame from burning back up into the equipmentFlashback arrestor
A flashback arrestor or flash arrestor is a gas safety device most commonly used in oxy-fuel welding and cutting to stop the flame or reverse flow of gas back up into the equipment or supply line. It protects the user and equipment from damage or explosions. These devices are mainly used in industrial processes where oxy-fuel gas mixtures are handled and used. Flashback arrestors as safety products are essential to secure the workplaces and working environment. In former times wet flashback arrestors were also used. Today the industry standard is to use dry flashback arrestors with at least two safety elements.Injector (disambiguation)
Injector may refer to:
Injector or steam injector, a pump-like device without moving parts
Jet injector, a medical hypodermic device
a type of welding and cutting torch in oxy-fuel welding and cutting
Sample injector, a device used in conjunction with injecting samples into high-performance liquid chromatography or similar chromatography apparatus
Fuel injector, a device used in many modern vehicle engines
Injector Linux, a one floppy Linux system (Lightweight Linux distribution)
a program used to perform DLL injection.Kerf (disambiguation)
Kerf is the width of a saw cut.
Kerf may also refer to:
Kerf, molten metal and metal oxide blown out when metal is cut by an oxy-gas torch: see Oxy-fuel welding and cutting
Kerf (sculpture), a pair of cast-concrete works by Thomas Sayre in Portland, Oregon, US
Kerf, a poetry collection by Peter Sanger
Kerf dust, a byproduct of sawing silicon ingots into wafers, esp. in production of Photovoltaics
The Kerf, a poetry publication of the College of the Redwoods, Del Norte Center for Writing in Crescent City, California
Kerala E.N.T. Research Foundation (KERF), a hospital at Kollam in Kerala, IndiaMAPP gas
"MAPP gas" is a trademarked name, belonging to The Linde Group, and previously belonging to the Dow Chemical Company, for a fuel gas based on a stabilized mixture of methylacetylene (propyne) and propadiene. The name comes from the original chemical composition, methylacetylene-propadiene propane. "MAPP gas" is also widely used as a generic name for UN 1060 stabilised methylacetylene-propadiene (unstabilised methylacetylene-propadiene is known as MAPD). MAPP gas is widely regarded as a safer and easier-to-use substitute for acetylene. In early 2008, true MAPP gas production ended in North America when production was discontinued at the only remaining plant in North America that still manufactured it. However, many current products labeled "MAPP" are, in fact, MAPP substitutes. These versions are composed almost entirely of propylene with minuscule impurities of propane (<0.5%).Methylacetylene-propadiene gas
Methylacetylene-propadiene (MPS) gas is a type of fuel gas used in oxy-fuel welding and cutting torches. The most commonly known type of MPS gas was MAPP gas.This gas was a mixture of propyne, CH3C≡CH, and propadiene, CH2=C=CH2. As a fuel gas, it burned hotter than propylene, propane or natural gas. It also had better heat distribution than acetylene.Oxidizing and reducing flames
In various burners, the oxidizing flame is the flame produced with an excessive amount of oxygen. When the amount of oxygen increases, the flame shortens, its color darkens, and it hisses and roars. With some exceptions (e.g., platinum soldering in jewelry), the oxidizing flame is usually undesirable for welding and soldering, since, as its name suggests, it oxidizes the metal's surface. The same principle is important in firing pottery—see Reducing atmosphere.
The reducing flame is the flame with low oxygen. It has a yellow or yellowish color due to carbon or hydrocarbons which bind with (or reduce) the oxygen contained in the materials processed with the flame. The reducing flame is also called the carburizing flame, since it tends to introduce carbon into the molten metal.
The neutral flame is the flame in which the amount of oxygen is precisely enough for burning, and neither oxidation nor reduction occurs. A flame with a good balance of oxygen is clear blue.
The reducing and neutral flames are useful in soldering and annealing.Pressure regulator
A pressure regulator is a control valve that reduces the input pressure of a fluid to a desired value at its output.
Regulators are used for gases and liquids, and can be an integral device with an output pressure setting, a restrictor and a sensor all in the one body, or consist of a separate pressure sensor, controller and flow valve.Rosebud
Rosebud may refer to:
Rose bud, the bud of a rose flowerWelded sculpture
Welded sculpture (related to visual art and works of art) is an art form in which sculpture is made using welding techniques.Welding goggles
Welding goggles provide a degree of eye protection while some forms of welding and cutting are being done. They are intended to protect the eyes not only from the heat and optical radiation produced by the welding, such as the intense ultraviolet light produced by an electric arc, but also from sparks or debris. A full facemask may be required for arc welding.
Welding and cutting processes, including arc welding and cutting, as well as brazing produce intense ultraviolet (UV), infrared (IR) and visible light wavelengths. The UV and IR wavelengths cannot be seen and can produce eye injury without the victim realizing it immediately. Extremely dark filters of the proper sort are needed for the welder to be able to look at the intensely glowing metal being welded. An approved face shield or welding helmet can also have filters for optical radiation protection, and offer additional protection against debris and sparks. UV blocking protective spectacles with side shields or welding goggles are considered primary protection, with the face shield or welding helmet considered secondary protection. This way, the eyes are still protected even when the face shield or helmet is lifted up.The optical filter in welding goggles, face mask or helmet must be a type which is suitable for the sort of work being done. A filter suitable for gas welding, for instance, should not be used for arc welding. Face masks which are self dimming are available for arc welding, MIG, TIG, and plasma cutting, and allow better vision before the arc is struck and after it is extinguished. Failure to use such protection when arc welding or even being near where arc welding is going on can result in a painful condition called “arc eye” or photokeratitis, which is akin to a severe sunburn of the cornea and conjunctiva of the eye.Wolf Robotics
Wolf Robotics is a company operating in automation technology, utilizing industrial robots and computer numerical control systems. Based in Fort Collins, Colorado, it also has employees in Mexico and Brazil. By 2014, it had installed over 8,400 robotic systems for mining, construction, agriculture, and other industries. These typically incorporate ABB or FANUC robots with Wolf's own robotic positioners.In August 2015, Lincoln Electric acquired Rimrock and Wolf Robotics.