Oxyacetylene torches

Brazed Silver-brazed connectors are commonly used for joining non-ferrous piping in the pressure and temperature range where their use is practical. Use of this type of connector is limited to installations in which the piping temperature will not exceed 425°F and the pressure in cold lines will not exceed 3000 psi. Heating the joint with an oxyacetylene torch melts the alloy. This causes the alloy insert to melt and fill the few thousandths of an inch annular space between the pipe and fitting. 

Brazing Satisfactory brazed joints in molybdenum have been made using oxyacetylene torch and furnace brazing techniques. 

Oxyacetylene torches used for welding reach temperatures near 2000°C. The reaction involved in die combustion of acetylene is... 

Calculate AH and AE at 25°C for the reaction that takes place when an oxyacetylene torch is used. 

Cardiovascular effects have been noted in occupationally exposed workers after exposure to high levels of lead following exposure durations of as short as 4 weeks. Construction workers (race not specified) using oxyacetylene torches to cut a metal bridge that had been painted with lead-based paint were reported to exhibit increases in heart rate and blood pressure after 4 weeks of exposure (Marino et al. 

There are also carbon-carbon triple bonds. Acetylene (or, more rigorously, ethyne—yne indicating the presence of a triple bond in the molecule), C2H2, is a common hydrocarbon that contains a triple bond HC=CH. Note that here too each carbon atom makes four chemical bonds the triple bond counts as three. Acetylene finds significant commercial use in oxyacetylene torches. 

Acetylene, which is produced from coal or natural gas, is burned with oxygen in oxyacetylene torches for welding. This mixture of gases can reach temperatures of 5,072°F (2,800°C), which is hot enough to melt steel. 

In the oxyacetylene torch, how many grams of acetylene and how many liters of O2 at STP are needed to generate 1000 kj of heat ... 

Acetylene (Figure 1.9) is an alkyne, a class of hydrocarbons characterized by carbon-carbon triple bonds consisting of six shared electrons. Highly flammable acetylene is used in large quantities as a chemical raw material and fuel for oxyacetylene torches. It forms dangerously explosive mixtures with air. 

Acetylene (Figure 13.1) is widely used as a chemical raw material and fuel for oxyacetylene torches. It was once the principal raw material for the manufacture of vinyl chloride (see reaction 13.2.4), but other synthetic routes are now used. Acetylene is a colorless gas with an odor resembling garlic. Though not notably toxic, it acts as an asphyxiant and narcotic and has been used for anesthesia. Exposure can cause headache, dizziness, and gastric disturbances. Some adverse effects from exposure to acetylene may be due to the presence of impurities in the commercial product. 

Have you ever seen a construction worker using an oxyacetylene torch (See Figure 14.6.) A brilliant white light comes from the torch as it cuts through steel. The intense heat that is associated with this flame comes from the combustion of ethyne, a very common alkyne. Ethyne is also known as acetylene. 

Norwood, W.D., D.E.Wisehart, C.A.Earl, F.E.Adley, and D.E.Anderson. 1966. Nitrogen dioxide poisoning due to metal-cutting with oxyacetylene torch. J. Occup. Med. 8(6) 301—306. 

Major producers manufacture acetylene by either the partial oxidation of natural gas or as a coproduct of the thermal cracking of ethylene minor producers manufacture acetylene from calcium carbide. About 80% of production is used as a closed system intermediate in the manufacture of acetylene black as well as acetylenic and vinyl derivatives used in a variety of applications such as the manufacture of plastics. The remaining 20% is used primarily in oxyacetylene torches for welding and metal cutting. Although acetylene was used as an anesthetic in the early 1900s, this use has fallen into disfavor due to the explosive properties of acetylene. 

Acetylene lamps are charged with calcium carbide. Very slow addition of water produces acetylene, which is burned as it is produced. Acetylene is also used in the oxyacetylene torch for welding and cutting metals. When acetylene is burned with oxygen, the flame reaches temperatures of about 3000°C. 

Alkynes bum in air with a sooty, yellow flame, like alkanes. Alkenes also bum yellow, while alkanes bum with blue flames. Acetylene bums with large amoimts of heat, and is used in oxyacetylene torches for welding metals together, for example, in the superstmetures of skyscrapers. 

Another type of unsaturated hydrocarbon, called an alkyne, contains a triple bond between two carbon atoms. Alkynes are named using the alkane root name for a given carbon chain length and changing the -ane ending to -yne. Ethyne, known more commonly as acetylene, is the most important commercial alkyne. Most acetylene produced in the United States is used to make vinyl and acrylic materials, although about ten percent is burned in oxyacetylene torches. These torches are used to cut and weld metals. Few alkynes are known to occur naturally because they are very reactive. However, they can be synthesized from other organic compounds. The names and structures of some small alkyne molecules are shown in Table 18.2. 

The high energy of acetylene is released when it is mixed with oxygen and burned in an oxyacetylene torch. The temperature of the flame (about 3000°C) exceeds that of any other hydrocarbon fuel and is higher than the melting point of iron (1535°C). 

The energy necessary to weld metals with an oxyacetylene torch comes from the combustion of acetylene. 

An oxyacetylene torch has a high flame temperature (3000°Cj and is used to weld metals. 

Combustion synthesis of diamond films fi om atmospheric pressure oxyacetylene flame was first reported by Hirose in 1988.This technique, as shown schematically in Fig. 2h, has been demonstrated to be a potentially very important means of growing diamond (Table 1). In Hirose s experiments, linear growth rates of100-200 pmh were achieved. The results were then confirmed by Hanssen et al.l l In Hirose s experiments and most of those that followed, the oxyacetylene torch was typically run with... 

The burning of acetylene (C2H2) in oxygen is the reaction in the oxyacetylene torch. How much oxygen is needed to burn... 

Compute the flame temperature of an oxyacetylene torch using pure acetylene and 50 percent more pure oxygen than is needed to convert all the acetylene to carbon dioxide and water. Both the oxygen and acetylene are initially at room temperature and atmospheric pressure. The following reactions may occur ... 

Acetylene gas (ethyne HC=CH) burns with oxygen in an oxyacetylene torch to produce carbon dioxide, water vapor, and the heat needed to weld metals. The heat of reaction for the combustion of acetylene is 1259 kJ/mol. (a) Calculate the C=C bond energy, and compare your value with that in Table 9.2. (b) When 500.0 g of acetylene burns, how many kilojoules of heat are given off (c) How many grams of CO2 are produced ... 

Acetylene (HC CH), the common name for the smallest alkyne, may be a familiar word because of the oxyacetylene torch used in welding. Acetylene is supplied to the torch from one high-pressure gas tank, and oxygen is supplied from another. Burning acetylene produces a high-temperature flame capable of melting and vaporizing iron and steel. 

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