Use in welding and cutting

You are probably most familiar with acetylene as a gaseous fuel used in welding and cutting metals (Figure 22.8). When mixed with pure oxygen in a torch, acetylene burns at temperatures above 2000°C. The heat comes from the reaction... 

The weaker lasers are used in such systems as CD players and recorders and in communications and distance-measuring devices. The more-intense laser beams are used for welding and cutting of metals, cloth, skin, etc. and have even been examined as a means of inducing thermonuclear fusion reactions. 

Use Manufacture of polyethylene, polypropylene, ethylene oxide, ethylene dichloride, ethylene glycols, aluminum alkyls, vinyl chloride, vinyl acetate, ethyl chloride, ethylene chlorohydrin, acetaldehyde, ethyl alcohol, polystyrene, styrene, polyvinyl chloride, SBR, polyester resins, trichloroethylene, etc. as a refrigerant, in welding and cutting of metals, an anesthetic, and in orchard sprays to accelerate fruit ripening. 

Commonly accepted safe practice for use of MAPP Gas is available in ANSI Z49.1, Safety in Welding and Cutting, and AWS C4.2, Operator s Manual for Oxyfuel Gas Cutting, [6] and [7]... 

It should be noted that the use of open-flame torches and welding machines is not a part of normal warehouse operations. This type of work must be left to those that have the skills and training. The use of torches and welding can easily start a fire. Every precaution must be taken to ensure that the work area is free of combustibles, flammables, and any other ignition source. Even when the job has been completed, a fire watch should be in place to ensure the safety of the building and employees. More information on the use of welding and cutting operations can be found in Chapter 20. 

The largest use for calcium carbide is in the production of acetylene for oxyacetylene welding and cutting. Companies producing compressed acetylene gas are located neat user plants to minimize freight costs on the gas cylinders. Some acetylene from carbide continues to compete with acetylene from petrochemical sources on a small scale. In Canada and other countries the production of calcium cyanamide from calcium carbide continues. More recentiy calcium carbide has found increased use as a desulfurizing reagent of blast-furnace metal for the production of steel and low sulfur nodular cast iron. 

Acetylenes contain at least one triple bond. The triple bond is even more reactive than a double bond and, therefore, acetylene is used industrially to make other compounds used in rubber and plastics. Acetylene burns in oxygen to produce a very hot flame used for welding and metal cutting (oxy-acetylene torch). 

HS(G)139 The safe use of compressed gases in welding, flame cutting and allied processes... 

Cyanogen, a colorless gas with an almond-like odor, is used in organic syntheses, as a fumigant, as a fuel gas for welding and cutting heat-resistant metals, and as a rocket and missile propellant with ozone or... 

One problem with the use of acetylene is its stability. Although it is stable at normal pressures and temperatures, if it is subjected to pressures as low as 15pounds per square inch gauge (psig) it can explode. To minimize the stability problem, acetylene transport is minimized. Acetylene contained in pressurized cylinders for welding and cutting is dissolved in acetone. A typical acetylene cylinder contains a porous filler made from a combination of materials such as wood chips, diatomaceous earth, charcoal, asbestos, and Portland cement. Synthetic fillers are also available. Acetone is placed in the cylinder and fills the voids in the porous material. Acetylene can then be pressurized in the cylinders up to approximately 250 pounds per square inch (psi) In a pressurized cylinder, 1 titer of filler can hold a couple of hundred titers of acetylene, which stabilizes it. Acetylene cylinders should not be stored on their sides because this could cause the acetone to distribute unequally and create acetylene pockets. 

Accdg to footnote 11 in Ref 2, p 212, ethylene was manufd in the US by passing ethanol vapor over coke wet with phosphoric acid in towers Uses The source of many ethyl and ethylene compds, such as synthetic ethanol, ethyleneglycol, styrene also in oxyethylene welding and cutting of metals (Refs 4 5)... 

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