Welding and Cutting

Safety in Welding and Cutting ANSI Z49.1-1988, American Welding Society, Miami, Fla., 1988. 

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. 

API Publ 2009, Safe Welding and Cutting Practices in Refineries, Gasoline Plants, and Petrochemical Plants, 6th ed., September 1995... 

HS(Gj5 Hot work welding and cutting on plant containing flammable matenals... 

Resistance and arc welding operations, and plasma and laser cutting produce fumes by expulsion or evaporation of the base material, coating, and electrode wear. Larger particles deposit on the surrounding surfaces, while smaller particles move upward with convective flows. Specific contaminants associated with different welding and cutting operations are listed in AWS. ... 

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... 

Ensure feat proper fresh air ventilation is provided in oxy-fuel gas welding and cutting operations. 

The US fire code covers installation and use of gaseous oxygen-fuel gas systems for welding and cutting, for the thermodynamically unstable fuels acetylene, MAPP (methylacetylene-allene-propene-propane mixtures), and the stable hydrocarbons propane or butane. 

Operations such as gas or electric welding and cutting with cutting torches cannot be safely performed on hydrogen gas pipelines, mains, or auxiliary equipment, unless all possibility of leakage of hydrogen into the work area is eliminated. The following procedures are recommended ... 

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... 

Uses. Organic synthesis fuel gas for welding and cutting heat-resistant metals rocket and missile propellant fumigant... 

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. 

While internal improvement efforts such as cost reductions need to be continued, the main challenge of the industry will be to maintain the stable growth in volumes it has exhibited in the past. With the importance of the old welding and cutting customers slowly eroding and many of the traditional applications maturing, the industry must be ready to look for alternative growth options. 

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