ACETYLENE

Acetylene is a flammable fuel gas composed of carbon and hydrogen having the chemical formula C₂H₂.Whenburned with oxygen, acetylene produces a hot flame, having a temperature between 5700F and 6300F. Acetylene is a colorless gas, having a disagreeable odor that is readily detected even when the gas is highly diluted with air. When a portable welding outfit, similar to the one shown in figure 4-3 is used, acetylene is obtained directly from the cylinder. In the case of stationary equipment, similar to the acetylene cylinder bank shown in figure 4-4, the acetylene can be piped to a number of individual cutting stations.

Hazards

Pure acetylene is self-explosive if stored in the free state under a pressure of 29.4 pounds per square inch (psi). A slight shock is likely to cause it to explode.

WARNING

Acetylene becomes extremely dangerous if used above 15 pounds pressure.

Figure 44.-Stationary acetylene cylinder bank.

Cylinder Design

Acetylene can be safely compressed up to 275 psi when dissolved in acetone and stored in specially designed cylinders filled with porous material, such as balsa wood, charcoal, finely shredded asbestos, corn pith, portland cement, or infusorial earth. These porous filler materials aid in the prevention of high-pressure gas pockets forming in the cylinder.

Acetone is a liquid chemical that dissolves large portions of acetylene under pressure without changing the nature of the gas. Being a liquid, acetone can be drawn from an acetylene cylinder when it is not upright. You should not store acetylene cylinders on their side, but if they are, you must let the cylinder stand upright for a minimum of 2 hours before using. This allows the acetone to settle to the bottom of the cylinder.

NOTE: Acetone contaminates the hoses, regulators, torch, and disrupts the flame.

Acetylene is measured in cubic feet. The most common cylinder sizes are 130-, 290-, and 330-cubic-foot capacity. The standard size cylinder the Navy uses holds

Figure 4-5.-Acetylene cylinder.

225 cubic feet of acetylene. Just because a cylinder has a 225-cubic-foot capacity does not necessarily mean it has 225 cubic feet of acetylene in it. Because it is dissolved in acetone, you cannot judge how much acetylene is left in a cylinder by gauge pressure. The pressure of the acetylene cylinder will remain fairly constant until most of the gas is consumed.

An example of an acetylene cylinder is shown in figure 4-5. These cylinders are equipped with fusible plugs that relieve excess pressure if the cylinder is exposed to undo heat. The standard Navy acetylene cylinder contains 225 cubic feet of acetylene and weighs about 250 pounds. The acetylene cylinder is yellow, and all compressed-gas cylinders are color-coded for identification. More on the color coding of cylinders is covered later in this chapter.

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