Document Xz6V0L33aBZbkJNXmrzrMdxkJ

34--Welding and Cutting Fig 34--10 --Self-standing safety shield provides close-quarter protection, rolls up for storage meter should be installed at each torch con nection Air is used to cool the torch and electric current cables Water is also used for cooling, generally where the welding current is more than 250 amp The water supply line, even if city water is used, should be equipped with a strainer to keep out impurities which might get into the torch and plug the water cool ing passages In the gas-shielded tungsten aic torch (Fig 34--9), gas is conducted to the welding point through orifices in the toich around the elec trode holdei Cooling water goes thiough passages through the torch handle and about the holder In the smaller torches, ceramic cups are used A toich for heavier woik gen erally has a water-cooled gas cup Other Welding and Cutting Processes There are several heat sources for welding and cutting which are presently m the expenmental stage, such as friction, ultiasonics, and 966 lasers During each stage of their develop ment, these heat sources require guarding and the evolution of a set of safe practices For example, the laser (Light Amplification by Stimulated Emission of Radiation) presents the hazard of eye damage from the optically amplified light beam, which because of its intensity, can do damage even at great dis tances All employees should theiefore be given preemployment and periodic followup eye examinations Most companies require that employees work m pairs when using laser equipment To confine the laser beam, suitable shields should be developed and installed Since a reflected laser beam is also hazardous, the woik area should contain no glossy surfaces Power supplies for lasers are high-voltage equipment, which should be operated with the precautions developed for this type of equipment See discussion in Chapter 19, "Personal Pro tective Equipment" and Chapter 37, "In dustrial Hygiene " Common Hazards Light rays Electric arcs and gas flames both produce ultraviolet and infrared rays which have a harmful effect on the eyes and skin upon con tinued or repeated exposure The usual effect of ultraviolet is to "sunburn" the surface of the eye, which is painful and disabling but temporary in most instances However, per manent eve injury may result from looking directly into a veiy powerful arc without eye protection Ultraviolet may also produce the same effects on the skin as a severe sunburn Production of ultraviolet radiation is high in gas-shielded arc welding For example, a shield of argon gas around the arc doubles the intensity of the ultraviolet radiation, and, with the greater cunent densities required (paiticulariy with a consumable electrode), the intensity may be five to thirty times as great as with non-shielded welding such as coveied electrode oi gas-shielded metal arc welding Infrared has only the effect of heating the tissue with which it comes m contact If the heat is not enough to cause an ordinary ther-