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WELDING

WELDING. SAFETY AND PROCEEDURES. OXY-ACETYLENE PROCESSES. Acetylene is an unstable gas produced by immersing calcium carbide in water It is dissolved in acetone and store under pressures of 250 psi Cylinders contain a honey comb structure

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WELDING

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  1. WELDING SAFETY AND PROCEEDURES

  2. OXY-ACETYLENE PROCESSES • Acetylene is an unstable gas produced by immersing calcium carbide in water • It is dissolved in acetone and store under pressures of 250 psi • Cylinders contain a honey comb structure • Cylinders have 2 safety plugs to prevent cylinders from heating up and exploding

  3. 0xy-acetylene • Acetylene regulators and hose connections are left hand thread • Working pressure should never exceed 15 psi • Acetylene becomes extremely unstable at pressures above 15psi

  4. Oxygen Cylinders • Oxygen is stored at 2000 psi • Cylinders have a burst disc, to protect against pressures exceeding normal pressures • Oxygen regulators and hose fittings are right hand thread

  5. Regulators and Gauges • Device used to reduce pressure at which gas is delivered • Working pressure will increase when turned clockwise • Regulators usually have 2 gauges • Cylinder pressure gauge and working pressure gauge

  6. Hoses and Fittings • Hoses are usually color coded • Green identifies the oxygen line • Red identifies the fuel line • Hoses should be routinely inspected and replaced if leaking never try and repair! • Fittings couple hose to regulators and torch • Fittings are machined out of brass and are self lubricating never lubricate fittings

  7. Backfire • Happen when fuel ignites within the torch tip-----produces a popping or squealing noise • Occurs when torch nozzle overheats • Must extinguish torch and clean tip

  8. Flashback • Takes place when the flame travels backward in the torch to the mixing chamber • Caused by low pressure settings and leaking hoses • When a backfire or flashback is suspected close the cylinder valves starting with the fuel valve • Flashback arresters are normally fitted at the torch connections

  9. Torches and Tips • After working pressures are set, open fuel valve and ignite tip, set acetylene burn to a clean burn (no soot) • Open oxygen and set flame to desired flame • When extinguishing the torch close the fuel valve first the oxygen valve

  10. Adjusting the Oxy-acetylene Flame • At point of ignition the flame will be yellow and producing black smoke • Increase acetylene pressure using the torch valve • At the point the smoke disappears the working pressure can be assumed to be correct

  11. Setting a Neutral Flame • Next turn on torch oxygen valve, this will cause the flame to become less luminous and an inner blue cone surrounded by a white plume will form at the tip. • The white colored plume indicates excessive acetylene • As more oxygen is added the white plume disappears and a more define blue cone appears • Ideal setting for most welding operations • Flame temperature approx. 5900F (3260C)

  12. Oxidizing Flame • After setting a neutral flame, the oxygen supply is increased the blue cone becomes smaller and sharper • Oxidizing flame indicates excessive oxygen • For most welding operations an oxidizing flame should be avoided • Flame temperature approx.6300 F (3500C)

  13. Carburizing Flame • Indicated by a white plume surrounding a blue cone • Should also be avoided for most welding operations • Flame temperature is approx. 5300F-5800 degrees F (2927C-3205C)

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