- - AGRICULTURE CORE CURRICULUM - - (CLF2000) Advanced Core Cluster: AGRICULTURAL MECHANICS (CLF2250) Unit Title: OXYACETYLENE WELDING ___________________________________________________________________________ (CLF2251) Topic: OXYACETYLENE WELDING Time Year(s) EQUIPMENT & SAFETY 4 hours 1/2/3/4 ___________________________________________________________________________ Topic Objectives: Upon completion of this lesson, the students will be able to: Learning Outcome #: (F-1) - Pass a safety test on oxyacetylene welding. (F-2) - Identify the basic components of the oxyacetylene welder appratus. (F-14) - Change lenses on goggles. Special Material and Equipment: Oxygen and acetylene cylinders, regulators and hoses, torch, tips, open-end wrench, striker, goggles, and protective clothing. References: Cooper, Elmer L. (1987). AGRICULTURAL MECHANICS: FUNDAMENTALS AND APPLICATIONS. Albany, NY: Delmar Publishers. Phipps, Lloyd J., & Reynolds, Carl L. (1990). MECHANICS IN AGRICULTURE (4th ed.). Danville, IL: Interstate Publishers. Resources: Deere & Company. (1987). WELDING (6th ed.) (Fundamentals of Service (FOS) Series). Available from: John Deere Technical Services, Dept. F, John Deere Road, Moline, IL 61265 (Available in Spanish) Evaluation: Quiz by instructor. TOPIC PRESENTATION: OXYACETYLENE WELDING EQUIPMENT AND SAFETY A. Oxyacetylene Equipment Identification 1. Gas Cylinders a. Oxygen Cylinders 1) Oxygen a) Oxygen is a colorless gas (20% of the atmosphere). b) Oxygen has no smell or taste. c) Oxygen is not a flammable or toxic gas. d) Oxygen readily supports combustion. 2) Common size oxygen cylinders hold about 244 cu. ft. of oxygen at 2,000 to 2,600 lbs. per square inch (psi) pressure. 3) Because of their high pressure, they can explode if dropped, struck, heated, or arced with an arc welder. 4) The cylinder valve, which allows the flow of gas from the cylinder to the regulator, is protected when not in use with a threaded cylinder cap. 5) The cylinder cap has two holes on its side designed to cause a cylinder with a broken-off valve to spin instead of take off like a missile from the jet effect of the escaping, high pressure gas. b. Acetylene Cylinders 1) Acetylene a) Acetylene is a colorless gas (a compound of carbon and hydrogen). b) Acetylene has a pungent smell due largely to impurities. c) Acetylene is flammable and highly explosive when mixed with oxygen. d) Acetylene is explosive when compressed above 15 psi, but is very soluble in acetone. e) Acetylene forms explosive compounds with silver and copper, so never use copper pipe or fittings with it. 2) Acetylene cylinders are filled with a porous form of concrete in which all the air is removed by filling the pore spaces with acetone. 3) The acetylene can be stored in these cylinders at pressures above 15 psi without becoming unstable because it combines with the acetone under pressure. 4) Large acetylene cylinders can hold around 275 cu. ft. of acetylene at 250 psi. 5) If acetylene is withdrawn too quickly, removing all the available acetylene, the cylinder pressure gauge will read empty; but after the cylinder is not used for a while, more usable acetylene will come out of the solution. 6) Acetylene cylinders must be kept upright for about eight hours before use and during use in order to prevent acetone loss. 2. Gas Regulators a. Gas regulators reduce the high cylinder pressures to low, hose pressures suitable for welding and cutting applications. b. Identification of the Parts of a Gas Regulator 1) Inlet (cylinder valve connection) a) Oxygen inlets have right-handed threads. b) Acetylene inlets have left-handed threads and their nuts are notched on the outside. 2) Pressure Adjusting Screw a) Decreasing the pressure (out) is counterclockwise. b) Increasing the pressure (in) is clockwise. 3) Cylinder (high) Pressure Gauge a) Oxygen cylinder gauge reads 0-4000 psi. b) Acetylene cylinder gauge reads 0-400 psi. 4) Working (low) Pressure Gauge a) Oxygen working gauge reads 0-200 psi. b) Acetylene working gauge reads 0-30 psi. 5) Outlet (connection for hoses) a) Oxygen outlets have right-handed threads. b) Acetylene outlets have left-handed threads. 3. Check Valves a. Check valves allow the gases to flow in only one direction to prevent backflow. b. Check valves are necessary safety devices attached between the hoses and the regulator outlets. 4. Gas Hoses a. The hoses transport low-pressure gas from the regulator to the torch. b. The oxygen hose is always black or green. c. The acetylene hose is always red. d. The hoses are flame retardant, but should still be kept away from an open flame, sparks, molten metal, and slag. e. New hoses are stored with talcum powder inside, which should be blown out before connecting them to the torch. 5. Torch (Blowpipe) a. The torch controls the mixture of oxygen and acetylene to produce the desired flame. b. Identification of the parts of the torch: 1) Hose connections a) Oxygen connection is usually marked "OXY." b) Acetylene connection is usually marked "FUEL." 1) Oxygen control valve 2) Acetylene control valve 3) Barrel 4) Torch head 6. Torch Tips a. Welding tips b. Cutting tips c. Heating tips d. Tip cleaner 7. Protective Wear a. Goggles b. Leather gloves 8. Striker a. Hand-held piece of equipment used to produce spark. _________________________________________________________ ACTIVITY: 1. Change flint on striker. _________________________________________________________ 9. Working Surfaces a. Welding table (fire brick does not explode under heat) b. Cutting table B. Oxyacetylene Welding Safety 1. Preventing Eye Injury a. Wear goggles with the proper lens when welding, cutting, and grinding. b. Protect others' vision by using a welding shield. c. Make sure no one is standing in front of the cylinder valve before cracking it to prevent eye injury from blowing dust and grit. d. Make sure no one is standing in front of the gas regulators when turning them on to prevent injury from flying glass should they explode. 2. Preventing Burns a. Wear protective gloves, clothing, and boots (lace-up shoes can trap hot sparks, molten metal, and slag). b. Use a spark striker for lighting a torch, not matches or heated metal. c. Cool in water or mark your work "HOT" to keep others from touching it. d. Do not wear ragged clothes or cuffs on pants. e. Keep gloves and protective clothing free of oil and grease. 3. Preventing Respiratory Problems a. Ventilate the work area properly. b. Do not breathe the toxic fumes from welding or cutting galvanized material. 4. Preventing Equipment Damage a. Always use gas regulators to protect the hoses from the high cylinder pressure. b. Use tongs not the leather gloves to pick up hot metal. c. Do not over tighten hose connections and torch tips. d. Never lift cylinders by their valves. e. Never weld or cut on concrete; overheated concrete cracks and explodes. f. Be careful not to break tip cleaners off in the tip being cleaned. g. Keep hoses clear of the torch flame and dropping, molten metal when cutting. 5. Preventing Fire & Gas Explosions a. Never light a torch in an area full of feed or grain dust. b. Keep the area between you and the cylinders clear and the cylinder valves unobstructed. c. Keep oil and grease away from oxygen and oxygen connections. d. Do not try to find a gas leak with a flame; use soapy water from a soap that does not contain oil. e. Do not weld or cut on closed containers, tanks, or vessels. f. Never leave a lighted torch unattended. g. Never use the oxygen tank as a pressure supply to inflate tires or blow off surfaces. h. Always make sure the safety chain is attached and hold onto the oxygen cylinder when moving the cylinder truck. i. When moving or storing individual cylinders, always replace the caps to prevent valve damage. _________________________________________________________ ACTIVITY: 1. Identify all the components of an oxyacetylene welder. 2. Change lenses on welding goggles. 3. Take an oxyacetylene safety test. _________________________________________________________ 7/1/91 OLR/tf/ #%&C