Arc welding & safty


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Arc welding & safty

  1. 1. Arc Welding <ul><li>Patrick V. Bebout </li></ul><ul><li>BCN5737-8384 Advanced Construction Safety </li></ul><ul><li>Spring, 2009 </li></ul>
  2. 2. Definition <ul><li>Arc Welding – A fusion process for joining metals. Through the application of intense heat, the metals at the joint intermix (often with a filler material) to create a metallurgical bond as strong as the original two metals. </li></ul>
  3. 3. Applications and Environment <ul><li>Arc welding is performed whenever an extremely strong metal bond is needed: </li></ul><ul><ul><li>Construction </li></ul></ul><ul><ul><li>Maintenance </li></ul></ul><ul><ul><li>Manufacturing </li></ul></ul><ul><li>Arc welding is performed in all environments: </li></ul><ul><ul><li>Indoors / Outdoors </li></ul></ul><ul><ul><li>Extreme Heights </li></ul></ul><ul><ul><li>Confined Spaces </li></ul></ul><ul><ul><li>Underwater </li></ul></ul>
  4. 4. Arc Welding Components <ul><li>Arc Welding requires five main pieces of equipment: </li></ul><ul><ul><li>Electrode </li></ul></ul><ul><ul><li>Electrode Holder </li></ul></ul><ul><ul><li>Electrode Cable </li></ul></ul><ul><ul><li>Welding Machine (AC or DC) </li></ul></ul><ul><ul><li>Work Cable </li></ul></ul>
  5. 5. Arc Welding Components <ul><li>The Welding machine </li></ul><ul><ul><li>Supplies the electricity needed to create the welding arc </li></ul></ul><ul><ul><li>Converts 120-240 volt AC electricity to welding voltage, typically 20-30 volts AC (also DC voltages) </li></ul></ul>Lincoln Electric’s AC-225 with Wheel Kit and Gloves
  6. 6. The Arc Welding Process <ul><li>How it works: </li></ul><ul><ul><li>The intense heat needed to melt metals is created by the electric arc (> 6500 ° F) </li></ul></ul><ul><ul><li>The arc forms between the electrode and the work surface </li></ul></ul><ul><ul><li>The welder guides the arc along the joint by moving the electrode </li></ul></ul>
  7. 7. History of Arc Welding <ul><li>The electric arc was discovered by Sir Humphry Davy in 1808 </li></ul><ul><li>N.G. Slavianoff and C.L. Coffin developed metal electrodes in the late 1800’s </li></ul><ul><li>Around 1900, A.P. Strohmenger stabilized the arc with coated metal electrodes </li></ul><ul><li>In 1919, C.J. Holslag invented AC welding </li></ul>Portrait by Henry Howard, 1803 Sir Humphry Davy
  8. 8. History of Arc Welding <ul><li>By WWI, welding began replacing rivets on ships due to time savings </li></ul><ul><li>By the end of the war, Germans, Americans and British were arc welding ships and airplanes </li></ul><ul><li>Other advances to strengthen the welds led to much larger usage by WWII </li></ul>Source:
  9. 9. Dangers of Welding <ul><li>Most fatalities that occur while welding fall into four categories * : </li></ul><ul><ul><li>Falls </li></ul></ul><ul><ul><li>Crushed / Struck-By </li></ul></ul><ul><ul><li>Fire / Explosions </li></ul></ul><ul><ul><li>Electrocution </li></ul></ul><ul><li>“ Welding, cutting and brazing are hazardous activities ... The risk from fatal injuries alone is more than four deaths per 1,000 workers over a working lifetime.” </li></ul><ul><li>OSHA Safety and Health Topics </li></ul><ul><li> </li></ul>* Information extracted from OSHA construction worker fatality data (1990-2007)
  10. 10. Types of Welding Fatalities Source: Information extracted from OSHA construction worker fatality data (1990-2007)
  11. 11. Example Fatality <ul><li>Fall: </li></ul><ul><ul><li>Employee #1 was walking along the edge of a roof to conduct some welding on an airport expansion project </li></ul></ul><ul><ul><li>Decking along the edge became loose </li></ul></ul><ul><ul><li>The employee fell 51 feet to the compacted soil </li></ul></ul><ul><ul><li>He died several hours later of internal bleeding and asphyxia </li></ul></ul>Source: OSHA construction worker fatality data (1990-2007)
  12. 12. Example Fatality <ul><li>Crushing Injury: </li></ul><ul><ul><li>Employee #1 was welding pre-cast panels into place at a water treatment facility </li></ul></ul><ul><ul><li>After welding the first panel, Employee #1 repositioned to complete a corner weld on the second panel </li></ul></ul><ul><ul><li>The first panel fell over and crushed him from the rib cage down </li></ul></ul><ul><ul><li>Employee #1 died </li></ul></ul>Source: OSHA construction worker fatality data (1990-2007)
  13. 13. Example Fatality <ul><li>Explosion: </li></ul><ul><ul><li>3 Workers were making repairs on a crude oil storage tank with an arc welder </li></ul></ul><ul><ul><li>90 gallons of oil had been placed in the tank the previous day </li></ul></ul><ul><ul><li>Vapors from the tank were ignited by the welding arc </li></ul></ul><ul><ul><li>Workers #1 and #2 were killed instantly in the explosion </li></ul></ul><ul><ul><li>Worker #3 died the next day from burns covering 90% of his body </li></ul></ul>Source: OSHA construction worker fatality data (1990-2007)
  14. 14. Example Fatality <ul><li>Electrocution: </li></ul><ul><ul><li>Employee #1 was arc welding on his back, drenched in his own sweat </li></ul></ul><ul><ul><li>His equipment was set at 135 ampere AC position </li></ul></ul><ul><ul><li>Equipment was in excellent condition, with warning labels concerning amperage </li></ul></ul><ul><ul><li>Employee was later found dead </li></ul></ul><ul><ul><li>Medical Examiner confirmed that he died from electrocution </li></ul></ul>Source: OSHA construction worker fatality data (1990-2007)
  15. 15. Other Dangers <ul><li>Eye damage from flash burns or Ultraviolet (UV) Radiation (“Welder’s Eye”) </li></ul><ul><li>Flash burns to the welder or surrounding workers </li></ul><ul><li>Inhalation of dangerous fumes (“Metal Fume Fever”) </li></ul><ul><li>Heat stress </li></ul>
  16. 16. OSHA & Arc Welding <ul><li>OSHA addresses arc welding with Regulations 1926.351 </li></ul><ul><li>Manual Electrode Holders: </li></ul><ul><ul><li>Only use electrode holders specifically designed to safely handle the maximum rated current required </li></ul></ul><ul><ul><li>Make sure all current carrying parts are well insulated </li></ul></ul>
  17. 17. OSHA & Arc Welding <ul><li>Welding Cables and Connectors: </li></ul><ul><ul><li>All welding cables should be well insulated </li></ul></ul><ul><ul><li>Repairs or splices must be at least 10ft from the electrode. Splices made closer must have the same insulating quality as the cable. </li></ul></ul>10’ Min. Repair or splice
  18. 18. OSHA & Arc Welding <ul><ul><li>Use substantial insulating material at splices or connectors </li></ul></ul><ul><ul><li>Cables in need of repair can not be used </li></ul></ul>Splice
  19. 19. OSHA & Arc Welding <ul><li>Ground Returns and Machine Grounding: </li></ul><ul><ul><li>Ground cables must be able to carry the specified maximum current capacity </li></ul></ul><ul><ul><li>Do not use pipes carrying flammable gases, flammable liquids, or electric wires as a ground </li></ul></ul>Ground Wire Flammable Gases / Liquids Electrical Wiring
  20. 20. OSHA & Arc Welding <ul><ul><li>Must maintain electrical contact at all joints </li></ul></ul><ul><ul><li>Joints to be bonded and periodically inspected for electrolysis or fire hazard (when continuously employed as ground return) </li></ul></ul>Joints pipe/conduit used as ground return
  21. 21. OSHA & Arc Welding <ul><ul><li>Frame of welding machine must also be grounded </li></ul></ul><ul><ul><li>Ground must be able to break fuse </li></ul></ul><ul><ul><li>Ground connections must be strong and adequate </li></ul></ul>Must Also be Grounded frame of arc welding/cutting machine ground connections
  22. 22. OSHA & Arc Welding <ul><li>Operating Procedures: </li></ul><ul><ul><li>When left unattended, remove electrodes and place away from conductive materials </li></ul></ul><ul><ul><li>Never place hot electrode holders in water </li></ul></ul>Hot Electrode Holder water
  23. 23. OSHA & Arc Welding <ul><ul><li>Turn off welding machine when left unattended or when moving </li></ul></ul><ul><ul><li>Use shielding screens if possible </li></ul></ul>on off welding machine
  24. 24. Additional Safety Guidelines <ul><li>Avoid crushing injuries and falls: </li></ul><ul><ul><li>Examine the workspace prior to commencing any work to identify possible hazards </li></ul></ul><ul><ul><li>Always properly tie-off when welding from heights </li></ul></ul><ul><ul><li>Wear a life-jacket when working above water </li></ul></ul>FALL HAZARD
  25. 25. Additional Safety Guidelines <ul><li>Minimize Risk of Electrocution: </li></ul><ul><ul><li>Low-level dampness increases the risk of electrocution. Do not weld in a wet or damp environment unless an insulating mat or other non-conductive material is securely in place between all body contact points and any surrounding metal. </li></ul></ul><ul><ul><li>Minimize electrical shock through proper equipment: </li></ul></ul><ul><ul><ul><li>Dry gloves, rubber-soled shoes & dry clothing </li></ul></ul></ul><ul><ul><ul><li>Frequent changing of cotton liners to prevent welding gloves saturated with perspiration </li></ul></ul></ul><ul><ul><ul><li>Standing or sitting on a dry wooden floor, a dry rubber mat or similar insulating material </li></ul></ul></ul>
  26. 26. Additional Safety Guidelines <ul><li>Avoid the risk of explosion: </li></ul><ul><ul><li>Where possible welding should be undertaken outdoors in a well ventilated area </li></ul></ul><ul><ul><li>Open up structures / containers prior to welding </li></ul></ul><ul><ul><li>Ventilation during cleaning should be such that any flammable gases are quickly and safely dispersed </li></ul></ul><ul><ul><li>Sight or smell must not be used to determine if safe working conditions apply </li></ul></ul><ul><ul><li>If the condition of the container is not known, it should be assumed that the container contains an explosive mixture </li></ul></ul>
  27. 27. Personal Protective Equipment Source: National AG Safety Database <ul><li>Wear the appropriate PPE for the job: </li></ul><ul><ul><li>Eye Protection </li></ul></ul><ul><ul><li>Burn Protection </li></ul></ul><ul><ul><li>Inhalation Protection </li></ul></ul>
  28. 28. Conclusions <ul><li>Welding should only be carried out by experienced welders directly supervised by a person who fully understands the hazards involved </li></ul><ul><li>Always properly maintain equipment </li></ul><ul><li>Wear appropriate personal protective equipment </li></ul><ul><li>Perform a hazard identification and risk assessment of any workplace prior to commencement of any work </li></ul>