Resistance Welding

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Resistance Welding

  1. 1. RESISTANCE WELDING <ul><li>1910.255, SUBPART Q </li></ul><ul><li>Samuel D. Yates </li></ul><ul><li>Corporate Safety and Environmental </li></ul><ul><li>Meadowcraft, Inc. </li></ul><ul><li>[email_address] </li></ul>
  2. 2. VARIOUS TYPES OF RESISTANCE WELDERS Rocker Arm, Seam, and Spot Welder
  3. 3. MULTIHEAD RESISTANCE WELDER
  4. 4. <ul><li>In General </li></ul><ul><li>INSTALLATION – All equipment is to be </li></ul><ul><li>installed by qualified electrician. </li></ul><ul><li>There must be a safety-type discon- </li></ul><ul><li>necting switch, a circuit breaker or a </li></ul><ul><li>circuit interrupter to open each </li></ul><ul><li>power circuit to the machine conven- </li></ul><ul><li>iently located at or near the machine. </li></ul>
  5. 5. <ul><li>Ignitron tubes used in resistance </li></ul><ul><li>welding equipment must be equipped </li></ul><ul><li>with a thermal protection switch. </li></ul><ul><li>Employees assigned to operate resis- </li></ul><ul><li>tence welding equipment must be </li></ul><ul><li>properly trained and judged competent </li></ul><ul><li>to operate the equipment. </li></ul><ul><li>All controls of automatic or air and </li></ul><ul><li>hydraulic must be arranged or guarded to </li></ul><ul><li>prevent accidental activation by the operator. </li></ul>
  6. 6. <ul><li>NONPORTABLE SPOT AND SEAM </li></ul><ul><li>WELDING MACHINES </li></ul><ul><li>For operator safety, all external weld </li></ul><ul><li>initiating control circuits shall operate </li></ul><ul><li>on low voltage (not over 120 volts). </li></ul>
  7. 7. <ul><li>CAPACITOR WELDING </li></ul><ul><li>Stored energy or capacitor discharge </li></ul><ul><li>resistance welding equipment and con- </li></ul><ul><li>trol panels involving voltages of over </li></ul><ul><li>550 volts must be insulated and pro- </li></ul><ul><li>tected by complete enclosures with </li></ul><ul><li>interlocked doors with contacts wired </li></ul><ul><li>into the control circuit. These interlocks </li></ul><ul><li>must interrupt power and short circuit </li></ul><ul><li>all capacitors when the door or panel is open. </li></ul>
  8. 8. CONTROL CABINET
  9. 9. <ul><li>Capacitor Welding </li></ul><ul><li>A manual switch or other suitable pos- </li></ul><ul><li>itive device, along with other mechani- </li></ul><ul><li>cal interlocks or contacts, must be in- </li></ul><ul><li>stalled as an additional safety measure. </li></ul>
  10. 10. <ul><li>INTERLOCKS </li></ul><ul><li>All doors and access panels of all </li></ul><ul><li>resistance welding machines and con- </li></ul><ul><li>trol panels are to be kept locked and </li></ul><ul><li>interlocked to prevent access to live </li></ul><ul><li>portions of the equipment by un- </li></ul><ul><li>authorized persons. </li></ul>
  11. 11. <ul><li>GUARDING </li></ul><ul><li>All press welding machines must be </li></ul><ul><li>guarded where there is a possibility of </li></ul><ul><li>the operator’s fingers being under the </li></ul><ul><li>point of operation by such devices as: </li></ul><ul><li>Electronic eye safety circuits. </li></ul><ul><li>Two hand controls similar to punch </li></ul><ul><li>press operations. </li></ul>
  12. 12. <ul><li>GUARDING </li></ul><ul><li>All chains, gears, operating bus </li></ul><ul><li>linkage and belts must be protected </li></ul><ul><li>by adequate guards. </li></ul>
  13. 13. VARIOUS TYPES OF GUARDING
  14. 14. <ul><li>SHIELDS </li></ul><ul><li>Where practical, shields guards of safety </li></ul><ul><li>glass or suitable fire-resistant plastic, </li></ul><ul><li>shall be installed to guard against flying </li></ul><ul><li>sparks. </li></ul><ul><li>Additional shields or curtains shall be </li></ul><ul><li>installed as necessary to protect passing </li></ul><ul><li>persons from flying sparks. </li></ul>
  15. 15. <ul><li>SHIELDS </li></ul><ul><li>All operators and attendants shall use </li></ul><ul><li>transparent face shields or goggles to </li></ul><ul><li>protect their eyes while operating resis- </li></ul><ul><li>tance welders or resistance brazing </li></ul><ul><li>equipment. </li></ul>
  16. 16. FOOT SWITCHES <ul><li>All foot switches shall be guarded to </li></ul><ul><li>prevent accidental operation of the </li></ul><ul><li>machine. </li></ul>
  17. 17. STOP BUTTONS <ul><li>Two or more emergency stop </li></ul><ul><li>buttons shall be provided on all </li></ul><ul><li>special multispot welding machines, </li></ul><ul><li>including 2-post and 4-post weld </li></ul><ul><li>presses. </li></ul>
  18. 18. SAFETY PINS <ul><li>On large machines, four safety pins </li></ul><ul><li>with plugs and receptacles (one in </li></ul><ul><li>each corner) shall be provided so </li></ul><ul><li>that when the safety pins are re- </li></ul><ul><li>moved and inserted into the ram or </li></ul><ul><li>platen, the press becomes inopera- </li></ul><ul><li>tive. </li></ul>
  19. 19. GROUNDING <ul><li>WHEN?: When technically practical. </li></ul><ul><li>WHAT?: The secondary of all </li></ul><ul><li>welding transformers used </li></ul><ul><li>in multispot, projection, </li></ul><ul><li>and seam welding. </li></ul><ul><li>HOW?: By permanently grounding </li></ul><ul><li>one side of the welding </li></ul><ul><li>secondary current circuit. </li></ul>
  20. 20. GROUNDING <ul><li>When not technically practical: </li></ul><ul><li>Use a center tapped grounding </li></ul><ul><li>reactor connected across the sec- </li></ul><ul><li>ondary or use a safety disconnect </li></ul><ul><li>switch in conjunction with the </li></ul><ul><li>welding controls. The safety discon- </li></ul><ul><li>nect shall be arranged to open both </li></ul><ul><li>sides of the line when welding current </li></ul><ul><li>is not present. </li></ul>
  21. 21. <ul><li>PORTABLE WELDING MACHINES </li></ul><ul><li>Counterbalance: All portable welding </li></ul><ul><li>guns shall have suitable counter- </li></ul><ul><li>balanced devices for supporting the </li></ul><ul><li>guns, including cables, unless the </li></ul><ul><li>design of the gun makes counter- </li></ul><ul><li>balancing impractical or unnecessary. </li></ul>
  22. 22. <ul><li>PORTABLE WELDING MACHINES </li></ul><ul><li>Safety Chains: All portable welding guns, </li></ul><ul><li>transformers and related equipment </li></ul><ul><li>that is suspended from overhead </li></ul><ul><li>structures, eye beams, trolleys, etc. </li></ul><ul><li>shall be equipped with safety chains or </li></ul><ul><li>cables capable of supporting the total </li></ul><ul><li>shock load in the event of failure of any </li></ul><ul><li>component of the supporting system. </li></ul>
  23. 23. <ul><li>PORTABLE WELDING MACHINES </li></ul><ul><li>Clevis: Each clevis shall be capable of </li></ul><ul><li>supporting the total shock load of the </li></ul><ul><li>suspended equipment in the event of </li></ul><ul><li>trolley failure. </li></ul>
  24. 24. <ul><li>PORTABLE WELDING MACHINES </li></ul><ul><li>Switch guards: All initiating switches, </li></ul><ul><li>including retraction and dual schedule </li></ul><ul><li>switches, located on the portable </li></ul><ul><li>welding gun shall be equipped with </li></ul><ul><li>suitable guards capable of preventing </li></ul><ul><li>accidental initiation through contact </li></ul><ul><li>with fixtures, operator’s clothes, etc. </li></ul><ul><li>The initiating switch voltage shall not </li></ul><ul><li>exceed 24 volts. </li></ul>
  25. 25. <ul><li>PORTABLE WELDING MACHINES </li></ul><ul><li>Moving Holder: The movable holder, </li></ul><ul><li>where it enters the gun frame, shall have sufficient clearance to prevent the shearing of fingers carelessly placed on the operating movable holder. </li></ul>
  26. 26. <ul><li>PORTABLE WELDING MACHINES </li></ul><ul><li>Grounding: The secondary and case of </li></ul><ul><li>all portable welding transformers shall be grounded by center tapped secondary or by a center tapped grounding reactor connected across the secondary. </li></ul>
  27. 27. <ul><li>FLASH WELDING EQUIPMENT </li></ul><ul><li>Ventilation and Flash Guard: Flash </li></ul><ul><li>welding machines shall be equipped with a hood to control flying flash. In cases of high production, where materials may contain a film of oil and where toxic elements and metal fumes are given off, ventilation shall be pro-vided in accordance with 1910.252(c). </li></ul>
  28. 28. <ul><li>FLASH WELDING EQUIPMENT </li></ul><ul><li>Fire Curtains: For protection of the operators of nearby equipment, fire-resistant curtains of suitable shields shall be set up around the machine and in such a manner that the operators movements are not hampered. </li></ul>
  29. 29. <ul><li>MAINTENANCE </li></ul><ul><li>PERIODIC INSPECTION SHALL BE MADE </li></ul><ul><li>BY QUALIFIED MAINTENANCE PER- </li></ul><ul><li>SONNEL. </li></ul><ul><li>A CERTIFICATION RECORD MUST BE </li></ul><ul><li>MAINTAINED TO INCLUDE: </li></ul><ul><li>DATE OF INSPECTION </li></ul><ul><li>THE SIGNATURE OF PERSON CONDUCTING THE INSPECTION </li></ul><ul><li>SERIAL NUMBER OR IDENTIFIER OF EQUIPMENT INSPECTED </li></ul>
  30. 30. <ul><li>MAINTENANCE </li></ul><ul><li>OPERATORS SHALL BE INSTRUCTED TO </li></ul><ul><li>REPORT ANY EQUIPMENT DEFECTS TO </li></ul><ul><li>HIS SUPERVISOR AND THE USE OF THE </li></ul><ul><li>EQUIPMENT DISCONTINUED UNTIL </li></ul><ul><li>SAFETY REPAIRS HAVE BEEN COM- </li></ul><ul><li>PLETED. </li></ul>

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