Accident Prevention Manual for Business & Industry: Engineering & Technology 13th edition

1. Accident Prevention Manual for Business & Industry: Engineering & Technology 13th edition National Safety Council Compiled by Dr. S.D. Allen Iske, Associate Professor University of Central Missouri

2. CHAPTER 22 WELDING AND CUTTING

3. Health Hazards • Toxic metal fumes, vapors, and gases • Primary pulmonary gases • Nonpulmonary gases • Particulate matter • Pulmonary irritants and toxic inhalants • Cleaning compounds • Chlorinated hydrocarbons • Asbestos

4. Health Hazards (Cont.) • Most significant health hazard in welding: generation of toxic metal fumes, vapors, and gases. • Exposure to various toxic gases and vapors generated during welding may produce one or more of the following: • inflammation of the lungs (chemical pneumonitis) • swelling and accumulation of fluids (pulmonary edema) • loss of elasticity of the lungs (emphysema) • chronic bronchitis • asphyxiation • Gases impair or injure lungs and the pulmonary system of those who inhale these hazardous substances. .

5. Primary Pulmonary Gases • These gases can impair or injure the lungs and pulmonary system of workers who inhale these gases in hazardous amounts. • Ozone • Oxides of nitrogen • Phosgene • Phosphine

6. Non-Pulmonary Gases • These gases do not directly injure the lungs, but can cause damage by displacing oxygen in the bloodstream • Carbon monoxide • Carbon dioxide

7. Particulate MatterBenign Pneumoconisosis • Aluminosis (aluminum) • Anthracosis (carbon particles) • Siderosis (iron oxide) • Stannosis (tinoxide)

8. Pulmonary Irritants and Toxic Inhalants Beryllium Cadmium Chromium Copper Fluoride Lead Magnesium Manganese Mercury Molybdenum Nickel Titanium Vanadium Zinc

9. Safety Hazards • Fire protection • Drums, tanks, and closed containers • Management and workers should know the safety hazards involved in the workplace. • Management and workers should be trained to avoid, reduce, or eliminate safety hazards through safe work practices, PPE, and safety equipment.

10. Fire Protection • Fire protection is very important because portable welding and cutting equipment creates special fire hazards. • Work stations should be designed to provide maximum safety and fire protection • Require “hot work permits”. • Floors and combustible materials • Hazardous locations

11. Drums, Tanks, and Closed Containers • Thoroughly clean closed containers that held flammable liquids or other combustibles prior to welding or cutting these materials. • Preference: standard cleaning procedure • If not standard cleaning; two alternate methods: • containers purged with inert gases • fill with water to approximate area of work and vent open

12. Controlling Hazardous Exposures • Ventilation • Natural, mechanical, air cleaners • Fume avoidance • Avoid breathing fumes or being in path. • Nonionizing radiation • UV and IR affect eyes and skin from continued or repeat exposure. • Noise • Exposure limit • Chipping • Slag-chipping hammers and proper safety glasses and hearing protection

13. Controlling Hazardous Exposures (Cont.) • Certain materials contained in consumables, base metals, coatings, or atmospheres of welding or cutting operations have low OSHA permissible exposure limits (PELs) or have low ACGIH threshold limit values (TLVs). • beryllium, arsenic, antimony, chromium, cadmium, mercury, silver, nickel, lead, copper, cobalt, manganese, selenium, vanadium, barium • In welding, cutting, and associated operations, noise levels can exceed the permissible limits.

14. Controlling Hazardous Exposures (Cont.) • Nonionizing radiation • Electric arcs and gas flames produce UV and IR radiation that has a harmful effect on the eyes and skin after repeated exposures. • The effects may include permanent eye injury if appropriate eye protection is not used. • Bystanders and coworkers are also at risk.

15. Personal Protective Equipment • Recommendations: • baseline physical • chest x-ray • pulmonary function testing • Re-examinations by company policy or facility physician • Workers trained in the type of PPE each job requires and proper use and care of equipment

16. Personal Protective Equipment (Cont.) • Respiratory protection • Regarding PELs and TLVs, if dusts, gases, and fumes cannot be kept below the applicable level, welders should wear respiratory equipment certified for the exposure (NIOSH). • Certified respirators for gases, dusts, fumes or self-contained breathing apparatus for oxygen-deficient environments.

17. Personal Protective Equipment (Cont.) • Eye protection • Goggles, helmets, and shields for operators, welders, and helpers • Conform to ANSI Z87.1-1989 and Z89.1-1986 • Protective clothing • Flame resistant gloves, aprons, leggings, high boots, safety shoes, and safety hats

18. Training in Safe Practices • Management should ensure that all welders and cutters are well trained in safe practices that apply to their work. • Standards for training and qualification of welders by American welding society recommended. • Operators and management should recognize their joint responsibilities for safety. • Management ensures welders and supervisors are trained and establishes/enforces procedures. • Use only approved welding equipment.

19. Oxyfuel Welding and Cutting • Unites metals by heating; the heat source is flame produced by the combustion of a fuel gas or gases. • sometimes includes the use of pressure and a filler metal • Oxygen-cutting process severs or removes metal by chemical reaction of the base metal with oxygen at an elevated temperature. • Temperature is maintained by heat from the combustion of fuel gases or from an electric arc.

20. Oxyfuel Welding and Cutting (Cont.) • Welding and cutting gases • Oxygen supports combustion. • Acetylene—combustion with oxygen produces higher flame temperature than any other gas used commercially. • Compressed gas cylinders • Pressurized cylinders—such as oxygen, hydrogen, acetylene • Handling cylinders • Storing cylinders—secured in upright position in a safe, dry, well-ventilated place reserved for purpose. • Using cylinders • Manifolds • Centralized gas supply to provide continuous fuel at a rate in excess of single cylinder. • Construction and design for particular gas and service for which used. • Obtained and installed under supervision of reliable manufacturer.

21. Oxyfuel Welding and Cutting (Cont.) • Distribution piping • Color-coded and clearly identified by gas • Specific requirements per each gas • Portable outlet headers • Valves and connections used for service outlet purposes • Regulators • Only regulators listed by UL or factory mutual used on cylinders of gas • Provide uniform gas supply at correct pressure • Right- or left-hand thread per gas and specific regulators for each gas

22. Oxyfuel Welding and Cutting (Cont.) • Hoses and hose connections • Oxygen and acetylene hoses are different colors or are identified/distinguished clearly • Red—fuel gas • Green—oxygen • Black—inert gas or air hoses • Torches • Constructed of metal castings, forgings, and tubing • Brass or bronze; may be stainless steel • UL or factory mutual approved • Two types: injector or pressure

23. Resistance Welding • Resistance welding equipment is normally permanently installed so the hazards are usually minimized if the equipment has been installed properly and safe practices have been established. • Hazards: lack of point-of-operation guards, flying hot metallic particles, improper handling of materials, unauthorized adjustments and repairs. • Eye injuries, burns, and electrical shock.

24. Resistance Welding (Cont.) • Resistance welding is metal-joining process from heat by resistance to flow of electric current. • Parameters of resistance welding: • Current magnitude, current time, and tip pressure. Each must be accurately controlled.

25. Resistance Welding (Cont.) • Power supply • Transformer secondary max 30 V and high-amp current (up to 200,000 amp) for welding • Cables • Abuse of the cables associated with resistance welding is severe. • Demand on cables requires frequent replacement. • Cables subject to pulsation, bending, and twisting leading to fatigue and breakdown • Machine installation • Installation conform to NEC (NFPA 70)

26. Arc Welding and Cutting • For arc welding or cutting, two welding leads (electrode lead and work lead) are required from the source of current supply. • One lead connected to work and one lead connected to electrode holder. • The steel structure and connections should be capable of carrying the welding current.

27. Arc Welding and Cutting (Cont.) • Power supply • Voltages • Cables • Electrodes and holders • Protection against electric shock • Gas-tungsten arc welding, plasma arc welding, and cutting

28. Gas-Metal Arc Welding (GMAW) • Defined as an arc-welding process that uses an arc between a continuous filler metal electrode and the weld pool. • Also known as metal inert gas (MIG) process. • Most of the processes uses an externally applied shielding gas or a mixture to protect the weld zone.

29. Flux-Cored Arc Welding • Defined as an arc-welding process that uses an arc between a continuous filler metal electrode and the welding pool. • Process used with shielding gas from a flux contained within the tubular electrode. • Used mostly to weld steels. • When used properly, the flux produces high-quality welds that have a clean, smooth appearance.

30. Other Welding and Cutting Processes • Relatively new heat sources for welding and cutting: friction, ultrasonic, lasers. • Each of these special heat sources requires guarding and safe practices. • Laser (light amplification by stimulated emission of radiation)—special eye precautions