OSHA Welding and Cutting

OSHA Outreach Safety Training General Industry Safety Standards Welding, Cutting, and Brazing Subpart Q 29 CFR 1910.251 – 29 CFR 1910.255 Introduction • Welding is the most common method of joining metals in industry today. • When welded, two pieces of similar metals are fused (melted) together. • Once completed, the welded joint is as strong or stronger than the pieces from which the joint is formed. General Hazards • • • • • • General Hazards of welding include: Impact Harmful Dust Smoke Harmful Fumes Heat and Light Radiation Types of Welding • Gas Welding • Arc Welding • Oxygen and Arc Cutting 29 CFR 1910.251 Definitions • Hot Work: work which may generate heat, flame, or sparks. (Welding, Cutting, Brazing, Grinding. • Approved: means listed or approved by nationally recognized testing laboratory. • Welder: mean any operator of electric or gas welding and cutting equipment. 29 CFR 1910.252 General Requirements • All the moveable fire hazards in the vicinity shall be taken to a safe distance (35 FT). • If all the fire hazards cannot be removed, then guards shall be used to confine the heat, sparks, and slag, and to protect the immovable fire hazards. • Suitable fire extinguishing equipment shall be maintained. Continued • Fire watchers are required, to detect all sparks, to extinguish any fires, sounding the alarms. • A fire watch shall be maintained for at least a half hour after completion of welding or cutting operations to detect and extinguish possible smoldering fires. Continued • Where combustible materials such as paper clippings, wood shavings, or textile fibers are on the floor. The floor shall be swept clean for a radius of 35 feet (10.7 m). Combustible floors shall be wet, or protected by fire-resistant shields. Welding or Cutting Containers • No welding, cutting, or other hot works shall be performed on used drums, barrels, tanks, or other containers until they have been cleaned so thoroughly as to make absolutely certain that there are no flammable materials present. Protection of Personnel • Fire resistant gloves • Fire resistant clothing protect from sparks and hot metal. • Safety Shoes • Protective eye wear with proper filter. (Welding Helmet) Health Protection and Ventilation • Mechanical ventilation is required when welding or cutting is done with materials (fluorine compounds, zinc, lead, cadmium, which are partially hazardous and have specific control requirements. • Mechanical ventilation shall be provided: • In space less than 10000 ft3 (284m3) per welder. • In a room having a ceiling height of less than 16 feet (5m). Continued • Such ventilation shall be at the minimum rate of 2,000 cubic feet (57m3) per minute per welder. • When welding must be performed in a space entirely screened on all sides, (No ventilation restriction – 2 feet above the floor). Movable Hoods • Freely movable hoods intended to be placed by the welder as near as practicable to the work being welded . • 100 linear feet per minute velocity in the direction of the hood. 29 CFR 1910.253 Gas Welding and Cutting • An oxyacetylene welding outfits is basically made up of: cylinders of oxygen and acetylene, regulators, hoses, and a torch. • Oxygen and Acetylene are stored in separate cylinders in a high pressure, which is controlled by the regulators. • Hoses carry the gases from the cylinders to the torch. The green hose carries Oxygen. The red Hose carries Acetylene. • The gases are mixed inside the torch. When burned they produce a very hot flame. The flame is regulated by interchangeable torch tips and by the torch valves. Oxyacetylene Welding Equipment Oxyacetylene Welding Torch General Requirements • Under no condition shall acetylene be generated or utilized at a pressure in excess of 15 psig. • Using acetylene at a pressure in excess of 15 psig is a hazardous practice. Free gaseous acetylene is potentially unstable at pressure above 15 psig and could decompose with explosive violence. Continued • The decomposition characteristics of acetylene gas are avoided by keeping the gas in liquid solution and storing it in cylinders of unique construction. These cylinders contain porous calcium silicate filler (millions of microscopic pores) and a suitable solvent usually acetone. (has the ability to absorb over 400 times its own volume of acetylene at 70º F. Continued • When absorbed in this filler, the acetylene is divided into such small units that, should acetylene decomposition take place in one pore, the heat released is not enough to raise the temperature of the acetylene in the surrounding pores. • Acetylene is usually supplied in cylinders which have the capacity of up to 300 cubic feet of dissolved gas under pressure of 250 psig at 70º F. Cylinders and Containers • Compressed gas cylinders shall be legibly marked, for the purpose of identifying the gas content.(stenciling – stamping) • Cylinders should be stored away from elevators, stairs, or gangways, or other areas where they might be knocked over or damaged by passing or falling objects. Continued • Where the cylinder is designed to accept a cap, shall always be in place, hand-tight, except when cylinders are in use or connected for use. The valve protection cap is designed to take the blow in case of cylinder falls. • Acetylene cylinders shall be stored valve end up. Oxygen Cylinders • Oxygen cylinders in storage shall be separated from fuel-gas cylinders or combustible cylinders a minimum distance of 20 feet (6.1 m). Oxygen Cylinders • Or by a noncombustible barrier at least 5 feet (1.5m) high having a fire resistance rating of at least 1/2 hour. 29 CFR 1910.254 Arc Welding and Cutting • Most of the electric welder are typically AC/DC, 240 volt transformer types using electricity as the energy source. • Arc welding uses the heat from an electric arc to melt and fuse base metals and welding-rod metal into one piece. The heat from the arc melts the flux coating on the rod. Installing the Arc Welder • The frame or case of welder shall be properly grounded. • A safety type disconnecting switch shall be located near the machine. • The welder shall be protected by properly sized fuse or circuit breaker on an independent circuit. Arc Welding Key Points to Remember • Be sure the welder is properly installed and grounded. • Never weld without adequate ventilation. • Take proper precaution to prevent fires. • Protect your entire body with fire retardant clothing, shoes, and gloves. • Wear eye protection all times. • Weld only in firesafe areas. • Never do any welding, cutting, or hot work on used drums barrels, tanks, or other containers. • Mark metal “HOT” with a soapstone. 29 CFR 1910.255 Resistance Welding • All doors and access panels of all resistance welding machines and control panels shall be kept locked and interlocked to prevent access, to live portions of the equipment. • All press welding operations, shall be effectively guarded by use of a device such as an electronic eye safety circuit, two hands controls, …. Continued • The hazard of flying sparks shall be eliminated by installing a shield guard of safety glass or suitable fire-resistant plastic at the point of operation. • Two or more safety emergency stop buttons shall be provided on all special multispot welding machines.