Welding and Cutting Safety It’s your responsibility
Welding safety Arc rays PPEs Machines Ventilation Oxyfuel cutting safety Cylinders Oxygen Fuels Equipment Flame types Grinding safety Pedestal grinders Portable grinders General shop safety Fire extiguishers Burn treatment First aid MSDSs General safety Safety Topics
Arc Rays • Welding arcs are intensely brilliant lights. • They contain a proportion of ultraviolet light which may cause eye damage. For this reason, the arc should never be viewed with the naked eye within a distance of 50.0 ft (15.2 m). • The spectrum of the welding arc is similar to that of the sun. Exposure of the skin and eyes to the arc is the same as exposure to the sun. • Due to the close proximity, the arc is more dangerous than sun exposure. • A burn to the eyes is known as “flash burn”
Personal Clothing Requirements • 100% cotton or wool clothing. • To assess UV protection of materials, simply hold the the material up to a light or window and see how much light gets through. Less light filtering through means greater protection. In addition, darker colors provide more protection than fabrics of the same material in light colors. • Clothing must not be frayed or torn or it can catch fire. • No exposed open pockets. • No synthetic (flammable) materials are to be worn, such as nylon, polyester or rayon. • Safety glasses are required at all times while working. • High top, all leather boots. • DO NOT carry matchers or lighter while welding, cutting or grinding.
A welding hood with the proper filter shade. A welding cap, optional, but recommended. A welding jacket. Apron, optional. Leather welding gloves. Personal Protective Equipment
Recommended Welding Filter Shades • A #10 shade lens is typically the recommended shade for most arc welding.
Reflected Arc Radiation • Reflected UV light can cause the same burs as direct exposure. • Where the work permits, the welder should be enclosed in an individual booth painted with a finish of low reflectivity such as zinc oxide (an important factor for absorbing ultraviolet radiations) and lamp black, or must be enclosed with noncombustible screens similarly painted. Booths and screens must permit circulation of air at floor level. Workers or other persons adjacent to the welding areas must be protected from the rays by noncombustible or flameproof screens or shields or must be required to wear appropriate goggles.
Electric Shock • The hazard of electric shock is one of the the most serious and immediate risks facing a welder. To avoid being shocked • The maximum open circuit voltage for a welder is 80 volts. • Wear dry gloves in good condition for welding. • Do not touch the electrode or metal parts with skin or wet clothing while the machine is turned on. • Keep dry insulation between the body and any grounded metal. • Do not stand in water while welding. • Do not place liquids on or above welders/electrical equipment. • Keep welding cables and electrode holders in good condition. • Remember water conducts electricity. You are mostly water!
Welding Safety • Never weld or flame cut directly on concrete, it could explode from the heat. • Be cautious when picking up metal, it could be hot. • Do not leave hot metal in areas other than those designated or clearly mark the piece “HOT” • Never pass current through a gas cylinder. • Use screens to protect others from the arc light.
Welding Machine Care • Welding machines should be cleaned and maintained on a regular schedule. • Never exceed the rated duty cycle of the machine. • The duty cycle is the % of time the machine can be operated within a ten minute period.
The duty cycle is the percentage of time a welding machine can be used. The “use time” is based on a ten minute time period. Example: a 60% duty cycle means that it can be used for six minutes and needs four minutes of cool down time. If the duty cycle is exceeded, the internal heat will damage the machine. Duty Cycle Chart Example
Ventilation Safety • Consider proper ventilation your most important safety factor. Prior to welding or cutting, make sure you have clean air to breath or wear the proper respirator. • "CAUTION! Welding may produce fumes and gases hazardous to health. Avoid breathing these fumes and gases. Use adequate ventilation. See ANSI Z49.1 – 1967 Safety in Welding and Cutting published by the American Welding Society.“ • If there is smoke on your welding hood after welding, then your head is in the wrong place.
Proper Ventilation Requirements • Mechanical ventilation must be provided when welding or cutting is done in a space of less than 1 0,000 cubic feet (284 m(3)) per welder-, in a room having a ceiling height of less than 16 feet (5 m); or in confined spaces or where the welding space contains partitions, balconies, or other structural barriers to the extent that they significantly obstruct cross ventilation. • Ventilation must be provided be at the minimum rate of 2,000 cubic feet (57 m(3)) per minute per welder, except where appropriate local exhaust hoods and booths a, or airline respirators • Natural ventilation is considered sufficient for welding or cutting operations where the restrictions listed in the preceding paragraphs are not present. • Respiratory protective equipment shall be used when the methods above are not feasible. • Improper Use of Welding Gases. Compressed gases used for welding and cutting shall not be used for ventilation purposes, comfort cooling, blowing dust from clothing, or cleaning the work area.
Ventilation Requirements Minimum air flow/Duct diameter inches • Welding Zone Cubic f/m Duct Dia. inches • 4 to 6 inches from arc to torch: 150 cfm 3 • 6 to 8 inches from arc or torch: 275 cfm 3 ½ • 8 to 10 inches from arc or torch: 425 cfm 4 ½ • 10 to 12 inches from arc or torch: 600 cfm 5 ½
Toxic Materials • Local exhaust ventilation shall be used when potentially hazardous materials are employed as base metals, fluxes, coatings, platings or filler metals. These include, but are not limited to, the following materials: • Beryllium Lead • Cadmium Mercury • Chromium Zinc • Fluorides • Inert-gas metal-arc welding or oxygen cutting of stainless steel • Except for operations involving beryllium, cadmium, lead, or mercury, respiratory protective equipment is not required when natural or mechanical ventilation is sufficient to remove welding fumes from the breathing zone of the workers.
Solvents/Cleaning Agents • Chlorinated Hydrocarbons. Degreasing or other operations involving chlorinated hydrocarbons shall be located or controlled such that vapors from these operations will not enter the atmosphere surrounding any welding or cutting operations to prevent the degradation of such chlorinated hydrocarbon vapors to more highly toxic gases by the action of heat or ultraviolet radiation. • These types of solvents shall be no closer than 200 feet from welding activities.
Oxyfuel Cutting (OFC) The oxyfuel cutting process uses a combination of oxygen and a fuel to provide a high temperature flame.
General Cutting Safety • The light from cutting can be dangerous, a #5 shade filter lens is recommended for most cutting applications. • There is not enough UV light created by the flame to burn your skin. • Sparks, molten metal and the flame can burn you, wear protective clothing.
Oxyfuel Cutting (OFC) • OFC can be a manual process in which the welder must control the the torch movement or a machine can control the movement. • The term oxyfuel gas cutting outfit refers to all the equipment needed to cut. • Cylinders contain oxygen at extremely high pressure and a fuel gas at a low pressure.
Oxygen Cylinders • Oxygen is stored within cylinders of various sizes and pressures ranging from 2000- 2640 PSI. (Pounds Per square inch) • Oxygen cylinders are forged from solid armor plate steel. No part of the cylinder may be less than 1/4” thick. • Cylinders are then tested to over 3,300 PSI using a (NDE) hydrostatic pressure test.
Cylinders are regularly re-tested using hydrostatic (NDE) while in service Cylinders are regularly chemically cleaned and annealed to relieve “jobsite” stresses created by handling . Oxygen Cylinders
Oxygen Cylinder Storage Requirements • Oxygen cylinders shall not be stored near highly combustable material (especially oil or grease); near reserve stocks of carbide, acetylene, or other gas cylinders; near any other substance likely to cause or accelerate fire; or in an acetylene generator compartment. • Oxygen cylinders in storage shall be separated from fuel gas cylinders or combustable materials a minimum of 20 feet or by a noncombustable barrier at least 5 feet high having a fire-resistance rating of at least one-half hour. • Inside buildings, cylinders shall be stored in well protected, well ventilated areas and shall be stored away from elevators, stairs, or gangways. Assigned storage spaces shall be located where cylinders will not be knocked over or damaged by passing or falling objects. • Valve protection caps, where cylinders are designed to accept a cap, shall always be in place, hand-tight, except where cylinders are in use or connected for use.
Cylinder Transportation • Never transport cylinders without the safety caps in place. • Never transport with the regulators in place. • Never allow bottles to stand freely. Always chain them to a secure cart or some other object that cannot be toppled easily. • Never use cylinders as rollers or supports.
Oxygen cylinders incorporate a thin metal “pressure safety disk” made from stainless steel and are designed to rupture prior to the cylinder becoming damaged by pressure. The cylinder valve should be turned on all the way for any high pressure cylinder. Oxygen Cylinders
Reduce high storage cylinder pressure to lower working pressure. Most regulators have a gauge for cylinder pressure and working pressure. Pressure Regulators for Cylinders
Regulators are shut off when the adjusting screw is turn out completely. Regulators maintain a constant torch pressure although cylinder pressure may vary. Regulator diaphragms are made of stainless steel. Pressure Regulators for Cylinders
Hoses are are fabricated from rubber. Oxygen hoses are green in color and have right hand thread. Acetylene hoses are red in color with left hand thread. Left hand threads can be identified by a grove in the body of the nut and it may have “ACET” stamped on it. Regulator Hoses
Check valves allow gas to flow in one direction only. Flashback arrestors are designed to eliminate the possibility of an explosion at the cylinder. Combination Check/ Flashback Valves can be placed at the torch or regulator. Check Valves &Flashback Arrestors
Fuel Gas Types • Acetylene • Gasoline • Hydrogen • Mapp gas • Butane and Propane • Propylene
Acetylene Gas • Virtually all the acetylene distributed for welding and cutting use is created by allowing calcium carbide (a man made product) to react with water. • The nice thing about the calcium carbide method of producing acetylene is that it can be done on almost any scale desired. Placed in tightly-sealed cans, calcium carbide keeps indefinitely. For years, miners’ lamps produced acetylene by adding water, a drop at a time, to lumps of carbide. • Before acetylene in cylinders became available in almost every community of appreciable size produced their own gas from calcium carbide.
Acetylene Cylinders • Acetylene is stored in cylinders specially designed for this purpose only. • Acetylene is extremely unstable in its pure form at pressure above 15 PSI. (Pounds per Square Inch) • Acetone is also present within the cylinder to stabilize the acetylene. • Acetylene cylinders should always be stored in the upright position to prevent the acetone from escaping thus causing the acetylene to become unstable.
Cylinders are filled with a very porous substance “monolithic filler” to help prevent large pockets of pure acetylene from forming. Cylinders have safety (Fuse) plugs in the top and bottom designed to melt at 212° F (100 °C). Acetylene Cylinders
Oxygen and Acetylene Regulator Pressure Settings • Regulator pressure may vary with different torch styles and tip sizes. • PSI (pounds per square inch) is sometimes shown as PSIG (pounds per square inch -gauge) • Common gauge settings for cutting • 1/4” material Oxy 30-35psi Acet 3-9 psi • 1/2” material Oxy 55-85psi Acet 6-12 psi • 1” material Oxy 110-160psi Acet 7-15 psi • Check the torch manufactures data for optimum pressure settings.
Regulator Pressure Settings • The maximum safe working pressure for acetylene is 15 PSI !
Gasoline • Gasoline torches have been found to perform very well, especially where bottled gas fuel is not available or difficult to transport to the worksite. • Tests showed that an oxy-gasoline torch cut steel plate up to 0.5 inch thick as well as oxyacetylene; and 0.5 to 4 inches thick better: 3 times better at 4 inches thick. • The gasoline is fed from a pressure tank whose pressure can be hand-pumped or fed from a gas cylinder.
Hydrogen • Hydrogen has a clean flame and is good for use on aluminum. • It can be used at a higher pressure than acetylene and is therefore useful for underwater welding and cutting. • It is a good type of flame to use when heating large amounts of material.
Mapp Gas • MAPP gas is a registered product of the Dow Chemical Company. • It is liquefied petroleum gas mixed with methylacetylene-propadiene. • It has a heat value a little less than acetylene. • It can be used at much higher pressures than acetylene. • It does not polymerize at high pressures - above 15 psi or so (as acetylene does) and is therefore much less dangerous than acetylene.
Butane and Propane • Butane, like propane, is a saturated hydrocarbon. • Both are mixed together to attain the vapor pressure that is required by the end user and depending on the ambient conditions. • Propane, however, has a very high number of BTUs per cubic foot in its outer cone, and so with the right torch (injector style) can make a faster and cleaner cut than acetylene, and is much more useful for heating and bending than acetylene. • Propane is cheaper than acetylene and easier to transport.
Propylene • Propylene cuts similarly to propane. • When propylene is used, the torch rarely needs tip cleaning. • There is often a substantial advantage to cutting with an injector torch.
Fuel gas cylinder shut off valves should only be opened 1/4 to 1/2 turn This will allow the cylinder to be closed quickly in case of fire. Cylinder valve wrenches should be left in place on cylinders that do not have a hand wheel. Fuel Gas Cylinder Valves
A small welding torch, with throttle valves located at the front end of the handle. Ideally suited to sheet metal welding. Can be fitted for cutting. attachment in place of the welding head shown. Welding torches of this general design are by far the most widely used. They will handle any oxyacetylene welding job, can be fitted with multi-flame (Rosebud) heads for heating applications, and accommodate cutting attachments that will cut steel 6 in. thick. A full-size oxygen cutting torch which has all valves located in its rear body. Another style of cutting torch, with oxygen valves located at the front end of its handle. Typical torch styles
Typical startup procedures • Verify that equipment visually appears safe IE: Hose condition, visibility of gauges. • Clean torch orifices with a “tip cleaners” (a small wire gauge file set used to clean slag and dirt form the torch tip). • Crack (or open) cylinder valves slightly allowing pressure to enter the regulators slowly. • Opening the cylinder valve quickly will “Slam” the regulator and will cause failure.
Typical startup procedures • Never stand directly in the path of a regulator when opening the cylinder. • Check for leaks by setting the regulators to the working pressure and closing the cylinders for a short time. When opening the cylinder valves, watch for the regulators to increase in pressure, if they do, there is a leak in the system. • Using a soapy (non-petroleum based) “Bubble” solution can reveal the leak location.
Typical startup procedures • Always use a flint and steel spark lighter to light the oxygen fuel flame. • Never use a butane lighter or matches to light the flame.
Flame Settings • There are three distinct types of oxy-fuel flames, usually termed: • Neutral • Carburizing (or “excess fuel”) • Oxidizing (or “excess oxygen” ) • The type of flame produced depends upon the ratio of oxygen to acetylene in the gas mixture which leaves the torch tip.
Flame definition • The neutral flame (Fig. 4-1) is produced when the ratio of oxygen to acetylene, in the mixture leaving the torch, is almost exactly one-to-one. It’s termed ”neutral” because it will usually have no chemical effect on the metal being welded. It will not oxidize the weld metal; it will not cause an increase in the carbon content of the weld metal. • The excess acetylene flame (Fig. 4-2), as its name implies, is created when the proportion of acetylene in the mixture is higher than that required to produce the neutral flame. Used on steel, it will cause an increase in the carbon content of the weld metal. • The oxidizing flame (Fig. 4-3) results from burning a mixture which contains more oxygen than required for a neutral flame. It will oxidize or ”burn” some of the metal being welded.
Pedestal or Bench Grinder Safety • Safety glasses with side shields and a face shield must be worn. Hearing protection should be worn. • Remove loose fitting clothing, jewelry, and tie back long hair. • Gloves should not be placed near the grinding stone. • Never grind aluminum with a wheel designed for steel. The wheel will overheat and could explode.