- Slides: 77
Arc Welding Basic Safety
Warnings • Welding can be safe when proper measures are taken to protect yourself and others from potential hazards. • Understand follow all warning labels found on equipment and with all consumables.
Potential Hazards • Protect yourself and others from potential hazards including: – Fumes and Gases – Electric Shock – Arc Rays – Fire and Explosion Hazards – Noise – Hot objects – Welding Sparks
Fumes and Gases • Welding fumes can be harmful to the welder causing implications such as: o. Irritation of the respiratory tract o. Metal fume fever o. Slightly increase the risk of lung cancer • Use enough ventilation, exhaust at the arc, or both, to keep fumes and gases from your breathing zone and the general area • Use a respirator if needed or required by the process. • The ventilation system must be on while welding at all times.
Electrical Shock • Electric shock can kill • Do not touch live electrical parts Primary Voltage – 208 240, 416 - 480 volt input power Secondary Voltage – 6 to 100 volts for welding • Insulate yourself from work and ground • Follow all warnings on welding equipment • Wear insulated clothing • Always shut off machinery when done and roll the cords up neatly • Do not make repairs yourself, alert your instructor immediately!
U. V. Rays • Welding will produce ultraviolet rays that are harmful to the human eye and skin. Proper protection is needed to avoid bodily harm. • Arc rays are ten times brighter than the sun and can injure eyes and burn skin • Precaution must be taken to protect your eyes and skin from UV radiation. The welding arc is brighter than the sun • Wear correct eye and body protection o 10 shade helmet o. Safety Glasses under the helmet o. Gloves o. Arm and Body Protection ØJacket ØShoulder Covers ØCoveralls
Fire Hazards and Material Safety • Welding sparks can cause fires and explosions • Sparks and spatter from the welding arc can spray up to 35 feet from your work • Flammable materials should be removed from the welding area or shielded from sparks and spatter • Always clean painted materials • All welding booths should be cleaned thoroughly • Have a fire extinguisher ready • Inspect area for fires 30 minutes after welding • Watch for sharp metal edges • Cool all welded metal in the water tank.
Ear Protection • Loud noises can damage your hearing • Keep loud noises at a safe level by using proper hearing protection such as: – Ear plugs – Ear muffs
Protective Clothing • Welders must wear protective clothing for o. Protection from sparks, spatter and UV radiation o. Insulation from electric shock • Protective clothing includes … o. Fire-proof clothing without rolled sleeves, cuffs or frays o. Work boots o. Welding gloves, shirts jackets, bibs, and fire-proof pants o. Welding cap, helmet and safety glasses o. Ear protection – ear plugs and muffs o. Most importantly safety glasses are to be worn at all times in the shop
Improper Protective Clothing • List and describe what is wrong in this picture
Basic Electricity and Welding Arc Welding Basic Safety
Arc Welding Circuit and Concept • The electricity flows from the power source, through the electrode and across the arc, through the base material to the work lead and back to the power source. Identify all the above parts for the arc welder, describe the function of each part, and determine each of the parts safety aspects.
Electrical Concepts DC - DC + • Voltage – The electrical potential or pressure that causes current to flow o. Measured in Volts • Current – The movement of charged particles in a specific direction o. Measured in Amps • Polarity o. DC- (Direct Current Electrode Negative) o. DC+ (Direct Current Electrode Positive) o. AC (Alternating Current) • ALWAYS REMEMBER THAT VOLTAGE WILL HURT BUT AMPERAGE CAN BE FATAL AC
Electrical Lead Condition • Before starting an operation, always check the condition of all electrical leads. • Cracked and worn leads can lead to fatal shock. • All electrode holders or “stingers” should be in tack and not cracked or missing pieces. • All plugs and outlets should be in tack. Never set-up a welder with a broken plug or into a broken outlet. Never operate a welder with splices showing in the leads.
Shielded Metal Arc Welding SMAW
SMAW Key Parts • Electrode Holder: Also known as the “stinger” Handle-like tool that holds the electrode while welding. – Never hold this part with your bare hand while welding. • Ground Connection: Also known as the “workpiece connection clamp” that connects to the work to complete the electrical circuit • Power Source: Where the welder plugs into • Amperage Scale: Determines the amount of “heat” or power the welder will operate at. • Polarity Switch: Setting that determines how the electrons will flow during the welding process. • On / Off Switch: Turns the welder on / off. Make sure the switch function properly at all times.
SMAW Principles • The American Welding Society defines SMAW as Shielded Metal Arc Welding • SMAW: – Is commonly known as ‘Stick’ welding or manual arc welding – Is the most widely used arc welding process in the world – Can be used to weld most common metals and alloys
SMAW Welding Circuit • Current flows through the electrode cable, to the electrode holder, through the electrode, and across the arc • On the work side of the arc, the current flows through the base material to the work clamp and back to the welding machine
SMAW Process Identify all the above segments for the SMAW process, describe the function of each segment, and determine if any safety aspects exist.
The Electrode What is it? • Is a consumable - it gets melted during the welding process • Is composed of two parts – Core Rod (Metal Filler) § Carries welding current § Becomes part of the weld – Flux Coating § Produces a shielding gas § Can provide additional filler § Forms a slag
Electrode Classification • Electrodes are classified by a numbering system • E 6013 o. E = Electrode o 60 or first two numbers = Tensile strength (thousands of pounds o 1 or third number = Welding position o 3 or fourth number = Welding current type and depth of weld penetration. Pictured above are E-7018 electrodes. Identify what the tensile strength is for this electrode.
Electrode Classification Third Digit • Third Digit E_ _ 1 _ = Usable in all directions E_ _ 2 _ = Usable in flat and horizontal positions only E_ _ 4 _ = Usable for vertical down only Pictured above are E-6011 electrodes. Identify what each digit resembles up to the third digit.
Electrode Classification Fourth Digit • Fourth Digit E_ _ _ 0 = DC reverse polarity only E_ _ _ 1 = AC and DC reverse polarity E_ _ _ 2 = AC and DC straight polarity E_ _ _ 3 = AC and DC E_ _ _ 4 = AC and DC E_ _ _ 5 = DC reverse polarity E_ _ _ 6 = AC and DC reverse polarity E_ _ _ 8 = AC and DC reverse polarity Pictured above are E-6013 electrodes. Identify what each digit resembles.
The Arc • An arc occurs when the electrode comes in contact with the work-piece and completes the circuit … like turning on a light! • The electric arc is established in the space between the end of the electrode and the work • The arc reaches temperatures of 10, 000°F which melts the electrode and base material • Don’t look at the arc without proper eye protection. • Wear proper body protection. The UV rays will cause bodily harm. Arc burning off the electrode
Weld Puddle • As the core rod, flux coating, and work pieces heat up and melt, they form a pool of molten material called a weld puddle • The weld puddle is what a welder watches and manipulates while welding • Don’t touch the hot puddle!!! The metal is hot!!!
Shielding Gas • A shielding gas is formed when the flux coating melts. • This protects the weld puddle from the atmosphere preventing contamination during the molten state • Don’t touch the metal!!! The metal is hot!!! • Shielding gas can cause bodily harm. Be sure proper ventilation is being used. Shielding Gas 4 3 2 The shielding gas protects the molten puddle from the atmosphere while stabilizing the arc
Solidified Weldment • As the molten weld puddle solidifies, it forms a joint or connection between two pieces of base material • When done properly on steel, it results in a weld stronger than the surrounding base metal • Don’t touch the metal!!! The metal is hot!!!
Slag • Slag is a combination of the flux coating and impurities from the base metal that float to the surface of the weld. • Slag quickly solidifies to form a solid coating which slows the cooling rate of the weld • The slag can be chipped away and cleaned with a wire brush when hard • Don’t touch the metal!!! The metal is hot!!! • Slag can be dangerous when being removed. Wear the proper safety protection. This welder chips the slag off of a weld during the repair of railroad tracks
Gas Metal Arc Welding GMAW “Mig”
GMAW Defined • An arc welding process that uses an arc between a continuous filler metal electrode and the weld pool. • The process uses a shielding gas that protects the weld from contamination. • Without using a shielding gas the weld becomes pitted and contains no strength value.
Pitted GMAW Weldment Weld is Pitted from improper flow of shielding gas
GMAW Safety Points • Fumes and Gases can be dangerous – Keep your head out of the fumes – Use enough ventilation, exhaust at the arc, or both, to keep fumes and gases from your breathing zone and the general area – Local exhaust and mechanical ventilation can be used without reducing weld quality • Electric Shock can kill – to receive a shock your body must touch the electrode and work or ground at the same time – Do not touch the electrode or metal parts of the electrode holder with skin or wet clothing – Keep dry insulation between your body and the metal being welded or ground – The coil of wire is ‘electrically hot’ when the trigger is pulled
GMAW Safety Points (Continued) • REMEMBER – Gas Cylinders require SPECIAL safety precautions – Cylinders must be secured in an upright position – Cylinders should be located in an area away from arc welding, cutting, heat, sparks, and flame – Shut off the gas cylinder when finished. – NCWHS uses a 75% carbon dioxide and a 25% argon mix for shielding gas. – Don’t bleed or purge the lines after an operation. This gas will not combust / burn.
GMAW Process • During the GMAW process, a solid metal wire is fed through a welding gun and becomes the filler material • Instead of a flux, a shielding gas is used to protect the molten puddle from the atmosphere which results in a weld without slag
GMAW Process (Continued) • Three things happen when the GMAW gun trigger is pulled: – The wire electrode begins to feed – The circuit becomes electrically ‘hot’ – Shielding gas flows through the gun and out the nozzle • Current flows from the power source through the gun cable, gun, contact tip to the wire and across the arc. • On the other side of the arc, current flows through the base metal to the work cable and back to the power source • Shielding gas flows through the gun and out the nozzle
GMAW Key Parts • Gun Housing: Holds or houses the welding wire liner, gas line, and trigger in one piece • Conductor Tube: The angled part of the gun that the wire and shielding gas flow through during the weld operation • Gas Diffuser: Disperses the shielding gas onto the weldment • Contact Tip: The part where the welding wire runs through. Different sized tips accommodate different sized wire. • Nozzle: The cover for the end of the gun that keeps spatter from sticking to the contact tip and gas diffuser and plugging the gun up.
GMAW Process Welding Tip: Generally, drag on thin sheet metal and push on thicker materials Shielding Gas Solidified Weld Metal Arc Electrode Puddle
GMAW Electrode • A GMAW electrode is: – A metal wire – Fed through the gun by the wire feeder – Measured by its diameter GMAW electrodes are commonly packaged on spools, reels and coils ranging from 1 lb to 1000 lbs
GMAW Arc • An electric arc occurs in the gas filled space between the electrode wire and the work piece Electric arcs can generate temperatures up to 10, 000°F
GMAW Weld Puddle • As the wire electrode and work piece heat up and melt, they form a pool of molten material called a weld puddle • This is what the welder watches and manipulates while welding
Shielding Gas • GMAW welding requires a shielding gas to protect the weld puddle • Shielding gas is usually CO 2, argon, or a mixture of both
Final Weld • The welder “lays a bead” of molten metal that quickly solidifies into a weld • The resulting weld is slag free
Weld Examples • GOAL - Make Good Welds • Eliminate Porosity Eliminate Ropey Convex bead Eliminate Excessive Spatter
OXY ACETYLENE SET-UP
Terms and Definitions • Backfire: A short pop of the torch flame followed by extinguishing of the flame or continued burning of the gases. • Flashback: when the torch flame moves into or beyond the mixing chamber. • Preheating: Heating prior to a welding or cutting operation
Equipment Required • • Oxygen cylinder Acetylene cylinder Pressure regulators Two hoses encased together Welding torch with tips Welding goggles and safety glasses Striker Check valves to prevent flashback
Welding and Heating Tips
Safety Rules for Oxy-Acetylene Workplace • Keep the work area free of grease, oil, and flammable materials • Cool or quench hot metal and extinguish all sparks before leaving. Sparks can travel up to 35 feet. • Don’t leave torches, or hot metal where someone will pick them up • Never carry matches or lighters into any work area
Pressure Gauge Failure
Cracked Acetylene Hose
Improper Storage of Tanks
Oxygen/ Acetylene Cutting Torch Stored on Unsafe Cart
Oxygen/ Acetylene Cutting Torch Stored in Flammable Liquids Cabinet
Regulator Parts Pressure regulators reduce the supply pressure, indicated by the high pressure gauge to suitable working pressure, indicated by the low pressure gauge. By turning the adjusting screw, proper working pressures can be achieved.
Personal Safety • Shirts – keep collar and sleeves buttoned to keep out sparks. Avoid wearing shirts with pockets. • Pants or Coveralls – no cuffs and come over shoe tops • Shoes – leather, cover entire foot • Gloves – Leather, never use to pick up metal • Safety Glasses – worn under helmets and goggles and all times.
Eye Protection • Wear safety glasses at all times • Wear welding goggles or a face shield with a lens no. 4 -6 while using torch equipment – when in doubt start with too dark of a lens and then switch to a lighter one.
Color Codes • Green = Oxygen • Red = Acetylene
Pressure Regulating Valves • Each regulator has two gauges mounted on a single manifold. One indicates cylinder pressure and the other indicates working pressure for the torch. • Each regulator has an adjusting screw or Tscrew, so pressure to the torch can be quickly controlled by turning the screw righty-tighty to increases pressure and left-loosey to decrease pressure.
Regulator Attachment – Acetylene connectors have a V-groove left handed thread – Oxygen connectors have a plain surface right handed thread
PSI Settings • Acetylene = 15 psi. max – Over 15 psi. can be fatal – Our regulators in the NCWHS lab will be set at 10 psi. max. • Oxygen = 40 psi. max – Over 40 psi. will dilute the heat of the flame – Our regulators in the NCWHS lab will be set at 30 psi. max.
Torch Parts • Torch body is the part of the torch that is held like a pencil. It contains two needle valves to control the flow of gas • The welding head contains a mixer, mixing throat, and the welding tip
Types of Flames • Oxidizing – Excess oxygen with no feather, makes hissing sound. Sounds like an angry snake. – Least used for anything • Neutral – Burns equal amounts of oxygen and acetylene and has a clear edged inner cone – Most used
Types of Flames • Carburizing – Excess acetylene with an acetylene feather two to three times the length of the inner cone – While burning it will produce a heavy black smoke flame – Used some in hardsurfacing, adds carbon to metal
Operation Safety • 1. Before you start make sure personal safety is followed. • 2. Make sure you have had instruction • 3. Release adjusting screw on regulators before opening valves • 4. Stand on the opposite side of the regulator when opening a valve • 5. Open cylinder valve slowly, oxygen first all the way open acetylene just a quarter of a turn
Operation Safety (II) • 6. Do not use or compress acetylene at pressures higher than 15 psi. • 7. Set working pressures as desired. – Acetylene: 10 psi for NCWHS lab – Oxygen: 30 psi for NCWHS lab • 8. Light acetylene first 9. Never use oil on regulators or any equipment – If oil mixes or touches the acetylene it will combust • 10. Do not use compressed air as a substitute for oxygen • 11. Keep heat, flames, and sparks away from combustibles. • 12. Keep hoses out of sparks or spatter to prevent leaks
Safety Lighting the Torch • • Check the torch valves to make sure they are closed Open the oxygen tank valve full open Open the acetylene tank valve ¼ turn Turn on the oxygen knob on the torch body – This is located next to the acetylene knob • Turn the acetylene gas on no more than ¼ turn • Strike and light • Mix oxygen into the flame with the mixing knob on the torch body. While mixing you want to create a neutral flame. Press down on the cutting lever also to make sure the flame does not jump. – The mixing knob is located half-way up the torch body next to the cutting lever
Shutting down the unit • Shut down the flame by turning off the acetylene knob on the torch body. • Close the oxygen mixing knob located half-way up the torch body • Shut off the tanks by closing the tank valves • Open the acetylene to purge or bleed the line • When both gauges read zero, close the valve • Open the oxygen valve • When both gauges read zero, close the valve • Release pressure on the regulators by turning adjusting screw left or T-screw (out). DO NOT remove the T-screw • Coil hoses and put tools away