OXY-ACETYLENE CUTTING OXY-ACETYLENE CUTTING AND WELDINGAND WELDING

UNIT 23-24UNIT 23-24

I CANI CAN

I can identify oxyacetylene equipmentI can identify oxyacetylene equipment I can describe the safe startup, settings and I can describe the safe startup, settings and

shutdown of the oxyacetylene equipment.shutdown of the oxyacetylene equipment. I can explain the correct operating I can explain the correct operating

procedure for brazing, heating and cutting. procedure for brazing, heating and cutting.

Oxy/Acetylene Oxy/Acetylene FusionFusion

– Process of joining two metals by fusioning (melting) Process of joining two metals by fusioning (melting) the adjoining surfaces. the adjoining surfaces.

– Move molten puddle back & forth between the metal. Move molten puddle back & forth between the metal. Holds very littleHolds very little

BrazingBrazing– Process of joining two metals by fusioning (melting) Process of joining two metals by fusioning (melting)

with a third metal bronzewith a third metal bronze

– Brazing flame is 800 degree (F) or below.Brazing flame is 800 degree (F) or below.

– Base metal is not brought to molten stage. Base metal is not brought to molten stage.

FUEL

HEAT

THE FIRE TRIANGLETHE FIRE TRIANGLETO PRODUCE FIRE, THREE THINGS MUST BE PRESENT AT THE TO PRODUCE FIRE, THREE THINGS MUST BE PRESENT AT THE

SAME TIMESAME TIMEThe basic process that allows the oxy-acetylene equipment toThe basic process that allows the oxy-acetylene equipment to work. work.

OXYGEN

Oxyfuel Gas Welding & Cutting Oxyfuel Gas Welding & Cutting

Oxyfuel is a group of processes that use heat Oxyfuel is a group of processes that use heat generated as a result of the combustion of a generated as a result of the combustion of a mixture of oxygen and a combustible gas. mixture of oxygen and a combustible gas.

Acetylene is the most commonly used in oxyfuel Acetylene is the most commonly used in oxyfuel processes. Propane is another good source of fuel.processes. Propane is another good source of fuel.

The flexibility and mobility provided by oxy-The flexibility and mobility provided by oxy-acetylene welding allow its use in all acetylene welding allow its use in all metalworking industries.metalworking industries.

Oxyfuel welding is primarily used for Oxyfuel welding is primarily used for maintenance, general fabrication, and repair work. maintenance, general fabrication, and repair work.

Chemicals UsedChemicals Used OxygenOxygen

– Colorless, odorless, tasteless gasColorless, odorless, tasteless gas

– Supports combustions & increase heatSupports combustions & increase heat

– Produce by cooling air to a low temperature and turning it Produce by cooling air to a low temperature and turning it into liquid where the oxygen is separate out.into liquid where the oxygen is separate out.

AcetyleneAcetylene– Colorless, has a very distinctive odorColorless, has a very distinctive odor

– Highly flammableHighly flammable

– Produce by mixing calcium carbide (coke + limestone burnt Produce by mixing calcium carbide (coke + limestone burnt together) and water yields acetylene and calcium hydroxide. together) and water yields acetylene and calcium hydroxide.

ADVANTAGESADVANTAGES The relative cost of the equipment is low.The relative cost of the equipment is low. No electricity is required for this process.No electricity is required for this process. Can be used for welding in all positions because no Can be used for welding in all positions because no

electrical cables are required and the operator has electrical cables are required and the operator has precise control of the process. This process is also precise control of the process. This process is also extremely portable. extremely portable.

Can be used on both thick and thin materials, which Can be used on both thick and thin materials, which makes it a very versatile process. makes it a very versatile process.

Very clean, producing no slag or spatter that must be Very clean, producing no slag or spatter that must be removed from the weld.removed from the weld.

Produces high quality welds when done properly.Produces high quality welds when done properly.

LIMITATIONSLIMITATIONS

The materials that can be welded are limited The materials that can be welded are limited primarily to ferrous materials.primarily to ferrous materials.

Creates a “Hot Zone”, fire hazard, because of the Creates a “Hot Zone”, fire hazard, because of the sparks and flame generated in the welding process.sparks and flame generated in the welding process.

Requires the handling of high pressure gases. The Requires the handling of high pressure gases. The combination of oxygen with a fuel gas creates the combination of oxygen with a fuel gas creates the potential for flashbacks and backfires.potential for flashbacks and backfires.

The process can often be slow when compared to The process can often be slow when compared to other types of welding processes.other types of welding processes.

Welding is limited to oxy-acetylene or oxy-Welding is limited to oxy-acetylene or oxy-MAPP.MAPP.

TIP HEIGHTTIP HEIGHT This slide depicts cuts that have been made when the This slide depicts cuts that have been made when the

cutting tip is too high or too low. cutting tip is too high or too low. If the cutting tip height is too high, the top edge of the If the cutting tip height is too high, the top edge of the

cut is beaded or rounded. The cut face is not smooth cut is beaded or rounded. The cut face is not smooth and often is only slightly beveled because the preheat and often is only slightly beveled because the preheat effectiveness is partially lost because the tip is held too effectiveness is partially lost because the tip is held too high. In this situation, the cutting speed is reduced high. In this situation, the cutting speed is reduced because of the danger of losing the cut.because of the danger of losing the cut.

If the cutting tip height is too low, the cut had grooves If the cutting tip height is too low, the cut had grooves and deep drag lines caused by an unstable cutting action. and deep drag lines caused by an unstable cutting action. In this case, part of the preheat cone burns inside the In this case, part of the preheat cone burns inside the kerf where normal gas expansion deflects the oxygen kerf where normal gas expansion deflects the oxygen cutting stream cutting stream

CUTTINGCUTTINGThe preheat flame performs four functions:The preheat flame performs four functions:

ToTo preheat the base metal to ignition temperature.preheat the base metal to ignition temperature. To maintain a protective shield around the cutting stream.To maintain a protective shield around the cutting stream. To maintain the reaction temperature.To maintain the reaction temperature. To penetrate rust, scale, and other foreign properties on the base To penetrate rust, scale, and other foreign properties on the base

metal.metal.

CUTTINGCUTTING

Before cutting action can start, the steel must be Before cutting action can start, the steel must be preheated to a bright cherry red. preheated to a bright cherry red.

When the red spot appears, depress the cutting When the red spot appears, depress the cutting oxygen lever slowly.oxygen lever slowly.

Move steadily across base metal, keeping the Move steadily across base metal, keeping the luminous inner cones approximately 1/8 inch luminous inner cones approximately 1/8 inch above metal.above metal.

While moving across the base metal, if cutting While moving across the base metal, if cutting stops, release the cutting lever, preheat again and stops, release the cutting lever, preheat again and restart the cut.restart the cut.

Use a smooth straight edge to steady and guide Use a smooth straight edge to steady and guide torch movement, if necessary. torch movement, if necessary.

Type of FlameType of Flame Oxygen flameOxygen flame

– More oxygen is used than acetyleneMore oxygen is used than acetylene– Used on torch cutting or heating. Used on torch cutting or heating. – Flame is noisy Flame is noisy

AcetyleneAcetylene– More acetylene than oxygen. More acetylene than oxygen. – Flame produces a black soot and is worthlessFlame produces a black soot and is worthless

NeutralNeutral– Oxygen & acetylene same pressuresOxygen & acetylene same pressures– Quiet flameQuiet flame– Used on brazing. Used on brazing.

FLAMESFLAMES There are three basic flame types used in oxyfuel processesThere are three basic flame types used in oxyfuel processes. . The neutral flame is used in most welding, brazing, soldering and The neutral flame is used in most welding, brazing, soldering and

cutting because it does not carburize or burn the metal. A neutral cutting because it does not carburize or burn the metal. A neutral flame has a bright blue outer envelope with a sharp inner cone visible. flame has a bright blue outer envelope with a sharp inner cone visible. It is called a neutral flame because there is an approximate one-to-one It is called a neutral flame because there is an approximate one-to-one mixture of acetylene and oxygen. This results in a flame that is mixture of acetylene and oxygen. This results in a flame that is chemically neutral. The brilliant white cone should be approximately chemically neutral. The brilliant white cone should be approximately 1/16” to ¾” long, depending on the welding tip size. 1/16” to ¾” long, depending on the welding tip size.

Any variation from the one-to-one oxygen-acetylene mixture will alter Any variation from the one-to-one oxygen-acetylene mixture will alter the flame characteristics. When excess oxygen is forced into the the flame characteristics. When excess oxygen is forced into the oxyacetylene mixture, the resulting flame is said to be oxidizing The oxyacetylene mixture, the resulting flame is said to be oxidizing The oxidizing flame has excess oxygen beyond the neutral flame. It is pale oxidizing flame has excess oxygen beyond the neutral flame. It is pale blue in color without the clearly defined inner cone and characterized blue in color without the clearly defined inner cone and characterized by a hissing sound. An oxidizing flame is sometimes used for brazing. by a hissing sound. An oxidizing flame is sometimes used for brazing.

The carburizing or reducing flame is caused by excess acetylene and is The carburizing or reducing flame is caused by excess acetylene and is characterized by a feather flame that contracts towards the welding tip characterized by a feather flame that contracts towards the welding tip and inner cone. A carburizing flame can be identified by observing and inner cone. A carburizing flame can be identified by observing the existence of three flame zones instead of the usual two found in the the existence of three flame zones instead of the usual two found in the neutral flame. The end of the brilliant white cone is not as well defined neutral flame. The end of the brilliant white cone is not as well defined and is surrounded by an intermediate white cone, that has a feathery and is surrounded by an intermediate white cone, that has a feathery edge in addition to the bluish outer envelopeedge in addition to the bluish outer envelope . .

EquipmentEquipment Cylinder SizesCylinder Sizes

– Oxygen—green color cylinderOxygen—green color cylinder» Sizes—244, 122, or 80 cubic feet.Sizes—244, 122, or 80 cubic feet.

– Acetylene—red color cylinderAcetylene—red color cylinder» Sizes—300, 100 or 60 cubic feetSizes—300, 100 or 60 cubic feet» Contains acetone which absorbs large amounts of acetylene without Contains acetone which absorbs large amounts of acetylene without

changing the nature of the gas.changing the nature of the gas.

Cylinder Pressure (Full pressurize cylinders)Cylinder Pressure (Full pressurize cylinders)– Oxygen—2200 psi at 70 degreeOxygen—2200 psi at 70 degree244 cubic feet244 cubic feet– Acetylene—250 psi at 70 degreeAcetylene—250 psi at 70 degree100 cubic feet.100 cubic feet.

Operating Pressure (Operating Pressure (NEVER ADJUST ACETYLENE ABOVE 15 PSI)NEVER ADJUST ACETYLENE ABOVE 15 PSI)

– Cutting—5 parts oxygen to 1 part acetyleneCutting—5 parts oxygen to 1 part acetylene» Setting—35 oxygen, 7 acetyleneSetting—35 oxygen, 7 acetylene

– Brazing—1 part oxygen to 1 part acetyleneBrazing—1 part oxygen to 1 part acetylene» Setting 3 oxygen, 3 acetyleneSetting 3 oxygen, 3 acetylene

CylindersCylinders

Acetylene Bottle

Oxygen Bottle

Equipment IIEquipment II Cylinder ValveCylinder Valve

– Oxygen & acetylene valves—open all the way.Oxygen & acetylene valves—open all the way.» Allows the gases to flow one way—out.Allows the gases to flow one way—out.

GagesGages– 11stst gage will show the pressure in the cylinders gage will show the pressure in the cylinders

» Oxygen 0 to 4000 psi; Acetylene 0 to 400 psiOxygen 0 to 4000 psi; Acetylene 0 to 400 psi

– 22ndnd gage will show the working line pressure. gage will show the working line pressure.» Oxygen 0 to 100 psi; Acetylene 0 to 30 (Never go above 15 psi)Oxygen 0 to 100 psi; Acetylene 0 to 30 (Never go above 15 psi)

RegulatorsRegulators– Used to adjust the line pressure.Used to adjust the line pressure.– Double stage regulators. Double stage regulators. – Turn regulator knob clockwise to increase pressure. Turn regulator knob clockwise to increase pressure.

NOZZLES

RegulatorsRegulators

Equipment IIIEquipment III NutsNuts

– Acetylene nuts are grooved—counter threads.Acetylene nuts are grooved—counter threads.» Turn counter clockwise to tightenTurn counter clockwise to tighten

Torch bodyTorch body– Two passages for the gases to travel. Two passages for the gases to travel.

HosesHoses– Acetylene—red; Oxygen—greenAcetylene—red; Oxygen—green

Brazing tipsBrazing tips– Numbered 0—15; Larger the number the larger the hole.Numbered 0—15; Larger the number the larger the hole.

Cutting tipsCutting tips– Have 4 preheat orifices (holes)Have 4 preheat orifices (holes)

Oxygen Pre-Heat ValveOxygen Pre-Heat Valve– Adjusts your flame Adjusts your flame

Brazing Head SetupBrazing Head Setup

Torch Head SetupTorch Head Setup

Cutting TipCutting Tip

Safety ConcernsSafety Concerns Lens—Use a number 5 lens.Lens—Use a number 5 lens.

– Used to see the hot metal from the cold metal.Used to see the hot metal from the cold metal. Acetylene AdjustmentAcetylene Adjustment

– Never go above 15 psi working pressure.Never go above 15 psi working pressure. Check for leaks.Check for leaks.

– Use non-organic soap and water. Brush soap and Use non-organic soap and water. Brush soap and water on connection and see if bubbles form. If water on connection and see if bubbles form. If bubbles appear—fix.bubbles appear—fix.

Use long sleeve, long pants, close toe shoes, leather Use long sleeve, long pants, close toe shoes, leather gloves.gloves.

Backfire—tip is too close to metal, causes the flame Backfire—tip is too close to metal, causes the flame to blow out. Caused by overheating, wrong to blow out. Caused by overheating, wrong pressure.pressure.

Flashback—flame goes into torch head, makes a Flashback—flame goes into torch head, makes a shrill hissing noise. Cause—hose leak. Shut off shrill hissing noise. Cause—hose leak. Shut off acetylene, check and fix.acetylene, check and fix.

SUMMARYSUMMARY

Most popular gases for heating, cutting, Most popular gases for heating, cutting, welding metal are acetylene & propane.welding metal are acetylene & propane.

Acetylene is shut off first followed by Acetylene is shut off first followed by oxygen.oxygen.

3-types of flames 3-types of flames – oxidizing flame(excess – oxidizing flame(excess oxygen) hottest flame; carbonizing oxygen) hottest flame; carbonizing flame(excess acetylene) cooler flame; neutral flame(excess acetylene) cooler flame; neutral flame(correct balance of acetylene/oxyflame(correct balance of acetylene/oxy

SUMMARYSUMMARY

Check leaks with soapy water.Check leaks with soapy water. NEVER!!! NEVER NEVER!!! NEVER use oil or oily use oil or oily

substance around oxygen regulators, substance around oxygen regulators, fittings, etc.fittings, etc.

Slag is an insulator rather than steel. Will Slag is an insulator rather than steel. Will not cut.not cut.

Clearance prevents bevel cuts(distance Clearance prevents bevel cuts(distance between tip and base metal.between tip and base metal.

SUMMARYSUMMARY

Oxygen must be 99.5% pure to support the Oxygen must be 99.5% pure to support the combustion of iron.combustion of iron.

Cutting or heating galvanized metal creates Cutting or heating galvanized metal creates a toxic fume.a toxic fume.

Prevent Backfire(tip to close to work, dirty Prevent Backfire(tip to close to work, dirty tip, tip overheating) & flashback(leakage) tip, tip overheating) & flashback(leakage)