PowerPoint to accompany Welding Principles and Practices 4th edition Edward R. Bohnart © 2012 The...

PowerPoint to accompanyPowerPoint to accompany

WeldingWeldingPrinciples and PracticesPrinciples and Practices4th edition4th edition

Edward R. BohnartEdward R. Bohnart

© 2012 The McGraw-Hill Companies, Inc. All rights reserved.

Chapter 31Chapter 31

Welding and Bonding of

Plastics

Welding and Bonding of

Plastics

© 2012 The McGraw-Hill Companies, Inc. All rights reserved.W

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2

ObjectivesObjectives

1.1. Describe uses of plastics.Describe uses of plastics.

2.2. Identify types of plastics.Identify types of plastics.

3.3. Describe plastic welding processes.Describe plastic welding processes.

4.4. Identify common plastic weld faults.Identify common plastic weld faults.

5.5. Make various plastic groove, fillet, and Make various plastic groove, fillet, and edge welds on sheet, plate, and pipe.edge welds on sheet, plate, and pipe.


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PlasticsPlastics

• Synthetic polymers (thermoplastics) been Synthetic polymers (thermoplastics) been used in world economy for over 100 yearsused in world economy for over 100 years

• Welding and fabrication part of manufacturing Welding and fabrication part of manufacturing industry since mid-1930sindustry since mid-1930s– Birth of hot-gas welding techniqueBirth of hot-gas welding technique– No public documentation regarding requirements No public documentation regarding requirements

for use, design criteria, and applicationfor use, design criteria, and application• AWS covers plastics welding in Volume 3 AWS covers plastics welding in Volume 3

of its Welding Handbookof its Welding Handbook– Technical committee, GI, focused on plastic Technical committee, GI, focused on plastic

weldingwelding


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Usefulness of PlasticsUsefulness of Plastics

• Corrosion resistant, lightweight, and Corrosion resistant, lightweight, and fatigue resistant, and when composite fatigue resistant, and when composite structures used, great strength-to-weight structures used, great strength-to-weight ratios achievableratios achievable

• Manufacturing simplifiedManufacturing simplified– Parts made in one stepParts made in one step

• Abundant and recyclableAbundant and recyclable


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Key Points for WeldingKey Points for Welding

• Welding produces very strong joints Welding produces very strong joints • Some plastics can only be joined by welding Some plastics can only be joined by welding • Fusion line usually same as for bulk polymer, Fusion line usually same as for bulk polymer,

so easily recyclableso easily recyclable• Relative insensitivity to surface preparation Relative insensitivity to surface preparation

as pressure used to make weld forces as pressure used to make weld forces surface layers from fusion line surface layers from fusion line

• Process time very fastProcess time very fast


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Thermoplastic PolymersThermoplastic Polymers

• Consist of many strands intertwined but still Consist of many strands intertwined but still capable of moving past each othercapable of moving past each other

• Soften and/or melt when heated and can be Soften and/or melt when heated and can be weldedwelded

• Can put heated polymers in cooled mold of Can put heated polymers in cooled mold of shape required to form useful partsshape required to form useful parts

• Thermosetting plastics usually formed by Thermosetting plastics usually formed by polymerization of polymers in a heated mold of polymerization of polymers in a heated mold of the shape required for a partthe shape required for a part– Joined by mechanical fasteners or adhesivesJoined by mechanical fasteners or adhesives


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7Requirements Before Starting Any Plastic WeldingRequirements Before Starting Any Plastic Welding

1.1. Know applicationKnow application– Factors such as temperature usage, strength, Factors such as temperature usage, strength,

corrosion resistance, and UV resistancecorrosion resistance, and UV resistance

2.2. Know materialKnow material– Critical in selecting filler metal and which joining Critical in selecting filler metal and which joining

process to useprocess to use

3.3. Know welding processKnow welding process– Manually or automaticallyManually or automatically


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Know Your PlasticsKnow Your Plastics

• Color should never be used for Color should never be used for identificationidentification

• Look for identification numberLook for identification number– Can be referenced back through producer of Can be referenced back through producer of

part to determine plastic usedpart to determine plastic used

• Symbol used for identificationSymbol used for identification– Used in recycling of plasticsUsed in recycling of plastics– Look at Table 31-1 for rest ofLook at Table 31-1 for rest of

symbolssymbols


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9Plastics That May Not Have SymbolsPlastics That May Not Have Symbols

• PolyurethanePolyurethane– Flexible, foamy-type plasticFlexible, foamy-type plastic

• PolycarbonatesPolycarbonates– Very tough transparent plasticVery tough transparent plastic

• AcrylicAcrylic– Hard rigid plasticHard rigid plastic– Can be polished, cut and shaped by heating to Can be polished, cut and shaped by heating to

310ºF310ºF

• ABSABS– Good finish, heat and impact resistantGood finish, heat and impact resistant


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• NylonNylon– Very tough plastic with high abrasion Very tough plastic with high abrasion

resistanceresistance– Can be turned and shaped well on latheCan be turned and shaped well on lathe

• PTFEPTFE– Very low friction value and expensiveVery low friction value and expensive

• MFMF– Thermoset (considered unweldable)Thermoset (considered unweldable)– Heatproof and chemical resistant, but brittleHeatproof and chemical resistant, but brittle


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• Urea formaldehydeUrea formaldehyde– Thermoset, heatproof, and chemical resistantThermoset, heatproof, and chemical resistant

• Polyester resinPolyester resin– Thermoset, heatproof, and chemical resistantThermoset, heatproof, and chemical resistant

• Epoxy resinEpoxy resin– Similar to polyester resin but more Similar to polyester resin but more

dimensionally stable and more expensivedimensionally stable and more expensive

• RubberRubber– Very flexible and stretchyVery flexible and stretchy


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Scratching TestScratching Test

• Not very accurate testNot very accurate test• Gives some idea of type of plastic you are Gives some idea of type of plastic you are

working withworking with• Scratch with fingernailScratch with fingernail

– Scratches: One of softer-type plastics: Scratches: One of softer-type plastics: PE, PP, PTFEPE, PP, PTFE

– Does not scratch: Not ABS, PVC, or any other Does not scratch: Not ABS, PVC, or any other of harder plasticsof harder plastics


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Sound TestSound Test

• Have different specific weights and surface Have different specific weights and surface hardnesses that cause them to sound different hardnesses that cause them to sound different from one anotherfrom one another– Take solid piece and drop it on hard and Take solid piece and drop it on hard and

even surface from height of approximately even surface from height of approximately 5–10 in.5–10 in.

• Hear specific tonesHear specific tones• Train ear to different tonesTrain ear to different tones

– Generally reliable enough to determine Generally reliable enough to determine plastic’s familyplastic’s family


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Floating TestFloating Test

• Only help identify plastic's familyOnly help identify plastic's family• All plastics have specific weight higher or All plastics have specific weight higher or

lower than specific weight of waterlower than specific weight of water– Take glass of clean water at room temperatureTake glass of clean water at room temperature– Insert small piece of plastic to determine if it Insert small piece of plastic to determine if it

will float or notwill float or not

• Only two plastics will float: PE and PPOnly two plastics will float: PE and PP


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Burning TestBurning Test

• Every plastic reacts differently when Every plastic reacts differently when burnedburned

• Most accurate testMost accurate test– Have good ventilationHave good ventilation– Remove thin sample and put it on surface Remove thin sample and put it on surface

resistant to heatresistant to heat– Light torch or some other flame source and Light torch or some other flame source and

attempt to ignite sampleattempt to ignite sample– Observe reactionObserve reaction


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16Identification of Plastics by BurningIdentification of Plastics by Burning

• Plastic material observationPlastic material observation• PE: Produces blue/yellow flame, smokes, and smells PE: Produces blue/yellow flame, smokes, and smells

like paraffinlike paraffin• PP: Produces blue/yellow flame, drips, and smells like PP: Produces blue/yellow flame, drips, and smells like

dieseldiesel• ABS: Smells sweet, lacks sooty flame, doesABS: Smells sweet, lacks sooty flame, does

not extinguishnot extinguish• Polyamide: Smells like burnt horn, stringy, does not Polyamide: Smells like burnt horn, stringy, does not

extinguishextinguish• Polycarbonate: Black sooty smoke, may extinguishPolycarbonate: Black sooty smoke, may extinguish• PVC: Acrid smell, black smoke, does notPVC: Acrid smell, black smoke, does not

extinguishextinguish


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Two Basic Types of PlasticsTwo Basic Types of Plastics

• Thermosetting plasticsThermosetting plastics– Harden under heatHarden under heat– Through chemical reaction formed into Through chemical reaction formed into

permanent shapes that cannot be changed or permanent shapes that cannot be changed or weldedwelded

• ThermoplasticsThermoplastics– Soften when heatedSoften when heated– Solidify when cooled with no chemical changeSolidify when cooled with no chemical change– Can be machines, formed, and weldedCan be machines, formed, and welded


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18Thermoplastics:Polyvinyl Chloride (PVC)Thermoplastics:Polyvinyl Chloride (PVC)

• One of most popular materials of constructionOne of most popular materials of construction• Excellent physical propertiesExcellent physical properties

– Ease of fabricationEase of fabrication– Relatively low costRelatively low cost– Ability to be formed into wide range of productsAbility to be formed into wide range of products

• Wide forming-temperature ranges and self-Wide forming-temperature ranges and self-extinguishing propertiesextinguishing properties

• Primary limitation is recommended working Primary limitation is recommended working temperature range of 140º to 150ºFtemperature range of 140º to 150ºF


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19Thermoplastics: Rigid Polyvinyl Chloride (PVC)Thermoplastics: Rigid Polyvinyl Chloride (PVC)

• Two broad classificationsTwo broad classifications– Type I has normal resistance to impact and Type I has normal resistance to impact and

high resistance to corrosionhigh resistance to corrosion– Type II modified with rubber to increase impact Type II modified with rubber to increase impact

resistanceresistance• Best materials for general corrosion Best materials for general corrosion

protection because of physical properties, protection because of physical properties, chemical resistance, and low costchemical resistance, and low cost

• Can be hot-air welded, cemented, or Can be hot-air welded, cemented, or assembled by mechanical processesassembled by mechanical processes


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20Thermoplastics: Modified High Impact Rigid Polyvinyl ChlorideThermoplastics: Modified High Impact Rigid Polyvinyl Chloride

• Developed for intermediate corrosion Developed for intermediate corrosion serviceservice

• Readily formed in press and vacuum Readily formed in press and vacuum operationsoperations

• Can be worked and welded at same Can be worked and welded at same temperature as regular polyvinyl chloridetemperature as regular polyvinyl chloride

• Oxides but does not burnOxides but does not burn• Can be welded to type I or type II PVCCan be welded to type I or type II PVC• Used in exhaust systemsUsed in exhaust systems


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Thermoplastics: Polyethylene (PE)Thermoplastics: Polyethylene (PE)

• Available in three classes of materialAvailable in three classes of material– Low densityLow density– Medium densityMedium density– High densityHigh density

• All same chemicallyAll same chemically• Main differences in going from low to high Main differences in going from low to high

density in corrosion resistance, working density in corrosion resistance, working temperature, and tensile strengthtemperature, and tensile strength– Increase from low density to high densityIncrease from low density to high density


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22Thermoplastics: Low Density (Branched) PolyethyleneThermoplastics: Low Density (Branched) Polyethylene

• Lighter than metal and floats in waterLighter than metal and floats in water• BurnsBurns• Offers reasonably good corrosion Offers reasonably good corrosion

resistanceresistance• Cannot be joined by cement, can be Cannot be joined by cement, can be

welded using same class of rodwelded using same class of rod• Dry nitrogen recommended as source for Dry nitrogen recommended as source for

hot gas welding unitshot gas welding units


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23Thermoplastics: Medium Density PolyethyleneThermoplastics: Medium Density Polyethylene

• Produced as film, sheet, rod, tubing, and Produced as film, sheet, rod, tubing, and blockblock

• Not cementableNot cementable• Will burnWill burn• Used for both pressure and conduit tubing Used for both pressure and conduit tubing

and pipeand pipe• Impact strength goodImpact strength good• Can be both vacuum and press formedCan be both vacuum and press formed• Hot gas welding done with dry nitrogenHot gas welding done with dry nitrogen


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24Thermoplastics: High Density PolyethyleneThermoplastics: High Density Polyethylene

• Also referred to as low pressure Also referred to as low pressure polyethylenepolyethylene

• Much lighter than metalMuch lighter than metal• CombustibleCombustible• Can be welded, but not cementedCan be welded, but not cemented• Highest working stress factor and best Highest working stress factor and best

corrosion resistance of all three classescorrosion resistance of all three classes• Reasonably high working temperature Reasonably high working temperature

under low load conditionsunder low load conditions


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Thermoplastics: Polypropylene (PP)Thermoplastics: Polypropylene (PP)

• Compared to polyethyleneCompared to polyethylene– Has lower impact strength, but tensile strength Has lower impact strength, but tensile strength

higher and working temperatures superiorhigher and working temperatures superior– Offers more resistance to organic solvents and Offers more resistance to organic solvents and

degreasing agentsdegreasing agents• Can be joined by welding, but not Can be joined by welding, but not

cementedcemented• Welding rod available in 1/8-, 5/31-, and Welding rod available in 1/8-, 5/31-, and

3/16-inch coil and flat stock3/16-inch coil and flat stock• Dry nitrogen recommended for weldingDry nitrogen recommended for welding


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26Thermoplastics: Acrylonitrile Buadiene Styrene (ABS)Thermoplastics: Acrylonitrile Buadiene Styrene (ABS)

• Two classifications of rigid ABS plasticsTwo classifications of rigid ABS plastics– Type I designed for normal temperaturesType I designed for normal temperatures– Type II for use in higher temperaturesType II for use in higher temperatures

• Cementing main joining methodCementing main joining method– Can also be hot gas welded with nitrogenCan also be hot gas welded with nitrogen

• Good corrosion resistanceGood corrosion resistance• Supports combustionSupports combustion• Used in heat-formed structural partsUsed in heat-formed structural parts


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AcrylicsAcrylics

• Transparent and widely used as substitute Transparent and widely used as substitute for glassfor glass

• Preshrunk before shipmentPreshrunk before shipment• Necessary to specify corrosion resistance, Necessary to specify corrosion resistance,

crazing characteristics, and other crazing characteristics, and other specifications desiredspecifications desired

• Can be cemented and weldedCan be cemented and welded


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28Welding as a Method of Joining PlasticsWelding as a Method of Joining Plastics

• Welding of plastic pipe increasing in oil Welding of plastic pipe increasing in oil refineries and chemical plantsrefineries and chemical plants

• Welding seals leaks instantly in new or old Welding seals leaks instantly in new or old installationsinstallations

• Similar to gas welding of metalsSimilar to gas welding of metals– All basic joint designs usedAll basic joint designs used– All welding positions possibleAll welding positions possible


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29Basic Joints That May Be Formed and WeldedBasic Joints That May Be Formed and Welded

Kamweld Products Co.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.


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30Basic Joints That May Be Formed and WeldedBasic Joints That May Be Formed and Welded




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31

Preparation of PlasticsPreparation of Plastics

• LayoutLayout– Done directly on plastic sheet in pencil, Done directly on plastic sheet in pencil,

soapstone, or china markersoapstone, or china marker

• ShrinkageShrinkage– Preshrink for approximately 20 minutes at Preshrink for approximately 20 minutes at

250ºF, depending on gauge of material250ºF, depending on gauge of material– Control cooling so does not buckle and deformControl cooling so does not buckle and deform

• FormingForming– Can be heated with heat gun and formed Can be heated with heat gun and formed

around metal forms to make curved shapesaround metal forms to make curved shapes


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• CuttingCutting– Same hand or power tools used to cut wool or Same hand or power tools used to cut wool or

metalmetal

• SawingSawing– Heat buildup in saw blade due to poor heat Heat buildup in saw blade due to poor heat

conductivity of plasticconductivity of plastic• 8–22 teeth blades with negative rake8–22 teeth blades with negative rake

• Use special bladesUse special blades


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• ShearingShearing– Done at room temperatureDone at room temperature– Used for cutting of light gauge sheetsUsed for cutting of light gauge sheets

• RoutingRouting– Used for rimming edges of sheets or for Used for rimming edges of sheets or for

shaping and recessingshaping and recessing– Feed must be slow and continuous and swarf Feed must be slow and continuous and swarf

must be removed by compressed airmust be removed by compressed air


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• Other working processesOther working processes– Drilling, punching, machining, milling, Drilling, punching, machining, milling,

threading, knurling, riveting, and boltingthreading, knurling, riveting, and bolting

• SafetySafety– Same rules that apply in metalworkingSame rules that apply in metalworking


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Plastic Welding ProcessesPlastic Welding Processes

• Hot-plate weldingHot-plate welding• Infrared weldingInfrared welding• Hot-gas weldingHot-gas welding• Injection weldingInjection welding• Resistive implantResistive implant• High frequency weldingHigh frequency welding• Induction welding Induction welding

• Dielectric weldingDielectric welding• Microwave heatingMicrowave heating• Spin weldingSpin welding• Vibration weldingVibration welding• Ultrasonic weldingUltrasonic welding• Solvent weldingSolvent welding


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36

Ultrasonic WeldingUltrasonic Welding

• High frequency vibration directed through plastic High frequency vibration directed through plastic joinjoin– Vibration causes friction, then heat, often causing solid Vibration causes friction, then heat, often causing solid

fusion in less than a secondfusion in less than a second

• Generally frequencies above 20 kilohertz usedGenerally frequencies above 20 kilohertz used

• Well suited for rigid thermoplastic partsWell suited for rigid thermoplastic parts

• AdvantagesAdvantages– FastFast– CleanClean

• Filler materials not neededFiller materials not needed

• DisadvantagesDisadvantages– Many tool designs requiredMany tool designs required– Design rules not always available nor Design rules not always available nor

easily appliedeasily applied


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37

Other ProcessesOther Processes

• Linear vibration weldingLinear vibration welding– Similar to ultrasonic welding, but frequencies are in Similar to ultrasonic welding, but frequencies are in

hundreds of hertz and amplitudes in fractions of an inchhundreds of hertz and amplitudes in fractions of an inch

• Spin/friction weldingSpin/friction welding– Two parts spun and contact area builds up heat through Two parts spun and contact area builds up heat through

friction and pressurefriction and pressure– Forces fusion between parts and forces out Forces fusion between parts and forces out

discontinuitiesdiscontinuities– Advantages: Produces good weld, air does not enter Advantages: Produces good weld, air does not enter

during welding, inexpensive machines may be usedduring welding, inexpensive machines may be used– Disadvantages: Circular weld joints requiredDisadvantages: Circular weld joints required


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38

Hot-plate WeldingHot-plate Welding

• Plastic brought into contact with heated Plastic brought into contact with heated plate to soften or melt plasticplate to soften or melt plastic

• Parts removed and pressed togetherParts removed and pressed together• AdvantagesAdvantages

– Simple, easy to performSimple, easy to perform

• DisadvantagesDisadvantages– Slow speed, typically butt joints, requires Slow speed, typically butt joints, requires

variety of platensvariety of platens


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39

Injection Welding UnitInjection Welding Unit

• Used in manual modeUsed in manual mode• Injects molten welding rod below surface of Injects molten welding rod below surface of

plastic to create weldplastic to create weld– Injection tip forms weld zone of molten welding Injection tip forms weld zone of molten welding

rodrod

• Physical mixing of plastic substrate and Physical mixing of plastic substrate and welding rod makes strong, high quality weldwelding rod makes strong, high quality weld

• Automatic feed system lets welder work gunAutomatic feed system lets welder work gunwith one handwith one hand


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40

Injection WeldingInjection Welding

Weld being made on inside of a corner jointDrader Manufacturing

Drader Manufacturing



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41

Hot Gas WeldingHot Gas Welding

• One of principle methods of welding One of principle methods of welding plasticsplastics

• Two basic requirementsTwo basic requirements– Heat sourceHeat source– Welding rod that aids in fusion of weld to base Welding rod that aids in fusion of weld to base

materialmaterial

• Joints identical to those in metal welding Joints identical to those in metal welding and same material preparationand same material preparation

• Flux not required in weldingFlux not required in welding


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• Plastics poor heat conductors, so difficult Plastics poor heat conductors, so difficult to heat uniformlyto heat uniformly– Work in temperature ranges narrower than Work in temperature ranges narrower than

those in metal weldingthose in metal welding

• Only lower surface of welding rod fusibleOnly lower surface of welding rod fusible– Must apply pressure on welding rod to force Must apply pressure on welding rod to force

fusible portion into joint and make permanent fusible portion into joint and make permanent bondbond


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43

Plastic Filler RodPlastic Filler Rod

• Both hot-gas and injection welding require filler rodBoth hot-gas and injection welding require filler rod• Rod need to math properties of plastic to be weldedRod need to math properties of plastic to be welded• Available in variety of colors, sizes, types, and Available in variety of colors, sizes, types, and

profilesprofiles• If don’t know base material and/or filler, perform rod If don’t know base material and/or filler, perform rod

fusion testfusion test1.1. Scrape area cleanScrape area clean

2.2. Melt rod and fuse it into base material; cool with waterMelt rod and fuse it into base material; cool with water

3.3. Pull rod away to determine strength at fusion pointPull rod away to determine strength at fusion point

4.4. Repeat with various rods until best match foundRepeat with various rods until best match found


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44


Various types, sizes, and colors of plastic filler rod for

hot gas and injection welding.

Seelye Plastics

Drader Manufacturing

Basic welding procedure for welding plastics. Use of torch and filler rod is similar to gas welding. Joint is outside corner joint, and weld is fillet weld.



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45

Stretching and DistortionStretching and Distortion

• Some stretching of welding rod will always Some stretching of welding rod will always occuroccur– Should not exceed 15%Should not exceed 15%

• Thermoplastic rod becomes soft when Thermoplastic rod becomes soft when heated enough to form weldheated enough to form weld

• In speed welding, stretching caused by too In speed welding, stretching caused by too much pressure on rod or by plastic residue much pressure on rod or by plastic residue on shoe and in preheating tubeon shoe and in preheating tube


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46

Stretching and DistortionStretching and Distortion

• Amount of stretch in completed weld determined Amount of stretch in completed weld determined by measuring length of rod before and after by measuring length of rod before and after weldingwelding

• Stretching in multilayer welds must be held to Stretching in multilayer welds must be held to minimumminimum

– Checks and cracks show up as voids in finished weld and Checks and cracks show up as voids in finished weld and cannot be detected by visual inspectioncannot be detected by visual inspection

• Shrinkage of weld upon cooling greater near Shrinkage of weld upon cooling greater near crown than at rootcrown than at root

• Distortion can be reduced by using speed Distortion can be reduced by using speed welding and triangular welding rodwelding and triangular welding rod


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47

Welding PVCWelding PVC

• Material must be kept clean at all timesMaterial must be kept clean at all times– Wipe with methylethyl-ketone or similar solventWipe with methylethyl-ketone or similar solvent

• Welding edges beveled or offset to provide Welding edges beveled or offset to provide areas for welding rod and permit better areas for welding rod and permit better adhesionadhesion– Cut bevels with jointer, sander, router, or planeCut bevels with jointer, sander, router, or plane

• Allow root gap in most procedures except when Allow root gap in most procedures except when tack weldingtack welding

• Thickness, shape, size, and strength dictates Thickness, shape, size, and strength dictates type of weld to usetype of weld to use


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48Welding Polyethylene and Polypropylene PrecautionsWelding Polyethylene and Polypropylene Precautions

• Base material should be freshly cut or scraped Base material should be freshly cut or scraped and cleanand clean

• Welding rod and material must be of same Welding rod and material must be of same densitydensity

• Subject to stress cracking (use only 1 foot Subject to stress cracking (use only 1 foot of rod for 1 foot of weld)of rod for 1 foot of weld)

• If welded joint will be under stress in service, If welded joint will be under stress in service, weld will be subject to chemical attack that weld will be subject to chemical attack that would not occur under normal circumstances would not occur under normal circumstances (“environmental stress cracking”)(“environmental stress cracking”)

• Rods tend to loop in direction of the weld (do Rods tend to loop in direction of the weld (do not force rod and add undue strain on weld)not force rod and add undue strain on weld)


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49

Plastic Welding EquipmentPlastic Welding Equipment

• Hot-gas torches divided into two basic Hot-gas torches divided into two basic types:types:– Electrically heatedElectrically heated

• Used in manufacturing plantsUsed in manufacturing plants• Compact and easy to handleCompact and easy to handle

– Gas heatedGas heated• Used primarily in field operationsUsed primarily in field operations

• Welding gas (compressed air or nitrogen) Welding gas (compressed air or nitrogen) passes over heat source raising passes over heat source raising temperature to 450º–800ºFtemperature to 450º–800ºF


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50

Simple Outfit for Plastic WeldingSimple Outfit for Plastic Welding

• Double-jacketed and insulated stainless-steel Double-jacketed and insulated stainless-steel heating tube enclosing 110 volt, a.c.-d.c. heating tube enclosing 110 volt, a.c.-d.c. heating elementheating element

• Lightweight nylon handle for ease and comfortLightweight nylon handle for ease and comfort

• Twenty feet of neoprene-insulated, three-wire Twenty feet of neoprene-insulated, three-wire grounded electric cord inside neoprene air hosegrounded electric cord inside neoprene air hose

• Self-relieving air regulator and easy-to-read Self-relieving air regulator and easy-to-read gaugegauge

• Welding tipWelding tip


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51

Miscellaneous ToolsMiscellaneous Tools

• Wire brushWire brush

• Sharp knifeSharp knife

• Rotary sanderRotary sander

• RaspRasp

• Bending springBending spring

• FilesFiles

• SawsSaws

• C-clampsC-clamps

• Heat gunHeat gun


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52High Speed Electric Welding TorchesHigh Speed Electric Welding Torches

Laramy Products Co.



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53

REPLACE WITH:boh73710_31-13.jpg

Internal Construction of TypicalElectric Welding TorchInternal Construction of TypicalElectric Welding Torch



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54

Setting Up the EquipmentSetting Up the Equipment

1.1. Make sure you have proper type of torch Make sure you have proper type of torch for work at hand.for work at hand.

2.2. Select proper heating element.Select proper heating element.3.3. Relieve regulator-adjusting screw to Relieve regulator-adjusting screw to

prevent damage to regulator due to prevent damage to regulator due to sudden excessive air pressure.sudden excessive air pressure.

4.4. Connect welding unit to air or nitrogen Connect welding unit to air or nitrogen supply and adjust regulator for 3 pounds supply and adjust regulator for 3 pounds pressure.pressure.


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55

Setting Up the EquipmentSetting Up the Equipment

5.5. Connect torch with 115-volt electric Connect torch with 115-volt electric outlet.outlet.

6.6. Let torch warm up for 3 or 4 minutes; Let torch warm up for 3 or 4 minutes; make sure compressed air or nitrogen make sure compressed air or nitrogen flowing continuously through barrel of flowing continuously through barrel of the torch.the torch.

7.7. Select proper tip or high speed welding Select proper tip or high speed welding tool for type of work.tool for type of work.

8.8. Select proper air pressure for size of Select proper air pressure for size of heating element (in watts) and for heating element (in watts) and for temperature desired at tip end.temperature desired at tip end.


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56Rules for Welding with Electric Welding TorchesRules for Welding with Electric Welding Torches

• Be sure welding gas supply is cleanBe sure welding gas supply is clean

• Never leave electricity on when welding gas Never leave electricity on when welding gas turned offturned off

• Volume of welding gas passing over heating Volume of welding gas passing over heating element determines welding temperatureelement determines welding temperature– To increase temperature, reduce gas volumeTo increase temperature, reduce gas volume

– To decrease temperature, increase gas volumeTo decrease temperature, increase gas volume

– To determine temperature of heated air, hold To determine temperature of heated air, hold thermometer 1/4 inch from end of welding tipthermometer 1/4 inch from end of welding tip


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57Rules for Welding with Electric Welding TorchesRules for Welding with Electric Welding Torches

• Always ground torch to prevent short Always ground torch to prevent short circuit, electric shock, and damage to circuit, electric shock, and damage to heating elementheating element

• Never touch end of torch barrel or welding Never touch end of torch barrel or welding tip when torch turned ontip when torch turned on

• To obtain maximum life from heating To obtain maximum life from heating element, use recommended welding element, use recommended welding temperaturetemperature

• Read manufacturer’s operating Read manufacturer’s operating instructions before using torch for first timeinstructions before using torch for first time


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58Rules for Welding with Gas Welding TorchesRules for Welding with Gas Welding Torches

• Be sure torch equipped with proper jet for Be sure torch equipped with proper jet for heating gas being usedheating gas being used

• Be sure welding gas supply is cleanBe sure welding gas supply is clean

• When regulating welding temperatures, When regulating welding temperatures, reduce volume of welding gas or increase reduce volume of welding gas or increase pressure of heating gas to raise the pressure of heating gas to raise the temperaturetemperature– To lower temperature, increase volume of To lower temperature, increase volume of

welding gas or reduce pressure of heating gaswelding gas or reduce pressure of heating gas


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59Rules for Welding with Gas Welding TorchesRules for Welding with Gas Welding Torches

• Never touch end of torch barrel or welding Never touch end of torch barrel or welding tip when torch turned ontip when torch turned on

• Always turn welding gas on before lighting Always turn welding gas on before lighting torchtorch

• Never leave torch lighted when welding Never leave torch lighted when welding gas is off (turn off flame before shutting off gas is off (turn off flame before shutting off welding gas)welding gas)

• Always read manufacturer’s instructions Always read manufacturer’s instructions before using torch for first timebefore using torch for first time


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60

Inspection and TestingInspection and Testing

• Strength of plastic weld dependent on Strength of plastic weld dependent on combination of six interrelated factors:combination of six interrelated factors:– Strength of the base materialStrength of the base material

– Temperature and type of welding gasTemperature and type of welding gas

– Pressure on the welding rod during weldingPressure on the welding rod during welding

– Proper weld and joint selectionProper weld and joint selection

– Proper material preparation before weldingProper material preparation before welding

– Skill of the welderSkill of the welder

• Dressing plastic welds decreases strength of Dressing plastic welds decreases strength of completed welds by approximately 25%completed welds by approximately 25%


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61

Good WeldsGood Welds

Kamweld Products Co.Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.


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62

Faulty WeldsFaulty Welds



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63

Basic Bead StructureBasic Bead Structure

Discolored – Too Much Heat

Good Flowlines – Good WeldNo Flowlines – Cold Weld



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64

Reasons for Faulty WeldsReasons for Faulty Welds

• Overheating base material or plastic filler Overheating base material or plastic filler rodrod

• Underheating base material or plastic filler Underheating base material or plastic filler rodrod

• Improper penetration through entire root of Improper penetration through entire root of weldweld

• Porosity caused by air inclusions or dirtPorosity caused by air inclusions or dirt• Stretching filler rodStretching filler rod• Incorrect handling of welding torchIncorrect handling of welding torch


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65

Reasons for Faulty WeldsReasons for Faulty Welds

• Wrong torch or tip work and travel angleWrong torch or tip work and travel angle

• Too slow or too fast travelToo slow or too fast travel

• Lack of or faulty fanning motion of torchLack of or faulty fanning motion of torch

• Heat at torch tip too close or too far away Heat at torch tip too close or too far away from workfrom work

• Heat at torch tip not centered on weld Heat at torch tip not centered on weld beadbead


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66

Good Plastic Weld RequiresGood Plastic Weld Requires

• Thorough root penetrationThorough root penetration

• Proper balance between the heat used on Proper balance between the heat used on the weld and the pressure exerted on the weld and the pressure exerted on welding rodwelding rod

• Correct handling of welding torchCorrect handling of welding torch

• Correct preparation of joint to be weldedCorrect preparation of joint to be welded

Table 31-4 presents causes of common plastic welding troubles and how to correct them


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67


Porous Weld Poor Penetration

Scorching Distortion

Laramy Products Co.Laramy Products Co.

Laramy Products Co. Laramy Products Co.



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68


Warping Poor Appearance

Stress Cracking Poor FusionLaramy Products Co.

Laramy Products Co.

Laramy Products Co. Laramy Products Co.



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69

Visual InspectionVisual Inspection

• Permits only partial evaluation of weld Permits only partial evaluation of weld beadbead

• Internal defects as incomplete fusion and Internal defects as incomplete fusion and penetration, air inclusions, and cracks penetration, air inclusions, and cracks cannot be determined by visual inspection cannot be determined by visual inspection

• Visual evidence of a good weld is flowlines Visual evidence of a good weld is flowlines that present, continuous, and uniformthat present, continuous, and uniform

• Will reveal faults such as voids, scorching, Will reveal faults such as voids, scorching, and notchingand notching


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70

Testing of WeldsTesting of Welds

• Welded joints sites of potential weakness Welded joints sites of potential weakness in plastic structurein plastic structure

• Show welded joint fit for intended purposeShow welded joint fit for intended purpose– Achieved by appropriate destructive, Achieved by appropriate destructive,

nondestructive, and chemical testing techniquesnondestructive, and chemical testing techniques

• Organizations such as American Society Organizations such as American Society of Testing Materials and American of Testing Materials and American Welding Society have established Welding Society have established procedures for testing plastics and plastic procedures for testing plastics and plastic weldswelds


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71

Destructive TestingDestructive Testing

• Tensile testTensile test– Used to evaluate butt joint-groove welds on rigid Used to evaluate butt joint-groove welds on rigid

sheetsheet

– Value of 80–100% considered acceptableValue of 80–100% considered acceptable

• Creep rupture testCreep rupture test– Compares long term performance of plastic weldsCompares long term performance of plastic welds

– Test under constant load and elevated temperature Test under constant load and elevated temperature and time to failure measured; carried out in waterand time to failure measured; carried out in water


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• Bending testBending test– While weld still hot, bend it double along axis of weld; While weld still hot, bend it double along axis of weld;

another bend test conducted after 24 hoursanother bend test conducted after 24 hours

• Burst testBurst test– Most effective way of testing pipe butt joint-groove Most effective way of testing pipe butt joint-groove

welds and fillet welds on fabricated fittings and welds and fillet welds on fabricated fittings and couplingscouplings

• Impact testImpact test– Weld subjected to sudden impact by hitting it with Weld subjected to sudden impact by hitting it with

hammerhammer


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• Fracture mechanics testsFracture mechanics tests– More rigorous testingMore rigorous testing– Can be used to quantitatively qualify Can be used to quantitatively qualify

characteristics of plastic weldscharacteristics of plastic welds– Test conducted using either three-point bend Test conducted using either three-point bend

loading or single edge notch bend specimenloading or single edge notch bend specimen– If plastic brittle, use linear elastic fracture If plastic brittle, use linear elastic fracture

mechanics testmechanics test– If plastics show great deal of crack tip plasticity, If plastics show great deal of crack tip plasticity,

may require elastic-plastic fracture mechanics may require elastic-plastic fracture mechanics testtest


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74

Nondestructive TestingNondestructive Testing

• Spark coil testSpark coil test– High frequency, high voltage spark-coil tester High frequency, high voltage spark-coil tester

detects pores and cracks in plastic welddetects pores and cracks in plastic weld– Sparks have voltages up to 55 kilovolts and Sparks have voltages up to 55 kilovolts and

frequencies around 200 kilohertzfrequencies around 200 kilohertz

Electro-Technic Products, Inc.



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75

Nondestructive TestingNondestructive Testing

• RadiographyRadiography– Most efficient method of plastic weld inspectionMost efficient method of plastic weld inspection– Gives complete detailed picture of internal Gives complete detailed picture of internal

characteristics of weld joint and permanent characteristics of weld joint and permanent recordrecord

– High costHigh cost

• Chemical testsChemical tests– Test specimen immersed in acetone for 2 to 4 Test specimen immersed in acetone for 2 to 4

hourshours– Dye penetrant painted or sprayed on weldDye penetrant painted or sprayed on weld


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76Instructions for Completing Practice Jobs with the Hot-gas ProcessInstructions for Completing Practice Jobs with the Hot-gas Process

• Important “musts” concerned with plastic Important “musts” concerned with plastic welding:welding:– Small beads should form along each side of Small beads should form along each side of

weld where rod meets base materialweld where rod meets base material– Rod should hold its basic round shapeRod should hold its basic round shape– Neither rod nor base material should char or Neither rod nor base material should char or

discolordiscolor– Length of rod used should be no more nor less Length of rod used should be no more nor less

than length of the weldthan length of the weld– Do not use oxygen or other flammable gasesDo not use oxygen or other flammable gases


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• Plastics must be clean and dry prior to Plastics must be clean and dry prior to welding and during welding operationwelding and during welding operation– Clean by scraping off first layer of material Clean by scraping off first layer of material

surfacesurface• Best tool scraping bladeBest tool scraping blade

– Pick up moisture and must be driedPick up moisture and must be dried• Plastic filler rod must be same composition Plastic filler rod must be same composition

as type of plastic being weldedas type of plastic being welded– Considerations: Type of plastic, joint design, Considerations: Type of plastic, joint design,

thickness of material, position of welding, and thickness of material, position of welding, and type of equipmenttype of equipment


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• Heat supplied by heated gasHeat supplied by heated gas– Compressed air, nitrogen, or inert gasCompressed air, nitrogen, or inert gas– Gas passes through torch where heated by Gas passes through torch where heated by

heating element and then directed through heating element and then directed through torch tip to surface of jointtorch tip to surface of joint

• Filler rod can be fed by hand or Filler rod can be fed by hand or automatically with use of high speed automatically with use of high speed welding tipwelding tip– Tip increases speed of weldingTip increases speed of welding

• Temperature of welding gas regulated by Temperature of welding gas regulated by increasing or decreasing volume of gas to increasing or decreasing volume of gas to torchtorch


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79

Using High Speed Welding TipUsing High Speed Welding Tip

Seelye Plastics



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80

Procedure for Tack WeldingProcedure for Tack Welding

1.1. Attach tack welding tip to torch.Attach tack welding tip to torch.2.2. Wait for 1 or 2 minutes so tip can reach Wait for 1 or 2 minutes so tip can reach

proper temperature.proper temperature.3.3. Hold tip at work and travel angle of Hold tip at work and travel angle of

approximately 90approximately 90ºº and place directly on and place directly on joint to be tacked.joint to be tacked.

4.4. Draw tacker tip along the joint for the Draw tacker tip along the joint for the desired length (about 1/2 to 1 inch long).desired length (about 1/2 to 1 inch long).

5.5. Unit now ready for continuous welding.Unit now ready for continuous welding.6.6. Practice.Practice.


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81

Tack WeldingTack Welding

Kamaeld Products Co.



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82

Hand Welding (Beading)Hand Welding (Beading)

• Purpose to joint two or more pieces Purpose to joint two or more pieces permanently together with rod or strip as permanently together with rod or strip as fillerfiller

• Welder applies pressure on filler rod with Welder applies pressure on filler rod with one hand while applying heat to rod and one hand while applying heat to rod and base material with hot gas from welding base material with hot gas from welding torchtorch

• Fusion result of proper combination of heat Fusion result of proper combination of heat and pressureand pressure– Must be kept constant and in proper balanceMust be kept constant and in proper balance


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83Procedure for Hand Welding PVC Plastics with Round TipProcedure for Hand Welding PVC Plastics with Round Tip

1.1. Install heating element that produces from 450 Install heating element that produces from 450 to 500to 500ººF.F.

2.2. Attach round tip to torch.Attach round tip to torch.3.3. Set air pressure according to Set air pressure according to

recommendations by manufacturer of the recommendations by manufacturer of the equipment.equipment.

4.4. Obtain flat piece of PVC about 6 inches long, 4 Obtain flat piece of PVC about 6 inches long, 4 inches wide, and at least 3/31 inch thick; make inches wide, and at least 3/31 inch thick; make sure surface clean; clamp piece to workbench.sure surface clean; clamp piece to workbench.

5.5. Secure PVC filler rod 1/8 inch in diameter and Secure PVC filler rod 1/8 inch in diameter and cut end at a 60cut end at a 60ººangle with cutting pliers.angle with cutting pliers.


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84

6.6. Check for correct temperature.Check for correct temperature.7.7. Hold torch 1/4 to 3/4 inch from material to be Hold torch 1/4 to 3/4 inch from material to be

welded and preheat starting area and rod until welded and preheat starting area and rod until appears shiny and becomes tacky; rod held at appears shiny and becomes tacky; rod held at angle of 90angle of 90ºº to each side of base material. to each side of base material.

8.8. Too much heat in rod softens it so pressure Too much heat in rod softens it so pressure bends rod rather than forcing it into base bends rod rather than forcing it into base material; too little heat causes it to lay on surface material; too little heat causes it to lay on surface of material without being fused to it.of material without being fused to it.

9.9. Move torch up and down with fanning or weaving Move torch up and down with fanning or weaving motion in order to heat both filler rod and base motion in order to heat both filler rod and base material equally.material equally.

Procedure for Hand Welding PVC Plastics with Round TipProcedure for Hand Welding PVC Plastics with Round Tip


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85

10.10. Good start is essential.Good start is essential.11.11. Exert only as much pressure on rod as Exert only as much pressure on rod as

necessary to cause fusion to take place.necessary to cause fusion to take place.12.12. Too much forward pressure causes stretching Too much forward pressure causes stretching

which will lead to cracking as you weld.which will lead to cracking as you weld.13.13. Should notice small bead forming along both Should notice small bead forming along both

edges of welding bead and small roll forming edges of welding bead and small roll forming under welding rod.under welding rod.

14.14. Slight yellowing of rod and base material Slight yellowing of rod and base material caused by slight overheat.caused by slight overheat.



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86

15.15. To end, stop all forward motion and direct To end, stop all forward motion and direct quick heat directly at intersection of rod and quick heat directly at intersection of rod and base material. base material.– Remove heat and maintain downward pressure for Remove heat and maintain downward pressure for

several seconds until rod cool.several seconds until rod cool.

– Release downward pressure.Release downward pressure.

– Twist rod with fingers until breaks.Twist rod with fingers until breaks.



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87

Hand Welding with Round TipHand Welding with Round Tip



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88Hand Welding PVC Plastics with Round TipHand Welding PVC Plastics with Round Tip

Starting welding operation Torch motion during welding

Seelye Plastics Seelye Plastics



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89Hand Welding PVC Plastics with Round TipHand Welding PVC Plastics with Round Tip

Seelye Plastics

Note bead being formed along both edges of weld



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90

Hand Welding of JointsHand Welding of Joints

• Three basic types of butt joints used in Three basic types of butt joints used in plastic construction:plastic construction:– Square-groove butt jointSquare-groove butt joint– Single V-groove butt jointSingle V-groove butt joint– Double V-groove butt jointDouble V-groove butt joint


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91

Square-groove Butt JointsSquare-groove Butt Joints

• Generally made in light gauge sheets as Generally made in light gauge sheets as thick as 3/31 inchthick as 3/31 inch

• No preparation of edge requiredNo preparation of edge required• Root gap of approximately 1/64 inch Root gap of approximately 1/64 inch

necessary to permit full penetration necessary to permit full penetration through back sidethrough back side

• Welding from both side when possibleWelding from both side when possible• Acceptable when work not of critical nature Acceptable when work not of critical nature

and when cost considerationand when cost consideration


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92


1.1. Obtain two pieces of plastic sheet 6 inches Obtain two pieces of plastic sheet 6 inches long, 3 inches wide, and 3/31 inch thick.long, 3 inches wide, and 3/31 inch thick.

2.2. Set up pieces with root gap of 1/64 inch to Set up pieces with root gap of 1/64 inch to allow semimolten plastic to flow through to allow semimolten plastic to flow through to back side of joint.back side of joint.

3.3. Use same welding technique described for Use same welding technique described for beading (weld one pass on each side of plate).beading (weld one pass on each side of plate).

4.4. Inspect the weld carefully for faults.Inspect the weld carefully for faults.

5.5. Test weld.Test weld.


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93



Double square groove weld for butt joints, welded from both sides



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94

Single V-groove Butt JointsSingle V-groove Butt Joints

Used when only one side of plastic sheet Used when only one side of plastic sheet accessibleaccessible1.1.Obtain two pieces of plastic sheet 6 inches long, 3 Obtain two pieces of plastic sheet 6 inches long, 3 inches wide, and 1/8 inch thick.inches wide, and 1/8 inch thick.

2.2.Prepare pieces with 30Prepare pieces with 30ºº bevel and 1/31-inch flat bevel and 1/31-inch flat face at root.face at root.

3.3.Set up pieces with root gap of about 1/64 inch to Set up pieces with root gap of about 1/64 inch to allow semimolten plastic to flow through to back side allow semimolten plastic to flow through to back side of work.of work.

4.4.Weld first pass along root of weld.Weld first pass along root of weld.


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95

Single V-groove Butt JointsSingle V-groove Butt Joints

5.5. Weld two additional passes along edge of each Weld two additional passes along edge of each sheet. (Make sure that the weld is built up evenly; sheet. (Make sure that the weld is built up evenly; joint completely filled with overlaps on top beveled joint completely filled with overlaps on top beveled edges.)edges.)

6.6. Weld bead on back side; reinforced makes it Weld bead on back side; reinforced makes it somewhat stronger than double V-groove butt joint.somewhat stronger than double V-groove butt joint.

7.7. Inspect weld carefully for faults.Inspect weld carefully for faults.





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96

Double V-groove Butt JointDouble V-groove Butt Joint

Both sides of joint must be accessible for weldingBoth sides of joint must be accessible for welding

1.1. Obtain two pieces of plastic sheet 6 inches Obtain two pieces of plastic sheet 6 inches long, 3 inches wide, and 1/8 inch thick.long, 3 inches wide, and 1/8 inch thick.

2.2. Prepare edges of sheets to be welded with 30Prepare edges of sheets to be welded with 30ºº bevel (allow root gap of 1/31 to 1/64 inch).bevel (allow root gap of 1/31 to 1/64 inch).

3.3. Weld first pass along root of weld on one side Weld first pass along root of weld on one side (penetrate through to back side).(penetrate through to back side).

4.4. Weld two additional passes along edge of each Weld two additional passes along edge of each sheet.sheet.


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97

Double V-groove Butt JointDouble V-groove Butt Joint

5.5. Inspect welds carefully for good fusion and Inspect welds carefully for good fusion and appearance.appearance.

6.6. Turn plate over and repeat on other side.Turn plate over and repeat on other side.

7.7. Inspect welds carefully for faults.Inspect welds carefully for faults.




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98

Butt Joint TestButt Joint Test

• Tested by fracturing itTested by fracturing it– Place joint in jaws of vise with weld bead facing Place joint in jaws of vise with weld bead facing

away from you and 3/16 inch above and away from you and 3/16 inch above and parallel to top of vise jawsparallel to top of vise jaws

– Cover with clothCover with cloth– Strike with hammer on weld sideStrike with hammer on weld side

• If break occurs through weld bead with If break occurs through weld bead with some portion of weld on each piece – weld some portion of weld on each piece – weld goodgood


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99

Fillet WeldsFillet Welds

• Used to attach two sheets of plastic at 90º to Used to attach two sheets of plastic at 90º to each other in T-joints and corner jointseach other in T-joints and corner joints

• Vertical plate should be beveledVertical plate should be beveled• Welding from both sides strongerWelding from both sides stronger

45º

Kamweld Products Co. Kamweld Products Co.

45º



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100

Lap WeldsLap Welds

• Used to join two sheets or welding plastic Used to join two sheets or welding plastic angle to sheetangle to sheet

• Welds made by fusing overlapping areas Welds made by fusing overlapping areas with flat tip, or round tip with filler rodwith flat tip, or round tip with filler rod




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101

Edge WeldsEdge Welds

• Used to weld heads and bottoms into tanks or Used to weld heads and bottoms into tanks or boxes and to weld angle to edge of sheetboxes and to weld angle to edge of sheet

• Two flat surfaces set up side by side, and two Two flat surfaces set up side by side, and two edges welded togetheredges welded together

• If material heavy, edge of each plate chamfered If material heavy, edge of each plate chamfered and weld is a grooveand weld is a groove



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102

RepairsRepairs

• Two most common types of repairs are Two most common types of repairs are fixing cracks and replacing broken or fixing cracks and replacing broken or missing partsmissing parts

• Causes of cracksCauses of cracks– Internal stressInternal stress– Improper storage or handlingImproper storage or handling– Incorrect use of pieceIncorrect use of piece


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103

Repairing CracksRepairing Cracks

• Stop crack from traveling furtherStop crack from traveling further– Drill hole approximately 3/31 inch in diameter Drill hole approximately 3/31 inch in diameter

at each end of crackat each end of crack– If runs whole length, prepare crack by opening If runs whole length, prepare crack by opening

it up like V-grooveit up like V-groove• Use stick scraper to get 60º to 79º groove angleUse stick scraper to get 60º to 79º groove angle

• Most critical part of making quality weld is Most critical part of making quality weld is maintaining proper temperaturemaintaining proper temperature

• Weld both sides if possibleWeld both sides if possible• Finish weld and smooth down weld beadFinish weld and smooth down weld bead


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104

Replacing Missing PiecesReplacing Missing Pieces

• Cut out entire damaged area in shape that Cut out entire damaged area in shape that is round, square, or rectangularis round, square, or rectangular– Radius corners of square or rectangular shape Radius corners of square or rectangular shape

so no stress risersso no stress risers

• Take time to get good fit of replacement Take time to get good fit of replacement piecepiece

• Match material (cut from other damaged Match material (cut from other damaged parts)parts)

• Match material thicknessMatch material thickness


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105

High Speed WeldingHigh Speed Welding

• High speed welding tip increases average High speed welding tip increases average welding speed to over 4 feet per minute on welding speed to over 4 feet per minute on flatflat– Feeds welding rod automatically in right Feeds welding rod automatically in right

position and produces uniform weld headposition and produces uniform weld head

• One hand left free to steady or turn work One hand left free to steady or turn work and insert new rodsand insert new rods

• Cutting blade attached to tipCutting blade attached to tip• 500-watt heating element recommended500-watt heating element recommended


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106Operation of High Speed Welding TipOperation of High Speed Welding Tip




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107Procedure for High Speed Welding with Round RodProcedure for High Speed Welding with Round Rod

1.1. Secure two pieces of PVC about 18 inches Secure two pieces of PVC about 18 inches long, 3 inches wide, and 3/31 inch thick.long, 3 inches wide, and 3/31 inch thick.

2.2. Select high speed tool designed for diameter of Select high speed tool designed for diameter of filler rod to be used (cutting one end of rod at a filler rod to be used (cutting one end of rod at a 6060ºº angle). angle).

3.3. Set up equipment and allow unit to warm up.Set up equipment and allow unit to warm up.4.4. Hold welding unit straight down at a 90Hold welding unit straight down at a 90ºº work work

and travel angle in relationship to work.and travel angle in relationship to work.5.5. Hold shoe of high speed tool about 1/2 to 3/4 Hold shoe of high speed tool about 1/2 to 3/4

inch above surface of workpiece, and hold at inch above surface of workpiece, and hold at starting point.starting point.


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6.6. Insert beveled filler rod into preheated tube and Insert beveled filler rod into preheated tube and push into softened base material until rod push into softened base material until rod bends slightly backwards.bends slightly backwards.

7.7. Change travel angle of tip to about 60Change travel angle of tip to about 60ºº in in direction of welding (apply pressure on top direction of welding (apply pressure on top surface of rod until it starts to fuse to surface).surface of rod until it starts to fuse to surface).

8.8. Continue to exert pressure with shoe and start Continue to exert pressure with shoe and start pulling torch in the direction of welding.pulling torch in the direction of welding.

9.9. Continue to press on top surface of the rod Continue to press on top surface of the rod with shoe as you proceed with weld.with shoe as you proceed with weld.


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10.10. Once weld started, there can be no hesitation. Once weld started, there can be no hesitation. – Speed of weld can be increased by lowering travel Speed of weld can be increased by lowering travel

angle of welding unit to about 45 angle of welding unit to about 45ºº– Note flowlines which are similar to those visible in hand Note flowlines which are similar to those visible in hand

welding welding– Observe emerging rod constantly so any corrective Observe emerging rod constantly so any corrective

action can be taken immediately action can be taken immediately

11.11. If stretching occurs, withdraw tip, cut off rod, If stretching occurs, withdraw tip, cut off rod, and make new start before point where rod and make new start before point where rod started to stretch. started to stretch.

12.12. Rate at which weld proceeds governed by Rate at which weld proceeds governed by temperature, consistency of rod, and travel temperature, consistency of rod, and travel angle of welding unit. angle of welding unit.


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13.13. Make sure preheater hole and shoe Make sure preheater hole and shoe always in line with direction of weld so always in line with direction of weld so only material in front of shoe preheated.only material in front of shoe preheated.

14.14. To stop welding process, (a) withdraw tip To stop welding process, (a) withdraw tip quickly until rod is out of tube, and (b) quickly until rod is out of tube, and (b) bring tip quickly to 90bring tip quickly to 90ºº travel angle and travel angle and cut off rod with end of shoe.cut off rod with end of shoe.

15.15. Good speed weld in V-joint has slightly Good speed weld in V-joint has slightly higher crown than normal hand weld, higher crown than normal hand weld, and more uniform.and more uniform.


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111Welding Positions for High Speed TipWelding Positions for High Speed Tip




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112Adhesion of Flexible Strip to Base Material During High Speed WeldingAdhesion of Flexible Strip to Base Material During High Speed Welding




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113

High Speed Weld TestsHigh Speed Weld Tests

• Cut through joint and inspect for complete Cut through joint and inspect for complete bondingbonding– Strips should also be cut from work and Strips should also be cut from work and

subjected to tensile and bending stress testssubjected to tensile and bending stress tests

• If pressure test desired, make up small If pressure test desired, make up small box and subject it to water pressure testbox and subject it to water pressure test– Box can be similar to that used for metal arc Box can be similar to that used for metal arc

weldingwelding


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114High Speed Welding with a Plastic StripHigh Speed Welding with a Plastic Strip

• Strips come in different shapes and supplied in Strips come in different shapes and supplied in roll formroll form

• Only one pass necessary with stripOnly one pass necessary with strip

• Technique similar to welding with round rodTechnique similar to welding with round rod– Strip precut in length (1–2 inch for trimming)Strip precut in length (1–2 inch for trimming)

– Start weld by tamping with broad shoe of high Start weld by tamping with broad shoe of high speed tool on top of first inch of strip (80º travel angle)speed tool on top of first inch of strip (80º travel angle)

– Guide strip by hand and continue at sufficient speedGuide strip by hand and continue at sufficient speed

– To stop, remove tip and allow remaining strip to To stop, remove tip and allow remaining strip to pull throughpull through


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115

Welding Plastic PipeWelding Plastic Pipe

• Preparation and welding of pipe similar to that Preparation and welding of pipe similar to that used for flat materialused for flat material– One difference: torch and filler rod must follow One difference: torch and filler rod must follow

direction of round shapedirection of round shapeLaramy Products Co., Inc.

Fusion pipe welding machine



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116

Solvent Weld Process (Bonding)Solvent Weld Process (Bonding)

• Pipe and fittings solvent welded with MEKPipe and fittings solvent welded with MEK

• Solvent chemically etches surface of both Solvent chemically etches surface of both pipe and fittings so when joined, two pipe and fittings so when joined, two surfaces fused into each othersurfaces fused into each other– Like brazed copper or welded steelLike brazed copper or welded steel

• Original line of division no longer existsOriginal line of division no longer exists

• Joint stronger than either pipe or fittingJoint stronger than either pipe or fitting


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117

Procedure for Bonding PipeProcedure for Bonding Pipe

1.1. Use Schedule 40 ABS-DWV pipe and Use Schedule 40 ABS-DWV pipe and MEK solvent; cut pipe and remove all MEK solvent; cut pipe and remove all burrs; clean both pipe and fitting. burrs; clean both pipe and fitting.

2.2. In applying solvent, use brush large In applying solvent, use brush large enough to pass around pipe end or fitting enough to pass around pipe end or fitting socket quickly (fitting socket first and then socket quickly (fitting socket first and then pipe end).pipe end).

3.3. Insert pipe into fitting and position it with Insert pipe into fitting and position it with quick rotating motion of quarter turn or so.quick rotating motion of quarter turn or so.


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118

Procedure for Bonding PipeProcedure for Bonding Pipe

4.4. After full set, water tests may by applied After full set, water tests may by applied immediately; pressure systems require immediately; pressure systems require longer drying period because of higher longer drying period because of higher pressure tests.pressure tests.

5.5. Not all plastics nor solvents react the Not all plastics nor solvents react the same.same.

6.6. Test bonded joints by cutting through Test bonded joints by cutting through joint and inspect for thorough bonding joint and inspect for thorough bonding (cut strips from work and subject to (cut strips from work and subject to tensile and bending stress tests).tensile and bending stress tests).


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119

Gluing of PlasticsGluing of Plastics

• Approximately 250,000 different adhesivesApproximately 250,000 different adhesives• Selection criteriaSelection criteria

– Must understand how plastic will react to Must understand how plastic will react to adhesiveadhesive

– How joint will be appliedHow joint will be applied– What kind of environment it will be locatedWhat kind of environment it will be located

• Differences in chemical structure of Differences in chemical structure of adhesivesadhesives– All have certain technological propertiesAll have certain technological properties

• Preparation of splicing surface crucial stepPreparation of splicing surface crucial step


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120

Adhesives or Glue GroupingsAdhesives or Glue Groupings

• Melting glue (hot glue)Melting glue (hot glue)– Thermoplastic adhesive heated to melting Thermoplastic adhesive heated to melting

stagestage– Fast curing time, easy storage and handlingFast curing time, easy storage and handling– Solvent-free and efficientSolvent-free and efficient– Not capable of handling large splicing areasNot capable of handling large splicing areas

• Adhesive dispersion (wood glue)Adhesive dispersion (wood glue)– Not used in plastic joiningNot used in plastic joining– Used for woodworkingUsed for woodworking


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121


• Polycondensate (phenolics)Polycondensate (phenolics)– Two-component, thermoset adhesiveTwo-component, thermoset adhesive– Components react to each other when Components react to each other when

combinescombines– Strong splicing, wide range of useStrong splicing, wide range of use– Storage critical and can be expensiveStorage critical and can be expensive

• Polymerisate (cyanacrylates)Polymerisate (cyanacrylates)– One component, thermoplastic adhesiveOne component, thermoplastic adhesive– Needs catalyst to start reactionNeeds catalyst to start reaction– Fast curing time and strong bondFast curing time and strong bond


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122


• Polyaddition adhesive (epoxies)Polyaddition adhesive (epoxies)– Two-component, thermoset adhesiveTwo-component, thermoset adhesive– Two components react to each otherTwo components react to each other– Very strong splicingVery strong splicing– Wide range of useWide range of use– Provides enough time to work with itProvides enough time to work with it– Good heat resistanceGood heat resistance– Storage criticalStorage critical– Can be expensiveCan be expensive


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Procedures Prior to GluingProcedures Prior to Gluing

• Clean area where joining will occurClean area where joining will occur

• Make sure enough room for pieces, tools, Make sure enough room for pieces, tools, and personal protection availableand personal protection available

• Prepare equipmentPrepare equipment– Clean surfacesClean surfaces– Roughen splicing area by sanding or grinding Roughen splicing area by sanding or grinding

paperpaper– Remove grinding dustRemove grinding dust


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124Safety Considerations When Gluing PlasticsSafety Considerations When Gluing Plastics

• Eating, drinking, and especially smoking in splicing Eating, drinking, and especially smoking in splicing area should be prohibited at all timesarea should be prohibited at all times

• Open flames not allowed in close proximity because Open flames not allowed in close proximity because of flammability of fumes from most adhesivesof flammability of fumes from most adhesives

• Avoid skin contact because some solvents will find Avoid skin contact because some solvents will find their way directly into bloodstream; contact could their way directly into bloodstream; contact could also cause allergic reactionsalso cause allergic reactions

• Good ventilation important Good ventilation important • Read and strictly follow MSDS of adhesive usedRead and strictly follow MSDS of adhesive used• All adhesives basically special waste and should be All adhesives basically special waste and should be

disposed of in proper waydisposed of in proper way


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Care of Plastic PipeCare of Plastic Pipe

• Be careful in storing pipe and fittings Be careful in storing pipe and fittings (never store in sun) (never store in sun)

• Care must be taken in cutting pipeCare must be taken in cutting pipe

• Pipe must be laid out and cut with high Pipe must be laid out and cut with high degree of accuracy because errors cannot degree of accuracy because errors cannot be rectified with stress, heat, or hammerbe rectified with stress, heat, or hammer

• Plastic pipe must be supported properlyPlastic pipe must be supported properly


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Care of Plastic PipeCare of Plastic Pipe

• Never attempt to heat and bend plastic Never attempt to heat and bend plastic pipepipe

• Plastic pipe may be placed underground Plastic pipe may be placed underground with safety since it is impervious to soil with safety since it is impervious to soil acids in this countryacids in this country

• Plastic piping lends itself to prefabricationPlastic piping lends itself to prefabrication• Plastic pipe can be joined to pipe made of Plastic pipe can be joined to pipe made of

other materials only with the appropriate other materials only with the appropriate adapter fittingsadapter fittings

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