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1 PowerPoint to accompany Welding Principles and Practices 4th edition Edward R. Bohnart © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Chapter 31 Welding and Bonding of Plastics

2 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 2 Objectives 1.Describe uses of plastics. 2.Identify types of plastics. 3.Describe plastic welding processes. 4.Identify common plastic weld faults. 5.Make various plastic groove, fillet, and edge welds on sheet, plate, and pipe.

3 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 3 Plastics Synthetic polymers (thermoplastics) been used in world economy for over 100 yearsSynthetic polymers (thermoplastics) been used in world economy for over 100 years Welding and fabrication part of manufacturing industry since mid-1930sWelding and fabrication part of manufacturing industry since mid-1930s –Birth of hot-gas welding technique –No public documentation regarding requirements for use, design criteria, and application AWS covers plastics welding in Volume 3 of its Welding HandbookAWS covers plastics welding in Volume 3 of its Welding Handbook –Technical committee, GI, focused on plastic welding

4 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 4 Usefulness of Plastics Corrosion resistant, lightweight, and fatigue resistant, and when composite structures used, great strength-to-weight ratios achievableCorrosion resistant, lightweight, and fatigue resistant, and when composite structures used, great strength-to-weight ratios achievable Manufacturing simplifiedManufacturing simplified –Parts made in one step Abundant and recyclableAbundant and recyclable

5 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 5 Key Points for Welding Welding produces very strong jointsWelding produces very strong joints Some plastics can only be joined by weldingSome plastics can only be joined by welding Fusion line usually same as for bulk polymer, so easily recyclableFusion line usually same as for bulk polymer, so easily recyclable Relative insensitivity to surface preparation as pressure used to make weld forces surface layers from fusion lineRelative insensitivity to surface preparation as pressure used to make weld forces surface layers from fusion line Process time very fastProcess time very fast

6 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 6 Thermoplastic Polymers Consist of many strands intertwined but still capable of moving past each otherConsist of many strands intertwined but still capable of moving past each other Soften and/or melt when heated and can be weldedSoften and/or melt when heated and can be welded Can put heated polymers in cooled mold of shape required to form useful partsCan put heated polymers in cooled mold of shape required to form useful parts Thermosetting plastics usually formed by polymerization of polymers in a heated mold of the shape required for a partThermosetting plastics usually formed by polymerization of polymers in a heated mold of the shape required for a part –Joined by mechanical fasteners or adhesives

7 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 7 Requirements Before Starting Any Plastic Welding 1.Know application –Factors such as temperature usage, strength, corrosion resistance, and UV resistance 2.Know material –Critical in selecting filler metal and which joining process to use 3.Know welding process –Manually or automatically

8 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 8 Know Your Plastics Color should never be used for identificationColor should never be used for identification Look for identification numberLook for identification number – Can be referenced back through producer of part to determine plastic used Symbol used for identificationSymbol used for identification – Used in recycling of plastics – Look at Table 31-1 for rest of symbols

9 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 9 Plastics That May Not Have Symbols PolyurethanePolyurethane – Flexible, foamy-type plastic PolycarbonatesPolycarbonates – Very tough transparent plastic AcrylicAcrylic – Hard rigid plastic – Can be polished, cut and shaped by heating to 310ºF ABSABS – Good finish, heat and impact resistant

10 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 10 Plastics That May Not Have Symbols NylonNylon – Very tough plastic with high abrasion resistance – Can be turned and shaped well on lathe PTFEPTFE – Very low friction value and expensive MFMF – Thermoset (considered unweldable) – Heatproof and chemical resistant, but brittle

11 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 11 Plastics That May Not Have Symbols Urea formaldehydeUrea formaldehyde – Thermoset, heatproof, and chemical resistant Polyester resinPolyester resin – Thermoset, heatproof, and chemical resistant Epoxy resinEpoxy resin – Similar to polyester resin but more dimensionally stable and more expensive RubberRubber – Very flexible and stretchy

12 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 12 Scratching Test Not very accurate testNot very accurate test Gives some idea of type of plastic you are working withGives some idea of type of plastic you are working with Scratch with fingernailScratch with fingernail – Scratches: One of softer-type plastics: PE, PP, PTFE – Does not scratch: Not ABS, PVC, or any other of harder plastics

13 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 13 Sound Test Have different specific weights and surface hardnesses that cause them to sound different from one anotherHave different specific weights and surface hardnesses that cause them to sound different from one another – Take solid piece and drop it on hard and even surface from height of approximately 5–10 in. Hear specific tones Hear specific tones Train ear to different tonesTrain ear to different tones – Generally reliable enough to determine plastic’s family

14 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 14 Floating Test Only help identify plastic's familyOnly help identify plastic's family All plastics have specific weight higher or lower than specific weight of waterAll plastics have specific weight higher or lower than specific weight of water – Take glass of clean water at room temperature – Insert small piece of plastic to determine if it will float or not Only two plastics will float: PE and PPOnly two plastics will float: PE and PP

15 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 15 Burning Test Every plastic reacts differently when burnedEvery plastic reacts differently when burned Most accurate testMost accurate test – Have good ventilation – Remove thin sample and put it on surface resistant to heat – Light torch or some other flame source and attempt to ignite sample – Observe reaction

16 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 16 Identification of Plastics by Burning Plastic material observationPlastic material observation PE: Produces blue/yellow flame, smokes, and smells like paraffinPE: Produces blue/yellow flame, smokes, and smells like paraffin PP: Produces blue/yellow flame, drips, and smells like dieselPP: Produces blue/yellow flame, drips, and smells like diesel ABS: Smells sweet, lacks sooty flame, does not extinguishABS: Smells sweet, lacks sooty flame, does not extinguish Polyamide: Smells like burnt horn, stringy, does not extinguishPolyamide: Smells like burnt horn, stringy, does not extinguish Polycarbonate: Black sooty smoke, may extinguishPolycarbonate: Black sooty smoke, may extinguish PVC: Acrid smell, black smoke, does not extinguishPVC: Acrid smell, black smoke, does not extinguish

17 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 17 Two Basic Types of Plastics Thermosetting plasticsThermosetting plastics – Harden under heat – Through chemical reaction formed into permanent shapes that cannot be changed or welded ThermoplasticsThermoplastics – Soften when heated – Solidify when cooled with no chemical change – Can be machines, formed, and welded

18 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 18 Thermoplastics: Polyvinyl Chloride (PVC) One of most popular materials of constructionOne of most popular materials of construction Excellent physical propertiesExcellent physical properties – Ease of fabrication – Relatively low cost – Ability to be formed into wide range of products Wide forming-temperature ranges and self- extinguishing propertiesWide forming-temperature ranges and self- extinguishing properties Primary limitation is recommended working temperature range of 140º to 150ºFPrimary limitation is recommended working temperature range of 140º to 150ºF

19 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 19 Thermoplastics: Rigid Polyvinyl Chloride (PVC) Two broad classificationsTwo broad classifications – Type I has normal resistance to impact and high resistance to corrosion – Type II modified with rubber to increase impact resistance Best materials for general corrosion protection because of physical properties, chemical resistance, and low costBest materials for general corrosion protection because of physical properties, chemical resistance, and low cost Can be hot-air welded, cemented, or assembled by mechanical processesCan be hot-air welded, cemented, or assembled by mechanical processes

20 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 20 Thermoplastics: Modified High Impact Rigid Polyvinyl Chloride Developed for intermediate corrosion serviceDeveloped for intermediate corrosion service Readily formed in press and vacuum operationsReadily formed in press and vacuum operations Can be worked and welded at same temperature as regular polyvinyl chlorideCan be worked and welded at same temperature 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

21 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 21 Thermoplastics: Polyethylene (PE) Available in three classes of materialAvailable in three classes of material – Low density – Medium density – High density All same chemicallyAll same chemically Main differences in going from low to high density in corrosion resistance, working temperature, and tensile strengthMain differences in going from low to high density in corrosion resistance, working temperature, and tensile strength – Increase from low density to high density

22 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 22 Thermoplastics: Low Density (Branched) Polyethylene Lighter than metal and floats in waterLighter than metal and floats in water BurnsBurns Offers reasonably good corrosion resistanceOffers reasonably good corrosion resistance Cannot be joined by cement, can be welded using same class of rodCannot be joined by cement, can be welded using same class of rod Dry nitrogen recommended as source for hot gas welding unitsDry nitrogen recommended as source for hot gas welding units

23 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 23 Thermoplastics: Medium Density Polyethylene Produced as film, sheet, rod, tubing, and blockProduced as film, sheet, rod, tubing, and block Not cementableNot cementable Will burnWill burn Used for both pressure and conduit tubing and pipeUsed for both pressure and conduit tubing and 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

24 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 24 Thermoplastics: High Density Polyethylene Also referred to as low pressure polyethyleneAlso referred to as low pressure polyethylene 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 corrosion resistance of all three classesHighest working stress factor and best corrosion resistance of all three classes Reasonably high working temperature under low load conditionsReasonably high working temperature under low load conditions

25 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 25 Thermoplastics: Polypropylene (PP) Compared to polyethyleneCompared to polyethylene – Has lower impact strength, but tensile strength higher and working temperatures superior – Offers more resistance to organic solvents and degreasing agents Can be joined by welding, but not cementedCan be joined by welding, but not cemented Welding rod available in 1/8-, 5/31-, and 3/16-inch coil and flat stockWelding rod available in 1/8-, 5/31-, and 3/16-inch coil and flat stock Dry nitrogen recommended for weldingDry nitrogen recommended for welding

26 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 26 Thermoplastics: Acrylonitrile Buadiene Styrene (ABS) Two classifications of rigid ABS plasticsTwo classifications of rigid ABS plastics – Type I designed for normal temperatures – Type II for use in higher temperatures Cementing main joining methodCementing main joining method – Can 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

27 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 27 Acrylics Transparent and widely used as substitute for glassTransparent and widely used as substitute for glass Preshrunk before shipmentPreshrunk before shipment Necessary to specify corrosion resistance, crazing characteristics, and other specifications desiredNecessary to specify corrosion resistance, crazing characteristics, and other specifications desired Can be cemented and weldedCan be cemented and welded

28 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 28 Welding as a Method of Joining Plastics Welding of plastic pipe increasing in oil refineries and chemical plantsWelding of plastic pipe increasing in oil refineries and chemical plants Welding seals leaks instantly in new or old installationsWelding seals leaks instantly in new or old installations Similar to gas welding of metalsSimilar to gas welding of metals – All basic joint designs used – All welding positions possible

29 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 29 Basic Joints That May Be Formed and Welded Kamweld Products Co. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

30 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 30 Basic Joints That May Be Formed and Welded Kamweld Products Co. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

31 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 31 Preparation of Plastics LayoutLayout – Done directly on plastic sheet in pencil, soapstone, or china marker ShrinkageShrinkage – Preshrink for approximately 20 minutes at 250ºF, depending on gauge of material – Control cooling so does not buckle and deform FormingForming – Can be heated with heat gun and formed around metal forms to make curved shapes

32 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 32 Preparation of Plastics CuttingCutting – Same hand or power tools used to cut wool or metal SawingSawing – Heat buildup in saw blade due to poor heat conductivity of plastic 8–22 teeth blades with negative rake 8–22 teeth blades with negative rake Use special blades Use special blades

33 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 33 Preparation of Plastics ShearingShearing – Done at room temperature – Used for cutting of light gauge sheets RoutingRouting – Used for rimming edges of sheets or for shaping and recessing – Feed must be slow and continuous and swarf must be removed by compressed air

34 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 34 Preparation of Plastics Other working processesOther working processes – Drilling, punching, machining, milling, threading, knurling, riveting, and bolting SafetySafety – Same rules that apply in metalworking

35 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 35 Plastic 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 weldingInduction welding Dielectric weldingDielectric welding Microwave heatingMicrowave heating Spin weldingSpin welding Vibration weldingVibration welding Ultrasonic weldingUltrasonic welding Solvent weldingSolvent welding

36 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 36 Ultrasonic Welding High frequency vibration directed through plastic joinHigh frequency vibration directed through plastic join –Vibration causes friction, then heat, often causing solid fusion 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 – Fast – Clean Filler materials not needed Filler materials not needed DisadvantagesDisadvantages – Many tool designs required – Design rules not always available nor easily applied

37 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 37 Other Processes Linear vibration weldingLinear vibration welding – Similar to ultrasonic welding, but frequencies are in hundreds of hertz and amplitudes in fractions of an inch Spin/friction weldingSpin/friction welding – Two parts spun and contact area builds up heat through friction and pressure – Forces fusion between parts and forces out discontinuities – Advantages: Produces good weld, air does not enter during welding, inexpensive machines may be used – Disadvantages: Circular weld joints required

38 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 38 Hot-plate Welding Plastic brought into contact with heated plate to soften or melt plasticPlastic brought into contact with heated plate to soften or melt plastic Parts removed and pressed togetherParts removed and pressed together AdvantagesAdvantages – Simple, easy to perform DisadvantagesDisadvantages – Slow speed, typically butt joints, requires variety of platens

39 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 39 Injection Welding Unit Used in manual modeUsed in manual mode Injects molten welding rod below surface of plastic to create weldInjects molten welding rod below surface of plastic to create weld – Injection tip forms weld zone of molten welding rod Physical mixing of plastic substrate and welding rod makes strong, high quality weldPhysical mixing of plastic substrate and welding rod makes strong, high quality weld Automatic feed system lets welder work gun with one handAutomatic feed system lets welder work gun with one hand

40 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 40 Injection Welding Weld being made on inside of a corner joint Drader Manufacturing Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

41 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 41 Hot Gas Welding One of principle methods of welding plasticsOne of principle methods of welding plastics Two basic requirementsTwo basic requirements – Heat source – Welding rod that aids in fusion of weld to base material Joints identical to those in metal welding and same material preparationJoints identical to those in metal welding and same material preparation Flux not required in weldingFlux not required in welding

42 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 42 Hot Gas Welding Plastics poor heat conductors, so difficult to heat uniformlyPlastics poor heat conductors, so difficult to heat uniformly – Work in temperature ranges narrower than those in metal welding Only lower surface of welding rod fusibleOnly lower surface of welding rod fusible – Must apply pressure on welding rod to force fusible portion into joint and make permanent bond

43 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 43 Plastic 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 profilesAvailable in variety of colors, sizes, types, and profiles If don’t know base material and/or filler, perform rod fusion testIf don’t know base material and/or filler, perform rod fusion test 1.Scrape area clean 2.Melt rod and fuse it into base material; cool with water 3.Pull rod away to determine strength at fusion point 4.Repeat with various rods until best match found

44 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 44 Hot Gas Welding 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. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

45 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 45 Stretching and Distortion Some stretching of welding rod will always occurSome stretching of welding rod will always occur – Should not exceed 15% Thermoplastic rod becomes soft when heated enough to form weldThermoplastic rod becomes soft when heated enough to form weld In speed welding, stretching caused by too much pressure on rod or by plastic residue on shoe and in preheating tubeIn speed welding, stretching caused by too much pressure on rod or by plastic residue on shoe and in preheating tube

46 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 46 Stretching and Distortion Amount of stretch in completed weld determined by measuring length of rod before and after weldingAmount of stretch in completed weld determined by measuring length of rod before and after welding Stretching in multilayer welds must be held to minimumStretching in multilayer welds must be held to minimum – Checks and cracks show up as voids in finished weld and cannot be detected by visual inspection Shrinkage of weld upon cooling greater near crown than at rootShrinkage of weld upon cooling greater near crown than at root Distortion can be reduced by using speed welding and triangular welding rodDistortion can be reduced by using speed welding and triangular welding rod

47 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 47 Welding PVC Material must be kept clean at all timesMaterial must be kept clean at all times –Wipe with methylethyl-ketone or similar solvent Welding edges beveled or offset to provide areas for welding rod and permit better adhesionWelding edges beveled or offset to provide areas for welding rod and permit better adhesion –Cut bevels with jointer, sander, router, or plane Allow root gap in most procedures except when tack weldingAllow root gap in most procedures except when tack welding Thickness, shape, size, and strength dictates type of weld to useThickness, shape, size, and strength dictates type of weld to use

48 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 48 Welding Polyethylene and Polypropylene Precautions Base material should be freshly cut or scraped and cleanBase material should be freshly cut or scraped and clean Welding rod and material must be of same densityWelding rod and material must be of same density Subject to stress cracking (use only 1 foot of rod for 1 foot of weld)Subject to stress cracking (use only 1 foot of rod for 1 foot of weld) If welded joint will be under stress in service, weld will be subject to chemical attack that would not occur under normal circumstances (“environmental stress cracking”)If welded joint will be under stress in service, weld will be subject to chemical attack that would not occur under normal circumstances (“environmental stress cracking”) Rods tend to loop in direction of the weld (do not force rod and add undue strain on weld)Rods tend to loop in direction of the weld (do not force rod and add undue strain on weld)

49 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 49 Plastic Welding Equipment Hot-gas torches divided into two basic types:Hot-gas torches divided into two basic types: –Electrically heated Used in manufacturing plantsUsed in manufacturing plants Compact and easy to handleCompact and easy to handle –Gas heated Used primarily in field operationsUsed primarily in field operations Welding gas (compressed air or nitrogen) passes over heat source raising temperature to 450º–800ºFWelding gas (compressed air or nitrogen) passes over heat source raising temperature to 450º–800ºF

50 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 50 Simple Outfit for Plastic Welding Double-jacketed and insulated stainless-steel heating tube enclosing 110 volt, a.c.-d.c. heating elementDouble-jacketed and insulated stainless-steel heating tube enclosing 110 volt, a.c.-d.c. heating element Lightweight nylon handle for ease and comfortLightweight nylon handle for ease and comfort Twenty feet of neoprene-insulated, three-wire grounded electric cord inside neoprene air hoseTwenty feet of neoprene-insulated, three-wire grounded electric cord inside neoprene air hose Self-relieving air regulator and easy-to-read gaugeSelf-relieving air regulator and easy-to-read gauge Welding tipWelding tip

51 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 51 Miscellaneous Tools Wire brushWire brush Sharp knifeSharp knife Rotary sanderRotary sander RaspRasp Bending springBending spring FilesFiles SawsSaws C-clampsC-clamps Heat gunHeat gun

52 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 52 High Speed Electric Welding Torches Laramy Products Co. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

53 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 53 REPLACE WITH: boh73710_31-13.jpg Internal Construction of Typical Electric Welding Torch Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

54 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 54 Setting Up the Equipment 1.Make sure you have proper type of torch for work at hand. 2.Select proper heating element. 3.Relieve regulator-adjusting screw to prevent damage to regulator due to sudden excessive air pressure. 4.Connect welding unit to air or nitrogen supply and adjust regulator for 3 pounds pressure.

55 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 55 Setting Up the Equipment 5.Connect torch with 115-volt electric outlet. 6.Let torch warm up for 3 or 4 minutes; make sure compressed air or nitrogen flowing continuously through barrel of the torch. 7.Select proper tip or high speed welding tool for type of work. 8.Select proper air pressure for size of heating element (in watts) and for temperature desired at tip end.

56 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 56 Rules 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 turned offNever leave electricity on when welding gas turned off Volume of welding gas passing over heating element determines welding temperatureVolume of welding gas passing over heating element determines welding temperature –To increase temperature, reduce gas volume –To decrease temperature, increase gas volume –To determine temperature of heated air, hold thermometer 1/4 inch from end of welding tip

57 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 57 Rules for Welding with Electric Welding Torches Always ground torch to prevent short circuit, electric shock, and damage to heating elementAlways ground torch to prevent short circuit, electric shock, and damage to heating element Never touch end of torch barrel or welding tip when torch turned onNever touch end of torch barrel or welding tip when torch turned on To obtain maximum life from heating element, use recommended welding temperatureTo obtain maximum life from heating element, use recommended welding temperature Read manufacturer’s operating instructions before using torch for first timeRead manufacturer’s operating instructions before using torch for first time

58 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 58 Rules for Welding with Gas Welding Torches Be sure torch equipped with proper jet for heating gas being usedBe sure torch equipped with proper jet for heating gas being used Be sure welding gas supply is cleanBe sure welding gas supply is clean When regulating welding temperatures, reduce volume of welding gas or increase pressure of heating gas to raise the temperatureWhen regulating welding temperatures, reduce volume of welding gas or increase pressure of heating gas to raise the temperature –To lower temperature, increase volume of welding gas or reduce pressure of heating gas

59 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 59 Rules for Welding with Gas Welding Torches Never touch end of torch barrel or welding tip when torch turned onNever touch end of torch barrel or welding tip when torch turned on Always turn welding gas on before lighting torchAlways turn welding gas on before lighting torch Never leave torch lighted when welding gas is off (turn off flame before shutting off welding gas)Never leave torch lighted when welding gas is off (turn off flame before shutting off welding gas) Always read manufacturer’s instructions before using torch for first timeAlways read manufacturer’s instructions before using torch for first time

60 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 60 Inspection and Testing Strength of plastic weld dependent on combination of six interrelated factors:Strength of plastic weld dependent on combination of six interrelated factors: –Strength of the base material –Temperature and type of welding gas –Pressure on the welding rod during welding –Proper weld and joint selection –Proper material preparation before welding –Skill of the welder Dressing plastic welds decreases strength of completed welds by approximately 25%Dressing plastic welds decreases strength of completed welds by approximately 25%

61 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 61 Good Welds Kamweld Products Co. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

62 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 62 Faulty Welds Kamweld Products Co. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

63 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 63 Basic Bead Structure Discolored – Too Much Heat Good Flowlines – Good WeldNo Flowlines – Cold Weld Kamweld Products Co. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

64 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 64 Reasons for Faulty Welds Overheating base material or plastic filler rodOverheating base material or plastic filler rod Underheating base material or plastic filler rodUnderheating base material or plastic filler rod Improper penetration through entire root of weldImproper penetration through entire root of weld 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

65 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 65 Reasons 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 from workHeat at torch tip too close or too far away from work Heat at torch tip not centered on weld beadHeat at torch tip not centered on weld bead

66 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 66 Good Plastic Weld Requires Thorough root penetrationThorough root penetration Proper balance between the heat used on the weld and the pressure exerted on welding rodProper balance between the heat used on the weld and the pressure exerted on welding 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

67 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 67 Faulty Welds Porous Weld Poor Penetration ScorchingDistortion Laramy Products Co. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

68 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 68 Faulty Welds WarpingPoor Appearance Stress Cracking Poor Fusion Laramy Products Co. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

69 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 69 Visual Inspection Permits only partial evaluation of weld beadPermits only partial evaluation of weld bead Internal defects as incomplete fusion and penetration, air inclusions, and cracks cannot be determined by visual inspectionInternal defects as incomplete fusion and penetration, air inclusions, and cracks cannot be determined by visual inspection Visual evidence of a good weld is flowlines that present, continuous, and uniformVisual evidence of a good weld is flowlines that present, continuous, and uniform Will reveal faults such as voids, scorching, and notchingWill reveal faults such as voids, scorching, and notching

70 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 70 Testing of Welds Welded joints sites of potential weakness in plastic structureWelded joints sites of potential weakness in plastic structure Show welded joint fit for intended purposeShow welded joint fit for intended purpose –Achieved by appropriate destructive, nondestructive, and chemical testing techniques Organizations such as American Society of Testing Materials and American Welding Society have established procedures for testing plastics and plastic weldsOrganizations such as American Society of Testing Materials and American Welding Society have established procedures for testing plastics and plastic welds

71 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 71 Destructive Testing Tensile testTensile test –Used to evaluate butt joint-groove welds on rigid sheet –Value of 80–100% considered acceptable Creep rupture testCreep rupture test –Compares long term performance of plastic welds –Test under constant load and elevated temperature and time to failure measured; carried out in water

72 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 72 Destructive Testing Bending testBending test –While weld still hot, bend it double along axis of weld; another bend test conducted after 24 hours Burst testBurst test –Most effective way of testing pipe butt joint-groove welds and fillet welds on fabricated fittings and couplings Impact testImpact test –Weld subjected to sudden impact by hitting it with hammer

73 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 73 Destructive Testing Fracture mechanics testsFracture mechanics tests –More rigorous testing –Can be used to quantitatively qualify characteristics of plastic welds –Test conducted using either three-point bend loading or single edge notch bend specimen –If plastic brittle, use linear elastic fracture mechanics test –If plastics show great deal of crack tip plasticity, may require elastic-plastic fracture mechanics test

74 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 74 Nondestructive Testing Spark coil testSpark coil test –High frequency, high voltage spark-coil tester detects pores and cracks in plastic weld –Sparks have voltages up to 55 kilovolts and frequencies around 200 kilohertz Electro-Technic Products, Inc. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

75 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 75 Nondestructive Testing RadiographyRadiography –Most efficient method of plastic weld inspection –Gives complete detailed picture of internal characteristics of weld joint and permanent record –High cost Chemical testsChemical tests –Test specimen immersed in acetone for 2 to 4 hours –Dye penetrant painted or sprayed on weld

76 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 76 Instructions for Completing Practice Jobs with the Hot-gas Process Important “musts” concerned with plastic welding:Important “musts” concerned with plastic welding: –Small beads should form along each side of weld where rod meets base material –Rod should hold its basic round shape –Neither rod nor base material should char or discolor –Length of rod used should be no more nor less than length of the weld –Do not use oxygen or other flammable gases

77 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 77 Instructions for Completing Practice Jobs with the Hot-gas Process Plastics must be clean and dry prior to welding and during welding operationPlastics must be clean and dry prior to welding and during welding operation –Clean by scraping off first layer of material surface Best tool scraping bladeBest tool scraping blade –Pick up moisture and must be dried Plastic filler rod must be same composition as type of plastic being weldedPlastic filler rod must be same composition as type of plastic being welded –Considerations: Type of plastic, joint design, thickness of material, position of welding, and type of equipment

78 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 78 Instructions for Completing Practice Jobs with the Hot-gas Process Heat supplied by heated gasHeat supplied by heated gas –Compressed air, nitrogen, or inert gas –Gas passes through torch where heated by heating element and then directed through torch tip to surface of joint Filler rod can be fed by hand or automatically with use of high speed welding tipFiller rod can be fed by hand or automatically with use of high speed welding tip –Tip increases speed of welding Temperature of welding gas regulated by increasing or decreasing volume of gas to torchTemperature of welding gas regulated by increasing or decreasing volume of gas to torch

79 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 79 Using High Speed Welding Tip Seelye Plastics Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

80 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 80 Procedure for Tack Welding 1.Attach tack welding tip to torch. 2.Wait for 1 or 2 minutes so tip can reach proper temperature. 3.Hold tip at work and travel angle of approximately 90º and place directly on joint to be tacked. 4.Draw tacker tip along the joint for the desired length (about 1/2 to 1 inch long). 5.Unit now ready for continuous welding. 6.Practice.

81 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 81 Tack Welding Kamaeld Products Co. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

82 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 82 Hand Welding (Beading) Purpose to joint two or more pieces permanently together with rod or strip as fillerPurpose to joint two or more pieces permanently together with rod or strip as filler Welder applies pressure on filler rod with one hand while applying heat to rod and base material with hot gas from welding torchWelder applies pressure on filler rod with one hand while applying heat to rod and base material with hot gas from welding torch Fusion result of proper combination of heat and pressureFusion result of proper combination of heat and pressure –Must be kept constant and in proper balance

83 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 83 Procedure for Hand Welding PVC Plastics with Round Tip 1.Install heating element that produces from 450 to 500ºF. 2.Attach round tip to torch. 3.Set air pressure according to recommendations by manufacturer of the equipment. 4.Obtain flat piece of PVC about 6 inches long, 4 inches wide, and at least 3/31 inch thick; make sure surface clean; clamp piece to workbench. 5.Secure PVC filler rod 1/8 inch in diameter and cut end at a 60ºangle with cutting pliers.

84 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 84 6.Check for correct temperature. 7.Hold torch 1/4 to 3/4 inch from material to be welded and preheat starting area and rod until appears shiny and becomes tacky; rod held at angle of 90º to each side of base material. 8.Too much heat in rod softens it so pressure bends rod rather than forcing it into base material; too little heat causes it to lay on surface of material without being fused to it. 9.Move torch up and down with fanning or weaving motion in order to heat both filler rod and base material equally. Procedure for Hand Welding PVC Plastics with Round Tip

85 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e Good start is essential. 11.Exert only as much pressure on rod as necessary to cause fusion to take place. 12.Too much forward pressure causes stretching which will lead to cracking as you weld. 13.Should notice small bead forming along both edges of welding bead and small roll forming under welding rod. 14.Slight yellowing of rod and base material caused by slight overheat. Procedure for Hand Welding PVC Plastics with Round Tip

86 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e To end, stop all forward motion and direct quick heat directly at intersection of rod and base material. –Remove heat and maintain downward pressure for several seconds until rod cool. –Release downward pressure. –Twist rod with fingers until breaks. Procedure for Hand Welding PVC Plastics with Round Tip

87 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 87 Hand Welding with Round Tip Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

88 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 88 Hand Welding PVC Plastics with Round Tip Starting welding operation Torch motion during welding Seelye Plastics Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

89 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 89 Hand Welding PVC Plastics with Round Tip Seelye Plastics Note bead being formed along both edges of weld Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

90 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 90 Hand Welding of Joints Three basic types of butt joints used in plastic construction:Three basic types of butt joints used in plastic construction: –Square-groove butt joint –Single V-groove butt joint –Double V-groove butt joint

91 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 91 Square-groove Butt Joints Generally made in light gauge sheets as thick as 3/31 inchGenerally made in light gauge sheets as thick as 3/31 inch No preparation of edge requiredNo preparation of edge required Root gap of approximately 1/64 inch necessary to permit full penetration through back sideRoot gap of approximately 1/64 inch necessary to permit full penetration through back side Welding from both side when possibleWelding from both side when possible Acceptable when work not of critical nature and when cost considerationAcceptable when work not of critical nature and when cost consideration

92 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 92 Square-groove Butt Joints 1.Obtain two pieces of plastic sheet 6 inches long, 3 inches wide, and 3/31 inch thick. 2.Set up pieces with root gap of 1/64 inch to allow semimolten plastic to flow through to back side of joint. 3.Use same welding technique described for beading (weld one pass on each side of plate). 4.Inspect the weld carefully for faults. 5.Test weld.

93 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 93 Square-groove Butt Joints Kamweld Products Co. Double square groove weld for butt joints, welded from both sides Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

94 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 94 Single V-groove Butt Joints Used when only one side of plastic sheet accessible 1.Obtain two pieces of plastic sheet 6 inches long, 3 inches wide, and 1/8 inch thick. 2.Prepare pieces with 30º bevel and 1/31-inch flat face at root. 3.Set up pieces with root gap of about 1/64 inch to allow semimolten plastic to flow through to back side of work. 4.Weld first pass along root of weld.

95 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 95 Single V-groove Butt Joints 5.Weld two additional passes along edge of each sheet. (Make sure that the weld is built up evenly; joint completely filled with overlaps on top beveled edges.) 6.Weld bead on back side; reinforced makes it somewhat stronger than double V-groove butt joint. 7.Inspect weld carefully for faults. 8.Test weld. Kamweld Products Co. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

96 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 96 Double V-groove Butt Joint Both sides of joint must be accessible for welding Both sides of joint must be accessible for welding 1.Obtain two pieces of plastic sheet 6 inches long, 3 inches wide, and 1/8 inch thick. 2.Prepare edges of sheets to be welded with 30º bevel (allow root gap of 1/31 to 1/64 inch). 3.Weld first pass along root of weld on one side (penetrate through to back side). 4.Weld two additional passes along edge of each sheet.

97 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 97 Double V-groove Butt Joint 5.Inspect welds carefully for good fusion and appearance. 6.Turn plate over and repeat on other side. 7.Inspect welds carefully for faults. 8.Test weld. Kamweld Products Co. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

98 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 98 Butt Joint Test Tested by fracturing itTested by fracturing it –Place joint in jaws of vise with weld bead facing away from you and 3/16 inch above and parallel to top of vise jaws –Cover with cloth –Strike with hammer on weld side If break occurs through weld bead with some portion of weld on each piece – weld goodIf break occurs through weld bead with some portion of weld on each piece – weld good

99 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 99 Fillet Welds Used to attach two sheets of plastic at 90º to each other in T-joints and corner jointsUsed to attach two sheets of plastic at 90º to each 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. 45º Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

100 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 100 Lap Welds Used to join two sheets or welding plastic angle to sheetUsed to join two sheets or welding plastic angle to sheet Welds made by fusing overlapping areas with flat tip, or round tip with filler rodWelds made by fusing overlapping areas with flat tip, or round tip with filler rod Kamweld Products Co. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

101 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 101 Edge Welds Used to weld heads and bottoms into tanks or boxes and to weld angle to edge of sheetUsed to weld heads and bottoms into tanks or boxes and to weld angle to edge of sheet Two flat surfaces set up side by side, and two edges welded togetherTwo flat surfaces set up side by side, and two edges welded together If material heavy, edge of each plate chamfered and weld is a grooveIf material heavy, edge of each plate chamfered and weld is a groove Kamweld Products Co. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

102 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 102 Repairs Two most common types of repairs are fixing cracks and replacing broken or missing partsTwo most common types of repairs are fixing cracks and replacing broken or missing parts Causes of cracksCauses of cracks –Internal stress –Improper storage or handling –Incorrect use of piece

103 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 103 Repairing Cracks Stop crack from traveling furtherStop crack from traveling further –Drill hole approximately 3/31 inch in diameter at each end of crack –If runs whole length, prepare crack by opening it 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 maintaining proper temperatureMost critical part of making quality weld is maintaining proper temperature Weld both sides if possibleWeld both sides if possible Finish weld and smooth down weld beadFinish weld and smooth down weld bead

104 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 104 Replacing Missing Pieces Cut out entire damaged area in shape that is round, square, or rectangularCut out entire damaged area in shape that is round, square, or rectangular –Radius corners of square or rectangular shape so no stress risers Take time to get good fit of replacement pieceTake time to get good fit of replacement piece Match material (cut from other damaged parts)Match material (cut from other damaged parts) Match material thicknessMatch material thickness

105 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 105 High Speed Welding High speed welding tip increases average welding speed to over 4 feet per minute on flatHigh speed welding tip increases average welding speed to over 4 feet per minute on flat –Feeds welding rod automatically in right position and produces uniform weld head One hand left free to steady or turn work and insert new rodsOne hand left free to steady or turn work and insert new rods Cutting blade attached to tipCutting blade attached to tip 500-watt heating element recommended500-watt heating element recommended

106 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 106 Operation of High Speed Welding Tip Kamweld Products Co. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

107 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 107 Procedure for High Speed Welding with Round Rod 1.Secure two pieces of PVC about 18 inches long, 3 inches wide, and 3/31 inch thick. 2.Select high speed tool designed for diameter of filler rod to be used (cutting one end of rod at a 60º angle). 3.Set up equipment and allow unit to warm up. 4.Hold welding unit straight down at a 90º work and travel angle in relationship to work. 5.Hold shoe of high speed tool about 1/2 to 3/4 inch above surface of workpiece, and hold at starting point.

108 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 108 Procedure for High Speed Welding with Round Rod 6.Insert beveled filler rod into preheated tube and push into softened base material until rod bends slightly backwards. 7.Change travel angle of tip to about 60º in direction of welding (apply pressure on top surface of rod until it starts to fuse to surface). 8.Continue to exert pressure with shoe and start pulling torch in the direction of welding. 9.Continue to press on top surface of the rod with shoe as you proceed with weld.

109 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 109 Procedure for High Speed Welding with Round Rod 10. Once weld started, there can be no hesitation. – Speed of weld can be increased by lowering travel angle of welding unit to about 45º – Note flowlines which are similar to those visible in hand welding – Observe emerging rod constantly so any corrective action can be taken immediately 11. If stretching occurs, withdraw tip, cut off rod, and make new start before point where rod started to stretch. 12. Rate at which weld proceeds governed by temperature, consistency of rod, and travel angle of welding unit.

110 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 110 Procedure for High Speed Welding with Round Rod 13.Make sure preheater hole and shoe always in line with direction of weld so only material in front of shoe preheated. 14.To stop welding process, (a) withdraw tip quickly until rod is out of tube, and (b) bring tip quickly to 90º travel angle and cut off rod with end of shoe. 15.Good speed weld in V-joint has slightly higher crown than normal hand weld, and more uniform.

111 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 111 Welding Positions for High Speed Tip Kamweld Products Co. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

112 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 112 Adhesion of Flexible Strip to Base Material During High Speed Welding Kamweld Products Co. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

113 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 113 High Speed Weld Tests Cut through joint and inspect for complete bondingCut through joint and inspect for complete bonding –Strips should also be cut from work and subjected to tensile and bending stress tests If pressure test desired, make up small box and subject it to water pressure testIf pressure test desired, make up small box and subject it to water pressure test –Box can be similar to that used for metal arc welding

114 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 114 High Speed Welding with a Plastic Strip Strips come in different shapes and supplied in roll formStrips come in different shapes and supplied in roll 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) –Start weld by tamping with broad shoe of high speed tool on top of first inch of strip (80º travel angle) –Guide strip by hand and continue at sufficient speed –To stop, remove tip and allow remaining strip to pull through

115 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 115 Welding Plastic Pipe Preparation and welding of pipe similar to that used for flat materialPreparation and welding of pipe similar to that used for flat material –One difference: torch and filler rod must follow direction of round shape Laramy Products Co., Inc. Fusion pipe welding machine Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

116 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 116 Solvent Weld Process (Bonding) Pipe and fittings solvent welded with MEKPipe and fittings solvent welded with MEK Solvent chemically etches surface of both pipe and fittings so when joined, two surfaces fused into each otherSolvent chemically etches surface of both pipe and fittings so when joined, two surfaces fused into each other –Like 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

117 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 117 Procedure for Bonding Pipe 1.Use Schedule 40 ABS-DWV pipe and MEK solvent; cut pipe and remove all burrs; clean both pipe and fitting. 2.In applying solvent, use brush large enough to pass around pipe end or fitting socket quickly (fitting socket first and then pipe end). 3.Insert pipe into fitting and position it with quick rotating motion of quarter turn or so.

118 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 118 Procedure for Bonding Pipe 4.After full set, water tests may by applied immediately; pressure systems require longer drying period because of higher pressure tests. 5.Not all plastics nor solvents react the same. 6.Test bonded joints by cutting through joint and inspect for thorough bonding (cut strips from work and subject to tensile and bending stress tests).

119 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 119 Gluing of Plastics Approximately 250,000 different adhesivesApproximately 250,000 different adhesives Selection criteriaSelection criteria –Must understand how plastic will react to adhesive –How joint will be applied –What kind of environment it will be located Differences in chemical structure of adhesivesDifferences in chemical structure of adhesives –All have certain technological properties Preparation of splicing surface crucial stepPreparation of splicing surface crucial step

120 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 120 Adhesives or Glue Groupings Melting glue (hot glue)Melting glue (hot glue) –Thermoplastic adhesive heated to melting stage –Fast curing time, easy storage and handling –Solvent-free and efficient –Not capable of handling large splicing areas Adhesive dispersion (wood glue)Adhesive dispersion (wood glue) –Not used in plastic joining –Used for woodworking

121 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 121 Adhesives or Glue Groupings Polycondensate (phenolics)Polycondensate (phenolics) –Two-component, thermoset adhesive –Components react to each other when combines –Strong splicing, wide range of use –Storage critical and can be expensive Polymerisate (cyanacrylates)Polymerisate (cyanacrylates) –One component, thermoplastic adhesive –Needs catalyst to start reaction –Fast curing time and strong bond

122 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 122 Adhesives or Glue Groupings Polyaddition adhesive (epoxies)Polyaddition adhesive (epoxies) –Two-component, thermoset adhesive –Two components react to each other –Very strong splicing –Wide range of use –Provides enough time to work with it –Good heat resistance –Storage critical –Can be expensive

123 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 123 Procedures Prior to Gluing Clean area where joining will occurClean area where joining will occur Make sure enough room for pieces, tools, and personal protection availableMake sure enough room for pieces, tools, and personal protection available Prepare equipmentPrepare equipment –Clean surfaces –Roughen splicing area by sanding or grinding paper –Remove grinding dust

124 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 124 Safety Considerations When Gluing Plastics Eating, drinking, and especially smoking in splicing area should be prohibited at all timesEating, drinking, and especially smoking in splicing area should be prohibited at all times Open flames not allowed in close proximity because of flammability of fumes from most adhesivesOpen flames not allowed in close proximity because of flammability of fumes from most adhesives Avoid skin contact because some solvents will find their way directly into bloodstream; contact could also cause allergic reactionsAvoid skin contact because some solvents will find their way directly into bloodstream; contact could also cause allergic reactions Good ventilation importantGood 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 disposed of in proper wayAll adhesives basically special waste and should be disposed of in proper way

125 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 125 Care of Plastic Pipe Be careful in storing pipe and fittings (never store in sun)Be careful in storing pipe and fittings (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 degree of accuracy because errors cannot be rectified with stress, heat, or hammerPipe must be laid out and cut with high degree of accuracy because errors cannot be rectified with stress, heat, or hammer Plastic pipe must be supported properlyPlastic pipe must be supported properly

126 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. WELDING: Principles and Practices, 4e 126 Care of Plastic Pipe Never attempt to heat and bend plastic pipeNever attempt to heat and bend plastic pipe Plastic pipe may be placed underground with safety since it is impervious to soil acids in this countryPlastic pipe may be placed underground with safety since it is impervious to soil acids in this country Plastic piping lends itself to prefabricationPlastic piping lends itself to prefabrication Plastic pipe can be joined to pipe made of other materials only with the appropriate adapter fittingsPlastic pipe can be joined to pipe made of other materials only with the appropriate adapter fittings


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