Presentation on theme: "Oxyfuel Welding and Cutting Equipment, Setup, and Operation"— Presentation transcript:
1Oxyfuel Welding and Cutting Equipment, Setup, and Operation Chapter 30Oxyfuel Welding and Cutting Equipment, Setup, and Operation
2ObjectivesDescribe how to maintain the major components of oxyfuel welding equipmentExplain the method of testing an oxyfuel system for leaksDemonstrate how to set up, light, adjust, extinguish, and disassemble oxyfuel welding equipment safely
3IntroductionOxyfuel welding, cutting, brazing, hardsurfacing, heating, etc.Use the same basic equipmentCylindersRegulatorsHosesHose fittingsSafety valvesTorchesTips
4Introduction (cont'd.)All oxyfuel processes use a high-heat, high-temperature flameProduced by burning a fuel gas mixed with pure oxygenGases are supplied in pressurized cylindersRegulators reduce gas pressure from the cylinderGas flows through flexible hosesTorch controls flowAcetylene is the most widely used fuel gas
5Pressure Regulators Reduce a high pressure to a lower working pressure Kept constant over a range of flow ratesVarious typesLow-pressure regulators, high-pressure regulators, single-stage regulators, dual-stage regulators, cylinder regulators, etc.Not interchangeable
6Regulator OperationRegulators work by holding the forces on both sides of a diaphragm in balanceGas pressure on back side of diaphragm is reducedTwo-stage regulatorsKeep pressure constant at very low or high flow ratesTwo sets of springs, diaphragms, and valves
8Regulator Gauges One or two gauges on a regulator Line drop One regulator gauge shows working pressureShows pressure at regulator and not at the torchSecond gauge shows cylinder pressureLine dropCaused by resistance of a gas flow
9Regulator Safety Pressure Release Device Safety release valve or safety discPrevent excessive pressure from damaging the regulatorSafety release valveMade of a ball held against a seat by a springSafety discThin piece of metal held between two sealsMust be replaced if used
10Cylinder and Regulator Fittings Ensure regulator is not connected to wrong gas or pressureCommon adaptersLeft-hand male acetylene cylinder fitting to a right-hand female regulator fittingArgon or mixed gas male to a female flat washer-type CO2 fittingConsiderationsKeep fittings free of dirt and oilScrew together freely by handReplace damaged connections
11Regulator Safety Precautions Key pointsBack off adjusting screw at shut down to prevent damageCreep is rising pressure on working side of regulatorIf leakage at the seat is severe: maximum safe pressure can be exceeded on working sideResults in damage to diaphragm, gauge, hoses, etc.Do not use regulators that creep excessively
12Regulator Care and Use Considerations No internal or external moving parts on a regulator or a gauge require oilingAdjusting screw becomes tight and difficult to turn: remove and clean with a dry, oil-free ragReplacing adjusting screw: be sure it does not become cross-threadedWelding is finished and cylinders are turned off: gas pressure must be released and adjusting screw backed out
13Welding and Cutting Torches: Design and Service Oxyacetylene hand torchesMost common type of oxyfuel gas torch usedCombination welding and cutting torchesMore flexibleStraight or dedicated cutting torchesLonger than combination torchesMost manufacturers make torches in a variety of sizes for different types of work
14Mixing the Gases Two methods for mixing oxygen and fuel gas Two gases mixed completely before leaving tipOne method uses equal pressuresGases are mixed in a mixing chamberSecond method uses higher oxygen pressureGases are mixed in an injector chamber
16Torch Care and Use Considerations Torch body contains threaded connections for the hoses and tipsWrench should never be used on one nut unless the other connection is protectedHose connections should not leak after they are tightenedValves should be easily turned on and offBubbles around the valve stem indicates a leaking valve packing
17FIGURE One hose-fitting nut will protect the threads when the other nut is loosened or tightened. Larry Jeffus.
18Welding and Heating Torch Tips Key pointsNo industrial standard tip size identification systemStudents must learn various tip sizesTip sizes: comparable to numbered drill sizesOn some torch sets: each tip has its own mixing chamber
19Torch Tip Care and Use Considerations Tips may have metal-to-metal seals or an O-ring or gasket between the tip and the torch seatTighten metal-to-metal seal tips with a wrenchTips with an O-ring or gasket can be tightened by handDirty tips can be cleaned with tip cleanersDamaged tips or tips with cleaners broken in them can be reconditioned
20Backfires Backfire Flame goes out with a loud snap or pop Causes: Touching the tip against the workpieceOverheating the tipFlame settings are too lowLoose tipDamaged seatsDirt in the tip
21Flashbacks Flame is burning inside the tip, torch hose, or regulator Produces a high-pitched whistleClose oxygen valve and then close fuel valveAllow torch to coolUsually indicates a serious problem with the equipment
22Reverse Flow and Flashback Valves Reverse flow valvePrevents gases from flowing through the torch into the wrong hoseIf gases are allowed to mix in the hose or regulator they might explodeFlashback arrestorWill do the job of a reverse flow valveWill also stop the flame of a flashback
23Care of the Reverse Flow Valve and Flashback Arrestor ConsiderationsBoth devices must be checked on a regular basisInternal valves may become plugged with dirtTest reverse flow valve: blow air backwards through the valveTest flashback arrestor: follow manufacturer's recommended procedureReplace of not functioning correctly
24Hoses and Fittings Characteristics Siamese hoses are molded together as one pieceOther hoses may be taped togetherFuel gas hoses must be red and have left-hand threaded fittingsOxygen hoses must be green and have right-hand threaded fittingsHoses are available in four sizes
25Hose Care and Use Considerations Hoses not in use: gas must be turned off and pressure bled offHoses are resistant to burns: not burn-proofHoses should be checked for leaksHose fitting can be changed if damagedTo replace hose end: hose is cut square
26Types of Flames Oxyacetylene flame settings Carburizing flame Excess of fuel gasNeutral flameBalance of fuel gas and oxygenOxidizing flameExcess of oxygen
27Leak Detection Leak-detection solution Solution can be: Premixed or concentrateMust be free flowingGood quantity of bubbles without filmSolution can be:DippedSprayedBrushed
28Figure 30-36 Safety chain cylinder. Larry Jeffus.
29FIGURE Connect the free ends of the oxygen (green) and the acetylene (red) hoses to the welding torch. Larry Jeffus.
30FIGURE 30-43 Select the proper tip or nozzle and install it on the torch body. Larry Jeffus.
31FIGURE Back out both regulator-adjusting screws before opening the cylinder valve. Larry Jeffus.
32FIGURE 30-45 Stand to one side when opening the cylinder valve FIGURE Stand to one side when opening the cylinder valve. Larry Jeffus.
33FIGURE 30-48 Adjust the regulator to read 5 psig (0 FIGURE Adjust the regulator to read 5 psig (0.35 kg/cm2g) working pressure. Larry Jeffus.
34FIGURE 30-50 Identify any cylinder that has a problem by marking it. Larry Jeffus
35Manifold SystemsUsed when there are a number of work stations or a high volume of gas will be usedMust be located at least 20 feet or more from workRooms used for manifolds can be also used for cylinder storagePiping for high-pressure side of the manifold must be steel, stainless steel, or alloyed copperShould be tested for leaks at a half times operating pressure
36Manifold Operation Considerations Clean pipes with oil-free, noncombustible fluid before regulators are attachedInstall regulators and purge the system with nitrogenFill pipes with oxygen or fuel gasSet line pressure as low as possible
37Summary You will work with experienced welders After you have developed skills and found a welding jobThese welders have developed many good shortcutsSafe way of setting up and testing a system should always be followedAlways refer to the manufacturer's operating instructions and safety recommendations