WA Technology - MIG Gas Waste & Weld Quality
WA T echnologywww.NetWelding.comMIG Shielding Gas Control and OptimizationAlso Available as a Short Movie: http://youtu.be/H5nabh9deLEBy: Jerry UttrachiFind Out How To: Save money by reducing the high gas surge waste at each weldstart. Slash total MIG shielding gas use typically “in half.” Improve weld quality and reduce weld start spatter bylimiting the “gas blast” at each weld start that also pulls in air. Achieve these benefits easily and at low cost. Our patentedgas saving products eliminate past problems with gas surgecontrol devices, like simple orifices and low-pressuredevices. Prices start at 70.00. Over 15,000 of our patented Gas Saver Systems are in use. Payback is oftenmeasured in months!This Technical Paper Provides: A “one page” summaryHistory of MIG shielding gas flow controlMaximum usable shielding gas flow rates documentedMethods of setting shielding gas flowMaintaining consistent flow when inevitable flow restrictions occur in productionWhy some extra gas is needed at each weld start to purge air in the weld zone and gun nozzleHigh pressure is needed to achieve “coked flow” but causes excess stored gasExcess stored gas blasts out at each weld start and causes significant gas wastePublished reports show average MIG welder wastes up to 80% of shielding gas usedFabricator testimonial- shows a 63% total gas savings using a starting gas surge reductionDetails of patented, inexpensive Gas Saver System provided that reduces starting surgeGas Saver System improves weld start quality –includes fabricator testimonialsLow pressure, surge reducing, “Gas Guard” devices cause significant problemsOrifices or other flow control at the wire feeder cause problems and frustrate weldersCauses of gas flow restriction variations when welding are outlinedCalculations show average industrial MIG welder may waste 7 tons CO2/year/welderReferences: support comments and findingsAppendix A: Case examples of fabricators savings with Gas Saver SystemAppendix B: Fabricators report major problems with low pressure, surge reducing devicesAppendix C: Q & A; other reasons for gas loss;-1) leaks and 2) excess flowmeter settingsAppendix D: Why Gas Saver System purchases should be made at www.NetWelding.com?Appendix E: Check flow at nozzle/cup and demonstrate gas waste:Appendix F: Argon has recently increased 200% in Price. See why it will continue.Appendix G: Author & Company background:As a Past President of the American Welding Society (a volunteer position)Jerry Uttrachi gave technical talks about MIG Shielding Gas ControlOptimization at over 20 locations in the USA and conferences in Peru,Denmark, and South Korea.The talk was also presented at theInternational Institute of Welding (IIW) Annual Assembly in the CzechRepublic. This report summarizes the details presented in those talks.Author/company details in Appendix G.
Page 2 of 24One Page Report SummaryFrom the introduction of MIG welding in the 1950’s the developers knew excess shieldinggas flow rate created weld quality problems. Key claims as well as the teaching in theoriginal MIG patent state gas shielding must be: “ none turbulent to exclude air fromthe arc.” Several references sited in this report show MIG shielding gas flow rates cannotexceed about 50 to 60 cubic feet per hour (CFH) to achieve this non turbulent flow.The engineers that designed the gas flow control systems understood spatter buildup in theMIG gun nozzle and gas diffuser, bending of the small gas passage in the gun cable, etc,could cause significant variations in gas flow restrictions. They used a “choked flow” design, requiring aminimum of 25 psi upstream of the flow control device to automatically keep shielding flow at the presetlevel. However, the use of this high pressure stores excess gas in the gas delivery hose when welding stops,up to 7 times the physical hose volume. Most of this stored gas “blasts out” of the MIG gun nozzle at everyweld start! Most of this excess gas is wasted. About 87% of the excess gas volume is caused by theGas Pressure/Gas Volume relationship while 13% is due to hose expansion created by the high pressure.At each weld start, this excess stored gas in the hose from the gas supply to wire feeder exits the MIG gunnozzle at a peak flow rate often exceeding 200 CFH! This causes considerable shielding gas waste and veryturbulent flow. The turbulent flow lasts for several seconds even after the preset level is reached, whichmixes moisture-laden air into the gas stream. This creates inferior quality weld starts with excess spatterand possibly internal weld porosity.Published data shows the average MIG welder uses 3 to 6 times the amount of shielding gas they should!After conducting extensive laboratory and field tests, we have determined a major cause of this waste is thegas surge at the weld start and not the often-blamed gas leaks. A 1982 patent is cited showing that someextra shielding gas is needed at each weld start to purge air from the gun nozzle and weld start area.However, this initial extra purge gas must not occur at a high flow rate that creates excess turbulence - asoccurs with most standard shielding gas flow control systems.A patented, inexpensive device (our GSSTM) that reduces shielding gas waste is discussed. A fabricatoremploying it was able to weld 632 parts with one cylinder of gas using the same steady state shielding gasflow rate where one cylinder and their existing system was only sufficient to weld 236 parts. An appendixpresents tests of other fabricators who saved 40% to 50% shielding gas use with this gas saving system. Inaddition to gas savings, the reduced peak gas surge, flow rate at the weld start reduces spatter and internalweld porosity. Welders appreciate the system benefits.Past attempts at reducing gas surge and gas waste have frequently met with objections by welders. Somedevices tried reducing starting gas surge by using either: (a) low pressure, (b) orifices near the gas solenoidor (c) other flow controls mounted at the wire feeder like regulators or flowmeters. Some combine lowpressure devices with mounting at the wire feeder. Welders often rightfully reject these solutions or countertheir use by setting excess flow rates since they either eliminate: (a) automatic flow compensation by usinglow pressure causing flow variations or (b) the purge gas needed at the weld start by controlling flow at thefeeder. Or, in the worst case, (such as employed for a ”Gas Guard” foolish product) using a low-pressuredevice mounted at the feeder creating both problems! Examples are presented where fabricators removedthis and other devices because of poor weld performance.The patented GSS does not alter pressures and allows the welding operator to set any reasonable, shieldinggas flow rate. It eliminates the excess “gas blast” at each weld start and limits peak gas flow rate avoidingexcess turbulence. The GSS has no moving parts to maintain, set or adjust. Welders appreciate itsstarting benefits. Over 15,000 are in use in industrial shops! It is inexpensive, easy to install with paybackmeasured in weeks. A patented flowmeter “Flow Rate Limiter and Lock” is discussed that can control themaximum allowed gas flow setting. Argon has doubled in price- See Why in Appendix F.No time to read report? Watch this short summary: http://youtu.be/H5nabh9deLECopyright by W A Technology; 2021 - all rights reserved - DO NOT COPY
Page 3 of 24REPORT:MIG SHIELDING GAS CONTROLAND OPTIMIZATIONHistory of MIG WeldingA 1950 patent by Airco (reference 2)was the first that many sourcesacknowledge as producing the firstworkable MIG process. One of the keyelements was a MIG gun that providedquality shielding. In Claims 8, 9, 11and 12 they state the shielding mustbe, “.nonturbulent to exclude air fromthe arc.”Turbulent MIG Gas Flow RateSeveral sources quote MIG welding asbeing invented in the 1930’s; however,these systems did not work.Anexample is shown in the figure abovefrom a 1936 General Electric patent(reference 1.)When reading thepatent teaching it’s obvious, someelements required to produce qualitywelds were missing. One of thesemissing elements was proper qualitygas shielding.Only a few technical publicationsdiscuss the maximum shielding gasflow rate needed to produce a nonturbulent or minimum turbulence gasshielding. Two references that discussthe subject do quantify this maximumflow level. The first is by The WeldingInstitute (TWI) in Cambridge England(reference 3.) This research discussestests made using a number of methodsto measure air intrusion in the shieldinggas stream. For a common 5/8-inchsize ID industrial MIG gun nozzle thetransition from desirable laminar toturbulent flow occurs at 48 CFH.In another published article (reference4), Kevin Lyttle, then, Manager WeldingR&D for Praxair states; “In manyinstances production site surveys (offabricators using MIG sold and coredwire) determine that shielding gas flowrates typically are set in excess of50 CFH. This can contribute to poorweld quality as atmospheric gases aredrawn into the arc zone because ofexcess gas turbulence. Optimized flowenhances quality and reduces shieldinggas usage.”This supports TheWelding Institute findings of 48 CFHbeing the maximum flow rate producingno or low turbulence.More information on desirable flowrates is available in our LeanManufacturing Study Programs at:www.NetWelding.com/prod03.htmCopyright by W A Technology; 2021- all rights reserved - DO NOT COPY
Page 4 of 24Setting Gas FlowSeveral devices are used to setshielding gas flow rates. One type isused on cylinder or pipelinegas supply, a flowmeter withflow control knob. The knobadjusts a needle valve wherethe small opening sets the gasflow velocity. Assuming theproper pressure above the needlevalve, that velocity establishes the flowrate. A float ball is visible and rises inthe flow tube as flow rate increases.When used on cylinder gas supply aregulator precedes the needle valveand is set for a fixed delivery pressureranging from 25 psi to 80 psidepending on the specific model. Forexample, to prevent ice particleformation, flowmeters designed forCO2 service may use pressures from50 to 80 psi.The second type of flowcontrol is used forcylinder gas supply andemploys a very smalloutletorifice.Thepressure upstream of the orifice isvaried to control flow using a regulator.These are called regulator/flowgauges.The output gauge, although actuallymeasuring pressure, is calibrated toread flow based on the orifice size andgas type. Pressures for typical flowrates range from 40 psi to 80 psi. Theorifice is very small usually about0.025-inch diameter.In pipeline gas service, other devicessuch as fixed orifices or simply needlevalves may also be employed.Consistent Gas FlowIt is important that the flow rate set onthe flowmeter or regulator/flowgaugeremain constant while welding.However,restrictionsoccurinproduction that will alter flow such asspatter build-up in the MIG gun nozzle,bends occurring in the small gaspassages in the MIG gun cable, anddebris build-up in the gun conduit gaspassage (that often doubles as the wireliner retainer.) When the MIG processwas developed in the 1950’s theengineers used a technique to assureconstant flow rates regardless of thesenormal flow restrictions. This principleis called “choked flow” or critical flow.How Choked Flow WoksUnderstanding how the “choked flow”system works will help avoid the pitfallsof products sold which do not maintainconstant flow and cause flows to varywhentheinevitableproductionrestrictions occur.The following is a short explanation of“critical flow or choked flow.”Atechnical paper on the subject waspublished in The Welding Journal andhas more details (reference 5.)When gas passes through an cross the hole. However, once thegas flow velocity reaches the speed ofsound, the flow though the orificecannot increase above that velocity.Therefore, even with changes indownstream restrictions the flow willremain content. A specific minimumpressuredifferencecausesthis“choked flow” to exist.When thepressure upstream of the orifice isgreater than 2.1 times the downstreampressure the velocity will have reachedCopyright by W A Technology; 2021- all rights reserved - DO NOT COPY
Page 5 of 24the speed of sound in the orifice throat(for that gas at the upstreampressure.)Note: all pressures are measured asabsolute,i.e.gaugepressure 14.7 psi ( 15 psi for our purposes.)Using this fact, we can define thepressure needed above an orifice orneedle valve to produce “choked flow”in a MIG (or TIG) system.Thepressure needed at the wire feeder toachieve normal MIG shielding gas flowrates will vary from 3 to 8 psi. Theexact value will be dependent on theMIG gun length, number, andtightness of bends in the gun cable,spatter build-up in the nozzle and gasdiffuser etc. If we assume an averageof 5 psi is required, then that would be5 psi 15 psi to get absolute pressurestated as 20 psia.To achieveconstant flow regardless of normaldownstream restrictions will requireover twice that pressure above theorifice or needle valve or 40 psia.Stated as normal gauge pressure thatis 40 psia – 15 psi 25 psi. It is nocoincidencethatqualityregulator/ flowmeters use a minimumof 25 psi regulators! The engineersthat developed gas flow systems in the1950’s new MIG welding, were smartand knew what was needed!Information is presented later in thisreport showing the significant flowvariations that occur if lower pressuredevices are used.Some Extra Gas Needed at EachWeld StartThe preceding defined that it isimportant not to have an excessive gasflow rate to avoid turbulence in theshielding gas stream causing air to bepulled into and mixed with the shieldinggas. However, it is necessary to purgethe weld start area of air. In addition,air enters the MIG gun and MIG gunnozzle when welding stops. Stauffer ina 1982 patent (reference 6) defines theneed stating: ". air leaks back into theMIG gun and lines when welding isstopped. The air must be quickly purgedand replaced with inert gas to producehigh quality welds. Also, it is critical todisplace the air at the weld zone of thework piece upon initiating the weld." Hispatent defined a device that mountednear the wire feeder providing the extragas needed at the weld start. Headded a reservoir (item 112 in hispatent figure below) to store someinitial gas to be expelled at the weldstart. Unfortunately, the device alsouses relatively low pressure to avoidexcess surge, requiring the largereservoir and reducing the “AutomaticFlow Compensation” feature!Copyright by W A Technology; 2021- all rights reserved - DO NOT COPY
Page 6 of 24High Pressure Causes Initial GasSurgeof gas at 70 degrees and atmosphericpressure (that is what you pay for.)We defined that a minimum of 25 psiwas needed to have automatic flowcompensation.However,thispressure is much higher than the 3 to8 psi that is typically needed at thefeeder inlet to flow the desired amountof shielding gas. The pressure willreduce in the gas delivery hose to thatneeded to flow the gas volume comingout of the needle valve or orificethrough the feeder, MIG gun cable andnozzle. However, when welding stops,gas continues to flow through theneedle valve or the orifice and veryquickly fills the delivery hose. Thatflow continues until the regulatorpressure (or if on pipeline supply, thepipelinepressure)isreached.Pressure in some regulators andpipeline gas supply is as high as80 psi. The higher pressure causesan excess quantity of gas to be storedin the gas delivery hose from gassupply to wire feeder. The amount ofexcess is dependent on the absolutepressure difference and the hosevolume.If the absolute pressureincreases 5 times then the gas volumeincreases 5-fold as well.The shielding gas delivery hose issubjected to the same pressurerelationship. Therefore for an 80 psiregulator/flowmeter and only 3 psineeded to achieve the desired flowrate: (80 psi 15 psi)/(3 psi 15 psi) 5.3 times the physical hose volume ofEXCESS gas is stored in the hosewhen welding stops.To help with understanding excessgas storage, considera typical gas cylinderholding 310 CubicFeet (CF) of gas. Ithas only 1.8 CF ofphysical volume. Howdoes it hold all thatgas? By raising thegaspressureto2500 psi ( 2515 psia.)Therefore, the gasvolumewillbe2515/14.7 times 1.8(physical) CF 310 CFMostweldersunderstand that theexcesssurgecreatesproblems;they can hear it!However only a fewpublisheddocuments quantifythe typical amount ofHose Expansion Causes 13% MoreExcess Stored GasIn addition to the excess stored gasdue to increased pressure, our testsshow a standard 1/4-inch ID gasdelivery hose expandswhensubjectedtothese pressure levels.The volume increased13% with the internalpressureincrease.Therefore, the amount of excess gas is5.3 (due to pressure) X 1.13 6 timesthe physical hose volume. Every timethe MIG gun switch is pulled, thisexcess gas is rapidly expelled out thegun nozzle; most of it wasted!Excess Gas Expelled at the WeldStart Causes Significant Wastewaste.Looking first at documentation onwaste.An article in Trailer BodyBuilders magazine (reference 7) quotesa representative from Praxair, a leadingCopyright by W A Technology; 2021- all rights reserved - DO NOT COPY
Page 7 of 24producer and marketer of shieldinggases, indicating their fabricatorsurvey findings show the average MIGwelder consumes 5 to 6 times theamount of gas theoretically needed!Stated as a percentage, 80 to 83% ofthe shielding gas used is wasted!Another article in The FabricatorMagazine (reference 8) confirmed thisfinding of up to 6 times the neededshielding gas being used in fabricationshops.Just how much gas waste is causedby this surge at the weld start? Thefollowing is a case history of what onecompany found. We’ll also introduceourpatentedGas Saver System(GSSTM) to help explain this fabricatorstest results.Truck Box Fabricator Tests GSSA fabricator of truck boxes had 25 MIGwelders. They knew they were usingexcessgasandwanted totryourGSS as apossible solution.They use pipeline gassupply but to test the GSS theypurchased two gas cylinders with thesame gas mixture they employ. Theypurchased a flowmeter that utilized a50-psi regulator similar to their pipelinepressure. A part was selected thatthey made by the thousands, truck boxdoors.With their standard gasdelivery hose and normal weldingconditions, gas flow etc they installedone of the full cylinders and proceededto welded 236 doors until the cylinderwas empty. Only replacing their gasdelivery hose with the small volumepatented GSS, they used the samewelder, same welding conditions, andthe same shielding gas flow setting.The new cylinder was able to make 632doors before it was empty! That was63% less gas used. Or 2.7 cylinderswould be needed to weld 632 doorswith their old system! After about ayear using the 25 GSS’s purchased,they expanded their operation andadded 10 more weldingmachines. They called andasked for 10 more of the“Magic Hose!”Other fabricators test dataare shown in Appendix A.What is a GSS?The GSS is a patented device(reference 9) that eliminates the excess“gas blast” at each weld start and cancut gas use in half or more. The GSShas no moving parts and does muchmore than just save gas! The picturebelow shows the cross section of thiscustom extruded very heavy wall, fiberreinforced,gasdeliveryhose.In addition to reduced volume, the GSSavoids excess turbulence at the weldstart. It accomplishes this by limitinggas surge flow rate using a built-insurge orifice in the feeder/welder hoseend fitting. Note: the surge-limitingorifice does not limit setting any“reasonable, non-turbulent” steadystate flow, with an existing flowmeter,regulator/flowgauge or at the gassource on pipeline gas supply a fixedorifice or flowmeter.Copyright by W A Technology; 2021- all rights reserved - DO NOT COPY
Page 8 of 24Will this smaller ID gas hose, flow therequired amount of shielding gas?Yes, even 50 feet of hose will haveonly a moderate 4 to 5 psi pressuredrop at normal flow rates. On pipelinegas supplies with a 50-psi line, somefabricates use 100 feet of GSS hose.If longer gas lines are used, email:TechSupport@NetWelding.com wehave two recent patents that will allowany length hose to be used with equalresults. Also, see, Appendix C thatdiscusses the reason normal gasdelivery hose is 1/4-inch ID. It hasnothing to do with pressure drop!More Than Saving Gas: The GSSImproves Weld Start QualityThe GSS not only saves gas (typically,40 to 50 % is reported) it improvesweld start quality.This is bestdescribed with another fabricatorsexperience.A manufacturer had several MIGwelders using flux cored wire and CO2shielding gas to make weld repairs.Working with the welding engineer tocheck the amount of potential gassavings, a GSS was installed on therepair welder. All weld repair depositsrequired non-destructive testing beforethe repaired welds were accepted andthe pipe could leave the weldingstation. When making the first weldrepair with the GSS installed, theoperator was excited; he could “see”the improvement!Not in gas usagebutinthereducedinitialgas surge that heknew was causing internal weldporosity that made defective welds!He said he tried to weld with the wirecut back in the MIG gun and with thegun held high to have the start gassurge reduce in flow rate!Theaccompanying graph shows flow ratesmeasured in this application.It clearly shows what he was up againstand the GSS solution.The blue line shows the starting gasflow with the standard gas deliveryhose. Note, it peaks at 225 CFH! Atthis high gas flow rate, air is beingpulled into the shielding gas stream.Note the flow rate remains above 100CFH for about 3 seconds! Therefore,air was pulled into the gas stream foreven longer since turbulent flow takestime to return to desired laminar flow!Note, with the GSS the peak flow isunder 90 CFH and is only above 60CFH for a very short time!Of interest, although they measuredover a 40% gas savings, the weldquality improvement saved even moremoney and avoided the previousproduction bottleneck. After 6 monthsof use, the operator was asked what hefound in terms of repairs. He said hehardly had any need for rewelding,which was a common problem beforethe GSS was installed!Nitrogen and Hydrogen AreProblemsWhat’s wrong with air entering theshielding gas stream? Plenty! Aircontains three items that create weldingproblems. Nitrogen is 78% of air andOxygen 21%. Both are problems butCopyright by W A Technology; 2021- all rights reserved - DO NOT COPY
Page 9 of 24the water vapor (humidity) can be amajor problem as well. Elements canbe incorporated in the welding wire tohandle some amount of Oxygen.However, Nitrogen and the Hydrogenin water vapor can cause significantproblems and there is no way tocombine these ingredients withoutcausing other problems. Only 2%Nitrogen in the shielding gas is enoughtoproduceinternalporosity(reference 10.)Ludwig, using abubble chamber and mixtures ofshielding gas with various amounts ofnitrogen, found 1% was sufficient tocause problems (reference 11.)Assuming 2% Nitrogen will causeinternal porosity and possibly brittlewelds; since air is 78% Nitrogen only2%/78% or 2.6% air needs to mix withthe shielding gas to create problems.A turbulent shielding gas stream canmix far more than 2.6% air into the gasstream!Therefore, the excessively high gassurge at the weld start caused by moststandard shielding gas deliverysystems allows air to be mixed withthe gas stream at the weld start andcan cause internal weld porosity.In addition, some extra gas is neededto purge the MIG gun nozzle, cableand weld start area of air. If you everinadvertently started welding beforeturning on your shielding gas cylinder(haven’t we all) you have seen what aweld start looks like without shielding!A harsh arc, high spatter level, anoxidized weld and porosity wasprobably observed.Attempting to control flow at the wirefeeder is one-way insufficient extragas is available to purge the MIG gunnozzle and weld start area. The use offlow control orifices or flow controlregulators mounted at the feeder causelack of sufficient start gas. Excessstarting spatter occurs with thesesystems. Also, welders will often sethigher steady state flow rates inattempt to compensate for this lack ofsufficient purge gas.Maintaining system pressure andhaving a surge flow control orifice in thefeeder end of the GSS hose providesoptimized starting gas flow.Theneeded extra gas quickly purges the airin the weld start area and nozzle. Thepeak flow control orifice preventsexcessive flow rate and turbulence.Some research conducted by a majorwelding manufacturer employing one ofour patented GSS’s is of interest. Theyfound the weld start current and voltagein a critical aluminum weld can bemonitored with an oscilloscope andimprovements shown with flow ratesurge control and good weld startshielding.Use of Low-Pressure DevicesUnderstanding the problems created bythe start gas surge, some manufactureshad introduced low-pressure devices inattempt to solve the gas wasteproblem.However, they forgoautomatic flow compensation built intogas delivery systems since theinception of MIG welding! In fact, onemanufacturer who introduced a lowpressure system to their line of flowcontrols wrote a technical articlepublished in Flow Control Magazine(reference 12) that states: “ there areapplications in which a compensated unit(referring to higher pressure flowcompensatingregulator/flowmeters)may be required. When long lines fromthe flowmeter to the gun cause backpressure or when wind causes theshielding gas to blow off, the compensatedCopyright by W A Technology; 2021- all rights reserved - DO NOT COPY
Page 10 of 24system may be the solution to theseproblems.”We have found these low-pressuredevices create problems in mostcases, not just where it’s mentioned inthe technical paper! A number offabricators relayed the significantproblems encountered with a lowpressure device that mounts at thewire feeder. It has both problems:1) lack of automatic flow compensationcausing variations inflowfrompresetlevels and 2) sincemounted at the wirefeeder,insufficientextra gas at the startcausing inferior weldstarts.Tests wereconducted with thisdevice versus a normal 25 psiregulator/flowmeter (photo left).The following table shows the testresults with a conventional regulator/flowmeterthatoperates at 25 psiand a low-pressure“Gas Guard” device(photo right)bothsubjected to varyingMIGgunflowrestrictions.Bothwere initially set toflow 31 CFH (shownin green in the following table.)Placing a test pressure gauge after thelow-pressure device showed only 9 psiwas required to flow 31 CFH.As noted previously, 9 psi is wellbelow the minimum 25 psi needed toprovide automatic flow compensation.That means the shielding gas flow willnot only be determined by thepressure upstream of the flow controldevice (in this instance an orifice) butalso the downstream pressure thatvaries with flow restrictions.Thisfoolish device does not operate usingthe historic “choked flow” design.For these tests, the controls were left atthe initial settings as if they werepadlocked. MIG gun restrictions werethen added and removed, and flowmeasured at the gun nozzle with aportable flowmeter.FlowControlSystemConventional 25 psi Typical ProductionRestriction Range; psi 3 psi 4 psi 5 psi 6 psi 7 psi 8 psi313131313131CFH CFH CFH CFH CFH CFHLowPressure 373431272316DeviceCFH CFH CFH CFH CFH CFH 9 psiWith the conventional 25 psi regulator/flowmeter the gas flow did not changewith the restriction variations.Thepressure in the gas delivery hoseautomatically increased compensatingfor simulated spatter buildup in the gasdiffuser, clogged gas passage in theMIG gun (which for many MIG guns isalso the wire conduit,) spatter in thenozzle, twisted gun cables etc.Note with the low-pressure “GasGuard” device the flow reduced to a lowof 16 CFH and rose to 37 CFH!Four fabricators who documented theproblems with this device and theirexperiences are outlined in Appendix B.Note, one discarded 50 and another 70such systems! Tests of another lowpressure device showed it producedeven more flow variation! This deviceCopyright by W A Technology; 2021- all rights reserved - DO NOT COPY
Page 11 of 24sets flow by settingpressure (yellow arrow,photo right). It reduces thesurge but creates majorflow variation problemsmore difficult to analyze!BE CAREFUL; SOME OF THESE “SURGECONTROL DEVICES” DO NOT MENTIONTHEY USE LOW PRESSURE!A surge control flowmeter(photo right) at least indicates inthe literature, “operates atpressures lower than usual.”Unfortunately, it does notmention the problems thelower pressure creates!Welders just open the needle valvewhen restrictions occur and leave thehigh setting when restrictions reduce!Use of Restriction Orifices toControl FlowAnother method that has been used toreduce weld start gas surge isrestriction orifices mounted at thefeeder:1. One approach uses an orifice toreduce surge flow but still controlsteady state flow back at the gassource. This reduces surge butwhenweldingstopsgaspressure/volume still builds in thegas delivery hose. At each start,excess gas is expelled but it takessomewhat longer!2.Another approach is to use theorifice to control the steady stateflow. A very expensive electronic“supposed” gas saving device(EWR) also does somethingsimilar! With these approaches orwith any flow control placed at thefeeder there is insufficient extragas to purge the MIG gun nozzleand weld start area. The weld isessentially starting in air with theaccompanying problems. We havea report showing why the alsofoolish EWR device doesn’t work!Use of an Orifice at PipelineIn pipeline gas supply, an orifice is asatisfactory way to control shielding gasflow if placed at the pipeline outlet andused with our GSS. The flow rate iscontrolled, and sufficient extra shieldinggas is available to purge the weld startarea an
MIG SHIELDING GAS CONTROL AND OPTIMIZATION History of MIG Welding Several sources quote MIG welding as being invented in the 1930’s; however, these systems did not work. An example is shown in the figure above from a 1936 General Electric patent (referenc
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