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WATechnology       

Saving MIG Shielding Gas (And Improving Weld Starts)

THE PROBLEM:

The typical user of MIG welding consumes from 2 1/2 to 5 times the amount of shielding gas needed.  Two published reports quantify these estimates.

An article in the Fabricator magazine entitled “Shielding Gas Consumption Efficiency,” states the average fabricator uses from 18 to 30 cubic feet of shielding gas per pound of wire consumed.  This is 2.5 to 5 times the amount that is needed or up to 80% wasted gas!  They also define that the gas flow surge at the weld start is a significant cause of the waste.

An article in Trailer Body Builders magazine confirmed the previous published data and quotes a representative from Praxair, a leading producer and marketer of shielding gases, indicating their findings show the average fabricator consumes 30 cubic feet of gas per pound of MIG welding wire when only 5 cubic feet per pound may be needed (Note even 5 CF/lb is  high for some wire sizes, check Table below!)  They state, this is up to 6 times what is theoretically needed, or up to 83% wasted gas!

Depending on the price paid for shielding gas, the gas delivery pressure, the amount of arc time, the gas delivery hose length, and the frequency of MIG gun trigger pulls, this gas waste can cost well over $1000 per year per welder.

SIDE BAR

If MIG Shielding Gas Waste is so Prevalent, Why Has My Shielding Gas Supplier Not Told Me How to Fix the Problem? 

Understanding of the issues and reasons of shielding gas waste is rather complicated.  I managed a 30 person Material Technology R&D Laboratory for a producer of welding filler metals and half of the US Argon production. We developed MIG and TIG shielding gas mixtures as part of our development effort.  Neither myself or our group of engineers and metallurgists could have told you the main reasons shielding gas waste existed!  We knew it did, since when Argon was in short supply, as it was often at that time, the company would help large customers with hundred's of MIG welders in shipyards and offshore drill rig production, etc, fix leaks!  We knew the gas surge at the weld start was excessive and had a negative effect on weld starts.  We also knew a minimum of 25 psi gas pressure was needed to achieve "automatic flow compensation" to keep preset gas flow constant with the inevitable flow restrictions that occur in the MIG gun cables, spatter in the gas diffuser and nozzle etc.  However we did not conduct the research to quantify the reasons for gas waste and often would subjectively blame leaks since that was out of our control! 

I recall, at that time, a Lincoln Electric brochure for Innershield flux cored wire which didn't use shielding gas that stated in a section on costs; "We all know how much shielding gas is wasted."  They were refereeing to the standard cost calculations where gas cost is shown to be the flow rate times duty cycle-which we knew was bogus!  But how were we to put in a typical gas waste in the calculations when we  could not predict the amount?  And frankly, the company and all sales folks were selling gas! (See Gas Cost as Percentage of Welding Cost Information.)

Since forming WA Technology 12 years ago, we have made thousands of weld start and gas waste tests in our lab and hundreds at users.  After our extensive testing and customer visits we have found the gas surge at the weld start is often the most significant cause of shielding gas waste - NOT LEAKS!  We have evaluated a number of devices to reduce waste before inventing and patenting our simple, low cost Gas Saver System (GSS).  We and our customers have quantified the gas savings achieved by properly controlling gas surge at the weld start (typically, gas use can be cut in half.)  We understand why other approaches some have tried frustrated welders and have been altered, misused or removed such as low pressure devices, simple orifices, moving the flowmeter to the wire feeder etc.  We have also seen welders appreciate our GSS reducing peak flow at the weld start while still providing a controlled amount of extra gas to purge air in the weld start area without excess flow rate casing turbulence.  In addition, our GSS  does not interfere with their desired flow settings.  If limiting flow settings is desired, we have another patented device that locks the flow control knob on most flowmeters. See Flow Rate Limiter.

Another obvious reason why your gas supplier has not taken the time to help, is their financial disincentive to do so!  Our simple, low cost Gas Saver System (GSS) is patented; it is unique.  It will usually pay for itself in a very short time and save gas and costs for many years.  Thousands are in use - it works!  If you want a full explanation of waste and the solution, read the Technical Paper prepared from presentations given on the subject in many talks in the US and abroad - CLICK for FREE PDF.

MEASURING YOUR GAS WASTE

Measuring your shielding gas waste is straight forward.  If 0.035 solid MIG wire is being used, welding at 200 amps the deposit rate is 6 lb/hr of wire for every hour of arc time. A shielding gas flow rate of 30 CFH would be more than adequate.  Therefore for every pound of wire consumed 30 CFH / 5lb/hr or 6 CF of shielding gas.  Check past purchases of MIG welding wire and shielding gas for the same time period and compare.  Don’t be surprised if they are 3 to 4 times what they theoretically should be!

Validating the published data on what is typically needed; from the table below a typical deposition rate for  0.045 solid or cored, would deposit about 8 lbs/hr.  Using 35 CFH gas flow rate, that should consume 35 CFH/ 8 lbs/hr or 4.4 CF per pound of wire used or 15.7% of what the 30CF/lb they observed!  We have found similar large excesses in our tests with fabricators!

The accompanying table provides some deposition rates for typical wire types, sizes and amperages. Check out the far right column and note published survey data states the average MIG welders uses 30 CF of Gas Per /lb of wire used!

Wire Type

Size

Amps

Lbs/hr

CF Gas/  lb Wire Used

Solid

.035

175

  5.5

5.5 CF

Solid

.045

225

  6.8

4.1 CF

Cored

.045

250

  8.5

3.5 CF

Cored

1/16

300

  10.2

2.9 CF

Another way to provide an estimate of shielding GAS Waste can be made using the data in the far right column.  Select the wire type and size from the chart above and the average amperage used.  Not sure about the amperage - use the highest shown in the table to be conservative.  These data is based on using 35 CFH flow rate.

Example:  You used 46,000 lbs of 0.045 solid wire and your average amperage is about 225 amps.  Than multiple 4.1 CF Gas/1 lb wire X 46,000 lb = 188,000 CF of gas you should have used.  But you purchased 590,000 CF of gas.  Therefore 590,000 - 188,0000 = 402,000 CF was wasted or 402,000 Wasted / 590,000 Purchased =68% wasted!

Purchasing CO2 in pounds?  1 pound of CO2 = 8.7 CF gas at STP

Purchasing liquid argon in gallons?   1 gallon of liquid Argon = 113 CF gas At STP

Want More Details of Calculating Gas Waste?

A MAJOR CAUSE OF GAS WASTE

The accompanying figure schematically shows a typical MIG welding system.  The regulator/ flowmeter drops the pressure from the cylinder or gas pipeline to that needed to deliver the required amount of shielding gas to the MIG gun.

A small restriction orifice or a valve is used to control the gas flow.  Regulator/Flowmeters (Photo Below Left) outlet pressures range from 25 to 80 psi.  For CO2 shielding 80 psi is used to help prevent ice formation.  Flowmeters on pipelines allow pipeline pressure to exit the flow control valve when welding stops.  A typical  pipeline pressures 50 psi. 

Flowgauge/Regulators (Photo  Right) operate by setting a pressure above a critical orifice.  For most MIG shielding gas flow rates the pressure when welding stops will range from 40 to 70 psi.

However the pressure needed at the feeder to flow the shielding gas though the solenoid, fittings and MIG gun can 3 to 8 psi depending on MIG gun cable length and restrictions.  When welding is stopped, gas continues to flow through the needle valve or critical orifice and  increases in the gas delivery hose to that of the regulator output or pipeline.  Therefore the pressure in the gas delivery hose will be about 25/3 = 8 to 80/3 =26 times the pressure needed to flow the desired amount of gas!  For Flowgauge/Regulators 13 to 23 times what may be needed! 

When welding is started or the wire inched to cut off the end, the pressure drops rapidly to the typical 4 to 5 psi needed to provide the desired flow.  The excess gas that built up in the hose is usually expelled in a short time.  In fact the gas flow surge can exceed 200 CFH. The amount of gas expelled and wasted is proportional to the hose volume and the pressure build up when welding is stopped.  At higher regulator pressures such as 80 psi, the excess gas, when measured at standard pressure and temperature, exceeds 5 times the hose volume.

Turbulent Flow Causes Moisture Laden Air To Enter Shielding Stream

In addition to wasting shielding gas, the high gas surge at the weld start will cause very turbulent flow with any size gas cup.  This causes air to be pulled into the center of the shielding gas stream creating poor weld starts.  This turbulent flow takes a short time to stabilize into a more laminar, quality shielding gas stream even when flow returns to the normal desired level.  Therefore weld starts will contain entrained air in the gas stream even after the flow reaches the preset level.  In the February 2005 issue of Practical Welding Today magazine, Kevin Lyttle, Manager Welding R&D for Praxair states; In many instances, production site surveys determine that shielding gas flow rates typically are set in excess of 50 CFH. This can contribute to poor weld quality as atmospheric gases are drawn into the arc zone because of excessive gas turbulence. Optimized flow enhances quality and reduces shielding gas usage.”

In a 1893 technical paper Osborne Reynolds discussed tests made that showed there was a very well defined flow level  below which a smooth "Laminar" flow was achieved. Beyond that level a more chaotic "Turbulent" flow exits. He also defined if gas flow starts in a Turbulent mode, it takes time for the gas flow to become smooth and Laminar even when the velocity decreases.  Therefore at a weld start, the high velocity  surge of shielding gas exiting a MIG gun is Turbulent and will take some time to reach  the Laminar flow that is needed to eliminate air from the shielding gas stream. Photo right is a schematic of Osborne Reynolds standing next to his flow testing apparatus.

PAST ATTEMPTS TO SOLVE SURGE PROBLEM AND WASTE

Restriction Orifices have occasionally been  used to minimize the gas flow surge at the weld start.  However, assuming flow is still controlled at a regulator/flowgauge or flowmeter, significant gas waste still exists! If a pressure gauge is put in the shielding gas hose line the gas pressure changes observed are at similar levels as if the restrictor was not present.  Instead of the gas surge taking about a second to occur it takes longer at a lower flow rate. Significant gas waste occurs but over a longer time!  

If the restrictor is used to control the steady state flow then insufficient extra gas is available at the start to purge the MIG gun nozzle and weld start area of moisture laden air.  This causes similar problems to those caused by the high surge flow!  See Why there is a need for this extra gas and a special gas storage device defined by Stauffer in his 1982 patented system.  We have found welders see this lack of gas at the start and increase the steady state flow in attempt to compensate.  This may help to some degree but can't offset the need for enough gas to properly purge the weld start area.  Two specific observations at fabricators defined this problem.  One observation is outlined below regarding a Bar Joist manufacturer.  The other follows:

Flowmeters Placed at Wire Feeder Gas Inlet were observed at a shop with 100 MIG welders.  The fabricator had moved the flowmeters to the inlet of the feeder from the pipeline gas supply to reduce the gas surge at the weld start.  The steady state flow was observed on the welders during operation.  About 50% were set at 50 to 55 CFH, 25% were set near the top of the flow tube reading, which was 70 CFH.  The remaining 25% had the flow ball pinned to the top.  In our lab tests with this flowmeter we have found  to flow of 150 CFH with the needle valve fully opened!  It appears the welders were trying to compensate for the lack of the needed extra gas flow at the weld start.

Low Pressure Devices appear at first to be a possible solution.  However delivery systems have used pressures of a minimum of 25 psi since the introduction of TIG and MIG for very good reason.  That is the minimum pressure needed to provide automatic compensation of hose and MIG gun flow restrictions that occur in production!  We have measured changes in flow of 35% up to 65% in tests with low pressure systems without any change in flow settings,  See Why.

Higher pressure also helps to quickly delivery some extra gas at the weld start to purge the MIG gun nozzle and weld start area of moisture laden air.

PATENTED GAS SAVER SYSTEM

There is a simple way to significantly reduce MIG shielding gas waste due to gas flow surge.  First, employ a shielding gas hose with a much smaller internal diameter/volume.  At the low flow rates used for welding this creates a minimum pressure drop.  Secondly, incorporate a flow restriction orifice on the wire feeder end of the gas hose.  This has the benefit of reducing gas waste for very short time MIG gun trigger actuation such as when inching the wire to cut off the end.  The surge restricting orifice also has the benefit of improving weld starts by minimizing turbulence of the shielding gas stream.  Note a sufficient amount of extra shielding gas is still available to quickly purge the weld start area and weld nozzle of moisture laden air improving start weld quality.

 The patented WA Technology Gas Saver System (GSSTM) incorporates an 1/8 inch ID hose with a flow restrictor built into the hose connection at the wire feeder end.  The flow restrictor size is selected to reduce the surge at the start but allow the operator to have full control of the welding flow rate. It is also sized to allow a small amount of extra gas flow to assist in purging air that diffuses into the MIG gun gas line during the stoppage. It has a large OD and fiber reinforced construction to provide a robust product which will not kink or flattened when stepped on.  The hose volume is proportional to the hose ID squared therefore it results in a 4 fold or 75% reduction. The total % reduction is calculated from this volume decrease and the small pressure drop in the GSS hose and surge restrictor and exceeds 80%.

SOME EXTRA GAS IS NEEDED AT THE WELD START

Just as the high gas surge causes wasted gas; if gas flow control is attempted at the wire feeder with an orifice, flowmeter or needle valve then the surge is eliminated but now little or no extra gas is available at the weld start to purge the MIG gun nozzle and weld start area of gas.  We have found in these instances welders raise the steady state gas flow in attempt to compensate so they are not starting in air!  Check out the details of why this is necessary.  This creates considerable gas waste!

SELECTION OPTIONS AND INSTALLATION

To gain the benefits of this patented system simply replace the existing gas hose with the WA Technology GSS.  For industrial MIG systems hose end fittings are supplied with Compressed Gas Association (CGA) 032, 5/8 inch-18 male threaded connectors (also called “B” size, left in photo).  GSS components and systems may be ordered in from 3 to 50 foot lengths. These lengths are satisfactory with most commercial regulators or gas pipeline pressures. It is possible to use 100 foot or longer lengths however the regulator outlet or gas pipeline pressure must be known before ordering.

For some feeders or regulators where a CGA fitting is not used, such as when a hose barb is on the feeder, the GSS can be ordered with simple hose splice connectors (right in photo).  This allows the existing hose to be cut and the GSS assembly added by splicing to a 1/4 or 3/16 inch ID hose.  Both systems incorporate a flow restriction orifice on the end connected to the feeder and  perform the same.

TIG WELDING?

If you are TIG welding the GSS will also save you money, especially if your system incorporates a gas solenoid.  The gas surge at the weld start is significantly reduced in velocity to improve shielding.  In addition the heavy wall thickness of the GSS hose makes it resistant to leaks caused by abrasion.  A hose splice connection is available for connecting the GSS to an existing 1/8 inch diameter TIG hose.

PRODUCTION RESULTS

A number of fabricators have performed usage measurements comparing the GSS with a conventional delivery hose.  They reported savings in gas usage of from 30 to 63%.  Many also report welders are very impressed with the improved starts from the significant reduction in initial gas flow peak surge.

A fabricator of truck boxes reports his test results with the GSS.  They selected a repetitive application, welding doors.  Using a full cylinder with their standard gas delivery hose they were able to fabricate 236 doors.  With no other changes than to replace the gas delivery hose with our GSS they welded 632 doors with a full cylinder of gas.  That is a 63% shielding gas savings!  They immediately purchased 25 systems for all their welders.  Two years latter they added 10 more MIG welders and called and asked for 10 more “Magic Hose!”

This production example shows why extra gas at the weld start can reduce gas use. Welders at a Bar Joist fabricator wanted more gas flow than the 45 CFH that was set with the orifices installed at their feeders.   In some instances they were drilling the orifice to achieve more gas flow.  A GSS  was installed with gas control at the pipeline drop. This provided a controlled amount of extra gas at the weld start.  By providing extra gas at the start the GSS was able to improve starts and the steady state flow could be reduced to 35 CFH  or less and the welders still saw a significant improvement!  That was because the same amount of extra gas was still provided at the weld start. Overall gas savings were documented at 25% and most important  welders were pleased with the improved weld performance because extra start gas quickly purged the weld area!   Check out the details.

See Specifics of 15 Case Histories

WITH YOUR PURCHASE

When you purchase your GSS it will include simple installation instructions.

BOTTOM LINE

The WA Technology GSS has no moving parts to wear, repair or leak; no pressures to set or knobs to adjust.  It’s unique, patented design maintains the gas pressure in the delivery hose.  This allows a small amount of extra gas flow at the weld start to quickly purge air and moisture in the weld zone and air that enters the MIG gun shielding gas cup, MIG gun body and cable during weld stoppage.  Maintaining the higher pressure also retains the systems ability to automatically compensate for varying pressure drops in the delivery hose when inadvertently pinched, squeezed, bent, etc.  Pressure drops in the  MIG gun due to conduit bending and spatter build-up in the front end are also automatically compensated to maintain the preset flow. That is a key reason regulator flow systems are designed to operate at these pressures.  Want to understand why high pressure regulator/flowmeters are "A Good Thing?" Click Here. The GSS does not interfere with the welders ability to adjust the shielding gas flow within any reasonable flow level desired.

The GSS hose is made with a heavy wall thickness and with fiber reinforced construction to provide a robust product.  It will continue to flow even when stepped on. The heavy wall thickness makes the hose resistant to leaks caused by abrasion.

For most applications the GSS will pay for itself in gas waste reduction alone in a matter of weeks.  The improved weld starts and the reduced cylinder handling are added benefits which may be more important in some applications. 

The system is backed with a  money back guarantee.

Hear a Message from the President of

WA Technology   (Who was the 2007 President of the 52,000 Member American Welding Society)

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Sales Literature

PDF File for

 Downloading,

 

Click on ICONS

 

 Technical Paper

"MIG GAS CONTROL"

 

Copyright by WA Technology, LLC,

4313 Byrnes Blvd, Florence, SC 29506-8310

US Patent Numbers 6,610,957; 7,015,4126; 7,019,248 and 7.,462,799. 

Publication Number:  WAT 811

 

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* US Patent  # 6,610,957;  "Welding Shielding Gas Saver Device" August 26, 2003,  Patent Pending in other countries.  
 The "Flow Rate Limiter" device is covered by 2008 US patent # 7,462,709.  Other site material may be covered under  Patents # 7,015,412 or # 7,019,248 .
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Last modified: 01/30/12

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