|
                        
| |
|
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)
Click to Hear |
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
▲ HOME
►GSS
PRODUCTS
|
