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Tip of the Month
 Calculations
of MIG Shielding Gas Use Are Bogus!
They are often low by over 80% !
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 Typical
welding cost calculations show MIG shielding gas is 4 to 5% of the total
welding cost. That’s an approach employed if your selling gas!
The method often
used to “estimate” shielding gas usage is to state, as an example: "If the flow rate is 35
CFH and the duty cycle is 30% (30% of the day the arc is actually on, versus
fitting a joint, moving to the weld location, chipping etc.) That means
each welder is using 35 CFH x 8 hr work day x 30% arc on time or 84 cubic
feet of gas used per day. Sound right? It's way off!
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Gas Use is in Reality - Far More! Why??
 Reviewing
what two published reports say about the
amount of MIG
shielding gas used by the average fabricator.
An article in
Trailer Body Builders magazine quotes a representative from
Praxair indicating their market survey findings show the average
fabricator using MIG welding consumes 6 times the
amount of shielding gas theoretically needed. (Reference 1)
Another article
in The Fabricator magazine confirmed this finding of up to 6
times the needed shielding gas being used in fabrication shops.
This
article discuses and quantifies a major reason for gas waste being the high
gas flow surge at the weld start. He also states companies can cut their gas
use in half. (Reference 2) |
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First,
evaluating the simplistic approach typically published:
General
Assumptions:
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0.035 diameter solid wire
operating at 190 amps. That deposits 5.5 lbs/hr when the arc is on.
Assume wire cost is $0.85/pound
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30 CFH Shielding Gas flow setting.
Assume a cost of $0.10/cubic foot for an argon based gas (= $10.00/100 cubic
feet)
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Direct Labor cost = $18.00/ hour
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Labor Overhead = 30% of Labor cost
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NO Gas Waste Case:
With the above assumptions and no consideration for
shielding gas waste, the resulting weld cost pie chart is
shown on the left. This is what is typically published as the method of
calculating shielding gas costs. It’s Bogus! |
Shielding gas is
shown as only 5 % of total cost and less than wire costs which are 7%.
This is based on an unrealistic assumption of no
gas waste.
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High Waste Case:
To evaluate a high waste case, assume gas waste is the high side defined
in the literature, i.e. gas usage is 6 times what is needed with a high
duty cycle which reduces Labor Percentage. |
Shielding gas would now be
32% of welding costs!
Probably higher than actual
unless your welders are also setting much to high a flow rate.
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Where Does the Extra Gas Come
From and Go?
Each time welding stops a
significant amount of excess gas fills the delivery hose from gas source to
feeder. This excess is expelled at high velocity at every weld start.
An example of a fabricator who tested our Gas Saver System (GSSTM)
provides a graphic picture of how much gas is wasted at the weld start.
 This
manufacturer of truck boxes selected a repetitive job of welding doors.
They put a full cylinder of shielding gas on one welding system with
the existing gas delivery hose. They welded 236
doors with that cylinder. They then put on a new full
cylinder and our
GSS
with no changes in gas flow setting or welding procedures. When the cylinder was
empty they had welded 632 doors!
That is 2.7 times more parts or said another way they were wasting 63% of
the gas they were using!
Note: gas leaks, high gas flow settings etc, are not part of this test.
The savings they achieved were just from reduced gas surge at the weld start!
CLICK
to SEE many more production examples at:
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Another reason for gas
waste is welders often believe “If some is good more must be better,”
when it comes to setting gas flow rates. With typical flowmeters we have
measured 150 CFH flow at the MIG Gun nozzle when the needle valve was fully opened. The article
mentioned above
(Reference 2
) stated in hundreds of surveys he performed only 20% had settings that
were at the correct level! We have observed many MIG machines with the float ball
pinned to the top of the tube! We have a recently patented locking system that
fits most flowmeters and blocks flow increases beyond what is desired.
CLICK to SEE this product. |
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Want to
calculate your gas usage and define how much is waste?
CLICK to GO TO
this
web page and download the FREE “Guide to Saving Gas.” |
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Don’t feel badly if you
find out your using far more gas than you should! An analysis done
for a major fabricator showed they were wasting 83% of their Argon and 90%
of their CO2! In addition to the high gas surge at
the weld start they were setting excess flow rates and they also had leaks.
Want information on how to
measure and monitor leaks on an ongoing bases?
CLICK TO SEE our Lean Welding
Manufacturing Self Study Programs related to gas us age.
Click
on Email ICON and ask for more information.
-
Weber, R., How
to Save 20% on Welding Costs. Trailer/Body Builders, Volume 44, Number 3,
January 2003
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Standifer, L.
R., Shielding Gas Consumption Efficiency. The Fabricator, Volume 30,
Number 6, June 2000.
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What do you think of the TIP of the MONTH?
Please
Email.
This positive feedback regarding our first Tip of the Month discussing
the effects of leaks in a gas delivery system was received:
"I have been in Metal manufacturing for over 25
years... Recently, I have been assigned to a department manufacturing
centrifugal compressor impellers where a cover is TIG and MIG welded to the
top of blades...Your Tip of the Month is the first plausible explanation
(for occasional defects) I have come across that could explain this
phenomenon and why it may be more prevalent in springtime or high humidity
periods."
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Free Technical Paper, "MIG SHIELDING GAS CONTROL"
CLICK ICON for PDF DOWNLOAD |
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Hear a Message from the President of
WA Technology (Who was also 2007 President of the 60,000
Member American Welding Society)
Click to Hear |
Purchase
Gas Saving
Products
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