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Use This Web Page to Find Information About Setting MIG Shielding Gas Flow  Rates, Reducing Waste and Improving Weld Quality. 

Have a question about converting CFH to psi?  Click to see why you can't!

See Web Page With Suggested Flow Rate Chart


See Causes for MIG Gas Usage Being Over 3 Times What Should Be Used.


The Manager of Welding R&D for the Leading Shielding Gas Producer, Praxair, Says Using Over 50 CFH Gas Flow - "Creates Weld Defects."


Osborne Reynolds in 1893 Found That  a Clearly Defined Velocity Exists Where Gas Flow Goes From a Smooth Laminar Flow Mode to Chaotic Turbulent Flow.


In Pipeline Shielding Gas Supply, Pressure Changes Cause Significant Flow Changes.  In Addition, if Flowmeters Are Used, Many Are Designed to Operate and are Calibrated at 25 psi and Pipeline Pressures Are Often 50 psi.  In That Situation a Flow Set at 31 CFH Will Actually Be Flowing 40 CFH- SEE WHY.


See Ideal Gas Delivery System


Why Orifices Placed at Wire Feeder to Control Flow Are Often Justifiably Rejected By Welders


Using an Orifice to Control Flow at Pipeline Drop is "Fine."  Combined with The Gas Saver System Sufficient Extra Gas is Provided at the Weld Start to Purge the Weld Start Area.  Pressure is Maintained to Retain "Automatic Flow Control."


Gas Control System Must Provide Some Extra Gas at Weld Start


Pressure  in Flow Control Devices and in Pipelines Must be Over 25 psi to Provide an Important Feature the  Inventors of MIG and TIG and Early Designers of Shielding Gas Control Understood and Used and Some Have Forgotten - "AUTOMATIC FLOW COMPENSATION !"



We occasionally get a question about converting CFH (cubic feet per hour) to psi (pounds per square inch).  The short answer is that is mixing apples and oranges - they measure different things!

This video discusses CFH versus psi: Set MIG Shielding Gas Flow Rate

To understand why these two different units can not be converted one to another the general issue about conversions called "Dimensional Analysis" is useful to know:

Look at the units of an item and try to see what is needed for conversion to other units.  For example, a simple conversion of pounds per square inch (psi) to pounds per square foot (lbs/ft2) is straight forward:

You must be able to get the correct units when you finish, so lbs/in2  must convent to lbs/ft2   We know there are 12 inches in a foot so:

lbs/in2 X  (12 inches/foot)2  = lbs/ft2 or lbs/in2 (psi) X  144 = lbs/ft2   The in2  in the denomination (bottom) of the psi term cancels the in2 in the numerator (top) of the  (12 in/ft)and leaves ft2 in the denominator which is what is needed.  What was done by multiplying by 12 inches/foot or in this case (12 inches/foot)2 is you multiplied by 1, changing nothing.  Note 12 or 13 is still 1!

Now, try that with CFH to psi.  Foot3/hour cannot get to pounds/inch2 !

You would have to multiply by pounds/foot3 and inches2/hour.  Those are not equivalents!  They are not 1.  There is no such term.  So when checking your calculations first check the units.   If the units don't check than something is wrong.

If you still want to know what psi will provide a given CFH for a MIG system see this page: "AUTOMATIC FLOW COMPENSATION !"


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