Daniel Bernoulli was born in 1700.  He developed the understanding and mathematical equations for defining the relationships between gas pressure, temperature and volume.  His equations form the basis of our understanding of how airplanes fly and many other gases behavior phenomenon.  For understanding and quantifying the shielding gas waste problem, first review the material presented in Why Am I Using So Much Shielding Gas? 

The higher pressure in the gas delivery hose when welding is stopped versus when welding, creates an excess volume of shielding gas stored in the hose. This excess gas is expelled when the torch switch is activated, even if just inching the wire to cut off the end.  It may occur in less than a second although we have found it may take over 5 seconds to reduce to the preset level in some installations.  You can hear the gas surge, it is obvious. Using the Bernoulli gas equations we can define the excess volume measured at standard temperature and pressure as being proportional to the differences in absolute hose pressure when stopped versus when welding.  Depending on the regulator/flowmeter or gas pipeline pressure, the waste can exceed 5 times the delivery hose volume every time the torch trigger is pulled.

WHY ARE GAS DELIVERY PRESSURES HIGH?

To provide automatic flow compensation for the inevitable flow restrictions that occur in production, i.e. spatter build-up, twisted cables etc is one key reason.  They have been designed that way since the introduction of TIG and MIG Welding!  See - - What is Automatic Flow Compensation and Why it is  Needed?

 "Lean Welding Manufacturing" Learning Program

"Optimizing Shielding Gas Use and Eliminating Waste" includes details of this information in a Do-It-Yourself 11 Module Program 

It quantifies waste due to surge flow, leaks, ways to monitor leaks and the gas flow settings where air is pulled into the shielding stream.  Unfortunately many are using far too much gas flow, wrongly employing the philosophy, "If Some is Good More Must be Better" !

"Daniel Bernoulli would turn over in his grave if he realized the lack of basic understanding and apparent lack of concern we have regarding shielding gas waste!"

Why is the Pressure so High in the Regulator/Flowmeter System?  Actually its a "Good Thing" Click Here to find out why!

Why some Extra Gas Flow is needed at the weld start?  Actually its a "Good Thing" Click Here to find out why!

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