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?
