CFH to PSI:
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)2 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 !"
