On Jun 18, 11:50*pm, "Tim" wrote:

What do you hope to gain by a two-stage system?

Probably flame stability. When small tanks (any tank actually but is
more noticeable with small tanks) get low the high side pressure
changes by a greater % for a given amount of gas used resulting in
increased low side pressure creep. For a quick tack it's not
noticeable. Over a longer welding project the pressure will change
enough that you need to re-balance the flame. This is one of the
reasons 2 stage regulators are sold.

When setting up a paint booth air system it is a good idea to use 2
stage regulation to insure constant pressure at the gun for the same
reason.
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Leon McAtee