HTP Revolution 2500 Manual page 21

Here, you can select your pre-gas flow in
seconds. by turning encoder ( Fig.4,ref. 12 )
until you reach your desired pre-gas flow
duration.
In order to adjust the next value of the
sequencer, in this case t1 (slope up), press
button ( Fig.4,ref.9 );
When using a remote control, the t1 value is
fixed (not adjustable) as you typically use the
remote control to determine how fast the
slope up should be. With a momentary (arc
on/off) switch, the t1 adjustment feature is
available. Use button
move to t2 (slope down).
Here, you can adjust the slope down duration
in seconds. Like t1 (slope up), it is very
uncommon to set slope down when using a
foot pedal. However, setting a slope down
time may be done to implement a fail safe in
an attempt to avoid abrupt termination of the
weld and subsequent crater formation, which
leads to weld defects. Use button
( Fig.4,ref.9 ), to
(
Fig.4,ref.9 ) , to move to the final station of
the sequencer—post-gas flow .
When setting post-gas flow, more is better—
especially when in doubt. How much post-gas
flow you need depends on the material you
plan to weld, the cup you
plan to use, the amperage you plan to weld at,
and the amount of tungsten stick-out you use.
Some people advocate that you never need
more than 5 seconds of post-gas flow,
claiming that more post-gas flow is just a
waste of Argon. Well, let's put it this way. At
a bare minimum, you need to keep the
tungsten electrode shielded until the tungsten
is cold enough to where it does not react with
the ambient air. What does that mean? If the
shielding gas stops when the tungsten
electrode is still too hot, you will most likely
see gray or even black discoloration of the
tungsten, which is very bad! After you finish
welding, the tungsten should be the same
shiny silver color that it is when it was brand
new. If you weld stainless or even titanium,
post-gas flow times of 30 or 60 seconds, and
sometimes longer depending on the
amperage, are not unheard of. In order to
achive longer than 15 sec postflow re start the
arc at low amperage for a brief moment
occasionally before the post flow timer runs
out. During post-gas flow time, you also need
to hold the torch in position to shield the
metal from discoloring.
By pressing button
get deeper into the TIG - MAIN SETTINGS
submenu.
( Fig.4,ref.9 ); you