Tweco Tri-Arc Serie - Manual (Page 22)

5-2
Problem Cause Solution
In gouging, free carbon
deposits at varying
groove intervals; in pad
-washing, free carbon
deposits at various spots
on the washed surface.
1. A shorted electrode
on the workpiece. In
manual gouging, this
is a result of excessive
travel speed for the
amperage used and for
the depth of the groove
being made. In mecha-
nized operations, this
is a result of excessive
travel speed or using
a flat-curve, constant-
voltage power source
for a small diameter
electrode 5/16" (7,9
mm). In padwashing,
this is caused by hold-
ing the electrode at too
small a push angle.
1. Use an electrode-to-work
angle of 15° to 70°. A
smaller angle increases
the arcing area,reducing
the current density; this
reduction in arc-current
density requires a great
decrease in arc length, to
the point of short circuit.
Keep a proper arc gap.
Irregular groove: too
deep, then too shallow.
1. The operator was
unsteady.
1. The operator should
assume a comfortable
position while gouging.
Slag adhering to the
edges of the groove.
1. Slag ejection was
inadequate. To resolve,
keep a proper air
pressure and flow rate
(cfm). Air pressure be-
tween 80 and 100 psi
(550-690 kPa) may not
effectively eject all of
the slag if the volume
is insufficient.
1. To deliver adequate
volume, the air hose
feeding the concentric
cable assembly needs
a minimum hose ID of
3/8" (9.5 mm) for manual
torches. For automatic
torches, the minimum
hose ID should be 1/2"
(12.7 mm). Direct the air
jet parallel to the gouge
area. Do not favor one
side unless operator
wants to minimize slag
from adhering to one
side of the cut.