User Responsibility; Preheat Temperature For Plasma Cutting; Procedure Recommendations; General - Lincoln Electric PRO-CUT 55 Service Manual

B-7
WARNING
ELECTRIC SHOCK can kill.
• Turn off machine at the disconnect
switch on the front of the machine
before tightening, cleaning or replac-
ing consumables.
- Check the conditions of the inside of the nozzle. If
debris has collected, rub the electrode on the
inside bottom of the nozzle to remove any oxide
layer that may have built up. Refer to
"Suggestions for Extra Utility from the Pro-Cut
System."
- Check the condition of the electrode. If the end has
a crater-like appearance, replace it along with the
nozzle. The maximum wear depth of the electrode
is approximately .062 in. (1.6mm). A green and
erratic arc will indicate definite electrode failure.
The electrode should be replaced immediately.
• Replace the nozzle when the orifice exit is eroded
away or oval shaped.
• After the problem is found, or if there is nothing
apparently wrong, reset the machine by pressing
the "Reset" button. (It is possible for electrical noise
to trip the safety circuit on rare occasions. This
should not be a regular occurrence.)
• If the machine does not reset or continues to trip,
consult the Troubleshooting Section.
• Use the proper cutting or gouging procedures
referred to in "Procedure Recommendations"
below.

USER RESPONSIBILITY

Because design, fabrication, erection and cutting vari-
ables affect results, the serviceability of a product or
structure is the responsibility of the user. Variation
such as plate chemistry, plate surface condition (oil,
scale), plate thickness, preheat, quench, gas type, gas
flow rate and equipment may produce results different
from those expected. Some adjustments to proce-
dures may be necessary to compensate for unique
individual conditions. Test all procedures duplicating
actual field conditions.
OPERATION
PREHEAT TEMPERATURE FOR
PLASMA CUTTING
Preheat temperature control is not necessary in most
applications when plasma arc cutting or gouging.
Preheat temperature control may be necessary on
high carbon alloy steels and heat treated aluminum for
crack resistance and hardness control. Job condi-
tions, prevailing codes, alloy level, and other consider-
ations may also require preheat temperature control.
The recommended minimum preheat temperature for
plate thickness up to 1/2 in. (12.7mm) is 70°F (21.1°C).
Higher temperatures may be used as required by the
job conditions and/or prevailing codes. If cracking or
excessive hardness occurs on the cut face, higher pre-
heat temperature may be required.

PROCEDURE RECOMMENDATIONS

When properly used, plasma arc cutting or gouging is
a very economical process. Improper use will result in
a very high operating cost.
GENERAL - IN ALL CASES
• Follow safety precautions as printed throughout this
manual and on the machine.

THIN GAUGE SHEET METAL

Torch Standoff
DRAG thru 1/16"
Standoff
Output set below mid-range.
• The nozzle may be dragged on the metal surface,
touching it lightly to the surface after piercing a hole.
Current control should be set below the mid-range.
• Do not allow cable or body to contact hot surface.
B-7
Machine Output Setting
Output Setting
Output Setting
Min. thru Mid-Range
Min. thru Mid. Range