Lincoln Electric RED-D-ARC PM 255, Operator'S Manual, Page: 13 / 38

GUN AND CABLE INSTALLATION
The Magnum 250L gun and cable provided with the
PM 255 is factory installed with a liner for .035-.045"
(0.9-1.2 mm) electrode and an .035" (0.9 mm) contact
tip. Install the .045 tip (also provided) if this wire size
is being used.
Turn the welder power switch off before installing
gun and cable.
1. Lay the cable out straight.
2. Unscrew knurled screw on the drive unit front end
(inside wire feed compartment) until tip of screw no
longer protrudes into gun opening as seen from
front of machine.
3. Insert the male end of gun cable into the female
casting through opening in front panel. Make sure
connector is fully inserted and tighten knurled
screw.
4. Connect the gun trigger connector from the gun
and cable to the mating receptacle inside the com-
partment located above the gun connection made
in item 3 above. Make sure that the keyways are
aligned, insert and tighten retaining ring.
SHIELDING GAS
(For Gas Metal Arc Welding Processes)
Customer must provide cylinder of appropriate type
shielding gas for the process being used.
A gas flow regulator, for CO
2
or Argon blend gas, and
an inlet gas hose are factory provided with the PM
255.
Install shielding gas supply as follows:
1. Set gas cylinder on rear platform of PM 255. Hook
chain in place to secure cylinder to rear of welder.
WARNING
A-5
A-5
INSTALLATION
WARNING
2. Remove the cylinder cap. Inspect the cylinder
valves and regulator for damaged threads, dirt,
dust, oil or grease. Remove dust and dirt with a
clean cloth.
DO NOT ATTACH THE REGULATOR IF OIL,
GREASE OR DAMAGE IS PRESENT!
Inform your
gas supplier of this condition. Oil or grease in the
presence of high pressure oxygen is explosive.
3. Stand to one side away from the outlet and open
the cylinder valve for an instant. This blows away
any dust or dirt which may have accumulated in the
valve outlet.
Be sure to keep your face away from the valve
outlet when “cracking” the valve.
4. Attach the flow regulator to the cylinder valve and
tighten the union nut(s) securely with a wrench.
NOTE: If connecting to 100% CO
2
cylinder, insert reg-
ulator adapter between regulator and cylinder
valve. If adapter is equipped with a plastic
washer, be sure it is seated for connection to
the CO
2
cylinder.
5. Attach one end of the inlet gas hose to the outlet
fitting of the flow regulator, the other end to the PM
255 rear fitting, and tighten the union nuts securely
with a wrench.
6. Before opening the cylinder valve, turn the regula-
tor adjusting knob counterclockwise until the
adjusting spring pressure is released.
7. Standing to one side, open the cylinder valve slow-
ly a fraction of a turn. When the cylinder pressure
gauge pointer stops moving, open the valve fully.
Never stand directly in front of or behind the flow
regulator when opening the cylinder valve. Always
stand to one side.
8. The flow regulator is adjustable. Adjust it to the flow
rate recommended for the procedure and process
being used before making the weld.
CYLINDER may explode if
damaged.
• Gas under pressure is explosive. Always
keep gas cylinders in an upright position
and always keep chained to undercarriage
or stationary support. See American
National Standard Z-49.1, “Safety in
Welding and Cutting” published by the
American Welding Society.
WARNING
PM 255
WARNING