Tweco PCM-120 Machine Torch - Manual (Page 19)

Manual 0-2698 3-3 INSTALLATION PROCEDURES
2. Nitrogen (N2) Plasma
• Provides cut quality similar to air on non-ferrous
materials such as stainless steel and aluminum.
• Can be used in place of air plasma with air second-
ary or carbon dioxide (CO
2
).
• Provides much better parts life than air.
• A good clean welding grade nitrogen should be
used.
3. Argon/Hydrogen (ArH
2
) Plasma
• Recommended for use on 3/4 inch (19 mm) and
thicker stainless steel. Recommended for 1/2 inch
(12 mm) and thicker non-ferrous materials. Ar/H
2
is not normally used for thinner non-ferrous mate-
rials because less expensive gases can achieve simi-
lar cut quality.
• Poor cut quality on ferrous materials.
• Provides faster cutting speeds and high cut quality
on thicker materials to offset the higher cost.
• A 65% argon/35% hydrogen mixture should be
used.
B. Secondary Gases
NOTE
Refer to Section 2.03, Specifications & Design Fea-
tures, for proper gas pressure and flow rate.
1. Compressed Air Secondary
• Air secondary is normally used when operating
with air plasma and occasionally with nitrogen
plasma.
• Improves cut quality on some ferrous materials.
• Inexpensive - reduces operating costs.
2. Carbon Dioxide (CO
2
) Secondary
• CO
2
secondary is used with nitrogen or Ar/H
2
plasma.
• Provides good cooling and maximizes torch parts
life.
• Provides good cut quality on ferrous or non-ferrous
material.
• May reduce smoke when used with Ar/H
2
plasma.
NOTE
When CO
2
is used as the secondary gas, twenty
(50 lb) cylinders must be manifolded together or a
bulk CO
2
system used to get the required flow rate
of 340 scfh. Shop compressed air is a good alterna-
tive if providing the required CO
2
flow rate is not
feasible.
3. Nitrogen (N2) Secondary
• Nitrogen secondary is used with Ar/H
2
plasma.
• Provides smooth finishes on non-ferrous materials.
• May be used with nitrogen plasma in order to oper-
ate from one compressed gas cylinder - but torch
parts life may be shorter than with CO
2
secondary.
• May reduce smoke when used with Ar/H
2
plasma.
3.08 Gas Connections
A. Connecting to Power Supply
Connect the gases to the power supply as described
in the power supply operating manual supplied with
the power supply.
CAUTION
Air supply must be free of oil, moisture, and other
contaminants. Excessive oil and moisture may
cause double-arcing, rapid tip wear, or even com-
plete torch failure. Contaminants may cause poor
cutting performance and rapid electrode wear.
B. Checking Air Quality
To test the quality of air, place a welding filter lens in
front of the torch and turn on the gas for 2-3 minutes.
Any oil or moisture in the air will be visible on the
lens. Do not initiate an arc!
C. Filtering
An inline pneumatic dryer/evaporator type air fil-
ter, capable of filtering to at least 5 microns, is required
when using air from a compressor. This type filter
will insure that moisture, oil, dirt, chips, rust particles,
and other contminants from the supply hose do not
enter the torch. For highly automated applications,
a refrigerated drier may be used.
NOTE
Do not use an air line filter with high pressure gas
cylinders.