Ignoramus28229 said:
Oh, and I must say that I am sorry about that.
i
PLASMA GAS SELECTION CHART
Gas Recommended For Advantages Disadvantages
Air
* Carbon Steel
* Stainless Steel
* Clean Fast Cut on C.S.
* Affordable
* Convenient
* Short Electrode Life
* Nitriding on Cut Surface
* Oxidation on S.S./ AL
Nitrogen
* Stainless Steel
* Aluminum
* Carbon Steel
* Excellent Cut on S.S./AL
* Excellent Electrode Life
* Affordable
* Nitriding on Cut Surface
Argon/Hydrogen
* Stainless Steel
* Aluminum
* Excellent Cut Quality and Speed on Thicker Material (> 1/2 in.)
* Less Smoke/Fumes
* Expensive
* Not for C.S.
Oxygen
* Carbon Steel
* Clean Cut
* No Surface Nitriding
* Fast on C.S.
* Short Electrode Life
* Oxidation on S.S./AL
There are various types of torch cooling systems. Low-amp torches (150
amps or less) can be cooled by channeling a secondary gas through the
torch. Higher-powered torches use water and require a cooling system
with a reservoir, pump and heat exchanger. It's very important to use
de-ionized water for cooling, since the coolant (water) may contact
both negative and positive potentials inside the torch.
Theory: Sequence of Operation
When an operator gives a start cut signal, the system energizes and a
prepurge of gas lasting a few seconds will flow through the torch. This
ensures that proper gas flow is available before an arc is struck. The
initial arc, which ionizes a portion of the plasma gas, is generated by
a high-voltage spark between the nozzle and the electrode. Current
flows through the ionized gas (plasma) to the nozzle.
The gas flow pushes the arc out of the orifice where it reattaches to
the outside of the nozzle, forming a J-shaped pilot arc. In some
systems, the pilot arc is controlled by a timing circuit. Other systems
have an arc transfer sensor to detect the current change (when the
cutting arc takes over) and switch off the pilot circuit. Some systems
also have an automatic restart pilot, which is useful when cutting
grating or expanded metal. With automatic restart, the torch can cycle
back and forth between "pilot" and "cut" modes as long as the start
signal is present.
The pilot arc forms a "pathway" to the metal. If the torch is close
enough to the workpiece, then the arc will transfer from the electrode,
through the nozzle, to the metal. Once this transferred arc is
established, it will continue as long as there is metal to transfer to.
The constricted plasma jet concentrates the energy of the arc on a
small area of the workpiece, heating it to melting temperature and
blasting the molten material out of the cut.
When a stop signal is given (or the start-cut signal is shut off), the
cutting arc stops and the gas continues to flow for a few seconds to
cool the torch and torch parts. It also shields the electrode,
preventing outside air from reacting with the electrode element as it
cools.
hay i hope this helps out some
)