Tweco XTTM-300 - Manual (Page 23)

Manual 0-2912 3-11 INSTALLATION
3.06 Oxygen Plasma Pre-Charge Unit Installation Checks
ALWAYS verify proper function of the plasma pre-charge unit. Follow the steps below to verify the unit is installed
properly.
The pre-charge unit is used to increase the line pressure of the plasma gas (Oxygen) at the start of a cut cycle. The
pre-charge unit is activated only during pre-flow when the gas selection switch is set to cut with Oxygen. This added
pressure provides improved consumable life during piercing. When cutting with any other plasma gas, the pre-charge
unit is not activated.
To verify that the Oxygen Plasma Pre-Charge Unit is installed properly, check it as follows:
1. Be sure that O2 is being supplied to the pre-charge unit and to the gas box.
2. Be sure the gas outlet of the plasma pre-charge box is teed into the plasma lead.
3. Check the switch on the bottom of the pre-charge box to see if it is in the proper position (switch is changed
according to the type of gas box used.
4. Set the gas selection switch on the gas box to “O2/N2” cutting.
5. Turn on “Test Cut Flow” and observe the plasma outlet pressure of the gas box. This pressure will vary with
the consumables in the torch, but should generally be less than 60 psi. This is called the plasma cold flow
pressure.
6. Now turn the switch to “Test Pre-Flow”, and observe the outlet pressure of the plasma gas. It should climb to
120 PSI and the Green Light should be illuminated. This indicates that the plasma line (Oxygen) is correctly
being “pre-charged” to 120 PSI during pre-flow.
7. Now turn the switch back to “Test Cut-Flow”, and observe the outlet pressure of the plasma gas. It should drop
down to the plasma cold flow pressure.
Now verify that the plasma pre-charge unit is not energizing under the following conditions:
1. Set the Plasma Gas Selection switch off of Oxygen cutting (to H35 or Aux).
2. Turn on “Test Cut Flow” and observe the plasma cold flow pressure.
3. Now turn the switch to “Test Pre-Flow”, and observe the outlet pressure of the plasma gas. It should remain at
the plasma cold flow pressure and the Green light should not be illuminated. This indicates that the plasma
pre-charge unit is not activating.