Abstract: An apparatus and process is provided for controlling the selection and supply pressure of gases used in a plasma arc torch. A plurality of pressurized feed gases are selectively routed by solenoid gas valves to one or more motorized pressure regulators. A separate regulator controls the pressurized output of a selected pre-flow gas, plasma gas, shield gas, and post flow gas. A microprocessor establishes recommended pressures for each type of gas and prevents operating pressures from being used which may damage a plasma arc torch.

Abstract: A process for operating a plasma arc torch on shut down includes decreasing current to the electrode from its initial operational value Io to a lesser intermediate value Im in a ramping function between times t1 and t2. Gas pressure within the plasma gas chamber is controlled between times t1 and t2 so that the gas pressure decreases from its operational value Po to a lesser intermediate value Pm substantially concurrently with the decreasing of current between times t1 and t2 and at a controlled rate such that plasma gas flow rate through the nozzle is maintained at least about its operational level Fo or greater between times t1 and t2. At time t2, current is shut off to the electrode.

Abstract: A process for operating a plasma torch on shut down to substantially increase electrode element life involves shutting down the plasma torch according to a first shut down mode for a first predetermined number of pierces attributed to the electrode element. The first shut down mode is controlled such that plasma gas flow through the swirl ring and nozzle decrease to zero substantially immediately upon termination of arc current to the electrode. The shut down method is switched to a second shut down mode for an additional second predetermined number of pierces. In the second shut down mode, the plasma gas flow through the swirl ring and nozzle are maintained after termination of the arc current to the electrode. The shut down mode may be switched back again to the first mode after the second predetermined number of pierces.