Abstract: A plasma arc torch is disclosed and includes an electrode defining a discharge end and a longitudinal axis. A nozzle base, formed of metallic material, is positioned adjacent the discharge end of the electrode. The nozzle base has an outer, annular configured mounting surface and a frusto-conical surface positioned adjacent the mounting surface and tapering toward the longitudinal axis in a direction away from the electrode. A lower nozzle member, formed of metallic material, is secured onto the nozzle base mounting surface on the side opposite the electrode, and includes an interior surface spaced from the outer frusto-conical surface of the nozzle base to form a water passage. A ceramic insulator is secured onto the outer surface of the lower nozzle member and extends substantially along that surface for preventing double arcing and insulating the lower nozzle member from heat and plasma generated during torch operation. In a one embodiment the ceramic insulator is secured by means of glue.

Abstract: A process for starting a plasma arc torch is disclosed which minimizes the oxidation of the electrode to thereby extend the life of the electrode. A flow of non-oxidizing gas is first generated between the discharge end of the torch electrode and the nozzle assembly of the torch. A pilot arc then is created between the discharge end of the electrode and the nozzle assembly. The pilot arc is transferred and the flow of non-oxidizing gas is terminated. A flow of oxidizing gas then is generated for plasma formation.