Plasma torch initiated by short-circuit

Plasma torch comprising:

• two tubular coaxial axially spaced electrodes, each electrode being disposed in a support and at least one of said electrodes being axially movable between one torch-operating position in which said movable electrode is in contact with the other electrode, thus establishing an electric short circuit so as to generate an electric arc between said two electrodes upon rupture of the electric short circuit when said movable electrode is brought back to its operating position;
• means to inject a plasma gas between the two electrodes;
• cooling circuits in said supports for supplying a cooling fluid to exterior of said electrodes, the cooling circuit associated with said axially movable electrode having an effective length in contact with said movable electrode which varies with the position of said movable electrode;
• and
• sealing means for sealing the cooling circuit associated with said axially movable electrode regardless of the position of said axially mobile electrode.