Abstract: The invention relates to an installation for surfacing by plasma-arc welding including in particular a plasma torch and a control and power supply device for the formation of a transferred arc between the electrode of the torch and the workpiece to be surfaced and of a non-transferred arc between the said electrode and the nozzle of the torch, the control and power supply device comprising a single d.c. source one terminal of which is connected to the electrode of the torch and the other terminal of which is connected, on the one hand, to the workpiece to be surfaced and on the other hand to the nozzle of the torch via a resistance. The plasma torch has at least two cooling systems supplied by a distribution device which is controlled as a function of the cooling water temperature and/or the electrical power consumption of the torch.