Method for sterilising the blowing network of a machine for forming thermoplastic containers

A method for sterilizing a forming machine for forming containers from preforms made of thermoplastic material, the forming machine comprising a blowing network that comprises ducts which connect a controlled source of compressed blowing gas to at least one blowing nozzle for forming the containers by blowing, the forming machine comprising a device for sterilizing the blowing network comprising:

• a controlled source of a pressurized hot drying gas, distinct from the controlled source of blowing gas, which is connected to the blowing network at a supply junction;
• a controlled source of sterilizing vapor comprising a vaporized oxidizing agent;
• and
• a chamber for mixing the sterilizing vapor with the drying gas to form a sterilizing gaseous mixture comprising vaporized oxidizing agent and water vapor;
• the method comprising:
• a step of heating of the ducts of the blowing network by injection only of the pressurized hot drying gas, during which the drying gas heats up internal walls of the ducts of the blowing network;
• and
• a second step of injection of the sterilizing gaseous mixture into the blowing network,
• wherein the second step comprises a step of measurement of a treatment temperature via a probe arranged at a coldest point of the blowing network exposed to the sterilizing gaseous mixture and in that the second step of injection of the sterilizing gaseous mixture is initiated when the coldest point reaches a treatment temperature that is higher than a condensation temperature of the water vapor and of the vaporized sterilizing agent at said coldest point, the treatment temperature being lower than the temperature of the hot drying gas taken at the supply junction.