Metallic heating belts, with a power of 1000 to 2500W, are light, sealed and robust and are placed on the smooth, non-grooved parts of the drums. They have a large surface area which prevents any product carbonisation (load ≤ 1W/cm2). Installation is easy when the drum is positioned vertically. They are clamped with a device that can be adjusted to the diameter of the drum. Metallic heating belts can be equipped with a thermostat, which can be set to 0/200°C.