FIELD: chemistry.SUBSTANCE: in the invention, a device and methods for processing an oil refinery device or oil refinery device equipment during operation of the said oil refinery device are proposed, wherein in particular the method includes support during the processing period, the oil refinery device in the operation mode common to the plant itself, which includes supplying fresh feedstock to the oil refinery device; while maintaining the oil refinery device in the operation mode, one or both of the actions selected from a) and b) are performed; a) introducing into the oil refinery device, during the processing period, a processing hydrocarbon-based fluid; b) changing the set feed rate used at the beginning of the processing of the oil refinery device or the oil refinery device equipment. The set feed rate is changed ranging from the maximum operating speed for the oil refinery device, including the design speed for the oil refinery device, to the minimum operating speed, which is set at the level correspo
