Abstract The paper presents the revitalization of a conveyor belt furnace for annealing metal, which included the design and implementation of a control system based on a programmable logic controller. The goal of the revitalization of the furnace is its modernization through the digital transformation of technological process variables as a new form of data availability in the context of Industry 4.0. The application of a modern control system ensures optimal control of the technological process and thus significantly extends the useful life of the machine.