Abstract: Method and apparatus for cooling down a cryogenic heat exchanger, employing a programmable controller that receives input signals representing sensor signals of one or more controlled variables in a selected process, and produces control signals to control one or more manipulated variables in the selected process. The programmable controller can execute a computer program that comprises a network of at least three modules. The modules in the network are interconnected such a trigger signal received by a second and a third module of the at least three modules corresponds to a communication signal that is generated when the first module of the at least three modules has reached a pre-determined target for that module.