Abstract This work proposes a methodology and workflow to assist in the analysis of an existing heat exchanger network design when the operating conditions vary. Its purpose is to facilitate the involvement of the engineer in the daily operation and maintenance of the network. In order to incorporate this new methodology into the operations workflow, the concept of a heat exchanger network unit operation is introduced. The main characteristic of this new unit operation is its complete knowledge of the different complexities of the heat exchanger network model. Moreover, the heat exchanger unit operation is capable of managing the network degrees of freedom to consider different problem formulations. Additional features of this unit operation include the automatic analysis of output variables when the operating conditions change and the analysis of the trends follow by these variables during a given time period. An example showing the application of these features to the preheat train of a crude distillation column is presented.