The aim of this work is to create a model for automatic valves installed on piston compressors. Although their working principle is relatively simple, valves are the component within the compressor assembly with the highest risk of failure and/or maintenance. The aim of this thesis is to provide a comprehensive model of valve performance and how its characteristics influence compressor performance, since valves mark the various thermodynamic phases (suction, compression, discharge, expansion) of the piston compressor. The model was realised on the Simscape software, which is characterised by a graphic interface that can be quickly modified according to the type of valve being studied.