A life-time monitoring system is developed to predict the life-time of engines used in a gas pumping station. Four different models are presented to calculate the gas temperature at the inlet of the turbine's rotor, all the models are based on well known thermodynamic process taking place in the engine. Coefficients that include the not measured engine parameters are calculated by regression. The engine working cycle was simulated to generate data for model development and verification. Additional engine working cycle simulations were made taking into account three different defects for additional verification of the models. The model that describes the best the behavior of the gas temperature has been separated. Key words: gas turbine engine diagnostics, gas temperature, prediction.
