Fouling in crude distillation unit preheat train in petroleum refineries is a complex phenomenon. Besides, fouling of equipment by crude oil undergoes different mechanisms at different stages of preheating. Hence, understanding the fouling mechanisms is essential in formulating appropriate fouling mitigation strategies. In this respect, the use of the concept of threshold fouling conditions is one of the approaches for mitigating fouling through operating conditions. Indeed, during this study, a monitoring of the temporal fouling resistance evolution of the E102 exchanger battery of the Algerian refinery was carried out. However, this resistance was calculated based on the classical method proposed by Kern. Given that the monitoring of pressure drops is a widely used method in refineries so as to detect of fouling in the tubes of heat exchangers, it decided to study its evolution over time. Nonetheless, this study has effectively revealed that the heat exchanger battery had a clogging problem since the pressure drops increased over time. In addition, a considerable discrepancy was noted between the values read on the manometers and those calculated from a theoretical expression. In virtue of which, these deviations could be the consequence of measurement uncertainties or the instability of the operating conditions, and also to the fact of considering a constant internal diameter of the tubes.