This study aimed to evaluate and create a mathematical model for a priming system of a centrifugal pump, used to transport oil from a storage tank to the production line. Bettini (2007) proposes an equation for validation of a priming tank using water in laboratory tests. The present work is a similar system, but using oil, where the common obstructions of a foot valve, located at the old alignment of pump suction, led to the replacement of that valve by a priming tank system, located upstream the pump. A mathematical model based on the mechanical energy equation and Boyle's law to model the priming tank was created. The results obtained with the model have been validated by comparing with the real system operation, showing excellent agreement. The useful volume ranges of the priming tank, as well as its range of variation during system operation, were very close to those calculated. The efficiency of the system over time was also proven, considering one year after the modification maintenance interventions were not necessary in the system versus the five maintenances required in the year prior to the modification. Keywords: Centrifugal pump, priming tank, Boyle's Law.