The present work aims to describe and analyse the influence of the reliability and maintainability of the pump systems on the overall plant availability. The study was developed into an aliphatic solvent plant situated in Colombia and owned by the state company Ecopetrol S.A. This plant is composed of six pump systems, each one of them with parallel redundancy, working in series. The first step during the process was the identification of the dominant failure modes for these pump systems according to historical maintenance information collected during the last nine years and recorded in the CMMS of the company. For these dominant failure modes a Weibull analysis was carried out in order to determine the main parameters of the failure probability distribution function and, in this way, to build a mathematical model useful for predictions of future failures. Additionally, a maintainability model was developed based on the current repair process capability of the work shop employed by the company. By employing reliability block diagrams the reliability dependencies between components, items, units, and systems were taking into account. A general model for the whole plant unit was built and several simulations were performed using Monte Carlo techniques. The simulation results were helpful to identify the more sensitive elements for the overall plant availability and suggest some maintenance and operational actions in order to reduce plant downtime and maintenance costs.