Face to the development and competition to competitiveness, which drives the search for quality and above ail; cost reduction, maintenance has become one of the strategic functions in the company. One of the solutions incorporated in management systems is Conditional maintenance that has proved successful; Reduce downtime, optimize manufacturing, ensure safety and profitability of production. For this type of maintenance to be effective, precise and reliable measurements are required. Experience has shown that vibration analysis is the most widely used technique for reliable monitoring and diagnosis. The objective of this work is the study carried out at the Elma Labiod cement plant, which has adopted continuous monitoring in the hope of an optimal approach to conditional maintenance. We use the analysis of global velocity and acceleration levels, spectral analysis and envelope analysis to detect defects and anticipate degradations that can affect a mechanism and determine the probable causes of these malfunctions. In this context, the actual measurements were analyzed by vibratory indicator leading to detection of the weak points causing a malfunction on the machine (rolling bearings), therefor an optimization of the maintenance is realized by monitoring the degradation through on-line control system. The analysis of these vibrations let the possibility to detect and locale the defective components once the fixed corresponding threshold limit of vibration level has been reached.