An experimental investigation was undertaken in order to provide information on the roles of centrifugal and natural separations, with the objective of providing a coherent basis for predicting and improving moisture separator performance. In this experiment air-water tests at atmospheric temperature and pressure were performed because it is relatively inexpensive and readily obtainable. This experimental investigation aimed first at making a possible visualization of the separation process, and second at examining qualitatively the influence of certain mechanical features of a primary swirl vane separator. Also the work aimed at trying to know how much separation is occurred due to natural separation. The data from the experiments were reduced, examined and correlated for the purpose of advanced steam separator design. And then, the results of data reduction, the correlation and the modeling were analyzed in an effort to suggest means for prediction and improvement of separator performance.