The increasing amount of liquid, especially water, in the product stream of offshore gas wells, requires improvement of current separation methods. Nowadays, separation methods are mainly based on gravitational settling of the dispersed phases. In these separators low gas velocities are required to achieve a sufficient separating efficiency. As a result these devices are voluminous, heavy, and expensive. As platforms are restricted to space and weight and the liquid amount is increasing, compact and efficient phase separation equipment is required to keep the exploitation of the wells profitable. A device which fulfils these requirements is the naturally driven Rotational Particle Separator (RPS). In this study the operating characteristics of such a separator was measured. For this purpose a full-scale prototype was built, which is capable to handle the volume flow of one typical wellhead under high pressure (80 bar) and which separates droplets down to 2 micron. In order to validate the operating characteristics of the prototype both hydrodynamic and separation performance measurements were performed. Overall, the performance of the prototype agrees well with expectations.